During maintenance on wellhead, the SSSV hydraulic master and wing valves were opened. The choke was opened to 25% (the 6" production block valve downstream of the venturi was closed), pressurising the system to a CITHP of 233bar. During a local inspection of the plant, a gas leak was noticed coming out of 1 leg of the 3/8" 'T' piece fitting to the DP cell and pressure gauge. There was also a separate gas leak at the seal point of the isolation valve integral to the manifold block. The local gas detection did not activate.
Metallurgical analysis discussion stated that austenitic stainless steels are particularly susceptible to stress corrosion cracking in the presence of aqueous chlorides at elevated temperatures.
- Confirm all other fittings in the same service are gas tight and show no signs of deterioration
- Take further samples of the population of fittings to gauge whether a system issue – completed and found to be isolated case
Pipework & Fittings, Valve, Wellhead