The Piping Guide by David Sherwood - 1991
The Piping Guide by David Sherwood - 1991
The Piping Guide by David Sherwood - 1991
All rights reserved. No part of this book may be reproduced or transmitted by any means whatsoever
Printed in the United States of America
David R. Sherwood
ISBN 0914082191
Part I
Contents
Chapter
PIPING:
ORGANIZATION OF WORK:
DRAFTING:
PROCESS AND PIPING DRAWINGS including Drawing Symbols, Showing Dimensions, Showing Instrumentation, and Bills
of Material
Including Arrangement, Supporting, Insulation, Heating, Venting and Draining of Piping, Vessels and Equipment
for Piping Systems, Pipe, Pipe Supports, Flanges, Gaskets, Fittings, Valves, Traps, Pumps, Vessels, Heat Exchangers,
Symbols and Screw threads
ABBREVIATIONS:
for Piping Drawings and Industrial Chemicals
INDEX/GLOSSARY/ACKNOWLEDGMENTS
2.1
Pipe in the various sizes is made in several wall thicknesses for each size,
which have been established by three different sources:-
2.1.1
(1)
(2)
The principal uses for tube are in heat exchangers, instrument lines, and
small interconnections on equipment such as compressors, boilers, and
refrigerators.
(3)
The American Petroleum Institute, through its standard 5L, for 'Line
pipe'. Dimensions in this standard have no references for individual
sizes and wall thicknesses
ANSl standard B36.10M establishes wall thicknesses for pipe ranging from 118
to 80-inch nominal diameter('nomina1 pipe size'). Pipe sizes normally stocked
include: 112, 314, 1, 1%, lh, 2, 2%, 3, 3%, 4, 5, 6, 8, 10, 12, 14, 16, 18,
20 and 24. Sizes I%, 2K, 3'/2, and 5 inch are seldom used (unusual sizes are
sometimes required for connecting to equipment, but piping is normally
run in the next larger stock size after connection has been made). 118, 114,
318 and 112-inch pipe is usually restricted to instrument lines or to service
and other lines which have to mate with equipment. 112-inch pipe is
extensively used for steam tracing and for auxiliary piping at pumps, etc.
Pipe dimensions from the second and third sources are incorporated in
American National Standard B36.10M. Tables P.1 list dimensions for
welded and seamless steel pipe in this standard, and give derived data.
IRON PIPE SIZES were initially established for wrought-iron pipe, with wall
thicknesses designated by the terms 'standard (weight)', 'extra-strong', and
'double-extra-strong'. Before the schedule number scheme for steel pipe was
first published by the American Standards Association in 1935, the iron pipe
sizes were modified for steel pipe by slightly decreasing the wall thicknesses
(leaving the outside diameters constant) so that the weights per foot (Iblft)
equalled the iron pipe weights.
Wrought-iron pipe (no longer made) has been completely supplanted by steel
pipe, but schedule numbers, intended to supplant iron pipe designations did
not. Users continued to specify pipe in iron pipe terms, and as the mills
responded, these terms are included in ANSl standard B36.10M for steel pipe.
Schedule numbers were introduced to establish pipe wall thicknesses by
formula, but as wall thicknesses in common use continued t o depart from
those proposed by the scheme, schedule numbers now identify wall thick.
nesses of pipe in the different nominal sizes as ANSl B36.10M states "as a
convenient designation system for use in ordering".
2.1.3
The size of all pipe is identified by the nominal pipe size, abbreviated 'NPS',
which is seldom equal to the true bore (internal diameter) of the pipe-the
difference in some instances is large. NPS 14 and larger pipe has outside
diameter equal to the nominal pipe size.
131
2.1.4
made from plate. Seamless pipe is made using dies. Common finishes are
'black' ('plain' or 'mill' finish) and galvanized.
PLASTICS Pipe made from plastics may be used to convey actively corrosive
fluids, and is especially useful for handling corrosive or hazardous gases and
dilute mineral acids. Plastics are employed i n three ways: as all-plastic pipe,
as 'filled' plastic materials (glass-fiber-reinforced, carbon.filled, etc.) and as
lining or coating materials. Plastic pipe is made from polypropylene, polyethylene (PE), polybutylene (PB), polyvinyl chloride (PVC), acrylonitrile.
butadiene-styrene (ABS), cellulose acetate-butyrate (CAB), polyolefins, and
polyesters. Pipe made from polyester and epoxy resins is frequently glassfiber-reinforced ('FRP') and commercial products of this type have good
resistance to wear and chemical attack.
Correctly selected steel pipe offers the strength and durability required for
the application, and the ductility and machinability required to join it and
form i t into piping ('spools' .. see 5.2.9). The selected pipe must withstand
the conditions of use, especially pressure, temperature and corrosion conditions. These requirements are met by selecting pipe made t o an appropriate
standard; in almost all instances an ASTM or API standard (see 2.1.3 and
table 7.5).
W. CERhlANY
The most.used steel pipe for process lines, and for welding, bending, and
coiling, is made to ASTM A-53 or ASTM A.106, principally in wall thicknesses
defined b y schedules 40, 80, and manufacturers' weights, STD and XS. Both
ASTM A-53 and ASTM A.106 pipe is fabricated seamless or seamed, by
electrical resistance welding, in Grades A and El. Grades 8 have the higher
tensile strength. Three grades of A-106 are available-Grades A, B, and C, in
order of increasing tensile strength.
The most widely stocked pipe is to ASTM A.120 which covers welded and
seamless pipe for normal use in steam, water, and gas (including air) service.
ASTM A-120 is not intended for bending, coiling or high temperature service.
I t is not specified for hydrocarbon process lines.
g
<
I n the oil and natural gas industries, steel pipe used t o convey oil and gas is
manufactured to the American Petroleum Institute'sstandard API 5L, which
applies tighter control of composition and more testing than ASTM-120.
Steel specifications in other countries may correspond with USA specifications. Some corresponding european standards for carbon steels and
stainless steels are listed in table 2.1.
ASTM A53
BS 3601
DIN 1628
Grado A SMLS
Gi.xii? B SMLS
51 35
Sr 45
ASTM A53
BS 3601
DIN 1626
G i r d r A E RIV
Grade '3 E R W
ERN22
ERW 27
ASTM A53
BS 3601
DIN 1626
FBW
BW 2 2
ASTM A106
BS 3602
DIN 17175.
Grade A
Grade B
Grade C
HFS23
HFS27
HFS 3 5
5 1 35.8
St 45-8
ASTM A134
BS 3601
DIN 1626
EFW
B l r l l 2 EFW
515 1234-05
SIS 1 4 3 5 0 5
BS 3601
DIN 1626
Grade A
Grade B
ERW22
ERW27
ASTM A139
BS 3601
DIN 1626
Grdrlc A
Glddl' B
EFW 22
EFW27
B I ~ I I2 St 37
B i a l l 2 51 42
ASTM A155
2
BS 3602
C50
C 55
KC 5 5
KC Mi
KC 6 5
KC 7 0
EFW 28
EFWZBS
BS 3601
DIN 1629
Grade A SMLS
Grade B SMLS
H F S 22 & CDS 2 2
H F S 27 & C D 5 27
51 3 5
51 45
API 5L
BS 3601
t f l W 22
DIN 1625
tRW27 1
SIS 1 2 3 3 0 5
SIS 1434-05
U1~11J SI 34.2 t RW
81d11 4 SI 37-2 E RW
API 5 1
6s 3601
Doubl~.welded
DIN 1626
Grddc A F F W
Grade B t F W
EFW 22
EFW27 I
Bid11 '151 34 2 F Y I
Bldn 4 SI 37-2 F W
API 5L
BS 3601
DIN 1626
BW 2 2
'Spec~ly"Si.krllrd
SIS 1 2 3 3 0 6
SIS 1434.06
SI 34.2
SI 37-2
5142 2
Sl 42-2 '
Sl 4 2 2 '
SI 5 2 - 3
51 52-3
API 5L
FBW
ASTM A135
Gr,#,lc A L R W
Grruc B EHW
I R O N pipe is made from cast-iron and ductile-iron. The principal uses are
SIS 1233-05
SIS 1434.05
SiS 1 2 3 1 0 6
S S 1434-06 t
-1
3c
35
5
!
ASTM A312
BS 3605
TP 3 0 4
TP X i l H
TP 3 0 4 L
TP310
TP 3 1 6
Grade
Grade
Grade
Grade
Grade
;;
Graae 8 5 5
Grade 8 4 5 L
G ~ a d e8 4 6
Glade 8 2 2 TI
TP31EH
L;;;
TP321
TP 3 2 1 H
TP347
TP 3 4 7 H
801
81 1
801 L
805
845
Glads 8 3 2 TI
Grade 6 2 2 N b
Grade 8 3 2 Nb
WSN
Osigntion:
4301
Y 5 CrNq 1 8 9
SIS 2333-02
4306
4841
44011
4436
X 2 CrNt 1 8 9
X 5 C l N t M o 18 10
SIS 2 3 5 2 0 2
SlS236102
SIS 2 3 4 3 0 2
4404
X 2 CINIMO
SIS 2 3 5 3 0 2
4541
X 10CrN1T1 1 8 9
SIS2337.02
4550
X 1 0 CrNtNb I 8 9
515 2338.02
X 15CrN1St 2 5 2 0
18 10
r=li--
1.3
.2.4
L.-J,,-_ _
!:
2.2.2
SOCKET-WELDED JOINTS
Like screwed piping, socket welding is used for lines of smaller sizes, but
has the advantage that absence of leaking is assured: this is avaluable factor
when flammable, toxic, or radioactive fluids are being conveyed-the use of
socket-welded joints is not restricted to such fluids, however.
2.2.3
BOLTED-FLANGE JOINTS
Flanges are expensive and for the most part are used to mate with flanged
vessels, equ ipment, valves, and for process Iines which may requi re periodic
cleaning.
Flanged jointsare made by bolting together two flanges with agasket between
them to provide a seal. Refer to 2.6 for standard forged-steel flanges and
gaskets.
2.2.4
FITTINGS
2.1.5
Chart 2.1 shows the ratings of butt-welding fittings used with pipe of various
schedule numbers and manufacturers' weights, For dimensions of buttwelding fittings and flanges, see tables 0-1 thru 0-6, and tables F-l thru
F-7. 0 rafting symbols are given in charts 5.3 thru 5.5.
Threaded fittings have Pressure Class designations of: 2000,3000 and 6000.
Socket-welding fittings have Pressure Class designations of: 3000, 6000 and
9000. How these Pressure Class designations relate to schedule numbers and
manufacturers' weights for pipe isshown in table 2.2.
2.2
;2
11
Lines NPS 2 and larger are usually butt-welded, this being the most
economic leakproof way of joining larger-diameter piping. Usually such
lines are subcontracted to a piping fabricator for prefabrication in sections
termed 'spools', then transported to the site. Lines NPS 1% and smaller
are usually either screwed or socket-welded. and are normally field-run by
the piping contractor from drawings. Field-run and shop-fabricated piping
are discussed in 5.2.9.
GLASS
2.2.1
TABLE 2.2
The joints used for most carbon-steel and stainless-steel pipe are:
BUTTWELDED
SOCKETWELDED.
SCREWED
BOLTED FLANG E.
SEE 2.3
. SEE 2.4
SEE 2.5
.SEE 2.8.2
(5)
2000
80/XS
3000
160
80/XS
6000
XXS
160
9000
XXS
t-rA-sLE
12.1 & 2.2
Sections 2.1.3 thru 2.2.4 have shown that there is a wide variety of
differently-rated pipe, fittings and materials from which to make a choice.
Charts 2.1 thru 2.3 show how various weights of pipe, fittings and valves
can be combined in a piping system.
ADVANTAGE OF JOINT:
DISADVANTAGE
OF JOINT:
HOW JOINT IS MADE:
Chart 2.1 shows the ratings of pipe, fittings and valves that are commonly
combined or may be used together. I t is a guide only, and not a substitute
for a project specification.
NPS 2
FOR
WEIGHT OF PlPE & FITTINGS NCRMALLY
USED. CHOICE OF OTHER MATERIALS OR
HEAVIER.WEIGHT PIPE & FITTINGS WILL
DEPEND ON PRESSURE.TEMPERATURE &/OR
THE CORROSION ALLOWANCE REOUIRED.
NPS 2 AND LARGER PIPE IS USUALLY OR.
DERED TO ASTM A.53. Grade B. SEE 2 1.4,
UNDER 'STEELS'
NPS
:;FINAL
SIZE:
10
NPS 6
~~~~~E
SCH 40
MFRS'
WEIGHT
STD
NPS 8
end larger
CILCULATT
wrLLT*lcKrrrr
* * O M CODE
SCH 20
or
SCH 30
VALVES
FITTINGS, BENDS, MITERS 81 FLANGES
FOR BUTT-WELDED SYSTEMS
Refer to tables D, F and W-1 for dimensions and weights of fittings and
flanges.
PRESSURE
RATING
CLASS
BACKING RING
line size. Reducing elbows have centerline radius of curvature 1 % times the
nominal size of the pipe to be attached to the larger end.
RETURN changes direction of flow thru 180 degrees, and is used to
construct heating coils, vents on tanks, etc.
BENDS are made from straight pipe. Common bending radii are 3 and 5
times the pipe size (3R and 5R bends, where R = nominal pipe sizenominal diameter, not radius). 3R bends are available from stock. Larger
radius bends can be custom made, preferably by hot bending. Only seamless
or electric.resistance.welded pipe is suitable for bending.
FIGURE 2.1
F L A T TYPE
F I G U R E 2.2
90 L O N G - R A D I U S
ELBOW
90 S H O R T . R A D I U S
ELBOW
FIGURE 2.4
CONCENTRIC
4 5 O ELBOW
(LR)
LONG-RADIUS
RETURN
ECCENTRIC
VENTURI TYPE
3 x NPS
CHAR
REDUCING
ELBOW
SHORT-RADIUS
RETURN
x NPS
2 x NPS
( O f larger plpe)
REDUCER (or INCREASER) joins a larger pipe to a smaller one. The two
available types, concentric and eccentric, are shown. The eccentric reducer
is used when i t is necessary t o keep either the top or the bottom of the line
level-offset equals '/? x (larger ID minus smaller ID).
3-PIECE MITER
FIGURE 2.5
2-PIECE M I T E R
F I G U R E 2.3
REDUCERS
CONCENTRIC
are not
fittings. The use of miters to make changes in direction is practically
restricted to low-pressure lines 10-inch and larger if the pressure drop is
unimportant; for these uses regular elbows would be costlier. A 2-piece,
90-degree miter has four to six times the hydraulic resistance of the corresponding regular long-radius elbow, and should be used with caution. A 3-piece
90-degree miter has about double the resistance to flow of the regular l o n g
radius elbow-refer to table F-10. Constructions for 3-, 4-, and 5-piece miters
are shown in tables M-2.
ECCENTRIC
T H E 2-PIECE M I T E R H A S H I G H
F L O W R E S I S T A N C E (See T A B L E F-10)
2.1
The following five flange types are used for butt-welded lines. The different
flange facings available are discussed in 2.6.
FIGURE 2.6
EXPANDER FLANGE
FIGURE 2.7
FIGURE 2.9
Pz.l
RUN INLET
REOUCINQ ON BRANCH
6"
RUN OUTLET
BRANCH
EXAMPLE
4"
REOTEE6a6a4
L--
6"
BUTT-WELDING TEES
FIGURE 2.12
FIGURE 2.10
B END
pipe run-it is not a fitting. This is the commonest and least expensive method
of welding a full-size or reducing branch for pipe 2-inch and larger. A stub-in
can be reinforced by means set out in 2.1 1.
STUB-IN
FIGURE 2.11
pipe. Closer manifolding is possible than with tees. Flat-based weldolets are
available for connecting to pipe caps and vessel heads.
WELDOLET
FIGURE 2.13
(FIGURE
:i
2.6-2.1 3
BUTT-WELDING CROSS
FIGURE 2.17
BUTT-WELDING LATROLET
FIGURE 2.14
FIGURE 2.15
pipe.
SWEEPOLET makes a 90-degree reducing branch from the main run of pipe.
Primarily developed for high-yield pipe used in oil and gas transmission lines.
Provides good flow pattern, and optimum stress distribution.
SWEEPOLET
FIGURE 2.18
FIGURE 2.16
N o w rarely used, but can be obtained from stock in 90and 45-degree angles, and i n any size and angle, including offset, to special
order. The run is field-cut, using the nipple as template. Needs reinforcement
if it is necessary to bring the strength of the joint up to the full strength
of the pipe.
SHAPED NIPPLE
SHAPED NIPPLE
The next three fittings are usually used for special designs:
FIGURE 2.19
CLOSURES
2.3.3
CHART 2 2
SOCKET.WELDED PIPING
7
'
-
.3.2
L, .4
Chart 2 2 shows the ratrngs of prpe, flttlngs and valves that are commonly
comb~ned,or may be used together The chart IS a gulde only, and not a
subst~tutefor a project specrf~cat~on
(b) F L A T C L O S U R E
(c) F L A T C L O S U R E
CHART
WHERE USED:
WEIGHTS OF PlPE
A N D PRESSURE
CLASSES OF
FITTINGS WHICH
ARE COMPATIBLE
2.2
L
6000
9000
FITTING
BORED
TO
SCH 40
SCH 160
XXS
(1)
(2)
3002
i
i
ADVANTAGES OF JOINT:
FITTING
CLASS
VALVES
CONTROL VALVES
( U S U A L L Y FLANGED)
PRESSURE
(RATING)
CLASS
VALVES OTHER T H A N
CONTROL V A L V E S
600 (ANSI1
800 ( A P l l
ANSI ~ 1 6 . 1 1 r e c o m m e n d s a 1 / 1 6 t h - ~ n c h g a p t o p r e v e n t w e l d f r o m c r a c k l n g u n d e r
t h e r m a l stress
t S o c k e t - e n d e d f l t t l n g s a r e n o w o n l y m a d e I n classes 3 0 0 0 6 0 0 0 a n d 9 0 0 0 ( A N S I 6 1 6 . 1 1 )
1111
Dimensions of fittings and flanges are given in tables D-8 and F-1 thru F-6.
screwed joint designed for use with socket-welded piping systems. See explanation in 2.5.1 of uses given under 'threaded union'. Union should be
screwed tight before the ends are welded, t o minimize warping of the seat.
FIGURE 2.24
SOCKET-WELDING U N I O N
swage, etc.
FULLCOUPLING
FIGURE 2.21
SWAGED NIPPLES
REDUCER
TABLE 2.3
SW ITEM
LARGER to SMALLER
FIGURE 2.23
Bw
FITTING or PIPE
SW ITEM
SW
ITEM
--
SWG 1%
SWG 2
PEE
PSE
SOCKET-ENDED
FITTING, FLANGE,
O R EQUIPMENT
T H R E E FORMS
OF REDUCER
INSERT1
'I
SWAGE
(PEE)
--
PEE
BLE-PSE
BW
PLE
SW = Socket welding
ABRREVIATIONS:
x 1
x 1
Butt welding
Plain large end
FIGURE 2.25
FIGURE 2.26
SOCKET-WELDING
SOCKET-WELDING LATERAL
FIGURE 2.29
FIGURE 2.27
CROSS
SOCKET.WELDING CROSS
1"
FIGURE 2.30
2.4.3
SOCKET-WELDING LATROLET
straight pipe.
SOCKET-WELDING LATROLET
FIGURE 2.34
FIGURE 2.31
The next four fittings are made by Bonney Forge and offer an alternate method
of entering the main pipe run. They have the advantage that the beveled
welding ends are shaped t o the curvature of the run pipe. Reinforcement
for the butt-welded piping or vessel is not required.
NIPOLET
FIGURE 2.35
Flat-based sockolets are available for branch connections on pipe caps and
and vessel heads.
SOCKOLET
FIGURE 2.32
STUB-IN See comments i n 2.3.2 .Not preferred for lines under 2-inch due to
FIGURE 2.33
FIGURE 2.36
2.5
ADVANTAGES:
(1)
(2)
DISADVANTAGES:
(1)" U s e n o t p e r m i t t e d b y A N S I 8 3 1 . 1 - 1 9 8 9 , if
severe erosion, crevice c o r r o s i o n , shock, o r
v i b r a t i o n is a n t i c i p a t e d , n o r a t t e m p e r a t u r e s
o v e r 9 2 5 F. ( A l s o see f o o t n o t e t a b l e F - 9 )
( 2 ) Possible leakage o f j o i n t
( 3 ) * Seal w e l d i n g m a y b e required-see f o o t n o t e t o
c h a r t 2.3
(4) S t r e n g t h o f t h e p i p e is reduced, as f o r m i n g t h e
s c r e w t h r e a d reduces t h e w a l l t h i c k n e s s
CHART 2 3
SCREWED PIPING
i-2
11
CJ
A::
Easily m a d e f r o m p i p e a n d f i t t i n g s o n site
M i n i m i z e s f i r e h a z a r d w h e n i n s t a l l i n g p i p i n g in
areas w h e r e f l a m m a b l e gases o r l i q u i d s a r e
present
THREAD EhGACEUENT
S c r e w e d p i p i n g is p i p i n g assembled f r o m t h r e a d e d p i p e a n d f i t t i n g s
Threaded malleable-iron a n d cast-iron fittings are extensively used f o r plumbi n g in buildings. I n i n d u s t r i a l applications, Class 1 5 0 a n d 300 galvanized
m a l l e a b l e - i r o n f i t t i n g s a n d s i m i l a r l y r a t e d valves a r e u s e d f o r d r i n k i n g w a t e r
a n d a i r lines. D i m e n s i o n s o f malleable-iron f i t t i n g s a r e g i v e n in t a b l e 0 - 1 1.
2.3
CLASSES OF
FITTINGS WHICH
A R E COMPATIBLE
ends.
FULLCOUPLING
FIGURE 2.37
PRESSURE
(RATING)
CLASS
CONTROL VALVES
IUSUALLY FLANGED)
V A L V E S OTHER THAN
CONTROL V A L V E S
600 (ANSI)
800 1API)
states that seal weldjng shall not be considered to contribute to the nmrqth of the
joint
SEAL WELOING APPLICATIONS
0n.plot: On all screwed connections w i t h ~ nbattery Itrntts, wtth the axceptlon of ptptrq carrylrq air or
other inen gas. and water
0ff.plot: On wrmed lines lor hydrocarbon service and lor lines convryirq dang.rw~.lox~C,~ w O S N ~
or valuable fluids
FIGURE 2.38
REDUCING COUPLING
THREADED UNION
FIGURE 2.40
NIPPLES join unions, valves, strainers, fittings, etc. Basically a short length
of pipe either fully threaded (close nipple) or threaded both ends (TEE), or
plain one end and threaded one end (POE-TOE). Available in various lengths
-refer t o table 0-11. Nipples can be obtained with a Victaulic groove at one
end.
F I G U R E 2.39
NIPPLE
( c ) NIPPLE (POE-TOE)
N I P P L E (TBE)
PIPE-TO.TUBE CONNECTOR
FIGURE 2.41
(d) T A N K NIPPLE
Wall of
FIGURE 2.42
LARGER to SMALLER
AHHREvlAT1ONS:
Regular and reducing types are available from stock. For example, a reducing
flange to connect a NPS 1 pipe t o a Class 150 NPS 1% line-size flange is
specified:
FIGURE 2.45
TABLE 2.4
THRD ITEM
BW ITEM or PIPE
THRD ITEM*
THUD ITEM
THRD ITEM
BW ITEM*
SWG 1% x 1 TBE
SWG 2 x 1 BLE-TSE
SWG 3 x 2 TLE-BSE
BW = Butt welding
THRD = Threaded
TBE =Threaded both ends
TSE = Threaded small end
.
FITTINGS FOR BRANCHING FROM
SCREWED SYSTEMS
FIGURE 2.43
pipe. Reducing tees are made by boring and tapping standard forged blanks.
ELBOWS make
Street elbows having a integral nipple at one end (see table 0 - 1 l),are
available
T H R E A D E D ELBOWS, 45 and 90 DEGREE
REDUCING ON BRANCH
RED T E E 1 %
--
FIGURE 2.44
x 1%
- -
FIGURE 2.46
R E D U C I N G TEE
TABLE
2.4
LATERAL makes full-size 45-degree branch from the main run of pipe.
THREADED LATERAL
FIGURE 2.47
The next four fittings for branching are made b y Bonny Forge. These fittings
offer a means of joining screwed piping to a welded run, and for making
instrument connections. The advantages are that the welding end does not
require reinforcement and that the ends are shaped t o the curvature of the
run pipe.
THREDOLET makes a 90-degree branch, full or reducing, on straight plpe.
Flat-based thredolets are available for branch connections on pipe caps and
vessel heads.
THREDOLET
FIGURE 2.60
CROSS Remarks for butt-welding cross apply - see 2.3.2. Reducing crosses
are made b y boring and tapping standard forged blanks.
THREADED CROSS
FIGURE 2.48
FIGURE 2.51
pipes for instruments, or for vessel nozzles. Welding heat may cause ernbrittlement of the threads of this short fitting. Requires shaping.
THREADED HALFCOUPLING & FULLCOUPLING
FIGURE 2.49
necting t o pipe.
TANK NIPPLE See 2.5.1, figure 2.39(d).
FIGURE 2.62
PIPE THREADS
2.5+5
FIGURE 2.53
p
.
2
1.5.5
Tapered and straight threads will mate. Taperhaper and taperlstraight (both
types) joints are self sealing with the use of pipe dope (a compound spread
on the threads which lubricates and seals the joint on assembly), or plastic
tape (Teflon). Tape is wrapped around the external thread before the joint is
assembled. A straightlstraight screwed joint requires locknuts and gaskets to
ensure sealing -see fig. 2.39 ( d ) .
Standard ANSl 81.20.3 defines 'dryseal' threads. Dryseal threads seal against
line pressure without the use of pipe dope or tape. The seal is obtained by
using a modified thread form of sharp crest and flat root. This causes interference (metal-to-metal contact) between the engaged threads, and prevents
leakage through the spiral cavity of mating threads.
CLOSURES
2.5.4
ANSl 81.20.1: PlPE THREADS, GENERAL PURPOSE
FIGURE 2.54
N PT
NPTR
N PSC
N PSM
NPSL
NPSH
head plug:
BARSTOCK PLUG ( I N TEE)
FIGURE 2.55
3-8NPT
FIGURE'
' 2.47-2.55
2.6
2.6.1
ation of flange and stub end presents similar geometry t o the raised-face
flange and can be used where severe bending stresses will not occur. Advant.
ages of this flange are stated in 2.3.1.
The term 'finish' refers t o the type of surface produced by machining the
flange face which contacts the gasket. T w o principal types of finish are produced, the 'serrated' and 'smooth'.
FIGURE 2.56
FLAT-FACE
R I N G JOINT
L A P JOINT
2.6.2
Bolt holes in flanges are equally spaced. Specifying the number of holes, diameter of the b o l t circle and hole size sets the bolting configuration. Number
of bolt holes per flange is given i n tables F.
The RAISED FACE is 1116-inch high for Classes 150 and 300 flanges, and
114.inch high for all other classes. Class 250 cast-iron flanges and flanged
fittings also have the 1116-inch raised face.
Flanges are positioned so that bolts straddle vertical and horizontal centerlines. This is the normal position of b o l t holes on all flanged items.
BOLTS FOR FLANGES
0.06-inch raised face on flanges in Classes 150 and 300, but exclude the
025-inch raised face on flanges in Classes 400 thru 2500. Tables F
include the raised face for all flange Classes.
FLAT FACE Most common uses are for mating with non-steel flanges on
bodies of pumps, etc, and for mating with Class 125 cast-ironvalves and fittings.
Flat-faced flanges are used with a gasket whose outer diameter equals that of
the flange - this reduces the danger of cracking a cast-iron, bronze or plastic
flange when the assembly is tightened.
2.6.3
Two types of bolting are available: the studbolt using t w o nuts, and !he
machine bolt using one nut. Both boltings are illustrated in figure 2.57.
Studbolt thread lengths and diameters are given in tables F.
Studbolts have largely displaced regular bolts for bolting flanged piping joints.
Three advantages of using studbolts are:
(1)
(2)
(3)
FIGURE 2.57
GASKET CHARACTERISTICS
TABLE 2.5
STUDBOLT
SQUARE-HEAD
MACHINE BOLT
H E X NUT
HEX NUT
--
HEX NUT
UNIFIED INCH SCREW THREADS (UN AND UNR THREAD FORM) UNR
indicates rounded root contour, and applies t o external threads only. Flat, or
rounded root is optional with the U N thread. There are four Unified Screw
Threads: Unified Coarse (UNCI UNCR), Unified Fine (UNFIUNFR), Unified
Extra-fine (UNEFJUNEFR) and Unified Selected (UNSIUNSR), with three
classes of f i t : 1A, 2 A and 3 A for external threads; 1 B, 28, and 3 8 for internal
threads. (Class 3 has the least clearance.) The standard is ANSI 61.1. which
incorporates a metric translation.
UNC (Class 2 medium f i t bolt and nut) is used for bolts and studbolts in
piping, and specified in the following order:
GASKETS
BOLT:
NUT:
FIGURE 2.68
,-SINGLE INSULATING SET
STEEL WASHER
INSULATING WASHER
'/2 - 13 UNC 2A
% - 13 UNC 2 8
INSULATING GASKET
INSULATING SLEEVE
INSULATING WASHER
STEEL WASHER
2.6.4
Gaskets are used t o make a fluid-resistant seal between two surfaces. The
common gasket patterns for pipe flanges are the full-face and ring types, for
use with flat-faced and raised-face flanges respectively. Refer to figure 2.56.
Widely-used materials for gaskets are compressed asbestos (1116-inch thick)
and asbestos-filled metal ('spiral-wound', 0.175-inch thick). The filled-metal
gasket is especially useful if maintenance requires repeated uncoupling of
flanges, as the gasket separates cleanly and is often reusable.
Choice of gasket is decided by:
(1) Temperature, pressure and corrosive nature of the conveyed fluid
(2) Whether maintenance or operation requires repeated uncoupling
(3) CodeJenvironmental requirements that may apply
(4) Cost
TEMPORARY C L O S U R E S FOR L I N E S
2.7
IN-LINE CLOSURES
The valves described in 3.1 may not offer complete security against leakage,
and one of the following methods of temporary closure can be used: Lineblind valve, line blind (including special types.for use with ring.joint flanges),
spectacle plate (so-called from its shape), 'double block and bleed', and blind
flanges replacing a removable spool. The last three closures are illustrated in
f~gures2.59 thru 2.61.
I t may be required that adjacent parts of a line are electrically insulated from
one another, and this may be effected by inserting a flanged joint fitted
with an insulating gasket set between the parts. A gasket electrically insulates the flange faces, and sleeves and washers insulate the bolts from one
or both flanges, as illustrated i n figure 2.58.
1211
TABLE
2.5
Figure 2.60 shows the bleed ring connected to a bleed valve-see 3.1.1 1. The
use of a tapped valve rather than a bleed ring should be considered, as i t is
a more economic arrangement, and usually can be specified merely by adding
a suffix to the valve ordering number.
FIGURE 2.50
LINE
BLIND
J-a.-c,k,
screw
J a c k screw-,
J a c k screw
Table 2.6 compares the advantages of the four in-line temporary closures:
screw
IN-LINE CLOSURES
TABLE 2.6
J a c k screw
SIDE V I E W :
~t should be noted
t h a t jack screws may
sleze In corrosive
condltlons
DEPENDING ON FREQUENCY
FIGURE 2.60
'BLOCK' VALVE \
/'BLOCK'
VALVE
2.7.2
LTAPPING
ONE OF THE 'BLOCK'
Temporary bolted closures include blind flanges using flat gaskets or ring
joints, T-bolt closures, welded-on closures with hinged doors - including the
boltless manhole cover (Robert Jenkins, England) and closures primarily intended for vessels, such as the Lanape range (Bonney Forge) which may also
be used with pipe of large diameter. The blind flange is mostly used w i t h a
view to future expansion of the piping system, or for cleaning, inspection, etc.
Hinged closures are often installed on vessels; infrequently on pipe.
REMOVABLE SPOOL
FIGURE 2.61
Typical use is for connecting temporarily to tank cars, trucks or process vessels. Inter-trades agreements permit plant operators t o attach and uncouple
these boltless connectors. Certain temporary connectors have built-in valves.
Evertite manufactures a double shut-off connector for liquids, and Schrader
a valved connector for air lines.
BOLTED QUICK-COUPLINGS
2.8.2
(1) Re-routing or re-spacing the line. (2) Expansion loops-see figure 6.1.
(3)Calculated placement of anchors. (4) Cold springing-see 6.1. Bellows-type
expansion joints of the type shown in figure 2.63 are also used t o absorb
vibration.
SIMPLE BELLOWS
FIGURE 2.63
ARTICULATED BELLOWS
FIGURE 2.64
,-. .
2 ::::
oil and gas. Well-known manufacturers include Victaulic, Dresser and SmithBlair. Advantages: (1) Quick fitting and removal. (2) Joint may take up some
deflection and expansion. (3) End preparation of pipe is not needed.
VlCTAULlC COMPRESSION SLEEVE COUPLING
FIGURE 2.62
~
ARTICULATED TWIN-BELLOWS ASSEMBLY
FIGURE 2.66
2.59-2.65
L-
.-
2.9
2.9.1
,----
TABLE
,2.6
[231
SLIDINGSLEEVE-AND-ANCHOR SUPPORT
FIGURE 2.66
2.10.3
STRAINERS
2.9.2
SEPARATOR
For filling and emptying railcars, tankers, etc., thru rigid pipe, it is necessary
to design articulated piping, using 'swiveling' joints, or 'ball' joints (the latter
is a 'universal' joint). Flexible hose has many uses especially where there is
a need for temporary connections, or where vibration or movement occurs.
Chemical-resistant and/or armored hoses are available in regular or jacketed
forms (see figure 6.39).
WET STEAM
D R I E R STEAM
2.10
2.10.1
Devices are included in process and service lines to separate and collect undesirable solid or liquid material. Pipe scale, loose weld metal, unreacted or
decomposed process material, precipitates, lubricants, oils, or water may harm
either equipment or the process.
Common forms of line-installed separator are illustrated in figures 2.67 and
2.68. Other more elaborate separators mentioned in 3.3.3 are available, but
these fall more into the category of process equipment, normally selected by
the process engineer.
Air and some other gases in liquid-bearing lines are normally self-collecting at
piping high points and at the remote ends of headers, and are vented by discharge valves - see 3.1.9.
SEPARATORS
FIGURE 2.67
2.10.2
These permanent devices are used to collect droplets from a gaseous stream,
for example, to collect oil droplets from compressed air, or condensate droplets from wet steam. Figure 2.67 shows a separator in which droplets in the
stream collect in chevroned grooves in the barrier and drain to the small well.
Collected liquid is discharged via a trap-see 3.1.9 and 6.10.7.
REMOVED WATER
PIPED T O T R A P
STRAINER
FIGURE 2.68
SCREENS
2.10.4
Simple temporary strainers made from perforated sheet metal and/or wire
mesh are used for startup operations on the suction side of pumps and comppressors, especially where there is a long run of piping before the unit that
may contain weld spatter or material inadvertently left in the pipe. After
startup, the screen usually is removed.
I t may be necessary to arrange for a small removable spool to accommodate
the screen. I t is important that the flow in suction lines should not be
restricted. Cone-shaped screens are therefor preferred, with cylindric
types as second choice. Flat screens are better reserved for low-suction heads
SCREEN BETWEEN FLANGES
FIGURE 2.69
REINFORCEMENTS
BRANCH CONNECTIONS
USUAL DIRECTION
O F FLOW T H R U
T H E SCREEN
REINFORCING SADDLES
DRIPLEG CONSTRUCTION
FIGURE 2.70
(a) REGULAR SADDLE
VENT HOLE
-FIGURE
2.66-2.71
L
T R A P PIPING
CONNECTION
BLOWOOWN
CONNECTION
Often made from pipe and fittings, the dripleg is an inexpensive means of
collecting condensate. Figure 2.70 shows a dripleg fitted to a horizontal pipe.
Removal of condensate from steam lines is discussed in 6.10. Recommended
sizes for driplegs are given in table 6.10.
V E N T HOL
(In saddle o
---
FG
I URE 2.72~
SUPPORTS ALLOWING
FREE MOVEMENT OF PIPE
(COURTESY VOKES%ERGEN.GENSPRING L T D l
1. C O N S T A N T L O A D T Y P E
ICOURTESY U N I O N CARBIDE1
2. V A R I A B L E L O A D T Y P E
LOAD
INP'CATOR-
6 HYDROSTATIC
' U I N D O R F SYSTEM'
SPRING SUPPORT
INDICATOR
I
I
\\
2.12
Symbols for drafting various types of support are shown in chart 5.7. For
designing support systems, see 6.2.
PIPE SUPPORTS
2.12.1
Pipe supports s h ~ ~ u be
l d as simple as conditions allow. Stock items are used
where practicable, especially for piping held from above. To support piping
from below, supports are usually made to suit from platestock, pipe, and
pieces of structural steel.
2.12.2
coil spring in a housing. The weight of the piping rests on the spring in compression. The spring permits a limited amount of thermal movement. A
variable spring
hanger holding up a vertical line will reduce its lifting force as
the line expands toward it. A variable spring support would increase its lifting force as the line expands toward it. Both place a load on the piping system.
where this is undesirable, a constant-load hanger can be used instead.
The weight
piping is
carried On
made from
structural steel, or steel and concrete. (The term 'support' is also used in
reference to hangers.)
HANGER Device which suspends piping (usually a single line) from structural steel, concrete or wood. Hangers are usually adjustable for height.
ANCHOR A rigid support which prevents transmission of movement (thermal,
vibratory, etc.) along piping. Construction may be from steel plate, brackets,
flanges, rods, etc. Attachment of an anchor to pipe should preferably encircle
the pipe and be welded all around as this gives a better distribution of stress
in the pipe wall.
One end of the unit is attached to piping and the other to structural steel or
concrete. The unit expands or contracts to absorb slow movement of piping,
but is rigid to rapid movement.
of piping.
housing which. is fitted between piping and a rigid structure. Its function
is to buffer vibration and sway.
DUMMY LEG An extension piece (of pipe or rolled steel section) welded
to an elbow in order to support the line-see figure 2.72A and table 6.3.
WELDING TO PIPE
2.12.3
If the applicable code permits, lugs may be welded to pipe. Figure 2.72A
illustrates some common arrangements using welded lugs, rolled steel sections
and pipe, for:-
sideways.
(1)
(2)
SHOE A metal piece attached to the underside of a pipe which rests on sup-
porting steel. Primarily used to reduce wear from sliding for lines subject to
movement. Permits insulation to be applied to pipe.
Welding supports to prelined pipe will usually spoil the lining, and therefor
lugs, etc., must be welded to pipe and fittings before the lining is applied.
Welding of supports and lugs to pipes and vessels to be stress-relievedshould
be done before heat treatment.
I
n u ~ c w w r f
CENTRIFUGAL
OlHCIIILA?CO
lYPfl01? U Y
PIOIELLOI
*XI*LfLD*
TURBINE
YOLUTS
DlFFusf~
PLOW 1 1 7 1 A 7
W N I 1 A U T D l l Y l IPEfD
DIYHIROL PIEPURE
TUIIINE
UNIFORM l F T O I k I %&0UNCHANGED
LOW TO M l O l U U
VANE
NUTATOR
YURGEAR
rn:::::$s,
WINGING VANE
NUTlTiNG
01%
E VARI*TION
LOWTOHIGH
~EHRENS
ICREW
rtnoN
CPEY.rHI
OIAPHIAGY
UOYNO
I W & I Y ?LATE
RADIAL.
TRIPLE SCREW
P E R I ~ ~ L T ~ C
% N N O Lscmrw
~
e
.
.
.
U N l F O l M AT CONSTANT D C l V l I I E E D
LOWTOUfDiYM
MEDIUM
LOWTOHIGH
MEDIUM
L O W TO * G i (
LOWTO HIGH
LOWTOMEDlUM
LOW
b
b
b
b
b
OILS
b
b
b
b
CLA* LIOUIOS
V I ( C O " I LIQUIOB
SLUIIIEI
EUULIIONS
r m f s
b
b
LUYII
b
b
b
b
X
X
TYPES OF PUMP
VELOCITY HEAD
A pump is a device for moving a fluid from one place to another thru pipes
or channels. Chart 3.3, a selection guide for pumps, puts various types of
pump used industrially into five catagories, based on operating principle. I n
common reference, the terms centrifugal, rotary, screw, and reciprocating
are used. Chart 3.3 is not comprehensive: pumps utilizing other principles
are i n use. A b o u t nine o u t o f ten pumps used in industry are o f the centrifugal type.
Usually the liquid being pumped is stationary before entering the suction
piping, and some power is absorbed in accelerating i t t o the suction line
velocity. This causes a small 'velocity head' loss (usually about 1 ft) and
may be found from table 3.2, which is applicable to liquid of any density,
if the velocity head is read as feet of the liquid concerned.
A pump imparts energy to the pumped liquid. This energy is able to raise the
liquid to a height, or 'head'. The 'total head' of a pump (in f t ) is the energy
(in ft-lb) imparted by the pump t o each pound of liquid. I n piped systems,
part of the total head is used t o overcome friction i n the piping, which results
in a pressure drop (or 'headloss').
For a centrifugal pump, the same total head can be imparted to all liquids of
comparable viscosity, and is independent of the liquid's density: the required
driving power increases with density. Figure 3.3 relates the total head provided by the pump to the headlosses in the pumped system.
iFt/=)
VELOCITY
VELOCITYHEAD
iFrl
TABLE 3.2
5
0.39
0.56
0.76
10.25
0.99
10
1.261.55
12
15
2.24-q
Flow rate, liquid velocity and cross-sectional area (at right angles to flow)
are related b y the formulas:
Flow rate in cubic feet per second
( v ) ( a )/(I441
(3.1 169)( v ) ( a )
where:
POWER CALCULATIONS
PRESSURE & 'HEAD'
If S.G. = specific gravity of the pumped liquid, H = total head in feet of the
pumped liquid, a n d p = pressure drop in PSI, then
Hydraulic horsepower =
TABLE
3.2
The mechanical efficiency, e, of a pump is defined as the hydraulic horsepower (power transferred to the pumped liquid) divided by the brake horsepower (power applied to the driving shaft of the pump).
If the pump is driven by an electric motor which has a mechanical efficiency em, the electricity demand is:
Kilowatt ( K W ) =
(GPM)(H)(S.G.) (GPM)(p)
(531O)(e)(em)
(2299) (e)(em)
Compressors are used to supply high-pressure air for plant use, to pressurize
refrigerant vapors for cooling systems, to liquefy gases, etc. They are rated
by their maximum output pressure and the number of cubic feet per minute
of a gas handled at a specified speed or power, stated at 'standard conditions',
60 F and 14.7 PSlA (not at compressed volume). 60 F is accepted asstandard
temperature by the gas industry.
The term 'compressor' is usually reserved for machines developing high pressures i n closed systems, and the terms 'blower' and 'fan' for machines working
at low pressures i n open-ended systems.
TABLE 3.3
MACHINE
DISCHARGE PRESSURE R A N G E
COMPRESSOR
BLOWER
1 thru 15 PSlG
Up t o 1 PSlG
TYPES O F COMPRESSOR
RECIPROCATING COMPRESSOR Air or other gas is pressurized in cylinders
by reciprocating pistons. I f the compressor is lubricated, the outflow may
be contaminated by oil. If an oil-free outflow is required, the pistons may
be fitted with graphite or teflon piston rings. Flow is pulsating.
ROTARY SCREW COMPRESSOR Air or other gas enters pockets formed
between mating rotors and a casing wall. The pockets rotate away from
the inlet, taking the gas toward the discharge end. The rotors do not touch
each other or the casing wall. Outflow is uncontaminated in the 'dry type'
of machine, in which power is applied t o both rotors thru external timing
gears. I n the 'wet type', power is applied to one rotor, and both rotors are
separated by an oil film, which contaminates the discharge. Flow is uniform.
ROTARY V A N E COMPRESSOR resembles the rotary vane pump shown in
chart 3.3. Variation i n the volume enclosed by adjacent vanes as they rotate
produces compression. Ample lubrication is required, which may introduce
contamination. Flow is uniform.
ROTARY LOBE COMPRESSOR consists of two synchronized lobed rotors
turning within a casing, in the same way as the pump shown in chart 3.3
(under 'spurgear' type). The rotors do not touch each other or the casing.
No lubrication is used within the casing, and the outflow is not contaminated.
Flow is uniform. This machine is often referred to as a 'blower'.
D Y N A M I C COMPRESSORS resemble gas turbines acting i n reverse. Both
axial-flow machines and centrifugal machines (with radial flow) are available.
Centrifugal compressors commonly have either one or two stages. Axial
compressors have at least two stages, but seldom more than 16 stages.
The outflow is not contaminated. Flow is uniform.
L I Q U I D R I N G COMPRESSOR This type of compressor consists of a single
multi-bladed rotor which turns within a casing of approximately elliptic cross
section. A controlled volume of liquid in the casing is thrown to the casing
wall with rotation of the vanes. This liquid serves both to compress and to
seal. Inlet and outlet ports located i n the hub communicate with the pockets
formed between the vanes and the liquid ring. These compressors have special
advantages: wet gases and liquid carryover including hydrocarbons which are
troublesome with other compressors are easily handled. Additional cooling is
seldom required. Condensible vapor can be recovered by using liquid similar
t o that in the ring. Flow is uniform.
COMPRESSING I N STAGES
rocating compressors create pulsations i n the air or gas which may cause the
TABLE 3.4
COMPRESSOR TYPE
The location of the following four items of equipment is shown i n figure 6.23:
SEPARATOR (normally used only with air compressors) A Water Separator
is often provided following the aftercooler, and, sometimes, also at the intake
a compressor having a long suction line, if water is likely to collect in
the line. Each separator is provided with a drain to allow continuous removal
of water.
RECEIVER Refer to 'Discharge (supply) lines' and 'Storing compressed air',
this section.
SILENCER is used to suppress objectionable sound which may radiate from
an air intake.
FILTER is provided in the suction line to an air compressor to collect
particulate matter.
tcl
FLOW OF COMPRESSED A I R :
PRESSURE D R O P S O V E R 100 F t PI!,
WITH AIR ENTERING AT loo PSIG
(Adapted from data published by ~ n ~ e r s o l l - R a n d l
T A B L E 3.5
INFLOW
(SCFM)
40
70
90
100
400
700
900
vent excessive noise and starvation of the air supply. If the first compression
stage is reciprocating, the suction line should allow a 10 t o 23 ftlsec flow:
if a single-stage reciprocating compressor is used, the intake flow should not
be faster than 20 ftlsec. Dynamic compressors can operate with faster intake
velocities, but 40 ftlsec is suggested as a maximum. The inlet reducer for
a dynamic compressor should be placed close to the inlet nozzle.
1,000
DISCHARGE (SUPPLY) LINES are sized for 150 t o 175% of average flow,
4.000
7.000
9.000
10,000
40,000
depending on the number of outlets in use at any time. The pressure loss in
a branch should be limited t o 3 PSI. The pressure drop in a hose should not
exceed 5 PSI. The pressure drop i n distribution piping, from the compressor
to the most remote part of the system, should not be greater than 5 PSI (not
including hoses).
These suggested pressure drops may be used to select line sizes with the aid
of table 3.5. From the required SCFM flow in the line to be sized, find the
next higher flow in the table. Multiply the allowed pressure drop (PSI) in the
line by 100 and divide by the length of the line i n feet to obtain the PSI drop
per 100 ft-find the next lower figure to this in the table, and read required
line size.
Equipment drawing air at a high rate for a short period is best served by a
receiver close t o the point of maximum use-lines can then be sized on
average demand. A minimum receiver size of double the SCF used in intermittent demand should limit the pressure drop at the end of the period of use to
about 20% in the worst instances and keep i t under 10% in most others.
-SCHEDULE 40 PIPE
? 4 1 1 % 2 2 % 3 4 6
1.24 0.37
3.77 1.05 0.12
Pressure drop rmeller then
then 0.1 PSI per I00 It
6.00 1.69 0.19
7.53 2.09 0.24
3.59 0.98 0.41 0.13
32.2
10.8 2.92 1.19 0.38 0.10
17.9 4.78 1.97 0.62 0.15
2.43 0.76 0.19 22.0 5.90
11.9 2.90 0.35
8.77 1.06
Pressure drop larger
14.6
1.75
than 35 PSI per 100 If
18.0 2.13
33.8
POWER CONSUMPTION
76
100
125
SlNGLEgTAQE
14
18
22
24
TWOSTAGE
13
16
18
21
PSI0
H
P
w 100 CFM INFLOW
'Unloading' is the removal of the compression load from the running compressor. Compressors are unloaded at startup and for short periods when
demand for gas falls off. Damage to the compressor's drive motor can result
if full compression duties are applied suddenly.
COOLING-WATER REQUIREMENTS
If the vendor does not provide means of unloading the compressor, a manual
or automatic bypass line should be provided between suction and discharge
(on the compressor's side of any isolating valves)-see figure 6.23.
Provision should be made so that the discharge pressure cannot rise above a
value which would damage the compressor or its driver. Automatic unloading
will ensure this, and the control actions are listed in table 3.6.
AUTOMATIC UNLOADING
ACTIONS FOR COMPRESSORS
COMPRESSOR
Low-reacher
lower sat value
Running
H i h-reacher
higaer set value
Idling
Low-reaches
reload pressure
before idling
period is over
Medium-idlin
period ends beeore
reload preseure
is reached
1,
CALCULATIONS:
(1)
(2)
(3)
(4)
AUTOMATIC CONTROL
ACTION
Not running
The following calculation (taken from the referenced Atlas Copco manual)
is for a two-stage compressor, and is based on moisture content given in the
table below:
DATA:
~~~~~~E
TABLE 3.6
From the table, weight of water vapor in 2225 SCFM air at 86 F and
75% R H = (0.00189)(2225)(0.75) = 3.15 Iblmin.
Rate of removal of condensed water from intercooler, thru trap
= (0.8)[3.15 - (0.00189)(2225)(14.7)/(40)] = 1.28 Iblmin., or
(1.28)(60)/(8.33) = 9.2 US GPH
Rate of removal of condensed water from aftercooler, thru trap
= (0.9) l3.15 - 1.28 - (0.00189)(2225)(14.7)1(115)1 = 1.20 Iblmin., or
(1.20)(60)/(8.33) = 8.6 US GPH
Total rate at which water is removed from both coolers
= 9.2 + 8.6 = 17.8 US GPH
divide the compressor rating in SCFM by ten to get the volume in cubic feet
for the receiver. For example, if the compressor is designed to take 5500
cubic feet per minute, a receiver volume of about 550 cubic feet is adequate.
This rule is considered suitable for outflow pressures up to about 125 PSlG
and where the continuously running compressor is unloaded by automatic
valves-see 'Unloading' above. An extensive piping system for distributing
compressed air or other gas may have a capacity sufficiently large in itself to
serve as a receiver.
1441
3.3
PROCESS EQUIPMENT
SEPARATION
Process equipment is a term used to cover the many types of equipment used
to perform one or more of these basic operations on the process material:
(1)
CHEMICAL REACTION
(2)
MIXING
(3)
SEPARATION
(41
(5)
H E A T TRANSFER
3.3.1
S+S,S+L
L+L,L+G,G+G
S+S.S+L
PROPORTIONING PUMP
L+L
PROPORTIONING VALVE
L+L
IG
GAS. L = L I O U I D . S
OUTFLOW
MATERIAL
S +L
None
L I l I . L121. t
CYCLONE
LII) + ~ ( 2 1
StG
None
G. S
DEAERATOR
L+G
DEFOAMER
L+G
DISTILLATION COLUMN
L(II + ~ 1 2 1
L(II
~ ( 2 )
DRYER
s+ L
L'
D R Y SCREEN
SI1) + S(2)
S(1)
S12)
EVAPORATOR
L+s
LII) + ~ ( 2 )
L+S
~(1)
L'
~ ( 2 ')
FILTER PRESS
S+ L
FLOTATION TANK
S+ L
FRACTIONATION COLUMN
LI1) + L121
+ L(3l + etc.
None
L(1I. LIZ).
L(3), etc. t
SCRUBBER
S+G
SETTLING TANK
St L
STRIPPER
L(1) + L(2)
L(1)
LIZ)
IG
GAS. L
'R8rnov.a
as vapor
3.3.4
PHASES M I X E D
EDUCTOR
TABLE 3.7
S+L,L+L
RETAINED
MATERIAL
CONTINUOUS C E N T R I F U G E
FEED
MATERIAL
CENTRIFUGE
t S e p a r a t e flows
3.3.2
MIXING
AGITATOR
. <
1
EQUIPMENT
EQUIPMENT
3 1 .3.5
TABLE 3.8
SEPARATION EQUIPMENT
MIXING EQUIPMENT
3.3.5
SOLID I
h
1451
TABLES
3.6-3.8
-
..
. ., ,,Y,bdJliy
1
~ t l i d~i i UIirlreo
~
~vessel
2
exchanging heat between two fluids which are kept separated.The commonest
form of heat exchanger is the 'shell-and-tube' exchanger, consisting of a
bundle of tubes held inside a 'shell' (the vessel part). One fluid passes inside
the tubes, the other thru the space between the tubes and shell. Exchanged
heat has to flow thru the tube walls. Refer to 6.8 ('Keeping process material
at the right temperature') and to 6.6 for piping shell-and.tube heat exchangers.
Heat exchange with process material can take place i n a variety of other
equipment, such as condensers, evaporators, heaters, chillers, etc.
MULTIFUNCTION EQUIPMENT
3.3.6
PIPING SYMBOLS
5.1.1
Hand-drawn piping layouts depict pipe by single lines for clarityand economy.
Pipe and flanges are sometimes drawn partially 'double line' to display clearances. Computer drawn layouts can show piping in plan, elevational and isometric views in single line, or (without additional effort or expense) in double
line. Double line representation is best reserved for three-dimensional views,
such as isos.
The ways of showing joints set out in the standard ANSI Y32.2.3 are not
typical of current industrial practice. The standard's symbol for a butt-weld
as shown in table 5.1 iscommonly used to indicate a butt-weld to be made 'in
the field' (field weld).
SHOWING NONFLANGED JOINTS
AT ELBOWS
In double-line drawing, valves are shown by the symbols in chart 5.6 (refer
to the panel '0 rafting valves'). Oou ble-line representation is not used for
entire piping arrangements, as it is very time-consuming, difficult to read,
and not justified technically.
DOU BLE-L1 NE
PRESENTATION
BUTT WELD
SIMPLIFIED
PRACTICE *
SINGLE-LINE
PRESENTATION
-c.. I~.
CONVENTIONAL
PRACTICE
ANSI Y32.2.3
(Not current
practice)
r
r
TABLE 5.1
SOCKET WELD
SCREWED JOINT
I I
-rf r -r~
The loint symbol m.y be omitted it the type of ioint is determin.d by I piping IPlCifiCltion. 't is ulUllly
preferred to use the dot weld symbol to mek. the type of construction clelr: tor .ump". to distinguish
between. tee Ind I stub-in.
[53]
TABC-E--
5.1
5.1.2
Symbols that are shown in a similar way in all systems are collected in chart
5.7.
Chart 5.1 shows commonly accepted ways of drawing various lines. Many
other line symbols have been devised but most of these are not readily recognized, and i t is better t o state in words the function of special lines, particularly on process flow diagrams and P&ID1s. The designer or draftsman
should use his current emplover's symbols.
T 5.1
LlNE
PIPIUO DRAWIN48 IPLANI. I L E V A I I O W . I W I AND W O O L ORAWINOSI
111--
--
FUTURE PIPING
---
EXISIINGPIPING
E W I P M E N T OUTLINES. DIMENSION LlNES. OOUBLE LlNE PlPlNG
FUTURE
,
EXISTING-
---- -
ruruar-
FUTURE EOUIWENT
XI=
EXISTING E W I P M L N T
--
---
OR U T l L l r v
U O U L I I N I T R U l E N l I LINES
INSTRUMENT AIR IPNEUMATIC SIGNAL1
------
ELECTRIC
t
----t------t------
ELECTROUAGNEIIC~ OR SONIC
-'L
5.1.3
5.1.7
Chart 5.8 gives some symbols, signs, etc., which are used generally and are
likely to be found or needed on piping drawings
MATCWLINE
5.1.6
5.1.4
Chart 5.6 shows ways of denoting valves, including stems, handwheels and
other operators. The symbols are based on ANSl 232.2.3, but more valve
types are covered and the presentation is up-dated. Valve handwheels should
to be drawn t o scale with valve stem shown fully extended.
[541
A T Y O Y H E R I C l m N E ROOF1 TANK
GAS HOLDER
CATALVTIC REACTOR
PLATE
PACKED
SECTION
VESSEL
OPENO, VENTED
i l r C I I O * l i ~ lP ~ C l r o i
mLuMmr
PRESSURIZED
RESERVOIR
T O W ~ R ~
HEAT-EXCHANGE EQUIPMENT
'
THICKENER or CLARlflER
I
PROCESSSTREAM
TUBE FEED
bi.
//
"
!UNDERFLOW
'/'
CONDENSATE
SHELLJIDE FEED
COOLED OUTFLOW
WELL*
WATERCOOLED CONDENSER
TUBE H U T EXCHANOER
THICKENER
JACKETED KETTLE
COOLINO TOWER
ATTRITION EQUIPMENT
I
SEPARATION EIIPMENT
I
DRIED
PRODUCT
I*
L OU 0
+I
b'
'I
OONTINUOUS TUNNEL DRYER
SOL DS
It LIOUIDI
SOLIDS
1' LIOUIDI
SEPARATOR
SEPARATOR
WITH AUTOMATIC DRAIN
DRIED
PRODUCT
LIOUD
P........ .-
..........
THICKENED
OUTFLOW
IT Y ( X f I . INXCTOR, EDUCTOR or U n O R
FEED :,
.............
\Jh '
DESICCANT D R I E R
ROTARVDRUM FILTER
CEMRIFWIE
ELECTRICAL PRECIPITATOR
CVCLDYC
N.8
NORMALLY OPEN
NORMALLY CLOSED
VALVE OPERATORS
-8
CONTROL
VALVES (GENERAL1
Sp#c,al (IP.~ 01 r.1~.
rnly b. 1ndlc.1.d
by the l y m b o l l p4v.n
SINGLE ACTING
CYLINDER
ROTARYMOTOR
I E l r t r I c %&I
In chart 5 6
{lsA
--gx
ss
DOUBLE ACTING
CYLINDER
DIAPHRAGM
iP-u~&l~nQdI
SOLENOID
ACCUMULATORS
RECIPROCATING PUMP
C E M R I F U O A L PUMP
RECEIVER FOR
AIR or OTHER GAS
SPRING-LOADED
GASCHARGED
WEIGHTED
SYMBOL
TYPE
TYPE
TVPE
TURBINE COMPRESSOR
II
ROTARY PUMP
CONVEYORS
DRIVERS
ROLLER CONVEYOR
l P H A S E ELECTRIC MOTOR
SCREW CONVEYOR
STEAM OR AIR
ENGINE DRIVER
I P H A S E ELECTRIC MOTOR
TURBINE DRIVER
STEAM OR AIR
BELTS a SHAKERS
DRAFTING VALVES
CHART 5.6 GIVES THE BASlC SYMBOLS FOR V A L V E S
THESE BASlC SYMBOLS ARE U S E 0 OR ADAPTED AS
FOLLOWS.
P & I D's
USE THE RELEVANT V A L V E SYMBOL TO SHOW THE
TYPE OF V A L V E . DRAW MOST SYMBOLS l i C ~ n . LONG.
M A N U A L OPERATORS ARE NOT SHOWN,
PIPING DRAWINGS
OPERATOR IS SHOWN I F IMPORTANT
111 SCREWED VALVES
USE T H E BASlC V A L V E SYMBOL. DRAW THE LENGTH
OF THE V A L V E TO SCALE.
I21 SOCKET.ENDED VALVES
I F THE PROJECT H A S A PIPING SPECIFICATION, USE
THE BASlC V A L V E SYMBOL. IF NOT, SHOW SOCKET
ENDS TO THE VALVES:
SINGLE-LINE
DOUBLE-LINE
,O
c
3
SYMBOL
NAME OF ITEM
BLEED RING
JACKETED PIPE
WITH INSULATION
---it_
SEE D W G
CONTROL STATION
(on P i n Vb-1
--------
DTL..
ORIFICE FLANGE
ASSEMBLY
-------
+
i
v
+
PERSONNEL
PROTECTION
D R A I N 01H U B I l n f l m r l
DRAIN
I f a l8nd
EDUCTOR
IPr0t.st1". U S
01 msulat~onl
11) wlrnout C k k s
D~swnnctod
'*
'T
Connstad
I l l WithCh.cl'
Dllsonnrmd
Conmmd
p
p
EJECTOR
ELECTRIC TRACING
REMOVABLE SPOOL
!
?
*
--
--1)t-
RUPTURE DISC
SCREEN
Conlo1
Mounud
b.mesn
i H k
F1.n~
GUIDE
4k0r+.1
4-
p
p
P
'REMovED
W I T E R ETC I
EXHAUST H E A D
l l o l tUlm1
EXHAUST
-STEAM1
SCREEN
F1.t
Mountad between Flanpes
EXPANSION S I N 1
STEAM TRACING
FLAME ARRESTOR
FLEXIBLE COUPLING
HOSE
n
I
-
i F l w lrom L to R I
BUTT WELDING
&
.
>
YI
SOCKET WELDING
E
FLANGED
--I[
HANGER
e
.-F-
SPRING HANGER
FLOOR SUPPORT
,T
SPRING SUPPORT
INSULATION
SCREWED
&
--.=
k --
SS
SYMBOL
DESCRIPTION
SYMBOL
DESCRIPTION
'CONSTRUCTION HOLD' M A R K I N G IF SUF
FICIENT INFORMATION IS NOT A V A I L A B L E
NORTH ARROWS.
10
I0
10
30
PLACE TRIANGLE
ADJACENT TO
REVISED AREA
ON FRONT OF SHEET--
(2)
L L l l
TYPICAL SECTION INDICATORS. LETTERS 'I'
A N D '0' SHOULD N O T BE USED TO A V O I D
CONFUSION WITH NUMERALS '1' A N D '0'.
I F MORE T H A N 24 SECTIONS ARE NEEDED.
USE COMBINATIONS OF LETTERS A N D NUM.
ERALS. SHOW NUMBER OF T H E D R A W I N G
ON WHICH SECTION W I L L APPEAR
OrAJ
DWG NO.
"'A"' 7 "' I
. .....
OPENINGS
ill OPENING WHICH M A Y BECOVERED. (ARCH.
A N D H & V DRAWINGS)
121 HOLE I A R C H 1
Ill ANGLE
(21 CHANNEL.
131 I-BEAM
DISCONTINUED VIEWS
D ~ m c n s ~ o nA
\I
'FITTING M A K E U P ' S Y M B O L
( N O T PREFERRED SEE 6.3.3, UNDER 'FITT.
ING MAKEUP')
I
SCREWTHREAO SYMBOLS
l V P E OF
,Dl.,
-----------
CHAIN SYMBOL
'LOO~ID~M~I~~CA~IOM
GRADE
EARTH
SOLID M A T E R I A L
aloe c r o u v r t i o n l
land
STEEL
'ONCRETE
BRICK &
STnNF MASnNRY
CHECKER PLATE
iilrp 100 I,"-I
GRATING
Spot
Ol
seam
CHART 5.9
DOY~~.-FIII.I
F"nQ'
~urir~ng
~ . l d l n g Symbol
Chaln Inl.rmltl.nl
F1II.I
W.lding
Symbo
St.gg.rod
Fllkt W d d l w Symbd
PllC" ,dl.l.nc.
~ e n g t ho l ncraments
Back W.lding
NO!
Inl.rmln.nl
Edp*
L l n p l n 0' l"crsm.nl,
o, leg,
B r k l n g W.ldlng
Symbol
SymW
NO!
"Sod
I
2nd
OOBrltOn
l l l d 0FXI.IO"
Depfn 01 I ~ l i n gn rnchar
!Om,sliOn ndlClle, l~lllngr ComDlelel
"""'
s , : a or
--1-St\ ***
p
p
p
p
"Ud
Not
Suppkmont.ry Symbols
"M
NO,
+--ct\
".ad
NO!
usad
No1
UlDd
NO,
Locallon ol Elements of
Squ~,..Groov~
Wddlng Symbol
Slng1.-V
u
Notw
W M l w SymW
DBPW ol preparalon
Weldlng Symbol
Flnisn 8ymboI
Contour
Dou~~.-B.r.i-Gmor.
W8ld l 8 Z B
S y m b l wlth B l c t g o u ~ l n g
D.pm 01 pr.u.r.lan
Arlo.
YQ. L ,0'"1
Conur Jolnl
Symbd
Fl.~B.wI-Grwv.
W.ldlng
SymW
Fllld Waldrymml
Bade Joinb
Ibmtlllullon 01 Anow Sld. and Olhor Sldo 01 Jolnt
Mm *I
Mulllpl. Rel.rtns.
Lln.8
Cornpl.1.
P.n.lr.llon
SymW
1st OP.,<i110"
0" 18"O
nearest arrow
(Tall omiile0
m a n r.l.rlncs
i l "01 "W!
weld.ell.aro~nd symbol
3rd operntioo
E l e m s n l ~tn In#%
area
rama,n 8,3hO*"
,all end errow .,a
M.ll-Thru
Symbol
join! -4th 8 r l 8 n g
reversed
P"""
01 W"!
1 . ~ 1
Edge Jolnl
R nocater D a c l n p
removed alter roidlng
p
p
p
Jolnt wllh SF
,.
U E R I C A I I WLOINO WClCm, 1%
JIO \I V Llltun. R-d
P O B i l l 111W0 Mi.m#. Fiur@d.lli3!
Flush Contour S y m b l
Conr.x
C o n l w r Symbd
5.1.8
REFERENCE LINE
ARROW
BASIC WELD SYMBOLS
DIMENSIONS & OTHER DATA
SUPPLEMENTARY SYMBOLS
FINISH SYMBOLS
TAl L
SPECIFICATIONS, PROCESS or OTHER REFERENCE
The following is a quick guide t o the scheme. Full details will be found in
the current revision of 'Standard Welding Symbols' available from the
American Welding Society.
ASSEMBLING THE WELDING SYMBOL
Reference line and arrow: The symbol begins with a reference line and arrow
pointing t o the joint where the weld is to be made. The reference line has two
'sides': 'other side' (above the line) and 'arrow side' (below the line)-refer
to the following examples and to chart 5.9.
FIGURE 5.1
Other slde
O
r\A
-
Other side
Other $Id\
Arrow side
Arrow slde
Other side
&
Only the bevel and 'J' groove symbols require a break in the arrow -see
chart 5.9.
'*
"tF
Suppose the weld is required to be 114 inch in size, and the bevel is to be
3/16 inch deep:
r-l
These d~mens~ons
are shown
to the left of the weld symbol
FIGURE
.2,
'w
KVEL
rLAnc.v
FLARE BEVCL
[he symbol
IS
5.1
L
--
--
--
Going back to the example of a simple fillet weld, if the weld is required
all around a member,
Going back t o the fillet weld joint without a bevel, if the weld needs t n
be l/Cinch i n size and 6 inches long, like this:
alternately:
I f this same 'all around' weld has to be made in the field, it is shown thus.
If a series of 6-inch long welds is required with 6.inch gaps between them
(that is, the pitch of the welds is 12 inches), thus:
The contour of the weld is shown by a contour symbol on the weld symbol:
FLUSH CONTOUR
CONVEXCONTOUR
CONCAVECONTOUR
alternately:
likethis:
likethis:
or:
I
If these welds are required staggered on both sides-
like this,
,sM
>
These symbols give instructions for making the weld and define the required
countour:
a t l o ALL
AROUND
llCLDllL0
CONTOUR
YCLl.THRU
FLUSH
CONVEX
COYCAVC
DRAWINGS
5.2
SCHEMATIC DIAGRAM
~
The diagram is not to scale, but relationships between equipment and piping
with regard to the process are shown. The desired spatial arrangement of
equipment and piping may be broadly indicated. Usually, the schematic is
not used after the initial planning stage, but serves to develop the process flow
diagram which then becomes the primary reference.
5.2.1
FLOW DIAGRAM
5.2.3
(2)
(3)
PIPING DRAWING
EXAMPLE DIAGRAMS
LAYOUT OF THE FLOW DIAGRAM
A real or supposed need for industrial or national security may restrict information appearing on drawings. Instead of naming chemicals, indeterminate
or traditional terms such as 'sweet water', 'brine', 'leach acid', 'chemical B',
may be used. Data important t o the reactions such as temperatures, pressures
and flow rates may be withheld. Sometimes certain key drawings are locked
away when not in use.
I651
SOLVENT VAPOR
DIRTY WET S O L V E N T 4
SEDIMENT
SEPARATOR
'
STEAM
SOLVENT
PREHEATER
HEATED SOLVENT
C O O L I N G WATER
RECLAIMED SOLVENT
WATER
SLUDGE
STORAGE TANK
DRAIN
SEPARATOR
SIZE, D U N
EQUIP N O - SOLVENT PREHEATER
SIZE, DUTY
EQUIP N O - - -
STREAM N O
LB/HR
PSlG
SG
DEG F
SOLVENT VAPORIZOR
SIZE, DUTY
EQUIP N O - - -
SOLVENT COOLER
FLOW LINES
Directions of flow within the diagram are shown by solid arrowheads. The
use of arrowheads at all junctions and corners aids the rapid reading of the
diagram. The number of crossings can be minimized b y good arrangement.
Suitable line thicknesses are shown at full size i n chart 5.1. For photographic
reduction, lines should be spaced not closer than 318 inch.
The basic process information required for designing and operating major
items of equipment should be shown. This information is best placed immediately below the title of the equipment.
Process and service streams entering or leaving the flow diagram are shown
by large hollow arrowheads, with the conveyed fluid written over and the
continuation sheet number within the arrowhead, as i n figure 5.3.
IDENTIFYING EQUIPMENT
Also, i t is useful to divide the plant and open part of the site as necessary
into areas, giving each a code number. A n area number can be made the first
part of an equipment number. For example, if a heat exchanger is the 53rd
item of equipment listed under the classification letter 'E', located i n area 'l',
(see 'Key plan' i n 5.2.7) the exchanger's equipment number can be 1-E-53.
Each item of equipment should bear the same number on
grams and listings. Standby or identical equipment, if in
may be identified by adding the letters, A, B, C, and so
equipment identification letter and number. For example,
and its standby may be designated 1-E-53A, and 1-E-530.
ESSENTIAL INSTRUMENTATION
SERVICES ON PROCESS FLOW DIAGRAMS
Systems for providing services should not be shown. However, the type of
service, flow rates, temperatures and pressures should be noted at consumption rates corresponding t o the material balance-usually shown by a 'flag'
t o the line-see figure 5.3.
EQUIPMENT DATA
DISPOSAL OF WASTES
The routes of disposal for all waste streams should be indicated. For example,
arrows or drain symbols may be labelled with destination, such as 'chemical
sewer' or 'drips recovery system'. In some instances the disposal or wastetreatment system may be detailed on one or more separate sheets. See6.13
where 'effluent' is discussed.
MATERIAL BALANCE
5'
7
'
-
2.3
The P&ID should define piping, equipment and instrumentation well enough
for cost estimation and for subsequent design, construction, operation and
modification of the process. Material balance data, flow rates, temperatures,
pressures, etc., and piping fitting details are not shown, and purely mechanical
piping details such as elbows, joints and unions are inappropriate t o P&ID1s.
This type of full designation for a flow line need not be used, provided
identification is adequate.
Piping drawings use the line numbering of the P&ID, and the f o l l o w ~ n g
points apply to piping drawings as well as P&ID's.
INTERCONNECTING P&ID
This drawing shows process and service lines between buildings and units,
etc., and serves to link the P&IDJs for the individual processes, units or
buildings. Like any P&I D, the drawing is not to scale. I t resembles the layout
of the site plan, which enables line sizes and branching points from headers
t o be established, and assists in planning pipeways.
P&ID LAYOUT
The layout of the P&ID should resemble as far as practicable that of the
process flow diagram. The process relationship of equipment should correspond exactly. Often i t is useful t o draw equipment in proportion vertically, but to reduce horizontal dimensions to save space and allow room for
flow lines between equipment. Crowding information is a common drafting
fault - i t is desirable to space generously, as, more often than not, revisions
add information. On an elevational P&ID, a base line indicating grade or
first-floor level can be shown. Critical elevations are noted.
As with the process flow diagram, directions of flow within the drawing are
shown by solid arrows placed at every junction, and all corners except where
changes of direction occur closely together. Corners should be square. The
number of crossings should be kept minimal by good arrangement.
For revision purposes, a P&ID is best made on a drawing sheet having a grid
system-this is a sheet having letters along one border and numbers along the
adjacent border. Thus, references such as 'A6', 'BY, etc., can be given t o an
area where a change has been made. (A grid system is applicable to P&ID's
more complicated than the simple example of figure 5.4.)
FLOW L I N E S O N P&ID's
r
r
Special points for design and operating procedures are noted-such as lines
which need t o be sloped for gravity flow, lines which need careful cleaning
before startup, etc.
The P&ID should show all major equipment and information that is relevant
to the process, such as equipment names, equipment numbers, the sizes,
ratings, capacities, and/or duties of equipment, and instrumentation.
I f the locations of traps are known they are indicated. For example, the trap
required upstream of a pressure-reducing station feeding a steam turbine
should be shown.
'Future' equipment, together with the equipment that will service it, is shown
i n broken outline, and labeled. Blind-flange terminations t o accommodate
future piping should be indicated on headers and branches. 'Future' additions
are usually not anticipated beyond a 5-year period.
Steam traps on steam piping are not otherwise indicated, as these trap positions are determined when making the piping drawings. They can be added
later to the P & l 0 if desired, after the piping drawings have been completed.
Pressure ratings for equipment are noted if the rating is different from the
piping system. A 'typical' note may be used t o describe multiple pieces of
identical equipment i n the same service, but all equipment numbers are
written.
DRIPLEGS
Vents and drains on high and low points of lines respectively, to be used for
hydrostatic testing, are not shown, as they are established on the p i p ~ n g
arrangement drawings. Process vents and drains are shown.
CLOSURES
2.4
W O W INSTRUMENT NUMBERS
ON ALL INSTRUMENTATION
SYMBOLS (REFER TO 6.631
- .
RECLAIMED SOLVENT
FIGURE
5.4
COOLING WATER
DWG NO
STEAM
DWG NO
COOLING WATER
SLUDGE
(DWG
DWG NO
NO
CONDENSATE
SHOW LlNE NUMBER
ON ALL LINES
SEPARATOR
EQUIP NO
SOLVENT PREHEATER
EQUIP NO
SOLVENT VAPORIZER
EQUIP NO
DWG NO)
SOLVENT COOLER
EQUIP NO
EQUIP NO
SOLVENT RETURN PUMP
c n , l l D hln
5.2.5
Show and tag process and service valves with size and identifying num.
ber if applicable. Give pressure rating i f different from line specification
These sheets are tabulated lists of lines and information about them. The
numbers of the lines are usually listed at the right of the sheet. Other
columns list line size, material of construction (using company's specification
code, if there is one), conveyed fluid, pressure, temperature, flow rate, test
pressure, insulation or jacketing (if required), and connected lines (which
will usually be branches).
The sheets are compiled and kept up-to-date by the project group, taking all
the information from the P&lD. Copies are supplied t o the piping group for
reference.
Signal-lead drafting symbols shown in chart 5.1 may be used, and the
ISA scheme for designating instrumentation is described i n 5.5. Details of
instrument piping and conduit are usually shown on separate instrument
installation drawings.
On small projects involving only a few lines line designation sheets may not be
used. I t is useful t o add a note on the P&lD stating the numbers of the last
line and last valve used.
Show all instrumentation on the P&ID, for and including these items:
element or sensor, signal lead, orifice flange assembly, transmitter, controller, vacuum breaker,flame arrestor, level gage, sight glass, flow indicator, relief valve, rupture disc, safety valve. The last three items may be
tagged with set pressure(s) also
5.2.6
(1)
ORTHOGRAPHIC
(2)
PICTORIAL
Figure 5.5 shows how a building would appear in these different views.
ORTHOGRAPHIC
CONTROL STATIONS
FIGURE 5.5
PICTORIAL
Control stations are discussed i n 6.1.4. Control valves are indicated by pressure rating, instrument identifying number and size-see figure 5.15, for example.
P&ID SHOWS HOW WASTES ARE HANDLED
PLAN
Drains, funnels, relief valves and other equipment handling wastes are shown
on the P&ID. I f an extensive system or waste-treatment facility is involved,
i t should be shown on a separate P&lD. Wastes and effluents are discussed
in 6.13.
ELEVATIONS
OBLlOUE
Plan views are more common than elevational views. Piping layout is developed
in plan view, and elevational views and section details are added for clarity
where necessary.
PICTORIAL VIEWS
I n complex piping systems, where orthographic views may not easily illustrate the design, pictorial presentation can be used for clarity. In either
isometric or oblique presentations, lines not horizontal or vertical on the
drawing are usually drawn at 30 degrees t o the horizontal.
UTILITY STATIONS
Stations providing steam, compressed air, and water, are shown. Refer t o
6.1.5.
[701
Figure 5.6 illustrates how circular shapes viewed at different angles are approximated by means of a 35-degree ellipse template. Isometric templates
for valves, etc., are available and neat drawings can be rapidly produced with
them. Orthographic and isometric templates can be used t o produce an
oblique presentation.
ISOMETRIC PRESENTATION
OF CIRCULAR SECTIONS
FIGURE 5.6
5.2.7
The piping group produces a 'site plan' to a small scale ( 1 inch to 3 0 or 100ft
for example). I t shows the whole site including the boundaries, roads,
railroad spurs, pavement, buildings, process plant areas, large structures, storage areas, effluent ponds, waste disposal, shipping and loading areas. 'True'
(geographic) and 'assumed' or 'plant' north are marked and their angular
separation shown-see figure 5.1 1.
PIPING ARRANGEMENT I N DIFFERENT PRESENTATIONS
I
FIGURE 5.7
L
#q==
PLAN
FIGURES ; 5.5-5.7
ISOMETRIC
OBLIQUE
KEY PLAN
A 'key plan' is produced by adapting the site plan, dividing the area of the
site into smaller areas identified by key letters or numbers. A small simplified
inset of the key plan is added t o plot plans, and may be added t o piping and
other drawings for reference purposes. The subject area of the particular
drawing is hatched or shaded, as shown i n figure 5.8.
DRAWING SHEET SHOWING KEY PLAN 5 MATCHLINE
FIGURE 5.8
VESSEL DRAWINGS
When the equipment arrangement has been approved and the piping arrangement determined, small dimensioned drawings of process vessels are made
(on sheets 8% x 11 or 11 x 17 inches) i n order t o fix nozzles and their
orientations, manholes, ladders, etc. These drawings are then sent t o the
vendor who makes the shop detail drawings, which are examined by the
project engineer and sent t o the piping group for checking and approval.
Vessel drawings need not be t o scale. (Figure 5.14 is an example vessel
drawing.)
DRAWINGS FROM OTHER SOURCES
Piping drawings should be correlated with the following drawings from other
design groups and from vendors. Points t o be checked are listed:
MATCHLINE AREA '3'
DWG No.
............
Under project group supervision, the piping group usually makes several
viable arrangements of equipment, seeking an opt~maldesign that satisfies
process requirements. Often, preliminary piping studies are necessary i n order
t o establish equipment coordinates.
When the equipment arrangement drawings are approved, they are developed
into 'plot plans' by the addition of dimensions and coordinates t o locate
all major items of equipment and structures.
North and east coordinates of the extremities of buildings, and centerlines of
steelwork or other architectural constructions should be shown on the plot
plan, preferably at the west and south ends of the installation. Both 'plant
north' and true north should be shown-see figure 5.1 I .
Architectural drawings:
Outlines of walls or sidings, indicating thickness
r
m
Floor penetrations for stairways, lifts, elevators, ducts, drains, etc.
r
Positions of doors and windows
Civil engineering drawings:
Foundations, underground piping, drains, etc
m
Structural-steel drawings:
Positions of steel columns supporting next higher floor level
r
Supporting structures such as overhead cranes, monorails, platforms
r
or beams
I
Wall bracing, where pipes may be taken thru walls
Heating, ventilating & air-conditioning (H VAC) drawings:
Paths of ducting and rising ducts, fan room, plenums, space heaters, etc.
r
Electrical drawings:
Positions of motor control centers, switchgear, junction boxes and
r
control panels
m
Major conduit or wiring runs (including buried runs)
r
Positions of lights
instrumentation drawings:
r
Vendors' drawings:
r
Dimensions of equipment
Positions of nozzles, flange type and pressure rating, instruments, etc.
8
Mechanical drawings:
Positions and dimensions of mechanical equipment such as conveyors,
m
chutes, etc.
r
Piped services needed for mechanical equipment.
5.2.8
PIPING DRAWINGS
Process equipment and piping systems have priority. Drawings listed on the
preceding page must be reviewed for compatibility with the developing piping
design.
Pertinent background details (drawn faintly) from these drawings help t o
avoid interferences. Omission of such detail from the piping drawing often
leads t o the subsequent discovery that pipe has been routed thru a brace,
stairway, doorway, foundation, duct, mechanical equipment, motor control
center, fire-fighting equipment, etc.
Completed piping drawings will also show spool numbers, i f this part
of the job is not subcontracted - see 5.2.9. Electrical and instrument
cables are not shown on piping drawings, but trays t o hold the cables are
indicated-for example, see figure 6.3, point (8).
I t is not always possible for the piping drawing to follow exactly the logical
arrangement of the P&ID. Sometimes lines must be routed with different
junction sequence, and line numbers may be changed. During the preliminary
piping studies, economiesand practicable improvementsmay be found, and the
P&ID may be modified t o take these into account. However, i t is not the
piping designer's job t o seek ways t o change the P&IO.
On drawrngs show~nga plan vlew, place a north arrow at the top left
corner of the sheet to lndlcate plant north-see f~gure5 11
Do not draw i n the area above the title block, as this space is allocated
t o the bill of materiel, or to general notes, brief descriptions of changes,
and the titles and numbers of reference drawings
I f plans and elevations are small enough t o go on the same sheet, draw
the plan at the upper left side of the sheet and elevations t o the right
and bottom of it, as shown in figure 5.9
BACKGROUND DETAIL
SCALE
Take line numbers from the P&lD. Refer t o 5.2.4 under 'Flow lines on
P&ID1s' for information on numbering lines. Include line numbers on
all views, and arrowheads showing direction of flow
Draw all pipe 'single line' unless special instruct~onshave been given
for drawing 'double line'. Chart 5.1 gives line thicknesses (full size)
Obtain the drawing number and fill in the title block at the bottom
right corner of the sheet
FIGURE 5.9
I
I
Y 1
r'
u '
Y '
21
------ ----, , - - - - - - - - - I
1
2'
I
1
'
PLAN
-
X I
1
I
k--+
LINE NUMBER
drmlopl.
I
I
1
I
I
FIGURES
ELEVATION
I
I
I
I
1I 1
I
/1 /L- -- - - - - J
:,I
- - - -- - - - - - - - -1
L-------------J
I
I
1
I
I
I
I
-
5: : :1
V A L V E , etc.
ELEVATION
I f pipe sleeves are required thru floors, ~ndicatewhere they are needed
and inform the group leader for transmitting this information t o the
group(s) concerned
Indicate insulation, and show whether lines are electrically or steam
traced-see chart 5.7
The following items should be labeled in one view only: tees and ells
rolled at 45 degrees (see example, this page), short-radius ell, reducing
ell, eccentric reducer and eccentric swage (note on plan views whether
'top flat' or 'bottom flat'), concentric reducer, concentric swage,
non-standard or companion flange, reducing tee, special items of
unusual material, of pressure rating different from that of the system,
etc. Refer t o charts 5.3, 5.4 and 5.5 for symbol usage
Label control valves to show: size, pressure rating, dimension over flanges, and valve instrument number, from the P&ID -see figure 5.15
Draw plan views for each floor of the plant. These views should show
what the layout will look like between adjacent floors, viewed from
above, or at the elevation thru which the plan view is cut
I f the plan view will not f i t on one sheet, present i t on two or more
sheets, using matchlines t o link the drawings. See figure 5.8
'ROLLED' ELL
'ROLLED' TEE
ROLL ELL
AT 45'
ROLL TEE
A T 45'
Driplegs are indicated on relevant piping drawing plan views. Unless identical,
a separate detail is drawn for each dripleg. The trap is indicated on the dripleg piping b y a symbol, and referred t o a separate trap detail or data sheet.
The trap detail drawing should show all necessary valves, strainers, unions,
etc., required at the trap-see figures 6.43 and 6.44.
Figure 5.10 shows how lines can be broken t o give sufficient information
without drawing other views
The piping shown on the dripleg details should indicate whether condensate
is to be taken to a header for re-use, or run t o waste. The design notes i n
6.10.5 discuss dripleg details for steam lines i n which condensate forms
continuouslv. Refer t o 6.10.9 also.
Draw t o a large scale any part needing fuller detail. Enlarged details
are preferably drawn i n available space on elevational drawings, and
should be cross-referenced by the applicable detail and drawing number(~)
Identify sections indicated on plan views by letters (see chart 5.8) and
details by numbers. Letters I and 0 are not used as this can lead to confusion w i t h numerals. If more than twentyfour sections are needed
the letter identification can be broken down thus: A l - A l , A2-A2,
84-04, ....... and so on
Do not section plan views looking toward the bottbm of the drawing sheet
SPOOL FABRICATION
FABRICATION F R O M DRAWINGS
FIGURE 5.10
IOPTIONAILY-
ENGINEERING
FABRICATED
IPIPINC CONTRACTORI
ENGINEERING
r o a FABRICATION
DESIGN OFFICE
P L A N
1108 SllEl
IPlPlNC CONTRACTORI
(or ELEVATION)
Corresponding E L E V A T
I 0 N (or PLAN)
& 'SPOOLS'
5.2.9
The prefabricated parts of the piping system are termed 'spools', described
under 'Spools', this section. The piping group either produces isos showing
the required spools, or marks the piping to be spooled on plans and elevations,
depending on whether or not a model is used (as shown i n chart 5.10).
From these drawings, the subcontractor makes detail drawings termed
'spool sheets'. Figure 5.17 is an example spool sheet.
f751
CHART
5.1 0
Shop and field welds. Indicate limits of shop and field fabrication
(1)
(2)
Lists the cut lengths of pipe, fittings and flanges, etc. needed to make
the spool
(3)
Materials of construction
(4)
Spool numbers are allocated by the piping group, and appear on all
piping drawings. Various methods of numbering can be used as long as
identification is easily made. A suggested method follows:-
Iso sheets can be identified b y the line number of the section of line that is
shown, followed by a sequential number. For example, the fourth iso sheet
showing a spool to be part of a line numbered 74/BZ/6/412/23 could be
identified: 74/BZ/6/412/23-4 .
Both the spool and the spool sheet can be identified by number or letter
using the iso sheet number as a prefix. For example, the numbering of
spool sheets relating t o iso sheet 74/BZ/6/412/23-4 could be
or
74/BZ/6/412/23-4-1,
74/82/6141 2123-4-2,
74/82/6/412/23-4-A,
74/BZ/6/412/23-4-0,
........ etc.,
........ etc.
The size of a spool is limited by the fabricator's available means of transportation, and a spool is usually contained within a space of dimensions
40 f t x 10 f t x 8 ft. The maximum permissible dimensions may be obtained
from the fabricator.
The full line number need not be used if a shorter form would suffice for
identification.
FIELD-FABRICATED SPOOLS
(1)
(2)
(3)
Spool numbers are also referred to as 'mark numbers'. They are shown on
isos and on the following:-
Some States in the USA have a trades agreement that 2-inch and smaller
carbon-steel piping must be fabricated at the site. This rule is sometimes
extended t o piping larger than 2-inch.
DIMENSIONING
SHOP-FABRICATED SPOOLS
DIMENSIONING FROM REFERENCE POINTS
All alloy spools, and spools with 3 or more welds made from 3-inch (occasionally 4-inch) and larger carbon-steel pipe are normally 'shop-fabricated'. This
is, fabricated i n the shop fabricator's workshop, either at his plant or at
the site. Spools with fewer welds are usually made in the field.
HORIZONTAL REFERENCE
The lines of latitude and longitude which define the geographic reference
point are not used, as a 'plant north' (see figure 5.1 1 ) is established, parallel
t o structural steelwork. The direction closest t o true north is chosen for
the 'plant north'.
SPOOL SHEETS
VERTICAL REFERENCE
Before any building or erecting begins, the site is leveled ('graded') with
earth-moving equipment. The ground is made as flat as practicable, and aftel
leveling is termed 'finished grade'.
The highest graded point is termed the 'high point of finished grade',
(HPFG), and the horizontal plane passing thru i t is made the vertical reference
plane or 'datum' from which plant elevations are given. Figure 5.12 shows
that this horizontal plane is given a 'false' or nominal elevation, usually 100 ft,
and is not referred to mean sea level.
Coordinates are used t o locate tanks, vessels, major equipment and structural
steel. I n the open, these items are located directly with respect t o a geographic reference point, but i n buildings and structures,'can be dimensioned
from the building steel.
FIGURE 5.11
HORIZONTAL REFERENCE
Large plants may have several areas, each having its own high point of
finished grade. Nominal grade elevation is measured from a benchmark, as
illustrated in figure 5.12.
FIGURE 5.12
VERTICAL REFERENCE
H I G H POINT OF F I N I S H E D GRADE
E L E V A T I O N SET A T 1W. N O M I N A L
IEOUALS 811'-7" TRUE DATUM1
1 I
/-
ELEVATION OF EOUIPMENT
CENTERLINE STATED AS
105'-4". OR 5 - 4 " ABOVE HPFG
I
!
GEOGRAPHIC
REFERENCE POINT
IMONUMENTI
The US Department of Commerce's Coast and Geodetic Survey has established a large number of references for latitude and longitude, and for
elevations above sea level. These are termed 'geodetic control stations'.
5.3.2
Control stations for horizontal reference (latitude and longitude) are referred
to as 'triangulation stations' or 'traverse stations', etc. Control stations for
vertical reference are referred to as 'benchmarks'. Latitude and longitude
have not been established for all benchmarks.
Offplot:
The geographic positions of these stations can be obtained from the Director,
US Coast and Geodetic Survey, Rockville, Maryland 20852.
1771
FIGURES
V t H 1 ICAL VItVV
t L t v lu
~ l u~a a
ultvlctuatutra
DIMENSION
VESSELS
LErPp"MENT
LINES
LINES
STANDARD V A L V E S
CENTERLINE TO CENTERLINE
NOZZLESON
NON-STANDARD
VESSELS
PUMPS
EQUIPMENT
VALVES
I EyF,"tNT
INSTRUMENTS
REFERENCE L I N E C A N BE EITHER A N O R D I N A T E I L l N E OF L A T I T U D E
OR LONGITUDE1 OR A C E N T E R L I N E OF B U I L D I N G STEEL
Plan views convey most of the dimensional information, and may also show
dimensions for elevations in the absence of an elevational view or section.
EXAMPLE DIMENSIONS FOR PLAN VlEW
FIGURE 5.13
MISCELLANEOUS ELEVATIONS
FINISHED FLOOR,
SHOW ELEVATION OF HIGH POINT
OF FLOOR
A
FOUNDATION. SHOW 'TOP OF CONCRETE'.
INCLUDING GROUT
TOC EL
VERTICAL NOZZLE
SHOW ELEVATION OF FLANGE FACE
B=
INSTRUMENT POINT SHOW ELEVATION OF
CONNECTION CENTERLINE, or DIMENSION
FROM NEAREST RELEVANT ELEVATION
. . _ . . ..., ,_ . .. . " . ; .
- . 7 E EL
, ,.. .
. . " . ' . : : . ..'.
, ,
, , ,
",I'
EL
r
r
Draw dimension lines unbroken with a fine line. Write the dimension
just above a horizontal line. Write the dimension of a vertical line
sideways, preferably at the left. I t is usual t o terminate the line with
arrowheads, and these are preferable for isos. The oblique dashes shown
are quicker and are suitable for plans and elevations, especially i f the
dimer~sionsare cramped
DIMENSION
5.3.3
- do not
8
1I
.3.3
LL-
u
I
Dimensions under two feet are usually marked i n inches, and those
over t w o feet i n feet and inches. Some companies prefer t o mark all
dimensions over one foot in feet and inches
Attempt t o round off non-critical dimensions t o whole feet and inches.
Reserve fractions of inches for dimensions requiring this precision
DIMENSION
n
, -.3,2
I f a certain piping arrangement is repeated on the same drawing, i t is sufficient t o dimension the piping in one instance and note the other
appearances as 'TYP' (typical). This situation occurs where similar
pumps are connected t o a common header. For another example, see
the pump base i n figure 6.1 7
Do not duplicate dimensions. Do not repeat them in different views
r
I
DIMENSIONING TO JOINTS
DIM
DIM
DIM
DIM
T
r
--
FIGURE
5.1 3
DIM
I-
-.
DIM
DIM
DIM
I791
TABLE
5.2
FITTING MAKEUP
I f a number of items of standard dimensions are grouped together it is unnecessary to dimension each item, as the fabricator knows the sizes of stand.
ard fittings and equipment. I t is necessary, however, to indicate that the
overall dimension is 'fitting makeup' by the special cross symbol, or
preferably by writing the overall dimension. Any non-standard item inserted
between standard items should be dimensioned.
F I G U R E 5.14
CENTERLINE ILEVATIOW
MAY Bf DlVEN ?OR DESIGN
OFFICE REFEREWE
TANGENT LINE
9
.
DIM or
j)C
TANGENT L I N E
DIMENSIONING TO VALVES
8
ELEVATION
SPACED. FROM
SCH 40 PIPE
DIMENSIONING ISOS
5.3.4
FACES OF FLANGED NOZZLES SHALL
In order to clearly show all dimensions, the best aspect of the piping must
be determined. Freedom to extend linesand spread the piping without regard
to scale is a great help in showing isometric dimensions. The basic dimensions
set out in 5.3.2, 5.3.3, and the guidelines in 5.2.9 apply.
NOZZLE LISTING
Figure 5.15 illustrates the main requirements of an isometric drawing, and inincludes a dimensioned offset. Figure 5.16 shows how other offsets are dimensioned.
8
8
ENCINEERIAVC
CO.WlYAS Y
T I T L E BLOCK
/a01
FIGURE 5.16
5.3.5
-4
COMPOUND OFFSET
I
r'
FIGURE 5.17
1)
G
SPECIFICATION:&
NUMBER R E Q U I R E D . ~
E N G I N E E R I N G CO.
5.4.4
P&ID's, process flow diagrams and line designation sheets are checked by
engineers in the project group.
Title of drawing
Except for spool drawings, all piping drawings are checked b y the piping group.
Orthographic spool drawings produced by the piping fabricator are not usually
checked by the piping group, except for 'critical' spools, such as spools for
overseas shipment and intricate spools.
Usually an experienced designer within the piping group is given the task
of checking. Some companies employ persons specifically as design checkers.
The checker's res~onsibilitiesare set out i n 4.1.2.
r
a
8
Prints of drawings are checked and corrected b y marking with colored pencils.
Areas t o be corrected on the drawing are usually marked i n red on the print.
Correct areas and dimensions are usually marked i n yellow.
r
a
Checked drawings to be changed should be returned t o their originator whenever possible, for amendment. A new print is supplied t o the checker with
the original 'marked up' print for 'backchecking'.
Provision of line vents, drains, traps, and tracing. Check that vents are
at all high points and drains at all low points of lines for hydrostatic
test. Driplegs should be indicated and deta~led.Traps should be identi.
fied, and piping detailed
The following items should be labeled i n one view only: tees and ells
rolled at 45 degrees (see example in 5.2.8), short-radius ell, reducing
ell, eccentric reducer and eccentric swage (note on plan views whether
'top flat' or 'bottom flat'), concentric reducer, concentric swage,
non-standard or companion flange, reducing tee, special items of
unusual material, of pressure rating different from that of the system,
etc. Refer to charts 5.3, 5.4 and 5.5 for symbol usage
ISSUING DRAWINGS
5.4.3
..,L
That the drawing includes reference number(s) and title(s) to any other
relevant drawings
That all dimensions are correct
Agreement with certified vendors' drawings for dimensions, nozzle
orientation, manholes and ladders
That face-to-face dimensions and pressure ratings are shown for all
non-standard flanged items
5.4.2
5 ::::
my
Correctness of scale
Possible interferences
FIGURES
INSTRUMENT FUNCTIONS
Accessibility for operation and maintenance, and that adequate manholes, hatches, covers, dropout and handling areas, etc. have been
provided
Although instruments are used for many purposes, their basic funct~onsare
few in number:
r
0
0
0
(2)
(3)
(4)
5.5
This section briefly describes the purposes of instruments and explains how
instrumentation may be read from P&ID's. Piping drawings will also show
the connection (coupling, etc.) to line or vessel. However, piping drawings
should show only instruments connected to (or located in) piping and vessels.
The only purpose i n adding instrumentation to a piping drawing is to identify
the connection, orifice plate or equipment to be installed on or in the piping,
and to correlate the piping drawing to the P&ID.
INSTRUMENT FUNCTION ONLY IS SHOWN
(1)
5.5.2
5.5.3
5.5.1
FIGURE 5.18
INSTRUMENT
There is some uniformity, among the larger companies at least, in the way in
which instrumentation is shown. There is a willingness t o adopt the recommendations of the Instrument Society of America, but adherence is not always
complete. The ISA standard is S5.1, titled 'Instrumentation symbols and identification'.
'LOOP' NUMBER----
'
iI%"~~f#l,F!CA
l/O&
In figure 5.18, 'P', 'TI, and 'F'denote process variables pressure, temperature,
and flow respectively. 'I' and 'G' show the type of instrument; indicator
and gage respectively. Table 5.3 gives other letters denoting process variable,
type of instrument, etc. The number '8', labeled 'loop number', is an example
sequential number (allocated by an instrumentation engineer).
Compliance with the ISAscheme is to some extent international. This is beneficial when drawings go from one country t o another, as there is then no difficulty i n understanding the instrumentation.
[a41
5.5.4
INSTRUMENT MOUNTING,
5.5.6
SIGNAL LEADS
A horizontal line in the ISA balloon shows that the instrument performing
the function is to be 'board mounted' in a console, etc. Absence of this line
shows 'local mounting', in or near the piping, vessel, etc.
BOARD MOUNTING
LOCAL MOUNTING
INTERCONNECTED I N S T R U M E N T S ('LOOPS')
The ISA standard uses the term 'loop' to describe an interconnected group
of instruments, which is not necessarily a closed-loop arrangement: that is,
~nstrumentationused in a feedback (or feedforward) arrangement.
I f several instruments are interconnected, they may be all allocated the same
number for 'loop' identificat~on.Figure 5.19 shows a process line served by
one group of Instruments (loop number 73) to sense, transmit and ~ndicate
temperature, and a second group (loop number 74) to sense, transmit, indicate, record and control flow rate.
EXAMPLE INSTRUMENT 'LOOPS'
FIGURE 5.19
ANALYSIS.. . . . . . . . . . . . . . . . . . A
BURNER (Flame) . . . . . . . . . . . . . B
COMBUSTION.. . . . . . . . . . . . . . . B
USER'S CHOICE . . . . . . . . . . . . . . C
USER'S CHOICE . . . . . . . . . . . . . . D
VOLTAGE . . . . . . . . . . . . . . . . . . .E
FLOW RATE . . . . . . . . , . . . . . . . . F
USER'S CHOICE . . . . . . . . . . . . . . G
CURRENT (Electric) . . . . . . . . . . . I
POWER . . . . . . . . . . . . . . . . . . . . . J
TIME (Time Control/Clock) . . . . . . K
LEVEL.. . . . . . . . . . . . . . . . . . . . . L
USER'S CHOICE . . . . . . . . . . . . . . M
USER'S CHOICE . . . . . . . . . , . . . . N
USER'S CHOICE . . . . . . . . . . . . . . 0
PRESSUREIVACUUM . . . . . . . . . . P
RADIATION . . . . . . . . . . . . . . . . . R
SPEED (or Frequency). . . . . . . . . . S
TEMPERATURE . . . . . . . . . . . . . . T
MULTIVARIABLE . . . . . . . . . . . . U
VIBRATION . . . . . . . . . . . . . . . . . V
WEIGHT (or Force) . . . . . . . . . . . . W
UNCLASSIFIED . . . . . . . . . . . . . . X
EVENT (Response to) . . . . . . . . . . Y
POSITION, DIMENSION.. . . . . . . Z
signal-lead
Symbols, refer
to
chart
TYPE OF INSTRUMENT
ALARM . . . . . . . . . . . . . . . . . . .
.. A
USER'S CHOICE . . . . . . . . . . . . . . . B
CONTROLLER . . . . . . . . . . . . . . . . C
CONTROL VALVE . . . . . . . . . . . CV
TRAP . . . . . . . . . . . . . . . . . . . . . . CV
SENSOR (Primary Element) . . . . . . E
RUPTURE DISC . . . . . . . . . . . . . . . E
SIGHT or GAGE GLASS . . . . . . . . . G
TELEVISION MONITOR . . . . . . . . G
INDICATOR . . . . . . . . . . . . . . . . . I
CONTROL STATION . . . . . . . . . . . K
LIGHT (Pilot/Operation) . . . . . . . . . L
USER'S CHOICE . . . . . . . . . . . . . . . N
FLOW RESTRICTION ORIFICE . . . 0
TEST POINT (Sample Point) . . . . . . P
RECORDER . . . . . . . . . . . . . . . . . . R
SWITCH . . . . . . . . . . . . . . . . . . . . . . S
TRANSMITTER . . . . . . . . . . . . . . . T
MULTIFUNCTION . . . . . . . . . . . . . U
VALVEIDAMPER . . . . . . . . . . . . . . V
W E L L . . . . . . . . . . . . . . . . . . . . . . . .W
UNCLASSIFIED . . . . . . . . . . . . . . X
RELAY . . . . . . . . . . . . . . . . . . ..
.. Y
DRIVER . . . . . . . . . . . . . . . . . . . . . Z
ACTUATOR . . . . . . . . . . . . . . . . . . Z
'For
PROCESS VARIABLE
TABLE 6.3
TOTAL
. . . . . .
RATIO
. . . . . .
. . . S
5.1
SAFETY ITEM
'HAND'
. . . . . .
. . . . . . .
. .
. . . . . . .
INTERMEDIATE.
LOW
TABLE
5.3
5.6
L I S T I N G PIPING M A T E R I E L O N D R A W I N G S
5.6.1
ITEM NUMBER
QUANTITY
DEXRlPTlON
REMARK'
NUMBER'
OR COMPANY CODE
5.6.3
Under the heading DESCRIPTION, often on drawings the size of the item is
stated first. A typical order is: SIZE (NPS), RATING (class, schedule number.
etc.), NAME (of item), MATERIAL (ASTM or other material spec~fication),
and FEATURE (design feature).
Descriptions are best headed b y t h e NAME of the item, followed by the SIZE,
RATING, FEATURE(S), and MATERIAL. As material listings are commonly
handled b y data-processing equipment, beginning the description of an item
by name is of assistance i n handling the data. The description for 'pipe' is
detailed.
EXAMPLE LISTING FOR PIPE
I
NAME:
State 'PIPE'
SIZE:
RATING:
FEATURE:
5.6.2
Haphazard listing of items makes reference troublesome. The scheme suggested in chart 5.1 1 is based on the duty of the hardware and can be extended
to listing equipment i f desired. Items of higher pressure rating and larger size
can be listed first within each class.
Pipe is available seamless or with a welded seamexamples of designations are: SMLS = seamless, FBW =
furnace-butt-welded, ERW = electric-resistance-welded
GALV = galvanized. Specify ends: T&C = threaded and
coupled, BE = beveled end, PE = plain end.
CHART 5.11
5.6.4
See that all items in the list have been given a sequential item number
Label the items appearing on the piping drawings with the item number
from the list. Write the item number in a circle with a fine line or arrow
pointing to the item an the drawing. Each item in the list of materiel is
indicated in this way once on the plan or elevational piping drawings
---
- -
--
6.1
Avoid burying steam lines that pocket, due t o the difficulty of collecting condensate. Steam lines may be run below grade in trenches
provided with covers or (for short runs) in sleeves
Lines that are usually buried include drains and lines bringing in water
or gas. Where long cold winters freeze the soil, burying lines below
the frost line may avoid the freezing of water and solutions, saving
the expense of tracing long horizontal parts of the lines
6.1.1
Simple arrangements and short lines minimize pressure drops and lower
pumping costs.
Take gas and vapor branch lines from tops of headers where it is
necessary to reduce the chance of drawing off condensate (if present)
or sediment which may damage rotating equipment
Vent all high points and drain all low points on lines - see figure 6.47.
Indicate vents and drains using symbols in chart 5.7. Carefully-placed
drains and valved vents permit lines to be easily drained or purged
during shutdown periods: this isespecially important in freezing climates
and can reduce winterizing costs
Outside buildings, piping can be arranged: (1) On piperacks. (2) Near grade
on sleepers. (3) In trenches. (4) Vertically against steelwork or large items
of equipment.
PIPING ARRANGEMENT
Do not run piping under foundations. (Pipes may be run under grade
beams)
a
a
a
1871
ti:;.,
--
CHART5.1 1
L
Route piping to obtain adequate clearance for maintaining and removing equipment
Locate within reach, or make accessible, all equipment subject t o periodic operation or inspection - with special reference t o check valves,
pressure relief valves, traps, strainers and instruments
Take care to not obstruct access ways
ways, walkways, lifting wells, etc.
Position equipment with adequate clearance for operation and maintenance. Clearances often adopted are given i n table 6.1. I n some
circumstances, these clearances may be inadequate-for example, with
shell-and-tube heat exchangers, space must be provided to permit
withdrawal of the tubes from the shell
MINIMUM CLEARANCES
HORIZONTAL Operating space around equipment t
CLEARANCES: Centerline of railroad to nearest
obstruction: (1) Straight track
(2) Curved track
Manhole to railing or obstruction
Over walkmy, platform, or operating area
VERTICAL
CLEARANCES: Over rbirway
Over high point of plant roadway:
(1) Minor roadway
(2) Major roadway
Over railroad from top of rail
MINIMUM HORIZONTAL DIMENSIONS
Width of mlkwcy ct floor Iwsl
Width of alwabd walkway or stairway
Width of rung of fixed ladder See charrP-2.
Width of m y for forklift truck
VERTICAL DIMENSIONS
Railing. Top of floor, platform, or stair, to: (1) Lower rail
(2) Upper rail
Manhola centerline to floor
Valvn:
See table 6.2 and chart P-2.
tEqu#pm.nt
2h
6in.
Eft
Bft
3ft
6ft
7ft
6in.
6in.
Oin.
6in.
Oin.
17ft
20ft
22ft
Oin.
Oin.
6in.
Keep field welds and other joints at least 3 inches from supporting
steel, building siding or other obstruction. Allow room for the joint
to be made
Allow room for loops and other pipe arrangements to cope with expansion b y early consultation with staff concerned with pipe stressing.
Notify the structural group of any additional steel required to support
such loops
THERMAL MOVEMENT
Maximum and minimum lengths of a pipe run will correspond to the temperature extremes t o which i t is subjected. The amount of expansion or shrinkage
in steel per degree change in temperature ('coefficient of expansion') is approximately the same - that is, the expansion from 40F to 41 F is about the
same as from 132 F to 133 F, or from 179 F to 180 F , etc. Chart 6.1 gives
changes i n line length for changes in temperature.
6.1,
3ft
2ft
Oin.
6in.
16in.
8 h Oin.
l h Bin.
3ft Sin.
3ft Oin.
such r heel exchanQan cornpraron end turbines wlll require nddlt~onal clearance.
panlcular r p r a requlrernenls. Refer to flpure 6.33
C h r k rnenulr1ur.n' d r m t n p l o d;lermin.
and 1.ble 6.5 lor lprlne heat 1 x c h ~ 0 . 1 1 .
Ensure very hot lines are not run adjacent to lines carrying temperature
sensitive fluids, or elsewhere, where heat might be undesirable
CHART 6.1
STRESSES ON PIPING
THERMAL STRESSES
In w n m t p r t i a , II-
support
1 - }
+- - - 4
+4
fi +
may settle or tilt slightly i n the course of time. Connected piping and equipment not on a common foundation will be stressed by the displacement unless
the piping is arranged in a configuration flexible enough to accommodate
multiple-plane movement. This problem should not arise in new construction
but could occur in a modification to a plant unit or process.
FLEXIBILITY IN PIPING
I
O f f w n l q ma run ~ l v llaxib~l~ty
n
whsh l n c r s n a
w ~ t htho Iaqth of ma offmt
COLD SPRINGING
~i
b w n the unm
( a ) TO REDUCE STRESS
HOT POSITION
COLD SPRING
Tha extra lhmb in the morm flerlbl.
arranpsmsnt
( b ) TO A V O I D A N INTERFERENCE
A---
COLD POSITION
COLD LINE-
COLD LINE
HOT LlNE
-----I+-COLD SRllNG
4
f
Anchored end
'CHART
'
6.1
In t h e
o n heating expand
so
usually
nozzle may
t h a t 11 imposes a l o a d o n t h e n o z z l e I n excess
of
and
a
t h r u it, p u t t i n g
If
inch. I t
or
p r o v ~ d ~ nagd d i t i o n a l s u p p o r t
flows
give
stress
a n d s u p p o r t data
for
spans
of
horizontal
P'PC
the o
, io
, e had
t e m p e r a t u r e lateral
and the
hot
KEY F O R F I G U R E 6.3
c o l d s p r i n g of 50%
the most benefit in
r e d u c i n g stress. C o l d s p r i n g i n g is n o t r e c o m m e n d e d i f an a l t e r n a t e s o l u t i o n
can be used. Refer to t h e Code f o r Pressure P i p i n g ANSI 031 and to table7.2.
The
of
2 - ~ n c hp l p e ,
that
r e c o m m e n d e d A s s u m e t h a t p l p i n q t o t h e n o z z l e has b e e n ~ n s t a l l e dat a m b ~ e n t
temperature,
a p ~ p e r a c kw ~ t h o u t a d d t i o r i e l s i i p p o r r I S
may be m o r e e c o n o m i c t o change p r o p o s e d small I n e s t o
to suspend t h e m f r o m 4 - ~ n c h o r larger lines, ~ n s t e a d o f
T h e smallest size of p i p e r u n o n
f o l l u w l n q i:xample, ~ u l sdp r l n i.
j l n q.I S e m p l o y e d s o l e l y t o r e d u c e a stress
l o n g p l p e c o n n e c t e d b y a 90-degree e l b o w a n d f l a n g e t o a
the expansion
between
can be
varied.
t h e t e m p e r a t u r e e x t r e m e s gives
12) 0 0 NOT RUN PIPING OVER STANCHIONS AS THlS WlLL PREVENT ADDING
ANOTHER DECK
(31 PLACE LARGE LIQUID-FILLED PlPES NEAR STANCHIONS TO REDUCE STRESS
ON HORIZONTAL MEMBERS OF BENTS. HEAVY LIQUID-FILLED PlPES 112.1n
A N 0 LARGER) ARE MORE ECONOMICALLY RUN AT GRADE-SEE NOTE 1121
All
piping
Table F.11 gives pressure drops for water f l o w i n g thru SCH 40 pipe at
various rates. Charts t o determine the economic size ( N P S ) o f p i p i n g are
given in the Chemical Engineer's Handbook and o t h e r sources.
PIPERACKS
6.1.2
(13) CURRENT PRACTICE IS TO SPACE BENTS 20-25 FEET APART. THlS SPACING
IS A COMPROMISE BETWEEN THE ACCEPTABLE DEFLECTIONS OF THE
SMALLER PlPES A N 0 THE MOST ECONOMIC BEAM SECTION DESIRED FOR
THE PIPERACK. PIPERACKS ARE USUALLY NOT OVER 25 FEET IN WIDTH.
IF MORE ROOM IS NEEDED, THE PIPERACK IS DOUBLE. OR TRIPLE.DECKED
'tee-head s u p p o r t s ' .
(151 WHEN SETTING ELEVATIONS FOR THE PIPERACK TRY TO AVOID POCKETS
IN THE PIPING. LINES SHOULD BE ABLE TO DRAIN INTO EQUIPMENT OR
LINES THAT CAN BE DRAINED
Piperacks are expensive, but are necessary for a r r a n g i n g the main process and
service lines around t h e p l a n t s i t e . They are made use of in secondary ways,
principally t o p r o v i d e a p r o t e c t e d location for ancillary e q u i p m e n t .
(161 GROUP HOT LINES REQUIRING EXPANSION LOOPS AT ONE SIDE OF THE
PIPERACK FOR EASE OF SUPPORT-SEE FIGURE 6.1
(171 LOCATE UTILITY STATIONS, CONTROL (VALVE) STATIONS. AND FIREHOSE
POINTS ADJACENT TO STANCHIONS FOR SUPPORTING
(18) LEAVE SPACE FOR DOWNCOMERS TO PUMPS, Etc.. BETWEEN PIPERACK AND
ADJACENT BUILDING OR STRUCTURE
1901
(FIGURE
6.3
V A L V E OPERATING HEIGHTS
TABLE 6.2
(1)
(2)
Nearly all valves will be line size - one exception is control valves, which are
usually one or two sizes smaller than line size; never larger.
A t control stations and pumps i t has been almost traditional to use line-size
isolating valves. However, some companies are now using isolating valves at
control stations the same size as the control valve, and at pumps are using
'pump size' isolating valves at suction and discharge. The choice is usually
an economic one made by a project engineer.
a
8
The sizes of bypass valves for control stations are given in 6.1.4, under
'Control (valve) stations'.
See 6.3.1 for valving pumps, under 'Pump emplacement & connections'.
Preferably, place valves in lines from headers (on piperacks) in horizona
tal rather than vertical runs, so that lines can drain when the valves are
closed. (In cold climates, water held in lines may freeze and rupture the
piping: such lines should be traced - see 6.8.2)
To avoid spooling unnecessary lengths of pipe, mount valves directly
a
onto flanged equipment, if the flange is correctly pressure-rated. See
6.5.1 under 'Nozzle loading'
a
A relief valve that discharges into a header should be placed higher than
the header i n order t o drain into i t
a
Locate heavy valves near suitable support points. Flanges should be
not closer than 12 inches t o the nearest support, so that installation is
not hampered
a
For appearance, if practicable, keep centerlines of valves at the same
height above floor, and in-line on plan view
Group valves which would be out of reach so that all can be operated
by providing a platform, if automatic operators are not used
I f a chain is used on a horizontally-mounted valve, take the bottom of
the loop to within 3 f t of floor level for safety, and provide a hook near.
by to hold the chain out of the way -see 3.1.2, under 'Chain'
Do not use chain operators on screwed valves, or on any valve l%inches
and smaller
With lines handling dangerous materials i t is better to place valves at a
suitably low level above grade, floor, platform, etc., so thbt the operator
does not have to reach above head height
Make use of brick or concrete walls as possible fire shields for valve
stations
PREFERRED
ARRANGEMENT
Use line-blind valves, spectacle plates or the 'double block and bleed'
where positive shutoff is required either for maintenance or process
needs see 2.7
Do not point valve stems into walkways. truckways, ladder space, etc.
Unless necessary, do not arrange gate and globe valves with their stems
pointing downward (at any angle below the horizontal), as:-
Provide valved drains on all tanks, vessels, etc., and other equipment
which may contain or collect liquids
Provide an upstream isolating valve with a small valved bypass to equipment which may be subject to fracture if heat is too rapidly applied on
opening the isolating valve. Typical use is in steam systems to lessen the
risk of fracture of such things as castings, vitreous-lined vessels, etc
(1) Sediment may collect i n the gland packing and score the stem.
(2) A projecting stem may be a hazard t o personnel.
a
.....
.1.3
A liquid line fitted with a fast-closing valve should be provided with a stand.
pipe upstream and close to the valve to absorb the kinetic energy of the
liquid. A standpipe is a closed vertical branch on a line: air or other gas is
trapped i n this branch to form a pneumatic cushion.
IF THERE IS NO P&ID
TABLE
6.2
PIPING S A F E T Y
PRESSURE-RELIEF-VALVE PIPING
FIGURE 6.4
VAPOR T O ATMOSPHERE
PERSONNEL A R E A
RELIEF VALVE,
SAFETY VALVE,
or SAFETY-RELIEF
VALVE
lM".INCH D R A I N H O L E
VAPOR T O ATMOSPHERE
RELIEF VALVE O R
SAFETY-RELIEF
F R O M VESSEL
OR SYSTEM
Ensure that the disc has room t o rotate when the valve is installed,
as the disc enters the piping i n the open position
KEY
(1)
(2)
(3)
[941
UTILITY STATIONS
6.1.4
6.1.5
A utility station usually comprises three service Ines carrying steam, compressed air and water. 1'he steam line is normally %-inch minimum, and the
other two services are usually carried in I-inch lines. These services are for
cleaning local equipment and hoslng floors, (Frewater is taken from points
fed from an independent water supply .)
Control stations should be designed so that the control valve can be isolated
and removed for servicing. To facilitate this, the piping of the stations should
be as flexible as circumstances permit. Figure 6.5 shows ways of permitting
control valve removal i n welded or screwed systems. Figure 6.6 shows the
basic arrangement for control station piping.
The steam line is fitted with a globe valve and the air and water lines with gate
valves. All are terminated with hose connections about 3% f t above floor or
grade. A utillty station should be located at some convenient steel column for
supporting, and all areas i t is to serve should be reachable with a 50-ft hose.
The two isolating valves permit servicing of the control valve. The emergency
bypass valve is used for manual regulation if the control valve is out of action.
The bypass valve is usually a globe valve of the same size and pressure rating
as the control valve. For manual reaulation in lines 6-inch and larger, a gate
valve is often the more economic choice for the bypass line-refer to 3.1.4,
under 'Gate valve'.
SERVICES: STEAM,AIR,WATER
STATION
syM,o,:
S A W
U T I L I T Y STATION
AIR.WATER S T E A M W A T E R
AW
S W
STEAM-AIR
S A
F I G U R E 6.12
DESIGN POINTS
For best control, place the control station close to the equipment i t
serves, and locate i t at grade or operating platform level
L W A T I OVCRMtADV*LVII
FOR A C C C S l b l L l n i N O I
(1) G A T E V A L V E NPS 1
( 2 ) GLOBE V A L V E NPS 1
(3) GLOBE V A L V E NPS 314
( 4 ) HOSE C O U P L I N G NPS 314
If subject to freezing conditions, utility station steam lines are usually trapped
(otherwise, the trap can be omitted). Water is sometimes run underground in
cold climates using an additional underground cock or plug valve with an ex.
tended key for operating, and a self-draining valve at the base of the riser.
Another method t o prevent freezing, is to run the water and steam lines
i n a common insulation.
I n plan view, instead of drawing the valves, etc., the station is shown as a
rectangle labeled 'SEE DETAIL "Xu ' or 'DWG "Y"-DETAIL "X" ', if
the elevational detail appears on another sheet. See chart 5.7.
1951
-
--
~~p
FIGURES
ORF8CE-TO SUPPLY
THIS V A L V E MAY N
BE REOUIRED IF T
STATION IS CLOSE
W I S T 1 E A Y 09A1N I P T O U l O C O
I f U Y T R O L V A L Y E F A i L L CLMEO
CONTROL V A L V E
6.2
Supports for lines smaller than 2-inch and noncritical lines are often left to
the 'field'to arrange, by noting 'FIELD SUPPORT' on the piping drawings.
LOADS ON SUPPORTS
Refer t o tables P-1, which list the weights per foot of pipe and contained
water (see 6.1 1.2). Weights of fittings, flanges, valves, bolts and insulation are
given in tablesw-1, compiled from suppliers' data.
In the open, single pipes are usually routed so that they may be supported by
fixtures to buildings or structures. A group of parallel pipes in the open is
normally supported on a piperack-see 6.1.2.
Within a building, piping is routed primarily with regard t o its process duty
and secondarily with regard to existing structural steelwork, or to structural
steel which may be conveniently added. Separate pipe-holding structures inside buildings are rare.
FUNCTIONS OF THE SYSTEM OF SUPPORT
6.2.1
(2)
To carry the weight of the piping filled with water (or other liquid
involved) and insulation if used, with an ample safety margin - use a
factor of 3 (= ratio of load just causing failure of support or hanger
to actual load) or the safety factor specified for the project. External
loading factors t o be considered are the wind loads, the probable weight
of ice buildup in cold climates, and seismic shock in some areas
To allow for draining. Holdup of liquid can occur due to pipes sagging
between supports. Complete draining is ensured by making adjacent
supports adequately tilt the pipe-see 6.2.6
(4)
(5)
6.2.4
To ensure that the material from which the pipe is made is not stressed
beyond a safe limit. I n continuous runs of pipe, maximum tensile stress
occurs in the pipe cross sections at thesupports.Table S-1 gives spans for
water-filled steel and aluminum pipe at the respective stress limits 4000
and 2000 psi. Charts S-2 give the maximum overhangs if a 3-ft riser is
included in the span. The system of supports should minimize the
introduction of twisting forces in the piping due t o offset loads on
the supports; the method of cantilevered sections set out in 6.2.4
substantially eliminates torsional forces
(3)
6.2.3
FIGURE 6.13
FIGURES
A large company will usually have a specialist piping support group responsible for designing and arranging supports. This group will note all required
supports on the piping drawings (terminal job) and will add drawings of
any special details.
The piping support group works in cooperation with a stress analysis groupor the two may be combined as one group-which investigates areas of stress
due to thermal movement, vibration, etc., and makes recommendations to
the piping group.The stress group should be supplied with preliminary layouts
for this purpose by the piping group, as early as possible.
The presence of heavy flanges, valves, etc., in the piping will set the center
of gravity away from the midpoint of the associated length. Calculation
of support points and loadings is more quickly done using simple algebra.
Answers may be found by making trial-and-error calculations, but this is
much more tedious.
6.2.2
1971
6.5-6.11&6.13
-
C A L C U L A T I N G PIPE SUPPORTS
F I G U R E 6.15
In figure 6.14(a), the moment about the support of the two flanges is
(30 + 20)(16) = 800 Ib-ft, counter-clockwise. The moment of the 100-lb
valve about the support is (100)(8) = 800 Ib-ft, clockwise. As the lengths of
pipe each side of the support are about the same, they may be omitted
from the moment equation. The problem is simplified to balancing thevalve
and flanges.
F I G U R E 6.14
USE O F M O M E N T S
3Mb BLIND
FLANGE
1
II
XHb SO
1100lb VALVE
FLANGE
1800 I b f t
N
P
Suppose i t was required t o balance this length of piping with a 120 Ib valve
on the right-where should the 120 Ib valve be placed?
SECTIONS OF PIPING
(ASSOCIATED LENGTHS1
2 ft
x = (80)/(1 I ) , or about
7 f t 3 in.
The x2 terms canceled-this must be so, as there can physically be only one
value for X. The load on hanger F is (20)(15) + (360) or 660 Ib.
The support J should be at the center of the associated length of pipe, as
already shown i n figure 6.15, and the load on the support is (30)(15), or
450 Ib.
A more involved example follows:Figure 6.15 shows a length of 4-inch piping held by the hangers F, G,
and H, and support J. The lengths of associated piping are shown b y dashed
separation lines. The weights of pipe and fittings are shown on the drawing.
The 4-inch pipe is assumed to weigh 15 Ib per foot of length. Welded
elbows and tees are assumed t o weigh the same as line pipe.
First consider the section associated with hanger F. The weight of pipe to
the left of F is (15)(20 -x) Ib, and as its center of gravity is at (20 -x)/(2) f t ,
its moment on the hanger is (15)(20 - X ) ~ / ( Z )Ib-ft. The heavy valve and
flanges are assumed t o have their mass center 5 f t from the end, and their
moment is ( x - 5)(360) Ib-ft. Ignoring the pipe 'replaced' by the valve,
the weight of pipe t o the right of F is ( 1 5 ) ( x ) Ib and its moment about F
is (15)(x)(x)/(2) Ib-ft. As the associated length is in balance:
PROBLEM O F
THE END
[ T E X T CONTINUES O V E R L E A F ]
MIDPOINT
\
A
/I_
1W Ib VALVE
\ A
MlDPOlNT
IF
IR
Reaction
5fl
Reaction
15 11
SOLUTION
R = 202% Ib.
which gives
[ ll
121
[3)
Dovide the run of plping lnto parts Plping between the support polnts A and 8 IS
consvjered in three parts: Ill The valve. I21 The length of plpe BC. I31 The length
of pipe AC-the short plece of I n e omitted for the valve is ~gnored,and ths affect
of the elbow neglected.
141
Drop petpend~cularsfrom mldpolnts M I and M2, the valve and support polnl E to
the 8x1s Ilne.
151
Take moments about the axls Ilne, meawrhng the lengths of perpendiculars M2P. ES,
DQ and MI R directly from the plan vlew ithere lengths are noted on the sketch):
PlPE LENGTH AC
120)1181(61
which
gives
PIPE LENGTH CB
t
VALVE ASSY
i151i181161
l2001l9)
LOAD ON SUPPORT
=
IF)i961
as
F = 581 Ib
EXTENSION OF THE METHOD
The same method can be used (1 the angle at the corner is different from 90 degrees, or if
ven~cailines are ~ncludedIn the plplng.
NOTES
I
\
DENOTES ENDS O F
(1)
The axis line must pass thru polnts of suppon. If the axis l ~ n eIS not hor~zontal.
the lengths of the perpend~culars are st111 meawred dtrectly from the plan vlew.
121
Thts method does not take into account addltronal moments due to bsnding and
torston of pipe. However, 11 Is legitimate to calculate lmds on supports as 11the plpe
I S rlgld.
CANTILEVERED
SECTIONS O F
PIPING.
FIGURES
This problem often occurs when running pipes from one piperack to another,
with a change in elevation, as in figure 6.15. Too much overhang will stress
the material of the pipe beyond a safe limit near one of the supports adjacent
t o the bend, and the designer needs to know the allowable overhang.
The nature of the conveyed material, the process, and flow requirements
determine how much sagging can be accepted. Sagging is reduced by bringing
adjacent points of support closer. Pocketing of liquid due to sagging can be
eliminated by sloping the line so that the difference in height between
adjacent supports is at least equal t o triple the deflection (sag) at the midpoint. Lines which require sloping include blowdown headers, pressure-relief
lines, and some process, condensate and air lines. (Air lines are discussed i n
6.3.2, and draining of compressed-air lines i n 6.1 1.4.)
The stresses set up i n the material of the pipe set practical limits on the
overhangs allowed at corners. The problem is like that for spans of straight
pipe allowable between supports. Overhangs permitted by stated limits for
stress are given i n charts S-2.
PIPE SUPPORTS ALLOWING THERMAL MOVEMENT
6.2.5
SPRING SUPPORTS
There are two basic types of spring support: (1) Variable load. (2) Constant
load-refer to 2.12.2. Apart from cost, the choice between the t w o types
depends on how critical the circumstances are. For example, if a vertical line
supported on a rigid support at floor level is subject t o thermal movement,
a variable-spring hanger or support at the top of the line is suitable-see
figure 6.16 (a) and (b).
If a hot line comes down to a nozzle connected to a vessel or machine, and
i t is necessary to keep the nozzle substantially free from vertical loading,
a constant-load hanger can be used-see figure 6.16(c). Cheaper alternate
methods of supporting the load are by a cable-held weight working over a
pulley, as illustrated in figure 6.16(d), or by a cantilevered weight.
V A R I A B L E & CONSTANT.LOAD HANGERS & SUPPORTS
(b) V A R I A B L E
SPRING
HANGER
(a1 V
SPRING
ARIABLE
3
'ONSTANT
LOAD
HANGER
FIGURE 6.16
Inside a building, both large and small sloped lines can rest on steel brackets,
or be held with hangers. Rods with turnbuckles are used for hangers on lines
required to be sloped. Otherwise, drilled flat bar can be used. (Adjustable
brackets are available from the Unistrut and Kindorf ranges of support
hardware.)
(d) C O U N T E R .
WEIGHT
SUPPORT
-7.
COUNTER
WEIGHT
6.2.7
Pipe made either from flexible or rigid plastics cannot sustain the same span
loads as metal pipe, and requires a greater number of support points. One
way of providing support is to lay the pipe upon lengths of steel channel sections or half sections of pipe, or by suspending i t from other steel plpes. The
choice of steel section would depend on the span loads and the size and type
of plastic pipe.
For glass process and drain lines, hangers for steel pipe are used, provided that
they hold the pipe without causing local strains and are padded so as not to
crack the pipe. Rubber and asbestos paddings are suitable. Uninsulated
horizontal lines from 1 t o 6 inch i n size containing gas or liquid of specific
gravity less than 1.3 should be supported at 8 to 10 ft intervals. Couplings
and fittings should be about 1 f t from a point of support.
6.2.6
As pipe isnot completely rigid, sagging between points of support must occur.
I n many instances, sagging is acceptable, but i n others i t must be restricted.
[loo1
6.2.8
Terms such as 'dummy leg', 'ar,~nor', 'shoe', etc., used i n detailing supporting
hardware are explained i n 2.12.2. Refer to chart 5.7 for symbols.
For better stress distribution in the pipe wall, pipe support saddles are
usually used on large lines. They can also be used for lines that may
twist over when moving
DESIGN POINTERS
GENERAL
Design hangers for 2%inch and larger pipe to permit adjustment after
installation
If necessary, suspend pipes smaller than 2-inch nominal size from 4-inch
and larger pipes
DUMMY LEGS
Table 6.3 suggests sizes for dummy legs. The allowable stress on the wall
of the elbow or line pipe t o which the dummy leg is attached sets a maximum
length for the leg. The advice of the stress group should be sought.
TABLE 6.3
I 1% 1
10 12 14
1 6 I1 8 I1 8 1I 10
5 8 8 1 0
Anchors are required as stated i n the following two points. However, advice
from the stress and/or piping support groups should be obtained:
r
Provide anchors as necessary to prevent thermal or mechanical movement overloading nozzles on vessels or machinery, branch connections,
cast-iron valves, etc.
Provide anchors t o control direction of expansion; for example, at
battery limits and on piping leaving units, so that movement is not
transmitted to piping on a piperack
SUPPORTING VALVES
Large valves and equipment such as meters located at grade will usually
require a concrete foundation for support
ANCHORS
Welding the pipe directly t o shoes is not always acceptable; for example
with rubber-lined pipe. Bolted or strapped shoes are more suitable
FIGURE
6.1 6
TABLE
6.3
Most centrifugal pumps have baseplates that collect any leakage from the
pump. The baseplate will have a threaded connection which is piped to the
drain hub. Waste seal water is also piped to the drain hub-see figure 6.19.
6.3.1
Most pumps used i n industry are of the centrifugal type. Figures 6.17 and
6.18 show typical piping and fittings required at a centrifugal pump together
with the valves necessary to isolate the pump from the system.
The check valve is required t o prevent possible flow reversal in the discharge
line. A permanent in-line strainer is normally used for screwed suction piping
and a temporary strainer for butt-weldedlflanged piping. The temporary
strainer is installed between flanges-see figure 2.69. A spool is usually required t o facilitate removal.
INSTALLATION
Although centrifugal pumps are provided with suction and discharge ports of
cross-sectional area large enough to cope with the full rated capacity of the
pump, it is often necessary with thick fluids or with long suction lines t o use
an inlet pipe of larger size than the inlet port, t o avoid cavitation. Cavitation
is the pulling by the pump of vapor spaces in the pumped liquid, causing
reduction of pumping efficiency, noisy running, and possible impellor and
bearing damage. Refer t o 6.1.3, under 'Which size valve t o use?'.
Do not route piping over the pump, as this interferes with maintenance.
I t is better t o bring the piping forward of the pump as shown in figure
f-.
i 17
..
Most pumps have end suction and top discharge. Limitations on space may
require another configuration, such as top suction with top discharge, side
suction w i t h side discharge, etc. Determination of nozzle orientation takes
place when equipment layout and piping studies are made.
Position valves for ease of operation placing them so they are unlikely
t o be damaged by traffic and will not be a hazard to personnel-see
table 6.2 and chart P-2
The foundation may be of any material that has rigidity sufficient to
support the pump baseplate and withstand vibration. A concrete foundation built on solid ground or a concrete slab floor is usual. The pump
is positioned, the height fixed (using packing), and the grout is then
poured. Grout thickness is not usually less than one inch-see figure
6.17
A p i t in which a pump is installed should have a drain, or have a
sump that can be drained or pumped out
Pumps, compressors and turbines may require water for cooling bearings, for
mechanical seals, or for quenching vapors t o prevent their escape t o
atmosphere. Piping for cooling water or seal fluid is usually referred t o as
auxiliary, trim, or harness piping, and the requirement for this piping is
normally shown on the P&ID. This piping is usually shown i n isometric
view on one of the piping drawings.
In order t o cool the gland or seal of a centrifugal pump and ensure proper
sealing, i t is usually supplied with liquid from the discharge of the pump,
by a built-in arrangement, or piped from a connection on the pump's casing.
The gland may be provided with a cooling chamber, requiring piped water.
If a pump handles hot or volatile liquid, seal liquid may be piped from an
external source.
a
a
VALVES
DRAINING
Valves are 'line size' unless shown otherwise on the P&lD. See 6.1.3
under 'Which size valve t o use?'
Do not use globe valves for isolating pumps. Suction and discharge line
isolating valves are usually gate valves, but may be other valves offering
low resistance t o flow
SUCTION LlNE
For locations of drain connections in the discharge line, see figures 6.17
thru 6.21
Reciprocating and rotary pumps of this type must be protected against overloading due to restriction In the discharge line. If a positive-displacement
pump is not equipped with a relief valve by the manufacturer, provide a
relief valve between the pump discharge nozzle and the first valve in the
discharge line. The discharge from the relief valve is usually connected to
the suction line between the isolatinq valve and the pump.
As positive displacement pumping does not greatly change the flow velocity,
reducers and increasers are not usually required in suction and discharge
lines. See figures 6.20 and 6.21. A positive-displacement pump having a
pulsating discharge may set the piping into vibration, and t o reduce this
an air chamber (pneumatic resewoir) such as a standpipe can be provided
downstream of the discharge valve.
TURNING VANES
A pump with screwed connections requires unions in the suction and dis.
charge lines to permit removal of the pump.
If a pump has the suction nozzle at the side with split flow t o the impellor
provide a straight run of pipe equal t o 3 t o 5 pipe diameters of the suction
line to connect to the nozzle. Alternately, an elbow may be connected t o
the suction nozzle, but i t must be arranged i n a plane at 90 degrees t o the
driving shaft, t o promote equal flow t o both sides of the impellor. I f an
elbow must be i n the same plane as the driving shaft of the pump, consider
the use of turning (or splitter) vanes t o induce more even flow. Uneven flow
causes damage t o the impellor and bearings.
If a centrifugal pump has the suction nozzle at the end (in line with the
drive shaft), an elbow may be connected directly t o the nozzle at any
orientation.
I t may be necessary t o trace a pump (see 6.8.2) in order to keep the conveyed
material i n a fluid state, especially after shutdown. This problem arises either
with process material having a high melting point, or i n freezing conditions.
Alternately, jacketed pumps can be employed (such as Foster jacketed
pumps available from Parks-Cramer).
DISCHARGE LlNE
The outlet pipe for centrifugal and other non-positive displacement pumps is
in most cases chosen t o be of larger bore than the discharge port, in order to
reduce velocity and consequent pressure drop i n the line. A concentric
reducer or reducing elbow is used i n the discharge line t o increase the diameter. There is no restriction on the placement of elbows i n discharge lines
as there is in suction lines.
ALTERhATE PIPING
ARRANGEMENT
STATE E L E V A T I O N
STATE E L E V A T I O N OF
OFFSET
. Larp. 0
-Small I D
1'-0 M I N I M U M TO
PUMPCENTERLINE [SHAFT1
SCREWED PIPING
DISCHARGE M A N I F O L D W I T H
SINGLE c H r w V A L V E
L A h U E K QLLUOLI
A@AA.NCWUiIABQYC
FIGURES
i
VALVE O N S T R l k i R
FOR PERiODiC
BLOWDOW~
POR % I S ?
TO THOSE
P90YIOf i i i X 8 L l T I
A V O I D SHORT P l G i O
CONNtCTlONS FROM
HEADERS
0 6 REDUCER 5 r t
6.17-6.19
TO ACCOMMODATE VALVES
SlYllAR TO THOP
FOR SCREWED ?lU18
NEEDS TO TURN W W N
121
131
I41
161
1-51
CASING VENT.
I7Al
I7 Bl
181
1101
I111
1131
1141
I161
1161
COMPRESSOR PIPING
6.3.2
a
a
Provide air entry louvers i f a compressor takes air from within a compressor house or other building
a
a
BRANCH CONNECTION
OUTLET VALVE
FIGURE 6.23
SCHEMATIC ARRANGEMENTS
OF COMPRESSED.AIR EQUIPMENT
(rl
Avoid low points i n suction lines where moisture and dirt can collect.
I f low points cannot be avoided, provide a clean-out -see figure 6.24
I f the suction line is taken from a header, take i t from the top of the
header t o reduce the chance of drawing off moisture or sediment
A line-size isolating valve is required for the suction line if the suction
line draws from a header shared with other compressors
SINGLE.STAGE COMPRESSOR
-RAIN
R
UNLOADING VALVE L BYPbSS
( b ) TWO-STAGE COMPRESSOR
FIGURE 6.24
SUCTION LINES TO
AIR COMPRESSORS
r BK?ZER
6 ft min.
For efficiency the air supply should be taken from the coolest source
such as the shaded side of a building, keeping t o building clearances
shown in figure 6.24
I f the air supply is from outside the building, locate the suction point
above the roofline, and away from walls to avoid excessive noise
o
8
..
..'
DRAIN
,. ...
FOR CLEANING
PURPOSES
.".-... ' . ,
COMPRESSOR
The design of supports for piping t o large compressors (especially for reciprocating machines) requires special knowledge. Usually, collaboration is
necessary with the piping support group, the stress group, and the compressor
manufacturer's representative. A major problem is that the compressor may
be forced from alignment with its driver if the piping and supports are not
properly arranged.
If a diesel or gasoline engine is used as driver, a flexible joint on the engine's
exhaust pipe will reduce transmission of vibration, and protect the exhaust
nozzle. Flexible connections are sometimes needed on discharge and suction
piping. Pulsation i n discharge and-to a lesser extent-suction lines, tends to
vibrate piping. This effect is reduced by using bellows, large bends and
laterals, instead of elbows and tees.
INSTRUMENTATION & INSTRUMENT CONNECTIONS
Figure 6.23 shows the more useful locations for pressure and temperature
gages, but does not show instiumentation for starting, stopping and unloading
the compressors. Simple compressor control arrangements using pressure
switches have long been used, but result in frequent starting and stopp~ngof
the compressor, causing unnecessary wear to equipment.
Automatic control using an unloading valve is superior: table 3.6 gives the
working principles-see 3.2.2, under 'Unloading'. Further information can be
found in the 'Compressor installation manual' (Atlas-Copco). Unloading
valves are allocated instrument numbers.
The air-pressure signals for unloading, starting, loading and stopping a compressor should be free from pulsations. I t is best t o take these signals from
a connection on the receiver or a little downstream of it.
Details of construction of instrument connections are given i n 6.7, Instrument
branches should be braced to withstand transmission of line vibration.
.3.2
PRESSURE.RELIEF VALVES
Pressure-relief valves should be installed on interstage piping and on a discharge line from a compressor to the first downstream isolating valve. A
pressure-relief valve may be vented t o the suction line-see figure 6.23. Each
pressure-relief valve should be able to discharge the full capacity of the
compressor.
CHECK VALVE
Unless supplied with (or integral with) a compressor, a check valve must be
provided t o prevent backflow of stored compressed air or other gas.
DISTRIBUTION OF COMPRESSED AIR
Headers larger than 2-inch are often butt welded. Distribution lines are
screwed and usually incorporate malleable-iron fittings, as explained in 2.5.1.
Equipment used i n distribution piping is described i n 3.2.2.
A more efficient layout for compressed air lines is the ring main with auxiliary
receivers placed as near as possible to points of heavy intermittent demand.
The loop provides two-way air flow t o any user.
COMPRESSED AIR USAGE
FIGURES
6.23 & 6.24
PIPING TO S T E A M T U R B I N E S
6.4
r'R
ATYOYH6II
STEAM
TO D R A I N
tl
FIGURE 6.25
ATUOSPNLIII
CQQLwB
(1)
6.4.1
PROTECTIVE PIPING
MATTER & W A T E R
IN THE STEAM FEED
DRIPLEG &STRAINER, or
SEPARATOR, IN THE FEED
LlNE (See figure 6.9)
EXCESSIVE PRESSURE IN
STEAM FEED CAUSING
OVER-FAST RUNNING OR
CASING RUPTURE
ORIFICE BYPASS TO
FEED SMALL AMOUNT
OF STEAM TO TURBINE
AT ALL TIMES
(3)
TO B O L E * P t t O W A T l R T I N <
directly t o atmosphere.
Suitable
TABLE 6.4
HAZARD TO TURBINE
Exhaust Is discharged
Intermittent use.
Exhaust IS taken t o
contlnuously.oparatlng
Exhaust IS condensed
(2)
IIC<I"I"
KEY:
(1)
c,,,,.,,,
XQW
6.4.3
FIGURE 6.26
6.4.2
Figure 6.25 shows three methods for dealing with the turbine's exhaust.
Steam from an intermittently operated turbine may be run t o waste and all
that is required is a simple run of pipe to the nearest outside wall or up thru
the roof. Exhausts should be well clear of the building and arranged so as not
t o be hazardous t o personnel. The turbine discharge will include drops of
water and oil from the turbine, which are best collected and run t o drain. A
device suitable for this purpose is a Swartwout 'exhaust head' shown i n figure
6.26. Alternately, Ream discharged from a continuously running turbine may
be utilized elsewhere, i n a lower-pressure system.
6 11 minimum
cimranc* for
sxhaun from
hilding wall
11101
VESSEL CONNECTIONS
6.5
NOZZLE LOADING
With exceptions and limitations stated in section 8 of the ASME Boiler and
Pressure Vessel Code, vessels subject t o internal or external operating
pressures not exceeding 15 PSI need not be considered to be pressure vessels.
A vessel operating under full or partial vacuum and not subject t o an external
pressure greater than 15 PSI would not require Code certification.
COLUMN OPERATION
The feed is heated (in a 'furnace' or exchanger) before it enters the column.
As the feed enters the column, quantities of vapor are given off by 'flashing',
due to the release of pressure on the feed.
Check special nozzle needs, such as for flush-bottom tank valves (see
3.1.9)
Figure 5.14 shows the type of drawing or sketch sent t o a vessel fabricator.
Preliminary piping layouts are made t o determine a suitable nozzles arrangement. A sketch of the vessel showing all pertinent information is sent to the
vessel fabricator, who then makes a detail drawing. The preliminary studies
for pressure vessel piping layouts should indicate where pipe supports and
platforms (if required) are t o be located. I n the event that the vessel has t o
be stress-relieved, the fabricator can provide clips or brackets-see 6.2.8,
under 'Welding pipe-support and platform brackets t o vessels, etc.'
Check whether nozzles are required for an electric heater, coils for
heating or cooling, or vessel jacket. A jacket requires a drain and vent
PRESSURE VESSELS
6.5.1
Vessel connections are often made with couplings (for smaller lines), flanged
or welding nozzles, and pads fitted with studs, designed t o mate with flanged
piping. Nozzle outlets are also made by extrusion, t o give a shape like
that of the branch of a welding tee-this gives a good flow pattern, but is
an expensive method usually reserved for such items as manifolds and dished
heads. Weldolets, sockolets and thredolets are suitable for vessel connections
and are available flat.based for dished heads, tanks, and large vessels.
FIGURES
.
.
As the vapors rise up the column, they come into intimate contact with
downflowing liquid-see figure 6.29. During this contact, some of the heavier
components of the vapor are condensed, and some of the lighter components
of the downflowing liquid are vaporized. This process is termed 'refluxing'.
I f the composition of the feed remains the same and the column is kept in
steady operation, a temperature distribution establishes in the column. The
temperature at any tray is the boiling point of the liquid on the tray. 'Cuts'
are not taken from every tray. The P&ID shows cuts that are to be made, including alternatives-nozzles on selected trays are piped, and nozzles for
alternate operation are provided with line blinds or valves.
Ill11
- .- --.- TABLE
6.4
INSTRUMENT SPAC
INTERMEDIATE CUT
'BOTTOMS' PUMP
ELEVATION
FIGURE 6 27
F I G U R E 6.29
LIOUID FLOW
NOZZLE FOR
REMOVING A
FRACTION. or
'CUT' (Sm t e x t 1
DOWNCOMER
AREA FOR
TRAY 22
TRAY 23
TRAY 22
t
n
In addition to the condenser for the top product, a steam-heated heat exchanger, termed a 'reboiler', may be used to heat mater~aldrawn from a
selected level in a column; the heated material is returned to the column.
Reboilers are required for tall columns, and for columns operated at high
temperatures, which are sublect to appreciable loss of heat. Mount~ngthe
reboiler on the side of the column minmlzes p~plng.
SPARGER UNIT
F I G U R E 6.31
FLOW
'RAY
ORIENTATION
FIGURE 6.30
If the cuts are t o be taken either from even-numbered trays, or from oddnumbered trays, all nozzles can be located on one side of the column, facing
the piperack. If cuts are t o come from both even- and odd-numbered trays,
i t will almost certainly be impossible to arrange all nozzles toward the
piperack. (See 'Arranging column piping', this section.)
PLATFORMS & LADDERS
Platforms are required under manholes, valves at nozzles, level gages, controllers if any, and pressure relief valves. Columns may be grouped and
sometimes interconnecting platforms between columns are used. lnd~vidual
platforms for a column are usually shaped as circular segments, as shown in
figure 6.30. A platform is required at the top of the column, for operating
a davit, a vent on shutdown, and for access to the safety-relief valve.
This top platform is often rectangular.
Usual practice is to provide a separate ladder to go from grade past the
lowest platform. Ladders are arranged so that the operator steps sideways
onto the platforms.
Ladder length is usually restricted to 30 f t between landings. Some States
allow 40 f t (check local codes). If operating platforms are further apart
than the maximum permissible ladder height, a small intermediate platform
is provided.
Ladders and cages should conform to the company standard and satisfy the
requirements of the US Department of Labor (OSHA), part 1910.(0).
DAVIT
Referring t o figure 6.30, the davit should be located at the top of the column
so that i t can lower and raise tray parts, piping, valves, etc., between the platforms and the dropout area at grade.
r
r
r
------
-5.2
--
As lines from nozzles on the column are run down the length of the column,
it is logical t o start arranging downcomers from the top and proceed down
the column. A lower nozzle may need priority, but usually piping can be
arranged more efficiently if the space requirements of piping coming from
above are already established.
VALVES
Valves and blinds which serve the tower should be positioned directly on
nozzles, for economy. I t is desirable to arrange other valves so that lines
are self-draining.
Sometimes tray spacing is increased slightly to permit installation of manholes. I t may be possible to rotate trays within limits, to overcome a
difficulty in arranging column piping. Such changes i n tray spacing and
arrangement must be sanctioned by the process engineer and vessel designer.
Platforms should be located to give access to large valves. Small valves may
be located at the ends of platforms. Control valves should be accessible
from operating platforms or from grade.
Allocate space for vertical lines from lower nozzles, avoiding running
these lines thru platforms if possible
The pressure-relief valve for the relief line should be placed at the highest
point in the line, and should be accessible from the top platform.
Lines from the tops of columns tend t o be larger than others. Allocate
space for them first, keeping the lines about 12 inches from the platforms and the wall of the column-this makes supporting easier, and
permits access t o valves, instruments, etc.
Provide a clear space for lowering equipment from the top of a column
(for maintenance, etc.)
INSTRUMENTS 81 CONNECTIONS
FIGURES
THERMAL INSULATION
6.30& 6.31
Plot plan showing space available for column location, and details of
equipment which is to connect to the column
P&ID for nozzle connections, NPSH of bottoms pump, instrumentation, line blinds, relief valves, etc.
The base ring of a column's skirt is attached to a reinforced-concrete construction. The lower part of this construction, termed the 'foundation', is
below grade, and is square in plan view: the upper part, termed the 'base',
to which the base ring is attached, is usually octagonal and projects above
grade approximately 6 inches.
[1151
DESIGN POINTERS
6.6.2
Engineering Notes:
Put fouling and/or corrosive fluids inside the tubes as these are (except
U-type) easily cleaned, and cheaper to replace than the shell
Put the hotter fluid in the tubes to reduce heat loss to the surround~ngs
6.6.1
by the exchangers, and will state their flow rates, temperatures and pressures.
EXCHANGER D A T A SHEETS one of these sheets is compiled for each
exchanger design b y the project group. The piping group provides nozzle
orientation sketches (resulting from the piping studies). The data sheet informs the manufacturer or vendor of the exchanger concerning performance
and code stamp requirements, materials, and possible dimensional limitations.
TEMA CODING FOR EXCHANGER TYPE
FIGURE 6.32
HEAD
HEAD
NOZZLE
/'
'DRAIN
1st F L U I D
LEAVES
(WARM)
.\SADDLE
/
SADDLE
DRAIN'
Nozzle Positions:
Arrange nozzles to suit the best piping and plant layout. Nozzles may
be positioned tangentially or on elbows, as well as on vertical or
horizontal centerlines (as usually offered at first by vendors). Although
a tangential or elbowed nozzle is more expensive, it may permit economies i n piping multiple heat exchangers
TABLE 6.6
(a)
Exchangers arranged
(b)
piping
Locating Exchangen:
units
PIPING T O NOZZLES
O F H E A T EXCHANGERS
FIGURE 6.33
&
between paired
31
,/
(1)
(2)
(31
NOTES
FIGURES
Access t o operating valves and instruments (on one side only suffices)
Operating space for any davit, monorail or crane, etc., both for movement and to set loads down
W ELBOW NOZZLE
q@
TABLE
6.5
1I 2
2 '12
20 thru 40
50
65
80
15
PIPE. 4
Threaded Thermowells
in Straight Runs
MIN 1 6
SWAGE TSE B L t
6 and larger
LONG
PIPE I
THREDOLET 1'
MIN x 6
LONG
'"tiUOXtli
8W
'\
tA
'
F
2
2
Threaded Thermowells
MAYBE NtEDroTO
F i l TWLRUOITII
in Elbows
.Smw
.,.
not n r & d il D
I,1"
or Iar(er
ELBOLET
1 ' THREADED
1" THREADED
0
W
I-
a
K
Flanged Thermowells
in Straight Runs
I-
Flanged Thermowells
in Elbows
FLANGE 1 X ' S W
FLANGE, 1k"SW
ELBOLET l % " S W
Socket-welded
6.7
INSTRUMENT CONNECTIONS
6.7.1
Connections will usually be specified by company standards or by the specifications for the project. If no specification exists, full- and half-couplings,
swaged nipples, thredolets, nipolets and elbolets, etc., may be used. Chart 6.2
illustrates instrument connections used for lines of various sizes. The fittings
shown in chart 6.2 are described in chapter 2. Orifice flange connections
are discussed in 6.7.5.
CHOOSING THE CONNECTION
6.7.2
More than one level gage, level switch, etc., may be required on a
vessel: consider installing a 'strongback' to a horizontal vessel on
which instrument connections have to be made-see figure 6.34(c)
LEVEL-GAGE CONNECTIONS
(a)
FIGURE 6.34
L E V E L GAGE
(b) C O N N E C T I O N S F O R A G A G E GLASS
ASSEMBLY
The choice of instrument connection will depend on the conveyed fluid and
sometimes on the required penetration of the element into the vessel or pipe.
Instrument connectionsshould be designed so that servicing or replacement of
Instruments can be cartled out without interrupting the process. Valves are
needed to ~solategages for maintenance dur~ngplant operation and dur~ng
hydrostatic testing of the piping system. These valves are shown in chart 6.2
and are referred t o as 'root' or 'primary'valves.
1
NlPPLEor
1 THREADED PIPE
6.7.3
Chart 6.2 illustrates various methods for making temperature and pressure
connections. At the bottom of chart 6.2 a method of connecting a diaphragm
flange assembly (diaphragm isolator) is shown. Corrosive, abrasive or viscous
fluid in the process line presses on one side of the flexible diaphragm, and the
neutral fluid (glycol, etc.) on the other side transmits the pressure.
VALVE
x r
--
SWG TEE
CHART
--
6.2
PLUG
UNION
(C) C O N N E C T I O N S O N S T R O N G B A C K
V A L V E3/4\11.
PLUG
3141n.
SWG 2 i n . x 3/41",
BLE-TSE
2in.
r
8
:z:zt 1 ng
-2in.
----X:
Connection f o r
pressure gage.
level gage. etc.
VESSEL
NPT,
ELEMENT. 114 ~ n c hd ~ a r n e t e r -
3
Draln
WELL
2ln!
260 ~ n c hb o r e
NPT
Drain
S BLE-TSE
W 21' G x 3/41",
-VALVE
3/41",
PLUG 3/41",
.6.34
.~
.~-
6.7.5
ROTAMETER CONNECTIONS
FIGURE 6.35
(b) I N D U S T R I A L R O T A M E T E R
(a) P I P I N G T O R O T A M E T E R
Manometers for use with orifice plate assemblies are calibrated in terms of
differential pressure by the manufacturer. The meter run (that is, the piping
in which the orifice plate is t o be installed) must correspond with the piping
used to calibrate the orifice plate-the readings will be in error if there is very
much variation i n these two piping arrangements.
Sometimes the orifice assembly includes adjacent piping, ready for welding
in place. Otherwise, lengths of straight pipe, free from welds, branches or
obstruction, should be provided upstream and downstream of the orifice
assembly.
Table 6.6 shows lengths of straight pipe required upstream and downstream
of orifice flanges (for different piping arrangements) to sufficiently reduce
turbulence in liquids for reliable measurement.
PIPING T O FLANGE TAPS
FIGURE 6.36
GAGE
r\ A
/f---'
:-------I
KEY:
(1) 1-Inch mlnlmum clearance between
The orifice plate is held between special flanges having 'orifice taps1-these
are tapped holes made in the flange rims, to which tubing and a pressure
gage can be connected, as i n figure 6.36. A pressure gage may be termed a
'manometer'.
CLEARANCES
-7.5
-
CLEARANCES FOR
CLEARANCES FOR
LINES CONVEYING
AIR OR OTHER GAS
TABLE 6.6
FIGURE 6.38
OF ORIFICE ASSEMBLY
1'
LINES CONVEYING
LIQUIDS OR STEAM
PLANS
ELEVATIONS
=access space
-1
TABLE
6.6
6.8
NOMINAL
6.8.1
THERMAL INSULATION
PlPE
SIZE
INCHES
(in.)
below 4 0 0
INSULATION
to 1
'Insulation' is covering material having poor thermal conductivity applied externally to pipe and vessels, and is used: (1) To retain heat in a pipe or vessel
SO as to maintain process temperature or prevent freezing. (2) To minimize
transfer of heat from the surroundings into the line or vessel. (3) To safeguard personnel from hot lines. The choice of insulation is normally included
with the piping specification. The method of showing insulation on piping
drawings is included in chart 5.7.
3
4
6
8
10
12
14
16
18
20
24
1
1
1
1
1
1
1.5
1.5
1.5
1.5
2
2
Installed insulation normally consists of three parts: ( 1 ) The thermal insulating material. (2) The protective covering for it. (3) The metal banding to
fasten the covering. Most insulating materials are supplied in formed pieces
to fit elbows, etc. Formed coverings are also available. Additionally, i t is
customary t o paint the installed insulation, and to weatherproof i t before
painting, if for external use.
500 F I
P w w n ~ Protut)(ln
l
FI
Alberror. S ~ l t u r ~Mapnala
,
1 to 2 ~ncher
Mbnaal Wool
2
2
2
2.5
2.5
2.5
2.5
2.5
2.5
3
3
3
3
3
2
2
2.5
2.5
2.5
3
3
3
3
3
3.5
3.5
3.5
3.5
2.5
2.5
3
3
3.5
3.5
3.5
4
4
4
4
4
4
6.8.2
TABLE 6.7
1.5
1.5
1.5
1.5
1.5
1.5
2
2
2
2
2
2
2
2
JACKETING
APPLICATION
2
2
1
1.5
1.5
1.5
1.5
1.5
1.5
1.5
2
2
2
2
2
2
TH'CKNESS
OF INSULATION
TABLE 6.8
1 to 3 lncha
r1221
FIGURE 6.39
r
( a ) JACKETED PIPING S H O W I N G JUMPOVERS
'"
7
' 5.3
STEAM
UNION lTYPl
Electric tracing allows close control of temperature, and can provide a wider
range of temperatures than steam heating.
GETTING HEAT TO THE PROCESS LINE (USING STEAM)
CONDENSATE
If the process line temperature has to approach that of the available steam,
jacketing gives the best results. Barton and Williams have stated 141 that the
cheaper method of welding steam tracers directly to the process lines has proven adequate. I n this unusual method, the weld~ngis 'tack' or continuous
depending on how much heat is req~iiredto be transferred thru the weld.
INSULATION ITYPI
CONDENSATE
A greater rate of heat transfer may be achieved by using two (seldom more)
parallel tracers. Sometimes a single tracer is spirally wound about the pipe,
but spiral wlnding should be restricted to v u r t c a hnes wtiere condensate can
drain by gravity. I f the temperature of tile conveyed fluid has t o be closely
maintained, winding the tracer is too inaccurate-but it is a suitable method
for getting increased heating in non-critical applications.
Swaged End
insert End
To improve heat transfer between the tracer and plpe, they may either be
pressed into contact by banding or wiring them together at frequent ( 1 to
4 ft) intervals, or a heat-conducting cement such as 'Thermon' can be applied.
Unless used to anchor the tracer, banding I S norlnally applied sufficiently
loosely to permit the tracer to expand.
..
Hot spots occur at the bands. If t h s IS undesirable for a product line, a thin
piece of asbestos may be inserted between tracer and 1i:ie.
( c ) C O N S T R U C T I O N S F O R J A C K E T E D HOSE
There are advantages and disadvantages with the various systems. Piping whlch
is to be externally traced can be planned with little concern for the tracing.
Fluid-jacketed systems are flanged, and last-rlii~lutechanges could result In
delays. Jacketing offers superior heat transfer and should be seriously consldered for product lines, especially for those coriveying viscous liquids and
material which may solidify, whereasservice lines usually just need to be kept
from freezing and tracing is quite adequate for them. If process material has
to be kept cold in the line, refrigerant-jacketed systems are the only practicable choice.
FIGURE
6.39
For process lines, all systems should be evaluated on the criteria of heat distribution, initial cost and long-term operating and maintenance costs before a
decision can be made.
TRACING
External 'tracing' consists in running tubing filled with a hot fluid (usually
steam), or electric heating cables, in contact with the outer surface of the
pipe to be kept warm. The tubing or cables may be run parallel to the pipe
or wound spirally around it. The pipe and tracer(s) are encased in thermal
insulation.
Using the symbols given In chart 5.7, traclng is snown on the plan and elevation drawings of the plant piping and i t L V I s m ~ l i l r l ybe indicated on the
Trtlcing IS
cl
isometric drawings, 1 1 wrll also be iridicatcc: (111 ,illy ~ r i i ~ di1si:d
one of the last aspects of plant deslgri, alid sttarn subtieaders cdn either be
shown directly on the plplng dr,l~zririgsor 011 si:pi,ls or illin prints
TABLES
STEAM TRACING
6.8.3
Expansion can be accommodated b y looping the tracer at elbows andlor providing horizontal expansion loops i n the tracer. Vertical downward expansion loops obstruct draining and will cause trouble i n freezing climates, unless
the design includes a drain at the bottom of the loop, or a union to break
the loop. I t is necessary to anchor tracers t o control the amount of expansion
that can be tolerated in any one direction. Straight tracers 100 f t or longer are
usually anchored at their midpoints.
Steam pressures i n the range 10 to 200 PSIG are used. Sometimes steam will
be available at a suitable pressure for the tracing system, but if the available
steam is at too high a pressure, it may be reduced by means of a control
(valve) station-see 6.1.4. Low steam pressures may be adequate if tracers
are fitted with traps discharging to atmospheric pressure. I f a pressurized
condensate system is used, steam at 100 t o 125 PSlG is preferred.
EXAMPLE: System traced with copper tubing: coefficient of linear expansion of copper = 0.000009 per deg F. Steam pressure to be used = 50 PSlG
(equivalent steam temperature 298F). Lowest ambient temperature = 50 F.
If the anchor is located 20 f t from the elbow, the maximum expansion in
inches is (298-50)(0.000009)(20)(12) = 0.53 in. This expansion will usually
be tolerable even for a small line with the tracer construction for elbows
shown in figure 6.40.
SIZING HEADERS
The best way to size a steam subheader or condensate header serving several
tracers is t o calculate the total internal cross-sectional area of all the tracers,
and to select the header size offering about the same flow area.Table 6.9
allows quick selection if the tracers are all of the same size:
NUMBER OF TRACERS PER HEADER
TABLE 6.9
1
0 53 inch EXPANSION
LOWEST AMBIENTTEMPERATURE
318
114
112
314
1
1X
2
9
1
36
64
4
6
2
7
16
28
1
4
9
16
2
4
7
50 F
NUMBER OF TRACERS
3;
SCH 80 carbon steel pipe, or copper or stainless steel tubing is used for
tracers. Selection is based on steam pressure and required tracer size. In practice, tracers are either 112 or 318-inch size, as smaller sizes involve too much
pressure drop, and larger material does not bend well enough for customary
field installation.
112-inch OD copper tube is the most economic material for tracing straight
piping. 318-inch OD copper tubing is more useful where small bends are
required around valve bodies, etc. Copper tubing can be used for pressures up
to 150 PSlG (or t o 370 F ) . Table T-1 gives data for copper tube.
The rate at which condensate forms and fills the line determines the length
of the tracer in contact with the pipe. Too many variables are involved to
give useful maximum tracer lengths. Most companies have their own design
figure (or figures based on experience) for this: usually, length of tracer in
contact with pipe does not exceed 250 ft.
Supply lines from the header are usually socket welded or screwed and sealwelded depending on the pressures involved and the company's practice. A
pipe-to-tube connector is used to make the connection between the steel pipe
and tracer tube -see figure 2.41.
1 PSI steam will lift condensate about 2.3 ft, and therefor vertical rises
will present no problem unless low-pressure steam is being used. Companies
prefer to limit the vertical rise in a tracer at any one place t o 6 f t (for 25-49
PSlG steam) or 10 f t (for 50-100 PSlG steam). As a rough guide, the total
height, i n feet, of all the rises in one tracer may be limited to one quarter of
the initial steam pressure, in PSIG. For example, i f the initial steam pressure
is 100 PSIG, the total height of all risers i n the tracer should be limited
t o 25 ft. The rise for a sloped tracer is the difference i n elevations between
the ends of the sloping part of the tracer.
DOUBLE OR TRIPLE
B&NDFORTR&CEH
WRING TRilCER
TO $106 TO
ALLOW FOR EXPANSION ANDTO
lMPROVL HEATING OF ELBOW
THACt BbL<Or ~ L B O W
IN F R E ~ Z ~ N G C L I U A T L S
UNION TO BREAK L W P
AND
DRAIN
LlNE
IN
FRLEZlNG
CONOlTlONS
STEEL TRACER
CAN BE WELDEO
TO F L A T WAR
d .NUMBER OF COlLS
STEAM SUPPLY
TRACER AT VALVES
I L U S t r , , 1" V A L Y E
"NO F L I N C L S W U I P
AUOUNO 46 EXTRI\
* E l i 1 IS REUUIREO
n i L o n FOR REMOY
ING F l l N G t BOLTS
~ * ~ ~ P A O VUNIONS
~ U L
A LADDER OR AOJACENT
CONDENSATE RETURN
TRACING VESSELS
TOCONDENSATE
CONDENSATEHEAOLR
T O CONOENSATt C
COLLECTING SYSTEM
VESSEL TRACING
is,*,
END ARRANGEMENT
111.114.11
TABLE
6.9
6.9
SUPERHEATED STEAM
If heat is added to a quantity of dry steam, the temperature of the steam will
rise, and the number of degrees rise in temperature is the 'degrees of superheat'. Thus, superheat is 'sensible' heat - that is, i t can be measured by a
thermometer.
6.9.1
Steam is a convenient and easily handled medium for heating, for driving
machinery, for cleaning, and for creating vacuum.
After water has reached the boiling point, further addition of heat will convert
water into the vapor state: that is, steam. During boiling there is no further
rise in temperature of the water, b u t the vaporization of the water uses up
heat. This added heat energy, which is not shown by a rise i n temperature, is
termed 'latent heat of vaporization', and varies with pressure.
Under normal atmospheric pressure (14.7 PSIA) pure water boils at 212 F.
Reduction of the pressure over the water will lower the boiling point. Increase
i n pressure raises the boiling point. Steam tables give boiling points corresponding to particular pressures.
FLASH STEAM
I n boiling one pound of water at atmospheric pressure (14.7 PSIA) 970.3 BTU
is absorbed. I f the steam condenses back into water (still at the boiling
temperature and 14.7 PSIA) i t will release exactly the amount of heat i t
absorbed on vaporizing.
The term 'saturated steam' refers t o both dry steam and wet steam, described
below. Steam tables give pressure and temperature data applicable t o dry and
to wet steam. Small amounts of air, carbon dioxide, etc., are present i n
steam from industrial boilers.
STEAM/WATER/ICE DIAGRAM
The data provided i n steam tables enable calculation of the quantity and
temperature of steam produced in 'flashing'.
CHART 6.3
Steam in a line will give up heat to the piping and surroundings, and will
gradually become 'wetter', its temperature remaining the same. The change of
state of part of the vapor to liquid gives heat to the piping without lowering
the temperature in the line. The water that forms is termed 'condensate'. I f
the line initially contains superheated steam, heat lost to the piping and
surroundings will first cause the steam to lose sensible heat until the steam
temperature drops to that of dry steam at the line pressure.
a
2
b
a
W
AIR I N STEAM
-H.OI
With both dry and wet steam, a certain pressure will correspond t o a certain
temperature. The temperature of the steam at various pressures can be found
in steam tables. If air is mixed with steam, this relationship between pressure
and temperature no longer holds. The more air that is admixed, the more
the temperature is reduced below that of steam at the same pressure. There
is no practicable way to separate air from steam (without condensation) once
i t is mixed.
removed
CHANGE OF STATE
DRY STEAM
Dry steam is a gas, consisting of water vapor only. Placed in contact with
water at the same temperature, dry steam will not condense, nor will more
steam form-liquid and vapor are i n equilibrium.
WET STEAM
6.9.2
Special liquid media such as Dowtherms (Dow Chemical Co.) and Therminols
(Monsanto Co.) can be boiled like water, but the same vapor temperatures as
steam are obtained at lower pressures. Heating systems using these liquids
are more complicated than steam systems, and experience with them is necessary i n order to design an efficient installation. However, the basic principles
of steam-heating systems apply.
Wet steam consists of water vapor and suspended water particles at the same
temperature as the vapor. Heating ability ('quality') varies with the percentage
of dry steam in the mixture (the water particles contain no latent heat of
vaporization). Like dry steam, wet steam is i n equilibrium with water at the
same temperature.
(1271
CHART
6.3
STEAM PIPING
6.10
6.10.1
Air in steam lines lowers the temperature for a given pressure, and calculated
rates of heating may not be met. See 6.9.1 under 'Air in steam'.
The most economic means for removing air from steam lines isautomatically
thru temperature-sensitive traps or traps fitted with temperature-sensitive airventing devices placed at points remote from the steam supply. When full
line temperature is attained the vent valves will close completely. See 6.10.7
under 'Temperature-sensitive (or thermostatic) traps'.
WHY PLACE VENTS AT REMOTE POINTS ?
On start-up, cold lines will be filled with air. Steam issuing from the source
will mix with some of this air, but will also act as a piston pushing air to the
remote end of each line.
6.10.2
Steam with entrained water droplets will form a dense water film on
heat transfer surfaces and interfere with heating
Condensate can be swept along by the rapidly-moving steam (at
120 ftlsec or more) and the high-velocity impact of slugs of water
with fittings, etc. (waterhammer) may cause erosion or damage
UTILIZING CONDENSATE
FIGURE 6.41
I n early steam systems, there was considerable waste of steam and condensate
after passing thru heating coils, etc., as steam was merely vented to the open
air. Later, the wastefulness of this resulted in closed steam lines from which
only the condensed steam was removed and then re-fed to the boiler. The r e
moval of condensate to atmospheric pressure was effected with traps-special
automatic discharge valves-see 6.10.7.
This was a much more efficient system, but it still wasted flash steam. On
passing thru the traps, the depressurized condensate boiled, generating lowerpressure steam. I n modern systems, this flash steam is used and the residual
condensate returned to the boiler.
6.10.3
This is an in-line device which provides better drying of steam being immediately fed t o equipment. A separator is shown i n figure 2.67. I t separates
droplets entrained in the steam which have been picked up from condensate
in the pipe and from the pipe walls, by means of one or more baffles (which
cause a large pressure drop). The collected liquid is piped t o a trap.
SLOPING & DRAINING STEAM & CONDENSATE LINES
6.10.4
6.10.5
L-J
FLASH
Driplegs are made from pipe and fittings. Figure 6.42 shows three methods of
construction, and table 6.10 suggests dripleg and valve sizes.
Low-temperature Condenrate
F I G U R E 6.42
DRIPLEG CONSTRUCTIONS
SCREWED O R
SOCKET-WELDED PIPING
B U T T - W E L D E D PIPING
RECEIVER
Bo~lar.tredSystem
C M d e n u t e Pump
TABLE 6.10
--
t"
TO
.c
:f
12
%
%
6
6
12 14
%
%
4
4
10
12
14
16
16
%
%
14
10
18
%
%
16
12
20
%
1
1
1
18
20
12
21
12
22
1
1
1
1
24
12
24
1
1
1
L-B 2
D L
PIPING TO
TO TRAP
5 E- g
N
BLOWDOWN
VALVE
~ $ 5
- .G > "
.a &a za
PLUG
float trap is able t o discharge condensate continuously, but this trap will not
discharge air unless fitted with a temperature-sensitive vent (the temperature
limitation of the vent should be checked). Float traps sometimes may fail
from severe waterhammer. The inverted bucket trap (see 3.1.9) is probably
the most-used type. The trap is open when cold, but will not discharge
large quantities of air at startup unless the bucket is fitted with a temperaturesensitive vent. The action in discharging condensate is rapid. Steam will be
discharged if the trap loses its priming water due to an upstream valve being
opened; refer to note ( 9 ) i n the key to figure 6.43. Inverted bucket traps
will operate at pressures down to 114 PSIG.
Flgure 2 7 0 shows
dripleg construction
6.10.6
I n almost every steam-heating system where condensate is recovered the trapped condensate has to be lifted to a condensate header and run t o a boiler
feedwater tank, either directly or via a receiver. Each PSI of steam pressure
behind a trap can lift the condensate about two feet vertically. The pressure
available for lifting the condensate is the pressure difference between the
steam and condensate lines less any pressure drop over pipe, valves, fittings,
trap, etc.
STEAM TRAPS
FLASHING
6.10.8
6.10.7
The purpose of fitting traps to steam lines is to obtain fast heating of systems
and equipment by freeing the steam lines of condensate and air. A steam
trap is a valve device able t o discharge condensate from a steam line without
also discharging steam. A secondary duty is t o discharge air-at start-up, lines
are full of air which has t o be flushed out by the steam, and in continuous
operation a small amount of air and non-condensible gases introduced in the
boiler feedwater have also to be vented.
Some traps have built-in strainers to give protection from dirt and scale which
may cause the trap to jam in an open position. Traps are also available with
checking features to safeguard against backflow of condensate. Refer to the
manufacturers' catalogs for details.
Choosing a trap from the many designs should be based on the trap's ability
to operate with minimal maintenance, and on its cost. To reduce inventory
and aid maintenance, the minimum number of types of trap should be used
in a plant. The assistance of manufacturers' representatives should be sought
before trap types and sizes are selected.
The hotter the steam line and the colder the condensate discharge line, the
more flashing will take place; i t can be severe if the condensate comes from
high pressure steam. Only part of the condensate forms steam. However, if
the header is inadequately w e d to cope wlth tile quantity of flash steam
produced and backpressure builds up, waterhammer can result.
Often, where a trap is run to a drain, a lot of steam seems to be passing thru
the trap, but this is usually only from condensate flashing.
6.10.9
TABLE
6.1 0
Ill
DRIPLEG FROM STEAM HEADER OR LlNE TO EOUIPMENT OR LlNE FROM STEAM FED
EOUIPMENT
121
(31
14)
U R l P L k L FROM STLAM
/LI~E
OR LPLIPMENT
FIGURE 6.44
SLOPE L I N E T O
ASSIST U R A l N l N G
I N FREEZING
SYMBOL
SIGHT GLASS ALLOWS VISUAL CHECK THAT TRAP IS DISCHARGING CORRECTLY INTO
A PRESSURIZED CONDENSATE RETURN LINE. BUT IS SELDOM USED BECAUSE THE GLASS
M A Y ERODE. PRESENTING A RISK OF EXPLOSION
IT IS BETTER TO PROVIDE
Start-ups are infrequent and with more than a few degrees of superheat i t is
unnecessary t o trap a system which is continuously operated. These superheated steam lines can operate with driplegs only, and are usually fitted
with a blowdown line having two valves so that condensate can be manually
released from the dripleg after startup.
A superheated steam supply to an intermittently operated piece of equipment will require trapping directly before the controlling valve for the equipment, as the temperature will drop at times allowing condensate to form.
Rotary Joint
6.10.10
FIGURE 6.45
\
7
ROTATING DRUM
Insulation and steam or electric tracing of the trap and its piping may also
be required i n freezing environments. Temperature-sensitive and impulse traps
are not subject to freezing trouble if mounted correctly, so that the trap
can drain. Bucket traps are always mounted with the bucket vertical and a
type with top inlet and bottom outlet should be chosen, unless the trap can
be drained b y fitting an automatic drain.
8
6.10.11
Figures 6.43 thru 6.45 are a guide t o piping traps from driplegs, lines,
vessels, etc.
Unless instructed otherwise, pipe, valves and fittings will be the same
size as the trap connections, b u t not smaller than 314 in.
Traps are normally fitted at a level lower than the equipment or dripleg
that they serve
Trap each item of equipment using steam separately, even if the steam
pressure is common
Provide driplegs (and traps on all steam lines with little or no superheat)
at low points before or at the bottom of risers, at pockets and other
places where condensate collects on starting up a cold system. Table
6.10 gives dripleg sizes
If condensate is continuously discharg~ngto an open drain in an i n side installation a personnel hazard or oblectionable atmosphere may
be created. To correct this, discharge piping can be connected to an
exhaust stack venting to atmosphere and a connection to the maln
drain provided, as in figure 6.46
FIGURE 6.46
VENT S T A C K
FIGURES
6.43-6.46
Vent Stack
Condensate from
HYDROSTATIC TESTING
6.1 1
After piping has been erected, i t is often necessary to subject the system to a
hydrostatic test to see if there is any leakage. In compliance with the
applicable code, this consists of filling the lines with water or other liquid,
closing the line, applying test pressure, and observing how well pressure i s
maintained for a specified time, while searching for leaks.
6.11.1
Vents are needed to let gas (usually air) in and out of systems. When a line or
vessel cools, the pressure drops and creates a partial vacuum which can cause
syphoning or prevent draining When pressure rises in storage tanks due t o an
increase i n temperature, i t is necessary t o release excess pressure. Air must
also be released from tanks to allow filling, and admitted t o permit draining or
pumping out liquids.
As the test pressure is greater than the operating pressure of the system, it is
necessary t o protect equipment and instruments by closing all relevant valves.
Vessels and equipment usually are supplied with a certificate of code compliance. After testing, the valved drains are opened and the vent plugs temporarily removed t o allow air into the piping for complete drain~ng.
Unless air is removed from fuel lines to burners, flame fading can result. In
steam lines, air reduces heating efficiency.
IDESIGN
6.11.2
VENTS AND DRAINS FOR HYDROSTATIC TEST ARE INDICATED ON PIPING DRAWINGS BY THE SYMBOLS*
I F THE VENT OR DRAIN IS FOR ANOTHER PURPOSE. IT IS DETAILED ON THE PIPING DRAWING. OR THE DESIGN
PURPOSE
HYDROSTATIC TEST
USED
OPERATION OF PROCESS
IVALVES
VALVED VENTS AND DRAINS ARE USUALLY EOUIPPED WITH GATE VALVES. BUT GLOBE VALVES MAY
BE USED FOR TIGHTER CLOSURE
HAZARDOUS FLUIDS
V A L V E S A R E AVAILABLE WITH
a,,
'how
8"
TEE THRDD
24 m d 2 5
NIPOLET TL
TEE THRDD
II
PLUG
CAP THRDD
NIPPPOE-TOE
TEE.SW
Hot.
fc..
DVP. O l
l r-l
TEE S H
SOCKOLET
run. I rwir c r
.no
u
,-
m* b d I"
bun
hlPP;BE
I-,
PLUG
INTEGRALNIPPPE'
PLUG
L]
Sake, End
Threadad End
NIPOLET P E
SOCKOLET
.*.V A L V U , W d n
,TO on","
r*.
I) Ih<
CAP ' n R D O
'
.n.
m q n In n l w n n., .t m m m
r * l I I
Wlr
on t*.
Mu-
0,
!k"lW*<
Positions of the required vent and drain points are established on the piping
drawings. (P&lO1s will show only process vents, such as vacuum breakers,
and process drains.) Refer t o figure 6.47 for construction details.
VENTING GASES
R E L I E V I N G PRESSURE-LIQUIDS
6.1 1.3
Quick-opening vents of ample size are needed for gases. Safety and safetyrelief valves are the usual venting means. See 3.1.9 for pressure-relieving
devices, and 6.1.3, under 'Piping safety and relief valves'.
RELIEF HEADERS
If air for distribution has not been dried, distribution lines should be sloped
toward points of use and drains: lines carrying dried air need not be sloped.
Sloping is discussed in 6.2.6.
SEPARATOR
FIGURE 6.48
ORIPLEQ
MANUALDRAIN AT
E N D O F AIR LlNE
1 F l g u r e 2.70 shows
construction. Table 6.10
glves slzes sultable for
drlplsgs
8LOWDWN
VALVE
VALVE
1 0 ORIlN
1 0 DRAiN
6.13
ILWDOWN
6.12.1
:::
(2)
Headers should be sized to handle adequately the large amounts of vapor and
liquid that may be discharged during major mishap. Relief headers taken
to knockout drums, receivers or incinerators, are normally sloped, Refer to
6.2.6 and figure 6.3, showing the preferred location of a relief header on a
piperack.
6.11.4
Air has a moisture content which is partially carried thru the compressing
and cooling stages. I t is this moisture that tends to separate, together with
any oil, which may have been picked up by the air in passing thru the
compressor.
(1)
-----
Gases which offer no serious hazard after some dilution with air may be
vented t o atmosphere by means ensuring that no direct inhalation can occur.
I f a (combustible) gas is toxic or has a bad odor, i t may be piped t o an
incinerator or flarestack, and destroyed b y burning.
DRAINING COMPRESSED.AIR LINES
6.12
1 0 DRAIN
I1331
FEURES
6.47 & 6.48
6.14
SOME GUIDELINES
REFERENCES
'Fire hazard properties of flammable liquids, gases, volatile solids'.
NFPA 325M
1984.
Isolate flammable liquid facilities so that they do not endanger important buildings or equipment. I n main buildings, isolate from other
areas by firewalls or fire-resistive partitions, with fire doors or openlngs
and with means of drainage
1985.
'Guide for fighting fire in and around petroleum storage tanks'. 1980
API publication 2021
NFPA address: Batterymarch Park, Quincy MA 02269
TANK SPACINGS (NFPA)
CONDITIONS
FLAMMABLE or
COMBUSTIBLE LIQUID
STORAGE TANKS
(Not exceeding 150 ft. dia.)
TABLE 6.11
MINIMUM INTER.TANK CLEARANCE
3 ft
TANKS surrounded by
other Tanks
Whichever is greater:3ft
(Sum of diameters of adjacent tanks116
CRUDE PETROLEUM
126,000 gal max tank size
Noncongested locale
UNSTABLE FLAMMABLE and
UNSTABLE COMBUSTIBLE
LIQUID STORAGE TANKS
20 f t
NOTE:
If LPG
i s smaller than
Authority Limit
[I341
- --
--
6.15
6.15.1
VERTICAL SPACING
BETWEEN FLOOR 5 CEILING
;:;-:,;"'.:.'
.,
'
.'.'.:.:..'.'...:'
.. . ....:,::.
.... ,,-..
..
,'..
"
&. *'
FIGURE 6.50
---
1 ft
3-4 f t
10-12 f t
6.15.2
FIGURES
6.15.3
RELATION TO PROCESS
TABLE
6.1 1
7.1
(2)
Codes often supply the substance for Federal, State, and Municipal
safety regulations. However, the US Federal Government may, as
needed, devise its own regulations, which are sometimes in the form
of a code.
7.3
Not all USA standards and codes are issued directly by the Institute. The
American Society of Mechanical Engineers, the Instrument Society of America, and several other organizations issue standards and codes that applv
to piping. Table 7.1 lists the principal sources.
7.2
(4)
The American Standards Association was founded in 1918 to authorize national standards originating from five major engineering societies. Previously
a chaotic situation had arisen as many societies and trade associations had
been issuing individual standards which sometimes overlapped. In 1967, the
name of the ASA was changed to the USA Standards Institute. and in 1969
a second change was made, to American National Standards Institute.
Standards previously issued under the prefixes 'ASA' and 'USASI' are now
prefixed 'ANSI'.
The terms 'standard' and 'code' have become al most interchangeable, but
documents are termed codes when they cover a broad area, have governmental acceptance, and can form a basis for legal obligations. 'Recommendations' document advisable practice. 'Shall' in the wording of standards
and codes denotes a requirement or obligation, and 'should' implies recommendation.
(1)
WHOISSUESSTANDARDS?
Proven engi neering practices form the basis of standards and codes, so that
they embody minimum requirements for selection of material, dimensions,
design, erection, testing, and inspection, to ensure the safety of piping
systems. Periodic revisions are made to reflect developments in the industry.
(3)
__ _ _
~_
4_.
.._
..
--
..
--
A
A
ASS
AGA
AISI
ANSI
API
ASTM
AWS
AWWA
E
(1)
Air
(2)
Absolute
Absolute
American Gas Association
American Iron and Steel Institute
American National Standards Institute
American Petroleum Institute
American Society for Testing and Materials
American Welding Society
American Waterworks Association
B
BBL
BC
BLE
BLK
BLVD
BOP
BS
BTU
BW
Barrel
Bolt circle
Beveled large end
Black
Beveled
Bottom [of outside] of pipe. Used for
pipe support location
British Standard
British thermal unit
(1 )
Butt weld
(2)
Butt welded
E
ECN
EFW
ELL
ERW
F
F
F&D
FAHR
FBW
FCN
FD&SF
FE
FF
FLG
FLGD
FOB
C
CENT
CFM
CHU
CI
CM
Cr
CS
CSC
CSO
CTR
CU
(1)
Centigrade, or Celsius
(2)
Condensate
Centigrade
Cubic feet per minute
Centigrade heat unit
Cast iron
Centimeter
Chromium
( 1) Carbon steel
(2)
Cold spring
Car-sealed closed. Denotes a valve to be
locked in the closed position under all
circumstances other than repair to adjacent piping
Car-sealed open. See CSC
Center
Cubic
DEG
DIA
DIN
DO
DRG
DWG
FOT
FRP
FS
FW
Degree
Diameter
Deutsche Industrie Norm [German standard]
Drawing office
Drawing. [Not preferred)
Drawing
Fahrenheit
Faced and drilled
Fahrenheit
Furnace-butt-welded
Field change number
Faced, drilled and spot-faced
Flanged end
(1)
Hat facetdl
(2)
Full face [of gasket]
(3)
Flange face [dimensioning]
Flange
Flanged
(1)
Flat on bottom. [Indicates orientation of eccentric reducer]
(2)
Freight on board. [I nd icates location of supply of vendor's freight at the
stated price]
(3)
Free on board. [Indicates location
of supply of vendor's freight]
Flat on top. [Indicates orientation of
eccentric reducer]
[Glass-] fiber reinforced pipe
Forged steel
Field weld
G
G
GAL
GALV
GPH
GPM
Gas
(2)
Grade
(3)
Gram
Gallon
Galvanized
Gallons per hour
Gallon per minute
(1)
H
H
East
Engineering change number
Electric-fusion-welded
Elbow
Electr ic-resistance-welded
HEX
Hg
HPT
HR
(1)
Horizontal
(2)
Hour
Hexagon (al)
Mercury
Hose-pipe thread
Hour
I
IE
Invert elevation
(141 )
10
IMP
IPS
IS
ISO
IS&Y
(1 )
(2)
K
K
kg
L
l
lB,lb
IT
lR
liquid
Pound weight
Light-wall [of Pipe]
Long radius. [Of Elbow]
M
M
MACH
MATl
MAWP
MAX
MCC
M/C
MFR
MI
MIN
mm
Mo
MSS
(1)
(2)
Meter
Mega, times one million, 1000000.
[On old drawings, x 1000]
Machined
Material
Maximum allowable working pressure
Maximum
Motor control center
Machine
Manufacturer
Malleable iron
(1)
Minimum
(2)
Minute. [Of time)
Millimeter
Molybdenum
Manufacturers' Standardization Society
of the Valve and Fittings Industry
N
N
NC
NEMA
Ni
NIC
NO
NPSC
NPSF
NPSH
NPSI
NPSl
NPSM
North
Normally closed
National Electrical Manu factu rers' Assn.
Nickel
Not in contract
Normally open
2.5.5
2.5.5
(1)
Net positive suction head.[3.2.1]
(2) 2.5.5
2.5.5
2.5.5
2.5.5
TABLES
7.1 J -7.14
Part II
II
Piping Charts & Tables