PFI ES 24 Pipe Bending and Tollerances
PFI ES 24 Pipe Bending and Tollerances
PFI ES 24 Pipe Bending and Tollerances
Prepared by
Pipe Fabrication Institute Engineering Committee
Copyright by
WEB SITE
www.pfi-institute.org
--``,``,,``,`````````,``,`,````,-`-`,,`,,`,`,,`---
METRIC CONVERSIONS
The conversion of quantities between systems of units involves a determination of the number of significant digits to be retained.
All conversions depend upon the intended precision of the original quantity and are rounded to the appropriate accuracy.
Pipe sizes together with applicable wall thicknesses are not shown with metric equivalents.
The SI (metric) values where included with the customary U.S. values in this Standard are the rounded equivalents of the U.S.
values and are for reference only.
Metric units were derived utilizing the following conversion factor:
FIGURE 2.1
--``,``,,``,`````````,``,`,````,-`-`,,`,,`,`,,`---
3.3 While the bending equipment used in many of the HEATING DEVICE
methods is generically the same, there may be
differences in bending procedures, material
allowances, hold and pull legs, wall thickness,
etc., between bending fabricators.
--``,``,,``,`````````,``,`,````,-`-`,,`,,`,`,,`---
heats a narrow circumferential band around
the pipe to the appropriate bending
temperature. When this temperature is
reached, the pipe is continuously moved
through the heating coil while a bending
moment is applied to the heated area. After
passing through the coil, the pipe may be
RADIUS STOPS either forced or naturally cooled as required
(OPTIONAL)
by the appropriate qualified bending
PULLING DEVICE
procedure.
4. Welds in Bends
4.1 In some instances it is not practical to utilize pipe
ROTATING BEND DIE of sufficient length to satisfy the required arc
length of the bend. When it becomes necessary to
join lengths of pipe resulting in a circumferential
FIGURE 3.5.1
butt weld in the arc of a pipe bend, the following
ROTARY DRAW BENDING
practices should be considered:
3.5.2 RAM BENDING:
In ram bending, the pipe is held by two 4.1.1 Pipes to be welded should be selected to
supporting dies and a force is applied by provide the best uniformity possible at the
means of a hydraulic ram to a forming shoe mating ends. Pipe wall thickness shall not be
located at the center of the workpiece. The less than the design minimum plus bend
supporting dies rotate on their mounting thinning allowance (see section 7.0).
pins so that they follow the pipe and 4.1.2 End preparation for welding shall be in
maintain external support throughout the accordance with the qualified welding
operation. procedure to be used. Internal counterboring
should be avoided wherever possible. During
SUPPORT
DIE
fit-up of the joint, the pipes should be rotated
HYDRAULIC RAM
or aligned as necessary to provide the least
amount of I.D. and/or O.D. mismatch and the
best transition across the weld.
4.1.3 The welding procedure must be qualified in
accordance with the governing Code for the
FORMING SHOE thermal exposures, (if any) excepted in
bending and heat treatment.
4.1.4 After completion of the circumferential butt
FIGURE 3.5.2 weld, but before bending, the O.D. and I.D.
RAM BENDING (where accessible) of the weld should be
ground to remove excess weld reinforcement
3.5.3 ROLL BENDING: and blended smoothly into the base metal.
In roll bending, three forming rolls of
approximately the same diameter arranged in 4.1.5 It is good practice to examine the
a pyramid are used. The two fixed rolls circumferential butt weld by radiography
oppose the adjustable center roll. The pipe is prior to and after bending, whether or not
passed through the rolls with the position of such radiography is required by the
the adjustable roll controlling the bend applicable Code.
--``,``,,``,`````````,``,`,````,-`-`,,`,,`,`,,`---
radius.
TA MA
RO
W
7 LL M manufacturing tolerance, and tm is derived from
M
B A
RA
I-
6 ULT
WIT
HM
I-BAL
L equation (3) of B31.1, par. 104.1.2. The most
5 AW MULT
Y DR AW WITH IE conservative values over that range of pipe sizes
R D
4 TAR RY D IPER
RO ROTA ND W and wall thicknesses where used.
3 REL A
MAND
2
1 TABLE 7.2.1
0 FURNACE BENDING
0 25 50 75 100 125 150
Bend Minimum Thickness Factored
FIGURE 6.8.1 Radius Prior to Bending Thickness
COLD BENDING RANGE
6D 1.06 tm 1.03 tm
7. Material Allowances 5D 1.08 tm 1.04 tm
4D 1.14 tm 1.09 tm
7.1 The following recommendations for material 3D 1.25 tm 1.19 tm
allowances will vary with the bending method,
material, pipe size, bend radius and the bend TABLE 7.2.2
fabricator's equipment. It is suggested that the INDUCTION AND INCREMENTAL BENDING
purchaser contact the fabricator for specific
information. Bend Minimum Thickness Factored
Radius Prior to Bending Thickness
7.2 To compensate for wall thinning from bending, the
second column, (“Minimum Thickness Prior to 6Dn 1.06 tm 1.03 tm
Bending”), in Tables 7.2.1, 7.2.2, 7.2.3, and 7.2.4 can 5Dn 1.08 tm 1.04 tm
be used as a guide for ordering pipe for the appropriate 4Dn 1.10 tm 1.05 tm
process. ASME B31.1 Power Piping, equations 3Dn 1.14 tm 1.08 tm
102.4.5(3B, 3C & 3E), and B31.3 Process Piping, 2Dn 1.22 tm 1.13 tm
equation 304.2.1(3c & 3e) define a minimum thickness 1.5Dn 1.30 tm 1.19 tm
at the extrados of the bend that is less than the
minimum thickness required for straight pipe. TABLE 7.2.3
Conversely, the minimum thickness for the intrados of
--``,``,,``,`````````,``,`,````,-`-`,,`,,`,`,,`---
Nominal pipe size 1" thru 2" 2½" thru 3½" 4" thru 48"
Pulling End 6" 8" 2D (10" min)
Holding End 6" 8" 1.5D (10" min)
Tangent Between Bends (Tm) 6" 9" 1D (12" min)*
*Note: 9" min for 4" pipe. 10" min for 5" pipe.
TABLE 7.5.1
MINIMUM TANGENT LENGTHS FOR FURNACE BENDS
R
various processes are given in Tables 7.5.1, 7.5.2,
and 7.5.3. Definition of these tangent lengths can
R
TABLE 7.5.3
MINIMUM TANGENT LENGTHS FOR COLD BENDING
--``,``,,``,`````````,``,`,````,-`-`,,`,,`,`,,`---
Radius of
Bend (Dim C) Plane of Bend
(Angle between
Two Bend Planes)
Ovality Tolerence :
Minor The difference
Dia. between the major
e
n
and minor axis (percent)
Flat Plane iL
tn Nom. Major
of Bend e
g Dia. Dia.
n
a
T
Degree of
Bend
Ovality
(2 x size)
Tangent Line
Elevation
Figure 9.3
Tolerences
--``,``,,``,`````````,``,`,````,-`-`,,`,,`,`,,`---
Technical Bulletins
TB1 R13 Pressure - Temperature Ratings of Seamless Pipe Used in Power Plant Piping Systems - ELECTRONIC VERSION
TB3 R13 Guidelines Clarifying Relationships and Design Engineering Responsibilities Between Purchasers’ Engineers and Pipe Fabricator or Pipe
Fabricator or Pipe Fabricator Erector
TB5 R13 Information Required for the Bidding of Pipe Fabrication
TB7 R04 Guidelines for Fabrication and Installation of Stainless Steel High Purity Distribution Systems
TB8 R13 Recommended practice for the fabrication of polyvinylidene fluoride (PVDF) piping
TB9 R13 Customary Fitting, Forging, Plate and Bar Materials used with Pipe
ELECTRONIC VERSION
CHARTER MEMBERS
CONTRACTOR MEMBERS
ASSOCIATE MEMBERS
AFFILIATE MEMBERS
HONORARY MEMBERS
PFI Standards and Technical Bulletins are published to serve proven needs of the pipe
fabricating industry at the design level and in actual shop operations. Hence, such needs
are continually considered and reviewed by the Engineering Committee of the Pipe
Fabrication Institute to provide recommended procedures, which have been demonstrated
by collective experiences to fulfill requirements in a manner for Code compliance.
However, as the PFI Standards are for minimum requirements the designer or fabricator
always has the option of specifying supplementary conditions in the form of requirements
beyond the scope of the PFI publications.
--``,``,,``,`````````,``,`,````,-`-`,,`,,`,`,,`---