Engineering hydraulic cylinder cavitation reason and hydraulic cylinder cavitation prevention measures
You can often see some honeycomb-shaped cavities on the inner wall of the cylinder, the piston or the piston rod of the hydraulic cylinder, which are all caused by cavitation.
Cavitation will cause the details of the fit between the cylinder barrel and the piston rod to become rough, and the hydraulic cylinder will leak internally, reducing the speed. When cavitation and other forms of corrosion are jointly sensed, the corrosion rate of the main parts of the hydraulic cylinder will be accelerated, which will seriously affect the normal use of construction machinery.
Since cavitation will seriously affect the normal use of construction machinery, we should find the real cause of cavitation.
One, the reason for affecting cavitation is that when the hydraulic cylinder parts and hydraulic oil move relative to each other, the gas in the hydraulic oil is ablated to form bubbles. These bubbles rupture after flowing into the low-pressure zone. The ultra-low temperature and low-pressure micro-jet and the attack force are repeatedly sensed on the surface of the hydraulic cylinder parts, causing the parts to cavitation. The conditions of hydraulic cylinder cavitation have a certain relationship with hydraulic system layout, hydraulic cylinder parts materials, hydraulic oil quality, construction and maintenance.
1. In the structure of the hydraulic system, if the passages of the hydraulic system’s pipelines, control valves and other components are too narrow and too many elbows, the temperature of the hydraulic oil will rise, the attack force will increase, and bubbles will easily be generated in the hydraulic oil, which will cause Cavitation of hydraulic cylinder.
2. The hydraulic cylinder parts have better strength, toughness and corrosion resistance, so their cavitation resistance is better; otherwise, cavitation is prone to occur. In addition, the uniformity of the material structure has a greater impact on cavitation. The more uneven the material structure, the weaker the strength and the low corrosion resistance will easily cause cavitation.
3. The quality of hydraulic oil is also an important factor in whether the hydraulic cylinder produces cavitation. In the mission, the hydraulic oil cannot prevent the valve and pipeline from impacting. If the hydraulic oil has poor foam resistance, it is easy to produce foam, which will cause cavitation in the hydraulic cylinder and other parts. If the frequency of hydraulic oil pressure changes is too fast or too high, it will also promote the formation of air bubbles and accelerate the rate of air bubbles. For example, due to the relatively high frequency of pressure changes at the oil inlet and return ports of a hydraulic cylinder, the degree of cavitation is relatively higher than other parts.
4. The quality of construction, assembly and maintenance of hydraulic cylinders has an impact on cavitation. If the hydraulic system is not fully vented during assembly or maintenance, it will result in the presence of gas in the system. Under low temperature and low pressure sensing, the hydraulic cylinder will produce cavitation.
Two, measures to prevent cavitation are as follows:
1. Choose high-quality qualified and suitable hydraulic oil, which can effectively prevent the hydraulic oil from generating bubbles during use. The selection of hydraulic oil should be based on the relevant technical requirements and the temperature in the area, and should be filled according to the oil dipstick standard.
The connected hydraulic system must be kept clean. Check the oil quality, oil level and oil color of the hydraulic oil frequently. If foam or milky white is found in the hydraulic oil, it means that air has been mixed in the hydraulic oil. Replace with new hydraulic oil in time. If operating high water-based hydraulic oil, a high-mounted hydraulic oil tank should be configured to increase the pressure at the oil inlet of the hydraulic pump and effectively prevent the hydraulic cylinder from cavitation.
2. The selection of appropriate hydraulic oil additives can effectively inhibit the hydraulic oil from being dirty or hydrated, prevent the occurrence of foam, stabilize the quality of the hydraulic oil, and make the hydraulic oil run through the normal function of the connection for a long time.
3. To prevent the oil temperature from being too high, a reasonable configuration of the hydraulic oil heat dissipation device can prevent the hydraulic oil temperature from being too high. If the oil temperature is too high during use, the reason should be found and eliminated in time to eliminate the premise of air bubbles in the hydraulic oil. When using the hydraulic system, do not frequently increase the throttle, and strive to operate smoothly to reduce the impact of hydraulic oil on hydraulic components.
4. Assemble or repair the hydraulic cylinder correctly. When assembling or repairing important parts such as the cylinder body and piston rod of the hydraulic cylinder, the assembly should be carried out according to the lower limit of the assembly dimensional tolerance, which may well prevent the occurrence of cavitation. If the hydraulic cylinder parts have been cavitation, only metallographic sandpaper can be used to polish away the pitting and surface dirt caused by cavitation, and hard fine sandpaper can not be used for polishing.
After the hydraulic cylinder is repaired, it should be operated for a period of time under no-load and stable conditions so that the hydraulic oil can be fully recycled. If air is mixed in the hydraulic system, manual exhaust can be performed by slowly loosening the nut of the oil inlet pipe or return pipe of the hydraulic cylinder, and tighten the nut when the air bubble is completely overhead.