... gate valve, non-rising stem, rising stem, welded, threade, d, union or colar connection end. casting/forging body. API 6A gate valve: ... the body and the bonnet,metal seal or non-metal seal is used between the seat ... to replace the fill of the valve-stem when the valve bears pressure.The seal surface is ... spring, operation torque is little. The wedge valve gate is sealed by wedge seal surface ,it ...