Gate valve

The gate faces can be parallel but are most commonly wedge-shaped (in order to be able to apply pressure on the sealing surface).

[1] The size of the open flow path generally varies in a nonlinear manner as the gate is moved.

As the gate is pushed against its guiding rail by the pressure of the medium, it becomes harder to operate the valve.

Nonrising stem valves are fixed to, and rotate with, the actuator, and are threaded into the gate.

This construction is adopted for valves for high pressure service, typically in excess of 2250 psi (15 MPa).

Other constructions where the seal is provided by external clamping pressure tend to create leaks in the body-bonnet joint.

A knife gate valve is usually not wedge shaped and has a tapered knife-like edge on its lower surface.