There are many types and complex types of valves, mainly including gate valves, globe valves, throttle valves, butterfly valves, plug valves, ball valves, electric valves, diaphragm valves, check valves, safety valves, pressure reducing valves, steam traps and emergency shut-off valves, etc. , which are commonly used gate valve, globe valve, throttle valve, plug valve, butterfly valve, ball valve, check valve, diaphragm valve.
1 Butterfly valve
Butterfly valve is the opening and closing function of the butterfly plate can be completed by rotating 90° around the fixed axis in the valve body. Butterfly valve is small in size, light in weight and simple in structure, and only consists of a few parts. And it only needs to rotate 90°; it can be opened and closed quickly, and the operation is simple. When the butterfly valve is in the fully open position, the thickness of the butterfly plate is the only resistance when the medium flows through the valve body, so the pressure drop generated by the valve is very small, so it has better flow control characteristics. Butterfly valve is divided into elastic soft seal and metal hard seal. Elastic sealing valve, the sealing ring can be inlaid on the valve body or attached to the periphery of the disc, with good sealing performance, which can be used for throttling, medium vacuum pipelines and corrosive media. Valves with metal seals generally have a longer life than those with elastic seals, but it is difficult to achieve complete sealing. They are usually used in occasions with large changes in flow and pressure drop and requiring good throttling performance. Metal seals can adapt to higher operating temperatures, while elastic seals have the defect of being limited by temperature.
2 Gate valve
Gate valve refers to the valve whose opening and closing body (valve plate) is driven by the valve stem and moves up and down along the sealing surface of the valve seat, which can connect or cut off the passage of fluid. Compared with globe valve, gate valve has better sealing performance, less fluid resistance, less effort to open and close, and has certain adjustment performance. It is one of the most commonly used block valves. The disadvantage is that the size is large, the structure is more complicated than that of the globe valve, the sealing surface is easy to wear, and it is not easy to maintain. Generally, it is not suitable for throttling. According to the position of the thread on the gate valve stem, it is divided into two types: open rod type and dark rod type. According to the structural characteristics of the gate, it can be divided into two types: wedge type and parallel type.
3 Check valve
The check valve is a valve that can automatically prevent the backflow of the fluid. The valve flap of the check valve is opened under the action of the fluid pressure, and the fluid flows from the inlet side to the outlet side. When the pressure on the inlet side is lower than that on the outlet side, the valve flap will automatically close under the action of the fluid pressure difference, its own gravity and other factors to prevent the fluid from flowing backwards. According to the structure, it can be divided into lift check valve and swing check valve. The lift type has better sealing performance and larger fluid resistance than the swing type. For the suction port of the suction pipe of the pump, the bottom valve should be selected. Its function is to fill the inlet pipe of the pump with water before starting the pump; keep the inlet pipe and the pump body filled with water after the pump is stopped, so as to prepare for restarting again. The bottom valve is generally only installed on the vertical pipeline of the pump inlet, and the medium flows from bottom to top.
4 Globe valve
The globe valve is a downward closed valve, and the opening and closing member (valve) is driven by the valve stem to move up and down along the axis of the valve seat (sealing surface). Compared with gate valve, it has good adjustment performance, poor sealing performance, simple structure, convenient manufacture and maintenance, large fluid resistance and low price.
5 Ball valve
The opening and closing part of the ball valve is a sphere with a circular through hole, and the sphere rotates with the valve stem to realize the opening and closing of the valve. The ball valve has a simple structure, fast switching, convenient operation, small size, light weight, few parts, small fluid resistance, good sealing performance and convenient maintenance.
6 Throttle valve
The structure of the throttle valve is basically the same as that of the globe valve except for the valve disc. The valve disc is a throttling component, and different shapes have different characteristics. The diameter of the valve seat should not be too large, because the opening height is small. The medium flow rate increases, so Accelerates erosion of the valve disc. The throttle valve has small dimensions, light weight and good adjustment performance, but the adjustment accuracy is not high.
7 Plug valve
The plug valve uses a plug body with a through hole as the opening and closing part, and the plug body rotates with the valve stem to realize the opening and closing of the valve. The plug valve has the advantages of simple structure, quick switching, convenient operation, small fluid resistance, few parts and light weight. There are straight-through, three-way and four-way plug valves. The straight-through plug valve is used to cut off the medium, and the three-way and four-way plug valves are used to change the direction of the medium or divide the medium.
8 Diaphragm valve
The opening and closing part of the diaphragm valve is a rubber diaphragm, which is sandwiched between the valve body and the valve cover. The middle protruding part of the diaphragm is fixed on the valve stem, and the valve body is lined with rubber. Since the medium does not enter the inner cavity of the valve cover, the valve stem does not need a stuffing box. The diaphragm valve has simple structure, good sealing performance, easy maintenance and small fluid resistance. Diaphragm valves are divided into weir type, straight-through type, right-angle type and direct-flow type.
Post time: May-12-2022
