1. Gate valve

It is also called gate valve or gate. The movement direction of the gate valve is perpendicular to the fluid direction. The gate valve can only be fully opened and fully closed, but can not be adjusted and throttled. According to the configuration of sealing surface, it can be divided into wedge gate valve and parallel gate valve. Wedge gate valve can be divided into single gate * type, double gate plate type and elastic gate type; Parallel gate valves can be divided into single gate plate and double gate plate.

According to the thread position of the valve stem, it can be divided into rising stem gate valve and Non rising stem gate valve. Classification of gate valve driving mode: manual gate valve, pneumatic gate valve and electric gate valve.

2. Ball valve

Ball valve is defined in the standard GB / t21465-2008 valve terminology as a valve whose opening and closing parts (ball) are driven by the valve stem and rotate around the axis of the valve stem.

It is mainly used to cut off or connect the medium in the pipeline, and can also be used for fluid regulation and control. There is a strong shear force between the V-shaped ball core of the hard sealed V-shaped ball valve and the metal valve seat of surfacing cemented carbide, which is especially suitable for media containing fiber, micro solid particles and so on.

The multi-way ball valve can not only flexibly control the confluence, diversion and flow direction switching of media on the pipeline, but also close any channel to connect the other two channels. This type of valve shall be installed horizontally in the pipeline. Ball valve classification: pneumatic ball valve, electric ball valve, manual ball valve.

3. Butterfly valve

Butterfly valve, also known as butterfly valve, is a valve whose opening and closing parts are disc-shaped disc plates and can rotate around the axis of the valve body. It is mainly composed of valve body, valve rod, disc plate and sealing ring. The valve body is cylindrical with short axial length and built-in disc plate. The disc plate is driven by the valve rod. If it is turned 90 °, it can complete one-time opening and closing. Changing the deflection angle of the disc plate can control the flow of the medium.

The main seal is the sealing ring, which is made of materials according to the purpose and medium. There are two kinds of commonly used butterfly valves: wafer butterfly valve and flange butterfly valve. The wafer butterfly valve connects the valve between two pipe flanges with stud bolts. The flange butterfly valve has flanges on the valve, and the flanges at both ends of the valve are connected to the pipe flanges with bolts.

4. Stop valve

The stop valve is a forced sealing valve, so when the valve is closed, pressure must be applied to the valve disc to force the sealing surface not to leak. When the medium enters the valve from below the valve disc, the resistance to be overcome by the operating force is the friction between the valve stem and packing and the thrust generated by the pressure of the medium. The force to close the valve is greater than the force to open the valve, so the diameter of the valve stem should be larger, otherwise the failure of valve stem jacking will occur.

In recent years, after the emergence of self sealing valve, the medium flow direction of stop valve changes from above the valve disc to enter the valve cavity. At this time, under the action of medium pressure, the force to close the valve is small, while the force to open the valve is large, and the diameter of valve rod can be reduced accordingly. At the same time, under the action of medium, this form of valve is also more tight. The "three modernizations" of valves in China once stipulated that the flow direction of stop valves should be from top to bottom.

Extended data

All valves in operation shall be complete and intact. Bolts on flanges and supports are indispensable, and threads shall be intact without looseness. If the fastening nut on the hand wheel is found to be loose, it shall be tightened in time to avoid wearing the connection or losing the hand wheel and nameplate. If the hand wheel is lost, it is not allowed to replace it with a monkey wrench, and it shall be equipped in time. The packing gland shall not be skewed or have no pre tightening clearance.

For valves in the environment vulnerable to dirt such as rain, snow, dust and sand, the valve stem shall be equipped with a protective cover. The scale on the valve shall be complete, accurate and clear. The lead seal, cap and pneumatic accessories of the valve shall be complete and intact. The insulation jacket shall be free of depression and crack. It is not allowed to knock, stand or support heavy objects on the running valve; Especially non-metallic valves and cast iron valves should be prohibited.

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