Introduction: There are 208 pig traps on the NTS all holding a volume of gas at line pressure. Recently there has been an upwards trend in the number of seals failing per year. When the seals fail there is a release of gas to atmosphere. At which point National Grid must isolate the pig trap to stop emissions and repair.

A previous project looking at improving the over-all integrity of Pig Trap Enclosures set the groundwork for this investigation into the elastomer seals fitness for purpose. To understand the cause/source of failure the first phase of work will include a review of existing enclosure and seal details, operating duties and procedures, and seal failure analysis. To establish fitness for purpose and identify potential alternatives, work will be done to establish likely failure modes and will include possible contributory factors / issue findings. Recommendations will then be identified for alternative seals or other solutions to avoid future failures.

Objectives:

The goal of this project is to understand the cause/source of pig trap closure seal failures, and investigate the fitness for purpose of existing and alternative elastomer seals; with an aim to preventing future failures.

Expected Benefits: The project will propose a number of suitable potential solutions as alternatives to the current seal.