Agricultural machinery, hydraulic system, the pressure valve is used more often in a class of components, the pressure valve a sudden failure will directly affect the normal operation of machinery and equipment, this paper points the pressure valve failure reasons and examples of the pressure valve testing methods.
1. The common cause of failure
(1) hydraulic valve core and valve body when using the continuous generation of wear and tear, allowing part size, shape and surface quality changes.
(2) the balance of hydraulic valve springs, valve core and valve seat, in the long run to work under variable loads, resulting in fatigue and crack, resulting in spring, break, or the valve seat sealing surface, peeling off, damaged.
(3) hydraulic valve parts processing residues and use of residual stress in the external load stress, the material yield strength of more than spare parts, spare parts deformation.
(4) hydraulic oil mixed with water or too much acid, using a longer time, the corrosion of hydraulic valve parts to lose their accuracy.
(5) with the valve spool suites liquid radial force imbalance, ultimately spool valve comprising a wall pressure to the clamping phenomenon occurs.
(6) in the hydraulic valve manufacture or repair, did not meet the technical requirements provided; or part lack of good care, rust, mixed with dirt and so on.
2. For example, test methods
Pressure valves including relief valves, pressure reducing valve and sequence valve, this paper valve pressure relief valve as an example shows the test items and testing methods. Pressure valve test can be conducted in a dedicated test rig can also be carried out in an integrated test bed.
(1) the scope and the pressure regulator stability test. Regulating valves were tested hand wheel adjustment, from fully open to fully closed, and then to fully open from the pressure gauge shows the pressure rise and fall as well as voltage range. Pressure gauge pointer should be a smooth rise and fall voltage range should meet the required voltage range at the highest pressure, pressure fluctuation is not to exceed the specified value.
(2) within the leakage test. Regulating valve adjustment by hand wheel to full closed position, adjustable overflow valve as being the maximum pressure test valve, and then try regulating valve hand wheel adjustment, so that subjects were measured within the overflow valve leakage.
(3) The unloading stress testing. The relief valve remote control port access fuel tank, so that valves were tested by examining the flow, measuring the pressure relief valve in and out of the oil port, the difference shall be unloading valve pressure test.
(4) pressure loss testing. Regulating valve adjustment were tested hand wheel to full release and make valves were tested by examining the flow, measured by the pressure gauge the pressure relief valve in and out of the oil port, the difference shall be test valve pressure loss.
(5) open and close feature tests. Close overflow safety valve, regulating valve were tested to the maximum pressure, regulate blood pressure overflow valve make the system gradually, when the valve is closed down by the pressure test subjects were measured at excess flow valves. Adjustable overflow safety valve, pilot valve has been no overflow from the beginning to make the system a gradual step-up, when the pilot valve has been opened up to stress, measured by the excess flow valve. ball valve Trunnion Mounted Ball Valve Floating Ball Valve Top Entry Ball Valve Three way ball valve V Type Ball Valve
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