Precautions for using one-way valves

Pay attention to the following items when using the check valve:

1) In normal operation, the working pressure of the check valve is lower than the rated working pressure of the check valve; the flow through the check valve should be within the rated flow range allowed by the diameter, and no large pressure should be generated. loss.

2) There are various opening pressures of the check valve. The applicable opening pressure should be selected according to the system function requirements. It should be as low as possible to reduce the pressure loss. For the check valve with back pressure function, the opening pressure is high, usually Determined by the back pressure value.

3) When selecting the check valve, in addition to reasonable selection of the opening pressure according to the need, special attention should be paid to the flow rate at the time of operation should match the rated flow of the valve, because when the flow through the check valve is much smaller than the rated flow, the single The valve sometimes vibrates. The smaller the flow rate, the higher the opening pressure, and the more gas is contained in the oil, the more likely it is to generate vibration.

4) Pay attention to the direction of the inlet and outlet ports to ensure correct installation, otherwise it will affect the normal operation of the hydraulic system. In particular, check valves are used at the outlet of the pump. If installed in reverse, the pump may be damaged or the motor may be burned out. Improper installation of the check valve will result in a suction failure of the hydraulic pump with weak self-priming capability, especially for small displacement hydraulic pumps.

Therefore, the check valve should be avoided to be installed directly at the outlet of the hydraulic pump. Especially when the hydraulic pump is a high pressure vane pump, a high pressure piston pump and a screw pump, it should be avoided as much as possible. If it is a last resort, the check valve must be installed directly at the outlet of the hydraulic pump, and necessary measures should be taken to prevent the hydraulic pump from generating a suction fault.

For example, open a vent on the joint or flange connecting the hydraulic pump and the check valve. When the hydraulic pump generates an air suction fault, the exhaust screw plug can be released to directly discharge the air in the pump. If it is not enough, the oil can be filled into the pump from the exhaust port. Or make the suction port of the hydraulic pump lower than the lowest liquid level of the fuel tank, so that the oil can automatically fill the pump body by its own weight; or use a check valve with a small opening pressure.

5) The amount of leakage in the check state of the check valve is very small or even zero. However, after a period of use, leakage occurs due to wear of the seat and the spool. And sometimes the amount of leakage is very large, which will lead to the failure of the check valve. Therefore, attention should be paid to grinding and repair after wear.

6) The pressure loss of the forward free flow of the check valve is also large, generally 3 to 5 times of the opening pressure, about 0.2 to 0.4 MPa, and even as high as 0.8 MPa. Therefore, it should be fully considered when using it, carefully selected, and it can be used without it.