1. Description of the Problem and Scope of Application
This manual is intended for diagnosing and troubleshooting problems associated with pressure drop in industrial compressed air systems. A decrease in pressure can lead to significant energy losses, reduced performance of pneumatic equipment and accelerated wear of compressors. This problem usually manifests itself in the form of insufficient power of pneumatic tools, slow operation of actuators, or frequent loading/unloading cycles of the compressor.
These symptoms may affect the following types of equipment:
- Compressors (screw, piston)
- Air receivers
- Air preparation systems (filters, dryers)
- Main and auxiliary pipeline networks
- Pneumatic tools and equipment
- Valves, pressure regulators, connections
Classification of the severity of the problem:
- Critical: Immediate stoppage of production, failure of critical equipment. Requires immediate intervention.
- Significant: Decrease in equipment productivity, significant increase in energy consumption, deterioration of product quality. Requires elimination within 24-48 hours.
- Minor: Periodic decrease in performance, slight increase in power consumption. Requires elimination planning.
2. Precautions
⚠ SAFETY WARNING ⚠
- HIGH PRESSURE: Compressed air systems operate under high pressure (typically 6-12 bar), which is a serious hazard. A sudden release of energy can cause personal injury or equipment damage.
- LOCKOUT/MARKING (LOTO): Before performing any diagnostic or repair work on components of the compressed air system, it is MANDATORY to apply lockout/marking (LOTO) procedures in accordance with the company's internal standards and DSTU EN 10332:2018 (ISO 14118:2017). This includes turning off the compressor, disconnecting from the power source, and depressurizing the system.
- SAVED ENERGY: Even after the compressor is turned off, pressurized air can remain in the receivers, pipelines, valves and pneumatic cylinders. Make sure all pressure is completely relieved by using appropriate relief valves or drain points.
- PERSONAL PROTECTIVE EQUIPMENT (PPE): When working, always use approved PPE: safety glasses (DSTU EN 166:2017), headphones (DSTU EN 352-1:2017) to protect against compressor and ultrasonic detector noise, as well as protective gloves.
- HOT SURFACES: Compressors and some system components may have hot surfaces. Be careful to avoid burns.
3. Necessary Diagnostic Tools
The following set of tools is required for effective diagnosis of pressure drop in the compressed air system:
| Name of the Tool | Specification/Model (example) | Measurement range | Purpose |
|---|---|---|---|
| Ultrasonic leak detector | LEAKSHOOTER LKS1000, SDT340, Fluke ii900 | 0.001 – 100 dB ultrasound, 20 kHz – 100 kHz | Accurate detection of compressed air leaks (acoustic method). |
| High precision digital manometer | WIKA CPH6200, Testo 510i | 0 – 16 bar (variable ranges), accuracy class 0.25 (DSTU EN 837) | Accurate measurement of static and dynamic pressure at various points in the network. |
| Flow meter for compressed air | SUTO S401, CS Instruments VA500 | 0.1 – 1500 m³/h (depends on the model and pipe diameter) | Measurement of actual volumetric air consumption and identification of excess consumption. |
| Infrared camera | Flir E8, Testo 872 | -20°C to +350°C, temperature sensitivity < 0.05°C | Visualization of temperature anomalies caused by leaks (cooling of ambient air). |
| Digital multimeter | Fluke 179, Kyoritsu 1012 | Alternating current (up to 1000 V), direct current (up to 1000 V), resistance (up to 50 MΩ) | Inspection of compressor electrical components and control systems (eg valves). |
| Pressure/flow data logger | HOBO UX120-006M, Testo 176 P1 | Pressure range 0-16 bar, registration up to 1 million points | Long-term monitoring of system parameters to detect periodic anomalies. |
| Leak test kit (soap solution) | A specialized solution or soapy water | Not applicable | Confirmation of small leaks detected by ultrasound or for areas with low acoustic noise. |
4. Initial List of Estimates
Before starting detailed diagnostics, it is necessary to collect raw data and conduct a visual inspection. This will help to narrow down the area of fault finding and avoid unnecessary steps.
| Parameter / Observation | Value / State (Write) | Notes / Potential Indicators |
|---|---|---|
| Date and Time | To account for changes | |
| Ambient temperature in the workshop | It affects the efficiency of dehumidifiers and air density | |
| Relative humidity in the workshop | Affects the quality of compressed air | |
| Pressure in the main receiver of the compressor | Standard pressure: usually 7-8 bar | |
| Pressure at the most distant point of consumption | Normative pressure drop: no more than 0.3 bar from the receiver | |
| Current compressor load (%) | Record from the control panel | |
| Frequency of loading/unloading cycles of the compressor | Frequent cycles indicate excess consumption or leaks | |
| Visual inspection of the pipeline network | Signs of damage, corrosion, faulty connections | |
| Compressor and system alarm history | Check the event log on the compressor controller | |
| Recent maintenance of the compressor and preparation system | Filter replacement dates, dehumidifier maintenance | |
| Changes in production processes or connection of new equipment |
5. Systematic Flow of Diagnostics
Diagnostics of pressure drop should be carried out step by step, from general to specific, in order to quickly localize the root problem.
- Symptom Confirmation and Overall Assessment:
- Measure the pressure at the outlet of the compressor (after the receiver, before the dryer) and at the farthest point of consumption using a digital pressure gauge.
- If the pressure difference between these points exceeds 0.5 bar, the pressure drop is significant and requires further investigation.
- Record the reading of the compressed air flow meter (if applicable) to determine the total consumption. If consumption is significantly higher than normal for no apparent reason (new tool, active process), this indicates leaks.
- Primary Localization of the Problem Zone:
- If possible, isolate individual sections of the pipeline network or groups of consumers by closing the appropriate shut-off valves (for example, ball valves according to DSTU EN 331).
- Observe the pressure change in the system.
- If the pressure drop decreases or disappears after isolating the section, the problem is in this isolated section or the consumers connected to it. Go to point 3.
- If the pressure drop remains significant, the problem is probably related to the compressor, the air conditioning system (filters, dehumidifier) or the main piping to the isolation points. Go to point 4.
- Diagnostics of the Pipeline Network and Consumers (when localized):
- Leak detection:
- Put the system into the mode with minimum consumption (or turn off the consumers, leaving the pressure).
- Use an ultrasonic leak detector to systematically scan all connections, fittings, valves, hoses, tees, air cylinders and air tools in a designated section.
- Pay special attention to welds, threaded connections, flexible hoses, quick-release couplings.
- If an area with a high level of ultrasonic noise is found (eg > 20 dB of ultrasonic noise above the background level), confirm the leak with a soapy solution.
- Record all detected leaks.
- Estimating Pipeline Diameters:
- Check pipe diameters in remote or newly connected sections.
- Compare them with calculated values based on air flow and recommended velocities (normative flow velocity in trunk lines 6-10 m/s). If the flow velocity exceeds 15 m/s, this indicates an insufficient diameter.
- Pneumatic Equipment Inspection:
- Inspect pneumatic cylinders, valves, and tools for internal or external leaks.
- Check the settings of the pressure regulators on the end equipment.
- Leak detection:
- Diagnostics of the Compressor and Air Preparation System (with a general pressure drop):
- Filters and Dryer:
- Check the pressure drop on all filters (main, fine filter) and dryers.
- If the pressure drop across the filter exceeds 0.3 bar, the filter is clogged.
- If the pressure drop across the dryer exceeds 0.2 bar, this may indicate a blockage or malfunction.
- Check the dew point after the dehumidifier. If it is higher than the norm (for example, +3°C for refrigerator-type dehumidifiers), this may indicate a malfunction of the dehumidifier, affecting air quality and clogging of the elements.
- Compressor:
- Check the pressure at the compressor outlet. If it is lower than specified, check the compressor controller settings.
- Check the operation of the inlet valve and the minimum pressure valve of the compressor.
- For reciprocating compressors: check the condition of the piston rings and valves (disassembly may be required).
- For screw compressors: check the oil temperature and the operation of the thermostatic valve.
- BOLD: Check the internal components of the compressor only after complete de-energization and pressure relief.
- Filters and Dryer:
6. Matrix of Malfunctions and Causes
The table below summarizes common symptoms of pressure drop, their likely causes, diagnostic methods and expected results.
| Symptom | Probable Causes (ranked by probability) | Diagnostic Test | Expected Result if Cause Confirmed |
|---|---|---|---|
| Rapid, significant pressure drop (by >1 bar) throughout the network during operation, the compressor is constantly running under load. | 1. Large air leak (hose break, main valve failure). 2. Insufficient performance of the compressor (wear, malfunction). 3. Blockage of the main pipeline. |
1. Ultrasonic detector, visual inspection. 2. Measurement of compressor performance (ISO 1217). 3. Pressure drop in areas. |
1. Clear, loud ultrasonic signal, visually visible air flow. 2. The actual performance is much lower than the passport performance. 3. High pressure drop (>0.5 bar) in the problem area. |
| A slow, gradual drop in pressure (0.2-0.5 bar) throughout the network for a long time (for example, at night or on weekends). | 1. Multiple small leaks in connections, fittings, pneumatic cylinders. 2. Wear of valve seals or reducers. |
1. Systematic bypass with ultrasonic detector, soap solution. 2. Checking the tightness of components. |
1. Many sources of weak ultrasonic signal, small bubbles of soap solution. 2. Leaks through the cylinder rod, valve seals. |
| Low pressure at remote or final points of consumption, with normal pressure near the compressor. | 1. Insufficient pipeline diameter. 2. Clogging of filters on the line. 3. Excessive use of quick disconnects or small diameter adapters. |
1. Calculation of pressure losses in the pipeline (EN 13445), flow measurement. 2. Measurement of the pressure drop on the filters. 3. Visual inspection, assessment of throughput. |
1. Estimated pressure losses in the area >0.3 bar, flow speed >15 m/s. 2. Pressure drop >0.3 bar. 3. The presence of bottlenecks in the system. |
| Pressure reduction after the air preparation system (filters, dryer). | 1. Clogging of filter elements. 2. Failure or clogging of the dryer. 3. Malfunction of drain valves or condensate drains. |
1. Measurement of the pressure drop before and after each element. 2. Dew point check after dehumidifier. 3. Visual inspection, manual inspection of work. |
1. Pressure drop on the filter >0.3 bar. 2. The dew point is above the permissible level (+3°C), the pressure drop on the dryer is >0.2 bar. 3. Continuous air leakage through the drain valve. |
| Low pressure, compressor turns on and off frequently (short cycles). | 1. Significant leaks. 2. Malfunction of the control valve (unloading) of the compressor. 3. Incorrect on/off pressure settings. |
1. Bypass with an ultrasonic detector. 2. Checking the operation of the valve. 3. Checking the settings on the compressor controller. |
1. Detection of leaks. 2. The valve does not close the air flow properly. 3. The settings do not meet the requirements. |
7. Root Cause Analysis for Each Malfunction
A detailed understanding of the root causes allows not only to eliminate the symptom, but also to prevent its recurrence.
7.1. Sources of Air
Detailed description: Leaks are the most common and least obvious cause of pressure drop and excessive energy consumption. Even small leaks can account for up to 30% of the total volume of compressed air in the system. Every 1 bar of pressure drop caused by leaks can increase compressor energy consumption by up to 7%. Leaks occur due to:
- Mechanical wear: Seals (rings, gaskets), valve stems, quick-disconnect connections.
- Corrosion: Metal piping and fittings, especially in high humidity conditions.
- Incorrect installation: Insufficiently tightened connections, use of inappropriate sealants or tapes (FUM).
- Vibration: Weakens connections and causes material fatigue.
- Damage: Impacts, abrasive wear, high temperatures.
How to confirm: The ultrasonic detector detects the turbulence of the air flow beyond the working range of human hearing. An infrared camera can detect cold spots as the expanding air cools. The soap solution forms bubbles at the point of leakage.
Potential damage: In addition to energy losses, leaks cause the compressor to run continuously under load, shortening the life of its components (bearings, electric motor, screw pair) and increasing maintenance costs.
7.2. Insufficient Pipe Diameter or Excess Support
Detailed description: If the diameter of the main or distribution pipe is too small for the air flow, it creates excessive resistance to the air movement. According to Poiseuille's law, pressure losses are directly proportional to the length of the pipe and the square of the flow velocity, and inversely proportional to the fourth power of the diameter. An excessive number of elbows, tees, reducers, quick-disconnect connections also increases local supports.
How to confirm: Calculation of pressure losses based on the length, diameter of the pipeline and actual air flow. Flow rate measurement using a flow meter. Standard speed of flow in trunk lines 6-10 m/s; if it exceeds 15 m/s, it indicates insufficient diameter.
Potential damage: The compressor is forced to run at a higher discharge pressure to compensate for the losses, resulting in increased power consumption, overheating and accelerated wear.
7.3. Clogging of Filters and Malfunctions of the Air Preparation System
Детальний опис: Повітряні фільтри (магістральні, тонкої очистки, вугільні) призначені для видалення частинок, масла та вологи. Over time, they become clogged, increasing resistance to the passage of air. Similarly, a faulty dehumidifier may not remove moisture effectively, leading to corrosion and blockage of other components. Typical malfunctions of dehumidifiers include:
- Refrigerating: Clogged heat exchanger, low refrigerant level, dryer compressor failure.
- Adsorption: Wear of adsorbent, malfunction of switching valves or regeneration heater.
How to confirm: Pressure drop measurement on filters (>0.3 bar indicates clogging) and dryers (>0.2 bar). Dew point check after dehumidifier (for refrigerated dehumidifiers should be +3°C). Visual inspection of filter elements.
Potential damage: Increased compressor energy consumption, reduced compressed air quality (ISO 8573-1), which can lead to malfunction of pneumatic equipment, corrosion and blockage of the entire pipeline.
7.4. Compressor malfunctions
Detailed description: A drop in pressure can be a direct result of malfunctions of the compressor itself:
- Reciprocating compressors: Worn piston rings, defective suction or discharge valves, resulting in loss of compression.
- Screw compressors: Worn screw pairs (rare), failure of inlet valve, minimum pressure valve, or discharge control system.
- Incorrect settings: Incorrectly set loading/unloading pressure limits on the controller.
How to confirm: Pressure measurement directly at the compressor outlet. Checking the performance of the compressor in accordance with ISO 1217. Diagnostics of valves and control systems. Compressor event log analysis.
Potential damage: Electric motor overload, compressor overheating, complete unit failure, significant overhaul costs.
8. Step-by-Step Troubleshooting Procedures
The performance of these procedures requires strict adherence to safety regulations (Chapter 2).
8.1. Elimination of Air Leaks
- Identification and Location:
- Isolate the section of piping or equipment where the leak was detected using shut-off valves.
- ⚠ WARNING: Use the LOTO procedure. Completely depressurize the isolated area by opening the drain valves. Переконайтесь у відсутності тиску за допомогою манометра.
- Determine the exact location of the leak with an ultrasonic detector and confirm with a soapy solution.
- Replacement or Repair:
- Connections and Fittings: Unscrew the damaged connection. Clean the threads. Replace the old sealing ring (e.g. NBR 70 Shore A according to DIN ISO 3601) or use a new thread sealant (e.g. Loctite 55 or analogue certified according to DSTU EN 751). Tighten the connection according to the recommended tightening torque (eg 20-25 Nm for G½
