Replace ductile iron gas mains in non-Transco networks, warns HSE.

HSE Press Release E201:02 - 21 October 2002

The Health and Safety Executive (HSE) is warning occupiers of sites and localauthorities with their own gas mains that medium pressure ductile iron (MPDI) pipes need to be replaced.

This follows enforcement action requiring Transco to carry out an agreed accelerated programme of replacement of all MPDI gas mains located within 30 metres of buildings. This work is due for completion by the end of 2002.

The risk of failure of MPDI mains located close to buildings is such that they should be replaced on all networks as soon as reasonably practicable. As a result HSE is to begin a programme of work to ensure non-Transco MPDI networks are also replaced as soon as possible.

HSE has recently been notified of a small number of sites where such networks may be in place and are contacting the owners of these premises. HSE is also contacting the owners of other sites such as hospitals, universities, prisons, Ministry of Defence premises as well as some industrial and commercial premises to eliminate any other potential problem areas.

Dan Mitchell, Head of Land Division, HSE Hazardous Installations Directorate, said

"Presently we don't know how many of these networks exist. Although Transco has brought a number to our attention, there may be many more. Occupiers of large sites and local authorities need to establish who own the pipes, determine what material they are made of and, where appropriate, implement a suitable programme of replacement.

"The problem with ductile iron is that it can fail unpredictably. In view of this and the difficulties with accurately assessing its condition, mains close to property need to be replaced as soon as reasonably practicable. As Transco's programme is drawing to a close, HSE is now turning its attention to other organisations who may own MPDI networks.

"This is an important issue and inspectors will be taking a firm enforcement line to ensure occupiers take the necessary action promptly."

While HSE is currently focusing on MPDI networks, occupiers and local authorities should be aware that there is also an aging population of cast iron and low pressure ductile iron networks which should be considered for replacement.

Notes to editors

1. Cast iron mains can fail unpredictably particularly through fracture if exposed to excessive loading, such as heavy traffic or ground movement. Ductile iron pipe was introduced in the 1970s in response to problems with cast iron. It has greater strength and flexibility compared with cast iron. It was later found, however, that ductile iron could fail unpredictably through corrosion. When this happens, there is a risk that the gas will track into adjacent properties, where it may subsequently be ignited. Ductile and cast iron have now been superseded by polyethylene for all low and medium pressure mains.

2. Transco has already replaced all MP cast iron mains below 12" diameter within 20 metres of property.

3. "Medium pressure" means a pressure above 75 millibar.

4. An Improvement Notice was served on Transco in September 2000 to confirm an agreement reached that all "at risk" MPDI mains should be replaced by the end of 2002, a total length of 2,300 km.

5. An Improvement Notice is a statutory notice requiring specified improvements to be made within an agreed time scale. A failure to comply is a prosecutable offence under the Health and Safety at Work etc. Act 1974 (the HSW Act).

6. Recipients have the right to appeal against an Improvement Notice under Section 24(2) of the HSW Act, which states: "A person on whom a notice is served may within such period from the date of its service as may be prescribed appeal to an Employment Tribunal; and on such an appeal the tribunal may either cancel or affirm the notice and, if it affirms it, may do so either in its original form or with such modifications as the tribunal may in the circumstances think fit."

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