Import gas had been introduced to platform after a considerable shutdown. A detailed gas-compression re-commissioning procedure was being followed.
During commissioning of an HP compressor, an individual involved in the commissioning operation identified that gas was emanating from the bonnet vent port of a 2 ½ “ safety relief valve.
The suction pressure of the HP compressor is controlled by a pressure controlling valve and the safety relief valve protects the HP compressor. Due to the 9 barg operating pressure of the HP flare system, the safety relief valve is of balanced bellows design.
Upon discovery of the leak, the decision was made to initiate a manual blow-down and this was carried out and completed a short time after.
Subsequent investigations have revealed that the leak was caused by a crack in the bellows which allowed HP flare-gas to escape via the vent port.
The bellows in balanced bellows relief valves have a finite life and as such should be treated as consumables.
Ensure that suitable and sufficient maintenance routines are in place for bellows in balanced bellows relief valves which are in line with manufacturers recommend max-life.
2 ½ “ balanced bellows safety relief valve protecting an HP compressor.