What are the national standard requirements for installing gate valve stem nuts?

The national standard GB/T 12234 "steel gate valve with bolted bonnet for oil and gas industry" stipulates that the stem nut should be loaded from the upper part of the bracket, and the upper part of the stem nut of the gate valve should be a prismatic body, a cylinder with a keyway, or a structure of equal strength connected with the handwheel. When the valve is opened, the handwheel can be removed without causing the stem and gate to fall to the closed position. If a bearing gland with threads is applied, it shall be secured by spot welding or other means.