Gate Valve Seats from Solid Stellite

[arosum]

I see that lot of Valve manufacturers use solid stellite 6 seats for sour service Gate valves and majority of the after market seat manufacturers offer cast stellite 6 seats (AMS 5387) but API 6A prohibits the use of castings and clearly ask for wrought products for PSL3 and PSL4 applications.
i am not sure if i am interpreting the requirements correctly or is industry using a wrong material? please advise.

 

[SPDL310]

I'm not 100% on this so take it with a grain of salt.

1.) The seats can be used in PSL 1 and 2 applications with no problem.

2.) PSL 3 also requires serialized parts from the vale manufacturer. If you are repairing a PSL 3 valve with after market parts, you no longer have a PSL 3 compliant valve anyway.

3.) I'm unsure about whether or not aftermarket part manufacturers require an API license as they are technically not manufacturing and/or monograming a product.

4.) A new valve order for a PSL 3 compliant valve will likely come with a carbide seat, and not cast stellite.