1.1 This Standard supersedes IGEM/H/3, Communication 1861 which is obsolete.

1.2 This Standard supersedes IGEM/H/3, Communication 1861 which is obsolete. This Hydrogen Enabling Standard was commissioned by the Hydrogen Skills and Standards for Hydrogen (HSS4H) programme to provide evidence to support the UK Government’s 2025 consultation on the role of hydrogen in heating. The Standard has been prepared to support the initial coordinated community-based village trial for 100% Hydrogen (see Sub-Section 2.4) and to support the training and assessment program for Gas Safe Registered engineers who are to be engaged in the trial.

Note: A decision was made by the UK Government in 2023 not to progress with the initial village trials planned for Whitby and Redcar. The document will still be relevant to any future trial that takes place.

1.3 The Standard sets down the specific additional requirements and procedures to enable engineers to carry out work on new non-domestic Hydrogen installations and existing Natural Gas (NG) non-domestic installations repurposed for Hydrogen during the initial community-based village trial.

1.4 The aim of the document is to identify the differences in practices and procedures that will be required for non-domestic Hydrogen installations. However, this cannot be an exhaustive list.

1.5 This IGEM Standard provides the key technical & safety engineering requirements, in conjunction with applicable UK Regulations, to support a training and assessment programme for engineers involved in the Hydrogen community trials. The Standard can also be used to support employers to develop their own site-specific work practices and procedures for their employees to use and follow.

1.6 For industrial and commercial (i.e., non-domestic) installations, the Dangerous Substances and Explosive Atmosphere Regulations (DSEAR) require employers to control the risks to safety from fire, explosions, and substances corrosive to metals. For such installations, it is essential that they are maintained and inspected as determined by the risk assessment. Gas pipework design and installation for industrial and commercial installation undertaken in accordance with this Standard has to account for any requirements imposed by DSEAR.

Note: See Sub-Section 3.8.

1.7 Under normal circumstances, correctly jointed pipework will not leak throughout its lifetime. However, the local environment, mechanical damage and interference could cause leakage to occur. Therefore, it is necessary to ensure that if leakage does occur, a flammable atmosphere will not result. Advice is given in this Standard on the location of pipework joints for Hydrogen installations.

1.8 Standards, and research being undertaken by the HSS4H and other research-based programs, are to support the UK Government’s policy decision and the village trial. The practices and procedures recommended in this Standard reflect the current maturity of knowledge and experience of Hydrogen operation and will be reviewed over time as the operational evidence base becomes more established.

1.9 Some procedures and equipment required by this Standard may only be applicable during the initial trials. If the UK Government’s policy decision supports conversion, further research and development, in conjunction with experience gained from trials, may result in different approaches being adopted in the future, which will be incorporated into future guidance.

1.10 Many of the methods and equipment required for these activities are still being developed and finalised, and updates to this document will be required as information becomes available.

1.11 If the UK Government’s policy decision supports converting the Natural Gas system to Hydrogen, this document will be superseded by normative Standards and procedures once they are fully developed.

1.12 This Standard makes use of the terms “must”, “shall” and “should”, when prescribing particular procedures:

• the term “must” identifies a requirement by law in Great Britain (GB) at the time of publication
• the term “shall” prescribes a procedure which, it is intended, will be complied with in full and without deviation
• the term “should” prescribes a procedure 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 Executive (HSE) Approved Code of Practice (ACoP) or guidance, and reference needs to be made to such statutory Legislation or official guidance for information on legal obligations.

1.13 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. People who initiated actions that caused or contributed to accidents might have acted in a more appropriate manner to prevent them.
To assist in the control of risk and proper management of these human factors, due regard is to be taken of HSG48 and HSG65.

1.14 The primary responsibility for compliance with legal duties relating to health and safety at work 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.

Note: The responsible engineer is a suitably qualified, competent, and experienced engineer appointed to be responsible for the execution and for approval of activities designated by their employer.
Employers are required to:

• have done everything to ensure, so far as is reasonably practicable, that there are no better protective measures that can be taken other than relying on the exercise of professional judgement by "responsible engineers"
• have done everything to ensure, so far as 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
• Employers shall 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 are to refer the matter for higher review

1.15 Notwithstanding Sub-Section 1.12, where new and better techniques are developed and proved, they are to be adopted without waiting for the modification of this Standard. Amendments to this Standard will be issued when necessary and their publication will be announced in the Journal of IGEM and other publications as appropriate.

1.16 The document identifies (via notes) where confirmation is outstanding or where an explanation of a recommendation given in the draft is required, for example:
(Note: Exact details of size and flow limits to be determined.)

1.17 Evidence to support these recommendations is referenced throughout the document and is based on work published at the time of writing.

1.18 This Standard was published in December 2024.

2.1 This Standard covers gas utilisation activities associated with the design, installation, commissioning, and maintenance of Hydrogen gas installations, downstream of the Emergency Control Valve (ECV), in non-domestic premises, forming part of a UK Government approved coordinated community-based trial.
 

Note 1: The term ‘non-domestic’ encompasses commercial and industrial.
Note 2: This Standard assumes a supply of Hydrogen gas is available upstream of the ECV and that the new conversion of the local low-pressure supply network to Hydrogen has been completed.

2.2 This Standard applies to both new installations for Hydrogen and repurposed Natural Gas installations for Hydrogen.

Note 1: The Standard uses the terminology - ‘new installations’ and ‘repurposed installations’ to reflect this.
Note 2: Where all or parts of an existing Natural Gas installation is to be repurposed for Hydrogen, it will have been covered by a risk assessment (which may be generic if suitable for the specific circumstances and adapted if necessary) to ensure the components are suitable for use or otherwise replaced.
Note 3: The range of Hydrogen plant and appliances available for the initial trials may be limited. Therefore, this Standard focuses on the installation of those appliances that will be used in the trials and will be available for both training and assessment of competence.
Note 4: Some non-domestic premises may include domestic sized meters and appliances.
Note 5: The principles of this Standard can be applied to the repurposing of other fuel gas installations, e.g. LPG, with due regard to the differences in the gas.

2.3 Trials may also include domestic premises. These installations are covered by a separate Standard, IGEM/H/2 Hydrogen Enabling Standard – Domestic.
Larger domestic premises which are outside the scope of IGEM/H/2 will be covered by this Standard.
 

Note 1: This is due to large domestic premises having a primary meter size greater than 20 m3/h requiring individual assessment of excess flow mitigation provision.
Note 2: DSEAR would only apply in these premises when work was being carried out.

2.4 The Hydrogen gas supplied to trial installations is assumed to be nominally 100% Hydrogen, though it may contain small quantities of other components and the odorant. Blends of Hydrogen and Natural Gas are not within the scope of this document.

Note 1: The term 100% is used to differentiate between Hydrogen and Hydrogen blended with Natural Gas.
Note 2: IGEM/H/1 Reference Standard and PAS 4444 details the gas quality information.

2.5 The Standard applies to new and repurposed Hydrogen installation pipework and meters having the following:

• connection to a Hydrogen low pressure (LP) supply network and,

Note: Although Medium Pressure (MP) supplies above 75 mbar are not included in the trials, an outline of the additional considerations for MP supplied installations is given in Appendix 9. The principles of this Standard could be applied to downstream installation pipework operating up to 100 mbar.

• maximum Operating Pressure at the inlet to the meter installation (MOPu) not exceeding 75 mbar and Maximum Incidental Pressure (MIPu) not exceeding 200 mbar and,
• nominal contracted metering pressure (Pm) not exceeding 30 mbar (normally 21 mbar) and,
• primary meters having a maximum badged capacity through the primary meter of not exceeding 65 m3/h (see note 2 below) and,
• single stream pressure regulator and,
• the following primary meter types:
• ultrasonic
• hermal mass flow
• rotary positive displacement.
• large domestic premises that exceed the scope of IGEM/H/2.

Note 1: The supply Network Operator may choose to provide a higher than normal minimum pressure at the outlet of the ECV to assist in the repurposing of the downstream pipework, subject to the required approvals.
Note 2: The principles of this Standard can be applied to larger sized (up to 1076 m3/h) low-pressure non-domestic meter installations (subject to the availability of meters and acceptable regulating equipment to satisfy the requirements of the trial).
Note 3: It is unlikely that suitable turbine meters will be available for the trial.

2.6 All pressures quoted are gauge pressure unless otherwise stated.

2.7 The following types of premises and plant are excluded:

• gas engines
• gas boosters
• gas compressors
• gas turbines
• educational establishments other than central boiler plant
• multi-occupancy buildings (as defined by IGEM/G/5)
• energy centres
• garages and body shops facilities
• caravan parks and boats, yachts, and other vessels
• bottled gas supplies.

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”.