OS & Y Gate valves

a type of valve commonly used to control water flow to fire sprinkler systems is known as gate valve OS & Y. OS & Y means "external root and yoke" or "outside screw and yoke."

OS & Y gate valves operate by opening and closing through a gate, which lowers or rises from the valve. Increasing the gate allows water to flow through the valve by reducin

g the gate cuts off the water flowing through the valve. When fully open, the typical gate valve has no obstruction in the path of the flow, with consequent loss of 

very low friction

On an OS and Y gate valve, the shutter (A) is connected to a threaded rod (B) with a handle (C) which connects the yoke to the element (D). As the operator rotates the handle counterclockwise, raises the stem from the handle, the opening of the gate. A clockwise rotation of the gate moves the stem back into the gate and closes the valve. 

When the rod does not protrude from the handle, the gate valve is closed. You can watch a slide valve OS & Y and say if it is open or closed by the position of the rod