The screw threads of NRS gate valve lift the gate are exposed to fluid being controlled by the valve. This can cause problems if the fluids tend to foul the threads. So the non risint stem gate valve are usually on the clean liquid or gases.
Rising stem gate valve have the threads external to the valve body and are not subject to fouling from the fluid the valve is controlling.
Non rising stem gate valve are usually made from ductile iron, brass and bronze materials, while rising stem gate valves are made from cast or forged steel material. Non rising stem gate valves require less working space and rising stem gate valve need more space to operate.