Among USA fire safe design standards check API 6FA Fire safe valves including API 6A and 6D valves and API 607 Fire safe quarter turn valves applicable to ANSI B16.34 valves. For the WWS2 - Worldwide Standards II Combined Index consider the SABS - South African Bureau of Standards 1056-1. Ball valves Part 1: Fire-safe valves.
Adding to John's excellent post
We used a lot of "fire safe" ball valves from different companies. All our valves were metal seated with the stem captured by the packing gland. We had a fire that exposed 5 of the valves, 3" and 4" flanged valves, to very intense heat with only one that showed any signs of leaking around the stem. There were 4 different manufactures valves represented.
One thing we did find that it required varying torque to operate the different valves.
We also had stem failures in some of the larger valves, 6" and above, due to stem failure. We had no blowouts but a lot stem twisting that required refurbishing the valves with a redesigned stem.
I would like to know, if it is ever possible (in this new technology) for a firesafe valve to have soft seat. If yes pls let me know, if not pls let mw know also.
Thanks
1ton
I do not know what new technology you address. However, many fire-safe valves have a soft seats. Metal seats become an issue when the process design temperature exceeds the limits of commonly used elastomers.
My previous post excluded some standards that you may want to see. One is API STD 589 for valve stem packing leak testing. API 598 includes the maximum allowable seat leak rates for acceptance testing. Also obtain copies of API 6FB and 6FC.
Tsenthil was querying about a Ball Valve fire safe design (not the test).
Fire safe design applies to both soft and metal seated ball valves but the way it is achieved is practically the same:
a)A Soft seated valves: at Seats/Ball interface the seat is designed with a lip which secure the M/M seating once the soft seal insert is melting down.
b) For M/M seated this contact M/M is continuous;
1)Consider for both cases above, valves are trunion mounted and as such at LP the contact Seat/Ball is helped by springs whilst at HP is the pressure itself keeping the upstream seat in contact with the ball.
2)for external leaks all sealing areas (Body/adapters or Body/cover flage and Body/stem) a secondary sealing system,mostly graphite must be provided for this purpose.
Design, is sure, must be validated by Fire Safe tests as already mentioned.
