INSTITUTION OF GAS ENGINEERS AND MANAGERS
IGEM/UP/1A Edition 3
Communication XXXX
IGEM/TSP/13/282
Founded 1863
Royal Charter 1929
Patron
Her Majesty the Queen
STRENGTH TESTING, TIGHTNESS TESTING AND DIRECT
PURGING
OF
LPG/AIR,
NATURAL
GAS
AND
LPG
INSTALLATIONS.
MOP UP TO 60 MBAR, VOLUME UP TO 1 m3 AND DIAMETER
UP TO 150 mm
DRAFT FOR COMMENT
1
This draft Standard IGEM/UP/1A Edition 3 has been prepared by a Panel under the
chairmanship of Andy Durber.
2
This Draft for Comment is presented to Industry for comments which are required by
6th December 2013, and in accordance with the attached Reply Form.
3
This is a draft document and should not be regarded or used as a fully approved and
published Standard. It is anticipated that amendments will be made prior to
publication.
It should be noted that this draft Standard contains intellectual property
belonging to IGEM. Unauthorised copying or use by any unauthorised person
or party is not permitted.
4
This is a copyright document of the Institution of Gas Engineers and Managers.
Enquiries should be addressed in the first instance to:
Nick Cowling
IGEM
IGEM House
26-28 High Street
Kegworth
Derbyshire, DE74 2DA
Tel: 0844 375 4436
Fax: 01509 678198
Email: nick@igem.org.uk
Attached is the Draft for Comment of IGEM/UP/1A – “Strength testing, tightness testing and
direct purging of LPG/Air, Natural Gas and LPG installations. MOP up to 60 mbar, volume up to
1 m3 and diameter up to 150 mm” and the associated comment form.
We wish to make it as easy as possible for those of you representing industry bodies to issue
the draft to your Members. You can either forward this email with attachment complete or
forward it without the attachment and invite them to visit our website via
http://www.igem.org.uk/technical-standards/standards-development/drafts-for-comment.aspx
where the Draft and Comment Form are posted.
Organisations to which this Draft has been circulated:
Organisation
AIGT
Association of Registered Gas Installers
BSI/GSE/30
CIBSE
CIPHE
DNO Collaboration Forum
Energy Institute
ENA
EUSkills
Gas Forum
Gas Safe Register
GIRSAP
GISG
HSE
HVCA
ICOM
National Grid
Northern Gas Networks
Ofgem
Organisation of Professional Gas Operatives
SBGI
Scotia Gas Networks
UKLPG
Wales and West Utilities
YPN
IGEM
COUNCIL
Membership Committee
Marketing Committee
Audit Committee
TCC
GTDC
GMC
GUC
IGEM/UP/1A Edition 3
Communication XXXX
Strength testing, tightness testing and
direct purging of LPG/Air, Natural Gas and
LPG installations.
MOP up to 60 mbar, volume up to 1 m3 and
diameter up to 150 mm
Draft for Comment
Founded 1863
Royal Charter 1929
Patron: Her Majesty the Queen
IGEM/UP/1A Edition 3
Communication XXXX
Strength testing, tightness testing and
direct purging of LPG/Air, Natural Gas and
LPG installations.
MOP up to 60 mbar, volume up to 1 m3 and
diameter up to 150 mm
Draft for Comment
Price Code: C10H
© The Institution of Gas Engineers and Managers
IGEM House
High Street
Kegworth
Derbyshire, DE74 2DA
Tel: 0844 375 4436
Fax: 01509 678198
Email: general@igem.org.uk
Copyright © 2013, IGEM. All rights reserved
Registered charity number 214001
All content in this publication is, unless stated otherwise, the property of IGEM. Copyright laws
protect this publication. Reproduction or retransmission in whole or in part, in any manner,
without the prior written consent of the copyright holder, is a violation of copyright law.
ISBN 978 1 905903 XX X
ISSN 0367 7850
Published by the Institution of Gas Engineers and Managers
Previous Publications:
Communication 1645 (1998) – 1st Edition
Communication 1701 (2003) – 2nd Edition
Communication 1717 (2005) – 2nd Edition, Reprint with Amendments
For information on other IGEM Standards please visit our website, www.igem.org.uk
IGEM/UP/1A Edition 3 (Draft for Comment)
CONTENTS
SECTION
PAGE
1
Introduction
1
2
Scope
5
3
Legal and allied considerations
9
4
Test equipment and criteria
10
5
Strength testing
10
6
7


5.1
Determination of STP
10
5.2
11
11
11



Decision whether to strength test
• 5.2.1 New installations and extensions
• 5.2.2 Existing installations
5.3
Method, pressure, duration and test criteria for strength testing
11
5.4
Testing separate components or sub-assemblies
11
5.5
Procedures
12
Tightness testing
14

6.1
15
15
15

General
 6.1.1 New installations and extensions
 6.1.2 Existing installations
6.2



Installation volume (IV)
 6.2.1 General
 6.2.2 Calculations
15
15
16
6.3
Tightness test pressure (TTP)
17
6.4
Selection of pressure gauges
17
6.5

Test criteria
 6.5.1 New installations and extensions
 6.5.2 Existing installations
18
18
18
6.6
20
20
21

Tightness test duration (TTD)
 5.6.1 New installations and extensions
 5.6.2 Existing installations
6.7
21
21
22
22
23

Procedures
 6.7.1 By-passing components
 6.7.2 Ambient conditions
 6.7.3 Testing new installations and extensions
 6.7.4 Testing existing installations
6.8
Appliance connector
25
Direct purging



28
7.1
General
28
7.2
Planning and supervision
28
7.3
Site precautions
 7.3.1 Warning notices and label
 7.3.2 Electrical and fire
29
29
30
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IGEM/UP/1A Edition 3 (Draft for Comment)
APPENDIX








7.4
Designing and positioning purge points, hoses and vent stacks
30
7.5
Verification of purge flow rate
31
7.6
Identification of purge gas cylinders
32
7.7
Gas detectors, oxygen analysers and other electronic equipment
32
7.8
Gas appliances
32
7.9
Determination of the purge volume, purge flow rate and purge time32
7.10
Vent gas testing
34
7.11
34
34
35

Purging procedures when venting to outside
 7.11.1 Direct purging from air to gas i.e. commissioning
 7.11.2 Direct purging from gas to air i.e. de-commissioning
7.12
Dealing with meters within pipework sections
 7.12.1 Replacement meter with associated pipework
maintained at positive pressure
 7.12.2 Replacement meter with associated pipework
not maintained at a positive pressure
 7.12.3 Purging a new meter
37
37
38
39
1
Glossary, acronyms and symbols
42
2
References
45
3
Indirect purging with nitrogen
47
4
Tightness test durations for a water gauge using the concept of “no perceptible
movement” (for new installations only)
48
FIGURES
1
Relative pressure levels
2
2
Algorithm to select testing and purging standards
2
3
Typical schematic NG installations
7
4
Flowchart/decision algorithm for strength testing
13
5
Flowchart/decision algorithm for tightness testing of new
installations and extensions
26
Flowchart/decision algorithm for tightness testing
of existing installations
27
7
Flowchart for direct purging of air to gas
40
8
Flowchart for direct purging of gas to air
41
1
Method, pressure, duration and test criteria for strength testing
11
2
Installation volume (IV) of meters
16
3
Volume of 1 m length of pipe
17
4
Selection of pressure gauges (typical data)
18
6
TABLES
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IGEM/UP/1A Edition 3 (Draft for Comment)
5
Determination of maximum allowable pressure drop (test criteria) on
existing installations
19
6
Tightness test duration (TTD) for new installations and extensions
20
7
Tightness test duration (TTD) for existing installations
21
8
Let-by test period
23
9
Minimum purge flow rate
33
10
Flammable limits and safe purge end points
34
11
Flammability limits and safe purge end points for indirect purge
48
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IGEM/UP/1A Edition 3 (Draft for Comment)
SECTION 1 : INTRODUCTION
1.1
This Standard supersedes IGE/UP/1A Edition 2, Communication 1701 and
IGE/UP/1A Edition 2 Reprint with Amendments, Communication 1715 which are
obsolete. It complements the IGEM/UP/1 Edition 3.
1.2
This Standard has been drafted by a Panel appointed by the Institution of Gas
Engineers and Managers’ (IGEM’s) Gas Utilization Committee, subsequently
approved by that Committee and published by the authority of the Council of
the Institution.
1.3
IGEM/UP/1 deals with all aspects of strength and tightness testing of selected
1st, 2nd and 3rd family gases at a maximum operating pressure (MOP) not
exceeding 16 bar. It deals with all aspects of purging those gases but there is no
limit on MOP for purging.
Note:
It has been recognised that certain activities outlined in IGEM/UP/1 are only required for
“large” installations and/or higher pressures and/or other gases and, therefore, the text of
IGEM/UP/1A Edition 3 can be much simpler due to the limited scope.
IGEM/UP/1A deals with strength and tightness testing and direct purging of
Liquefied Petroleum Gas/Air (LPG/Air), Natural Gas (NG) and Liquefied
Petroleum Gas (LPG) installations of volume not exceeding 1 m3 (0.5 m3 for LPG
installations) and maximum operating pressure (MOP) of not exceeding 60 mbar
on industrial and commercial premises.
Note:
In the United Kingdom LPG/Air is typically 1st family gas, NG is 2nd family gas and LPG is a
3rd family gas. NG is lighter than air and LPG/Air and LPG are both heavier than air.
IGEM/UP/1A is intended to assist the operative in understanding and identifying
the particular activities of strength and tightness testing and direct purging
related to a particular installation.
Note:
Strength testing ensures that pipework can withstand, with respect to integrity, the
pressures it could experience under fault conditions. A result of carrying out a strength test
is that the subsequent tightness test is carried out at Operating Pressure (OP) and not at
higher pressures. For IGEM/UP/1A applications, the strength and tightness tests may be
carried out separately or be combined or be carried out concurrently. Referring to Figure 2,
note how OP is shown to oscillate about the set point (SP). Note also that MOP can be
declared at any value from OP to a limit below maximum incidental pressure (MIP).
IGEM/UP/1B deals with all aspects of tightness testing and direct purging of
small Liquefied Petroleum Gas/Air (LPG/Air), NG and Liquefied Petroleum Gas
(LPG) installations with or without a meter of maximum badged capacity not
exceeding 16 m3 h-1 and supply MOP (MOPu) not exceeding 2 bar.
IGEM/UP/1C deals with strength testing, tightness testing and direct purging of
meter installations (as defined in IGEM/G/1), containing either NG or LPG, of
volume not exceeding 1 m3 and MOP not exceeding 7 bar.
Note:
IGEM/UP/1C is most useful for those NG or LPG meter installations that have a means of
isolation on the outlet, are out of scope of IGEM/UP/1B and where there is no desire to test
the installation pipework downstream of the meter installation.
Figure 1 will assist in selecting the appropriate standard.
Note:
For a new system of installation pipework, the onus is on the designer to establish both the
maximum incidental pressure (MIP) and MOP. For an existing system of installation
pipework, the onus is on the designer/owner of the installation to ensure that any increase
in pressure within the installation will not result in OP exceeding MOP of the system and on
the gas transporter/meter asset manager (GT/MAM) to ensure that any change in their
pressure regimes due to fault conditions will not jeopardise the safety of the downstream
installation. This involves effective communication between the GTs/MAMs and installation
designers/owners.
1
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IGEM/UP/1A Edition 3 (Draft for Comment)
Start
LPG installation
on a boat, small craft, (up to
24 m in length) or other
vessels?
PD 5482-3 or
BS EN ISO 10239
Yes
No
Is supply MOP
≤ 2 bar (for LPG/air and NG) AND
Ø ≤ 35 mm AND
Meter badged capacity ≤ 16 m3 h-1 AND
volume ≤ 0.035 m3 AND
OP ≤ 21 mbar (for LPG/Air and NG) OR
OP ≤ 37 mbar (for LPG)?
Yes
IGEM/UP/1B Edition 3
Yes
IGE/UP/1A Edition 2
No
Is MOP ≤ 60 mbar AND
Ø ≤ 150 mm AND
volume ≤ 1 m3 (for LPG/Air and NG) OR
volume ≤ 0.5 m3 (for LPG)?
No
NG or LPG?
Yes
Meter installation with
supply MOP ≤ 7 bar AND
with volume ≤ 1 m3 AND
with no PE included AND
isolated at the outlet
Yes
IGEM/UP/1C
No
No
IGE/UP/1 Edition 2


V
less than or equal to
nominal diameter
volume
MOP
NG
OP
LPG
Maximum Operating Pressure
Natural Gas
Operating pressure
Liquefied petroleum gas
mbar
mm
m3
millibar
millimetre
cubic metre
Note 1: If it is preferred IGE/UP/1 Edition 2 can be used rather than IGE/UP/1A Edition 2,
IGEM/UP/1B Edition 3 or IGEM/UP/1C or PD 5482-3 or BS EN ISO 10239. It is necessary to
check the scope of referenced Standards before proceeding.
Note 2: Operating pressures listed are nominal for the installations and will vary around the
regulator set point (see Figure 2).
FIGURE 1 - ALGORITHM TO SELECT TESTING AND PURGING STANDARDS
2
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IGEM/UP/1A Edition 3 (Draft for Comment)
STP
MIP
OP
MOP
SP
Note:
=
=
=
=
=
Strength test pressure
Maximum incidental pressure (e.g., as declared by the GT/MAM/Supplier)
Operating pressure
Maximum operating pressure
Set point of the regulator.
This is extracted from IGEM/TD/13 and simplified for the purposes of IGEM/UP/1A.
FIGURE 2 - RELATIVE PRESSURE LEVELS
1.4
This Standard makes use of the terms “must”, “shall” and “should” when
prescribing particular procedures. Notwithstanding Sub-Section 1.7:



the term “must” identifies a requirement by law in Great Britain (GB) at the
time of publication
the term “shall” prescribes a requirement which, it is intended, will be
complied with in full and without deviation
the term “should” prescribes a requirement which, it is intended, will be
complied with unless, after prior consideration, deviation is considered to be
acceptable.
Such terms may have different meanings when used in legislation, or Health and
Safety and Executive (HSE) Approved Code of Practice (ACoPs) or guidance, and
reference needs to be made to such statutory legislation or official guidance for
information on legal obligations.
1.5
The primary responsibility for compliance with legal duties rests with the
employer. The fact that certain employees, for example “responsible engineers”,
are allowed to exercise their professional judgement does not allow employers
to abrogate their primary responsibilities. Employers must:



1.6
have done everything to ensure, so far as it is reasonably practicable, that
“responsible engineers” have the skills, training, experience and personal
qualities necessary for the proper exercise of professional judgement
have systems and procedures in place to ensure that the exercise of
professional judgement by “responsible engineers” is subject to appropriate
monitoring and review
not require “responsible engineers” to undertake tasks which would
necessitate the exercise of professional judgement that is not within their
competence. There should be written procedures defining the extent to
which “responsible engineers” can exercise their professional judgement.
When “responsible engineers” are asked to undertake tasks which deviate
from this they should refer the matter for higher review.
It is now widely accepted that the majority of accidents in industry generally are
in some measure attributable to human as well as technical factors in the sense
that actions by people initiated or contributed to the accidents, or people might
have acted in a more appropriate manner to avert them.
It is therefore necessary to give proper consideration to the management of
these human factors and the control of risk. To assist in this, it is recommended
that due regard be paid to HSG48 and HSG65.
3
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IGEM/UP/1A Edition 3 (Draft for Comment)
1.7
Notwithstanding Sub-Section 1.4, this Standard does not attempt to make the
use of any method or specification obligatory against the judgement of the
responsible engineer. Where new and better techniques are developed and
proved, they should be adopted without waiting for modification to this
Standard. Amendments to this Standard will be issued when necessary, and
their publication will be announced in IGEM’s Journal and other publications as
appropriate.
1.8
Requests for interpretation of this Standard in relation to matters within its
scope, but not precisely covered by the current text, should be addressed in
writing to Technical Services, IGEM, IGEM House, High Street, Kegworth,
Derbyshire, DE74 2DA and will be submitted to the relevant Committee for
consideration and advice, but in the context that the final responsibility is that of
the engineer concerned. If any advice is given by or on behalf of IGEM, this
does not relieve the responsible engineer of any of his or her obligations.
1.9
This Standard was published in January 2013.
4
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IGEM/UP/1A Edition 3 (Draft for Comment)
SECTION 2 : SCOPE
2.1
This Standard covers strength and tightness testing, and purging of installations
containing LPG/air, NG or LPG.
Note:
2.2
For other gases, IGEM/UP/1 applies.
This Standard applies to any section of an installation downstream of the outlet
of the emergency control valve (ECV).
Note:
This includes any primary or secondary meter installation.
For pressures exceeding 75 mbar on the inlet to the section being tested, the
length of pipework between a valve being used to isolate that section and the
first regulator downstream of that valve is limited to a maximum length of 3 m
unless it has been pre-tested for strength and tightness prior to assembly.
Typical installations are shown in Figure 3.
This Standard does not apply to distribution mains, service pipes or service
pipework, for which the appropriate Standard, i.e. IGEM/TD/3, IGEM/TD/4 or
UKLPG CoP 22 applies.
2.3
This Standard applies to installations/sections of an installation (that may
include meter installations) having the following:



volume not exceeding 1 m3 for LPG/air and NG installations and 0.5 m3 for
LPG installations, including any meter and any allowance for fittings
MOP not exceeding 60 mbar at the outlet of the first regulator
pipework of nominal bore not exceeding 150 mm.
2.4
This Standard covers the testing of any installation sections of an installation
where IV can be calculated or a conservative estimate i.e. over estimate, can be
made.
2.5
This Standard applies to strength testing and/or tightness testing in the
following circumstances:






new installations


routine testing of existing installations
alteration to, replacement of, or re-use of, existing installations
new extensions to existing installations
prior to any work on existing installations
where there is a known or suspected gas escape
where there has been a complete loss of supply pressure i.e. upstream of
the ECV, or of installation pressure
immediately before purging of installations (except when taking components
permanently out of service).
Note:
If considering strength testing existing pipework, refer to clause 5.2.2.
5
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IGEM/UP/1A Edition 3 (Draft for Comment)
2.6
This Standard applies to direct purging in the following circumstances:






new installations
alteration to, replacement of or re-use of existing installations
new extensions to existing installations
where there has been a complete loss of installation pressure
where there is the possibility of air being present in an installation
where an installation is to be taken out of service temporarily or
permanently.
2.7
All pressures quoted are gauge pressures, unless otherwise stated.
2.8
Italicised text is informative and does not represent formal requirements.
2.9
Appendices are informative and do not represent formal requirements unless
specifically referenced in the main sections via the prescriptive terms ‘must’,
‘shall’ or ‘should’.
6
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IGEM/UP/1A Edition 3 (Draft for Comment)
(a) Typical installation. MOPu  75 mbar.
Installation MOP  60 mbar
Strength test if New or Extension.
Tightness test and
Purge to IGEM/UP/1A.
M
ECV
F
S
R
A
MIV
AECV
(If fitted)
AIV
(b) Typical installation. 75 mbar < MOPu  2 bar
Installation MOP  60 mbar
(c) Example section installation. 2 bar < MOPu
Section installation MOP  60 mbar
ECV
S
F
R
MIV
M
A
AECV
AIV
IV
MOPu
emergency control valve
safety device (see BS 6400)
filter
regulator
meter inlet valve
meter
appliance
additional emergency control valve
appliance isolation valve
isolation valve
supply MOP.
<

Network
meter installation
installation pipework
less than
less than or equal to
Note 1: Certain installations will incorporate an under pressure shut-off device.
Note 2: A meter may not be fitted on LPG installations.
Note 3: Where a component or sub-assembly (meter installation component, meter “skid” unit,
etc.) has been pre-tested and not subsequently modified (such as by cutting threads or
welding) and has appropriate certificates of conformity available, the strength testing of
such a component/assembly need not be undertaken but a visual examination of joints,
general condition, suitability, etc. is recommended prior to installing and subsequent
tightness testing as for a new installation. Permanent marking, for example by
manufacturer’s badging/stamping, may be deemed as certification of conformity.
FIGURE 3 - TYPICAL INSTALLATIONS
7
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IGEM/UP/1A Edition 3 (Draft for Comment)
SECTION 3 : LEGAL AND ALLIED CONSIDERATIONS
3.1
This Standard is set out against a background of legislation in force in GB at the
time of publication. Similar considerations are likely to apply in other countries
where reference to appropriate national legislation is necessary.
All relevant legislation must be applied and relevant ACoPs, official Guidance
Notes and referenced codes, standards, etc. shall be taken into account.
Note:
Appendix 2 is relevant in this respect.
Where British Standards, etc. are quoted, equivalent national or international
standards, etc. equally may be appropriate.
3.2
Any person engaged in strength testing, tightness testing or purging of pipework
must be a competent person.
Note:
Any person carrying out the installation of gas pipework and associated fittings must be
competent to do so. Where gas installation work is carried out in properties covered by the
Gas Safety (Installation and Use) Regulations (GS(I&U)R), the persons carrying out that
work must be a “member of a class of persons” as specified by those Regulations.
At the time of publication of this Standard, the body with HSE approval to operate, and
which maintains, a register of businesses in the GB who are "members of a class of
persons" is the Gas Safe Register. Thus, it is essential that all businesses or self-employed
gas installers be registered with Gas Safe if GS(I&U)R apply. Persons who are deemed
competent to carry out gas work under GS(I&U)R are those who hold a current certificate
of competence in the type of activity to be conducted issued under the ACoP arrangements,
or by a certification body accredited by the United Kingdom Accreditation Service (UKAS)
for the Accredited Certification Scheme (ACS).
3.3
Consideration shall be given to the environmental impact of methane and other
hydrocarbons in the atmosphere. Releases should be minimised to levels
required to achieve prescribed purge end points.
3.4
If at any stage in the tightness testing or purging process there is any potential
for fuel gas or a fuel gas/air mixtures being released into the atmosphere, for
example adjusting the pressure for a let by test, it will need to be vented
ensuring the following safety precautions are taken throughout the process:





avoid any accumulation of gas within confined spaces

advise the responsible person for the premises or other persons in the area
of the above of the intent to purge and that there may be a smell of gas.
prevent inadvertent operation of any electrical switch or other appliance
extinguish all potential sources of ignition
ensure that there is no smoking or naked lights
ensure good ventilation by opening doors, windows, passive stack ventilation
systems, etc.
8
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IGEM/UP/1A Edition 3 (Draft for Comment)
SECTION 4 : TEST EQUIPMENT AND CRITERIA
4.1
TEST EQUIPMENT
4.1.1
Any gauge or gas detector shall:





be suitably ranged
if appropriate, be zeroed at atmospheric pressure at the start of each test
be appropriate for the gas under test
be suitable for the atmosphere in which they are to be used
be calibrated for the gas on which it will be used in accordance with the
manufacturer’s instructions.
Any electronic gauge or gas detector shall be calibrated at least every 12
months, or otherwise as specified by the manufacturer, and a calibration
certificate should be available.
Note:
4.1.2
4.1.3
For the purposes of this Standard, one of the following gauges shall be used:



Fluid (Water) gauge reading in 0.5 mbar increments
Electronic gauge reading to 1 decimal place
Electronic gauge reading to 2 decimal places.
Any electronic gauge shall:


be operated within the manufacturer’s specification for ambient temperature
be stabilized at the ambient temperature as specified by the gauge
manufacturer, prior to the test being carried out.
Note:
4.1.4
Fluid (water) gauges do not require calibration but do need to be kept well maintained.
Electronic gauges may be prone to drifting due to changes in ambient temperature.
In the following situations, electronic test equipment shall be certified for use in
a hazardous area (intrinsically safe):

when seeking the source of a known or suspected gas escape, using a gas
detector

where it is known or suspected that the location in which the equipment is to
be used could contain a flammable atmosphere that may be ignited by the
use of equipment that is not certified for use in hazardous areas

when a hazardous area is imposed by the gas installation or other
installations/situations that require the use of such certified equipment and
the equipment is to be used within the designated zone of that hazardous
area

when it is anticipated that the area in which the equipment will be located
will be left unattended at any time during the test/purge

when a risk assessment indicates that the use of certified equipment is
essential.
The decision on whether electronic equipment, for example pressure gauges and
gas detectors, can be of a type not certified for use in a hazardous area, may be
complex and is not an issue that can be developed in IGEM/UP/1A.
Note:
Fluid (water) gauges can always be used if there is any doubt about the use of electronic
pressure gauges that are not certified for use in hazardous areas.
Use of electronic pressure gauges that are not certified for use in hazardous areas, placed
in the open air or in well ventilated environments and located in a position that will not
cause the ignition of any flammable atmospheres may be acceptable for a number of the
above situations, subject to a suitable risk assessment.
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IGEM/UP/1A Edition 3 (Draft for Comment)
A hazardous area is an area in which explosive mixtures are, or may be expected to be, in
quantities such as to require special precautions for the construction, installation and use of
electrical apparatus or other sources of ignition. Detailed guidance on hazardous areas
relating to gas installations can be found in IGEM/SR/25 and IGEM/UP/16.
4.1.5
Any equipment, including the sample line, shall be checked for integrity
immediately prior to measurement.
Only proprietary leak detection fluids (LDFs) shall be used that comply with
BS EN 14291 and should be compatible with the materials to which it is to be
applied. LDFs containing more than 30 parts per million of halogens shall not be
used on stainless steel components. LDFs containing ammonia shall not be used
on copper or brass components.
To avoid subsequent corrosion, care shall be taken to ensure that LDF is wiped
off pipe and fittings after use.
Note 1: A pH value of 7.0 or less indicates absence of ammonia.
Note 2: Detergents and soap solutions such as “washing-up” liquids are not suitable.
Note 3: Certain chemicals (for example, ammonia and chlorides) used in some LDFs can cause
unwanted effects such as stress corrosion cracking.
4.2
TEST CRITERIA
4.2.1
Consideration shall be given to whether the installation is new or existing and
the type of fuel being tested. Test criteria for strength testing and tightness
testing are given in Sections 5 and 6 respectively.
4.2.2
IGEM/UP/1A Edition 3 continues to adopt the concept of “gauge readable
movement”. When using a water gauge, it is possible to reduce the duration of
tests for new installations and extensions by adopting the concept of “no
perceptible movement” in which case Appendix 4 shall be used.
4.2.3
For “let-by tests” and ‘appliance connector tests’, the pass criteria shall be “no
perceptible movement” during the test period.
Note:
A movement of 0.25 mbar or less on a fluid (water) gauge is considered to be “not
perceptible”. Therefore, if the gauge is seen to move, it can be inferred that the pressure
within the installation has altered by more than 0.25 mbar.
It follows that, where a gauge that can register perceptible movement of less than 0.25
mbar i.e. an electronic gauge, is used, the pass criteria of “no perceptible movement” has
to be considered to be a maximum of 0.25 mbar except for those gauges that read to one
decimal place when “no perceptible movement” is considered a maximum of 0.2 mbar.
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IGEM/UP/1A Edition 3 (Draft for Comment)
SECTION 5 : STRENGTH TESTING
New pipework, designed in accordance with current relevant standards, will have been
designed to withstand the strength test pressure (STP). However, particular components
within the pipework may need to be removed for the strength test (see Sub-Section 5.4). In
addition, appliances may not be designed to withstand the STP.
Strength testing is used to identify any major flaw in the construction of a new installation,
prior to tightness testing.
A strength test permits a fall in pressure limited to the value given in Table 1.
Note 1: It is advisable to combine the strength and tightness tests i.e. immediately follow the strength test with the
tightness test. This may save a little time by not requiring a stabilization period for the tightness test. The
requirements given in Sections 4 and 5 assume a separate test for each (although some guidance is included
for combining the tests) and the principles equally apply for a combined test.
Note 2: It is also permitted to carry out the tightness test concurrently with the strength test. This would mean
carrying out the tightness test at STP, applying the greater of the required stabilization and test times but
not both, and applying the tightness test pass/fail criteria (a pass indicating that both the strength and
tightness tests are satisfactory). However, there will be a minority of installations that will fail the tightness
test that would have passed if the tests had been carried out separately or simply combined. IGEM/UP/1A
does not describe the method of carrying out the tests concurrently.
Preparations for the tightness test will need to be made prior to carrying out the strength test
if the tests are to be combined or if they are to be carried out concurrently.
Some leak detection fluids (LDFs) have an adverse effect on certain pipework materials.
Consequently, any residual fluid shall be washed thoroughly off the pipe.
If necessary, for example when joints are broken, temporary electrical continuity bonds shall
be installed before testing.
For the purposes of this section, it is assumed that, due to the low test pressure involved, the
strength test is carried out pneumatically. For hydrostatic testing, the procedures and criteria
in IGEM/UP/1 shall be applied.
Note:
5.1
Hydrostatic testing is not necessary for installations capable of being tested to IGEM/UP/1A and is not
recommended due to the subsequent need to dry the pipework.
DETERMINATION OF STP
STP shall be as given in Table 1. This Standard assumes that MOP equates to
design pressure (DP). Where DP is quoted and is in excess of MOP, the value of
DP shall be used in the calculation of STP.
Where a booster or compressor is included anywhere downstream of, or within,
the installation pipework being tested, the maximum back pressure shall not
exceed 75 mbar.
Where DP is greater than MOP and exceeds 75 mbar, or where the maximum
back pressure exceeds 75 mbar, the installation shall be tested in accordance
with IGEM/UP/1.
Note:
IGEM/UP/2 explains the principles of this back pressure but its value would need to be
determined from equipment manufacturers and/or system designers.
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IGEM/UP/1A Edition 3 (Draft for Comment)
5.2
DECISION WHETHER TO STRENGTH TEST
5.2.1
New installations and extensions
A strength test shall be carried out on any new installation or extension except
for components that have been pre-tested or have been removed to avoid over
pressurisation, for example appliances.
Note:
Where a component or sub-assembly (meter installation component, meter “skid” unit, etc.)
has been pre-tested and not subsequently modified and has appropriate certificates of
conformity available, the strength testing of such a component/assembly need not be
undertaken but a visual examination of joints, general condition, suitability, etc. is
recommended prior to installing and subsequent tightness testing as for a new installation
(see Sub-Section 5.4). Permanent marking, for example by manufacturer’s
badging/stamping, may be deemed as certification of conformity.
5.2.2
Existing installations
5.2.2.1
A strength test shall not be carried out on an existing installation unless the
installation has been subjected to repairs involving new sections of pipework,
etc. that cannot be tested separately or the OP is to be increased to a level not
previously covered by strength testing.
5.2.2.2
Strength testing of an existing installation shall not be undertaken without first
undertaking a suitable risk assessment which shall establish that the installation
will withstand STP without catastrophic failure.
Note:
IGE/SR/24 provides general guidance on risk assessment techniques.
5.2.2.3
If it is decided to strength test an existing installation, and if the system has
been de-commissioned or has lost all pressure, it shall be purged with air or
nitrogen (N2) using the correct procedures (a suitable procedure for purging
with N2 is given in Appendix 3), before testing.
5.3
METHOD, PRESSURE, DURATION AND TEST CRITERIA FOR STRENGTH
TESTING
5.3.1
The strength test pressure (STP), duration (STD) and criteria shall be as given
in Table 1.
5.3.2
The upstream fault pressure shall be known and MIP of the section to be tested
shall be at least this value.
Note:
GAS
LPG/Air
or NG
LPG
*
Either this value will have been formally recorded previously or the relevant GT will need to
be consulted.
MOP
STP
STABILIZE
STD
MAXIMUM
PERMITTED
DROP
≤ 21 mbar
82.5 mbar
5 mins*
5 mins
20% STP
> 21 mbar
5 mins*
5 mins
20% STP
≤ 60 mbar
(greater of)
120 mbar and
2.5 MOP
≤ 60 mbar
165 mbar
5 mins*
5 mins
20% STP
Where surrounding conditions are stable, the responsible engineer may judge the installation to
have stabilised before the time periods given.
Note:
A pressure drop of 20% STP or less indicates general integrity but any significant drop
means that the tightness test is liable to fail and the cause needs to be found and rectified.
TABLE 1 - PRESSURE, DURATION AND TEST CRITERIA FOR STRENGTH
TESTING
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IGEM/UP/1A Edition 3 (Draft for Comment)
5.4
TESTING SEPARATE COMPONENTS OR SUB - ASSEMBLIES
Any component or sub-assembly that could be internally damaged by STP shall
be removed prior to carrying out the strength test. Such a component or
sub-assembly shall be, or be proved to have been, tested separately to an
appropriate standard.
Note 1: Components such as regulators, meters, non-return valves (NRVs), automatic isolation
valves, safety shut-off valves (SSOVs), etc, may need to be removed and replaced with
spool pieces or sealed off with an appropriate fitting.
Note 2: When the item(s) subsequently is(are) connected to the pipework section, it is not
necessary to repeat the strength test for the whole section before carrying out a tightness
test, provided the connections are inspected carefully during the tightness test. Such
connections, if welded, will need to have been subject to non-destructive testing (NDT) to a
standard equivalent to that used for the rest of the section.
5.5
PROCEDURES
5.5.1
A thorough survey of the pipework section, to detect any major integrity defect,
shall be carried out before testing, including, as appropriate, inspection of
certificates, NDT, etc.
Note:
This survey may entail checking the accuracy of any plans, any other information provided
and the mechanical integrity of installations.
As far as is reasonably practicable, joints should be exposed during the strength
test and indications of leakage sought using LDF.
5.5.2
It shall be ensured that all pipework and components have been designed,
installed and anchored to withstand STP.
5.5.3
Before testing, the following actions shall be taken:

where necessary, remove any component that is not to be included in the
test (see Sub-Section 5.4). Install spool pieces or blanks

ensure all isolation valves are plugged securely or blanked off and the valves
are in the open position to ensure the body is tested


ensure there is a means of pressurising the system with air
incorporate (in the connection of the pressurisation medium to the section)
suitably adjusted regulators and a full flow safety valve(s) to prevent
pressurisation above STP.
5.5.4
Appropriate gauges shall be provided to evaluate the test, duplicated where
necessary. Gauges shall be certificated for calibration and, if appropriate, zeroed
before use.
5.5.5
If the strength test is being combined, or is to be carried out concurrently, with
with the tightness test, all the preparations and all necessary calculations for the
tightness test (see Section 5) shall be carried out.
5.5.6
A final inspection of the pipework section shall be carried out to ensure that it is
ready for the test.
5.5.7
The pipework section shall be pressurised slowly and the pressure maintained at
STP for 5 mins.
5.5.8
After 5 mins, the pressure source shall be disconnected from the pipework
section and the 5 minute strength test duration (STD) shall start. The gauge
shall be monitored for the full test duration.
5.5.9
If the pressure drop exceeds 20% STP, joints, glands, etc. shall be tested for
leakage, using LDF (see also the Note to Table 1).
Once any repairs are complete, a further strength test may be carried out which
shall be in accordance with the above requirements.
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IGEM/UP/1A Edition 3 (Draft for Comment)
5.5.10
Following a satisfactory strength test, the pressure in the pipework section
should be reduced to OP if the pipework is to have a tightness test carried out
immediately. The tightness test may then be carried out, having adjusted the
stablization time, in accordance with Section 5, i.e the tests are combined.
Otherwise, the pressure shall be vented and pipework left in a safe condition
until the tightness test is to be carried out.
Any component removed (see Sub-Section 5.4) shall be replaced if the tightness
test is carried out immediately or if it is required to be in place for the tightness
test.
5.5.11
The strength test shall be documented and included in any site Health and
Safety File. Results should be recorded on a formal certificate, a copy of which
should be given to the owner/operator of the pipework tested.
Note:
IGEM publishes suitable triplicate certificates in pads.
STP and MOP shall be recorded clearly and be available for reference by any
party subsequently working on the installation.
Note:
This algorithm does not show all necessary steps and the full requirements in Section 4
apply.
FIGURE 4 - FLOWCHART/DECISION
TESTING
ALGORITHM
FOR
STRENGTH
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IGEM/UP/1A Edition 3 (Draft for Comment)
SECTION 6 : TIGHTNESS TESTING
Tightness testing is carried out to ensure that pipework has a leak rate below a level which
could ever be considered to form a hazard caused by the size of the leak, assuming adequate
ventilation of the pipework has been provided.
On a new installation, the test is to verify that, within tolerances caused by the finite time for
testing and the accuracy of instruments, pipework is, predominately, gas tight i.e. has,
nominally, zero leakage.
On an existing installation, the test is to verify that, within tolerances caused by the finite time
for testing and the accuracy of instruments, pipework is, nominally, gas tight within acceptable
limits.
Note:
The test may be against isolation valves which may be relatively old and worn, so a defined maximum level
of leakage is permitted.
Even if the tightness test result is satisfactory, a smell of gas or a gas detector indicating the
presence of gas is not acceptable.
Some LDFs have an adverse effect on certain pipework materials. Consequently, any residual
fluid shall be washed thoroughly off the pipe.
If necessary, for example when joints are broken, temporary electrical continuity bonds shall
be installed before tightness testing.
6.1
GENERAL
6.1.1
New installations and extensions
Normally, testing of a new installation or extension should be carried out using
air.
A pipework section may be tested without certain components fitted, for
example by testing before they are installed. The components then should be
installed, the section re-pressurised and the joints checked with LDF at OP (see
the principles as detailed in Sub-Section 5.4).
Note:
All new installations/extensions have to be strength tested prior to being tightness tested.
6.1.2
Existing installations
6.1.2.1
A thorough survey of the pipework section, to detect any major integrity defect,
shall be carried out before testing.
Note:
This survey may entail checking the accuracy of any plans, any other information provided
and the mechanical integrity of the installation.
6.1.2.2
If the pipework section contains fuel gas, it shall be tested with the fuel gas.
6.1.2.3
If the pipework section is at atmospheric pressure and may contain air/fuel gas
mixture or air, it shall be tested assuming the installation contains air.
Note:
See Appendix 5 for typical scenarios.
6.1.2.4
Where it is not necessary to test any component of a meter installation, such a
component shall be isolated at the meter installation outlet valve/meter outlet
valve (MIOV/MOV), as appropriate.
6.1.2.5
If new pipework is connected to existing pipework and cannot be isolated from
the existing pipework for the purpose of tightness testing, the existing pipework
shall be tested as if new.
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IGEM/UP/1A Edition 3 (Draft for Comment)
6.1.2.6
Where a tightness test includes the section of pipework between an ECV and the
primary meter regulator, that section shall be tested at its OP using LDF or a
gas detector (see clause 4.1.4).
6.2
INSTALLATION VOLUME (IV)
6.2.1
General
6.2.1.1
The estimation of IV involves surveying the whole of the pipework section to be
tested, unless it is a very simple section (for example, one straight length of
pipe).
The total IV (IVt) (m3) should be calculated to two significant figures with
“rounding” being upwards only.
Note:
6.2.1.2
It is not advisable to round the calculations of IV of individual parts of a section as this may
cause the test to be more onerous than necessary.
Note shall be taken of the relevant dimensions of all components including any:




meter
pipe
fitting, including any regulator, bend, tee, etc .
pipework exposed to direct sunlight or high temperature
Note:

The tightness test result is valid only if the temperature of the section remains stable
throughout the period of the test.
inaccessible section of pipework.
Note:
For inaccessible pipework where there are different sizes of pipework of unknown
length, always assume the largest size for the maximum length.
6.2.1.3
When existing pipework is to be extended, then unless the new section can be
isolated from the existing section (allowing each section to be treated as
separate installation volumes), the total volume of the new and existing sections
will have to be less than 1 m3 (otherwise, IGEM/UP/1 shall be applied).
6.2.2
Calculations
IV total (t) = IV meter (m) + IV
calculated as follows:
(a)
pipe (p)
+ IV
fittings (f)
and the total IV (IVt) (m3) shall be
IV of meters (IVm)
Use Table 2 or for other meters, consult the meter manufacturer.
DESIGNATION
OF METER
G4/U6
G10/U16
G16/U25
G25/U40
G40/U65
G65/U100
G100/U160
RD or turbine
E6
Note:
IVm (m3)
0.008
0.025
0.052
0.105
0.129
0.270
0.304
Equivalent length of pipe based on connection size (see Table 3)
0.0024
The values above are based on the largest case sizes of meters typically in use in the UK.
For “Tin-case” meters, the installation volumes will need to be calculated from the case
dimensions. “Tin-case” meters all measure in imperial units, will be dated pre-1980 and
may be larger in volume.
TABLE 2 – TYPICAL INSTALLATION VOLUME (IV) OF METERS
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IGEM/UP/1A Edition 3 (Draft for Comment)
IV of pipe (IVp)
(b)
For a 1 m length of pipe, obtain the volume of the particular pipe as
given in Table 3. Multiply the value given by the length of the pipe in the
section.
Note:
Data obtained from a manufacturer or other appropriate source may be used
instead of Table 3.
MATERIAL AND
NOMINAL SIZE OF
PIPE
(mm)
(in)
Steel/stainless
steel/CSST
VOLUME OF 1 m
LENGTH OF PIPE
(m3)
MATERIAL AND
NOMINAL SIZE
OF PIPE
(mm)
VOLUME OF 1 m
LENGTH OF PIPE
(m3)
PE
15
½
.00024
20
.00019
20
¾
.00046
25
.00033
25
1
.00064
32
.00053
32
1¼
.0011
55
.0016
40
1½
.0015
63
.0021
50
2
.0024
75
.0029
65
2½
.0038
90
.005
80
3
.0054
125
.01
100
4
.009
180
.02
125
5
.014
150
6
.02
Copper
15
.00014
22
.00032
28
.00054
35
.00084
42
.0012
54
.0021
67
.0033
76
.0043
108
.0087
TABLE 3 - VOLUME OF 1 m LENGTH OF PIPE
(c)
IV of valves, fittings, pressure vessels, accumulators, etc. (IVf)
Add any additional volume caused by such components. In the event that
IVf cannot be calculated, add an additional 10% of the pipe volume (IVp).
(d)
Total IV (IVt)
IVt = IVm + IVp + IVf
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IGEM/UP/1A Edition 3 (Draft for Comment)
Example: A simple system. Meter is U65, volume of valves and fittings is unknown.
INSTALLATION VOLUME
Meter (IVm)
U65 Diaphragm Meter
Pipework (IVp)
12 m of 80 mm (Steel)
10 m of 35 mm (Copper)
IVm =
12 x 0.0054 =
10 x 0.00084 =
IVp =
Fittings (IVf)
0.1 x IVp
Total volume (IVt)
IVm+ IVp + IVf
6.3
0.100 m3
0.0648 m3
0.0084 m3
0.0732 m3
IVf =
0.00732 m3
IVt =
0.181 m3
TIGHTNESS TEST PRESSURE (TTP)
TTP shall be OP of the pipework.
6.4
TIGHTNESS TEST DURATION (TTD)
6.4.1
New installations and extensions
TTD shall be as specified in Table 4 or Table 5 as appropriate when using air as
the test medium.
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IGEM/UP/1A Edition 3 (Draft for Comment)
LPG/Air (SMG)
Up to 0.12
>0.12  0.18
>0.18  0.24
>0.24  0.30
>0.30  0.36
>0.36  0.42
>0.42  0.48
>0.48  0.54
>0.54  0.60
>0.60  0.66
>0.66  0.72
>0.72  0.78
>0.78  0.84
>0.84  0.90
>0.90  1
IV (m3)
NG
Up to 0.06
>0.06  0.09
>0.09  0.12
>0.12  0.15
>0.15  0.18
>0.18  0.21
>0.21  0.24
>0.24  0.27
>0.27  0.3
>0.3  0.33
>0.33  0.36
>0.36  0.39
>0.39  0.42
>0.42  0.45
>0.45  0.48
>0.48  0.51
>0.51  0.54
>0.54  0.57
>0.57  0.6
>0.6  0.63
>0.63  0.66
>0.66  0.69
>0.69  0.72
>0.72  0.75
>0.75  0.78
>0.78  0.81
>0.81  0.84
>0.84  0.87
>0.87  0.9
LPG
TIGHTNESS TEST
DURATION (TTD) (mins)
Up to 0.01
>0.01  0.02
>0.02  0.03
>0.03  0.04
>0.04  0.05
>0.05  0.06
>0.06  0.07
>0.07  0.08
>0.08  0.09
>0.09  0.1
>0.1  0.11
>0.11  0.12
>0.12  0.13
>0.13  0.14
>0.14  0.15
>0.15  0.16
>0.16  0.17
>0.17  0.18
>0.18  0.19
>0.19  0.20
>0.20  0.21
>0.21  0.22
>0.22  0.23
>0.23  0.24
>0.24  0.25
>0.25  0.26
>0.26  0.27
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
TABLE 4 - TIGHTNESS TEST DURATION (TTD) FOR NEW INSTALLATIONS
AND EXTENSIONS USING FLUID GAUGES WITH 0.5 MBAR
INCREMENTS
OR
ELECTRONIC
GAUGE
READING
TO
1 DECIMAL PLACE
IV (m3)
LPG/Air (SMG)
Up to 0.60
>0.60  0.90
>0.90  1
TIGHTNESS TEST
DURATION (TTD) (mins)
LPG/Air (SNG) or
NG
LPG
Up to 0.30
>0.30  0.45
>0.45  0.60
>0.60  0.75
>0.75  0.90
>0.90  1
Up to 0.09
>0.09  0.13
>0.13  0.18
>0.18  0.22
>0.22  0.27
>0.27  0.31
>0.31  0.36
>0.36  0.40
>0.40  0.45
>0.45  0.49
>0.49  0.50
2
3
4
5
6
7
8
9
10
11
12
TABLE 5 - TIGHTNESS TEST DURATION (TTD) FOR NEW INSTALLATIONS
AND EXTENSIONS USING AN ELECTRONIC GAUGE READING
TO 2 DECIMAL PLACES
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IGEM/UP/1A Edition 3 (Draft for Comment)
6.4.2
Existing installations
TTD shall be as specified in Table 6 using air or fuel gas as the medium.
IV (m3)
TIGHTNESS TEST DURATION (mins)
LPG/air or NG Installation
Test using
air
Test using
NG
Test using
air
Test using
LPG
2
3
5
2
2
3
6
4
5
10
14
19
3
5
7
9
8
9
10
5
6
6
N/A
N/A
 0.15
>0.15 ≤0.3
>0.3 ≤0.45
>0.45 ≤0.5
>0.5 ≤0.6
>0.6 ≤0.75
>0.75 ≤0.9
>0.9 ≤1
Note:
LPG Installation
The above times are calculated based on the principle of using either a fluid gauge with 0.5
mbar increments or electronic gauge reading to 1 decimal place and align with the
allowable pressure drops given in Tables 9 and 10. This does not preclude the use of a
more accurate gauge but the tightness test duration and maximum allowable pressure drop
remain the same.
TABLE 6 - TIGHTNESS
TEST
INSTALLATIONS
6.5
PROCEDURES
6.5.1
By-passing components
DURATION
(TTD)
FOR
EXISTING
If there is any component in the system to be tested that could trap pressure,
for example a regulator, a non-return valve, etc., the component concerned
shall be by-passed temporarily to equalize the pressure either side of the
component. All valves shall be open, by-passed or removed.
When constructing a by-pass, particular care shall be taken to use
materials/components and security (via anchorage, etc.) suitable for the test
pressure.
Note:
Account will not normally need to be made for hose relaxation.
Care shall be taken to avoid damage to regulator diaphragms, filters, etc.
6.5.2
Ambient conditions
Where a system includes above ground pipework, the test shall be carried out
when ambient conditions are stable.
Testing shall not be carried out if pipework would be exposed to direct sunlight
or other heat source during the test period.
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IGEM/UP/1A Edition 3 (Draft for Comment)
6.5.3
Testing new installations and extensions
Note:
Where a combined strength and tightness test is being carried out, steps (a) to (c) will be
within strength testing, steps (d) and (f) will not be necessary and step (e) will involve a
reduced stabilization time.
The following procedure shall be carried out:
(a)
Seal of the outlet of the section isolation valve / inlet to the section to be
tested with an appropriate fitting.
Visually inspect the installation and ensure all sections to be tested are
connected, all joints are correctly made and any exposed gasways (for
example, open ends) on the installation are sealed with an appropriate
fitting.
Note:
The scope of IGEM/UP/1A now includes appliances. Appliances do not, therefore,
need to be isolated from the test section but the advice in Sub-Section 6.6 applies.
(b)
Open all valves within the section.
(c)
Connect a suitable pressure gauge to a pressure test point on the section
(see clause 4.4.1).
(d)
Slowly raise the pressure in the section with air to the at least TTP (see
Sub-Section 6.3) then turn off the pressure source.
(e)
Allow the pressure and temperature within the section to stabilise for a
period equivalent to the tightness test duration (TTD) (see
Sub-Section 6.4) or for 6 minutes, whichever is the longer.
The test procedure shall not proceed until a stable reading is obtained.
Note:
There may still be a slight increase or decrease in the pressure reading on the
gauge during this period as the installation stabilises. Further time may need to be
allowed until a stable reading is obtained.
Where surrounding conditions are stable, the responsible engineer may judge the
installation to have stabilised before the time periods given.
(f)
If necessary, at the end of the stabilisation period re-adjust the pressure
to the TTP then turn off the pressure source.
(g)
Check for any movement (fall) of the gauge reading over the TTD.
(h)
If the pressure drop on the gauge is less than or equal to the values of
GRM given Table 7 the section shall be deemed to have passed the test.
Otherwise, the section shall be deemed to have failed the test.
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TYPE OF GAUGE
GRM
(mbar)
Fluid (increments of 0.5 mbar)
Electronic (1 decimal place)
Electronic (2 decimal places)
0.5
0.5
0.05
Note 1: The resolution of a gauge is different to its GRM. The resolution is the minimum
pressure change that it is possible to read on the display.
Note 2: Account will need to be taken of variable atmospheric conditions and other nearby
heat sources (see 6.6.2).
Note 3: The gauge has to remain in the same position for the duration of the test.
Note 4: If there is an increase in the pressure reading on the gauge during this period the
installation may still be stabilising and further time will need to be allowed until a
stable reading is obtained. Once a stable reading is obtained this stage in the test
procedure will have to be repeated.
TABLE 7 - TEST CRITERIA FOR NEW INSTALLATIONS
(i)
If the section fails the test, stop the test and either:


trace and repair the escapes(s) and re-test the section, or
the section must be left safe and the relevant section of the
installation disconnected and all exposed gasways sealed off with an
appropriate fitting.
If the section passes the test, de-pressurise the system.
(j)
Connect the complete installation and remove the pressure gauge and
any temporary by-pass and re-seal the test points / connections.
(k)
Re-pressurise the section with air to OP and check any joint affected by
actions following the test with LDF, repairing any escape.
(l)
Record the results of the tightness test on a formal certificate and pass a
copy to the responsible person.
Note:
(m)
IGEM publishes suitable triplicate certificates in pads.
If the section is connected to a live gas supply, immediately carry out a
commissioning purge in accordance with Section 7.
If the section is not connected to a live gas supply or the section is not to
be immediately purged, it must be made safe by disconnecting and
sealing all exposed gasways with an appropriate fitting.
Example
New pipework. IV = 0.52 m3. Water gauge.
If OP is 40 mbar, STP will be 100 mbar (2.5 MOP = 2.5 X 40 = 100 > 82.5 mbar – Table 1).
Stabilization time for strength test from Table 1 is 5 mins.
STD from Table 1 is 5 mins with pressure drop limited to 20% STP = 20 mbar (Table 2).
TTD is 18 minutes (Table 6).
Pressurise to 100 mbar and maintain for 5 mins strength test stabilization time.
Isolate pressurisation and monitor for 5 mins with an end pressure  80 mbar for a successful
strength test.
Lower the pressure by venting until pressure is 40 mbar.
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Commence tightness test stabilization time (18 minutes less 10 minutes already taken for strength
test) = 8 minutes.
Once stabilization is complete, carry out the tightness test over 18 minutes with the gauge dropping
by less than 0.5 mbar (Table 4).
If test fails, trace and repair the leak and re-test. This will entail a full 18 mins stabilization as fresh
air (or N2) will be in the pipe from re-pressurisation, following the repair.
Finally, replace any items removed from the pipework, and remove any by-passes. Re-pressurise
the system with air and test disturbed joints with LDF.
The pipework is now ready for purging.
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IGEM/UP/1A Edition 3 (Draft for Comment)
6.5.4
Testing existing installations
The following procedure shall be carried out:
(a)
Visually inspect the installation and ensure all sections to be tested are
connected, all joints are correctly made and any exposed gas ways (for
example, open ends) on the installation are sealed with an appropriate
fitting. Turn off all appliances.
Note:
The scope of IGEM/UP/1A includes appliances. Appliances do not, therefore, need
to be isolated from the test section but the advice in Sub-Section 6.6 applies.
(b)
Turn off the upstream section isolation valve.
(c)
Connect a suitable pressure gauge to a pressure test point on the section
(see clause 4.4.1).
(d)
Carry out a let-by test of the closed section isolation valve as follows:


adjust the pressure to approximately 50% OP
close the section isolation valve, if not already closed, and note the
gauge reading
Note:
If the pressure requires reducing to achieve the required test pressure at this stage
or any stage in the tightness testing process then any potential fuel gas or fuel
gas/air mixtures that are to be released will need to be vented to a safe area. See
clause 3.4 for guidance on the necessary safety precautions to be taken.
Check for any perceptible movement (rise) of the gauge reading (see
clause 4.2.3) over the period given in Table 8.
IV (m3)
>0.5
>0.8
≤0.5
≤0.8
≤1.0
LET-BY TEST
PERIOD (mins)
2
3
4
TABLE 8 - LET-BY TEST PERIOD
If there is no perceptible movement of the gauge reading the valve shall
be deemed to have passed the test. Otherwise, the valve shall be
deemed to have failed the test.
If the valve fails the test the cause shall be investigated and rectified.
In this situation the valve shall be checked for let-by by disconnecting its
outlet union and applying LDF to the valve barrel or ball.
If let-by is confirmed on an ECV connected to the end of a NG service
pipe, the appropriate Gas Emergency Service Call Centre shall be
immediately notified to enable them to arrange an effective repair. On no
account shall anyone other than an authorised operative working on
behalf of the Gas Emergency Service Provider (ESP) attempt to remove,
repair or dismantle the valve.
If let-by is confirmed on a MIV, the MAM shall be immediately notified to
enable them to arrange an effective repair. On no account shall anyone
other than an authorised operative working on behalf of the MAM
attempt to remove, repair or dismantle the valve.
In any event, if let-by is confirmed, the valve shall be repaired / replaced
before repeating this let-by test and proceeding with the tightness test.
If the repair cannot be completed, the installation must be made safe by
disconnecting the installation, as appropriate, and sealing all open ends
with an appropriate fitting and suspending further tests.
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Note:
(e)
If the valve appears satisfactory but there is still an increase in the pressure
reading on the gauge during this period, the pressure and/or temperature within
the installation may be stabilising. Time will need to be allowed until a stable
reading is obtained. Once a stable reading is obtained this stage in the test
procedure will have to be repeated. A major decrease in pressure is probably
attributable to an escape on the installation that will need to be rectified before
restarting the test.
Slowly raise the pressure in the section with air or fuel gas, as
appropriate, to the TTP (see Sub-Section 6.3) then turn off the pressure
source.
Note:
It is important not to permit air into pipework containing fuel gas or a fuel gas / air
mixture and not to permit fuel gas into pipework containing air or a fuel gas / air
mixture unless the installation is fully purged to either fuel gas or air as
appropriate, before the next stage of any works commences. For example, if
during tightness testing there may be a fuel gas / air mixture in the pipework this
must be fully purged to air prior to exposing any gasways.
Air or fuel gas/air mixtures have to be prevented from entering the upstream.
(f)
Allow the pressure and temperature within the section to stabilise or a
period equivalent to the tightness test duration (TTD) (see Sub-Section
6.4) or for 6 minutes, whichever is the longer.
The test procedure shall not proceed until a stable reading is obtained.
Note:
There may still be a slight increase or decrease in the pressure reading on the
gauge during this period as the installation stabilises. Further time may need to be
allowed until a stable reading is obtained.
Where surrounding conditions are stable, the responsible engineer may judge the
installation to have stabilised before the time periods given.
(g)
If necessary, at the end of the stabilisation period re-adjust the pressure
to the TTP then turn off the pressure source.
(h)
Check for any movement (fall) of the gauge reading over the TTD.
If the pressure drop on the gauge does not exceed the values given in
Tables 9 or 10 and there is no smell of gas, the installation shall be
deemed to have passed the test.. Otherwise, the section shall be deemed
to have failed the test.
Note:
Tables 9 and 10 use the value of IV and the volume of the smallest occupied space
or 60 m3 (if there is no occupied space), as appropriate, to determine the
maximum allowable pressure drop.
If there is an increase in the pressure reading on the gauge during this period the
installation may still be stabilising and further time will need to be allowed until a
stable reading is obtained. Once a stable reading is obtained this stage in the test
procedure will have to be repeated.
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IGEM/UP/1A Edition 3 (Draft for Comment)
IV (m3 )
TTD
TTD
(Test Using (Test Using
Air)
Fuel Gas)
VOLUME OF SMALLEST OCCUPIED SPACE (RV) (m3)
10
15
20
25
30
35
40
45
50
55
≥60
0.7
1.0
1.4
1.7
2.1
2.4
2.8
3.1
3.5
3.9
4.2
0.7
1.1
1.5
1.9
2.3
2.7
3.1
3.5
3.9
4.3
4.7
0.6
0.9
1.2
1.5
1.9
2.2
2.5
2.8
3.1
3.5
3.8
>0.25  0.3
0.5
0.7
1.0
1.3
1.5
1.8
2.1
2.3
2.6
2.9
3.1
>0.3
0.7
1.1
1.5
1.8
2.2
2.6
3.0
3.4
3.7
4.1
4.5
0.6
0.9
1.3
1.6
1.9
2.3
2.6
2.9
3.3
3.6
3.9
0.5
0.8
1.1
1.4
1.7
2.0
2.3
2.6
2.9
3.2
3.5
0.6
0.9
1.2
1.5
1.9
2.2
2.5
2.8
3.1
3.5
3.8
0.5
0.8
1.1
1.4
1.7
2.0
2.3
2.6
2.9
3.1
3.4
>0.55  0.6
0.5
0.7
1.0
1.3
1.5
1.8
2.1
2.3
2.6
2.9
3.1
>0.6
0.6
0.9
1.3
1.6
1.9
2.2
2.6
2.9
3.2
3.6
3.9
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2.7
3.0
3.3
3.6
0.5
0.8
1.1
1.4
1.7
1.9
2.2
2.5
2.8
3.1
3.4
0.5
0.8
1.1
1.4
1.7
2.0
2.3
2.6
2.9
3.2
3.5
0.5
0.8
1.1
1.4
1.6
1.9
2.2
2.5
2.8
3.0
3.3
0.5
0.7
1.0
1.3
1.5
1.8
2.1
2.3
2.6
2.9
3.1
0.5
0.8
1.1
1.3
1.6
1.9
2.2
2.5
2.7
3.0
3.3
0.5
0.7
1.0
1.3
1.5
1.8
2.1
2.3
2.6
2.9
3.1
 0.15
2
2
>0.15  0.2
>0.2
 0.25
3
 0.35
>0.35  0.4
>0.4
2
3
5
 0.45
>0.45  0.5
>0.5
 0.55
6
 0.65
>0.65  0.7
>0.7
4
5
8
 0.75
>0.75  0.8
>0.8
 0.85
6
9
>0.85  0.9
>0.9
 0.95
6
>0.95  1.0
10
Note 1: For RV between two stated values, assume the lower value e.g. for RV = 42 m3, use 40 m3.
Note 2: For a fluid gauge, where appropriate, round the maximum allowable pressure drop
downwards to the next lower 0.5 mbar e.g. for 1.3 mbar, use 1.0 mbar, for 1.8 mbar, use
1.5 mbar.
TABLE 9 - DETERMINATION OF MAXIMUM ALLOWABLE PRESSURE DROP
(TEST
CRITERIA)
ON
EXISTING
LPG/AIR
AND
NG
INSTALLATIONS
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IGEM/UP/1A Edition 3 (Draft for Comment)
IV (m3 )

TTD
TTD
(Test Using (Test Using
Air)
Fuel Gas)
0.15
3
5
>0.15  0.2
>0.2
 0.25
5
10
>0.25  0.3
>0.3
 0.35
>0.35  0.4
>0.4
7
14
 0.45
>0.45  0.5
9
19
VOLUME OF SMALLEST OCCUPIED SPACE (RV) (m3)
10
15
20
25
30
35
40
45
50
55
≥60
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.9
2.1
2.3
2.5
0.6
0.9
1.2
1.5
1.9
2.2
2.5
2.8
3.1
3.4
3.8
0.5
0.7
1.0
1.2
1.5
1.7
2.0
2.2
2.5
2.7
3.0
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.9
2.1
2.3
2.5
0.5
0.7
1.0
1.2
1.5
1.7
2.0
2.2
2.5
2.7
3.0
0.4
0.6
0.8
1.1
1.3
1.5
1.7
2.0
2.2
2.4
2.6
0.3
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
2.1
2.3
0.4
0.7
0.9
1.2
1.4
1.6
1.9
2.1
2.4
2.6
2.8
Note 1: For RV between two stated values, assume the lower value e.g. for RV = 42 m3, use 40 m3.
Note 2: For a fluid gauge, where appropriate, round the maximum allowable pressure drop
downwards to the next lower 0.5 mbar e.g. for 1.3 mbar, use 1.0 mbar, for 1.8 mbar, use
1.5 mbar.
TABLE 10 - DETERMINATION
OF
MAXIMUM
ALLOWABLE
PRESSURE DROP (TEST CRITERIA) ON EXISTING
PROPANE INSTALLATIONS
(i)
If the section fails the test, stop the test, and either:


trace and repair the escapes(s) and re-test the section, or
the section must be left safe and the relevant section of the
installation disconnected and all exposed gasways sealed off with an
appropriate fitting.
If the section passes the test, carry out the following test any joint within
an enclosed space of 10 m3 of less, for example an adequately ventilated
duct or a small storeroom, with LDF or a gas detector (see clause 4.1.4).
If air is the test medium, only LDF can be used. The criteria for
acceptance is no bubble using LDF or no perceptible movement from 0%
LFL on the 0 – 10% scale for a gas detector.
(j)
When pipework passes through an inadequately ventilated area, reliance
shall not be placed on the outcome of the pressure drop on the gauge
documented in (i) alone.
One or more of the following procedures shall be used:



if access is available to all joints in the area, test each joint using LDF
or a gas detector (see clause 4.1.4). If air is the test medium, only
LDF can be used. The criteria for acceptance is no bubble using LDF
or no perceptible movement from 0% LFL on the 0 – 10% scale for a
gas detector or, if not practicable,
physically isolate any inaccessible pipework section in the area
without reliance on valves, for example by spading off, then test the
section as if new pipework or, if not practicable,
test the whole installation as if new pipework.
These additional tests help ensure in all instances, pipework in an
inadequately ventilated area shall be proven to be gas tight to at least
the standards for a new installation.
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Note :
Where necessary, for example when entering an inadequately ventilated area, due
attention must be paid to the Confined Spaces Regulations.
(k)
Where there is no access to any particular section, the section shall be
physically isolated without reliance on the use of valves, for example by
spading off, then tested separately as a new section with respect to TTD.
(l)
Remove the pressure gauge any temporary by-pass and re-seal the test
points / connections. Ensure the section is pressurised with either air or
fuel gas to OP, as appropriate, and check any joint affected by actions
following the test with LDF, repairing any escape.
(m)
Record the results of the tightness test on a formal certificate and pass a
copy to the responsible person.
Note:
(n)
IGEM publishes suitable triplicate certification in pads.
If the section installation is connected to a live gas supply, either:



if the section contains or potentially contains fuel gas or a fuel gas/air
mixture and work is to be completed on the section or the section is
to be permanently decommissioned, immediately carry out a
decommissioning purge in accordance with Section 7. The section
must then be made safe by disconnecting and sealing all exposed
gasways with an appropriate fitting; or
if the section contains or potentially contains air, fuel gas or a fuel
gas / air mixture and no work further work is to be completed on the
section, immediately carry out a commissioning purge in accordance
with Section 7; or
if the section is known to contain fuel gas only, no further action is
required.
If the section is not connected to a live gas supply, but may contain a
fuel gas or a fuel gas / air mixture, immediately carry out a
decommissioning purge in accordance with Section 7. The section must
then be made safe by disconnecting and sealing all exposed gasways
with an appropriate fitting.
Example
An existing section is to be tested using gas, having an installation volume of 0.48 m3 and passing
through a smallest occupied space of dimension 3 m x 3 m x 2.55 m, using a water gauge.
Volume of space
TTD
Maximum allowable pressure drop
=
=
=
(3 X 3 X 2.55) = 22.95 m3
4 minutes (Table 8)
1.4 mbar (Table 5).
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IGEM/UP/1A Edition 3 (Draft for Comment)
6.6
APPLIANCE CONNECTOR
6.6.1
This section applies to appliances connectors with an installation volumes not
exceeding:



LPG / air - 0.24 m3
NG - 0.12 m3
LPG - 0.03 m3
For pipework volumes exceeding those listed above, the appliance connector
shall be tightness tested in accordance with clause 6.5.
6.6.2
Before commissioning or re-commissioning any appliance, a tightness test shall
be carried out on the pipework in the appliance connector after the AIV.
For new installations a strength test, tightness test and purge certificate shall be
obtained for the upstream pipework prior to commencing work on the appliance
connector.
Note 1: The prescribed tightness test does not guarantee tightness of joints downstream of any
SSOV within an appliance.
Note 2: The manufacturing standards for gas appliances allow a very small leakage, for practical
reasons. This could create a discernible pressure drop when complete systems are tested,
particularly if the pipework and appliance internal volume is small.
6.6.3
Visually inspect the appliance connector and ensure all sections to be tested are
connected, all joints are correctly made and any exposed gas ways (for
example, open ends) on the appliance connector are sealed with an appropriate
fitting.
If there is any component in the system to be tested that could trap pressure,
for example a regulator, a non-return valve, etc., the component concerned
shall be by-passed temporarily to equalize the pressure either side of the
component (see clause 6.5.1).
6.6.4
Turn off the AIV
6.6.5
Connect a suitable pressure gauge to a pressure test point on the appliance
connector (see clause 4.4.1).
6.6.6
Carry out a let-by test of the closed AIV as follows:


adjust the pressure to approximately 50% OP
close the AIV, if not already closed, and note the gauge reading.
Note:
If the pressure requires reducing to achieve the required test pressure at this stage or any
stage in the tightness testing process then any potential fuel gas or fuel gas/air mixtures
that are to be released will need to be vented to a safe area. See clause 3.4 for guidance on
the necessary safety precautions to be taken.
Check for any perceptible movement (rise) of the gauge reading (see clause
4.2.3) over the next 2 minute period
If there is no perceptible movement of the gauge reading the AIV shall be
deemed to have passed the test. Otherwise, the AIV shall be deemed to have
failed the test.
If the AIV fails the test the cause shall be investigated and rectified.
In this situation the valve shall be checked for let-by by disconnecting its outlet
union and applying LDF to the valve barrel or ball.
In any event, if let-by is confirmed, the AIV shall be repaired / replaced before
repeating this let-by test and proceeding with the tightness test.
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IGEM/UP/1A Edition 3 (Draft for Comment)
If the repair cannot be completed, the appliance must be made safe by
disconnecting the appliance and sealing all exposed gasways with an
appropriate fitting and suspending further tests.
Note:
6.6.7
If the AIV appears satisfactory but there is still an increase in the pressure reading on the
gauge during this period, the pressure and/or temperature within the installation may be
stabilising. Time will need to be allowed until a stable reading is obtained. Once a stable
reading is obtained this stage in the test procedure will have to be repeated. A major
decrease in pressure is probably attributable to an escape on the installation that will need
to be rectified before restarting the test.
Slowly raise the pressure in the appliance connector with air or gas, as
appropriate, to the TTP (see Sub-Section 6.3) then turn off the pressure source.
Note:
It is important not to permit air into pipework containing fuel gas or a fuel gas / air
mixture and not to permit gas into pipework containing air or a fuel gas / air
mixture unless the installation is fully purged to either fuel gas or air as
appropriate, before the next stage of any works commences. For example, if
during tightness testing there may be a fuel gas / air mixture in the pipework this
must be fully purged to air prior to exposing any gasways.
Air or fuel gas / air mixtures have to be prevented from entering the upstream
supply
6.6.8
Allow 2 minutes for the pressure and temperature within the installation to
stabilise, if necessary, at the end of the stabilisation period re-adjust the
pressure to the TTP. If the AIV has been turned on to re-adjust the pressure
then turn off the valve.
The test procedure shall not proceed until a stable reading is obtained.
Note: There may still be a slight increase or decrease in the pressure reading on the gauge during
this period as the installation stabilises. Further time may need to be allowed until a stable
reading is obtained.
Where surrounding conditions are stable, the responsible engineer may judge the installation
to have stabilised before the time period given.
6.6.9
Check for any perceptible movement (fall) of the gauge reading (see
clause 4.2.3) over the next 2 minute period.
If there is no perceptible movement (fall) of the gauge reading and there is no
smell of gas the appliance connector shall be deemed to have passed the test.
Otherwise, the appliance connector shall be deemed to have failed the test.
6.6.10
If the appliance connector fails the test, either:


trace and repair the escapes(s) and re-test the appliance connector, or
the appliance must be made safe by disconnecting the appliance and sealing
all exposed gasways with an appropriate fitting.
6.6.11
Remove the pressure gauge and any temporary by-pass and re-seal any test
points / connections. Ensure the section is pressurised with either air or fuel gas
to OP, as appropriate, and check any joint affected by actions following the test
with LDF, repairing any escape.
6.6.12
Upon completion of the test:

if the appliance connector contains or potentially contains air, fuel gas or a
fuel gas/air mixture and no work further work is to be completed on the
appliance connector, immediately carry out a commissioning purge in
accordance with Section 7 and commission / re-commission the appliance in
accordance with the manufacturer's instructions and in compliance with
GS(I&U)R; or
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
if the appliance connector is known to contain fuel gas only, commission / recommission the appliance in accordance with the manufacturer's instructions
and in compliance with GS(I&U)R; or

if the appliance cannot be commissioned/re-commissioned the appliance must
be made safe by disconnecting and sealing all exposed gasways with an
appropriate fitting, carrying out a decommissioning purge in accordance with
Section 7, as required, on the appliance connector. Attach an appropriate
label to the appliance indicating it is not commissioned.
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Note:
This algorithm does not show all necessary steps and the full procedures in Section 6 apply.
FIGURE 5 - FLOW CHART/DECISION ALGORITHM FOR TIGHTNESS
TESTING OF NEW INSTALLATIONS AND EXTENSIONS
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Note:
This algorithm does not show all necessary steps and the full procedures in Section 6 apply.
FIGURE 6 - FLOW CHART/DECISION ALGORITHM
TESTING OF EXISTING INSTALLATIONS
FOR
TIGHTNESS
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SECTION 7 : DIRECT PURGING
This section deals with direct purging with air or fuel gas. If, for any reason, the purge is not
complete, it will be necessary to carry out an indirect purge using N2, guidance on which is
provided in Appendix 3.
These Procedures assume that the system will be pressurised during purging. However,
methods using suction (eduction) may also be appropriate (see IGE/SR/22).
7.1
GENERAL
7.1.1
The environmental impact of releasing methane into the atmosphere shall be
considered and the volume of vented gas should be minimised and, where
practicable, NG should be flared.
7.1.2
For LPG/Air and LPG, reference should be made to the advice contained in
Appendix 7 when assessing safety.
Heavier-than-air gases shall be flared.
7.1.3
A tightness test of pipework must be carried out immediately prior to any purge
admitting fuel gas. Vent points and flare points shall be leakage tested.
Note:
This equally applies when admitting N2 to be followed by fuel gas (see Appendix 3).
7.1.4
The pressure created during purging shall not exceed MOP of any pipework
being purged.
7.1.5
If compressed air from a cylinder is used for purging to air, the air shall be
supplied through high capacity regulators, appropriate precautions being taken.
7.1.6
Where pipework is to be taken permanently out of use, it shall be isolated
physically, for example by spading or removing a section of pipework and
sealing the ends.
De-commissioned pipework shall be left purged to air.
7.1.7
Where pipework is to be taken temporarily out of service for repairs or
alterations, a let-by test shall be carried out on any valve(s) to be used to
isolate the section (see clause 7.6.2(c)). Where pipework is left unattended, it
shall be isolated physically, for example by spading or, where not practicable, by
reliably locking off to prevent unauthorised operation.
7.2
PLANNING AND SUPERVISION
7.2.1
A full description of the system pipework shall be available and the accuracy of
plans and other available information shall be checked.
7.2.2
Purging of a primary meter shall be carried out only with the prior agreement of
its owner.
7.2.3
Purging shall be planned carefully and the following procedures shall be
undertaken:


determine the required number of operatives

survey the pipework section to establish that it is in a satisfactory condition.
Any defect shall be corrected before any purging is undertaken, unless decommissioning
check for the existence of a “ring main” system. If a ring main exists,
divide/sectionalise the “ring main” to enable complete purging
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
except for the simplest of purging operations, prepare a written procedure
for the operation. If it is anticipated that cutting or welding of any part of the
system may take place after completion of purging, a purging certificate
should be issued.
7.2.4
During the purging operation, all other work on the section being purged shall
be prohibited.
7.2.5
The complete purge procedure shall be continuous (except as given in the Notes
to clause 7.11.1(b) and 7.11.2(d) and the minimum purge volume rates given in
Table 11 shall be achieved.
Note:
It is not a requirement to purge at MOP. In general, if purge points are sized adequately,
the minimum required velocity will be achieved more easily at lower pressures.
If it becomes immediately apparent that a direct purge will not achieve the
required flow rate, the restriction may be removed and the purge re-started.
Otherwise, an indirect purge via N2 shall be carried out (see Appendix 3).
Consequently, planning shall take into account the need for sufficient quantities
of N2 to be available.
Throughout purging, it should be ensured that the pressure does not fall to a
level that could affect the operation of any appliance installed upstream of the
section being purged.
7.2.6
Purge points shall be located at the remote end of each branch of pipework to
be purged.
7.2.7
Purge points shall be located as close as possible to the extremities of the
section to be purged to enable a complete purge.
7.2.8
When purging with air, it must be ensured that air will not enter the GT’s
distribution network.
7.2.9
Planning shall cover the progression of the purging operation through any meter
and/or branched pipework (which should be purged in reducing order of
diameter).
Note:
Special care is needed to ensure that any branch interconnection is purged fully.
7.3
SITE PRECAUTIONS
7.3.1
Warning notices and labels
7.3.1.1
Appropriate “No smoking” and/or “No naked lights” signage shall be displayed
prominently around any vent and the overall area where purging will take place.
7.3.1.2
Any valve to or from the section to be purged shall be labelled clearly, for
example “Do not operate – purging in progress”.
7.3.2
Electrical and fire
7.3.2.1
An appropriate communications system shall be used for co-ordinating remote
activities associated with purging. Where appropriate, due regard shall be paid
to the suitability of this and any other electrical equipment for use in a
hazardous area (see Sub-Section 4.1.4).
7.3.2.2
Any fitted electrical continuity bonds shall be maintained throughout the purging
operation.
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7.3.2.3
Sufficient and appropriate fire extinguishers shall be situated near the vent
point(s).
7.4
DESIGNING AND POSITIONING PURGE POINTS, HOSES AND VENT
STACKS
7.4.1
Precautions shall be taken to reduce, as far as possible, the hazards associated
with venting, for example by avoiding venting close to property air intakes, or to
any potential sources of ignition such as street lamps and electrical plant. If
there is any doubt about the minimum clearance to ignition sources, reference
should be made to IGE/SR/23. Any electrical switch or isolator in the vicinity of
the vent outlet shall not be operated during purging. Purged fuel gas shall be
flared whenever a potential hazard cannot be eliminated (see also clauses 7.1.1
and 7.1.2).
Consideration should be given to potential complaints of smell arising from any
purging operation.
7.4.2
Purge points, associated vents, hoses, vent stacks and flame arrestors shall be
sized to permit sufficient flow in order to maintain the required purge flow rate.
In the absence of more definitive guidance, Table 11 should be used.
Note:
Where the minimum required size of purge hose and vent stack cannot be achieved,
multiple vents may be used. These may be operated simultaneously, provided each point is
supervised and communications are adequate to enable a safe purge.
Any valve used in the purge process should be full bore, where possible.
7.4.3
If flaring, the flare stack should be fitted with a suitable in-line flame arrestor to
BS EN 12874.
If venting but not flaring, the vent stack should terminate with a suitable flame
arrestor.
Note:
Where the purge flow rate can be guaranteed, it may not be necessary to fit an arrestor but
suitable additional precautions are required (see IGE/UP/1).
7.4.4
Any vent stack shall incorporate a full bore control valve and sample point.
7.4.5
For flaring, the arrestor shall be fitted at least 2 m upstream of the discharge
end and a source of ignition provided.
7.4.6
Any purge hose shall be of sufficient diameter to minimise pressure loss through
the vent pipe and shall be:



suitable for containing the fuel gas

earthed suitably to avoid sparking, if necessary, for example for externally
armoured hose.
gas tight
secured firmly to the purge point
Note:
Unsecured push-on connections are not acceptable.
Hose materials that may generate static electricity, for example PE, shall not be
used.
Note:
The possibility of generating static electricity increases as the purge velocity increases.
7.4.7
The vent/flare outlet shall be located in open air and terminate at least 2.5 m
above ground. Any vent outlet shall be located at least 5 m downwind of any
potential ignition source.
7.4.8
Precautions shall be taken to prevent vented gas drifting into buildings.
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7.4.9
7.4.10
When flaring, the flame shall be at a location that minimises heat radiation
effects that could lead to danger to persons or property.
When purging volumes of pipework and appliance control trains less than
0.035 m3, purging may be carried out directly into a well ventilated internal area
without the use of a purge hose, vent stack or flame arrestor, in accordance
with Appendix 6.
7.5
VERIFICATION OF PURGE FLOW RATE
7.5.1
A method of verifying that the required purge velocity (Table 11) is achievable
shall be available and shall be one of the following:


a suitably sized “volume” meter (used in conjunction with a timer to enable
the flow rate to be calculated) already fitted in the section of pipework to be
purged or
a sufficiently sized “rate of flow” meter, i.e. capable of passing well in excess
of the purge flow rate or other suitable flow measuring device fitted
downstream of the purge point(s), such as an independent positive
displacement or turbine meter.
Note:
Provided there is confidence that the required purge flow rate (Table 11) will be achieved, a
timed passage of purge gas may be used at the discretion of a responsible, competent
person.
7.5.2
A test of the vent gas shall always be carried out (see Sub-Section 7.10).
7.6
IDENTIFICATION OF PURGE GAS CYLINDERS
When the purge gas is supplied from a cylinder, special care shall be taken to
ensure that the cylinder does not contain the wrong gas, for example oxygen.
Cylinders of air shall be checked in this respect, before use.
Note:
7.7
This can be achieved, for example by using an oxygen detector, or by confirmation of the
contents of the cylinder from the supplier, etc.
GAS DETECTORS AND OTHER ELECTRONIC EQUIPMENT
Any gas detector or other electronic equipment shall:


where necessary, be certified for use in a hazardous area (see clause 4.1.4)


have its batteries tested prior to use

be operated in accordance with the manufacturer’s instructions and by a
trained competent person capable of interpreting the results obtained
be zeroed at the commencement of each test and have its zero checked at
the finish of each test
be tested, overhauled and calibrated in accordance with the manufacturer’s
instructions.
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7.8
GAS APPLIANCES
Where a connected appliance is identified which has not been commissioned,
either it must be:
 disconnected from the gas supply or sealed off with an appropriate fitting
with an appropriate label attached indicating the appliance is not
commissioned, or
 the appliance commissioned in accordance with the manufacturer's
instructions and in compliance with GS(I&U)R.
7.9
DETERMINATION OF THE PURGE VOLUME, PURGE FLOW RATE AND
PURGE TIME
7.9.1
The purge volume (PV) is the total volume that should be passed through the
installation to ensure a safe air to gas ratio.
The volume of the purge equipment (IVh) should be included in determining the
purge volume.
Note:
Purge equipment include items such as purge hoses/pipes, meters, vent stacks etc. The
principles in Section 6.2.2 may be used for calculating IVh.
PV = 1.5 x (IVt + IVh).
7.9.2
To ensure that the effect of stratification does not impair the purging of the
pipework, it should be confirmed that the velocity of the purging medium
through the pipe is above a minimum level (0.6 m s-1).
Note:
7.9.3
Although velocity is not easily measured in such a situation, it can be related to purge flow
rate which can be monitored with a flow meter or a timing method (see Table 11).
The minimum purge flow rate (Qp) through the pipework section shall be
determined from Table 11. The largest diameter pipe in the section shall be
used to determine the value.
Note:
If Qp is not achieved, the purge time and volume of purge gas required will be excessive
and, even then, a satisfactory purge may not be achieved as the minimum velocity
required, the key factor, will also not be achieved.
Largest nominal
diameter (mm)
Minimum purge
gas flow rate (Qp)
(m3 h-1)
Purge point
nominal bore
Purge hose/vent
stack nominal bore
Flame arrestor
nominal bore
Note:
20
25
32
40
50
80
0.7
1.0
1.7
2.5
4.5
11.0
20
20
20
20
25
25
100
125
150
30.0
38.0
25
40
40
20.0
20
20
20
20
40
40
40
50
50
20
20
20
20
50
50
50
50
50
While the dimensions of nominal bore are ideal, it may be necessary to defer to the
relevant design standard which may not require such dimensions. In any event, the
minimum required purge velocity has to be achieved.
TABLE 11 - MINIMUM PURGE FLOW RATE
7.9.4
Where necessary (see clause 7.5.1) the maximum purge time (PT) shall be
calculated as follows:
Max PT (sec) = PV (m3) x 3600
Qp
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Note:
This is the maximum time (purge time) it will take before a vent gas test indicates a
sufficient quantity of fuel gas or air as appropriate to indicate completion of the purge.
Example. Calculation of purge time
What is the maximum purge time of 75 m of 80 mm nominal bore steel pipe?
There is a U25 diaphragm meter fitted and the purge hose is 10 m of 25 mm nominal bore hose.
From Sub-Section 5.2
IVp
=75 x 0.0054
IVf
=10% x IVp
PV of pipework
=1.5 x (0.405 + 0.0405)
Meter cyclic volume
PV of meter
=5 x cyclic volume (= 5 x 0.01)
Purge hose volume
=10 x 0.00064
PV of purge hose
=1.5 x 0.0064
Total purge volume is, thus ( 0.6683 + 0.05 + 0.0096)
Minimum purge flow rate
Maximum purge time = 0.73 x 3600
11
=0.405 m3
=0.0405 m3
=0.6683 m3
=0.01 m3
=0.05 m3
=0.0064 m3
=0.0096 m3
=0.73m3
(rounding up)
= 11 m3h-1 (Table 9)
= 238.9 seconds
=3 minutes 59 seconds
7.10
VENT GAS TESTING
7.10.1
The criteria given in Table 12 shall be used when testing the vent gas.
Note:
FUEL GAS
LPG/Air
Table 12 is intended to ensure safe conditions, but not necessarily efficient combustion
performance.
FLAMMABILITY LIMITS
LOWER LIMIT
UPPER LIMIT
% GAS IN AIR % GAS IN AIR
2.0
10.0
NG
4.5
15.5
Propane
2.1
10.0
SAFE PURGE END POINTS
DIRECT PURGE
DIRECT PURGE
AIR TO GAS
GAS TO AIR
90% fuel gas
< 10% LFL
(0.2% gas in air)
90% fuel gas
< 40% LFL
(1.8% gas in air)
90% fuel gas
< 10% LFL
(0.2% gas in air)
TABLE 12 - FLAMMABILITY LIMITS AND SAFE PURGE END POINTS
7.11
PURGING PROCEDURES WHEN VENTING TO OUTSIDE
7.11.1
Direct purging from air to gas i.e. commissioning
The procedure assumes that, prior to purging, any purge point and any valve on
any connected vent stack is closed, that the section isolation valve(s) is/are
closed and that any other valve within the section is open.
Typical purge equipment arrangements are illustrated in Appendix 8.
Throughout the purge operation, steps should be taken to ensure that any
upstream pipework or appliance will not be affected by the purging operation.
7.11.1.1
The following procedure shall be carried out:
(a)
Ensure that a satisfactory tightness test (Section 6) has been carried out,
immediately before starting the purge.
(b)
Open all purge points on the section being purged and open valves on
connected vent stacks then open the section isolation valve, to admit
gas. Simultaneously, start the chosen method of measuring the flow of
purge gas (Sub-Section 7.5), i.e.;
 start a timer and
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
read the in-line meter or read the flow meter rate.
Note:
If using a flow meter, it will be immediately apparent if the minimum required
purge volume rate is not being achieved. In this case, it may be possible to stop
the purge by turning off the section isolation valve and quickly (and without
significant mixing of air and gas) rectify the reason for the incomplete purge and
re-start the purge (from the beginning) without resorting to a decommissioning
purge (see (d) below).
(c)
After half the estimated purge time has elapsed (or earlier if desired),
start testing the concentration of fuel gas in the vent gas using a suitable
gas detector.
(d)
Stop the purge by closing the vent stack valve(s) (and record the on-line
meter reading, if applicable) when a level of fuel gas, as indicated in
Table 12 for safe purge end point, is achieved, or the metered purge
volume has passed.
Note:
Any method has to be verified by a satisfactory vent gas sample.
If Table 12 concentrations are not achieved within the purge time (or by
the time the purge volume has passed) an incomplete purge is indicated.
In this case, close the section isolation valve(s) and immediately purge
the section with N2 in accordance with Appendix 3. Before repeating
steps (a) to (d), identify and rectify the reason for the incomplete purge.
Note1:
For any "partially complete" purge, the pipework will contain a mixture of gas and
air that is potentially hazardous. If it is possible to rectify the problem without
opening the gasway, then it may be acceptable to so rectify and re-start the purge
from the beginning. In the intervening period, it is imperative that the gasway is
not opened, that any section isolation valve is not opened, that the section is not
left unattended and that site precautions remain in place. An overall risk
assessment is required which, if sufficient assurance of safety is not indicated, will
lead to an indirect purge using N2 (see Appendix 3).
Note2:
The reason for an incomplete purge is likely to be insufficient velocity of the fuel
gas. Check the purge time recorded against any meter reading/ flow rate
recorded. Any metered reading less than PV is suspect. Any flow rate less than PV
expressed as a flow rate is also suspect. If both are satisfactory, re-check the
calculations. If no problem is found, it is likely that the actual design of the section
is not as assumed when calculating PV.
Note 3: In conjunction with a stopwatch for metered flow, all the above methods will serve
to confirm that the purge flow rate is the minimum required (see Table 9).
(e)
Close all purge points, disconnect vent stacks, remove all purge
equipment and plug or cap any exposed gasways with an appropriate
fitting. Test any disturbed joints with LDF or a gas detector (see clause
4.1.4).
Note 1: A gas detector is not permitted to move from zero or 0% LFL on a scale no less
accurate than 0% to 10% LFL.
Note 2: Disconnected purge equipment (hoses, meters, etc.) will need to be purged of fuel
gas.
(f)
Rectify the cause of any detected escapes or smell of gas.
(g)
Commission any connected appliances or seal the outlet of the pipework
and label all pipework termination points to indicate that gas is on and
purged up to each point. Confirm that outlets from appliance isolation
valves and/or branches are sealed with an appropriate fitting.
(h)
Complete an appropriate purging certificate.
Note:
IGEM publishes suitable triplicate certificates in pads.
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7.11.2
Direct purging from gas to air i.e. de-commissioning
The procedure assumes that, prior to purging, any purge point and any valve on
any connected vent stack is closed, that the section isolation valve is closed and
that any other valve within the section is open.
Any appliance attached to the section shall be turned off.
Throughout the purge operation, steps should be taken to ensure that any
upstream pipework or appliance will not be affected by the purging operation.
7.11.2.1
The following procedure shall be carried out:
(a)
Carry out a let-by test on the section isolation valve(s), to prove its/their
integrity (see clause 7.6.4 (c)).
(b)
Ensure the section isolation valve(s) is/are turned off.
(c)
Ensure OP of the section will not be exceeded.
Note:
(d)
This will require a suitable gauge to be fitted as close as practicable to the air inlet
point. Limiting the pressure can, normally, be achieved with the use of a lowpressure air blower(s) or, in the case of refillable cylinder(s)/tank(s), with the use
of a suitable regulator that can be accurately set to a pressure at or below OP.
Low-pressure air blower(s), cylinder(s)/tank(s), and regulator(s) need to be sized
to pass the required purge flow rate.
Open all purge points and valves on connected vent stacks then admit
air. Simultaneously, start the chosen method of "measuring" the flow of
air (see Sub-Section 7.5) i.e.;
 start a timer and
 read the in-line meter or read the flow meter rate.
Note:
If using a flow meter, it will be immediately apparent if the minimum required
purge volume rate is not being achieved. In this case, it may be possible to stop
the purge by turning off the air supply and quickly (and without significant mixing
of air and gas) rectify the reason for the incomplete purge and re-start the purge
(from the beginning) without resorting to a decommissioning purge (see (f)
below).
(e)
After half the estimated purge time has elapsed (or earlier if desired),
start testing the concentration of fuel gas in the vent gas using a suitable
gas detector.
(f)
Stop the purge by isolating the air supply (and record the in-line meter
reading, if applicable) when a level of gas, as indicated in Table 10 for
safe purge end point, is achieved or the metered purge volume has
passed, whichever occurs first.
Note:
Any method has to be verified by a satisfactory vent gas sample.
If Table 12 concentrations are not achieved within the purge time (or by
the time the purge volume has passed) an incomplete purge is indicated.
In this case, close the section isolation valve(s) and immediately purge
the section with N2 in accordance with Appendix 3. Before repeating
steps (a) to (d), identify and rectify the reason for the incomplete purge.
Note1:
For any "partially complete" purge, the pipework will contain a mixture of gas and
air that is potentially hazardous. If it is possible to rectify the problem without
opening the gasway, then it may be acceptable to so rectify and re-start the purge
from the beginning. In the intervening period, it is imperative that the gasway is
not opened, that any section isolation valve is not opened, that the section is not
left unattended and that site precautions remain in place. An overall risk
assessment is required which, if sufficient assurance of safety is not indicated, will
lead to an indirect purge using nitrogen (see Appendix 3).
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Note2:
The reason for an incomplete purge is likely to be insufficient velocity of the fuel
gas. Check the purge time recorded against any meter reading/ flow rate
recorded. Any metered reading less than PV is suspect. Any flow rate less than PV
expressed as a flow rate is also suspect. If both are satisfactory, re-check the
calculations. If no problem is found, it is likely that the actual design of the section
is not as assumed when calculating PV.
Note 3: Provided there is confidence that the required purge flow rate (Table 11) will be
achieved, a timed passage of purge gas may be used at the discretion of a
responsible, competent person.
(g)
Close all purge points, disconnect vent stacks, remove all purge
equipment and plug or cap any exposed gasways with an appropriate
fitting. Test any disturbed joints with LDF. Seal or disconnect pipework
from the gas supply, sealing all ends with an appropriate fitting.
Decommission in accordance with these Procedures.
(h)
Label all pipework to show that it has been de-commissioned.
(i)
Complete an appropriate purging certificate.
Note:
IGEM publishes suitable triplicate certificates in pads.
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IGEM/UP/1A Edition 3 (Draft for Comment)
AIR TO GAS
Commissioning
Start
Ensure that a satisfactory
tightness test has been
carried out.
Vent stacks and hoses
correctly located. Warning
notices, barriers, fire
extinguishers available and
checked. Test meters and
gas detectors checked.
Carry out all preparation
work.
(7.1, 7.2, 7.3, 7.4, 7.5)
Calculate:
Purge volume (7.6)
Purge flow rate (7.6)
Purge time (7.6)
Open purge points and vent
valves.
Immediately admit fuel gas
at correct flow rate.
Monitor gas pressure.
Do not allow to exceed OP.
Monitor gas flow rate.
If correct flow rate cannot be
achieved, abandon purge
and use indirect method.
Sample at vent point after
half the purge time.
After satisfactory vent gas
test, close vent point valve
and remove purge hose from
vent.
Check purge is complete.
(see Table 12)
Test all disturbed joints and
joints in ducts for leaks.
Complete records and inform
responsible person of
position.
Note: This algorithm does not show all necessary steps and the full procedures in Section 7 apply.
FIGURE 7 - FLOWCHART FOR DIRECT PURGING OF AIR TO GAS
43
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IGEM/UP/1A Edition 3 (Draft for Comment)
GAS TO AIR
De-commissioning
Start
Vent stacks and hoses
correctly located. Warning
notices, barriers, fire
extinguishers available and
checked. Test meters and
gas detectors checked.
Carry out all preparation
work.
(7.1, 7.2, 7.3, 7.4, 7.5)
Calculate:
Purge volume (7.6)
Purge flow rate (7.6)
Purge time (7.6)
Isolate gas supply.
Carry out let-by test.
Open purge points and vent
valves.
Immediately admit air at
correct flow rate.
Monitor gas pressure.
Do not allow to exceed OP.
Monitor gas flow rate.
If correct flow rate cannot be
achieved, abandon purge
and use indirect method.
Sample at vent point after
half the purge time.
After satisfactory vent gas
test, close vent point valve
and remove purge hose from
vent.
Check purge is complete.
(see Table 12)
Complete records and inform
responsible person of
position.
Note: This algorithm does not show all necessary steps and the full procedures in Section 7 apply.
FIGURE 8 - FLOWCHART FOR DIRECT PURGING OF GAS TO AIR
44
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IGEM/UP/1A Edition 3 (Draft for Comment)
APPENDIX 1 : GLOSSARY, ACRONYMS AND SYMBOLS
GLOSSARY
All definitions are given in IGEM/G/4 which is freely available by downloading a printable
version from IGEM’s website, www.igem.org.uk.
Recommended and legacy gas metering arrangements are given in IGEM/G/1 which is freely
available by downloading a printable version from IGEM’s website, www.igem.org.uk.
ACRONYMS
ACoP
ACS
ECV
GRM
GS(I&U)R
GT
HSE
IGEM
IV
LDF
LFL
LPG
LPGA
MAM
MIP
MIV
MOP
MOV
NDT
NG
OP
PE
PT
PV
RD
RV
SDR
SP
SSOV
STD
STP
TTD
TTP
UK
UKAS
Approved Code of Practice
Accredited Certification Scheme
Emergency control valve
Gauge readable movement
Gas Safety (Installation and Use) Regulations
Gas transporter
Health and Safety Executive
Institution of Gas Engineers and Managers
Installation volume
Leak detection fluid
Lower flammable limit
Liquefied petroleum gas
Liquefied Petroleum Gas Association
Meter asset manager
Maximum incidental pressure
Meter inlet valve
Maximum operating pressure
Meter outlet valve
Non-destructive testing
Natural Gas
Operating pressure
Polyethylene
Purge time
Purge volume
Rotary displacement
Room volume
Standard dimension ratio
Set point
Safety shut-off valve
Strength test duration
Strength test pressure
Tightness test duration
Tightness test pressure
United Kingdom
United Kingdom Accreditation Service.
SYMBOLS





Qp
N2
V
diameter
less than
greater than
equal to or greater than
less than or equal to
minimum purge flow rate
Nitrogen
volume.
45
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IGEM/UP/1A Edition 3 (Draft for Comment)
SUBSCRIPTS/SUFFICES/UNITS
f
p
m
t
d
L
m3
m3 h-1
ft3
ft3 h-1
m
mm
in
mins
mbar
fittings, etc.
pipe
meter
total
nominal bore
flange to flange dimension
cubic metre
cubic metre per hour
cubic feet
cubic feet per hour
metre
millimetre
inch
minute
millibar.
46
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IGEM/UP/1A Edition 3 (Draft for Comment)
APPENDIX 2 : REFERENCES
Care needs to be taken to ensure that the latest editions of the relevant documents are used.
A2.1
LEGISLATION



Construction (Design and Management) Regulations 1994

Control of Substances Hazardous to Health Regulations 1995 as amended in
1997 and 1998



A2.2
Note:
This applies to all work activities. It places general duties on employers to ensure, so far
is reasonably practicable, the health safety and welfare of their employees and the
health and safety of members of the public who may be affected by the activity.
Dangerous Substances and Explosive Atmospheres Regulations 2002
Electricity at Work Regulations 1989
Gas Safety (Installation and Use) Regulations 1998
Note:
These apply to domestic and commercial premises. For industrial premises, the
requirements of these Regulations could be considered relevant in any investigation
under the Health and Safety at Work etc. Act. The Regulations set out detailed
requirements for gas installation work. In particular, they require that anyone carrying
out such work must be competent to do so. They also prescribe circumstances in which
a soundness(tightness) test and purge must be carried out.
Management of Health and Safety at Work Regulations 1999

Workplace (Health, Safety and Welfare) Regulations 1992.
Pressure Equipment Regulations 1999
Pressure Systems Safety Regulations 2000
Note:
For cylinders etc., Carriage of Dangerous Goods (Classification, Packaging and
Labelling) and Use of Transportable Pressure Receptacles Regulations 1996 (as
amended), the Transportable Pressure Vessel Regulations 2001 may also be relevant.
ACOPS AND GUIDANCE NOTES
HSG48 Human factors in industrial safety.
BRITISH STANDARDS (ABBREVIATED TITLES)



A2.4
Health and Safety at Work etc. Act 1974




A2.3
Gas Act 1995
BS 6891
Low pressure pipework in domestic premises
BS EN 12874
Flame arresters
BS EN 60079
Electrical apparatus for explosive gas atmospheres.
IGEM PROCEDURES AND RECOMMENDATIONS

IGE/UP/1
Edition 2
Strength testing, tightness testing and direct purging of
industrial and commercial gas installations

IGEM/UP/1B
Edition 3

Tightness testing and direct purging of small Liquefied
Petroleum Gas/Air, Natural Gas and Liquefied Petroleum
Gas installations
IGEM/UP/2
Edition 2
Installation pipework on industrial and commercial
premises
IGE/SR/22
Purging operations for
distribution and storage



IGE/SR/23
Venting of Natural Gas
IGE/SR/24
Risk assessment techniques
IGEM/TD/13
Edition 2
Pressure regulating installations for Natural Gas, Liquefied
Petroleum Gas and Liquefied Petroleum Gas/Air

IGEM/G/1
Definitions for the end of a network, meter installation,
and installation pipework.

fuel
gases
in
transmission,
47
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IGEM/UP/1A Edition 3 (Draft for Comment)
APPENDIX 3 : INDIRECT PURGING WITH NITROGEN (N2)
An indirect purge is necessary if:


the direct purge has been unsuccessful
a direct purge is unlikely to be achieved successfully, for example where inadequatelysized purge points are fitted.
A3.1
Make the installation and the surroundings safe and implement fallback plans.
A3.2
Check the calculations, survey the installation and inspect equipment to
endeavour to identify the cause of failure of the direct purge.
If the cause is identified and can be rectified, (for example following calculation
error, blocked hose, closed valve, restrictive purge points, etc.), the direct purge
can be repeated.
Note:
A3.3
Take additional care at purge gas vent point due as a flammable mixture may occur at a
different stage in the operation.
Ensure the indirect purge is a complete displacement purge using volume based measurement of N2 and vent gas testing. Pay particular attention to any
dead-legs.
Take precautions to prevent asphyxiation, especially in basements and confined
spaces.
Take precautions to prevent N2 entering parts of the installation upstream of the
section being purged.
A3.4
Start with the largest diameter pipe and progress to the smallest.
Ensure a minimum volume equal to 1.5 times the swept volume of the pipework
is available.
A3.5
As a guide, a standard 1.5 m long N2 bottle usually has a capacity of 6.5 m3. The
maximum through a high capacity single-stage regulator is typically, 1 m3 per
minute.
A3.6
The criteria given in Table 13 apply when testing the vent gas.
A3.7
Following the indirect purge, identify the reason for any failure of the direct
purge. This may necessitate sectionalising the installation to identify blockages
etc.
A3.8
Following the indirect purge, if hot work is to be undertaken, take care in case
small pockets of gas remain in the pipe due to the effects of stratification or due
to the effect of dead-legs.
A3.9
When undertaking any work following an indirect purge, take suitable
precautions to account for the presence of N2.
A3.10
Once the purge to Nitrogen is complete, it is advisable to either then:
 purge to air and ensure the oxygen level is at least 20%, or
 label the pipework to indicate that it contained N2.
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IGEM/UP/1A Edition 3 (Draft for Comment)
FUEL GAS
LPG/Air
NG
Propane
FLAMMABILITY LIMITS
LOWER LIMIT
UPPER LIMIT
% GAS IN AIR % GAS IN AIR
2.0
4.5
2.1
10.0
15.5
10
SAFE PURGE
INDIRECT
PURGE FROM
FUEL GAS TO N2
3.5% gas in N2
7.5% gas in N2
3.5% gas in N2
END POINTS
INDIRECT PURGE
FROM N2 TO FUEL
GAS
90% fuel gas in N2
90% fuel gas in N2
90% fuel gas in N2
TABLE 13 - FLAMMABILITY LIMITS AND SAFE PURGE ENDS POINTS FOR
INDIRECT PURGE
49
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IGEM/UP/1A Edition 3 (Draft for Comment)
APPENDIX 4 : TIGHTNESS TEST DURATIONS FOR A WATER GAUGE
USING
THE
CONCEPT
OF
“NO
PERCEPTIBLE
MOVEMENT”(FOR NEW INSTALLATIONS ONLY)
For clarity, IGE/UP/1A Edition 2 adopts the concept of “gauge readable movement”. This is
because the meaning of “no perceptible movement” is open to differing interpretation with
respect to electronic gauges, which are seeing increased usage. However, in the case of a
water gauge, the use of “no perceptible movement” is an established and understood concept.
When testing a new installation, using this concept for a water gauge has the benefit of
significantly reducing the test times from those given in Table 4 which are based on GRM. The
table below gives the equivalent values for “no perceptible movement”.
Any movement of the gauge during the test time indicates the installation has failed the
tightness test.
LPG/Air (SMG)
Up to 0.12
>0.12  0.18
>0.18  0.24
>0.24  0.30
>0.30  0.36
>0.36  0.42
>0.42  0.48
>0.48  0.54
>0.54  0.60
>0.60  0.66
>0.66  0.72
>0.72  0.78
>0.78  0.84
>0.84  0.90
>0.90  1
IV (m3)
NG
Up to 0.06
>0.06  0.09
>0.09  0.12
>0.12  0.15
>0.15  0.18
>0.18  0.21
>0.21  0.24
>0.24  0.27
>0.27  0.3
>0.3  0.33
>0.33  0.36
>0.36  0.39
>0.39  0.42
>0.42  0.45
>0.45  0.48
>0.48  0.51
>0.51  0.54
>0.54  0.57
>0.57  0.6
>0.6  0.63
>0.63  0.66
>0.66  0.69
>0.69  0.72
>0.72  0.75
>0.75  0.78
>0.78  0.81
>0.81  0.84
>0.84  0.87
>0.87  0.9
>0.9  0.93
>0.93  0.96
>0.96  1.0
LPG
TIGHTNESS TEST
DURATION (TTD) (mins)
Up to 0.01
>0.01  0.02
>0.02  0.03
>0.03  0.04
>0.04  0.05
>0.05  0.06
>0.06  0.07
>0.07  0.08
>0.08  0.09
>0.09  0.1
>0.1  0.11
>0.11  0.12
>0.12  0.13
>0.13  0.14
>0.14  0.15
>0.15  0.16
>0.16  0.17
>0.17  0.18
>0.18  0.19
>0.19  0.20
>0.20  0.21
>0.21  0.22
>0.22  0.23
>0.23  0.24
>0.24  0.25
>0.25  0.26
>0.26  0.27
>0.27  0.28
>0.28  0.29
>0.29  0.3
2
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
11
11
12
12
13
13
14
14
15
15
16
16
17
TABLE 14 - TIGHTNESS
TEST
DURATION
(TTD)
FOR
NEW
INSTALLATIONS AND EXTENSIONS USING NO PERCEPTIBLE
MOVEMENT
50
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IGEM/UP/1A Edition 3 (Draft for Comment)
APPENDIX 5 : INSTALLATIONS AT ATMOSPHERIC PRESSURE CONSIDERATIONS/SCENARIOS
GS(I&U)R require a tightness test to always proceed a purge. The following gives advice on
scenarios which may be encountered.
A5.1
INSTALLATION KNOWN TO CONTAIN AIR ONLY
Initial tightness test of installation using TTD for an installation containing air
(Table 6).
Actions following initial successful test:
A5.2

No gas ways to be exposed to the atmosphere (e.g. no work to be
undertaken)
 direct purge the installation to fuel gas - commissioning purge (Section
7)

achieve satisfactory safe purge end point (>90% Gas)

purging for at least the maximum purge time or until PV has been
passed

Gas ways to be exposed to the atmosphere (e.g. work to be
undertaken)
 undertake & complete any work

tightness test installation using TTD for an installation containing air
(Table 9)

direct purge the installation to fuel gas - commissioning purge (Section
7)

achieve satisfactory safe purge end point (>90% Gas)

purging for at least the maximum purge time or until PV has been
passed
INSTALLATION CONTAINS OR POTENTIALLY CONTAINS GAS / AIR
MIXTURE
Initial tightness test of installation using TTD for an installation containing air
(Table 6)
Actions following successful test:

No gas ways to be exposed to the atmosphere (e.g. no work to be
undertaken)
 direct purge the installation to fuel gas - commissioning purge (Section
7)

achieve satisfactory safe purge end point (>90% Gas)

purging for at least the maximum purge time or until PV has been
passed

Gas ways to be exposed to the atmosphere (e.g. work to be
undertaken)
 direct purge the installation to air - de-commissioning purge (Section 7)

achieve satisfactory safe purge end point (<40% LFL)

purging for at least the maximum purge time or until PV has been
passed

undertake & complete any work
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IGEM/UP/1A Edition 3 (Draft for Comment)
A5.3

tightness test installation using TTD for an installation containing air
(Table 9)

direct purge the installation to fuel gas - commissioning purge (Section
7)

achieve satisfactory safe purge end point (>90% Gas)

purging for at least the maximum purge time or until PV has been
passed
INSTALLATION KNOW TO CONTAIN FUEL GAS ONLY
Initial tightness test of installation using TTD for an installation containing gas
(Table 6)
Actions following initial successful test:

No gas ways to be exposed to the atmosphere (e.g. no work to be
undertaken)
 Pressurise system - No further action required

Gas ways to be exposed to the atmosphere (e.g. work to be
undertaken)
 direct purge the installation to air - de-commissioning purge (Section 7)

achieve satisfactory safe purge end point (<40% LFL)

purging for at least the maximum purge time or until PV has been
passed


undertake & complete any work

direct purge the installation to fuel gas - commissioning purge (Section
7)

achieve satisfactory safe purge end point (>90% Gas)

purging for at least the maximum purge time or until PV has been
passed
tightness test installation using TTD for an installation containing air
(Table 9)
52
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IGEM/UP/1A Edition 3 (Draft for Comment)
APPENDIX 6 : PURGING SMALL VOLUMES
A6.1
LPG/Air mixtures
In accordance with clause 7.4.10 and where the OP at the inlet of the purge
valve does not exceed 21 mbar, the following procedure can be used for
purging:
(a) Within the vicinity of the purging activity ensure the following safety
precautions are taken throughout the purging process:





avoid any accumulation of gas within confined spaces

advise the responsible person for the premises or other persons in the
area of the above of the intent to purge and that there may be a smell of
gas.
prevent inadvertent operation of any electrical switch or other appliance
extinguish all potential sources of ignition
ensure that there is no smoking or naked lights
ensure good ventilation by opening doors, windows, passive stack
ventilation systems, etc.
Note:
These precautions are applicable even if a source of ignition is held adjacent to the
purged gas, as a mixture of un-ignited gas/air may be released until a suitable mixture
is achieved.
(b) Ensure that all appliances are turned off before commencing with the purge.
(c) Slowly turn on the gas supply and note the position of the test dial or test
drum on diaphragm meters.
(d) From a suitable purge point on the installation turn on a burner control tap
on an appliance with an open burner. The purge gas mixture shall be ignited
at the burner as soon as possible, by holding a source of ignition adjacent to
the burner head or by continually operating the appliances ignition system.
Note:
It may be necessary, in certain situations, to connect a temporarily installed burner to
a suitable point on the installation, for example, on installations with no appliances
fitted, where the appliance(s) is fitted with a flame supervision device or where there
are no open burners.
Confirm the presence of gas, for example, by observation of the burner
igniting. Turn off the appliance burner control tap.
During the purging operation, the area in which the purge gas is being
released shall not be left unattended.
(e) Return to the meter and note the volume of gas that has passed.
(f) Continue steps (d) and (e) until the correct PV has been passed (see
Table 5).
(g) Ensure every branch of pipework is purged following the aforementioned
procedure.
(h) Establish a stable flame picture at each appliance.
Where an appliance is identified which has not been commissioned, either it
must be:


disconnected from the gas supply or sealed off with an appropriate fitting
with an appropriate label attached indicating the appliance is not
commissioned, or
the appliance commissioned.
53
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IGEM/UP/1A Edition 3 (Draft for Comment)
A6.2
Natural Gas
In accordance with clause 7.4.10 and where the OP at the inlet of the purge
valve does not exceed 21 mbar, the following procedure can be used for
purging:
(a) Within the vicinity of the purging activity ensure the following safety
precautions are taken throughout the purging process:





avoid any accumulation of gas within confined spaces

advise the responsible person for the premises or other persons in the
area of the above of the intent to purge and that there may be a smell of
gas.
prevent inadvertent operation of any electrical switch or other appliance
extinguish all potential sources of ignition
ensure that there is no smoking or naked lights
ensure good ventilation by opening doors, windows, passive stack
ventilation systems, etc.
Note:
These precautions are applicable even if a source of ignition is held adjacent to the
purged gas, as a mixture of un-ignited gas/air may be released until a suitable mixture
is achieved.
(b) Ensure that all appliances are turned off before commencing with the purge.
(c) Slowly turn on the gas supply and note the position of the test dial or test
drum on diaphragm meters or the meter reading on ultrasonic meters.
(d) Select the appropriate purge activity based on the installation volume:

Installation Volumes ≤ 0.02 m3
From a suitable purge point on the installation either turn on a burner
control tap on an appliance with an open burner or loosen the
appropriate fitting sealing the gas way. If purging by opening a burner
control tap, it is permissible to hold a source of ignition adjacent to the
burner head or to continually operate the appliances ignition system to
attempt to ignite the purged gas/air mixture.
Note:
This not only serves to assist the operative in determining whether the PV has
been passed but will limit the amount of un-ignited purge gas that will be released.
Confirm the presence of gas, for example, by observation of the burner
igniting and/or by use of a gas detector to confirm a safe purge end point
of ≥ 90% fuel gas. Turn off the appliance burner control tap or tighten
the appropriate fitting, testing with LDF as required.
During the purging operation, the area in which the purge gas is being
released shall not be left unattended.

Installation Volumes > 0.02 m3 ≤ 0.035 m3
From a suitable purge point on the installation turn on a burner control
tap on an appliance with an open burner. The purge gas mixture shall be
ignited at the burner as soon as possible, by holding a source of ignition
adjacent to the burner head or by continually operating the appliances
ignition system.
Note:
It may be necessary, in certain situations, to connect a temporarily installed
burner to a suitable point on the installation, for example, on installations with no
appliances fitted, where the appliance(s) is fitted with a flame supervision device
or where there are no open burners.
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IGEM/UP/1A Edition 3 (Draft for Comment)
Confirm the presence of gas, for example, by observation of the burner
igniting. Turn off the appliance burner control tap.
During the purging operation, the area in which the purge gas is being
released shall not be left unattended.
(e) Ensure every branch of pipework is purged following the aforementioned
procedure.
(f) Establish a stable flame picture at each appliance.
Where an appliance is identified which has not been commissioned, either it
must be:


disconnected from the gas supply or sealed off with an appropriate fitting
with an appropriate label attached indicating the appliance is not
commissioned, or
the appliance commissioned.
55
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IGEM/UP/1A Edition 3 (Draft for Comment)
A6.3
LPG
In accordance with clause 7.4.10 and where the OP at the inlet of the purge
valve does not exceed 37 mbar, the following procedure can be used for
purging:
(a) Within the vicinity of the purging activity ensure the following safety
precautions are taken throughout the purging process:





avoid any accumulation of gas within confined spaces

advise the responsible person for the premises or other persons in the
area of the above of the intent to purge and that there may be a smell of
gas.
prevent inadvertent operation of any electrical switch or other appliance
extinguish all potential sources of ignition
ensure that there is no smoking or naked lights
ensure good ventilation by opening doors, windows, passive stack
ventilation systems, etc.
Note:
These precautions are applicable even if a source of ignition is held adjacent to the
purged gas, as a mixture of un-ignited gas/air may be released until a suitable mixture
is achieved.
(b) Ensure that all appliances are turned off before commencing with the purge.
(c) Slowly turn on the gas supply and when a meter is installed note the position
of the test dial or test drum on diaphragm meters or the meter reading on
ultrasonic meters.
(d) From a suitable purge point on the installation turn on a burner control tap
on an appliance with an open burner. The purge gas mixture shall be ignited
at the burner as soon as possible, by holding a source of ignition adjacent to
the burner head or by continually operating the appliances ignition system.
Note:
It may be necessary, in certain situations, to connect a temporarily installed burner to
a suitable point on the installation, for example, on installations with no appliances
fitted, where the appliance(s) is fitted with a flame supervision device or where there
are no open burners.
Confirm the presence of gas, for example, by observation of the burner
igniting. Turn off the appliance burner control tap.
During the purging operation, the area in which the purge gas is being
released shall not be left unattended.
(e) Upon establishing the presence of gas:

if the installation includes a meter, return to the meter and note the
volume of gas that has passed continuing steps (d) and (e) until the
correct PV has been passed (see Table 5).

if the installation does not include a meter proceed to step (f).
(f) Ensure every branch of pipework is purged following the aforementioned
procedure.
(g) Establish a stable flame picture at each appliance.
Where an appliance is identified which has not been commissioned, either it
must be:


disconnected from the gas supply or sealed off with an appropriate fitting
with an appropriate label attached indicating the appliance is not
commissioned, or
the appliance commissioned.
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IGEM, IGEM, IGEM House, High Street, Kegworth, Derbyshire, DE74 2DA. Website: www.igem.org.uk
IGEM/UP/1A Edition 3 (Draft for Comment)
APPENDIX 7 : PURGING HEAVIER-THAN-AIR GASES – RISK
ASSESSMENT
A7.1
FLAMMABILITY RANGE
Differing fuel gases have very different flammable ranges and, when working
with these various gases, it is essential that the range is understood as well as
having gas detection equipment suitable for the gas being monitored.
A7.2
DENSITY (SPECIFIC GRAVITY)
The densities of gases vary dependant on their temperatures, so it is normal to
refer to density relative to air. Air has a density of 1. Gases with lower density
are lighter-than-air and gases with a higher density are heavier-than-air.
A7.3
PROPERTIES OF LPG
The most common of the heavier than air gases in use are known as Liquefied
Petroleum Gas, or LPG, (3rd family gases). BS 4250 is the specification for
commercial butane and propane, but gases outside this specification are often
used for special purposes.
They are stored in the liquefied state under pressure. The actual pressure in the
storage container, known as the vapour pressure, is dependent upon the
specification of the actual LPG and the temperature of the stored liquid.
These procedures apply only to the pipework downstream of the first stage
pressure regulator in a vapour system. They do not apply to the storage tank,
the high pressure pipework feeding the first stage regulator, or to any part of a
system containing LPG in the liquid phase.
LPG vapour is, normally, used for gas supplies to gas fired equipment. This
vapour may be generated by natural vaporisation of the liquefied LPG, or for
large industrial offtakes by the use of an in line vaporiser where the latent heat
required is provided from an external source.
Some LPG may contain small quantities of heavy hydrocarbons that do not
readily vaporise, often described as "heavy ends". Where they are present,
these heavy ends will concentrate in the bottom of storage vessels used for
natural vaporisation systems, or in the base of external vaporisers. In abnormal
situations, or where the plant operators fail to drain the system regularly, they
may be carried over into the gas supply pipework.
Where heavy ends are found in downstream pipework specialist advice is
required to ensure that they are removed and disposed of in a safe manner. A
permit to carry out such work is required to be issued by an authorised
competent person.
Note:
A7.4
Heavy ends are, normally, only associated with LPG produced from refinery operations and
are not present in LPG produced from natural gas liquids.
ASSESSMENT OUTCOME
If the assessment indicates that safety would be compromised, the heavierthan-air gas shall be purged indirectly seeking specialist advice if necessary.
57
IGEM, IGEM, IGEM House, High Street, Kegworth, Derbyshire, DE74 2DA. Website: www.igem.org.uk
IGEM/UP/1A Edition 3 (Draft for Comment)
APPENDIX 8 : TYPICAL PURGE EQUIPMENT SETUP
FIGURE 9 – TYPICAL EQUIPMENT FOR AIR TO GAS PURGE
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IGEM, IGEM, IGEM House, High Street, Kegworth, Derbyshire, DE74 2DA. Website: www.igem.org.uk
IGEM/UP/1A Edition 3 (Draft for Comment)
FIGURE 10 - TYPICAL EQUIPMENT FOR GAS TO AIR PURGE (COMPRESSED
AIR/NITROGEN)
59
IGEM, IGEM, IGEM House, High Street, Kegworth, Derbyshire, DE74 2DA. Website: www.igem.org.uk
IGEM/UP/1A Edition 3 (Draft for Comment)
FIGURE 11 - TYPICAL EQUIPMENT FOR GAS TO AIR PURGE (FAN)
60
IGEM, IGEM, IGEM House, High Street, Kegworth, Derbyshire, DE74 2DA. Website: www.igem.org.uk