- With reference to a pressure compensated variable displacement, swash plate pump, explain FOUR different possible causes of reduction in performance.
Note: The filter has been cleaned, the system is in good condition and there are no visual signs.
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Question
Although the question clearly states that the system is in good condition, many give low / high viscosity, air etc. Many give worn pistons but no explanation as to why the performance is affected unless they explain I can’t award marks. Few appear to understand what a pressure compensated pump is or how it maintains a constant pressure output hence no faults regarding this are given, whereas many appear to believe that the swash angle is externally set.
Possible causes of reduction in performance.
A pressure-compensated variable displacement, swash plate pump, like any hydraulic component, can experience a reduction in performance over time or due to various factors. Here are some possible causes:
Wear and Tear of Internal Components:
- Piston and Slipper Wear: As the pistons and their slippers reciprocate against the swash plate, friction causes gradual wear. This can lead to internal leakage, reducing the pump’s volumetric efficiency and output flow.
- Cylinder Block and Valve Plate Wear: Wear in the cylinder block bores or on the valve plate can also contribute to internal leakage, affecting performance.
- Bearing Wear: The bearings supporting the swash plate and cylinder block experience wear over time. This can lead to increased friction, vibration, and noise, impacting pump efficiency and potentially causing more severe damage if left unchecked.
Contamination of Hydraulic Fluid:
- Solid Particles: Dirt, dust, or wear debris in the hydraulic fluid can cause abrasive wear on the pump’s internal components, leading to leakage and reduced performance.
- Water Contamination: Water in the hydraulic fluid can lead to corrosion, rust, and erosion, further damaging the pump’s internal parts and affecting its efficiency.
- Air Entrainment: Air bubbles in the hydraulic fluid can cause cavitation, which is the formation and collapse of vapor bubbles. Cavitation can damage the pump’s internal surfaces, leading to reduced performance, increased noise, and vibration.
Control System Issues:
- Pressure Compensator Malfunction: A faulty pressure compensator may not accurately sense the system pressure or adjust the swash plate angle correctly, resulting in inconsistent pressure and flow output.
- Control Valve Sticking or Wear: The control valve that adjusts the swash plate angle can become sticky or worn, leading to sluggish response or inaccurate control of the pump’s displacement.
- Electrical or Electronic Faults: In pumps with electronic control systems, faults in the sensors, wiring, or control module can disrupt the pump’s operation and affect its performance.
Other Factors:
- Improper Installation or Alignment: Misalignment of the pump and motor can cause excessive vibration and stress on the shaft and bearings, leading to premature wear and reduced efficiency.
- Inadequate Maintenance: Neglecting regular maintenance, such as oil changes, filter replacements, and inspections, can accelerate wear and tear and increase the risk of breakdowns.
- Age and Fatigue: Over time, even with proper maintenance, the pump’s components will experience fatigue and degradation, leading to a gradual decline in performance.
Signs of Reduced Performance:
- Decreased Flow Output: The pump may not be able to deliver the required flow rate, even at maximum swash plate angle.
- Inconsistent Pressure: The system pressure may fluctuate or fail to reach the desired level.
- Increased Noise and Vibration: The pump may become noisier or vibrate excessively due to internal wear or damage.
- Overheating: The pump may run hotter than usual due to increased friction or internal leakage.
By regularly monitoring the pump’s performance and conducting timely maintenance and repairs, you can identify and address these potential issues before they cause significant problems or lead to costly downtime. Condition monitoring techniques, such as vibration analysis and oil analysis, can also be helpful in detecting early signs of wear or degradation.