Rising stem gate valves have the threads external to the valve body. You can see the valve stem is moving up when the valve is opening. In this way you can visually keep track of how far the valve is open.
Non rising stem gate valves have threads that lift the gate are exposed to the fluid being controlled by the valve. This can cause problems if the fluid tends to foul the threads, so non rising stem valves are usually used on only clean liquids and gases.
Non rising stem gate valves requires bigger disc than rising stem gate valve for the same size and class rating, hence the cost is higher.
Non rising stem valves take up less space and rising stem valves require more space.
Rising stem valves are usually made from cast or forged steel while non rising stem valves are more typically brass, bronze or cast iron.
Rising stem gate valves can be used in high pressure rating up to Class 2500, while non rising stem gate valves are normally used for middle pressure rating.
Related Information:API 600 Trim Number Chart
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