The pump is the "heart" of all hydraulic systems. So any time there is a problem with the hydraulic system, the problem is often blamed on the pump.
In fact, as far as the cause of pump damage is concerned, it is rare to see a phenomenon caused by a defective pump itself. More correctly, when the pump's working condition is deteriorating, it shows that the hydraulic system has hidden a symptom of other problems.
Pump damage in ninety to ninety-five percent can be roughly summarized as the following kinds of reasons: a. Air mixing (A)
Ⅰ, air mixing (Aeration)
Air mixing refers to a bubble in the system of the hydraulic fluid dispersed phenomenon. When the oil system has been compressed air bubbles face the pump outlet pressure, it will occur this rupture effect. This rupture effect will cause the pressure side plate, wear side plate, and other metal surfaces near the rupture point inside the pump to peel off and cause extreme heat in the area.
The phenomenon of air mixing, the pump will produce a loud noise of thunder and pop. The pitch of this noise will rise with the pressure, and excessive air mixing phenomenon will lead to hydraulic fluid emulsification (due to a large amount of water vapor in the air). Moreover, the air compression phenomenon in the hydraulic fluid causes problems such as poor movement of hydraulic components in each department.
The possible ways to cause air to mix into the pump are.
1, bad shaft seal.
2, the oil tank to the pump inlet port of the joint leakage.
3, the oil level is too low or return to the oil tank is installed on the oil surface, resulting in air bubbles in the hydraulic oil in the tank, which is sucked again by the pump when the air bubbles have not been eliminated.
Ⅱ, cavitation (Cavitation)
Cavitation refers to a local cavitation phenomenon that occurs when the pressure is reduced to below the saturation vapor pressure in the fluid of the hydraulic fluid. More simply put, when the hydraulic fluid is not completely filled with the space that should be occupied, that is, there is a vacuum in the oil circuit, it will cause this cavitation phenomenon.
The noise caused by cavitation is roughly similar to the noise caused by the air mixing phenomenon. The factors that cause cavitation are.
1, the pump and electric motor matching problems, resulting in pump speed being too high.
2, too long pump suction line, or for the suction port is restricted.
3、The viscosity of hydraulic oil is too high.
4、Is the exhaust port on the oil tank blocked?
5 Check the filter of the pump suction port.
The presence of any foreign matter in the hydraulic system circuit, for the hydraulic components and its circuit efficiency, will have a negative impact. The contamination may be solid, liquid, or gas.
Most of the foreign matter contamination will cause frictional movement between the workpiece and the close clearance of the workpiece, which will lead to accelerated wear and cracking of the workpiece.
Pollution sources in the oil circuit can be roughly divided into.
1、Cast cylinder, oil circuit block, inside of oil tank, pipeline joints, etc.
2、Oil seal or O-ring embrittlement fracture.
3、Hydraulic oil deteriorates under high temperatures for a long time and produces oil contamination.
4、Pump stripping material on the metal surface due to air mixing or cavitation.
Ⅳ. Excessive heat
Excessive heat is a thermal phenomenon that causes fluid viscosity change because the specified upper temperature is exceeded. Excessive heat will cause accelerated oxidation of hydraulic fluid and make hydraulic fluid viscosity deterioration, and cause a chain reaction, so the real root cause of excessive heat must be eliminated so that the effective correction of this problem.
The causes of overheating are
1、Overload operation, overpressure use.
2, air mixing and cavitation caused by the phenomenon.
3, oil pollution caused by.
V. Over-pressure (Over-pressuri\zation)
Over-pressure means that the operating pressure is greater than the pressure designed by the pump. Over-pressure will make the internal workpiece of the pump suffer great force and cause early damage to the internal workpiece.
All of the above-mentioned causes will leave their specific signs of damage. It is important to identify and understand the information brought by these signs. In this way, the real cause of damage to the pump can be corrected before another pump is damaged.