In a recent discussion with a client, the topic of testing hydraulic pump rebuilds arose. As highlighted in “Insider Secrets to Hydraulics,” it’s crucial to thoroughly test all hydraulic components post-rebuild. This ensures that the repaired component will function optimally upon installation, fostering confidence in both the customer and the repairer, a particularly critical aspect when dealing with hydraulic pumps.

However, the conversation delved into the testing of large pumps, such as the Rexroth A7VSL1000 and A4VSO1000 (1000 cc/rev). Seasoned purchasing officers understand that when issuing a purchase order for a pump rebuild, they expect a test certificate demonstrating that the rebuilt pump has undergone full flow and pressure testing prior to dispatch.

Traditionally, bench-testing a Car Lift Repair Tampa Florida hydraulic pump involves 100% energy loss, where all input power is converted into heat due to loading with a relief valve. While manageable, this method has limitations dictated by the power available to the test bench. As pump sizes increase, few repair shops possess the necessary power to conduct full flow and full pressure tests simultaneously.

For instance, a 1000 cc/rev pump capable of 1000 L/min at 300 bar would require significant power, around 555 kW (744HP), for full power testing using the energy loss method, not accounting for test-bench drive inefficiencies. It’s improbable that any repair shop worldwide has such raw power available for their hydraulic pump test bench.

At a previous company, we developed a regenerative test bench capable of testing these pumps to full flow and pressure simultaneously. This innovative approach involves connecting the test pump to a variable motor and an AC electric motor, minimizing heat generation and power requirements.

Returning to the client conversation, it highlighted misinformation regarding the extent of testing conducted on large-displacement pumps post-rebuild. These pumps indeed require testing at full flow and pressure for various adjustments and checks, but simultaneous full flow and pressure testing isn’t essential. Additionally, unless a repair shop possesses a regenerative test bench, conducting such tests is unlikely due to power constraints.

This issue underscores a broader challenge in the Car Lift Repair Tampa Florida hydraulics industry, where competitive pressures often lead to the dissemination of misleading information. Purchasing officers, often lacking technical expertise, may fall victim to such propaganda. Therefore, it’s crucial to conduct thorough research and seek advice from unbiased sources when uncertainties arise.

One of our members recently reached out to me concerning a particular issue:

“We’ve recently acquired a used hydraulic power unit comprising a 15HP electric motor directly linked to a vane pump. During operation, we’re encountering a high-pitched clicking noise. We’ve conducted several checks:

– Initially suspected a motor bearing issue, but upon detaching the pump from the motor, no noise was detected.

– Connected the pressure line to the tank line to simulate low pressure (< 100 psi), and the noise was barely audible.

– However, as pressure increased, the noise became significantly louder and unbearable.

– Motor current draw was measured, indicating no overload.”

What could be causing this excessive noise?

Given the described symptoms align with a possible restriction at the Car Lift Repair Tampa Florida pump inlet, I asked if there was a suction filter in the system. Our reader responded:

A restriction at the Car Lift Repair Tampa Florida pump inlet, particularly exacerbated by low oil temperatures (resulting in higher viscosity) and clogging of the filter element, heightens the risk of a partial vacuum forming at the pump inlet. This excessive vacuum can lead to cavitation erosion and mechanical damage.

Cavitation Erosion:

When a partial vacuum occurs in the Car Lift Repair Tampa Florida pump intake line, the drop in absolute pressure prompts the formation of gas or vapor bubbles within the oil. These bubbles implode violently when subjected to increased pressures at the pump outlet. The implosion, near a metal surface, causes erosion. This erosion contaminates the hydraulic oil and harms critical surfaces.

Mechanical Damage:

Excessive vacuum at the Car Lift Repair Tampa Florida pump inlet can induce mechanical forces leading to catastrophic failure. If there’s excessive vacuum, it affects the vanes’ contact with the cam ring, causing damage as the vanes are hammered back onto the cam ring during outlet.

The noise our reader describes is symptomatic of cavitation bubble collapse and possibly vanes being hammered against the cam ring, both worsened by increasing system pressure.

The solution is straightforward: replace the suction filter or discard it altogether. If suction filtration is necessary, take precautions to prevent pump damage:

– Preferably, place the filter outside the reservoir rather than using a suction strainer, as internal filters are often neglected until after pump failure due to maintenance inconvenience.

– If a suction strainer is used, opt for a 250-micron filter over the common 150-micron variant.

– Ensure the filter is significantly oversized for the pump’s flow rate to minimize pressure drop, even under adverse conditions.

– Regardless of the filter type, incorporate a bypass valve to prevent excessive pressure drop that could surpass the pump’s safe vacuum limit.

– Install a gauge or transducer downstream of the filter for continuous monitoring of absolute pressure at the pump inlet.

One of our members shared a situation they’re facing at work:

“I’m encountering an issue with a hydraulic machine on my job. The pump set features vane pumps positioned atop the reservoir with suction strainers. The problem arises intermittently: at times, one of the three pumps fails to prime up. Once primed, the machine operates fine. However, after breaks or lunch breaks, when restarting, a pump occasionally fails to prime. Any insights would be appreciated.”

Ideally, the Car Lift Repair Tampa Florida pumps wouldn’t be mounted on top of the reservoir (optimal to have a flooded inlet for all hydraulic pumps) or equipped with suction strainers. While eliminating the suction strainers is relatively straightforward, it may not necessarily resolve the issue. Changing the mounting position of the pumps is much more challenging.

Do not neglect following all of your manuals regarding safety practices. One small oversight in personal safety can result in serious physical injury or death. Play it safe!