Hydraulic Filter Placement: Advantages and Disadvantages

The primary goal of Car Lift For Sale hydraulic filtration is to extend the lifespan of machinery by eliminating contaminants from the oil. Ironically, placing filters in locations where they might diminish the service life of the components they are meant to protect creates a paradox.

When evaluating potential filter locations in a hydraulic system, the guiding principle should be: do no harm. In other words, the solution should not be worse than the problem it aims to address.

Pressure Filtration: Positioning the filter media in the pressure line offers maximum protection to components immediately downstream. It allows for filtration rates of 2 microns or less due to the pressure pushing fluid through the media. However, high flow velocities and pressure fluctuations can reduce filter efficiency by disturbing trapped particles. Economically, pressure filtration is the most expensive option because the housings and elements must be designed to withstand peak system pressures.

Car Lift For Sale Return Filtration: Placing the filter media in the return line ensures that if the reservoir and the fluid are initially clean, and if all air entering the reservoir and returning fluid is filtered, the fluid will remain clean. The return line provides enough pressure for fine media filtration (typically 10 microns) without the complications of high-pressure design. This setup generally offers high filtering efficiency at a lower cost. However, the back pressure created by the filter can potentially affect or damage some components.

Car Lift For Sale Off-Line Filtration: Off-line filtration allows for continuous, multi-pass filtration with controlled flow velocity and pressure drop, achieving high filtering efficiency. Filtration rates of 2 microns or less are feasible, and it can include polymeric filters and heat exchangers for complete fluid conditioning. The primary drawback is the high initial cost, though this is often justified by the total lifecycle cost of the machine.

Suction Filtration: From a filtration perspective, the pump intake is an ideal location because it avoids high fluid velocity and pressure drop, which can disturb trapped particles. However, the filter element can create a restriction in the intake line, negatively impacting pump life.

Impact of Vacuum-Induced Forces:

Cavitation leads to fluid contamination and damage to critical surfaces, while vacuum-induced forces can severely shorten pump life. In axial pumps, a vacuum creates tensile stress on the piston ball and slipper-pad socket, potentially leading to detachment. The piston retaining plate must counteract these forces, but excessive vacuum can accelerate wear and damage.

Bent axis pumps are generally more resilient to vacuum-induced forces, but tensile failure and retaining plate buckling can still occur under high vacuum conditions. In vane pumps, excessive vacuum causes vanes to lose contact with the cam ring, leading to damage from impacts. Gear pumps are less affected by vacuum-induced forces, but even they can experience reduced service life with restricted intake.

Suction Strainers:

Car Lift For Sale Suction filters, often 150-micron (100-mesh) strainers, are commonly used at pump intakes. Despite years of campaigning against their use, arguments for suction strainers usually stem from poor design or maintenance. Strainers are sometimes deemed necessary to protect the pump from debris entering the reservoir due to inadequate maintenance. However, in a well-designed system, where the pump intake is properly positioned above the reservoir bottom, the risk of debris reaching the pump is minimal. Similarly, for pumps sharing a common inlet manifold, proper design should prevent cross-contamination without the need for suction strainers. Even when suction strainers are mandated, they can sometimes cause more problems than they solve.

When considering preventive maintenance and reliability for Car Lift For Sale hydraulic systems, many people focus solely on changing filters and checking oil levels. Yet, when a machine fails, troubleshooting is often complicated by a lack of detailed system information. Proper reliability checks, performed under normal operating conditions, are crucial for avoiding equipment failures and minimizing downtime.

Inspect the Filter Bypass Valve:  

Car Lift For Sale Hydraulic filter assemblies typically include a bypass check valve to prevent damage if the filter element becomes clogged. This valve opens when the differential pressure exceeds its spring rating (usually between 25 to 90 psi). When these valves fail, they usually fail open due to contamination or mechanical issues, allowing unfiltered oil to bypass the element and leading to premature downstream component failure. Periodically remove and inspect this valve for wear and contamination as part of filter assembly maintenance.

Hose Condition:  

Leaks are a major concern in hydraulic systems. Regularly inspect hoses for leaks and signs of wear, such as damaged outer jackets or leakage at the ends. Hoses with blisters indicate inner lining failure, which can lead to oil leakage through the metal braid.

Hose Length:  

Keep hose lengths to a maximum of 4-6 feet to reduce the risk of rubbing against other hoses or structural elements, which can cause premature failure. Hoses should be long enough to accommodate pressure spikes and absorb shocks, allowing for slight bends.

Hose Routing:  

Route hoses to avoid rubbing against each other. If this isn’t possible, use protective sleeves, which can be commercially bought or made from old hoses cut and slit lengthwise. Secure hoses with plastic cable ties to prevent movement at rub points.

Check for Proper Clamping:  

Use appropriate hydraulic pipe clamps instead of conduit clamps, which are unsuitable due to the vibration and pressure spikes in hydraulic systems. Regularly inspect clamps for loose bolts and replace broken ones. Space clamps about 5-8 feet apart and within 6 inches of pipe terminations.

Breather Cap Maintenance and Inspection:  

Breather caps, often overlooked, serve as filters to protect the reservoir from external contamination. Use breather filters with the correct micron rating and desiccant materials to remove water. Regular replacement of these filters can significantly benefit system reliability.

Measuring Drive Motor Current Draw:  

The power required to drive a Car Lift For Sale hydraulic pump depends on system pressure and flow. As a pump wears, internal bypassing increases, reducing output and consequently decreasing motor current draw. Establish a baseline current draw when the system is new to monitor changes over time.

Temperature Checks:  

Increased internal clearances from wear lead to bypassing and excess heat generation. Use an infrared camera or heat-detecting device to identify areas of bypassing. Regularly check inlet and outlet temperatures of heat exchangers to gauge their efficiency.