Hydraulic System Failures and Troubleshooting Techniques
Hydraulic systems commonly fail due to four primary factors:
- Contamination: As explained in Section 10, hydraulic oils can contain particulate, chemical, or biological contaminants. These contaminants can cause wear on system components, increase system heat, and block small passages. Larger particles like metal shavings and sand lead to ‘phonographing’ on gear pump wear plates, where grooves resembling those on phonograph records reduce pump efficiency and add heat. Smaller particles, less than 5µ in size, may not immediately destroy a pump, but they can cause early wear and disturb the pump’s pressure balance, a phenomenon known as ‘jetting,’ leading to sudden pressure loss. Bearings and journals also suffer wear from these particles. Chemical and biological contaminants compromise the oil’s protective film, leading to particulate generation and heat from increased friction and wear.
- Cavitation: This occurs when gaseous bubbles form in the hydraulic oil due to a high vacuum at the pump inlet. These bubbles implode violently upon reaching the pump’s pressure side, releasing intense heat (up to 5,000º F at the implosion point) and damaging wear plates and pump bodies. Cavitation, a phase change from liquid to gas due to pressure below the liquid’s vapor pressure, is often confused with aeration, which involves air entering the system, often through leaks or insufficient reservoir levels. Aeration makes controls unresponsive and actuator functions erratic, and the compressed air generates heat at high pressures.
- Overpressurization: Excessive pressure in the system can lead to various mechanical failures and inefficiencies.
- Heat: Excessive heat in a hydraulic system can be a cause or a consequence of other issues, leading to reduced efficiency and increased wear.
Vacuum Levels and Hydraulic System Impacts
Vacuum levels in Hydraulic Repair Near Me hydraulic systems are measured in inches of mercury (in.Hg.). A vacuum exceeding 5 in.Hg., especially in gear pumps, can lead to the creation and collapse of vapor bubbles in the oil. The intensity of cavitation damage escalates with higher vacuum levels. High vacuum often stems from obstructions in oil flow from the reservoir to the pump, caused by various factors such as:
- Clogged reservoir breather.
- Blocked suction strainer or filter.
- Shut-off valve being closed.
- Inlet hose being too small.
- Collapsed or kinked inlet hose.
- Excessively long inlet hose.
- Low oil temperature.
- Pump inlet located higher than the oil level in the reservoir.
Cavitation produces a unique sound in the pump, ranging from a ‘marbles-in-a-metal-box’ rattle to a high-pitched whine, indicating vapor bubble implosions. This noise tends to be more noticeable with cold oil and may reduce as the oil heats up.
To prevent cavitation damage, identifying and addressing the cause of the flow restriction is crucial. Hydraulic Repair Near Me Piston pumps, being highly sensitive to poor inlet conditions, may require additional measures like charge pumps or pressurized reservoirs to ensure positive pressure at the pump inlet.
Operating a pump beyond its designed pressure limits can cause significant damage to Hydraulic Repair Near Me components such as input shafts, housings, and wear plates, as well as cylinder packing and hydraulic hoses. When oil flows through a small relief valve orifice, heat can build up rapidly.
Damage from overpressurization occurs when the system consistently operates above the pump’s rated pressure or faces pressure spikes—sudden increases due to changing or binding loads. Even with a relief valve, spike pressures exceeding the pump’s response capacity can cause damage. Signs of overpressurization include excessive wear on gear housing, cracked pump bodies, twisted input shaft splines, or sheared shafts. Pressure spikes or operations above recommended pressure levels can exceed the Shaft Torque Limitation (STL) of the pump’s input shaft, particularly concerning in tandem and triple pump setups where the input shaft endures the torque of all pump sections. STL is calculated by multiplying the pump displacement by the maximum operating pressure, for example, 3.5 cu.in. × 3,000 PSI = 10,500 STL.
Heat in Hydraulic Repair Near Me Hydraulic Systems and Troubleshooting Techniques
In Hydraulic Repair Near Me hydraulic systems, heat is often a secondary issue, emerging as a result of other problems like cavitation, contamination, or overpressurization. Heat can also originate from improperly sized valves, hoses, or reservoirs. A malfunctioning or improperly adjusted relief valve can generate heat, as can hoses or components located near exhaust systems, which absorb and transfer heat to the oil. Excessive heat leads to oil degradation through oxidation, reduced lubrication, and varnish formation. Extremely high temperatures can physically harm pumps or motors and degrade the oil, necessitating its replacement.
Effective Troubleshooting Strategies
Accurate Hydraulic Repair Near Me hydraulic system diagnosis requires essential tools: a vacuum gauge, pressure gauges, a flow meter, and a temperature gauge. Measurements should be taken at standard operating speeds and oil temperatures. Attempting repairs on hydraulic equipment without the right testing tools is both ineffective and risky.
- Vacuum Gauge: This should be connected to the pump’s inlet line. A vacuum reading above 5 in.Hg. at normal engine speeds suggests a blockage potentially leading to cavitation. Check the hose, strainer, shut-off valve, and breather for obstructions.
- Pressure Gauges: Initially use a high-pressure gauge (0–5,000 PSI), switching to a lower range gauge (0–500 PSI) only after verifying the pressure is within its scope. Pressure gauges help adjust relief valves, assess neutral system pressure, and diagnose pump issues.
- Flow Meters: These verify that a pump’s output flow meets specifications and, in conjunction with a pressure gauge, assess pump efficiency at different pressures.
- Temperature Gauge: It’s vital to monitor system operating temperatures, aiming to keep oil temperature below 140º F. If temperatures exceed this, consider increasing reservoir size, adding a cooler, or re-evaluating component sizes for system flow compatibility.
Post-Repair Contamination Prevention
After repairing or replacing Hydraulic Repair Near Me hydraulic system components, preventing contamination is crucial. This involves flushing tanks, cylinders, and hoses, replacing filters, and refilling with new, filtered oil. Operate all valve controls, extend and retract cylinders, and then change filters again before returning the equipment to service.