Gate valve
Gate valve turns up in 2 fields: valves, vacuum. Here is what it means to the people in each one.
Gate valve in valves
A multi-turn isolation valve that lifts a flat or wedge-shaped gate clear of the flow path to open.
The closure member slides across the flow at right angles: either a wedge that jams between two inclined seats or a flat parallel slide. Fully open, the bore is almost unobstructed, so pressure drop is tiny and the line can be rodded straight through. It is built for on-off duty: run partly open, the gate vibrates and the high-velocity jet cuts the seats.
"Isolation on the cooling water header is a 12 inch gate valve, so bring the big wheel key and plan on about forty turns."
Gate valve in vacuum
Full-bore valve with a sliding plate that isolates a high vacuum pump or a load lock from the chamber.
A valve whose sealing plate slides across the bore and presses against a seat, leaving an unobstructed opening when open. Gate valves sit between a chamber and its high vacuum pump, so a turbo or cryo can keep running while the chamber is vented, and between load locks and process chambers on cluster tools. Production versions are pneumatic with position switches and have a maximum pressure difference they may be opened against.
"Close the gate valve before you vent, I don't want to crash another turbo this month."