All of the design drawings I've seen over the years show gate valves as full bore design. That is, with the gate fully open nothing protrudes into the flow.

During the pressure test of a piping system, 3 out of 20 3/4" #800 gate valves had a minor leakage,(according to customer inspector about 1 drop per minute).

If particulate is an issue, and you decide to use a ball valve, a metal-seated ball valve would be in order.

The API and ASME standards have in common that they cover pipeline equipment (and valves). However they have a different origin.

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.