What is cavitation?
Cavitation is a common phenomenon in hydraulic systems, especially in hydraulic cylinders. It refers to the formation of bubbles in the hydraulic oil due to low pressure in the hydraulic cylinder, and these bubbles will burst instantly under high pressure, generating a strong impact. Cavitation can have many effects on the hydraulic system, including performance degradation, system damage, etc.
What causes cavitation in hydraulic cylinders?
Low pressure in hydraulic cylinders
One of the main causes of cavitation in hydraulic cylinders is low pressure. When the pressure of the hydraulic oil drops below the vapour pressure of the fluid, the hydraulic oil will gasify and form bubbles. These bubbles will quickly burst during the flow process, causing an impact force. Fluctuations in the pressure of the hydraulic cylinder, low pressure values or design faults can lead to the formation of low air pressure.
Too much air in hydraulic oil
Hydraulic oil contains a lot of dissolved gas or air, which is also a cause of cavitation. Air is difficult to remove from hydraulic oil. When the hydraulic system is operating, these gases will quickly expand in low pressure areas to form bubbles, thus increasing the occurrence of cavitation. Improper system design, hydraulic oil quality and maintenance can lead to excessive air in the oil.
Unstable flow
Unstable flow in the hydraulic system, especially where the pump flow is insufficient or fluctuates greatly, will result in low pressure in localised areas. System flow instability is often a catalyst for cavitation. Large fluctuations in flow can easily cause a sudden drop in pressure in some parts of the hydraulic oil, resulting in the formation of bubbles.
Incorrect selection or maintenance of hydraulic oil
Improper selection, quality and maintenance of hydraulic oil is a major cause of cavitation. If the hydraulic oil has poor anti-cavitation performance, or the oil is aged or contains impurities, it is easy to cause cavitation. In addition, too long an oil change cycle and excessive contamination can also cause cavitation.
What are the dangers of cavitation?
Physical damage
Cavitation can cause serious physical damage to several components in the hydraulic system. Firstly, when bubbles burst in the hydraulic cylinder, they will exert a large impact force on the inner wall of the hydraulic cylinder or the surface of the piston rod, causing surface erosion, wear or corrosion. This damage will directly affect the sealing and stability of the hydraulic cylinder.
Erosion of the inner wall of the hydraulic cylinder or the surface of the piston rod
The bursting of the bubbles will create an effect similar to a small explosion, hitting the inner wall of the hydraulic cylinder or the surface of the piston rod, causing surface erosion. Over time, the area of erosion will increase, which can lead to poor sealing of the hydraulic system, affecting the operating efficiency of the entire system.
Increased wear on valves and seals
Cavitation can also damage valves and seals in the hydraulic system. When bubbles burst, they create strong shock waves, wear seals, cause leaks and then affect the stability of the system.
Reduced system performance
Cavitation will significantly reduce the performance of the hydraulic system. Firstly, the movement of the system becomes unstable and the working efficiency is reduced. Secondly, cavitation will cause the temperature of the hydraulic oil to rise and the pressure fluctuation of the system to increase, further affecting the working efficiency and stability of the equipment.
Increased noise and temperature
Cavitation is usually accompanied by increased noise. When bubbles burst, a sound similar to an explosion is emitted. At the same time, cavitation causes the oil temperature to rise, increasing the cooling load and reducing the efficiency of the system.
Increased operating costs
Cavitation not only affects the performance of the hydraulic system, it also increases maintenance costs. Because cavitation can damage components such as hydraulic cylinders, pumps and valves, the system requires more frequent maintenance and parts replacement, increasing the company’s operating costs.
Increase maintenance frequency and shorten equipment life
Physical damage and performance degradation caused by cavitation can shorten equipment life. To ensure normal operation of the hydraulic system, the frequency of maintenance and replacement of parts will also increase.
How can cavitation be prevented in hydraulic cylinders?
Optimise the design of the hydraulic system
Optimising the design of the hydraulic system is the first step in preventing cavitation. By properly designing the hydraulic cylinder and piping to ensure that there is no sudden pressure drop, cavitation can be effectively prevented.
Ensure there is no sudden pressure drop when designing the hydraulic cylinder and piping
In the hydraulic system, it is important to avoid sudden pressure drops in the hydraulic cylinder and piping. The design must ensure that there is no excessive pressure fluctuation as the oil flows, to avoid low air pressure in local areas and the formation of bubbles.
Select the right hydraulic pump and control valve to avoid drastic flow fluctuations
Proper selection of hydraulic pumps and control valves and ensuring their stable operating conditions are important measures to avoid cavitation. The flow of the pump should be kept stable and the control valve should be properly adjusted to avoid sudden flow fluctuations.
Use high quality hydraulic oil
The selection of high quality hydraulic oil is essential to prevent cavitation. High quality hydraulic oil has better anti-cavitation performance and stronger lubricating effect.
Select hydraulic oil with good anti-cavitation performance and make sure the oil is clean.
High quality hydraulic oil has good anti-cavitation ability and can effectively reduce the formation of bubbles. Regularly checking the cleanliness of the oil and keeping the oil clean can effectively prevent cavitation problems.
Replace hydraulic oil regularly to prevent oil ageing
Regularly changing the hydraulic oil to prevent oil deterioration due to long-term use is an important means of preventing cavitation. Aged hydraulic oil will lose its ability to resist cavitation, resulting in increased cavitation.
Periodic inspection and maintenance
Regular inspection and maintenance of the hydraulic system will help to detect and rectify potential cavitation problems.
Check the hydraulic ram for leaks and remove any air in good time.
Checking the hydraulic ram for leaks and removing air in time to prevent air from entering the hydraulic system is an effective way of preventing cavitation.
Keep the oil tank vent clean to prevent air from entering the hydraulic ram.
Keep the oil tank vent clean to prevent external air from entering the hydraulic ram, which is an effective way of preventing the formation of bubbles in the hydraulic system.
Correct operation
Incorrect operation can cause cavitation in the hydraulic system, so take care to avoid overloading and emergency stops during operation.
Avoid overloading and frequent emergency stops and starts
Avoid operating the hydraulic cylinder under overload conditions and frequent emergency stops and starts, as this will greatly reduce the likelihood of cavitation.
Ensure that the pressure and flow of the hydraulic cylinder are within the design range during operation.
Ensure that the pressure and flow of the hydraulic cylinder are always within the design range during operation to avoid cavitation.
