Gate Valve Stem Design:

Gate valves are categorized as either rising stem or nonrising stem valves. To the nonrising stem gate valve then the stem is threaded on the lower end into the gate. Since the hand wheel on the stem is rotated then the gate travels up or down the stem on the threads although the stem remains vertically stationary. This category valve will almost always have a pointer-type indicator threaded on the upper end of the stem to denote valve position. Figures described rising-stem gate valves and nonrising stem gate valves.

The nonrising stem configuration places the stem threads inside the boundary established through the valve packing out of contact along with the environment. That configuration assures in which the stem merely rotates within the packing without much danger of carrying dirt within the packing from outside to inside.

Rising stem gate valves are designed so in which the stem is increased out of the flowpath while the valve is open. Rising stem gate valves come within two basic designs. A few have a stem that rises by the handwheel when others have a stem which is threaded to the bonnet.