Fault Analysis and Diagnosis of Excavator Air Conditioning System

Ensuring optimal performance and longevity of an excavator's air conditioning system requires diligent fault analysis and diagnosis. Before conducting fault checks, the excavator should be parked in a well-ventilated, cool area away from fire sources. Fault analysis and diagnosis typically involve a combination of visual inspection, auditory assessment, tactile examination, and instrument testing.

1. Visual Inspection: Visual inspection involves assessing the condition of various components by sight.

   • Check the wear of the engine drive belt.
   • Ensure the compressor pulley is aligned and securely installed.
   • Inspect the condenser fins for cleanliness and damage.
   • Ensure the evaporator is clean and unobstructed.
   • Check refrigerant pipes and joints for cleanliness and signs of leakage.
   • Inspect system pipes for scratches, bends, flattening, or breakage.
   • Verify the reliability of heating water pipe connections and the operation of the hot water valve.
   • Check for frost or ice formation on external components after machine operation.
   • Observe refrigerant flow through sight glass for abnormalities.

2. Auditory Assessment: Listen for abnormal sounds from the fan, compressor, and air conditioning system.

3. Tactile Examination: Feel the tension of belts to ensure they are appropriately tight.

4. Instrument Testing: Use instruments such as pressure gauges, thermometers, multimeters, and leak detectors for testing.

   • Use a pressure gauge to check compressor pressures under static and operating conditions.
   • Measure temperatures at various points in the system.
   • Use a leak detector to assess system seal integrity.
   • Use a multimeter to check electrical circuit continuity and component operation.

Common Component Failures:

1. Compressor:

   • Leakage from shaft seals, inlet/outlet ports, cylinder head, oiler, or cylinder body.
   • Abnormal noise due to improper clearance adjustment, insufficient refrigerant, or damaged springs in discharge or suction valves.

2. Clutch:

   • Slippage causing overheating and damage to engagement surfaces.
   • Friction between stationary and rotating parts leading to coil damage. Normal coil resistance should be a few ohms.

3. Condenser and Evaporator:

   • Common issues include leaks due to vibration and reduced heat dissipation due to surface dirt.

4. Accumulator:

   • Damaged desiccant filter causing desiccant leakage.
   • Overheating and melting of fusible plug due to high temperature and pressure.

5. Expansion Valve:

   • Common failure is blockage, often caused by system contamination or moisture. Cleaning or replacement may be necessary.

6. High/Low Pressure Switch:

   • Malfunctioning switches can occur when the system experiences high or low pressure conditions. Replacement may be required.

Common System Failures and Causes: Air conditioning system failures can be categorized as electrical, mechanical, refrigerant-related, or lubrication-related issues.

Each of these failure modes requires careful diagnosis and troubleshooting to identify the root cause and implement appropriate corrective actions for effective system operation.