Pump cavitation is always a serious concern in the fluid power industry that leads to pump failure/breakdown. Cavitation occurs when liquid/oil contains dissolved gas and collapse during machine operation. In short, cavitation is the formation and collapse of air cavities in the liquid. The factors that affect air bubble formation are system pressure, temperature, fluid type, and external/internal leakages. This article will highlight all important facts about pump cavitation that includes its symptoms, method of prevention, and more.
What is pump cavitation? As we mentioned earlier, cavitation is the process of forming an air bubble in the hydraulic fluid. The primary reason for this issue is the partial pressure drop at the suction side of the pump caused while pumping fluid from the reservoir to the hydraulic pump. This pressure various will lead to the creation of a cavity inside the hydraulic pump. The produced air bubble will explode inside the pump causing system failure. There are numerous other causes for pump cavitation that includes the following.
- Clogged suction strainer or reservoir breather
- Excessively low/high fluid temperature
- Wrong fluid viscosity
- Excessive internal leakage
- Low liquid pressure
- Hydraulic pump related issues like too small intake line, too small pump intake drop pipe inlet area, too many bends in pump intake line, etc...
- Incorrect pump and reservoir arrangement
- Excessive pump drive-shaft RPM and swivel speed
Also, it is common for every hydraulic oil to contain 9% of dissolved air. The air will be pulled out of the oil when the pump doesn’t get sufficient oil. When this air bubble reaches a high-pressure area, it will explode or collapse.
Cavitation can be categorized based on its effect and different conditions. Based on the effects, cavitation can be of two types called inertial cavitation and non-inertial cavitation. Inertial cavitation will produce a shock wave when a bubble or void present in a liquid collapses. Whereas, non-inertial cavitation occurs when the air bubble in fluid changes its shape due to an acoustic field or some other type of energy input. Similarly, suction cavitation and discharge cavitation are two cavitation categories based on different conditions. I.e; suction cavitation occurs under high vacuum or low-pressure conditions that effects flow and discharge cavitation occurs when the pump’s discharge pressure becomes abnormally high.
The results of cavitation are excessive heat, reduced lubrication, violent implosions, friction and wear. These issues can cause serious damages to the pump leading to hydraulic system breakdown. The symptoms of cavitation are unusual sound while pump operation, presence of metal debris, and damage. When these symptoms occur, proper inspection and troubleshooting are necessary.
If pump cavitation is avoided, the pump will deliver maximum performance to a longer time period. Some tips for avoiding cavitation are mentioned below.
- Properly arrange the pump and reservoir. I.e; the pump can’t be mounted too far above/too far from the reservoir.
- Reduce the fittings and bends in the pump intake line.
- Choose properly sized pump
- Maintain sufficient fluid temperature and pressure
- Avoid using suction strainers
- Install breather filter on the reservoir