Pressure-Temperature Ratings

[bao2ye]

For the valve application, some terms confusing me and can anybody please give me some instructions?

What does seat pressure rating means for valve product?

How the valve manufacturing determine the seat material's pressure-temperature ratings?

Thanks

 

[JLSeagull]

I don't know but could guess along two lines of thought. The pressure and temperature rating typically applies to the pressure containing components such as the valve body and flanges. For control valves we often speak of the trim meaning valve plug and seat components.

1.
The valve manufacturers often publish minimum and maximum temperature limits; and pressure drop limits within those temperatures. Perhaps the type 316 stainless steel plug and seat are published to 300 psi differential and Stellite alloy 6 could be published to 600 psi at the same temperature.

B.
The other though could pertain to the forces exerted by the actuator to maintain the seat tighness.

 

[bcd]

Seat pressure rating is the maximum pressure the seat is capable of repeatedly and reliably operating at. It normally goes down as temperature increases, so manufacturers publish pressure-temperature ratings. Often, but not always the case, the seat has a lower pressure rating than the valve body. Especially when the valve has plastic or rubber seals.

There is no industry stanadrd for establishing pressure-temperature ratings and it is left up to the manufacturers to determine their product's limits. It is normally done by testing, but some of the low cost manufacturers just copy the data from their competitors catalogs. Each Manufacturer has different amounts of liability they are willing to extend in order to hype their products, so you will see different ratings from different manufacturers even for the same materials. this is a great question to ask a valve supplier. If they can explain how they do it, then in general, you can trust the product will perform to the ratings they advertise.

bcd