A guide to finding and correcting the causes of improper operation of a pneumatic cylinder

1. Problem description and scope

This document describes methods for diagnosing and correcting causes of pneumatic cylinder malfunctions, including slow or constant operation. Problems can occur in various types of equipment, including presses, automatic lines, screwing units, and conveying equipment. Severity classification: critical (disability), severe (reduced productivity), minor (minor deviation).

2. Safety precautions

Stop equipment before diagnosis
Use lockout and tagout (LOTO) procedures to ensure safety during diagnosis. Disconnect electrical and pneumatic power before accessing the cylinder.
Using personal protective equipment
Wear gloves, goggles and protective equipment against harmful liquids when working with seals or lubricants.
Attention to stored energy
Before operation, make sure that all components do not contain stored compressed air energy, especially in high pressure systems.

3. Necessary diagnostic tools

4. First assessment (checklist)

5. Systematic flow of diagnostics

1. Symptom: Slow operation of the cylinder
   1. Check the pressure in the pneumatic system: acceptable value: 5-8 bar, alert: < 4 бар або > 10 bar
   2. Use a pressure gauge to measure the pressure in the supply lines
   3. If the pressure is correct, check the operation of the control valves
   4. If the valves are suitable, check for blinding in the output lines
   5. If there is no blanking, check for leakage through the seal
   6. Use a thermal camera to detect overheating
   7. If there is no overheating, check for vibrations
   8. Use a vibration analyzer to measure vibrations: acceptable value: < 2,5 мм/с, alert: > 5 mm/s
   9. If the vibrations are higher, check the balance and mounting of the cylinder
   10. If the vibrations are correct, check the operation of the outlet valve
2. Symptom: Constant operation of the cylinder
   1. Check the pressure in the pneumatic system
   2. If the pressure is correct, check for air leaks
   3. Use a manometer to measure the pressure in the system
   4. If pressure is correct, check for seal leaks
   5. If there are no leaks, check for vibrations
   6. Use a vibration analyzer to measure vibration
   7. If the vibrations are higher, check the balance and mounting of the cylinder
   8. If the vibrations are correct, check for bad connections
   9. Use a thermal camera to detect overheating
   10. If there are no overheating, check for bad connections

6. Matrix of causes of defects

7. Analysis of the causes of defects

7.1. Insufficient pressure in the system

Reason: A decrease in pressure in the pneumatic system can occur due to leaks, lack of filters, or improper adjustment of control valves.
Confirmation: Pressure measurement with a manometer. If the pressure is higher than 8 bar or lower than 5 bar, there is a corresponding problem.
Side effects: Reduced performance, no operation, delamination of seals.

7.2. Seal leakage

Reason: Seals can fail due to wear, misadjustment or improper assembly.
Confirmation: Using a thermal imager or performing a visual inspection. If there is a leak, it may be detected due to pressure drop or air loss.
Side Effects: Decreased efficiency, air loss, possible wear of internal components.

7.3. Improper valve adjustment

Reason: Control valves may be misadjusted due to improper adjustment or lack of regular maintenance.
Confirmation: Checking valve adjustment and measuring system pressure. Improper adjustment may result in improper air distribution.
Side effects: Malfunction, reduced performance, malfunction.

7.4. Vibration or overheating

Reason: Vibrations can occur due to improper mounting, lack of balance, or incorrect adjustment of control valves.
Confirmation: Vibration measurement by analyzer. If the vibration is higher than 5 mm/s, there is a problem. Overheating can be detected by a thermal camera.
Side effects: Incorrect operation, wear of components, lack of efficiency.

8. Step-by-step correction procedures

8.1. Correction of insufficient pressure

1. Check the system pressure. If the pressure is higher than 8 bar, perform additional air mixing.
2. If the pressure is below 5 bar, check for leaks or incorrect connections.
3. Check the filters for contamination.
4. Change the adjustment of the control valves to achieve an acceptable pressure.
5. Check for leaks in the system after patching.

8.2. Repair of leaks due to sealing

1. Disarm the system and lock and tag.
2. Open the cylinder and check the seal.
3. Replace worn seals with new ones according to specifications.
4. Check the fixing of the cylinder and the adjustment of the valves.
5. Measure the pressure again and perform a test run.

8.3. Correction of incorrect valve adjustment

1. Perform control valve diagnostics.
2. Change valve settings to achieve acceptable pressure.
3. Check for leaks or improper connections.
4. Measure the pressure again and perform a test run.

8.4. Fixed vibration or overheating

1. Check the fastening of the cylinder and the absence of vibrations.
2. Perform balancing if necessary.
3. Check valve adjustment.
4. Use a thermal camera to measure the temperature.
5. If the temperature is higher than 60°C, change the setting of the control valves.
6. Measure the pressure again and perform a test run.

9. Preventive measures

10. Replacement parts and components

Learn more about components - visit https://www.unitecd.com/e-catalog/

11. Links

• Standards: DSTU 5758:2018, EN 12481:2019, ISO 12100:2010
• UNITEC Catalog: https://www.unitecd.com/e-catalog/
• Original manufacturers' catalogs: Perform diagnostics according to manufacturers' technical data sheets.
• Additional materials: See other maintenance guides at https://www.unitecd.com/maintenance-guides/.