Failure causes and test methods of the hottest pre

The failure reason and test method of pressure valve

in the hydraulic system of agricultural machinery, pressure valve is a kind of component that is widely used. The sudden failure of pressure valve will directly affect the normal operation of mechanical equipment. This paper divides the failure reason of pressure valve and introduces the test method of pressure valve with examples

1. Common causes of failure

(1) the hydraulic valve core and valve body are constantly worn during use, which changes the size, shape and surface quality of parts

(2) the balance spring, valve core and valve seat in the hydraulic valve work under long-term variable load, resulting in fatigue and cracks, resulting in spring, fracture or peeling and damage of the sealing surface of the valve seat

(3) residual stress during the processing of hydraulic valve parts and 4. Change the external load stress during the use of the experimental machine, which exceeds the yield strength of the part material, and the part deforms

(4) the hydraulic oil is mixed with too much water or acidic substances. After a long time of use, the parts in the hydraulic valve will be corroded and lose their due accuracy

(5) the radial force of the liquid between the valve core and the valve sleeve is unbalanced, which finally makes the valve core press against the inner wall surface of the valve sleeve, resulting in clamping

(6) when the hydraulic valve is manufactured or repaired, it does not meet the specified technical requirements; Or the parts are not well kept, rusted, mixed with dirt, etc

press vertically into the sample surface under the action of experimental force 2 Examples of test methods

pressure valves include overflow valves, pressure reducing valves and sequence valves. This paper takes overflow 3 and pressure union height as the minimum value valve as an example to illustrate the test items and methods of pressure valves. The test of pressure valve can be carried out on a special test bench or a comprehensive test bench

(1) pressure regulation range and pressure stability test. Adjust the adjusting handwheel of the tested valve from fully open to fully closed, and then to fully open. From the pressure gauge, we can see the pressure rise and serious damage to the lens decline and the pressure regulation range. The pointer of the pressure gauge shall rise and fall steadily, and the pressure regulating range shall meet the specified pressure regulating range. At the highest pressure, the pressure fluctuation value shall not exceed the specified value

(2) internal leakage test. Adjust the adjusting handwheel of the tested valve to the fully closed position, adjust the overflow safety valve to the maximum pressure of the tested valve, and then adjust the adjusting handwheel of the tested valve to make the overflow port of the tested valve measure the internal leakage

(3) unloading pressure test. Connect the remote control port of the overflow valve to the oil tank, make the tested valve pass the flow inspection, and measure the inlet and outlet pressure of the overflow valve. The difference is the unloading pressure of the tested valve

(4) pressure loss test. Adjust the adjusting handwheel of the tested valve until it is completely loosened, and make the tested valve pass the inspection flow. The pressure at the inlet and outlet of the overflow valve is measured by the pressure gauge, and the difference is the pressure loss of the tested valve

(5) opening and closing characteristic test. Close the overflow safety valve, adjust the tested valve to the maximum pressure, adjust the overflow safety valve to gradually depressurize the system, and measure the overflow of the tested valve when it is reduced to the closing pressure of the tested valve. Adjust the overflow safety valve, start from the point that the tested valve does not overflow, and gradually increase the pressure of the system. When it rises to the opening pressure of the tested valve, measure the overflow of the tested valve