BCGA CP4 - Industrial Gas Cylinders and Gas Distribution
BCGA CP4 - Industrial Gas Cylinders and Gas Distribution
BCGA CP4 - Industrial Gas Cylinders and Gas Distribution
|
|
.
|
\
| +
+ = 21 . 0
Vr
n L
0.21n
21 . 0 C
t
e - 1
m
t -
where C
t
= oxygen concentration at time t
L = gas release m/h
V
r
= room volume m
n = air changes per hour
t = time gas has flowed in hours
m =
Vr n L
Vr
+
and for long periods (t tending to infinity):
( ) n Vr L
n 0.21 Vr
C
+
=
approximately
BCGA CP4 Rev 3 2005 18
5.2.3 Example Calculations
5.2.3.1 Example Calculation 1A
One nitrogen 50 litre cylinder charged to 200 bar being used in a workplace
with a free air volume of 75 m
3
.
VR = 75 m
3
1000
200 50
cylinder in gas of Volume
= = 9.52 m
3
( 52 . 9 75 21 . 0 = O V ) = 13.75 m
3
Resulting oxygen concentration (C
ox
) =
75
75 . 13 100
= 18.3%
This oxygen concentration is below the minimum workplace concentration
for normal working recommended by the BCGA. However, the
instantaneous release of the whole contents of a compressed gas cylinder is
an almost inconceivable event, and not foreseeable as part of normal
working. Thus specific preventative measures are unlikely to be required in
this case.
5.2.3.2 Example Calculation 1B
One liquid nitrogen 50 litre tank being used in a workplace with a free air
volume of 75 m
3
.
VR = 75 m
3
|
|
.
|
\
|
|
.
|
\
|
=
1000
683 50
75 21 . 0 O V = = 8.58 m ( 15 . 34 75 21 . 0 )
3
Resulting oxygen concentration C
ox
=
75
58 . 8 100
= 11.44%
This oxygen concentration is clearly below the minimum recommended by
the BCGA and would represent an immediate threat to life. The
instantaneous loss of the full contents of a 50 litre liquid tank is a very
unlikely event, and the probability that this could occur needs to be assessed
for the specific activity being undertaken. Preventative measures will be
necessary where such a loss of contents is reasonably foreseeable.
BCGA CP4 Rev 3 2005 19
5.2.3.3 Example Calculation 1C :
One 6.35kg (14lb) carbon dioxide cylinder being used in a workplace with a
free air volume of 75 m
3
.
VR = 75 m
3
VO= 0.21(75-((6.35 x 535)/1000)) =0.21(75-3.4) =15.0 m
3
Resulting oxygen concentration (C
ox
) = (100 x 15)/75 = 20%
This oxygen concentration is above the minimum recommended by the
BCGA. However carbon dioxide is mildly toxic and therefore the HSE
have defined an occupational exposure limit of 0.5% averaged over 8 hours,
with a maximum exposure of 1.5% for short periods of 15 minutes.
The volume of carbon dioxide from this 6.35kg cylinder could produce a
concentration of 4.5% in case of complete loss via, for example, a bursting
disc failure. This would produce a dangerous atmosphere and preventive
measures are necessary.
5.2.3.4 Example Calculation 2
An inert gas is being used in a work place with a free air volume of 18 m
3
,
the gas flow rate is 1.1 m
3
/h, the air changes are 0.4 per hour and the time
taken to complete the job is 2 hours.
To establish the effect of this activity on the workplace atmosphere after 2
hours the following formula is used:
Ct = 0.21+
Vr
n L
n 21 . 0 21 . 0
e - 1
m
t
-
where: Ct
= oxygen concentration at time t, which can be multiplied
by 100 to give the % concentration
L = 1.1
VR = 18
n = 0.4
t = 2
m = 17 . 2
L
Vr
=
+ nVr
Ct
= 0.19324
BCGA CP4 Rev 3 2005 20
This is the concentration of the oxygen in the air.
The oxygen concentration in the workplace has dropped to 19.324%, which
is above the minimum recommended by the BCGA and above the level
where the BCGA recommends evacuation of the workplace (18%),
therefore preventative measures will probably not need to be taken.
5.2.3.5 Example calculation 3
In the case of flammable gases, fixed manifolds should not be sited inside
buildings. Hydrogen for example, has a very wide flammability band in air
and in the event of a relatively small leak can create a flammable
atmosphere in an enclosed or restricted space.
Consider a 50 litre, 200 bar cylinder of hydrogen in a room of internal
volume 75 m
3
. The volume of gas contained in the cylinder is 8.796 m
3
,
measured at 1.013 bar and 15C.
The concentration of hydrogen in the room is thus 8.796/75 X 100% =
11.7%
As in example calculation 1A the instantaneous release of the complete
contents of the cylinder is not normally a reasonably foreseeable event,
however the result is over 10 times the suggested maximum acceptable gas
concentration (25% of LEL, which is for hydrogen in air 4%, giving a
maximum allowable concentration of 1%). There is therefore sufficient gas
to cause a dangerous situation, and a detailed risk assessment will be
needed to decide how to make the situation acceptable, for example by
defining the room as a zoned area, requiring that all sources of ignition and
electrical equipment be designed accordingly.
Where relief valves or bursting discs are fitted to manifolds, the outlets shall be
piped away to a safe area. The outlet of any vent line, or outlet line fitted to a relief
device shall discharge into a safe area, which shall be construed as areas where gases
may be discharged safely without creating an asphyxiant, flammable or oxygen
enriched environment or where venting gas could impinge on materials or in
proximity to people such as to create a hazard. Vent outlet points should therefore
be remote from where people normally pass or gather, and not discharge towards
windows, doors, air intakes or other hazards identified in the safety distances table.
The number of cylinders in the room should be the minimum necessary for the
operation and safety distances between different types of gases must be observed.
Where flammable gas manifolds are installed, electrical systems in the manifold
room shall be in accordance with the recommendations of BS EN 60079 (56).
Heating should preferably be by steam or hot water.
Flammable gas manifolds and pipework shall be electrically earthed in accordance
with the requirements of BS EN 60079 (56). Manifolds and pipework carrying other
BCGA CP4 Rev 3 2005 21
gases should be cross-bonded to earth in accordance with the recommendations of
BS 7671 (45) and of the current IEE Wiring Regulations.
The installation shall be clearly identified with the product name and hazards as per
the requirements of The Health and Safety (Safety Signs & Signals Regulations) SI
1996 No 341 (28), either on the outside of a manifold room or adjacent to an outside
installation.
5.3 Use Points
Where there is a perceived risk at the use point from a gas escape a risk assessment
shall be conducted to establish necessary controls.
5.4 Distribution Pipework Design
5.4.1 Pressure Drop
For most conditions and gases within the scope of this Code, pressure drop
(at 15
o
C) can be estimated from the formula:
5
g
2
2
1 1
d
S L Q 32
P P P =
where:
P = pressure drop bar
P
1
= inlet pressure bar absolute
Q = flow m
3
/h measured at 15
o
C & 1013
mbar
L = pipe length m
S
g
= specific gravity air = 1
d = internal diameter of pipe mm
Pressure drop will be increased due to fittings and components installed in
the pipework. The usual method of calculating pressure drop, due to
fittings and components, is to increase theoretically the pipe length to
account for the fittings as shown in Table 3.
BCGA CP4 Rev 3 2005 22
Table 3 Calculating pressure drop due to fittings and components installed in
pipework
Equivalent length of straight pipe (m)
Pipe size
mm -
nominal
Valves (Wide open) Fittings
Ball
Globe or
Diaphragm
Angle
Tee
(Through)
Tee
(Branch)
Elbow
10 0. 3 4. 0 2. 5 0. 2 0. 9 0. 4
12 0. 3 4. 0 2. 5 0. 2 0. 9 0. 4
15/16 0. 3 6. 0 3. 1 0. 3 1. 0 0. 5
20/22 0. 6 6. 0 4. 0 0. 6 1. 9 0. 7
25/28 0. 9 9. 0 5. 0 0. 6 1. 9 0. 9
42 1.2 14.0 7.5 0.9 3.0 1.2
54 1.4 16.0 9.0 1.1 3.5 1.4
Allowance should be made at the design stage for future extensions.
NB The calculations for pressure drop are applicable to metallic piping only
and provide indicative values.
5.4.2 Velocity
For materials of construction of oxygen systems, the velocity of the gas
must be kept below a defined value See Appendix 1.
For most gases and conditions covered by this code, velocity may be
calculated using the following formula:
m/s
1.013) (P D
Q 358
V
2
+
=
where: Q is the gas flow-rate in cubic metres per hour measured at 15
o
C,
1013 mbar
D is the internal diameter of the pipe : mm
P is the inlet pressure : barg
BCGA CP4 Rev 3 2005 23
6 MATERIAL & COMPONENT SELECTION
6.1 Materials of Construction
For the specific gases covered by this code the suitable materials are detailed in
Appendices 1 to 9.
6.2 Flexible Hose Assemblies
Flexible hose assemblies shall have end fittings permanently attached and where
used on flammable gas systems be electrically conductive with a resistance not
exceeding 10
6
ohms to give protection against electrostatic charging.
They shall be suitable for the design pressure, compatible with the service gas and
the length and diameter shall be kept to a minimum. Where the pressure exceeds 40
barg anti-whip wires shall be fitted to prevent injury to personnel in the event of a
hose failure.
Hose assemblies shall conform to BS EN ISO 14113 (62) or an equivalent standard.
6.3 Pigtail
Typically this is made from 90/10 cupro/nickel or other materials suitable for the gas
and pressure.
6.4 Manifold
Typically this is made from 90/10 cupro/nickel or other materials suitable for the gas
and pressure.
6.5 Regulators
Regulators shall be suitable for the particular gas service and it is recommended that
they be suitably labelled. They shall be suitable for the design pressure and flow
rate and shall comply with European or British Standards where appropriate (e.g.
BS EN ISO 7291 (60), BS EN ISO 2503 (58)).
6.6 Pressure Gauges
Pressure gauges shall conform to BS EN 562 (50) or BS EN 837 Part 1 (52) for the
operating requirements of the particular gas service.
6.7 Pressure Relief Devices
Pressure relief valves shall conform to BS 6759 (44) or an equivalent design
standard and shall be so sized that with the valve fully open the pressure in the
system cannot exceed the design pressure. A momentary over-pressure not
exceeding 10% of the set pressure is permitted to allow for the lifting characteristics
of the valve.
BCGA CP4 Rev 3 2005 24
Bursting discs shall conform to BS EN ISO 4126 (59) or an equivalent design
standard. When fitted alone bursting discs shall be selected so that the pressure
rating taking into account maximum tolerance, will not allow the pressure in the
system to exceed the design pressure by more than 10%.
Pressure relief devices shall be properly secured. Relief device outlets shall be sited
to relieve in a safe area. Where vent pipes are used, they shall be adequately sized to
relieve the flow rate, be securely anchored to prevent movement and sited to
discharge to a safe place.
Certification for safety devices shall be provided by the supplier.
6.8 Isolation Valves
Isolation valves shall be designed for positive shut-off and should be suitably
identified by type for pressure rating, direction of flow and gas service.
Specific gas service restrictions are detailed in Appendix 1-9.
Isolation valves should be fitted at strategic points on all main and branch lines so as
to be readily accessible for emergency isolation.
6.9 Non-return Valves
Non-return valves should be capable of passing the required flow rate without
oscillation or excessive pressure drop.
Consideration shall be given to the required performance capability of a non-return
valve with respect to the specific application including cracking pressure, seat
leakage and reseating pressure. This is especially important where cross or backfeed
contamination can occur. Where non-return valves are used, for example in multi-
cylinder manifolds, primarily as safety devices to prevent high pressure gas flowing
back through open-ended flexible hoses, absolute leak-tightness against back flow
may not be required.
6.10 Flashback Arrestors
Flashback arrestors shall be suitable for the required flow requirements and conform
to BS EN 730 (51).
6.11 Filters
Filters should be installed to protect equipment from particles, and should be
compatible with gas and pressure. Additional consideration shall be given to the
filtration requirements of oxygen systems to prevent the possibility of loose particles
forming ignition sources through impingement or frictional heating.
BCGA CP4 Rev 3 2005 25
7 CONSTRUCTION, INSTALLATION AND TEST
7.1 Pipe bends
Bends shall have the same design strength as straight pipe sections.
Pipes should have a minimum bend radius of 3D (where D is the nominal pipe bore).
Fabricated bends shall show no signs of buckling, cracking or other defects.
7.2 Flanges and fixings
Flanges shall conform to a recognised standard such as BS 1560 (35) or BS EN 1515
(53) in respect of material, dimensions and drilling and be suitable for the duty for
which they are installed.
Nuts and bolts shall conform to a recognised national standard such as BS EN 1515
(53) and be suitable for the duty for which they are installed. Bolts and stud bolts
shall extend completely through the nuts.
7.3 Jointing Materials
The design shall specify the joint sealing material to be used. Jointing materials
shall be capable of withstanding the maximum pressure and maintaining their
chemical and physical properties at any temperature which may be experienced in
service.
All types of jointing material shall be suitable for the particular gas service.
PTFE tape for use in oxygen service shall be of degreased quality to BS 7786 (46).
Asbestos based materials shall not be used.
7.4 Pipe Fittings
Pipe fittings shall be capable of withstanding the system design pressure and shall be
compatible with the service gas.
7.5 Compression fittings
Only compression fittings designed and approved for the specific gas application
shall be used (this excludes domestic plumbing fittings). Compression fittings
should not be used in systems where they may be exposed to wide temperature
variations. They should be confined to the installation of instrument lines and
similar small bore connections up to 15mm. Where this method of jointing is used,
the requirements of BS 8313 (47) must still be observed in relation to routing of
pipework through ducts, roof voids and similar confined spaces. It is essential that
manufacturers installation instructions be followed when compression fittings of
any type are used.
BCGA CP4 Rev 3 2005 26
7.6 Pipe Jointing
Pipes shall be jointed by one of the following techniques:
1 Carbon steel - welded, bronze welded, flanged, screwed or compression
fittings.
2 Copper and copper alloys - brazed, bronze welded, flanged, screwed,
compression fittings. Soft-soldered joints shall not be used.
3 Stainless steel - welded, brazed, flanged, screwed compression fittings.
4 Plastic varies according to the type of material, but may be solvent-welded,
screwed, fusion-welded, flanged, hose fittings and clips, push-in or
compression fittings.
Jointing techniques not mentioned above shall be used only after detailed evaluation
and risk assessment.
7.7 Jointing Techniques
7.7.1 Welding
All welding shall be made to approved procedures of which the following
are recommended:
BS 2640 Specification for Class II oxy-acetylene welding of
carbon steel pipework for carrying fluids (39).
BS 2971 Specification for Class II arc welding of carbon steel
pipework for carrying fluids (40).
BS 1821 Specification for Class 1 oxy-acetylene welding of
ferritic steel pipework for carrying fluids (37).
BS 2633 Specification for Class 1 arc welding of ferritic steel
pipework for carrying fluids (38).
BS EN 288 Specification for approval of welding procedures for
metallic materials (49).
BS EN 287 Approval testing of welders for fusion welding (48).
BS 4872 Specification for approval testing of welders when
welding procedure approval is not required (41).
ASME Section IX Welding qualifications (64).
7.7.2 Brazing
Joints shall be made with the appropriate brazing alloy and flux, where this
is appropriate and generally to BS EN 13134 (55) for BS 1306 piping
systems or ASME IX (64) for ANSI B31.3. Pipe ends shall be square cut
BCGA CP4 Rev 3 2005 27
with full penetration into the end fitting and a minimum wetted area of 70%
or in accordance with the brazing procedure.
Brazers shall be approved in accordance with BS EN 13133 (54).
In cases where flux residues are not acceptable eg medical, some laboratory
and food applications, copper phosphorus rod may used for fluxless brazing
of copper to copper using a suitable purge.
7.7.3 Screw Threads
Screw threads shall conform to BS 21 (32) where the pressure seal is made
on the thread and to BS EN ISO 228 (57) where the seal is not made on the
thread. Threads shall be clean cut and the calculated strength of the
threaded joints shall be adequate for the pressure and other service loading
of the pipework in which they are installed. The number of joints shall be
kept to a minimum.
NOTE taper and parallel threads, and threads of different forms shall not
be mismatched.
PTFE tape shall only be used on taper threads, it should only be applied
sparingly and start at least one thread back from the start of the thread form.
Under no circumstances should thread tape be in contact with the gas
stream.
7.8 Supports
Supports shall be capable of supporting the pipe system without causing distortion.
Supports shall also be adequate for the concentrated loads imposed by valves and
risers and for axial loading due to expansions/contractions and the pressure of the
fluid. As a guide to the frequency of pipe supports the following would normally be
adequate for metallic pipework:
Nominal Pipe Size (mm)
Support Spacing (m)
Up to 15
22 to 28
35 to 54
1. 5
2. 0
2. 5
7.9 Routing
7.9.1 General
All pipework shall be adequately supported and protected where necessary
from damage, vibration or corrosion.
BCGA CP4 Rev 3 2005 28
Sections of pipework in buildings should be kept to the minimum
reasonable practicable length. Where pipes have to be run inside buildings
they should be run in well-ventilated rooms. Routings in enclosed spaces
(roof and floor spaces, ducts, etc.) should be avoided. Where pipes have to
be routed through enclosed spaces, they should be installed in accordance
with BS 5588 Part 9 (43) and BS 8313 (47).
BS 5588 (43) provides guidance to designers in relation to Fire
precautions in the design and construction of buildings. Part 9 is the Code
of Practice for ventilation and air conditioning ductwork. This code
recommends that toxic or flammable gases should not be routed in or
through ductwork provided for ventilation purposes.
BS 8313 (47) provides guidance relating to the accommodation of building
services in ducts. This standard divides gas vapour and liquid pipework into
groups according to the major risk associated with the pipework contents. BS
8313 recommends that hazardous materials such as flammable, oxidising,
toxic or corrosive gases or liquids should only be run in ducts when there is
no safe practical alternative.
7.9.2 Routing in ducts
Where it is necessary to install flammable gas pipework in ducts the
following precautions shall be taken:
1 Flammable gas pipework shall not be installed in the same duct as
any other services other than cold water or steam.
2 The pipe shall be of non-combustible material with a melting point
not lower than 800C.
3 The duct shall be well ventilated or by some other means it should
be ensured that a hazardous atmosphere cannot develop within the
duct.
4 There shall be no mechanical joints within the enclosed pipe run.
5 Joints shall be welded or brazed and strength tested in accordance
with the requirements of Paragraph 7.8.
6 Pipes carrying liquefied flammable gases should not be run in ducts
unless the duct is filled with a crushed inert in-fill in order to
reduce to a minimum the volume of any gas which may
accumulate as a result of a leak.
Pipes conveying oxidising gases should only be run in ducts if the
following precautions are taken:
7 The pipe shall be of non-combustible material with a melting point
not lower than 800C.
BCGA CP4 Rev 3 2005 29
8 The duct shall be well ventilated or by some other means it should
be ensured that a hazardous atmosphere couldnt develop within
the duct.
9 Joints shall be welded or brazed and strength tested in accordance
with the requirements of Paragraph 7.7.
10 Pipes carrying oxidising gases should not be exposed to any
leakage of incompatible materials, e.g. from oil or flammable
materials.
Inert gases or mixtures of these may be run in ducts if the following
precautions are taken:
1 The duct shall be well ventilated or by some other means it should
be ensured that a hazardous atmosphere cannot develop within the
duct.
2 Joints shall be welded or brazed and strength tested in accordance
with the requirements of paragraph 7.7.
3 Pipes carrying liquefied inert gases should not be run in ducts
unless the duct is filled with a crushed inert in-fill in order to
reduce to a minimum the volume of any gas which may
accumulate as a result of a leak.
Where it is not possible to ventilate ducts, pipework shall be run within an
outer, larger diameter pipe, (i.e. sheathed), both ends of the outer pipe being
open to well-ventilated positions.
Routing of flammable, oxidising or inert services through cavities should be
avoided where practicable, but, if this is necessary, the following
requirements shall be observed:
a) Services should take the shortest practicable route through the
cavity.
b) The use of high-integrity pipework, avoiding joints within the
cavity is recommended. Where a pipe penetrates a fire resisting
division or enclosure, the pipe shall be sleeved. The fire resistance
of the material used for the sleeve shall be at least equal to that of
the materials forming the cavity. The sleeve shall be sealed to the
structure using suitable building materials and the pipe shall be
sealed.
7.10 Underground Routing
Pipework should only be installed underground where there is no alternative , eg in
order to cross roads, railway lines or to enter buildings. Several different methods
may be used:
BCGA CP4 Rev 3 2005 30
1 Pipes installed on pipe racks or supports inside concrete or metal ducts,
which may be closed by the use of masonry slabs or which may be covered
using open grid covers.
2 Pipes laid in trenches and backfilled.
3 Pipes laid in trenches and encased in concrete.
General Requirements
7.10.1 Flammable and oxidising gases should not be run in the same trench or duct
unless:
a) the ventilation is adequate e.g. in a large ventilated duct.
or
b) the trench is back filled with an inert non corrosive material and
the oxygen and flammable gas lines have a minimum separation
distance of 500mm.
or
c) the lines are encased in concrete and the minimum separation
distance is 300mm.
7.10.2 Inert gases may be run in the same trenches as either oxidising or
flammable gases.
7.10.3 Piping shall be at least 50mm away from any electrical power cables.
7.10.4 Mechanical joints shall not be used underground. Joints shall be welded or
brazed and tested in accordance with Paragraph 7.7. Flanges or other
mechanical joints shall only be permissible when they are essential for
assembly and disassembly. Where valves are used, they should be
accessible from the surface (via a suitable access pit, e.g. concrete or brick
lined) and be of a high integrity leak tight design. Where the piping is to be
laid underground on private property under tarmac or grass areas where
there is no likelihood of heavy traffic, trenches shall be at least 600mm
deep. Where the pipe is to be laid under a road, the trench shall be a
minimum of 500mm deep. Where subsidence may be a problem,
consideration should be given to using concrete slabs or steel plates
positioned on a bed of sand above the pipe.
7.10.5 Where the ground at the base of the trench is of irregular consistency, the
depth of excavation should be increased by approximately 75 mm in order
to allow the pipe to be laid on a bed of sand.
7.10.6 Pressure testing should take place prior to back-filling, although this is not
essential if all joints and connections are left exposed for such tests. The
backfill at the sides of the pipe and immediately above it should be of the
same material as that used under the pipe. The initial cover of backfill over
BCGA CP4 Rev 3 2005 31
the pipe should be carried out by hand and compacted such that there is a
good support between the sides of the pipe and the trench and a firm layer
over the top of the pipe.
7.10.7 Where piping is to enter a building, the entry point should be above ground
wherever this is practicable. Pipework shall not pass under the foundations
of the building, under the base of a wall or under the footings. Where the
pipework passes through the wall of the building, a metal sleeve shall be
used and where appropriate, the same principles of construction used as if
the pipework were passing through a cavity.
7.10.8 Plastic pipe work shall not be laid in chemically corrosive soils containing
tars, oils or other acidic type residues. Manufacturers of such pipe should
be consulted where there is any doubt.
7.11 Protection
7.11.1 Painting
Where painting is required, this should be done in accordance with
manufacturers recommendations on clean, dry and rust-free surfaces and
shall conform to BS 1710 (36).
7.11.2 Wrapping
For buried pipework or in corrosive atmospheres, a protective wrapping
shall be applied. The protection shall be applied as a continuous wrap with
sufficient overlap to prevent exposure of the pipe surface. Pipework laid in
open trenches shall be painted where necessary.
7.11.3 Cathodic Protection
Alternatively, a cathodic protection system may be installed to counteract
the corrosive nature of the terrain. This is usually installed by a specialist
contractor and should take into account BS EN 60079 (56) or an equivalent
standard.
7.12 Cleaning
Before erection, pipes, fittings and equipment shall be fully cleaned and degreased
and cleanliness maintained thereafter. However, certain gases such as oxygen
require special cleaning methods as indicated in the Appendices. Where this is the
case, it is recommended that all pipework, valves and fittings exposed to the product
are purchased from a supplier with the capability of cleaning to this standard.
Alternatively specialist-cleaning companies may be used. Site cleaning of pipework
should be limited to re-cleaning ends of pipework/valves and fittings which may
have been contaminated during the system erection process.
Appropriate health and safety precautions shall be followed. Used solvent shall be
recovered and disposed of in accordance with SI 1980:1709 Control of Pollution
(Special Waste) Regulations (24).
BCGA CP4 Rev 3 2005 32
Completed pipework shall be cleaned internally until all foreign matter is removed.
This will normally be achieved by passing clean, dry, oil-free nitrogen or air through
the pipework at high velocity.
7.13 Identification
According to the complexity of the installation and to the variety of gases conveyed,
each pipe should be identified in accordance with BS 1710 (36) and BS 5499 (42).
Where the precise nature of the pipe content is important, a secondary identification
should be superimposed on the basic identity either by written word, gas symbol or
secondary colour.
7.14 Testing
7.14.1 General
Pressure gauges and safety devices may have to be removed from the
system before testing. Safety devices will normally be tested prior to
installation by the manufacturer. Parts which have been tested prior to
installation may be excluded from the pressure test on the final inspection.
7.14.2 Pressure Test
Particular equipment design codes will have specific pressure testing
requirements, and the equipment may also be required to comply with any
applicable national legislation i.e. The Pressure Equipment Regulations
(29).
7.14.3 Types of pressure test
Proof pressure test: this is carried out when the required thickness of all the
pressure parts has not been accurately calculated or is in doubt. Proof
pressure testing should only be carried out hydraulically and the pressure
applied gradually until the specified test pressure is reached or until
significant yielding of any part of the pressure equipment occurs. This is not
normally applicable, as all components should be suitable for the design
pressure.
Standard pressure test: this test is used when the required thickness of all
pressure parts has been calculated, this test is carried out at a specified
pressure above the design pressure, typically 1.25 to 1.5 times the design
pressure.
Leak test: This may be performed at a pressure, not exceeding 110% of the
design pressure on pressure equipment which has satisfactorily passed the
standard pressure test.
Functional test: this test is carried out using a suitable test medium at design
pressure, or working pressure if this is lower, to check that the pressure
equipment and its components function properly. It may include the
actuation of moveable parts, such as the opening and closing of valves; this
BCGA CP4 Rev 3 2005 33
is normally done at the conclusion when protective devices etc have been
refitted.
7.14.4 Applicable pressure tests
New equipment: a standard and a functional pressure test.
Repaired or refurbished equipment: a leak test (as the equipment should
have already had a standard pressure test when it was manufactured) and a
function test.
7.14.5 Test Medium
Equipment should be hydraulically tested wherever possible, as the energy
released in the event of a failure compared with a pneumatic test is
considerably lower.
Pneumatic testing should only be carried out when hydraulic testing is not
practicable, for instance where the interior of the pressure equipment will
be contaminated by the hydraulic test medium.
For hydraulic testing demineralised water with a chloride content of less
then 50 ppm should be used.
For pneumatic testing helium or helium/air mixture, helium is a searching
gas and will leak from positions that a gas such as nitrogen will not.
7.14.6 Determination of the Test Pressure
Test pressure is a function of the design pressure of the equipment.
For systems connected to a high pressure source e.g. a compressed gas
cylinder the design pressure shall be the developed pressure of the cylinder.
For other systems it can either be at the design pressure of the lowest
pressure rated component in the system or at the setting of a protective
device protecting the system.
Whatever pressure test is to be performed and the fluid used a risk
assessment shall be carried out.
Further guidance on pressure testing is given in Safety in Pressure Testing
GS4 (15) published by the HSE.
7.14.7 Pressure Retention Test
Where required the system may be pressurised to the maximum operating
pressure for a period which is relative to the capacity of the system under
test. After taking into account any changes in ambient conditions, the
pressure variation of the system during this period will be measured. If this
BCGA CP4 Rev 3 2005 34
variation is acceptable the system may be commissioned; if not further leak
checks will be required.
7.15 Commissioning
7.15.1 Anti-confusion
Where, for any reason, cross-connection of the pipework is possible, the
following anti-confusion check shall be made:
a) isolate the pipework from all gas supplies except the one under
test, then:
b) check that gas is supplied at each outlet point of the pipework
under test
c) no gas is supplied into the system or from the outlet points of any
other system
d) prove each pipework supply and distribution system in turn with
all other systems isolated.
7.15.2 Purging Into Service
The total system may be purged with an inert gas before introducing the
service gas systematically into the system. For small systems, purging may
be carried out with the service gas.
7.15.3 Service Tests
Check non-return valves and stop valves for closure tightness and gland
leakage.
Check manifold changeover valves for closure tightness and gland leakage.
Automatic changeover devices should be checked for correct operation.
Check alarm and cut-off devices for correct operation and set pressure.
NOTE Pipework conveying natural gas, LPG or methane, or a mixture of these
gases, where the installation is covered by The Gas Safety Regulations
1972 (23) and The Gas Safety (Installation and Use) Regulations 1994
(25, 26 & 27), shall be installed in accordance with the recommendations
of IGE/UP/2 (6) published by the Institution of Gas Engineers. These
Regulations do not apply to factories within the meaning of the
Factories Act 1961, Mines or Quarries within the meaning of the Mines
and Quarries Act 1954, temporary installations used in connection with
any building operation or work of engineering construction (both within
the meaning of the Factories Act ), except that the Regulations shall
apply to such premises used for domestic or residential or sleeping
accommodation. There are several other exceptions which are detailed
in HSE ACOP L56 Safety in the Installation and Use of Gas Systems
and Appliances (18). Thus most industrial installations are not covered
BCGA CP4 Rev 3 2005 35
by the Regulations. Where the Regulations do apply, such work shall
only be carried out by persons registered as competent by The Council
for Registered Gas Installers (CORGI).
7.16 Precautions
Before connecting gas cylinders make sure that there are no particles of dirt in the
cylinder outlet.
Carefully inspect the outlet and if there are any signs of dirt, blow it out with a jet of
compressed air or wipe with a clean, oil free, lint free cloth.
Ensure that the cylinders to be connected are correctly identified for the system e.g.
product and pressure.
Ensure that all equipment to be connected to the system is suitable for the maximum
operating pressure that can be applied and the service gas.
Correct tools should be used to tighten cylinder connections and valves to avoid
damage and over torque.
Always open valves SLOWLY when connected to the gas supply. An open valve
should not be left less than half a turn from the fully open position.
7.17 Provision of information
In accordance with the Pressure Systems Safety Regulations the designer, supplier or
the employer of a person who install, modifies or repairs a pressure system shall
provide sufficient written information to enable the user of a pressure system to
determine the safe operating limits within his responsibility. Such information may
include the following;
Design Codes
Process and Instrumentation Drawings or Flowsheets
Safe operating limits for pressure and temperature
Design pressure and Design Temperature
Operating Instructions (including emergency procedures)
Written Scheme of Examination
Maintenance Instructions
Test Certificates
Declaration of conformity
For flammable or oxidising gas systems a risk assessment to comply with
DSEAR shall be available.
BCGA CP4 Rev 3 2005 36
Appropriate information should be included in the handover documentation or
operating instructions supplied to the user.
8 USER OF THE PRESSURE SYSTEM
The following paragraphs give details of the duties of the user in relation to the
operation, examination, repair and maintenance of the system and of the need for the
user to obtain a written scheme of examination (if applicable) for the system and
keep certain records. Further information relating to the Pressure Systems Safety
Regulations 2000 (30) is given in the BCGA Code of Practice CP 23 (7) and the
Pressure Equipment Regulations 1999 (29).
8.1 Operation - Information and Training
Suitable instructions shall be provided to indicate operation of controls and a system
flowsheet / P& ID shall be available.
Hazard warning notices appropriate to the installation shall be clearly displayed
together with telephone numbers for emergency contact.
The supplier shall provide the user with information on operating conditions and
these shall not be changed such that safe working could be jeopardised: any change
shall be approved by a competent authority.
All operators shall receive adequate instruction and training before operating
manifolds and pipes.
8.2 Maintenance
Maintenance is required by the Pressure Systems Safety Regulations, 2000 (30) to
ensure equipment remains in a safe condition. It is the responsibility of the user to
ensure that this is carried out.
Important differences exist between Maintenance and Written Scheme of
Examination activities. The latter are formal assessments of the pressure system, or
part of it, with regard to its ability to operate safely for a further specified period.
The assessment only considers potential danger from the uncontrolled release of
stored energy.
Maintenance covers a wide range of activities ranging from such items as servicing,
lubrication, adjustment, performance checks and painting through to routine safety
inspections. The latter may partially overlap Written Scheme of Examination
activities, but they are not as comprehensive and do not provide a complete
assessment. As such they are not subject to formal postponement procedures and
restrictive controls.
The maintenance schedule for a system should cover the following points as a
minimum requirement:
BCGA CP4 Rev 3 2005 37
8.2.1 Weekly Inspection (by the user)
Check that:
1 Visually, equipment is in good order, is being correctly used and
all the required equipment is fitted.
2 Manifold, framework and chains are in good condition.
3 Pigtails and flexible hoses are not corroded or damaged.
4 Valves shut off and open correctly.
5 Regulators are identified as being suitable for the gas and pressures
and are not damaged.
6 The system is operating normally, i.e. report if the system is using
more gas than normal, if there is an unusual drop in pressure or if
there is a smell of gas which could indicate a malfunction or leak.
7 The manifold house is free from oil and combustible materials and
is not used as a storeroom.
8.2.2 Annual Inspection (by a person with appropriate experience and
knowledge)
Check that:
1 All repairs and modifications (including removals and additions of
components) and extensions carried out conform to this Code of
Practice.
2 Changes in the vicinity of the installation do not affect its
operation or safety.
Examples are location of heat sources or burners, moving of
machines or work places, occurrence of vibrations, use of a
pipework as an electrical earth or as a support for other items,
proximity to electrical installations and to other piping systems.
3 There is adequate identification of above ground pipework and
route markers for buried pipework.
4 The system is free from leaks by testing at the designated operating
pressure.
5 Buried pipework are in ground which is free from encroachment
by other services, buildings or civil structures.
6 Filters are in good condition and are not blocked. Clean or replace
them where necessary.
BCGA CP4 Rev 3 2005 38
8.3 Repair and modification
The user shall ensure that the employer of a person who installs, repairs or modifies
a pressure system ensures that nothing about the way it is repaired or modified gives
rise to danger, or otherwise impairs the operation of any protective device (e.g.
pressure relief valve or bursting disc) or inspection facility.
All repairs and modifications must be carried out to the same design and
construction standards as the original system, so as not to reduce its integrity. Full
testing of the repaired or modified system will be required on completion (see
Section 7.8).
System records, flowsheets/schematics, general layout drawings, operating
instructions etc will need to be updated following repair and modification.
Consideration shall also be given to the need to amend the system safe operating
limits.
8.4 Written Scheme of Examination
In order to conform with the requirements of the Pressure Systems Safety
Regulations 2000 (30) the user of an installed system shall not allow it to be
operated without a Written Scheme of Examination certified by a Competent Person.
The Written Scheme should cover the following items as a minimum requirement:
a) All protective devices.
b) All manifold pressure regulators (when they are a primary protective
device).
c) All high pressure hoses and pigtails.
d) All pipework where a failure would give rise to danger.
Guidelines for Written Schemes of Examination are given in BCGA CP23 (7).
8.5 Keeping of records
The following records shall be kept by the user (or the owner in the case where he
has undertaken to examine and maintain the system):
a) the Written Scheme of Examination
b) the last report in accordance with the Written Scheme of Examination
c) previous reports if they assist in assessing whether the system is safe to
operate
d) details of any repairs or modifications carried out
e) documents supplied under Section 7.17
f) agreement to postpone an examination and notification to the enforcing
Authority
BCGA CP4 Rev 3 2005 39
g) details of any out of service periods and storage conditions (where
appropriate).
These records shall be kept either at the premises where the equipment is installed or
at the office of the user or owner when applicable. The records may be kept within a
computer system as long as a printed copy can be produced when required.
8.6 The Competent Person
The Pressure Systems Safety Regulations 2000 (30) define duties for the Competent
Person in three distinct functions, i.e.:
advising the user on the scope of the Written Scheme
drawing up or certifying Written Schemes of Examination
carrying out examinations under the Scheme.
The Competent Person may be either:
a user Company with its own in-house inspection department
an inspection organisation providing such services
a partnership of individuals
a self employed person.
The Health and Safety Commission Approved Code of Practice, (Safety of Pressure
Systems ACOP L 122) (19) defines the level of corporate membership, experience,
specialist services and organisation required for the Competent Person drawing up or
certifying Written Schemes of Examination for Minor, Intermediate and Major
Systems.
Member Companies of BCGA are able to provide advice on the systems used within
the gases industry.
BCGA CP4 Rev 3 2005 40
9 REFERENCES *
Document Number Title
1 BCGA CP5 The Design & Construction of Manifolds using
Acetylene Gas to a Maximum Working Pressure
of 25 bar.
2 BCGA CP6 The Safe Distribution of Acetylene in the
Pressure Range 0 -1. 5 bar.
3 BCGA CP18 The Safe Storage, Handling and Use of Special
Gases in the Micro-Electronics and other
Industries.
4 BCGA CP33 The Bulk Storage of Gaseous Hydrogen at Users
Premises.
5 BCGA GN2 Guidance for the Storage of Gas Cylinders in the
Workplace.
6 IGE/UP/2 Gas Installation Pipework, Boosters and
Compressors on Industrial and Commercial
Premises (with amendments Jan 1995).
7 BCGA CP23 Application of the Pressure Systems Safety
Regulations 2000 to Industrial and Medical
Pressure Systems Installed at Consumer
Premises.
Other relevant BCGA Codes are:
8 BCGA CP7 The Safe Use of Oxy-Fuel Gas Equipment
(Individual Portable or Mobile Cylinder Supply).
9 BCGA CP27 Transportable Vacuum Insulated Containers of
not more than 1,000 litres volume.
10 BCGA CP28 Vacuum Insulated Tanks of not more than 1,000
litres volume which are Static Installations at
user Premises.
11 BCGA GN10 Implementation of EIGA Carbon Dioxide
Standards.
European Industrial Gases Association publications:
12 IGC Doc 33/97 Cleaning of equipment for oxygen service
guidelines.
BCGA CP4 Rev 3 2005 41
Document Number Title
13 IGC Doc 42/89 Prevention of hose failures in high-pressure gas
systems.
14 IGC Doc 13/02 Oxygen Pipeline Systems.
HSE Guidance Notes:
15 GS 4 Safety in Pressure Testing, 1998.
16 EH 40 Occupational Exposure Limits (published
periodically).
Department of Health
17 HTM 2022 Medical Gas Pipeline Systems published by
NHS Estates.
HSC Approved Code of Practice
18 L56 Safety in the Installation & Use of Gas Systems
and Appliances.
19 L122 Safety of Pressure Systems.
LPGA Codes of Practice
20 COP 1 Bulk LPG Storage at Fixed Installations.
21 COP 7 Storage of Full and Empty LPG Cylinders and
Cartridges.
Legislation
22 SI 1972 No 917 The Highly Flammable Liquids and Liquefied
Petroleum Gases Regulations.
23 SI 1972 No 1178 The Gas Safety Regulations.
24 SI 1980 No 1709 Control of Pollution (Special Waste)
Regulations.
25 SI 1994 No 1886 Gas Safety (Installation and Use) Regulations.
26 SI 1996 No 550 Gas Safety (Installation and Use) (Amendment)
Regulations.
27 SI 1996 No 2541 Gas Safety (Installation and Use)
(Amendment)(No 2) Regulations.
BCGA CP4 Rev 3 2005 42
Document Number Title
28 SI 1996 No 341 The Health and Safety (Safety Signs and Signals)
Regulations.
29 SI 1999 No 2001 The Pressure Equipment Regulations.
30 SI 2000 No 128 Pressure Systems Safety Regulations.
31 SI 2002 No 2776 The Dangerous Substances and Explosive
Atmospheres Regulations.
British Standards:
32 BS 21 Specification for Pipe Threads for Tubes and
Fittings where pressure-tight joints are made on
the threads.
33 BS 476 Fire tests on building materials.
34 BS 1306 Specification for Copper and Copper Alloy
Pressure Piping Systems.
35 BS 1560 Section 3. 1: Specification for Steel Flanges.
36 BS 1710 Specification for Identification of Pipelines and
Services.
37 BS 1821 Specification for Class 1 Oxyacetylene Welding
of Ferritic Steel Pipework for Carrying Fluids.
38 BS 2633 Specification for Class 1 Arc Welding of Ferritic
Steel Pipework for Carrying Fluids.
39 BS 2640 Specification for Class II Oxyacetylene Welding
of Carbon Steel Pipework for Carrying Fluids.
40 BS 2971 Specification for Class II Arc Welding of Carbon
Steel Pipework for Carrying Fluids.
41 BS 4872 Specification for Approval Testing of Welders
When Welding Procedure Approval Is Not
Required.
42 BS 5499 Graphical symbols & signs.
43 BS 5588 - Part 9 Code of Practice for Ventilation and Air
Conditioning Ductwork.
44 BS 6759 Safety Valves.
BCGA CP4 Rev 3 2005 43
Document Number Title
45 BS 7671 Institution of Electrical Engineers. Wiring
Regulations.
46 BS 7786 Specification for Unsintered PTFE Tape:
General Requirements.
47 BS 8313 Code of Practice for Accommodation of
Building Services in Ducts.
BS EN Standards
48 BS EN 287 Approval Testing of Welders for Fusion
Welding.
49 BS EN 288 Specification and Approval of Welding
Procedures for Metallic Materials.
50 BS EN 562 Pressure Gauges Used in Welding, Cutting and
Allied Processes.
51 BS EN 730 Gas welding equipment: Safety Devices.
52 BS EN 837 Pressure gauges.
53 BS EN 1515 Flanges and their joints: bolting.
54 BS EN 13133 Brazing. Brazer approval.
55 BS EN 13134 Brazing. Procedure approval.
56 BS EN 60079 Electrical apparatus for explosive gas
atmospheres.
BS EN ISO Standards
57 BS EN ISO 228 Pipe threads where pressure-tight joints are not
made on the threads.
58 BS EN ISO 2503 Gas welding equipment Pressure regulators for
gas cylinders used in welding, cutting and allied
processes up to 300 bar.
59 BS EN ISO 4126 - Part 2 Safety devices for protection against excessive
pressure. Bursting disc safety devices.
60 BS EN ISO 7291 Gas welding equipment. Pressure regulators for
manifold systems.
BCGA CP4 Rev 3 2005 44
Document Number Title
61 BS EN ISO 11114 Parts 1
and 2
Transportable gas cylinders. Compatibility of
cylinder and valve materials with gas contents.
Part 1 metallic materials. Part 2 non-metallic
materials.
62 BS EN ISO 14113 Gas welding equipment: Rubber and Plastic
Hoses Assembled for Compressed or Liquefied
Gases up to A Maximum Design Pressure of 450
Bar.
Other:
63 ANSI B31.3 Chemical Plant and Petroleum Refinery Piping.
64 ASME - Section IX Welding Qualifications.
Further information can be obtained from:
Health and Safety Executive
www.hse.gov.uk
HSE Books
www.hsebooks.co.uk
HMSO
www.hmso.gov.uk
EIGA
www.eiga.org
BCGA CP4 Rev 3 2005 45
APPENDIX 1 - OXYGEN
1 GENERAL DATA
Chemical symbol O
2
Flammable/non-flammable Non-flammable (see Clause 3. 1)
Lighter/heavier than air Slightly heavier
Colour Colourless
Odour Odourless
Taste Tasteless
Toxicity Non-toxic
Corrosive Non-corrosive (in absence of moisture)
2 RECOMMENDED MATERIALS
Note: Up to 230 bar.
At pressures higher than 230 bar materials may
require special consideration. Refer to the gas
supplier.
Pipe Copper/Copper alloy
Steel (restricted - see Clause 3. 3)
Jointing Approved grades of:
PTFE
Compressed fibre
Copper washers, viton bonded seals
Valves and other components These require special consideration; refer to
manufacturer.
3 SPECIAL CONDITIONS
3. 1 Oxygen is non-flammable but supports combustion vigorously, combining with all
other elements except inert gases.
3. 2 All readily combustible substances including oil, grease and organic solvents shall
not be allowed to come into contact with oxygen or oxygen-containing equipment.
Scrupulous cleaning, degreasing and freeing from solvents is of prime importance
with oxygen. See IGC Document 33/97 (12).
3. 3 For pipework made of ferrous materials, (e.g. stainless steel, carbon steel) the gas
velocity shall be contained within limited values. The recommended limiting
velocity for oxygen in ferrous distribution pipework is 15 m/sec maximum at 20 bar.
See IGC Document 13/02 (14) for further information
BCGA CP4 Rev 3 2005 46
Appendix 1
Sheet 2 of 2
3. 4 Where ball valves are used in oxygen systems other than as emergency shut off
valves, extreme care shall be exercised in opening such a valve in order to prevent
high velocity gas flows occurring where the line downstream of the valve is at a lower
pressure than the line upstream of the valve. The other danger is of adiabatic
compression occurring in the downstream system causing very high temperatures and
possible ignition.
3. 5 Rapid pressurisation of flexible hoses on oxygen manifolds (e.g. by fast opening of
the cylinder valve may cause an ignition in a plastic lined hose or in the seat of the
non-return valve because of adiabatic compression. In these circumstances adiabatic
compression occurs because the change in pressure is so rapid that there is insufficient
time for the heat which is generated to dissipate. Protective measures as described in
IGC Document 42/89 (13) should be considered to prevent such an ignition resulting
in a hose or valve failure with consequent risk of injury (e.g. provision of a suitable
metallic `heat sink' at the hose end adjacent to the header).
4 SAFETY
4. 1 Oxygen pipework should be separated from pipework containing flammable products
and from sources of ignition to prevent the possibility of combustion occurring.
Note: Separation distances will vary according to the degree of precaution taken, eg
ventilation, sleeving, separation barriers.
4. 2 Oxygen pipework shall be separated by at least 50 mm from electrical systems.
4. 3 Warning notices indicating No Smoking, No Sources of Ignition shall be displayed.
Where the notice uses a pictorial symbol, then this shall be in accordance with The
Health and Safety (Safety Signs & Signals Regulations) SI 1996 No 341 (28).
4.4 Materials
For oxygen service the use of materials, lubricants and greases shall be restricted to
oxygen compatible types only.
BCGA CP4 Rev 3 2005 47
APPENDIX 2 - NITROGEN
Sheet 1 of 1
1 GENERAL DATA
Chemical symbol N
2
Flammable/non-flammable Non-flammable
Lighter/heavier than air Slightly lighter
Colour Colourless
Odour Odourless
Taste Tasteless
Toxicity Non-toxic (see Clause 4. 1)
Corrosive Non-corrosive
2 RECOMMENDED MATERIALS
Pipe Copper/Copper alloy
Steel
Plastic - within the limitations set out in appendix
10
Jointing All commonly used materials are suitable.
Except soft solder
Valves and other components All commonly-used materials are suitable.
3 SPECIAL CONDITIONS
NIL
4 SAFETY
4. 1 Although nitrogen is non-toxic, nitrogen-enriched atmospheres can cause
asphyxiation through the depletion of oxygen.
4. 2 Warning notices indicating Inert Gas Storage shall be displayed.
BCGA CP4 Rev 3 2005 48
APPENDIX 3 - ARGON
Sheet 1 of 1
1 GENERAL DATA
Chemical symbol Ar
Flammable/non-flammable Non-flammable
Lighter/heavier than air Much heavier (see Clause 4. 3)
Colour Colourless
Odour Odourless
Taste Tasteless
Toxicity Non-toxic
Corrosive Non-corrosive
2 RECOMMENDED MATERIALS
Pipe Copper/Copper alloy
Steel
Plastic - within the limitations set out in appendix
10
Jointing All commonly-used materials are suitable.
Except soft solder
Valves and other components All commonly-used materials are suitable
3 SPECIAL CONDITIONS
NIL
4 SAFETY
4. 1 Although argon is non-toxic, argon-enriched atmosphere can cause asphyxiation
through the depletion of oxygen.
4. 2 Warning notices indicating Inert Gas Storage shall be displayed.
4. 3 Argon is considerably heavier than air and will remain in low-lying places for long
periods - this fact will influence the gas storage location and ventilation requirements.
BCGA CP4 Rev 3 2005 49
APPENDIX 4 - HELIUM
Sheet 1 of 1
1 GENERAL DATA
Chemical symbol He
Flammable/non-flammable Non-flammable
Lighter/heavier than air Much lighter
Colour Colourless
Odour Odourless
Taste Tasteless
Toxicity Non-toxic (see Clause 4. 1)
Corrosive Non-corrosive
2 RECOMMENDED MATERIALS
Pipe Copper/Copper alloy
Steel
Plastic - within the limitations set out in
Appendix 10
(Permeability should also be checked with the
manufacturer)
Jointing All commonly-used materials are suitable.
Except soft solder
Valves and other components All commonly-used materials are suitable.
3 SPECIAL CONDITIONS
Helium is an extremely penetrative gas which can leak through joints which have
been proved leak tight with nitrogen, consequently more stringent jointing techniques
such as back-brazing of screwed joints may be necessary.
4 SAFETY
4. 1 Although helium is non-toxic, a helium-enriched atmosphere can cause asphyxiation
through the depletion of oxygen.
4. 2 Warning notices indicating Inert Gas Storage shall be displayed.
4. 3 Helium is an extremely light gas which will readily collect at high level. Adequate
ventilation in such places as the roof of a storage room is therefore necessary.
BCGA CP4 Rev 3 2005 50
APPENDIX 5- HYDROGEN
Sheet 1 of 2
1 GENERAL DATA
Chemical symbol H
2
Flammable/non-flammable Flammable
Lighter/heavier than air Much lighter
Colour Colourless
Odour Odourless
Taste Tasteless
Toxicity Non-toxic (see Clause 4. 1)
Corrosive Non-corrosive
2 RECOMMENDED MATERIALS
Pipe Copper/Copper alloy
Steel (see Clause 3. 2)
Jointing All commonly-used materials are suitable
Except soft solder
Valves and other components All commonly-used materials are suitable (see
Clause 3. 2)
3 SPECIAL CONDITIONS
3. 1 Hydrogen is an extremely penetrative gas which can leak through joints which have
been proved leak tight with nitrogen, consequently more stringent jointing techniques
such as back-brazing of screwed joints may be necessary.
3. 2 Although most commonly used materials are suitable with hydrogen, the problem of
embrittlement under cyclic conditions with steel must be considered especially at
elevated temperatures and pressures.
3. 3 The use of bursting discs is not recommended on hydrogen systems.
4 SAFETY
4. 1 Although hydrogen is non-toxic, a hydrogen-enriched atmosphere can cause
asphyxiation through the depletion of oxygen.
4. 2 Hydrogen vent lines shall terminate in a safe area at high level.
4. 3 Earth all lines and equipment where there is the possibility of electro-static discharge.
BCGA CP4 Rev 3 2005 51
Appendix 5
Sheet 2 of 2
4. 4 Electrical equipment shall be certified to BS EN 60079 (56) or equivalent and
selected, installed and maintained in accordance with that standard..
4. 5 Electrical circuits shall be in accordance with BS EN 60079 (56).
4. 6 Pipework shall be purged out of service with inert gas until the residual hydrogen
concentration is below 1% and purged into service with an inert gas until all residual
oxygen is removed.
4. 7 Each outlet point of the system shall terminate in a left hand thread.
4. 8 Pipework shall have a separation distance of 50 mm from electrical systems.
4. 9 Pipework should be segregated from other pipework carrying oxidising gases and
sources of ignition to prevent combustion occurring.
4. 10 Warning notices Flammable Gas, No Smoking, No Sources of Ignition EX in
accordance with DSEAR (31) shall be displayed. Where the notice uses a pictorial
symbol, then this shall be in accordance with The Health and Safety (Safety Signs &
Signals Regulations) SI 1996 No 341 (28).
4. 11 Fire fighting equipment shall be readily available, but fire fighting should normally be
done by the Fire Service.
4. 12 Hydrogen may spontaneously ignite in the event of a leak or in the event of a relief
device opening. Hydrogen flames are almost invisible and produce no radiant heat.
The approach to them must be made with caution.
4. 13 Hydrogen is an extremely light gas which will readily collect at high level, therefore
adequate ventilation in such places as the roof of a storage room is necessary to
prevent accumulation of gas which could form a potentially explosive atmosphere.
4. 14 Separation distances for hydrogen installations shall take into consideration vertical
distances.
BCGA CP4 Rev 3 2005 52
APPENDIX 6 LIQUEFIED PETROLEUM GAS (LPG)
Sheet 1 of 2
1 GENERAL DATA
Propane Butane
Chemical symbol C
3
H
8
C
4
H
10
Flammable/non-flammable Flammable Flammable
Lighter/heavier than air Heavier Heavier
Colour Colourless Colourless
Odour * Odourless * Odourless
Taste Tasteless Tasteless
Toxicity Non-toxic Non-toxic
Corrosive Non-corrosive Non-corrosive
* Commercial grades of LPG have a strong smelling additive to assist detection
by smell.
2 RECOMMENDED MATERIALS
Pipe Copper/Copper alloy - Not to be used with LPG
containing acetylene compounds if copper
content is above 60%.
Steel.
Jointing PTFE.
Compressed fibre.
Valves and other components All commonly-used materials are suitable.
3 SPECIAL CONDITIONS
3. 1 LPG is much heavier than air and will collect in low-lying positions where it will
remain for long periods before it is dissipated. Storage areas and vent positions
should be selected with this point in mind.
3. 2 Cylinders must be kept vertical. Although LPG is stored as a liquid, this Code applies
only to pipework conveying gas.
3. 3 Compression fittings may be used in well-ventilated areas.
BCGA CP4 Rev 3 2005 53
Appendix 6
Sheet 2 of 2
4 SAFETY
4. 1 Butane is mildly narcotic. Additionally LPG-enriched atmospheres can cause
asphyxiation through the depletion of oxygen.
4. 2 Vent lines shall terminate in a safe area where gas will not accumulate to form a
hazard.
4. 3 Earth all lines and equipment where there is the possibility of electro-static discharge.
4. 4 Electrical equipment shall be certified to BS EN 60079 (56) or equivalent and
selected, installed and maintained in accordance with that standard .
4. 5 Electrical circuits shall be intrinsically safe, explosion-proof or part of a safety barrier
circuit in accordance with BS EN 60079 (56).
4. 6 Pipework shall be purged out of service with inert gas where hot work is to be carried
out and purged into service and leak tested with the service gas or an inert gas.
4. 7 Each outlet point of the system shall terminate in a left hand thread.
4. 8 Pipework shall have a separation distance of 50 mm from electrical systems.
4. 9 Pipework should be segregated from other pipework carrying oxidising gases. Gas
cylinders must also be segregated.
4. 10 Warning notices indicating Flammable Gas, No Smoking, No Sources of Ignition
EX in accordance with DSEAR (31) shall be displayed. Where the notice uses a
pictorial symbol, then this shall be in accordance with The Health and Safety (Safety
Signs & Signals Regulations) SI 1996 No 341 (28).
4. 11 Fire fighting equipment shall be readily available but fire fighting should normally be
done by the Fire Service.
4. 12 The LP Gas Association Codes of Practice numbers 1 and 7 relating to the keeping of
LPG should be consulted (20, 21). Regulation 7 of the Highly Flammable Liquids
and Liquefied Petroleum Gases Regulations (22) makes specific requirements about
the storage and marking of vessels and cylinders of LPG within factory premises.
BCGA CP4 Rev 3 2005 54
APPENDIX 7 - METHANE
Sheet 1 of 1
Methane is the first of the paraffin series of hydrocarbons and is the main constituent of
natural gas. For precise information on natural gas refer to British Gas Codes of Practice.
1 GENERAL DATA
Chemical symbol CH
4
Flammable/non-flammable Flammable
Lighter/heavier than air Lighter
Colour Colourless
Odour Odourless
Taste Tasteless
Toxicity Non-toxic (see Clause 3. 1)
Corrosive Non-corrosive
2 RECOMMENDED MATERIALS
Pipe Copper/Copper alloy - Not to be used with
methane containing acetylene compounds if
copper content is above 60%.
Steel
Jointing All commonly-used materials are suitable.
Except soft solder
Valves and other components All commonly-used materials are suitable.
3 SAFETY
3. 1 Although methane is non-toxic, methane-enriched atmospheres can cause
asphyxiation through the depletion of oxygen.
3. 2 Vent lines shall terminate in a safe area where gas will not accumulate to form a
hazard.
3. 3 Earth all lines and equipment where there is the possibility of electro-static discharge.
3. 4 Electrical equipment shall be certified to BS EN 60079 (56) or equivalent and
selected, installed and maintained to that standard .
3. 5 Electrical circuits should be intrinsically safe, explosion-proof or part of a safety
barrier circuit in accordance with BS EN 60079 (56) .
3. 6 Pipework shall be purged out of service with inert gas until the residual is below 1%
and purged into service using an inert gas until all traces of oxygen are removed.
BCGA CP4 Rev 3 2005 55
Appendix 7
Sheet 2 of 2
3. 7 Each outlet point of the system shall terminate in a left hand thread.
3. 8 Pipework shall have a separation distance of 50 mm from electrical systems.
3. 9 Pipework should be segregated from other pipework carrying oxidising gases and
ignition sources to prevent combustion occurring.
3. 10 Warning notices indicating Flammable Gas, No Smoking, No Sources of Ignition
EX in accordance with DSEAR (31) shall be displayed. Where the notice uses a
pictorial symbol, then this shall be in accordance with The Health and Safety (Safety
Signs & Signals Regulations) SI 1996 No 341 (28).
3. 11 Ventilation shall be provided at high levels to prevent accumulation of gas which
could form a potentially explosive atmosphere.
4. 12 Separation distances for methane installations shall take into consideration vertical
distances.
BCGA CP4 Rev 3 2005 56
APPENDIX 8 CARBON DIOXIDE
Sheet 1 of 2
1 GENERAL DATA
Chemical symbol CO
2
Flammable/non-flammable Non-flammable
Lighter/heavier than air Much heavier (see Clause 4. 3)
Colour Colourless
Odour Slightly pungent odour at high concentrations.
Taste Tasteless
Toxicity Slightly toxic (see Clause 4. 1)
Corrosive Non-corrosive (in absence of moisture).
2 RECOMMENDED MATERIALS
Pipe Copper/Copper alloy.
Steel.
Plastic - within the limitations set out in
Appendix 10.
Jointing Glass filled PTFE
Compressed fibre
Valves and other components Most commonly-used materials are suitable. (see
Clauses 4. 4 and 4. 5)
3 SPECIAL CONDITIONS
Nil
4 SAFETY
4. 1 Although carbon dioxide is usually considered to be non-toxic, it does have a long-
term (8 hours) occupational exposure standard (OES) of 5000 ppm and a short term
(15 minutes) OES of 15,000 ppm. Respiration is affected, breathing becomes
laboured and mild narcotic effects may be experienced. At high concentrations
paralysis of the respiratory system occurs and asphyxiation through depletion of
oxygen can result. Refer to HSE publication EH40 (16).
4. 2 Warning notices indicating inert gas storage shall be displayed. Carbon dioxide is
usually considered as an inert gas but under certain conditions of temperature and
pressure it will react with certain other substances which are themselves highly
reactive. Further guidance should be obtained from the gas supplier.
BCGA CP4 Rev 3 2005 57
Appendix 8
Sheet 2 of 2
4. 3 Carbon dioxide is considerably heavier than air and will remain in low lying places
for long periods, this fact will influence the gas storage location and ventilation
requirements which should be adequate at low level to prevent enrichment occurring.
4. 4 Piping, valves and fittings for use with liquid carbon dioxide may require low
temperature properties and impact tested materials. A relief valve shall be interposed
between any two stop valves where liquid carbon dioxide may be trapped N.B a
bursting disc shall not be used.
4. 5 High tensile brass is not a recommended material.
4. 6 Discharge of liquid carbon dioxide can generate static electricity and it should be
avoided in or near flammable gas mixtures.
BCGA CP4 Rev 3 2005 58
APPENDIX 9 - MIXED GASES
Sheet 1 of 1
Contact the mixture supplier for full details of the physical properties, potential hazards,
safety precautions and operating procedures for the particular gas mixture to be used.
When these facts are known, identify what materials can safely be specified for piping, hoses
and other equipment used in the supply and distribution system and design the system on this
basis, taking into account also the operating and design pressure requirements.
Establish safe procedures for installation, operation and maintenance of the system and agree
emergency procedures to cover any potentially hazardous incidents which may occur.
Consideration should be given to withdrawal rates from the system - this will affect sizing of
the manifold and piping and, in the case of liquefied gases in cylinders, the number of
cylinders required. The possibility of freezing up of pressure regulators should also be
considered (eg methane/natural gas mixtures).
Identify if, under certain conditions, condensable products can be obtained in the system from
the mixture, and establish any precautions or modifications which may be required, eg
drainage points, trace heating.
For flammable mixtures, ensure that cylinders and manifolds, equipment and pipework are
adequately and continuously earthed.
A relief valve shall be interposed between any two stop valves where liquid may be trapped.
Consideration shall be given to the withdrawal to ensure the mixed gas is delivered at the
usage point in the correct ratio.
Ventilation shall be provided at high and low levels as necessary to prevent enrichment of the
normal atmosphere.
BCGA CP4 Rev 3 2005 59
APPENDIX 10 - PLASTIC PIPES
Sheet 1 of 1
Plastic piping may be used in inert gas (i.e. excluding flammable gases and oxygen ) service
Providing that the following criteria are met :
There shall be a minimum ratio between the burst and the safe working pressure of
4:1.
Design temperature shall be within the range -20C to +50C. Note that most
plastics become embrittled at low temperatures and should not therefore be used
where temperatures below -20C are likely to be encountered. Note also that the
maximum working pressures of plastics reduce as the operating temperature
increases, therefore care must be taken in terms of the operating environment in
which materials of this nature are being considered for use, in order to ensure that
the working pressure does not exceed the design pressure at the operating
temperature.
Where plastic piping is proposed to be used, due attention shall be paid to the
coefficient of expansion of the material when designing such systems in order to
make allowance for this factor.
Most plastics degrade in the presence of UV light and this should also be taken into
consideration at the design stage, bearing in mind the operating pressures,
temperatures and environment in which the system is to operate, in order to ensure
that a suitable design life is specified.
Plastic piping is potentially more easily damaged than piping manufactured from
steel or copper. Care must therefore be taken to ensure that this factor is also taken
into account at the installation stage.
Where flexible plastic piping is used, sufficient supports should be used to prevent the piping
from sagging between supports, supporting on cable trays rather than on standard support
systems may be a preferable alternative.
Taking all of the above into account and the design of the piping currently available, plastic
piping should only be used for applications where the system pressure is prevented from
exceeding the safe operating limits specified by the manufacturer by the use of suitable safety
pressure relief devices, for inert gas service, in environments where the possibility of
mechanical damage is minimal.
It is also important to ensure that the ultimate user of the system recognises that that
the piping is to a specific design and that any replacement that is fitted must comply
with the original specification.
BCGA CP4 Rev 3 2005 60
HISTORY AND OBJECTIVES OF BCGA
The British Compressed Gases Association was
established in August l971 as the successor to the British
Acetylene Association, formed in l901. Its Members
consist of producers, suppliers of gases equipment and
container manufacturers and users operating in the
compressed gas field.
The main objective of the Association is the advancement
of technology and safe practice in the manufacture,
handling and use of all gases and the design and
manufacture of all containers, apparatus, appliances, plant,
etc. BCGA also provides advice and makes
representations, insofar as these relate to particular
problems of the compressed gases industry, on behalf of
its Members to all regulatory bodies, including the UK
Government, concerning legislation both existing and
proposed.
Policy is determined by a Council elected from Member
Companies, with detailed technical studies being
undertaken by a Technical Committee and its specialist
Sub-Committees appointed for this purpose.
Further details of the Association may be obtained from:
BRITISH COMPRESSED GASES ASSOCIATION
6 St. Marys Street, Wallingford, OX10 0EL
Tel: 0044 (0)1491 825533 Fax: 0044 (0)1491 826689
Website: www.bcga.co.uk
E-mail: enquiries@bcga.co.uk
BCGA CP4 Rev 3 2005 61
British Compressed Gases Association
www.bcga.co.uk