With performing products, say a globe valve or a more complicated actuated valve, there could be (and usually is) a difference in buying price between two competing suppliers.

8 x 6" gate valves butt weld ends schedule 40 for use on LNG @ 10 bar temp minus 165 centigrade

-It should usually be closed Selection of the actuator permits failing the valve open or closed. Your description sounds like you want it to normally be closed and fail open upon loss of signal.

To brush up on my Fluid Mechanics training and specifically focus on valve engineering theory.

Safety Excess Flow Check Valve or "Velocity Fuse" for compressed air.How big is the line? Malema (spelling uncertain) sells a bit larger.

Designing a variety of valves for use within a Fuel Metering Unit. Usually we use O-rings for sealing purposes between sleeves and bores.

There are several modes of failure for a BFW leak off valve. They can fail due to seat leakage casuing micro cavitation whilst in the shut position.

I once installed a 12-inch gate valve in a valve-can on a gathering system. The valve takes almost 100 turns to operate