Created on:2021-05-08 10:52

Scope of inspection and maintenance for hydraulic pump and motor

Scope of inspection and maintenance for hydraulic pump and motor

② The practice shows that up to 80% of the failures and damages are caused by improper selection of oil, pollution and insufficient maintenance. In particular, many hydraulic equipment are exposed to wind, sun, rain and snow all year round, and are greatly affected by natural conditions. In order to reduce the number of failures and eliminate hidden troubles, and give full play to its efficiency, it is necessary to timely understand and master the operation status of hydraulic pump, hydraulic motor and the whole system. The best way to prevent failure is to strengthen the inspection of the main engine, hydraulic components and the whole system.

The inspection and maintenance of hydraulic pump and motor is an important part of the whole hydraulic system. However, due to the variety of hydraulic equipment, hydraulic pump and motor work place, load and environmental conditions and use requirements are different, so we can only briefly introduce the inspection and maintenance points from the system point of view.

The inspection and maintenance items and periodic table of the hydraulic system of the machine manufacturer are shown in the table below. The scope of inspection and maintenance includes oil, filter, accumulator, adjustment, cooler and others. The description of each inspection and maintenance item is as follows.


Inspection and maintenance items and periodic table of hydraulic system


a. Oil inspection includes liquid level, oil temperature, oil sample, oil change, etc.

Always check the liquid level and replenish the oil in time. When the volume of oil in the system is reduced below the lowest liquid level, it may cause temperature rise, insoluble air accumulation, pump failure due to cavitation, etc.

The working temperature of oil depends on many factors, usually between 40 ℃ and 90 ℃. For mineral oil, the recommended maximum temperature is 60 ℃. Because higher temperature will accelerate the aging of oil and shorten the life of seals and hoses. The oil temperature in the tank must be continuously monitored. A gradual increase in oil temperature indicates possible contamination or gum formation, or wear of seals or metal parts. The sudden rise of oil temperature is an alarm signal, which should be stopped immediately for inspection.

Oil aging depends on temperature, pressure, air humidity, polluted environment and other working parameters. According to the visual observation of the oil sample, the aging condition of the oil can be judged, so as to determine whether it can continue to be used.

Change oil immediately after initial commissioning. If there is no regular laboratory analysis on the oil quality, the oil should be changed every 2000-4000h or as recommended by the manufacturer. It is important that the maximum oil temperature should not exceed 70 ℃, and the filter should be cleaned or replaced in time.

b. Filter For the filter without clogging indicator, it must be replaced immediately after the initial commissioning, and then it should be replaced every 1-6 months according to the working conditions; for the filter with clogging indicator, it should be continuously monitored and checked every day when the working temperature reaches the normal value. During the temperature rise, it may alarm because of the large flow resistance, which does not indicate that the filter element is clogged.

When the liquid level of the oil tank rises or falls, the air flows in and out of the oil tank. The ventilation filter filters the air entering the tank. The cycle for checking and cleaning or replacing the filter element depends on the environmental conditions.

c. The accumulator is only allowed to be filled with nitrogen. In addition to the statutory test of the accumulator, the charging pressure of the accumulator must also be monitored. It is suggested to measure the inflation pressure several times during running in.

d. Adjust all the pressure control valve, flow control valve, pump and motor regulator, pressure relay, travel switch, thermal relay and other signal devices, which should be adjusted in the initial commissioning. At the initial stage of work, continuously monitor each set value, and then check regularly.

On the premise of meeting the load requirements, the system pressure should be set as low as possible to prevent unnecessary oil heating. In some cases, the set value can be 0.4 ~ 1.5MPa higher than the necessary static pressure to overcome the dynamic pressure drop or achieve the correct acceleration.

Systems using pressure compensated variable displacement pumps or relief valves are usually protected against overload by an additional relief valve. The opening pressure of the safety valve should be 1 ~ 3Mpa higher than the set pressure of the pump regulator or the relief valve.

e. The fouling of cooler air-cooled oil cooler should be cleaned regularly. The cleaning interval of water-cooled oil cooler depends on water quality, temperature and water quantity. It can be cleaned with nylon brush or chemical. In the tubular cooler, the zinc bar used to protect the copper tube from electrochemical corrosion should be inspected regularly and replaced in time.

f. Other inspections include leakage, contamination, damage, vibration and noise, instrument function, etc.

Always note accidental leakage, contamination, component damage (especially pipe and hose damage), instrument function and abnormal vibration and noise from hydraulic pump, hydraulic motor, coupling and base. To be vigilant and pay close attention to the details can early detect the signs of failure and prevent major equipment and personal accidents, especially when it is put into operation.

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