The gate valve is used as a cut-off medium, and the whole flow is straight when it is fully opened. At this time, the pressure loss of the medium is minimal. Gate valves are usually suitable for working conditions that do not need to be opened and closed frequently and keep the gate fully open or fully closed. Not suitable for use as regulation or throttling. For the high-speed flowing medium, the gate can cause vibration of the gate when it is partially opened, and the vibration may damage the sealing surface of the gate and the valve seat, and the throttling will cause the gate to be eroded by the medium. From the structural form, the main difference is the form of the sealing element used. According to the form of sealing elements, gate valves are often divided into several different types, such as: wedge gate valve, parallel gate valve, parallel double gate valve, wedge double gate valve, etc. The most commonly used forms are wedge gate valves and parallel gate valves.
The function of this type of valve is to only allow the medium to flow in one direction, and to prevent the flow of the direction. Usually this kind of valve works automatically. Under the action of the fluid pressure flowing in one direction, the valve flap opens; when the fluid flows in the opposite direction, the fluid pressure and the self-coincidence of the valve flap act on the valve seat, thereby cutting off the flow. Among them, the check valve belongs to this type of valve, which includes swing check valve and lift check valve. The swing check valve has a hinge mechanism and a valve disc like a door that rests freely on the inclined valve seat surface. In order to ensure that the valve clack can reach the proper position of the valve seat surface every time, the valve clack is designed in a hinge mechanism so that the valve clack has enough space for turning and makes the valve clack truly and comprehensively contact the valve seat.
The valve clack can be made of metal, leather, rubber, or synthetic covering can be inlaid on the metal, depending on the performance requirements. When the swing check valve is fully opened, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. The valve disc of the lift check valve is seated on the sealing surface of the valve seat on the valve body.
Except that the disc can be raised and lowered freely, the rest of the valve is like a shut-off valve. The fluid pressure lifts the disc from the seat sealing surface, and the backflow of the medium causes the disc to fall back onto the seat and cut off the flow. According to the conditions of use, the valve clack can be an all-metal structure, or it can be in the form of a rubber pad or a rubber ring inlaid on the valve clack frame. Like a shut-off valve, the passage of fluid through the lift check valve is also narrow, so the pressure drop through the lift check valve is larger than that of the swing check valve, and the flow rate of the swing check valve is restricted. Rarely, in the production process, in order to make the parameters such as the pressure and flow of the medium meet the requirements of the technological process, it is necessary to install an adjustment mechanism to adjust the above parameters.
The main working principle of the adjustment mechanism is to achieve the purpose of adjusting the above parameters by changing the flow area between the valve disc and the valve disc and the valve seat. These types of valves are collectively referred to as control valves, which are divided into self-driving control valves such as pressure reducing valves and stabilizing valves that rely on the power of the medium itself, and those that are driven by power (such as electricity, compressed air and liquid) Power) is called other drive control valve, such as electric control valve, pneumatic control valve and hydraulic control valve.
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