All valves are designed to stop, allow or throttle the flow of a process fluid. Gate valves, one of the original valve designs, are ideally suited for on/off, primarily liquid, service.
A gate valve functions by lifting a rectangular or circular gate out of the path of the fluid. When the valve is fully open, gate valves are full bore, meaning there is nothing to obstruct the flow because the gate and pipeline diameter have the same opening. This bore diameter also determines the valve size. An advantage of this full-bore design is very low friction loss, which saves energy and reduces total cost of ownership.