metal seated ball valve VS soft seated valves

[johnthebest]

Hello everyone
Today I have received a technical query and I want your opinion about it.

Requirement of metal seated ball valve:
1) As per Clause No ..... of Piping material specification, metal seated ball valve shall be considered for operating temperature ≥ 121 Deg C.
2) As per Clause No ..... of Valve material specification, metal seated ball valve shall be considered for design temperature > 180 Deg C.

With respect to above clause, following shall be noted on the philosophy adopted for flare system/network isolation valves:

Flare system/network is designed for 215 Deg C owing to high temperature gas relief from compressor discharge PSV. The flare isolation valves located on compressor discharge will see temperatures above 180 °C and hence these ball type isolation valves are selected as metal-seated valves.

The isolation valves located on relief path from all other systems operating at low temperature does not have relief at higher temperatures (except fire case). Therefore these valves will be soft seated valves which would provide better sealing properties.

in the attached file figure represents the above understanding in schematic form

Client is requested to confirm above contractor understanding.


what are your thoughts?

 

[mk3223]

IMO, the piping system needs to have a proper spec break point for the suitable valve seat material, especially for the low temperature lines which joined to the Flare header.
May consider to perform a relief CFD of the flare piping to determine the potential temperature impact of the branches connections into the flare header.