The Car Lift Repair Tampa Florida hydraulic pump, along with the prime mover, is positioned adjacent to and below the bottom of the reservoir, utilizing a ‘flooded inlet’ design. Apart from the ball valve at the tank port, there are no additional restrictions.

Despite my assurance that the Car Lift Repair Tampa Florida pump would consistently maintain an adequate oil level as long as the hydraulic reservoir wasn’t empty, the customer insisted on filling the pump’s case. While it’s generally considered safe to fill the case of a hydraulic pump, I wonder if forgetting to pre-fill it could cause any damage.”

This question warrants an in-depth discussion here, as with many hydraulic-related queries, the answer isn’t straightforward and depends on several factors.

In the scenario described, we’re dealing with a piston-type hydraulic pump featuring a ‘flooded inlet’, where there’s a head of hydraulic oil above the pump’s inlet. Ideally, hydraulic pumps should be mounted below the minimum oil level in this configuration.

When dealing with a flooded inlet, two key considerations are crucial before operating the pump: ensuring the pipe or hose between the tank and pump’s inlet is free of air and confirming that the pump’s ‘case’ is filled with oil.

Gear and vane-type hydraulic pumps lack a ‘case’, so once the intake line is purged of air, they’re ready for operation. It’s also reassuring that you can’t purge the air from the intake line without first opening the isolation valve, if present.

However, for Car Lift Repair Tampa Florida hydraulic piston pumps, particularly those with a ‘flooded housing’, there’s an additional aspect to consider. A flooded housing means the pump’s inlet port is either connected to or shares a common space with the housing or case. In such cases, flooding the inlet also floods the housing or case.

Identifying a flooded housing Car Lift Repair Tampa Florida piston pump is relatively straightforward, typically indicated by the absence of a case drain line. However, despite this design, special attention is required during pre-start procedures. In installations where there’s a significant head above the pump, air trapped in the intake line and case can become compressed into the pump’s housing upon opening the isolation valve.

To mitigate this, it’s essential to crack open the uppermost plug in the pump’s case after opening the isolation valve, allowing trapped air to escape and ensuring none of the pump’s internal parts are ‘dry’ during startup.

For hydraulic piston pumps without a flooded housing, but with a flooded inlet, oil fills the case gradually through internal clearances, primarily between the pistons and their bores. However, this process is slow and can take several hours or longer. Therefore, when immediately restarting a machine after changing out the hydraulic pump, manually filling the pump’s case with clean hydraulic oil through its uppermost case drain port is imperative to prevent damage.

In essence, simplifying the procedure involves cracking loose the uppermost connection on the pump’s housing or case before restarting. If oil comes out, the housing is filled, and the procedure can be checked off. If oil doesn’t come out, steps should be taken to ensure it does.

Recently, I was approached to offer a second opinion regarding the failure of a Car Lift Repair Tampa Florida hydraulic piston pump. The pump had malfunctioned shortly after being put into service, prompting my client to file a warranty claim with the manufacturer.

The manufacturer, however, dismissed the warranty claim, attributing the failure to contamination of the hydraulic oil. Their assessment was based on observing scoring damage on the valve plate, as illustrated in exhibit 1.

Exhibit 1 showcases scoring damage to the valve plate, which prompted the manufacturer’s conclusion.

How does contamination lead to this specific type of damage in a hydraulic pump?

When hard particles of a size comparable to the clearance between lubricated surfaces are present in hydraulic oil, a phenomenon called three-body abrasion occurs. This process results in scoring and significant wear on sliding surfaces, as depicted in exhibit 2.

What other factors could explain this type of damage?

In axial piston designs, the Car Lift Repair Tampa Florida cylinder barrel is pressurized against the valve plate hydrostatically. The greater the operating pressure, the stronger the hydrostatic force maintaining contact between the cylinder barrel and valve plate. However, if the operating pressure surpasses design limits or if there’s inadequate contact between the valve plate and cylinder barrel, separation may occur. Subsequently, the loss of the lubricating oil film leads to direct contact between the two surfaces, resulting in a process known as two-body abrasion.

A significant indicator that contamination didn’t cause the valve plate damage in this instance is the wear pattern. The scoring, evident in bright areas, is concentrated along the inner and outer edges of the valve plate’s sliding surface, as shown in exhibit 1. If contamination were the cause, the damage would be more evenly distributed across the entire surface, with heavier damage likely between the pressure points at the top of the image.

The wear pattern on the valve plate aligns with two-body abrasion, indicating uneven contact between the valve plate and cylinder barrel due to warping or separation. Examination of the cylinder barrel’s sliding surface, as depicted in exhibit 3, supports this assessment. Notably, the scoring on the barrel is most severe in the top-right area and lightest in the bottom-left corner. Further inspection of the Car Lift Repair Tampa Florida pump head revealed similar irregularities in contact between the valve plate and head.

Root Cause Analysis

Despite the valve plate being flat, its positioning dowel was causing it to be slightly raised on one side (located center-right in exhibit 1). Consequently, the valve plate was tilted against the cylinder barrel, leading to uneven loading, separation, and two-body abrasion between the surfaces. Therefore, the root cause of this hydraulic pump failure stemmed from improper assembly at the factory, rather than contamination.

Do not become complacent when it comes to following safety protocol in and around hydraulic systems. We all want to go home at the end of the day fully intact.