Enforcement considerations for inspectors investigating gas incidents arising from the failure of steel service pipes
Formerly SPC ENF 186
This guidance sets out the key factors that inspectors should take into account when investigating gas incidents arising from the failure of steel service pipes and steel service 'tails' attached to polyethylene pipes. In particular, it describes the approaches typically adopted by the gas distribution network operators (GDNs) to manage the risk of steel service pipe failure. Steel risers in blocks of flats and steel gas mains are outside the scope of this guidance
The failure of steel service pipes may lead to gas entering occupied buildings and the risk of fire or explosion should the gas ignite. The GDNs estimate that there are approximately 8 to 10 million steel service pipes taking gas from mains to consumers' premises. They fail typically through external corrosion which can be accelerated by acidic soil or the presence of decaying organic matter. Low pressure steel service pipes are not usually subject to cathodic protection (although those operating at higher pressures may be). Protective measures such as wrapping or coatings are sometimes used to prevent external corrosion but, due to damage or deterioration, they may not be fully effective.
The management of risk from steel service pipes is currently a significant issue for the GDNs.
Inspectors investigating incidents caused by gas escapes from steel service pipes must consider whether it was reasonable to expect the dutyholder to have identified and replaced the pipe prior to its failure.
Inspectors should consider taking enforcement action, in line with the Enforcement Management Model (EMM), if their investigation finds that the GDN has failed to:
- Undertake steel service pipe replacement where iron mains replacement has previously taken place upstream of the failed service pipe (mains replacement provides an ideal opportunity for the GDN to replace steel services with minimal disruption to customers and is accepted practice across GDNs),
- Replace the failed steel service pipe when it had been the subject of previous leakage report(s),
- Carry out the replacement and/or the condition assessment of the failed steel service pipe where there is evidence (obtained systematically by the GDN) of a heightened local risk of failure (ie a 'hot spot').
The GDNs may adopt other, equally effective, means of prioritising steel service pipe replacement and/or other suitable means of managing risk across their steel service pipe population. The decision to take enforcement action following an incident should therefore be considered carefully on a case-by-case basis.
Regulation 13 of the Pipelines Safety Regulations 1996 (PSR) - this Regulation requires the operator of a pipeline to ensure that it is maintained in an efficient state, in efficient working order and in good repair. This duty is absolute and, in the case of steel service pipes, maintenance generally means removal and replacement.
HSE accepts that it is not practicable for the GDNs to proactively establish and monitor the condition of all of the steel service pipes within their networks. Nor is it feasible for the entire population of these pipes to be replaced immediately. However, it may be practicable for operators of smaller networks to proactively assess the condition of their steel service pipes.
Regulation 13A of PSR - this offers the GDNs a statutory defence to Regulation 13 in the event of the failure of an iron pipe included within an approved mains replacement programme. However, Regulation 13A does not apply to steel service pipes and a GDN will be in breach of Regulation 13 in the event that these fail.
In 2011, an independent review into the effectiveness of the 30-year Iron Mains Replacement Programme (IMRP) concluded that the risks associated with the failure of steel service pipes does not justify their inclusion within the IMRP. As such steel service pipes continue to be excluded from the IMRP.
For further information please contact the Gas and Pipelines National Inspection and Operational Support Team (ED 5.4).