Introduction to working principle of large diameter gate valve

Introduction to working principle of large diameter gate valve:

According to the configuration of sealing surface, it can be divided into wedge gate valve and parallel gate valve, and wedge gate valve can be divided into single gate pole type, double gate plate type and elastic gate valve; Parallel gate valve can be divided into single gate valve and double gate valve. According to the thread position of the valve stem, it can be divided into rising stem gate valve and non-rising stem gate valve.

1. When the large-diameter gate valve is closed

The sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the ram is pressed to the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves adopt forced sealing, that is, when the valve is closed, the gate plate shall be forced to the valve seat by external force to ensure the sealing of the sealing surface. The ram of the gate valve moves in a straight line with the valve stem, which is called the rising stem gate valve (also called the rising stem gate valve). Generally, there is a trapezoidal thread on the lifting rod. Through the nut on the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into the operating thrust.

2. When the large-diameter gate valve is opened

When the lifting height of the ram is equal to 1:1 times of the valve diameter, the fluid channel is completely unblocked, but this position cannot be monitored during operation. In actual use, the top of the valve rod is used as the mark, that is, the position that can not be opened, as its fully open position. In order to consider the phenomenon of locking due to temperature change, it is usually to turn back 1/2 - 1 turn at the top position as the position of fully open valve. Therefore, the fully open position of the valve is determined according to the position of the ram (i.e., the stroke).