The selection standard of check valve is as follows:
1, In order to prevent the medium from counterflow, check valves should be installed on equipment, devices and pipelines;
2, Check valve is generally suitable for clean medium, should not be used for containing solid particles and high viscosity medium;
3, Generally in the nominal diameter of 50mm horizontal pipeline should be selected horizontal lift check valve;
4, Straight-through lift check valves can only be installed in horizontal pipelines;
5, For the pump inlet pipeline, the bottom valve should be selected, the bottom valve is generally only installed on the vertical pipeline of the pump inlet, and the medium flows from bottom to top;
6, Lifting type is better than swing-type sealing, fluid resistance is large, horizontal type should be installed on the horizontal pipeline, vertical installed on the vertical pipeline;
7, Swing 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, medium flow from the bottom to the top;
8, Swing check valve should not be made into small caliber valve, can be made into a very high working pressure, nominal pressure can reach 42Mpa, and nominal diameter can also be very large, the maximum can reach more than 2000mm. According to the material of the shell and the seal, it can be applied to any working medium and any working temperature range. The medium is water, steam, gas, corrosive medium, oil, medicine, etc. Medium operating temperature range between -196--800℃;
9, Swing check valve is suitable for low-pressure large diameter, and installation occasions are limited;
10, 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;
11, The diaphragm type check valve applies to produce water hammer on the pipeline, the diaphragm is a good way to eliminate water hammer produced by a dielectric upstream, it is generally used in low pressure pipe at room temperature, especially suitable for the water pipe, the general work of medium temperature between - 12-120 ℃, pressure < 1.6 MPa, but the diaphragm type check valve can be a large, DN can reach more than 2000mm;
12, Ball check valve is suitable for middle and low pressure pipeline, can be made of large diameter;
13, Spherical check valve shell material can be made of stainless steel, the hollow ball seal can be wrapped PTFE engineering plastic, so in the general corrosive media pipeline can also be applied, the working temperature between -101--150℃, the nominal pressure is less than or equal to 4.0MPa, the nominal warp range between DN200 and DN1200;
14, For the incompressible fluid with check valve selection, the first step is to evaluate the required closing speed, the second step is to select the type of check valve that may meet the required closing speed;
15, For compressible fluid with check valve when the choice according to non-compressible fluid using similar methods to choose the check valve, if the medium flow field is very big, the check valve can be used for compressible fluid, a speed reducer, if the medium flow continuous period of not to stop and start quickly, as the export of compressor, use the lift check valve;
16, Check valve should determine the appropriate size, the valve supplier must provide the selected size of data, so that you can find the size of the valve when the valve is fully open at a given flow rate;
17, For DN50mm below the high school pressure check valve, should choose vertical lift check valve and straight-through type lift check valve;
18, For DN50mm below the low pressure check valve, should choose butterfly check valve, vertical lift check valve and diaphragm type check valve;
19, DN is greater than 50mm, less than 600mm high pressure check valve, should choose swing check valve;
20, DN is greater than 200mm, less than 1200mm in the low pressure check valve, should choose no wear ball check valve;
21, For DN greater than 50mm, less than 2000mm of low pressure check valve, should choose butterfly check valve and diaphragm type check valve;
22, For the water impact is small or no water hit when the pipeline is closed, it is appropriate to choose slow closed swing check valve and slow closed butterfly check valve.