Dear Experts,
A LPG drain drum has been designed to install near LPG loading arm in jetty area. After every ship loading, loading arm and associated piping should be drained to drain drum.There are 3 options can be considered for venting of lpg gas in drain drum.
1- Venting lpg gas to safe location
2- Venting lpg gas to existing refinery flare header via 2 km flare header
3- Installing a separate flare stack in jetty area
Option 1 is not recommended by our technical safety due to lpg flamabilty and hazard.
Option 2 can be considerd but problem is due elevation difference between jetty area and refinery (+53 m), new flare header should be routed to existing refinery flare header with 5% slope toward lpg drain drum.
Option 3 seems is very costly because the source to flare is only from lpg drain drum and lpg loading arm PSV.
From engineering point of view option 2 seems more practical but my problem is to keep positive pressure in new flare header purge gas require to inject in inlet of new header close to loading arm and drain drum.
As purge gas also can sweep liquid in header, purging line can avoid of free draining of liquid in new flare header toward drain drum.
It seems this design is not correct but i don't have any idea to design it in proper way.
Appreciated if somone could shade a light in my problem.