RR1186: Failure rates for above ground major accident hazard pipelines outside above ground installations
Major accident hazard pipelines transport hazardous fluids, such as natural gas, that have the potential to harm people in the vicinity in the event of an unplanned release from a pipeline failure. Major accident hazard pipelines are defined under the Pipelines Safety Regulations (1996). Dutyholders must implement effective control measures to prevent pipeline failure. Land-use planning law is an important extra precaution to limit the potential risk to the public. HSE is a statutory consultee for proposed land-use developments. HSE sets land-use planning zones and provides advice to local planning authorities on proposed developments within these zones. HSE uses a quantified risk assessment approach as part of its decision making. The quantified risk assessment uses estimated pipeline failure rates. HSE has an established method for determining failure rates for pipelines that are either buried, or are above ground and within an above ground installation (AGI) such as a gas treatment works or gas compression station.
This report describes a methodology to estimate failure rates for pipelines that are above ground but not within an AGI. For instance, sections of pipeline along the side of railways or roads may be above ground due to topographical constraints. Some of the potential failure causes are the same as, or similar to, those for above ground pipelines within an AGI. However, some are different, such as potential failure due to a train crashing into a pipeline if effective measures to prevent this are not in place. The methodology is in use by HSE. The report also describes the software application developed for use of the failure rate methodology within HSE. The report will be of interest to specialists in risk modelling for major hazards.
This report and the work it describes were funded by the Health and Safety Executive. Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
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