Hydraulic motor device common phenomenon

The principle of gas erosion in oil pressure machines is as follows: Generally, there is air or small bubbles dissolved in the oil with a volume of 5-6% of the oil. When the flow rate of the liquid is too fast, it causes the local pressure to drop, and the air will be free from the oil to form bubbles. And, as the oil temperature rises, bubbles form cavities. When the cavity moves to the place of high pressure, it will disappear, causing the phenomenon of water crash. We call this water hammer phenomenon cavitation, cavitation has a bad effect on hydraulic machinery.
Due to the impact pressure conflict with the inner wall of the hydraulic pump, strong vibration and noise occur, when the impact force is strong or when the machine runs for a long time in the cavitation state, the machine will be damaged.
Cavitation of the pump:
If the suction filter of the hydraulic pump clogs the mesh due to the sludge, the suction resistance increases, and the inhaled oil causes the pressure to decrease, which causes the dissolved air to separate, and sends out vibration and noise.
The same phenomenon occurs at low temperatures and when the oil is too viscous.
Separation of dissolved air:
When the flow speed of the fluid in the pipe is too fast or the flow rate in the machine is severe, if the direction of flow is changed, the dissolved air will also free out and produce bubbles.
Bubbles in oil and dissolution of air:
1) The so-called bubble refers to the existence of air in a state that has not dissolved into the oil.
2) When there is no bubble in the oil, the volume elastic coefficient of the oil is about 1.6×104cm2, and if some bubbles are mixed, this value should be displayed smaller.
3) The solubility of the gas in the liquid is proportional to its air pressure. (Henry's Law)
Pressure: The amount of pressure in a complete vacuum
Mixing of air:
For various reasons, air will be mixed into the oil pressure circuit in the form of small bubbles, and this state is called ventilation. The main cause of ventilation is inhaled air. Because it is similar to the phenomenon of cavitation, it has to emit vibration and noise, and there is a small bubble formation in the oil, so it is difficult to distinguish from cavitation.
When the flow of a fluid is dramatically changed by the operation of an instrument such as a control valve, the pressure changes dramatically because the energy of the fluid's movement is converted into pressure, which is conducted at the same speed as the sound propagates through the fluid. Thus, the larger value of the transitional abnormal pressure that occurs in the oil pressure circuit is called the normal shock pressure.
The amount of pressure change is affected by the diameter of the pipe, the mixing of air, and the viscosity of the oil. The impact pressure can be seen when the work of the safety valve is delayed (about 0.1 seconds), or when the flow of oil is dramatically changed by operating the electromagnetic switching valve (about 0.08 ~ 0.12 seconds).
This phenomenon is accompanied by vibration, and the degree of mechanical vibration is more serious than that under high pressure and large flow rate, which can lead to wrong operation. In order to prevent the occurrence of this phenomenon, the shock pressure is absorbed by the energy accumulator to avoid the sudden switch of the switch valve, and the valve column of the switch valve is set up to make the pressure change slow.
When the flow of a fluid is dramatically changed by the operation of an instrument such as a control valve, the pressure changes dramatically because the energy of the fluid's movement is converted into pressure, which is conducted at the same speed as the sound propagates through the fluid. Thus, the larger value of the transitional abnormal pressure that occurs in the oil pressure circuit is called the normal shock pressure.
The amount of pressure change is affected by the diameter of the pipe, the mixing of air, and the viscosity of the oil. The impact pressure can be seen when the work of the safety valve is delayed (about 0.1 seconds), or when the flow of oil is dramatically changed by operating the electromagnetic switching valve (about 0.08 ~ 0.12 seconds).
This phenomenon is accompanied by vibration, and the degree of mechanical vibration is more serious than that under high pressure and large flow rate, which can lead to wrong operation. In order to prevent the occurrence of this phenomenon, the shock pressure is absorbed by the energy accumulator to avoid the sudden switch of the switch valve, and the valve column of the switch valve is set up to make the pressure change slow.
The flow control valve used to control the speed of the transmission device will have an instantaneous flow rate significantly higher than the set flow at the start of the transmission device, which will produce a jump when the transmission device starts to operate. The installation position of the flow regulating valve in the loop, the loop mode, the load, and the nature of the oil pressure source are the reasons for this phenomenon. This phenomenon can cause serious harm.