Diagnosing and troubleshooting problems with slow or uneven operation of a pneumatic cylinder

1. Description of the problem and the size of the impact

This guide is intended to diagnose and resolve problems with slow or erratic operation of pneumatic cylinders that are common in production facilities. The problem can occur in various types of equipment, including automatic lines, lifting and conveying systems, and can be considered critical due to the impact on productivity and safety. In the case of irregular cylinder operation, the cause must be determined to avoid equipment exposure or production accident.

2. Safety precautions

Turn off the power and perform a lockout/tagout (LOTO) before performing any diagnostic or repair work.
Use protective gloves, goggles, and protective clothing to protect against mechanical and chemical hazards.
Open the ventilation and vent the accumulators before working to avoid stored energy.
Do not diagnostics on working equipment without disconnection and protection.

3. Necessary diagnostic tools

4. First review and checklist

5. Systematic diagnostic schedule

1. Symptom: Cylinder moves slowly or unevenly.
   1. Check the air pressure: Measure the line pressure and compare with the nominal value (4-6 bar). If the pressure is below nominal, find out why.
   2. Check the control valve: Measure the pressure at the outlet of the valve. If the pressure is higher, there may be a problem with the adjustment.
   3. Check for Clogging: Determine if there is a blockage in the system or cylinder inlet/outlet.
   4. Check the oil seals: Measure the oil seals for wear using a micrometer. If the wear exceeds 0.5 mm, it may cause leakage or irregular operation.
   5. Check Lubrication: Determine if there is sufficient lubrication in the system. Lubrication should be within 1–2 g/month.
2. Symptom: The cylinder does not move to its full extent.
   1. Check the stem: Measure the stem size and compare to the nominal value. If it differs by more than 0.2 mm, it may indicate wear.
   2. Check connections: Determine if connections are open or missing.
   3. Check the latch: Determine if the latch is in the correct position.
   4. Check the pressure: Check if the pressure in the system meets the standards.
3. Symptom: The cylinder does not respond to the command.
   1. Check the electrical connections: Use a multimeter to measure resistance and voltage. If the resistance is higher than 100 ohms, there may be a problem with the sensor.
   2. Check Power: Determine if system power is working.
   3. Check the sensors: Use a multimeter to measure the input signals.

6. Matrix of causes and symptoms

7. Detailed analysis of reasons

7.1. Insufficient air pressure

Reason: Insufficient air pressure can occur due to a clogged filter, lack of air in the system, or incorrect adjustment of the valves. This leads to slow operation of the cylinder.

Confirmation: Measure the pressure in the system. If the pressure is below 4 bar, this may be the cause.

Consequences: Insufficient pressure can lead to loss of efficiency or cylinder exposure.

7.2. Wear of oil seals

Reason: Sealing wear occurs due to high pressure, mechanical wear or lack of lubrication. This results in air leakage and uneven operation.

Confirmation: Measure the oil seals for wear. If it exceeds 0.5 mm, this may be the cause.

Consequences: Sealing wear can lead to loss of tightness and exposure.

7.3. Clogging in the system

Reason: Clogging in the system can occur due to the absence of a filter, high humidity or the use of improper lubrication. This leads to uneven performance.

Confirmation: Check for clogging in the system. If a blockage is found, this may be the cause.

Consequences: Clogging can lead to component wear and loss of efficiency.

7.4. Incorrect valve settings

Reason: Incorrect valve settings can result in incorrect pressure regulation resulting in slow or uneven operation.

Confirmation: Check valve settings. If they deviate from the standards, this may be the reason.

Consequences: Improper valve settings can lead to increased air consumption and loss of efficiency.

8. Step-by-step solution procedures

8.1. Recovery of air pressure

1. Measure the pressure in the system.
2. Check the filter and clean it.
3. Return the pressure to the nominal value (4-6 bar).
4. Check the adjustment of the control valves.
5. Re-measure cylinder pressure and performance.

8.2. Replacing oil seals

1. Turn off the power and perform a lockout/tagout.
2. Measure the wear of the oil seals.
3. Remove the old oil seals.
4. Install new oil seals with the appropriate parameters.
5. Check the tightness of the system.

8.3. Cleaning the system

1. Turn off the power and perform a lockout/tagout.
2. Remove blockages from the system.
3. Check the filters and install new ones.
4. Measure the pressure and operation of the cylinder.

8.4. Adjusting the valves

1. Measure the pressure at the outlet of the valves.
2. Set valve adjustment to nominal values.
3. Check the settings.
4. Re-measure cylinder pressure and performance.

9. Preventive measures

10. Spare parts and components

For spare parts and components, visit UNITEC-D e-catalog.

11. Links

• DSTU, EN, ISO standards for pneumatic systems
• Original technical documents of manufacturers
• UNITEC-D special guides for equipment support