Pig trap door closure and hub corrosion risk assessment
Jee’s client manufactures and supplies pig traps as well as the associated doors/end closures. Where there is a high threat of corrosion to the pig trap door an Inconel overlay is usually used to mitigate the risk of failure.
Our client had recently supplied four pig traps to an operator which did not include the Inconel overlay on the doors. Upon delivery of the pig traps, the operator asked our client to supply further information regarding the risks arising from corrosion on the doors and to provide assurance that the design of the pig trap doors was suitable for a 30 year design life.
We were contracted, as an independent third party, to perform a corrosion risk assessment to quantify the risk of unacceptable levels of corrosion occurring on the pig trap doors over their design life, taking into consideration their expected operating conditions.
We identified a range of corrosion mechanisms that could potentially affect the pig trap doors. A qualitative assessment was then performed to define the probability and consequence of failure as a result of each corrosion mechanism using the risk matrix given in DNV-RP-F116.
The risk assessment concluded that there was not a high risk of failure on any of the four pig traps doors.
Recommended actions were also provided with the aim of giving further assurance that the pig trap doors would be maintained in good condition over the duration of their design life.
Our assessment was used by the pig trap fabricator to satisfy their client that there was no significant risk of pig trap door failure as a result of corrosion arising from the missing Inconel overlay.
The results of this study ultimately ensured that a good relationship was maintained between our client and the operator, as well as saving our client significant fabrication costs for new closures.