Avoiding Devastating Cavitation Damage With the help of Rexroth proportiona

Avoiding Devastating Cavitation Damage With the help of Rexroth proportional valve

Hydraulic pump cavitation is a destructive problem. It is the likely cause of symptoms such as excessive noise and power usage, pump damage, and pump failure.

Although each of these symptoms can indicate other concerns, cavitation is one of the most problematic, as it can compromise your entire hydraulic system. It is the second leading cause of hydraulic pump failure behind hydraulic fluid contamination.

For this reason, let's look at some causes of cavitation, how to recognize that it is occurring, as well as how to prevent damage and maintain the health of hydraulic systems.

What is cavitation and what causes it?

Cavitation occurs from the formation and resulting collapse of vapors within a hydraulic pump. Excessive vacuum conditions on the inlet (supply) side of a pump create vapor bubbles within the hydraulic fluid which then move to the discharge (pressure) side, at which point they collapse. The moment of collapse is when the cavitation damage occurs.

Cavitation is especially destructive to metal surfaces, which have little elasticity. The explosive force of cavitation causes friction and wear, which eventually leads to damage and, if left untreated, will lead to pump failure.

Although the primary cause of cavitation is poor plumbing, there are many other ways this destructive force can begin.

Some of these other possible causes of cavitation in a Rexroth hydraulic valve include:

flow restrictions

High oil viscosity

clogged filters

pipe obstruction

Bad piping design

Conditions that do not meet NPSH (Net Positive Suction Head) requirements

Identification of cavitation in a hydraulic pump

Most of the time, cavitation is heard, it is identified by a recognizable sound. However, there are other visual cues that are accurate clues when a pump is experiencing cavitation.

When you are concerned that cavitation is occurring in a hydraulic pump, pay attention to:

The Sound: A hissing sound from the pump can indicate mild cavitation, while a rattling sound best described as "marbles in a can" can indicate heavy implosions.

The physical evidence: Metal debris found in the Rexroth valve oil filter during routine maintenance can indicate cavitation in a pump.

The Damage – If the pump and its components are clearly damaged, it may be the result of cavitation and the pump requires immediate inspection.

Troubleshooting and Prevention

the problem, limit the damage, or help prevent the problem altogether.

Here are some preventative and troubleshooting steps that can be taken.

Problem solving

Check filters and strainers, looking for metal debris

Determine the absolute pressure available (NPSHa) and required (NPSHr) for the suction port of the pump.

Check the viscosity of the oil and make sure it is appropriate for the application and weather conditions

Prevention

Increase the liquid level around the suction area

Increase pump suction line size to reduce turbulence

Maintain the proper oil viscosity for your components and based on the weather/environmental conditions in which the pump operates

Best practices to avoid cavitation

Continuing a regular maintenance schedule on your hydraulic systems and looking for signs of cavitation are the best preventative measures which may already include the steps above. However, there are some practices that can further protect hydraulic systems from cavitation damage.

These practices include:

Ensuring pumps have flooded suction, i.e. using a direct path from reservoir to pump to use gravity and atmospheric pressure to power the pump rather than relying on vacuum pressure to draw fluid.

Use a proper vent cap on the reservoir, or pressurized (3-5 PSI) with an air system or pressurized vent cap

Make sure any supply line shutoff valve is fully open and free of restrictions.

Inspect reservoir filter for buildup (if present)

Consider laminar flow and reduce noise and turbulence at the pump inlet by ensuring that the supply hose length is at least 10 times its diameter.

Doing the job can save your hydraulic system

Starting with knowing what cavitation is, what causes it, and distinctive ways to recognize it, end users can avoid going down the path that can lead to a compromised hydraulic system.