Please see the attached file. Can anyone shed some light as to why it is neccesary to include a mimimum length of piping run downstream of the emergency BDV (upstream the RO). The attached scheme is a typical configuration for all the BDVs at the gas plant where I was a trainee engineer many years back. I have still not been able to figure out why this minimum specified straight run is needed. Does it have anything to do to avoid choked flow?

Thanks.

ashetty,

Major pressure drop take place at RO, downstream of BDV during blowdown. JT effect results fluid temperature downstream of RO drop below subzero. The "coldness" will travel back to upstream of RO. It potentially cause the upstream BDV body temperature drop below subzero. Moisture will freeze at the BDV body and cause it stuck at position. Operate may not possible to close the BDV after blowdown activities and may potentially lead to back flow. Those "general good engineering practice is to locate RO, 600mm downstream of BDV.


JoeWong

Thanks very much indeed Mr.Wong,

It is very basic.I should have thought of that.

Well, at least now i won`t die wondering.

Best Regards.

Very basic does not imply obvious. The greatest expert in the world in theoretical thermodynamics might easily have no clue as to this practical application of the theoretical knowledge. Hence the value of experience (but as a supplement to theory).

Doug,
I like this statement.

Thanks.


JoeWong