i would like to know how to prevent the LNG spill or leak in the double block valve when an emergency disconnection is eminent. I will be thankful if you can explain about ERC and PERC.

 

PERC /ERC is pressurized emergency release coupling operated hydraulically. PERC is having 2 valves (double XV) connected with a shear pin. Before the starting of LNG or ammonia ship loading the PERC needs to be armed (activated) In a situation where emergency disconnection is eminent, like high wind velocity, arm movement above allowable limit etc the sequence of operation is as under.

First phase the emergency release coupling alarm is activated to alert regarding the imminent PERC operation.

Second phase the loading facility (loading pump in normal condition) is switched off.

Third the double XV (double valve-XV-mentioned earlier) of PERC is closed.

Fourth the shear pin is broken hydraulically and one valve will be associated with loading arm and the second part with the ship.

Fifth the arm retracts to the parking position .

Hope this answers your question.