1. Description of the problem and scope of application
A high dew point in a refrigerated compressed air dryer is a critical fault, leading to condensation in the pneumatic network. This causes equipment to corrode, pneumatic tools to fail, and damage to sensitive control systems. This manual is intended for the diagnosis of dehumidifiers with a capacity of 0.5 to 50 m³/min in industrial conditions.
Severity classification: Critical (when dew point exceeds 7°C under nominal conditions).
2. Safety measures
WARNING: Before starting maintenance work on the refrigeration circuit, perform a Lockout/Tagout (LOTO) procedure for the power supply and close the compressed air inlet/outlet valves, depressurizing the system.
Cold agents can cause frostbite when in contact with the skin. Always use safety glasses and gloves. Work must be carried out in an area with proper ventilation.
3. Necessary tools
| Tool | Characteristics | Purpose |
|---|---|---|
| Hygrometer (dew point sensor) | Range -20°C...+20°C | Actual dew point measurement |
| Manometric collector | For the appropriate type of refrigerant | Checking the pressure in the refrigeration circuit |
| Thermal imager | Sensitivity < 0.1°C | Detection of clogging zones of the heat exchanger |
| Multimeter | True RMS | Checking the power supply of the compressor/fan |
4. Initial assessment checklist
| Parameter | What to check |
|---|---|
| Air suction pressure | Does it correspond to the passport data (usually 7-10 bar)? |
| Air temperature at the entrance | Does it not exceed the limit of 45°C? |
| Operation of the condenser fan | Does it work, is there any obstruction to air flow? |
| Condensate removal system | Does condensate discharge during operation? |
5. Diagnostic scheme
- Symptom: High dew point (>7°C)
- Step 1: Check the steam trap.
- If condensate does not come out → Reason: Clogging of the drain or malfunction of the valve.
- If condensate comes out → Go to Step 2.
- Step 2: Check the refrigerant pressure (suction pressure).
- Pressure too low (< 2-3 bar, for R134a/R407c) → Cause: Refrigerant leakage or capillary tube blockage.
- The pressure is too high (> 5-6 bar) → Cause: Air overload or compressor failure.
- Step 3: Check the air-to-air/air-to-refrigerant heat exchanger.
- The temperature difference at the outlet is high → Reason: Contamination of the heat exchange surface.
- Step 1: Check the steam trap.
6. Malfunction matrix
| Symptom | Probable reasons | Diagnostics | Expected result |
|---|---|---|---|
| High dew point, low suction pressure | Refrigerant leak | Checking pressure at rest (equal to ambient temperature) | The pressure is lower than the table pressure |
| High dew point, high suction pressure | Overload, dirty capacitor | Condenser temperature check | Temperature > 50°C |
| Water is in the network, there is no condensate discharge | Defective valve | Manual drainage testing | No condensation |
7. Analysis of the main reasons
7.1 Refrigerant leak
Reason: Microcracks in solder joints or corrosion of copper tubes. This leads to a decrease in cooling efficiency. Confirmation: Using an electronic leak detector. Consequences: Complete cessation of cooling, overheating of the compressor.
7.2 Contamination of the heat exchanger
Cause: Dust and oil deposits in compressed air. Confirmation: Thermography shows uneven temperature distribution. Consequences: Decreased productivity, increased pressure drop.
8. Resolution procedures
- Refrigerant leak: Find the place of the leak, replace the filter-drier, evacuate the system (at least 30 minutes), refill the refrigerant according to the weight indicated on the nameplate (±5g).
- Heat exchanger cleaning: Use special chemicals for washing aluminum/copper heat exchangers. Do not use aggressive alkaline agents.
9. Preventive measures
| The reason | Strategy | Monitoring method | Periodicity |
|---|---|---|---|
| Dirt in the condenser | Blowing with compressed air | Visual inspection | Every month |
| Contamination of filters | Replacement of filter elements | Pressure drop indicator | Every 2000 hours |
10. Spare parts
| Detail | Specification | When to replace | UNITEC-D category |
|---|---|---|---|
| Condensate diverter | Electronic, 230V | When it fails | Pneumatic components |
| Filter-drier | Cooling, 1/4" | At each contour dissection | Refrigerating components |
Order original spare parts at https://www.unitecd.com/e-catalog/
11. Links
ISO 8573.1: Compressed air quality standards. OEM (Manufacturer) Instruction Manuals.
