Hazard Knowledge

General

The utility industry uses pipelines extensively to transport products around their sites and for distribution around the UK. Pipelines are considered a safe mode of transport for conveying hazardous substances and are often safer than alternative methods, for example by road or rail. Refer to Health and Safety Executive's Further guidance on emergency plans for major accident hazard pipelines.

Fire and rescue service personnel may need to work in close proximity to pipelines while attending incidents at utility and fuel sites.

Other pipelines transport fuels, chemicals, other industrial products and water; these include over 1,000km of Major Accident Hazard Pipelines (MAHPs). Special duties apply to MAHP operators, including a notification regime, production of a major accident prevention document and emergency plan arrangements.

Pipelines buried underground have marker posts and indicators wherever they pass under roads or rail lines. These can be seen in all rural areas and are visible from the air by way of aerial marker posts. See the Linewatch website for typical pipeline markers and examples of marker posts and signs.

While it may be possible to identify the routes of buried pipelines, there is likely to be some delay in the arrival of a pipeline specialist or other specialist at remote rural locations.

Natural gas pipelines

Natural gas distribution in the UK consists of high-pressure gas mains. More than 95% of these are underground, or underwater to supply Northern Ireland.

Pipeline networks make up the UK gas transmission and distribution system for industrial and domestic consumers. These include:

• 278,00km of distribution mains
• 7,500km of high-pressure National Transmission System (NTS) pipelines operating at up to 85 bar
• 14,500km of high-pressure Local Transmission System (LTS) pipelines operating at up to 38 bar

For further information see the Health and Safety Executive's Onshore gas and pipelines sector strategy 2014-17.

High-pressure gas leaks will need to be dealt with by the appropriate gas utility; isolating leaks is not a straightforward task. Gas supplies cannot be isolated quickly and close liaison with the gas supplier will be required.

High-pressure gas is supplied at above 7 bar, and in the UK pressures can be up to 85 bar. This type of pressure can result in significant surface disruption when a leak occurs, and a resulting gas cloud will need to be mapped and monitored.

If there is a serious gas leak in close proximity to an airport, the airport and the Civil Aviation Authority need to be informed of the gas cloud because of the potential effect on aircraft.

Typical causes of pipeline failure

There are occasions when pipeline failure results in loss of containment or accidental release of the pipeline contents, including:

• Impact on the pipelines by construction workers
• Failure of the pipes through stress fractures and corrosion
• Unauthorised drilling into the pipelines for fuel theft
• Impact from external sources such as:
• Aircraft accidents
• Pressure waves caused by explosions
• Structural collapse

Consequences of pipeline failure

Damaged pipelines can result in:

• Fire or explosion hazards
• Release of gases and liquids under high pressure
• Excessive noise
• Impact hazards
• Environmental damage - fuel entering watercourses, etc.
• Flooding

Undamaged pipelines also create problems such as:

• Difficult access and egress
• Extremes of temperature
• Working at height