Gas supply - Monitoring and reporting of Distribution Networks
Iron Mains replacement programmes 2006 - 2013
- In September 2001 the Health and Safety Executive (HSE) published its Enforcement Policy for the Replacement of Iron Gas Mains. This set out a national decommissioning programme so that all 'at risk' iron gas mains would be removed by March 2032.
- HSE also published the arrangements for reporting and monitoring how Transco met the requirements of the decommissioning programme over the first five years from 2002 to 2007.
- This document revises the monitoring and reporting arrangements for the major distribution network operators (the DNOs) taking account of:
- A revised HSE enforcement policy for 2006 - 2013
- Structural changes in the gas distribution industry in June 2005 when Transco sold four of its eight distribution networks (DNs), followed by Transco changing its name to National Grid Gas plc
- New legislation concerning 'approved' mains replacement programmes
- Requirements for monitoring and reporting described in the DN Operators’ (DNOs) safety cases under the Gas Safety (Management) Regulations 1996 (GSMR).
- The objectives of these arrangements are to:
- Give HSE assurance that decommissioning targets are being met in line with its enforcement policy
- Provide information on the effectiveness of the replacement programme in removing risk
- Set out what reports HSE expects from the DNOs.
Changes in industry structure
- The eight major DNs are operated by:
National Grid Gas plc
East of England
Northern Gas Networks Ltd
North of England
Scotland Gas Networks plc
Southern Gas Networks plc
South of England
Wales & West Utilities Ltd
Wales & West
- The Pipelines Safety Regulations 1996, regulation 13, requires pipeline operators to ensure pipelines are maintained in good repair. Regulation 13A allows operators of iron gas distribution mains to submit a replacement programme to HSE for approval.
- All the DNOs have approved programmes which specify the length of mains requiring decommissioning and how this will be prioritised. HSE will normally approve programmes annually. However, HSE will approve programmes lasting more than one year where the DNO has:
- demonstrated that over the lifetime of the programme at least the same length of ‘at risk’ mains will be removed as would be under consecutive annual programmes,
- prioritise the removal of the highest risk mains each year in the same way as they would under an annual programme,
- ensure that, overall, the same amount of risk is removed through decommissioning as would be under consecutive annual programmes, and;
- set annual targets within the longer programme.
- Under GSMR the DNOs have accepted safety cases describing how they maintain their gas mains and manage their replacement programmes. This includes compliance with the following monitoring and reporting arrangements.
Monitoring and reporting arrangements
DNOs are required to report quarterly and annually to HSE on their progress with their approved programmes. This applies to annual programmes and those programmes lasting more than one year. These are minimum reporting requirements and HSE may require further information where necessary.
- Each quarter (Apr-June, Jul-Sep, Oct-Dec, Jan-Mar) for each network the DNOs are required to report:
- Mains decommissioned, by diameter (<=12", >12"),
- Replacement mains laid (including those by insertion), by diameter (<=12", >12"),
- Comparison of the mains decommissioned and laid against plan,
- Mains decommissioned/laid for reasons of condition or diversion against plan;
- Exception reports where required.
- The quarterly reports should be submitted to HSE within one month of the end of the period to which they relate, including the final quarter, to provide HSE with an early indication of annual performance. HSE notes that quarterly reports are likely to be provisional.
- Each year for each network the DNOs are required to report:
- Annual replacement performance containing the information as required in the quarterly reports,
- The risk band profile in each network. This includes the remaining length of mains in risk bands 0 - 30, 30 - 60, ...210 - 240, > 240 by diameter (<=12", >12") and material (cast, ductile iron),
- The number of 'gas in buildings' (GIB) events
by diameter (<=12", >12") and material type (cast,
spun, ductile iron);
- Number of fractures by diameter (<=12", >12") and material (cast, spun, ductile iron),
- Number of major mains and service related incidents (i.e. a gas explosion resulting in significant damage to property and/or injury),
- An estimate on the risk reduction by network in incidents/annum,
- The seed pipe risk score for the following year,
- The projected replacement by network for the following five years, by diameter (<=12", >12"),
- Where approved programmes have not been met, a report on the reasons and proposals for addressing any shortfall,
- The annual reports should be submitted to HSE by the end of July.
- For annually approved programmes and for approved programmes lasting more than one year the DNOs should provide detailed exception reports with each quarterly report where replacement performance falls below planned targets as below:
- Quarter 1 20%
- Quarter 2 15%
- Quarter 3 10%
- Quarter 4 0%
- The exception reports should give reasons for the shortfall and, for Q1, Q2 and Q3, details of the recovery plans.
- For annually approved programmes where the DNO has not met the programme target HSE will require a detailed explanation and will consider what other action is necessary. For example, this may require the DNO to address this shortfall in the following annual programme. HSE will also consider if further enforcement action is necessary.
- Where the DNO has not met the annual target within an approved programme lasting more than one year HSE will still require a detailed explanation. HSE will also require the DNO to address the shortfall within the remainder of the programme or, if this is not practicable, in the following programme. As with annually approved programmes HSE will also consider if further enforcement action is necessary.
- Replacement programmes are developed using mains risk prioritisation system [MRPS] which provides a risk score, in incidents per km of main, for each mains unit. DNOs can therefore give a risk profile for their networks and an estimate of the risk reduction provided by decommissioning. HSE and the DNOs can then use this information to assess the effectiveness of the programme in removing risk from the network.
- HSE have intervention plans for each DNO, which involve inspecting the DNOs’ compliance with their replacement programmes. The inspections include looking at the procedures for prioritising replacement.
- HSE may consider enforcement action throughout and following the approved programme where appropriate under its enforcement policy. This could involve:
- Requiring an improvement plan where replacement rates fall below target, including issuing Improvement Notices;
- Modifying the approved programme to address any shortfall in replacement targets;
- Prosecution for serious failings to meet replacement targets.
HSE Hazardous Installations Directorate
Gas & Pipelines Unit, December 2005
 Mains replaced through condition and diversion policies do not contribute to the replacement targets under the approved programmes.
 A gas in buildings event is where gas from a leaking main has entered property and reached a concentration level of 20% of the lower explosive limit (LEL).