Stopping Hydraulic Pump Cavitation in its Tracks

The second most prevalent cause of hydraulic pump failure, following closely behind contamination, is a phenomenon known as cavitation. Cavitation represents a condition that can severely compromise not just your hydraulic pump but your entire hydraulic system’s overall health and efficiency. To grasp the importance of combating cavitation, it’s essential to understand what it is, recognize its symptoms, and implement effective prevention measures.

Your Comprehensive Guide to Preventing, and Resolving this Costly Problem

Defining Cavitation

Cavitation, a significant concern in hydraulic systems, is a complex process rooted in fluid dynamics. It begins with generating excessive vacuum conditions at the hydraulic pump’s inlet, referred to as the supply side. This critical juncture in the hydraulic system serves as the initial stage of a phenomenon that can have far-reaching consequences.

In simpler terms, cavitation is akin to the formation and subsequent rapid collapse of vapor bubbles within the hydraulic pump. These bubbles come into existence due to elevated vacuum levels within the system. More often than not, the liquid involved is hydraulic oil, a fundamental component of hydraulic systems.

The conditions for cavitation are set when the vacuum levels within the pump’s inlet reach a point where they cause the hydraulic oil to vaporize. This vaporization, akin to transforming a liquid into a gas, initiates the formation of these minuscule vapor bubbles within the hydraulic fluid. This stage might appear deceptively benign, but it begins a cascade of events that can severely compromise the pump and the entire hydraulic system’s functionality.

These newly formed vapor bubbles, now present within the hydraulic oil, embark on a turbulent journey. They are transported from the pump’s inlet, where they originated due to the vacuum conditions, to the discharge or pressure side of the pump. It’s at this crucial juncture that the havoc of cavitation truly unfolds.

These vapor bubbles encounter significantly higher pressure levels upon reaching the discharge side. When coupled with the inherent instability of vapor bubbles, this sharp contrast in pressure results in their rapid and violent collapse. The collapse of these bubbles generates an intense implosion akin to a tiny but powerful explosion within the hydraulic fluid.

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Causes of Cavitation

Cavitation in hydraulic systems is a multifaceted problem, influenced by various factors that collectively challenge the system’s health. Poor plumbing stands out as the primary and often leading cause of cavitation, but it’s not alone in its contribution to this troublesome phenomenon. Let’s delve into these factors and understand how they can collectively spell trouble for hydraulic systems:

1. Flow Restrictions

Flow restrictions are significant players in the cavitation drama. These restrictions can arise from various sources, including the buildup of contaminants in the filter. When the strainer becomes clogged or dirty, it obstructs the smooth flow of hydraulic oil, exacerbating the conditions conducive to cavitation.

2. Hose Length and Valves

Inappropriate hose lengths or partially open valves can also lead to flow restrictions. Using hoses that are either too long or too short for the intended application can disrupt the hydraulic flow, and partially open valves create bottlenecks that impede the smooth movement of fluid. Both scenarios add to the risk of cavitation.

3. High Oil Viscosity

High oil viscosity is another contributing factor to cavitation. In some cases, hydraulic oil that is excessively viscous or thick can hinder its ability to flow smoothly to the pump. To mitigate this issue, selecting hydraulic oil with an appropriate viscosity that matches the environmental conditions and the application in which the hydraulic pump operates is essential.

4. Climate and Application Considerations

The viscosity of hydraulic oil plays a crucial role in preventing cavitation. Choosing hydraulic oil that aligns with the specific climate and application is vital. For instance, colder climates might necessitate oil with lower viscosity to ensure it flows adequately, while warmer environments may benefit from oil with higher viscosity.

Proper sizing components, regular maintenance to keep filters and strainers clean, and selecting the right hydraulic oil can help reduce the risk of cavitation and its associated damage.

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Results of Cavitation

Cavitation’s detrimental effects extend beyond just the hydraulic pump. The most significant damage occurs due to the excessive heat generated when vapor bubbles collapse at the pump’s outlet or discharge side. This collapse causes violent implosions, drawing in surrounding debris or material. 

The temperature at the point of implosion can exceed a staggering 5,000 degrees Fahrenheit. Cavitation can lead to reduced lubrication, increased friction, and wear over time, all of which can compromise the longevity and performance of your hydraulic system.

Recognizing Cavitation

Detecting cavitation is crucial for addressing it promptly. Typically, cavitation is accompanied by distinct sounds that can be classified as a “whining” or “rattling” noise. The severity of the noise may vary, but hearing either sound should prompt an investigation. 

To isolate the pump as the source, you can remove it from the power take-off (PTO) and run the PTO without the pump. If the noise disappears, your hydraulic pump is likely the culprit. Physical evidence is another indicator of cavitation. 

During routine maintenance, inspecting and replacing hydraulic oil filter elements is crucial. The presence of metallic debris during this process can signify cavitation. Checking the filter’s condition is an effective way to assess your hydraulic system’s health.

Preventing Cavitation

Preventing cavitation hinges on several key measures. Ensuring a straight and vertical path from the reservoir to the pump is essential, as this minimizes the chances of vapor bubble formation. A full-flow ball valve with the same inside diameter as the supply hose helps maintain an unobstructed flow. 

Adequate supply flow is ensured by removing obstructions in the reservoir’s strainer and checking the inlet hose for any restrictions. Promoting laminar flow by ensuring the supply hose’s length is at least ten times its diameter can reduce noise and turbulence at the pump inlet. Opting for a flared, flange-style fitting at the pump inlet can reduce pump noise compared to other fittings.

Selecting the proper viscosity of hydraulic fluid is paramount, with too dense oil impeding flow to the pump. Choosing the ideal fluid viscosity for your specific climate and application is essential. Regular maintenance, monitoring, and proactive measures can prevent cavitation, ensuring efficient hydraulic system operation throughout your pump’s lifespan. 

If cavitation is detected, identifying its root cause is crucial to prevent further damage and potential system failure.

Turn to Delta Hydraulics 

Delta Hydraulics is your trusted partner for addressing hydraulic pump cavitation issues. With over 50 years of experience in the hydraulic industry, our comprehensive services include rebuilt hydraulic pumps, custom-designed HPU solutions, repair and refurbishment services, and more. Contact us today to discuss your hydraulic pump rebuilding project and restore your equipment to peak efficiency.

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