Oil pump cavitation is the formation and collapse of vapors within a hydraulic pump, occurring primarily on the inlet or supply side. This phenomenon is the product of excessive vacuum conditions created at the hydraulic pump's inlet. When a high vacuum develops, it causes the oil's pressure to drop below its vapor pressure, leading to the creation of vapor bubbles within the fluid. These bubbles are then carried by the oil flow towards the pump's discharge (pressure) side, where the pressure is much higher.
How Cavitation Happens
The process described in the reference highlights the core mechanism:
- Excessive Vacuum: An unusually low-pressure condition forms at the pump's intake.
- Vapor Formation: This low pressure causes the liquid oil to vaporize locally, forming small bubbles (cavities) within the fluid.
- Bubble Transport: These vapor bubbles travel with the oil into the pump's high-pressure discharge section.
- Bubble Collapse: As the bubbles encounter the higher pressure, they violently collapse or implode.
This rapid implosion releases significant energy in the form of micro-jets and shockwaves, which can be highly damaging to the pump's internal components over time.
Common Causes of Oil Pump Cavitation
Cavitation is typically linked to factors that restrict flow or create excessive vacuum at the pump inlet. Common causes include:
- Low Fluid Level: Insufficient oil in the reservoir can cause the pump to pull air or struggle to get enough fluid, increasing vacuum.
- Restricted Inlet Line: Clogged filters, kinked hoses, collapsed suction lines, or closed valves can impede flow.
- High Fluid Viscosity: If the oil is too thick (e.g., due to cold temperatures or using the wrong type), the pump may struggle to draw it in effectively.
- Excessive Pump Speed: Running the pump faster than intended can increase the vacuum requirement at the inlet.
- Long or Small Diameter Suction Line: Inadequate line sizing or length can create excessive pressure drop.
Recognizing the Symptoms
Cavitation often provides clear warning signs before severe damage occurs:
- Noise: A distinctive popping, cracking, or rattling sound, often described as sounding like gravel or marbles passing through the pump.
- Vibration: Increased shaking or vibration in the pump and connected components.
- Reduced Performance: Decreased flow rate or pressure output from the pump.
- Overheating: The process of bubble formation and collapse generates heat.
- Damage: Visible wear, pitting, or erosion on internal pump surfaces, especially impellers, housing, and bearings.
Preventing and Addressing Cavitation
Preventing cavitation involves ensuring adequate fluid supply and minimal restrictions at the pump's inlet. Solutions often include:
- Check Fluid Levels: Maintain the proper oil level in the reservoir.
- Use Correct Fluid: Ensure the viscosity is appropriate for the operating temperature and system requirements.
- Inspect and Clean Inlet Filter/Strainer: Regularly check for and remove blockages.
- Verify Inlet Line Integrity: Ensure the suction line is correctly sized, free of kinks, and not collapsed.
- Check Valves: Confirm that all necessary inlet valves are fully open.
- Address Temperature: Allow fluid to warm up if high viscosity from cold is an issue.
- Verify Pump Speed: Ensure the pump is operating within its specified speed range.
Addressing cavitation promptly is crucial to prevent costly damage to the pump and other system components.