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What Is Check Valve?

Views: 84     Author: Site Editor     Publish Time: 2020-01-07      Origin: Site

What Is Check Valve?

Check valve is a kind of valve whose opening and closing parts are round disc and whose action is generated by its own weight and medium pressure to block the backflow of medium. It belongs to automatic valve, also known as check valve, return valve or isolation valve. It is mainly used in the pipeline with unidirectional flow of medium. It only allows the medium to flow in one direction to prevent accidents.

1. Working Principle

The check valve can be divided into swing check valve (rotating according to the center of gravity) and lift check valve (moving along the axis). Usually this valve works automatically. Under the action of the fluid pressure flowing in one direction, the valve disc opens; when the fluid flows in the opposite direction, the valve disc acts on the valve seat by the fluid pressure and the self weight of the valve disc, thus cutting off the flow. 

The swing check valve has a hinge mechanism, and a disc like a door freely resting on the inclined seat surface. In order to ensure that the valve clack can reach the proper position of the seat surface every time, the valve clack is designed in the hinge mechanism, so that the valve clack has enough swing space, and makes the valve clack truly and comprehensively contact with the seat. The valve flap can be made of metal completely, or inlaid with leather, rubber or synthetic coverage on the metal, which depends on the requirements of service performance. 

When the swing check valve is fully open, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. The disc of the lift check valve is located on the sealing surface of the valve seat on the valve body. Except that the valve disc can be lifted freely, the rest of the valve is like a globe valve. The fluid pressure makes the valve disc lift from the sealing surface of the valve seat, and the backflow of the medium causes the valve disc to fall back to the valve seat and cut off the flow. According to the service conditions, the valve disc can be of all metal structure or inlaid with rubber pad or rubber ring on the valve disc frame. Like the stop valve, the passage of fluid through the lift check valve is narrow, so the pressure drop through the lift check valve is larger than that of the swing check valve, and the flow of the swing check valve is limited rarely.

sanitary check valves

 2. Structure Classification

(1) by structure

Lift check valve can be divided into vertical and horizontal type. 

Swing check valve can be divided into three types, single disc type, double disc type and multi disc type. 

Butterfly check valve, it is pass-through type. 

The above check valves can be divided into four types of connection, threaded connection, flange connection, welding connection and wafer connection. 

(2) classification by material

① Cast iron check valve

② Brass check valve

Stainless steel check valve

④ Carbon steel check valve

⑤ Forged steel check valve

(3) Classification by Function

① DRVZ silent check valve

② DRVG silent check valve

③ NRVR silent check valve

④ SFCV rubber flap check valve

⑤ DDCV double disc check valve

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