1 reply to this topic

[alfaha]

Dear all,

 

I am currently working at LNG Plant where there will be a flare tip maintenance & inspection every 5 years for 6 days duration. This flare maintenance/inspection will be conducted during total plant shutdown (turn around) where all the processing facility such as, platform, onshore receiving facility, Train, and Utility will be shut-downed and de-inventoried except the refrigerant (propane & ethane) storage. The inventory of propane and ethane at the refrigerant storage is still maintained at its maximum liquid level since this refrigerant storage will be required to start-up the LNG Train after turn around.

 

During this flare maintenance, all the PSV, emergency depressuring system, relief header will be isolated including the PSV, emergency depressuring valve, and relief header for the refrigerant storage. The problem we are facing right now that we don’t have a spare flare installed to accommodate the refrigerant relief scenario and emergency depressuring.

 

The proposal that I am trying to work on right now is to rent and install a temporary flare with only considering the boil off gas case from the refrigerant storage during the main flare maintenance. The fire case and emergency depressuring case aren’t considered for this temporary flare with the following consideration:

 

1.     The flare tip maintenance will be carried for short term duration (6 days).

2.     No incoming and outgoing flow of refrigerant from/to the refrigerant bullet.

3.     The fire case has low probability since the train is shut downed with controlled environment.

4.     Unnecessary electrical source adjacent to the refrigerant bullets will be disconnected during flare tip replacement activities.

5.     ERT (emergency response team) will be standby around refrigerant bullets for 24 x 6 during flare tip replacement.

 

Based on above considerations, it is not practical to rent and install temporary flare and consider the fire case for this temporary flare since the fire possibility will be minimized and under controlled environment.

 

On second thought, I am also considering another option that to reroute the PSV discharge (fire case) into the atmospheric vent in addition to the temporary flare (only boil off gas case). Rerouting the PSV into atmospheric vent is allowed as per API 2510 with certain condition. After evaluating the economic for this atmospheric vent and to comply with API 2510 requirement, the cost is about the same to rent a big temporary flare with fire case scenario. 

 

I would like to hear anyone of you has already had an experience on this kind of situation. I am welcome for any feedback and advice from you.

      

Thanks,

Fajri.

[Zauberberg]

If the vessels are designed according to a Code that specifies pressure relief valves as mandatory protection devices, they must be maintained functional as long as the vessels are in service. With the refrigerant sitting in the vessel, they are considered to be vessels in service. Being in service, suitable relief path needs to be provided. This means either another flare, or venting to atmosphere.

 

Your fire scenario does not seem credible to me. In order for these vessels to be engulfed in a fire, a pool of flammable/combustible liquid needs to be sitting around the vessels. I don't see how this can happen, unless the plant is located in a very cold climate. Or a jet fire from one vessel affecting the other vessel (if the affected vessel is within the hazard zone created by jet fire).