The switch component of gate valve
is disc. There is a vertical relationship between ram direction and fluid direction during operating operation. Gate valves can keep only two states at work, open or close. These two states can't exchange. The ram of valve has two sealing surface. Now the wedge-shaped sealing surface is widely used. Because there are many types of gate valve, the parameters of the gate also is different.
Consequently, the wedge angle is different and is generally of 50. This kind of gate of wedge gate valve can be made into a whole, called the rigid gate; In addition, the gate valve gate can be made to be a gate that can do tiny deformation. The purpose is to improve the technology of gate valves and reduce the deviation of sealing surface angle during manufacturing. We call this type of gate flexible gate.
When opening gate valve, under the condition of the gate hoisting height and gate valve size is 1:1 relationship, the fluid channel is totally unimpeded. However, there is no way to monitor the fluid channel at run time. During actual use, gate valves marked with the stem apex. Stem apex is fixed position or the full open position. Considering the temperature change may result in deadlock phenomenon, usually to open it to vertex positions first, then, to turn back to 0.5 1 turn, as the full open position of the valve. As a result, the fully open position valve depends on the location of the gate.
When the gate valve is closed, sealing surface can only rely on medium pressure to seal, which is pressed valve sealing surface of the gate to the other side of the seat with medium pressure, to ensure the sealing surface is sealed. People call it self-sealing. Only a handful of gate valves adopts the self-sealing. Most of gate valves use mandatory sealing, namely that the valve is closed rely on outside force to enforce the gate stress on the valve seat.
When disc does rectilinear motion with stem, the valve is called as lifting lever gate, also called as rising stem gate valves. In general, there is a trapezoidal thread on the lifting lever. Through the nut at the top of the valve and the guide groove on valve body, can turn rotary motion to linear motion. That is to transfer operating torque into operating thrust.
Some valve stem nut of gate valve set on the gate. When the handwheel runs, valve stem will be driven and result in rising the gate. We call this valve rotating lever gate valve, also called non-rising stem gate valves.
The advantages of gate valves:
(1) Small fluid resistance; Sealing surface won’t be eroded by the medium easily.
(2) Labor-saving operation.
(3) The flow direction of medium is not restricted, no disturbed flow, reducing the pressure.
(4) Simple form; short structure length; good manufacturing performance; wide application scope.
The faults of gate valve:
(1) It’s easy to cause erosion and abrasion between the sealing surface; It’s difficult for maintenance.
(2) The dimension is bigger; It needs certain space to open and a longer opening and closing time.
(3) The structure is relatively complex.
Types of gate valve in accordance with the sealing surface configuration can be divided into wedge gate valve gate and parallel slide gate valves. The gate of wedge gate valve can be divided into three kinds: single disc; double disc; flexible disc; Parallel slide gate valve can be divided into two kinds: single sluice gate valve and double sluice gate valve. According to the threads of the valve stem position to differentiate, can be divided into rising stem gate valves and non-rising stem gate valves.
Attentions for installing and maintaining gate valves:
(1)The handwheel, handle and drive mechanism cannot be used for lifting. Collision should be strictly prohibited.
(2) Double disc gate valve should adopt vertical installation method, namely stem is in a vertical position. The hand wheel is in the top position.
(3) Open the bypass valve before opening the gate valve with a bypass valve. It’s used to balance the pressure difference of exits and entrances, and reduce the opening force.
(4) The gate valve with belt transmission mechanism should be in accordance with the instructions to install the product.
(5) If the valve is often switched, it’s necessary to do nursing job and lubricate it at least once a month.