Maintenance Guides 1 min read

Guide to Correction of Point Humidity Deviations in the Dry Air System

Technical analysis: Troubleshooting compressed air dryer dewpoint excursions: refrigerant charge, heat exchanger fouling

Guide to Correction of Point Humidity Deviations in the Dry Air System

1. Problem Description and Scope

This guide is intended for detection and correction of deviations in dewpoint content in the dry air system. Problems occur due to insufficient cooling level, refrigerant loss, heat exchanger contamination or incorrect operation of the moisture discharge valve. They may affect the operation of equipment working in high humidity conditions, including in industrial installations in Ukraine, as well as in production, food industry and energy sectors.

Point dew point deviation is considered critical if the dew point exceeds 20°C, or severe if it goes beyond 10–15°C. Incorrect operation of the dry air system may lead to equipment wear, reduction in product quality, or even system shutdown.

2. Safety Precautions

Important: Perform the lockout/tagout procedure before starting the diagnosis to ensure the equipment is disconnected from energy and pressure. Use protective equipment (pants, gloves, goggles) when working with high pressure or refrigerant.
Important: Do not perform work on an open system if it has stored energy or pressure. Use a high-pressure work kit if the work requires access to internal components.

3. Required diagnostic tools

Tool Name Model/Specification Measurement range Objective
Multimeter Fluke 87V 0–2000 mA, 0–200 V, 0–1000 Ω Measurement of electrical resistance, voltage and current
Thermography FLIR T1020 –20°C to 1000°C Temperature uneven distribution detection
Vibration Analyzer Keysight 35670A 0–50,000 Hz Detection of abnormal vibrations in the heat exchanger
Pressure Indication Dwyer 8310 0–10 bar Pressure measurement in the dry air system

4. Initial Assessment (Checklist)

Operating Conditions Latest changes History of Alarms
System pressure (0–10 bar) Availability of system shutdown/restart Alarm log date
Outlet temperature (10–30°C) Change of set parameters Type of alarm (for example, high humidity)
Moisture content at the outlet (0–20°C) Availability of technical maintenance Alarm frequency

5. Systematic Diagnostic Scheme

  1. Symptom: Humidity exceeds 20°C
    1. Measure the pressure in the system
    2. If the pressure is higher than 8 bar, check the moisture vent valve
    3. If the pressure is higher than 8 bar, check the refrigerant level
    4. If the pressure is higher than 8 bar, check the heat exchanger for contamination
  2. Symptom: Humidity goes out of the range of 10–15°C
    1. Measure the temperature at the output
    2. If the temperature is lower than 10°C, check the heat exchanger ventilation
    3. If the temperature is lower than 10°C, check the refrigerant level
    4. If the temperature is lower than 10°C, check the operation of the water drain valve
  3. Symptom: Uneven temperature distribution
    1. Use a thermograph to detect abnormal areas
    2. If high temperatures are detected, check the heat exchanger for contamination
    3. If low temperatures are detected, check the refrigerant level

6. Symptom Matrix, Possible Causes, Diagnostic Tests and Expected Results

Symptom Possible Causes Diagnostic test Expected result
Moisture > 20°C
  1. Insufficient refrigerant level (10%)
  2. Contaminated heat exchanger (more than 10 mm)
  3. Improper operation of the water drain valve (opening < 50%)
 Level measurement of refrigerant (microscopic levels) The refrigerant level should be within 10–15%
Humidity exceeds 10–15°C
  1. High pressure in the system (more than 8 bar)
  2. Low temperature at the outlet (below 10°C)
  3. Uneven temperature distribution (difference > 5°C)
 Pressure and Temperature Measurement The pressure should not exceed 8 bar, temperature not less than 10°C
Uneven temperature distribution
  1. Contamination of the heat exchanger (more than 10 mm)
  2. Improper operation of the water drain valve (opening < 50%)
  3. Insufficient refrigerant level (10%)
 Valve opening measurement and temperature The temperature should not differ by more than 5°C

7. Analysis of Main Causes

7.1. Insufficient refrigerant level

Causes: Insufficient refrigerant level may be caused by refrigerant loss through leakage or insufficient level at installation. High humidity occurs through inadequate air cooling.

Diagnostic test: Measure the refrigerant level using a microscopic sensor. If the level is below 10%, this may indicate refrigerant loss.

Consequences: High moisture content may lead to equipment wear, reduced product quality, and higher operating costs.

7.2. Contamination of the heat exchanger

Causes: Contamination of the heat exchanger may be caused by deposits, dust or clogging. This leads to a reduction in heat exchange efficiency, which affects the moisture content.

Diagnostic test: Use an infrared camera to detect abnormal areas on the surface of the heat exchanger. If areas with different temperatures are detected, this may indicate contamination.

Consequences: Contamination of the heat exchanger leads to increased energy consumption, reduced system efficiency, and possible failure.

7.3. Malfunction of the moisture discharge valve

Causes: The water drain valve may not function properly due to mechanical failures, absence of electrical power supply or clogging. This leads to accumulation of moisture in the system.

Diagnostic test: Measure the valve opening using a multimeter. If the opening is less than 50%, this may indicate improper valve operation.

Consequences: Incorrect operation of the water discharge valve leads to increased moisture content, which may result in equipment wear.

8. Step-by-step procedures for correction

8.1. Correction of Insufficient Refrigerant Level

  1. Measure the current level of refrigerant (0–15%)
  2. If the level is below 10%, add refrigerant to the set level (10–15%)
  3. Check for leaks in the system (use a leak detector)
  4. Measure the moisture content at the outlet (not more than 20°C)

8.2. Cleaning of the heat exchanger

  1. Use a thermograph to detect abnormal zones
  2. Clean the heat exchanger from contaminants (use drain and nitrogen)
  3. Check the drain valve opening
  4. Measure the moisture content at the outlet (not more than 20°C)

8.3. Correction of the moisture discharge valve malfunction

  1. Measure the valve opening (from 50% to 100%)
  2. If the opening is less than 50%, perform mechanical repair of the valve
  3. Check the valve supply (voltage 230 V)
  4. Measure the moisture content at the outlet (no more than 20°C)

9. Preventive Measures

Main cause Preventive strategy Monitoring method Recommended interval
Insufficient refrigerant level Periodic check of refrigerant level Refrigerant Level Measurement Every 6 months
Contamination of the heat exchanger Heat exchanger cleaning Use of a thermographer Every 12 months
Improper operation of the water discharge valve Periodic check of the valve Valve opening measurement Every 6 months

10. Parts and Components

Part description Specification When to replace Category UNITEC-D
Refrigerant Range 10–15% When the humidity deviates Freon
Heat Exchanger From 5 to 10 mm contamination Upon detection of contamination Heat Exchanger
Water Drain Valve Opening < 50% When the equipment is not working properly Valves

Visit https://www.unitecd.com/e-catalog/ to obtain a list of all components and spare parts.

11. References

  • ISO 8068:2016 — Standard for Measuring Moisture Content
  • EN 15004:2006 — Standard for Dry Air Systems
  • DSTU 4412:2004 — Requirements for the operation of industrial systems
  • OEM technical instructions from manufacturers
  • UNITEC-D Technical Guides

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