What is a swing check valve?
Swing check valve is a kind of check valve, which is composed of valve body, valve cover, valve disc and rocker. The valve disc is in a disc shape and rotates around the pin shaft outside the valve seat channel; The channel in the valve is streamlined, and the flow resistance is smaller than that of the straight-through lifting check valve. It is suitable for large-diameter pipeline. Swing check valve can be applied to water, steam, oil, nitric acid, acetic acid, strong oxidizing medium, urea and other media. It is mainly used in petroleum, chemical industry, pharmacy, chemical fertilizer, electric power and other pipelines.
Application of swing check valve
Swing check valve is applicable to nominal pressure PN1.0MPa – 42.0MPa, class150-2500; Nominal diameter DN15 – 1200mm, Nps1/2 – 48; On various pipelines with working temperature of – 196 – 540 ℃, it is used to prevent medium backflow. By selecting different materials (WCB, CF8 (m), CF3 (m), 1gr5mo, 15crmo1v, it can be applied to water, steam, oil, nitric acid, acetic acid, strong oxidizing medium, urea and other media. It is mainly used in petroleum, chemical, pharmaceutical, chemical fertilizer, electric power and other pipelines.
Principle of swing check valve
The opening and closing principle of swing check valve is the same as that of lift check valve. It also acts by itself under the action of fluid pressure and the self weight of valve disc. The difference is that the opening and closing mode of valve disc is rotary movement rather than up and down movement, and the inlet direction of fluid should be on the side that can impact the rotation of valve disc. The closing part of swing check valve is a valve disc or disc equivalent to the pipe diameter, which is suspended in the valve cavity. When the fluid flows forward, the valve disc opens under the action of fluid pressure, and when the pressure drops, the valve disc closes under the action of self weight and countercurrent fluid pressure.
Working principle of swing check valve
Due to the weight of the disc, when the swing check valve is opened, the resistance to the fluid is relatively large. In addition, because the valve disc is suspended in the fluid, the fluid can produce turbulence. This also shows that the fluid pressure drop through swing check valves is greater than that through other forms of check valves. When the flow direction changes suddenly, the valve disc will close on the valve seat violently, which will cause great wear of the valve seat and produce water hammer along the pipeline. In order to overcome this problem, a damping device can be installed on the valve disc and a metal valve seat can be used to reduce the wear of the valve seat.
The swing check valve has a pin mechanism and a valve disc like a door that freely rests on the inclined seat surface. In order to ensure that the valve clack can reach the appropriate position of the valve seat surface every time, the valve clack is set in the pin mechanism, so that the valve clack has enough swing space and makes the valve clack really and fully contact with the valve seat. When the swing check valve is fully open, the fluid pressure is almost unimpeded, so the pressure drop through the valve will be small. The valve disc can be made entirely of metal, or inlaid with leather, rubber or synthetic coverage, depending on the applicable performance requirements. At the pressure on the left side, the force generated by the pressure difference on both sides compresses the valve disc on the valve seat.
Function of swing check valve
The installation position of swing check valve is not limited. It can be installed horizontally in the pipeline or on the vertical or inclined pipeline. However, if it is installed on the vertical pipeline, the flow direction of medium shall be from bottom to top.
Installation of swing check valve
Installation method of swing check valve
The installation method of swing check valve is similar to that of ordinary check valve. The specific installation methods are as follows:
1. Before installation, the rotary check valve should be treated first. The stuffing cover and foam board at both ends of the valve channel should be removed to clean the inner cavity and remove grease stain. Peel off the oil paper on the valve disc surface and remove the oil dirt on the valve disc surface.
2. Select the appropriate installation position, install the swing check valve on the pipeline according to the direction symbol on the check valve, and pay attention not to reverse the flow direction.
3. Let the medium pass through the pipeline, test whether the medium can be prevented from countercurrent, and confirm that it is normal.
Precautions for installation of swing check valve
1. The check valve in the pipeline cannot bear the weight, especially the large check valve should be installed independently and not affected by the pressure generated by the system.
2. The direction marked on the valve body shall be the same as the direction of medium flow.
3. The medium passing through the pipeline shall not contain hard particles to avoid damaging the sealing surface. It is not suitable for the medium containing solid particles and high viscosity.
4. Pay attention to the installation position of swing check valve.
Can swing check valves be installed vertically?
Generally, the swing check valve is installed on the horizontal pipeline. Sometimes the installation conditions are limited and it needs to be installed vertically. Can the swing check valve be installed vertically?
The lift check valve can only be installed horizontally, but the swing check valve is different. It can be installed horizontally or vertically. When installed on the vertical pipeline, the medium will flow from the bottom to the top. However, the swing check valve is usually installed horizontally. If there is a need for vertical installation, the bottom valve can be considered.
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