Visual inspection method, also known as preliminary diagnosis method, is one of the most simple and convenient methods for hydraulic system fault diagnosis. This method is carried out through the six-word formula of "look, listen, touch, smell, read and ask". The visual inspection method can be carried out in the working state of the hydraulic equipment, and can be carried out in the non-working state.
1) Look. Observe the actual situation of the hydraulic system. A look at the speed, refers to the movement speed of the executing element changes and anomalies; Second, look at the pressure, refers to the pressure of each pressure monitoring point in the hydraulic system and the change of the situation: third, look at whether the oil is clean, deteriorated, whether the surface is foam, whether the liquid level is within the specified range, and whether the viscosity of the hydraulic oil is appropriate; Four look at leakage, refers to whether there is leakage in each connection; Five look at vibration, refers to the hydraulic actuator when working without jumping phenomenon; Six look at the product, according to the hydraulic equipment and the quality of the product, judge the working state of the actuator, the working pressure and flow stability of the hydraulic system.
2) Listen. Use hearing to judge whether the hydraulic system is working normally: listen to the noise, listen to whether the noise of the hydraulic pump and the hydraulic system is too large and the characteristics of the noise, whether the pressure control components such as the relief valve and the sequence valve scream; The second listen to the impact sound, refers to the workbench hydraulic cylinder reversing impact sound is too large, whether the piston has the sound of hitting the bottom of the cylinder, whether there is the impact of the end cap when the reversing valve is changing: the third listen to the abnormal sound of cavitation and trapped oil, check whether the hydraulic pump sucks air, and whether there is serious trapped oil phenomenon: the fourth listen to the knocking sound, refers to whether there is a beating sound caused by damage when the hydraulic pump is running.
3) Touch. Touch the moving parts allowed to touch by hand to understand their working status: touch the temperature rise, touch the surface of the shell of the hydraulic pump, oil tank and valve components by hand, if you feel hot for two seconds, you should check the reason for the high temperature rise; Two touch vibration, touch the vibration of moving parts and pipelines by hand, if there is high-frequency vibration should check the cause; Three touch crawling, when the table in light load and low speed movement, with the hand to touch whether there is crawling phenomenon; Touch the tightness degree, touch the tightness degree of the stop iron, micro-switch and fastening screw with your hand.
4) Smell. Use the olfactory organs to distinguish whether the oil is smelly and deteriorated, and whether the rubber parts emit special smells due to overheating.
5) Read. Check the relevant fault analysis and repair records, daily inspection and order inspection cards, shift records and maintenance records.
6) Ask. Visit the equipment operator to understand the normal operation of the equipment: ask whether the hydraulic system works normally, and whether the hydraulic pump has abnormal phenomena; Second, ask the hydraulic oil replacement time, whether the filter is clean; Three ask whether the pressure or speed regulating valve has been adjusted before the accident, and what are the abnormal phenomena; Four, ask whether the seals or hydraulic parts have been replaced before the accident; Five questions occurred before and after the accident of the hydraulic system what abnormal phenomena; Ask what faults have often occurred in the past and how to eliminate them.
Due to the differences in each person's feeling, judgment ability and practical experience, the judgment results will certainly be different, but after repeated practice, the cause of the failure is specific and will eventually be confirmed and eliminated. It should be noted that this method is more effective for engineering and technical personnel with practical experience.
