API 14 C /ISO 10418 FSV in flow lines

[MortenA]

Gents,

In API 14C /ISO 10418 tehre is a figure that shows a number of typical wellheads. (see attached drawings).

http://files.engineering.com/getfil...a-8c88-545f399bec65&file=FSV_in_flowlines.pdf

Does anybody here know if an alternative configuration where the FSC is moved downstream the branching of to production and test manifolds (one on each branc of course) would be in compliance with the tsandard?

Best regards, Morten

 

[amustha1407]

Hi,

Please correct me if i am wrong. The purpose of the check valve there is to avoid back flow when you have a leak on your flowline. Flowlines are prone to leaking, since they are located at the upstream side of the process due to errosion (multiphase flow at high rate) and corrosion (higher Pressure and temperature = higher corrosion rate).

In case a leak occurs, we want to limit the inventory feeding into the leak from the downstream side of the process, the FSV will do this. Putting them at each branch will not defeat the purpose of this (thus i do not see this as in compliance), as long as the distance is not too long from the flowline (the longer the distance to the check valve, the more inventory will feed into the leak). The only other disadvantage that i could think of if you put them on all branch is cost. You will have more check valve to procure and install, this also means additional maintenance task.

 

[MortenA]

I agree with your view - thanks for the comment

 

[LittleInch]

I don't think you need to take these sorts of diagrams too literally, they are just suggestions and recommendations. I would normally call this an NRV rather than an FSV (I find it difficult to rely on a non return valve as a "safety" valve), but that's just semantics. As amusstha has said quite correctly, the key issue on a well pad is to prevent back flow from the flowline onto the well pad in the event of a leak or rupture of the piping downstream the wellhead. Normally the well can be closed remotely, but other valves are often manual and hence it would be difficult to gain access to the well pad if gas and oil was flowing backwards from the flowline. Therefore in my opinion as long as you have NRVs somewhere in the system (close to the wellhead pad boundary is quite common) you've met the overall requirement of the standard / recommended practice.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way