STRENGTH TESTING, TIGHTNESS TESTING AND … edition 3 - draft for...Attached is the Draft for Comment of IGEM/UP/1A – “Strength testing, tightness testing and direct purging of

INSTITUTION OF GAS ENGINEERS AND MANAGERS IGEM/TSP/13/282

Founded 1863 IGEM/UP/1A Edition 3 Royal Charter 1929 Communication XXXX 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: [email protected]

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

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 HouseHigh Street

KegworthDerbyshire, DE74 2DA

Tel: 0844 375 4436Fax: 01509 678198

Email: [email protected]

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

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)

IGEM, IGEM House, High Street, Kegworth, Derbyshire DE74 2DA. Website: www.igem.org.uk

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

5.1 Determination of STP 10

5.2 Decision whether to strength test 11 • 5.2.1 New installations and extensions 11 • 5.2.2 Existing installations 11

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

6 Tightness testing 14

6.1 General 15 6.1.1 New installations and extensions 15 6.1.2 Existing installations 15

6.2 Installation volume (IV) 15 6.2.1 General 15 6.2.2 Calculations 16

6.3 Tightness test pressure (TTP) 17

6.4 Selection of pressure gauges 17

6.5 Test criteria 18 6.5.1 New installations and extensions 18 6.5.2 Existing installations 18

6.6 Tightness test duration (TTD) 20 5.6.1 New installations and extensions 20 5.6.2 Existing installations 21

6.7 Procedures 21 6.7.1 By-passing components 21 6.7.2 Ambient conditions 22 6.7.3 Testing new installations and extensions 22 6.7.4 Testing existing installations 23

6.8 Appliance connector 25 7 Direct purging 28

7.1 General 28

7.2 Planning and supervision 28

7.3 Site precautions 29 7.3.1 Warning notices and label 29 7.3.2 Electrical and fire 30



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 Purging procedures when venting to outside 34 7.11.1 Direct purging from air to gas i.e. commissioning 34 7.11.2 Direct purging from gas to air i.e. de-commissioning 35

7.12 Dealing with meters within pipework sections 37 7.12.1 Replacement meter with associated pipework

maintained at positive pressure 37 7.12.2 Replacement meter with associated pipework

not maintained at a positive pressure 38 7.12.3 Purging a new meter 39

APPENDIX 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

6 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 TABLES 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



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


1 IGEM, IGEM, IGEM House, High Street, Kegworth, Derbyshire, DE74 2DA. Website: www.igem.org.uk

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.



Start

LPG installationon a boat, small craft, (up to

24 m in length) or other vessels?

YesPD 5482-3 or

BS EN ISO 10239

Is supply MOP ≤ 2 bar (for LPG/air and NG) AND

Ø ≤ 35 mm ANDMeter badged capacity ≤ 16 m3 h-1 AND

volume ≤ 0.035 m3 ANDOP ≤ 21 mbar (for LPG/Air and NG) OR

OP ≤ 37 mbar (for LPG)?

No

Yes IGEM/UP/1B Edition 3

NG or LPG?

No

Yes

Meter installation withsupply MOP ≤ 7 bar ANDwith volume ≤ 1 m3 ANDwith no PE included AND

isolated at the outlet

Yes IGEM/UP/1C

No

Is MOP ≤ 60 mbar ANDØ ≤ 150 mm AND

volume ≤ 1 m3 (for LPG/Air and NG) ORvolume ≤ 0.5 m3 (for LPG)?

Yes IGE/UP/1A Edition 2

IGE/UP/1 Edition 2

No

No

less than or equal to MOP Maximum Operating Pressure mbar millibar

nominal diameter NG Natural Gas mm millimetre V volume OP Operating pressure m3 cubic metre LPG Liquefied petroleum gas

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



STP = Strength test pressure MIP = Maximum incidental pressure (e.g., as declared by the GT/MAM/Supplier) OP = Operating pressure MOP = Maximum operating pressure SP = Set point of the regulator.

Note: 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:

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.

1.6 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.



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.



SECTION 2 : SCOPE 2.1 This Standard covers strength and tightness testing, and purging of installations

containing LPG/air, NG or LPG. Note: For other gases, IGEM/UP/1 applies.

2.2 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

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

routine testing of existing installations

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.



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’.



(a) Typical installation. MOPu 75 mbar.

Installation MOP 60 mbar

Strength test if New or Extension.Tightness test and Purge to IGEM/UP/1A.

MECV R AECV

(If fitted)AIV

AMIVF S

(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 emergency control valve Network S safety device (see BS 6400) meter installation F filter installation pipework R regulator < less than MIV meter inlet valve less than or equal to M meter A appliance AECV additional emergency control valve AIV appliance isolation valve IV isolation valve MOPu supply MOP.

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



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

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.

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.



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: Fluid (water) gauges do not require calibration but do need to be kept well maintained.

4.1.2 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.

4.1.3 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: Electronic gauges may be prone to drifting due to changes in ambient temperature.

4.1.4 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.



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.



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: 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.

5.1 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.



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: Either this value will have been formally recorded previously or the relevant GT will need to be consulted.

GAS MOP STP

STABILIZE STD MAXIMUM PERMITTED

DROP

LPG/Air

or NG

≤ 21 mbar 82.5 mbar 5 mins* 5 mins 20% STP

> 21 mbar

≤ 60 mbar

(greater of) 120 mbar and 2.5 MOP

5 mins* 5 mins 20% STP

LPG ≤ 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



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.



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 ALGORITHM FOR STRENGTH TESTING



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.



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: 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. 6.2.1.2 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 pipe (p) + IV fittings (f) and the total IV (IVt) (m3) shall be calculated as follows: (a) IV of meters (IVm)

Use Table 2 or for other meters, consult the meter manufacturer.

DESIGNATION OF METER

IVm (m3)

G4/U6 G10/U16 G16/U25 G25/U40 G40/U65 G65/U100 G100/U160

0.008 0.025 0.052 0.105 0.129 0.270 0.304

RD or turbine Equivalent length of pipe based on connection size (see Table 3) E6 0.0024

Note: 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



(b) IV of pipe (IVp)

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)

VOLUME OF 1 m LENGTH OF PIPE

(m3)

MATERIAL AND NOMINAL SIZE

OF PIPE (mm)

VOLUME OF 1 m LENGTH OF PIPE

(m3)

Steel/stainless steel/CSST

PE

15 ½

20 ¾

25 1

32 1¼

40 1½

50 2

65 2½

80 3

100 4

125 5

150 6

.00024

.00046

.00064

.0011

.0015

.0024

.0038

.0054

.009

.014

.02

20

25

32

55

63

75

90

125

180

.00019

.00033

.00053

.0016

.0021

.0029

.005

.01

.02

Copper

15

22

28

35

42

54

67

76

108

.00014

.00032

.00054

.00084

.0012

.0021

.0033

.0043

.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



Example: A simple system. Meter is U65, volume of valves and fittings is unknown.

INSTALLATION VOLUME Meter (IVm) U65 Diaphragm Meter IVm = 0.100 m3

Pipework (IVp) 12 m of 80 mm (Steel) 12 x 0.0054 = 0.0648 m3

10 m of 35 mm (Copper) 10 x 0.00084 = 0.0084 m3

IVp = 0.0732 m3

Fittings (IVf) 0.1 x IVp IVf = 0.00732 m3

Total volume (IVt) IVm+ IVp + IVf IVt = 0.181 m3

6.3 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.



IV (m3) TIGHTNESS TEST DURATION (TTD) (mins) LPG/Air (SMG) NG LPG

Up to 0.12 Up to 0.06 Up to 0.01 2 >0.12 0.18 >0.06 0.09 >0.01 0.02 3 >0.18 0.24 >0.09 0.12 >0.02 0.03 4 >0.24 0.30 >0.12 0.15 >0.03 0.04 5 >0.30 0.36 >0.15 0.18 >0.04 0.05 6 >0.36 0.42 >0.18 0.21 >0.05 0.06 7 >0.42 0.48 >0.21 0.24 >0.06 0.07 8 >0.48 0.54 >0.24 0.27 >0.07 0.08 9 >0.54 0.60 >0.27 0.3 >0.08 0.09 10 >0.60 0.66 >0.3 0.33 >0.09 0.1 11 >0.66 0.72 >0.33 0.36 >0.1 0.11 12 >0.72 0.78 >0.36 0.39 - 13 >0.78 0.84 >0.39 0.42 >0.11 0.12 14 >0.84 0.90 >0.42 0.45 >0.12 0.13 15 >0.90 1 >0.45 0.48 >0.13 0.14 16 >0.48 0.51 >0.14 0.15 17 >0.51 0.54 >0.15 0.16 18 >0.54 0.57 >0.16 0.17 19 >0.57 0.6 >0.17 0.18 20 >0.6 0.63 >0.18 0.19 21 >0.63 0.66 - 22 >0.66 0.69 >0.19 0.20 23 >0.69 0.72 >0.20 0.21 24 >0.72 0.75 >0.21 0.22 25 >0.75 0.78 >0.22 0.23 26 >0.78 0.81 >0.23 0.24 27 >0.81 0.84 >0.24 0.25 28 >0.84 0.87 >0.25 0.26 29 >0.87 0.9 >0.26 0.27 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) TIGHTNESS TEST DURATION (TTD) (mins)

LPG/Air (SMG) LPG/Air (SNG) or

NG LPG

Up to 0.60 Up to 0.30 Up to 0.09 2 >0.60 0.90 >0.30 0.45 >0.09 0.13 3 >0.90 1 >0.45 0.60 >0.13 0.18 4 >0.60 0.75 >0.18 0.22 5 >0.75 0.90 >0.22 0.27 6 >0.90 1 >0.27 0.31 7 >0.31 0.36 8 >0.36 0.40 9 >0.40 0.45 10 >0.45 0.49 11 >0.49 0.50 12

TABLE 5 - TIGHTNESS TEST DURATION (TTD) FOR NEW INSTALLATIONS

AND EXTENSIONS USING AN ELECTRONIC GAUGE READING TO 2 DECIMAL PLACES



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 LPG Installation

Test using air

Test using NG

Test using air

Test using LPG

0.15 2 2 5 3 >0.15 ≤0.3 3 2 10 5 >0.3 ≤0.45 5 3 14 7 >0.45 ≤0.5

6 4 19 9

>0.5 ≤0.6

N/A N/A >0.6 ≤0.75 8 5 >0.75 ≤0.9 9 6 >0.9 ≤1 10 6

Note: 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 DURATION (TTD) FOR EXISTING

INSTALLATIONS 6.5 PROCEDURES 6.5.1 By-passing components

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.



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.



TYPE OF GAUGE GRM (mbar)

Fluid (increments of 0.5 mbar) 0.5 Electronic (1 decimal place) 0.5 Electronic (2 decimal places) 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: IGEM publishes suitable triplicate certificates in pads.

(m) 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.



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.



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) LET-BY TEST PERIOD (mins)

≤0.5 2 >0.5 ≤0.8 3 >0.8 ≤1.0 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.



Note: 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.

(e) 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.



IV (m3 ) TTD (Test Using Fuel Gas)

TTD (Test Using

Air)

VOLUME OF SMALLEST OCCUPIED SPACE (RV) (m3)

10 15 20 25 30 35 40 45 50 55 ≥60

0.15 2 2 0.7 1.0 1.4 1.7 2.1 2.4 2.8 3.1 3.5 3.9 4.2

>0.15 0.2

2 3

0.7 1.1 1.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3 4.7

>0.2 0.25 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 0.35

3 5

0.7 1.1 1.5 1.8 2.2 2.6 3.0 3.4 3.7 4.1 4.5

>0.35 0.4 0.6 0.9 1.3 1.6 1.9 2.3 2.6 2.9 3.3 3.6 3.9

>0.4 0.45 0.5 0.8 1.1 1.4 1.7 2.0 2.3 2.6 2.9 3.2 3.5

>0.45 0.5

4 6

0.6 0.9 1.2 1.5 1.9 2.2 2.5 2.8 3.1 3.5 3.8

>0.5 0.55 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 0.65

5 8

0.6 0.9 1.3 1.6 1.9 2.2 2.6 2.9 3.2 3.6 3.9

>0.65 0.7 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 3.3 3.6

>0.7 0.75 0.5 0.8 1.1 1.4 1.7 1.9 2.2 2.5 2.8 3.1 3.4

>0.75 0.8

6 9

0.5 0.8 1.1 1.4 1.7 2.0 2.3 2.6 2.9 3.2 3.5

>0.8 0.85 0.5 0.8 1.1 1.4 1.6 1.9 2.2 2.5 2.8 3.0 3.3

>0.85 0.9 0.5 0.7 1.0 1.3 1.5 1.8 2.1 2.3 2.6 2.9 3.1

>0.9 0.95 6 10

0.5 0.8 1.1 1.3 1.6 1.9 2.2 2.5 2.7 3.0 3.3

>0.95 1.0 0.5 0.7 1.0 1.3 1.5 1.8 2.1 2.3 2.6 2.9 3.1

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



IV (m3 ) TTD (Test Using Fuel Gas)

TTD (Test Using

Air)

VOLUME OF SMALLEST OCCUPIED SPACE (RV) (m3)

10 15 20 25 30 35 40 45 50 55 ≥60

0.15 3 5 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.9 2.1 2.3 2.5

>0.15 0.2

5 10

0.6 0.9 1.2 1.5 1.9 2.2 2.5 2.8 3.1 3.4 3.8

>0.2 0.25 0.5 0.7 1.0 1.2 1.5 1.7 2.0 2.2 2.5 2.7 3.0

>0.25 0.3 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.9 2.1 2.3 2.5

>0.3 0.35

7 14

0.5 0.7 1.0 1.2 1.5 1.7 2.0 2.2 2.5 2.7 3.0

>0.35 0.4 0.4 0.6 0.8 1.1 1.3 1.5 1.7 2.0 2.2 2.4 2.6

>0.4 0.45 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3

>0.45 0.5 9 19 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.



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: IGEM publishes suitable triplicate certification in pads.

(n) 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 = (3 X 3 X 2.55) = 22.95 m3

TTD = 4 minutes (Table 8) Maximum allowable pressure drop = 1.4 mbar (Table 5).



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.



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: 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.

6.6.7 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



if the appliance connector is known to contain fuel gas only, commission / re-commission 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.



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



Note: This algorithm does not show all necessary steps and the full procedures in Section 6 apply.

FIGURE 6 - FLOW CHART/DECISION ALGORITHM FOR TIGHTNESS TESTING OF EXISTING INSTALLATIONS



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

check for the existence of a “ring main” system. If a ring main exists, divide/sectionalise the “ring main” to enable complete purging

survey the pipework section to establish that it is in a satisfactory condition. Any defect shall be corrected before any purging is undertaken, unless de-commissioning



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.



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

gas tight

secured firmly to the purge point Note: Unsecured push-on connections are not acceptable.

earthed suitably to avoid sparking, if necessary, for example for externally armoured hose.

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.



7.4.9 When flaring, the flame shall be at a location that minimises heat radiation

effects that could lead to danger to persons or property. 7.4.10 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: This can be achieved, for example by using an oxygen detector, or by confirmation of the

contents of the cylinder from the supplier, etc. 7.7 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)

be operated in accordance with the manufacturer’s instructions and by a trained competent person capable of interpreting the results obtained

have its batteries tested prior to use

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.



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: 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). 7.9.3 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)

20 25 32 40 50 80 100 125 150

Minimum purge gas flow rate (Qp) (m3 h-1)

0.7 1.0 1.7 2.5 4.5 11.0 20.0 30.0 38.0

Purge point nominal bore

20 20 20 20 25 25 25 40 40

Purge hose/vent stack nominal bore

20 20 20 20 40 40 40 50 50

Flame arrestor nominal bore

20 20 20 20 50 50 50 50 50

Note: 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



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 =0.405 m3

IVf =10% x IVp =0.0405 m3 PV of pipework =1.5 x (0.405 + 0.0405) =0.6683 m3

Meter cyclic volume =0.01 m3 PV of meter =5 x cyclic volume (= 5 x 0.01) =0.05 m3 Purge hose volume =10 x 0.00064 =0.0064 m3 PV of purge hose =1.5 x 0.0064 =0.0096 m3

Total purge volume is, thus ( 0.6683 + 0.05 + 0.0096) =0.73m3

(rounding up) Minimum purge flow rate = 11 m3h-1 (Table 9) Maximum purge time = 0.73 x 3600 = 238.9 seconds 11 =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: Table 12 is intended to ensure safe conditions, but not necessarily efficient combustion performance.

FUEL GAS FLAMMABILITY LIMITS SAFE PURGE END POINTS LOWER LIMIT % GAS IN AIR

UPPER LIMIT % GAS IN AIR

DIRECT PURGE AIR TO GAS

DIRECT PURGE GAS TO AIR

LPG/Air 2.0 10.0 90% fuel gas < 10% LFL (0.2% gas in air)

NG 4.5 15.5 90% fuel gas < 40% LFL (1.8% gas in air)

Propane 2.1 10.0 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



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.




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: 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 low-pressure 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.

(d) 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).



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.




AIR TO GAS Commissioning

Start

Ensure that a satisfactory tightness test has been

carried out.

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)

Vent stacks and hoses correctly located. Warning

notices, barriers, fire extinguishers available and checked. Test meters and gas detectors checked.

Open purge points and vent valves.

Immediately admit fuel gas at correct flow rate.

Monitor gas pressure.

Monitor gas flow rate.

Do not allow to exceed OP.

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.

Test all disturbed joints and joints in ducts for leaks.

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 7 - FLOWCHART FOR DIRECT PURGING OF AIR TO GAS



GAS TO AIR De-commissioning

Start

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)

Vent stacks and hoses correctly located. Warning

notices, barriers, fire extinguishers available and checked. Test meters and gas detectors checked.

Open purge points and vent valves.

Immediately admit air at correct flow rate.

Monitor gas pressure.

Monitor gas flow rate.

Do not allow to exceed OP.

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.

Isolate gas supply.Carry out let-by test.

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



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 Approved Code of Practice ACS Accredited Certification Scheme ECV Emergency control valve GRM Gauge readable movement GS(I&U)R Gas Safety (Installation and Use) Regulations GT Gas transporter HSE Health and Safety Executive IGEM Institution of Gas Engineers and Managers IV Installation volume LDF Leak detection fluid LFL Lower flammable limit LPG Liquefied petroleum gas LPGA Liquefied Petroleum Gas Association MAM Meter asset manager MIP Maximum incidental pressure MIV Meter inlet valve MOP Maximum operating pressure MOV Meter outlet valve NDT Non-destructive testing NG Natural Gas OP Operating pressure PE Polyethylene PT Purge time PV Purge volume RD Rotary displacement RV Room volume SDR Standard dimension ratio SP Set point SSOV Safety shut-off valve STD Strength test duration STP Strength test pressure TTD Tightness test duration TTP Tightness test pressure UK United Kingdom UKAS United Kingdom Accreditation Service.

SYMBOLS

diameter less than greater than equal to or greater than less than or equal to Qp minimum purge flow rate N2 Nitrogen V volume.



SUBSCRIPTS/SUFFICES/UNITS

f fittings, etc. p pipe m meter t total d nominal bore L flange to flange dimension m3 cubic metre m3 h-1 cubic metre per hour ft3 cubic feet ft3 h-1 cubic feet per hour m metre mm millimetre in inch mins minute mbar millibar.



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

Gas Act 1995

Health and Safety at Work etc. Act 1974 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.

Control of Substances Hazardous to Health Regulations 1995 as amended in 1997 and 1998

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

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.

Workplace (Health, Safety and Welfare) Regulations 1992. A2.2 ACOPS AND GUIDANCE NOTES

HSG48 Human factors in industrial safety. A2.3 BRITISH STANDARDS (ABBREVIATED TITLES)

BS 6891 Low pressure pipework in domestic premises

BS EN 12874 Flame arresters

BS EN 60079 Electrical apparatus for explosive gas atmospheres. A2.4 IGEM PROCEDURES AND RECOMMENDATIONS

IGE/UP/1 Strength testing, tightness testing and direct purging of Edition 2 industrial and commercial gas installations

IGEM/UP/1B Tightness testing and direct purging of small Liquefied Edition 3 Petroleum Gas/Air, Natural Gas and Liquefied Petroleum Gas installations

IGEM/UP/2 Installation pipework on industrial and commercial Edition 2 premises

IGE/SR/22 Purging operations for fuel gases in transmission, distribution and storage

IGE/SR/23 Venting of Natural Gas

IGE/SR/24 Risk assessment techniques

IGEM/TD/13 Pressure regulating installations for Natural Gas, Liquefied Edition 2 Petroleum Gas and Liquefied Petroleum Gas/Air

IGEM/G/1 Definitions for the end of a network, meter installation, and installation pipework.



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 inadequately-sized 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: Take additional care at purge gas vent point due as a flammable mixture may occur at a

different stage in the operation. A3.3 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.



FUEL GAS FLAMMABILITY LIMITS SAFE PURGE END POINTS LOWER LIMIT % GAS IN AIR

UPPER LIMIT % GAS IN AIR

INDIRECT PURGE FROM

FUEL GAS TO N2

INDIRECT PURGE FROM N2 TO FUEL

GAS LPG/Air 2.0 10.0 3.5% gas in N2 90% fuel gas in N2

NG 4.5 15.5 7.5% gas in N2 90% fuel gas in N2

Propane 2.1 10 3.5% gas in N2 90% fuel gas in N2

TABLE 13 - FLAMMABILITY LIMITS AND SAFE PURGE ENDS POINTS FOR INDIRECT PURGE



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.

IV (m3) TIGHTNESS TEST DURATION (TTD) (mins) LPG/Air (SMG) NG LPG

Up to 0.12 Up to 0.06 Up to 0.01 2 >0.12 0.18 >0.06 0.09 >0.01 0.02 2 >0.18 0.24 >0.09 0.12 >0.02 0.03 2 >0.24 0.30 >0.12 0.15 >0.03 0.04 3 >0.30 0.36 >0.15 0.18 >0.04 0.05 3 >0.36 0.42 >0.18 0.21 >0.05 0.06 4 >0.42 0.48 >0.21 0.24 >0.06 0.07 4 >0.48 0.54 >0.24 0.27 >0.07 0.08 5 >0.54 0.60 >0.27 0.3 >0.08 0.09 5 >0.60 0.66 >0.3 0.33 >0.09 0.1 6 >0.66 0.72 >0.33 0.36 >0.1 0.11 6 >0.72 0.78 >0.36 0.39 - 7 >0.78 0.84 >0.39 0.42 >0.11 0.12 7 >0.84 0.90 >0.42 0.45 >0.12 0.13 8 >0.90 1 >0.45 0.48 >0.13 0.14 8 >0.48 0.51 >0.14 0.15 9 >0.51 0.54 >0.15 0.16 9 >0.54 0.57 >0.16 0.17 10 >0.57 0.6 >0.17 0.18 10 >0.6 0.63 >0.18 0.19 11 >0.63 0.66 - 11 >0.66 0.69 >0.19 0.20 12 >0.69 0.72 >0.20 0.21 12 >0.72 0.75 >0.21 0.22 13 >0.75 0.78 >0.22 0.23 13 >0.78 0.81 >0.23 0.24 14 >0.81 0.84 >0.24 0.25 14 >0.84 0.87 >0.25 0.26 15 >0.87 0.9 >0.26 0.27 15 >0.9 0.93 >0.27 0.28 16 >0.93 0.96 >0.28 0.29 16 >0.96 1.0 >0.29 0.3 17

TABLE 14 - TIGHTNESS TEST DURATION (TTD) FOR NEW INSTALLATIONS AND EXTENSIONS USING NO PERCEPTIBLE MOVEMENT



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:

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

A5.2 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





passed

A5.3 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



passed



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:







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.



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:












(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.


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.





(e) Ensure every branch of pipework is purged following the aforementioned

procedure.

(f) Establish a stable flame picture at each appliance.






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:












(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.



(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.






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: Heavy ends are, normally, only associated with LPG produced from refinery operations and

are not present in LPG produced from natural gas liquids.

A7.4 ASSESSMENT OUTCOME

If the assessment indicates that safety would be compromised, the heavier-than-air gas shall be purged indirectly seeking specialist advice if necessary.



APPENDIX 8 : TYPICAL PURGE EQUIPMENT SETUP

FIGURE 9 – TYPICAL EQUIPMENT FOR AIR TO GAS PURGE



FIGURE 10 - TYPICAL EQUIPMENT FOR GAS TO AIR PURGE (COMPRESSED

AIR/NITROGEN)



FIGURE 11 - TYPICAL EQUIPMENT FOR GAS TO AIR PURGE (FAN)

Documents

STRENGTH TESTING, TIGHTNESS TESTING AND … edition 3 - draft for...Attached is the Draft for Comment of IGEM/UP/1A – “Strength testing, tightness testing and direct purging of