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Internal thread aerosol valve and external thread aerosol valve
Internal thread aerosol valves, high-pressure gate valves, and corrugated pipe shut-off valves are mandatory sealing valves, so when the valve is closed, pressure must be applied to the disc to force the sealing surface to leak.

Structural principle of internal thread aerosol valve



Internal thread aerosol valve, high-pressure gate valve, bellows stop valve are forced sealing valves, so when the valve is closed, pressure must be applied to the disc to force the sealing surface to leak. When the medium enters the valve six from below the disc, the resistance that the operating force needs to overcome is the thrust generated by the friction between the valve stem and the packing and the medium pressure. The force of closing the valve is greater than the force of opening the valve, so the diameter of the valve stem must be large, otherwise the valve stem will be warped and fail. After the appearance of the self-sealing valve, the medium flow direction of the shut-off valve enters the valve cavity from above the valve clack. At this time, under the action of the medium pressure, the valve closing force is small and the valve opening force is large, and the diameter of the valve stem can be reduced accordingly. At the same time, under the action of the medium, this kind of valve is also tighter. my country's "Sanhua" valve once stipulated that the flow direction of the stop valve should be from top to bottom.



When the internal threaded aerosol valve is opened, when the opening height of the valve flap is 25% to 30% of the nominal diameter, the flow has reached the maximum value, indicating that the valve has reached the fully open position. Therefore, the fully open position of the shut-off valve should be determined by the stroke of the valve flap.

 1 英寸计量阀,200mcl 剂量.webp


 

Precautions

The handwheel and handle-operated corrugated pipe stop valve can be installed in any position of the pipeline.

Handwheels, handles and transmission mechanisms are not allowed to be used for lifting.

The flow direction of the medium should be consistent with the direction of the arrow shown on the valve body.

The internal thread aerosol valve, also called the cut-off valve, is the most widely used valve. The reason why it is popular is that the friction between the sealing surfaces is small during the opening and closing process, which is relatively durable, and the opening height is not large. Easy and convenient to maintain, not only suitable for medium and low pressure, but also suitable for high pressure. Its closing principle is to rely on the pressure of the valve stem to make the sealing surface of the disc and the sealing surface of the valve seat closely fit to prevent the medium from flowing.

The internally threaded aerosol valve only allows the medium to flow in one direction, and is directional when installed. Its structural length is longer than that of the gate valve, and the fluid resistance is large, and the sealing reliability is not strong during long-term operation.

 

Comparison between internal thread aerosol valve and external thread aerosol valve

From the point of use: Due to the price and working flow requirements, most of the market uses internal threaded aerosol valves.

From the channel: Taking into account the threaded connection, the diameter of the external thread of the same caliber is smaller than that of the internal thread, the flow rate is faster, and the flow rate is small.

From the appearance: most of the internal threads are management lines, the external threads are mostly taper threads, and the bite-type external threads are management lines.

From the point of pressure resistance: the valve wall of the same material with external thread is usually thicker than the internal thread (the smaller the diameter, the thicker the wall), and the pressure resistance is greater. This is also the reason why valves with large pressure levels are all external threads.

 

Threaded valve sealing form

1、直接密封:内外螺纹直接起密封作用。为保证接头不漏水,常在接头处填充铅油、麻和聚四氟乙烯胶带;其中,聚四氟乙烯胶带的应用越来越广泛;这种材料具有良好的耐腐蚀性和优良的密封效果,使用和储存都很方便。拆开的时候完全可以收进去,因为它是不粘的薄膜,比铅油和线麻好很多。

2、间接密封:螺纹的拧紧力传递到两个平面上的垫片上,使垫片起密封作用。

 

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