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Analysis of Common Failures of Exhaust Valve

Analysis of Common Failures of Exhaust Valve

Dec 27,2021

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Check Valves

MstnLand provides high performance check valve products, including Swing check valve, Lifting check valve, Titling check valve, External check valve, Wafer check valve etc. 


The disc of valve open or close by medium flow is called check valve which is a kind of automatic valve for one-way flow of the pipeline, that is only allowed medium flows in one direction of the pipeline system. The check valve is used to prevent the backflow of medium, the pump and drive motor reversal and the discharge of the container medium. Check valves should be installed in the pump outlet or front of the control valve for maintaining convenience.




Check Valves Types

The valve that opens or closes by the force of the medium flow to prevent the medium from flowing back is called a check valve. Check valves belong to the category of automatic valves, which are mainly used in pipelines where the medium flows in one direction, and only allow the medium to flow in one direction to prevent accidents. According to the structure, it can be divided into lift check valve, swing check valve and butterfly check valve; according to the material, it can be divided into cast iron check valve, brass check valve, stainless steel check valve, forged steel check valve, cast steel check valve.


Check Valve Working Principle

The function of the check valve is to allow the medium to flow in one direction and prevent the flow in the opposite direction. Usually, this kind of valve works automatically. Under the effect 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. It includes a 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 rotation and makes the valve clack truly and comprehensively contact the valve seat. The valve clack can be made of metal, or it can be inlaid with leather, rubber, or synthetic covering, 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 located on the sealing surface of the valve seat on the valve body. According to the conditions of use, the valve disc 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 disc frame. Like a globe 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 there is little restriction in the flow rate of the swing check valve.


Check Valve Installation

1. Swing check valve: The disc of the swing check valve is disc-shaped, and it rotates around the shaft of the valve seat passage. Because the inner passage of the valve is streamlined, the flow resistance is smaller than that of the lift check valve. It is suitable for low flow velocity and large diameter occasions where the flow does not change frequently, but it is not suitable for pulsating flow, and its sealing performance is not as good as the lifting type. Swing check valves are divided into three types: single valve, double valve and multi-valve. These three types are mainly classified according to the valve diameter. The purpose is to prevent the medium from stopping or flowing backward and weaken the hydraulic shock.

2. Lift check valve: it is a check valve whose disc slides along the vertical centerline of the valve body. The lift check valve can only be installed on a horizontal pipeline. The disc can use a round ball on the high-pressure small diameter check valve. . The valve body shape of the lift check valve is the same as that of the globe valve (which can be used in common with the globe valve), so its fluid resistance coefficient is relatively large. Its structure is similar to the globe valve, and the valve body and disc are the same as the globe valve. The upper part of the valve disc and the lower part of the valve cover is processed with guide sleeves. The disc guide can be lifted and lowered freely in the valve guide. When the medium flows downstream, the disc opens by the thrust of the medium. When the medium stops flowing, the valve flap falls on the valve seat by self-sagging to prevent the medium from flowing backward. The direction of the medium inlet and outlet channel of the straight-through lift check valve is perpendicular to the direction of the valve seat channel; the vertical lift check valve has the same direction of the medium inlet and outlet channels as the valve seat channel, and its flow resistance is smaller than that of the straight-through check valve.

Precautions:

1)Do not allow the check valve to bear weight in the piping system. Large check valves should be independently supported so that they are not affected by the pressure generated by the piping system.

2)When installing, ensure that the direction of the medium flow should be consistent with the direction of the arrow marked on the valve body.

3)The lift-type vertical flap check valve should be installed on the vertical pipeline.

4)The lift-type horizontal flap check valve should be installed on the horizontal pipeline.


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