I. Working principle of check valve

Check valve refers to relying on the flow of the medium itself and automatically open and close the disc, used to prevent the medium backflow valve, also known as check valve, one-way valve, reverse flow valve and back pressure valve. Check valve belongs to a kind of automatic valve, its main function is to prevent the medium backflow, prevent the pump and the drive motor reverse, and the container medium release. Check VALVES CAN ALSO BE USED IN LINES THAT FEED AUXILIARY SYSTEMS WHERE PRESSURE may RISE ABOVE SYSTEM PRESSURE. Check valve can be divided into swing type check valve (according to the center of gravity rotation) and lift type check valve (moving along the axis).

Check VALVE The purpose of this type of valve is to allow medium to flow in only one direction and to prevent flow in the opposite direction. Usually the valve is automatically operated, under the action of a flow of fluid pressure in one direction, the disc opens; When the fluid flows in the opposite direction, the fluid pressure and the self-overlapping valve disc of the valve disc act on the seat to cut off the flow.

II. Check valve selection:

1. In order to prevent medium counterflow, check valves should be installed on equipment, devices and pipelines;

2, check valve is generally suitable for clean media, should not be used for medium containing solid particles and large viscosity;

3, generally in the nominal diameter of 50mm horizontal pipeline should be selected horizontal lift check valve;

4, straight through lift check valve can only be installed in the horizontal pipeline;

5, for the pump inlet pipeline, should choose the bottom valve, the bottom valve is generally only installed in the pump inlet vertical pipeline, and the medium flow from bottom to top;

6, the lifting type is better than the swing type sealing, fluid resistance, horizontal should be installed on the horizontal pipeline, vertical installed on the vertical pipeline;

7, swing type check valve installation position is not limited, it can be installed in the horizontal, vertical or inclined pipeline, such as installed in the vertical pipeline, the medium flow from the bottom up;

8. Swing check valve can be applied to any working medium and any working temperature range according to the material of shell and seal. The medium is water, steam, gas, corrosive medium, oil, medicine, etc. The working temperature range of the medium is between -196- 800℃;

9, swing check valve is suitable for low pressure large diameter, and installation occasions are limited;

10, the butterfly check valve installation position is not limited, can be installed in the horizontal pipeline, can also be installed in the vertical or inclined pipeline;

III.Check valve structure

Check valve according to the structure, can be divided into lift check valve, swing check valve and butterfly check valve three. Lift type check valve can be divided into vertical and straight through two. Swing check valve is divided into single – valve, double – valve and multi – valve three. Butterfly CHECK valve for butterfly double valve, butterfly single valve, the above check valve in the form of connection can be divided into thread connection, flange connection, welding and clamp connection four kinds.