An 18″ medium pressure (MP) steam main located near to the A904 Bo’ness road ruptured at 23:18 p.m. on 7th June 2000 resulting in a significant loss of MP steam directly into the atmosphere. The steam leak damaged fencing immediately adjacent to the ruptured pipework. Debris and steam was blown across the road until the leak was isolated. The leak also caused significant noise (similar to a jet engine) being heard in the Grangemouth area. A member of the public walking the dog 300 metres away sustained rib injuries from tripping over the dog.

There was significant disruption to the steam supply system for the Complex for approximately one hour until the steam leak could be isolated and as a result of the incident the A904 Bo’ness road was closed for public access until 22nd June whilst repairs were carried out.

The medium pressure (MP) steam main rupture had the potential to cause fatal injury and environmental impact, although no serious injury occurred, and there was only short term impact on the environment.

The critical factors that led to the incident were created a week earlier. Significant levels of condensate built up in the steam line following isolation of a steam trap to gain access for inspection of the tunnel, after the culvert was flooded following the power distribution failure.

The immediate cause of the catastrophic failure of an MP steam distribution pipeline was “condensation induced water hammer” which caused gross overpressure.

KEY ISSUES:
• Management of change (change control procedures);
• Failure to adequately investigate significant plant upsets and to carry out risk assessments;
• Operating regimes and lack of certain site standards;
• Inspection and maintenance of equipment;
• Management structure and organisation;
• Failure to learn lessons from previous incidents/events on-site.

Image Credit: HSE