1. Description of the problem and scope of application
Slow or erratic operation of pneumatic cylinders is a critical problem, leading to disruption of automation cycles, reduced productivity and risk of equipment damage. This manual covers double and single acting cylinders used in industrial equipment. Severity: Critical (if affecting safety or production line synchronization).
2. Safety measures
WARNING: Before starting diagnostics, you must perform the LOTO (Lockout/Tagout) procedure. Turn off the compressed air supply and release the residual pressure in the circuit. Failure to do so may result in sudden, life-threatening movement of the cylinder rod. Use safety glasses and gloves to protect against exposure to compressed air and residual lubricants.
3. Necessary tools for diagnosis
| Tool | Technical characteristics | Purpose |
|---|---|---|
| Manometer (digital/analog) | 0-10 bar, accuracy class 1.6 | Measurement of pressure in the supply line and in the cylinder cavities |
| Multimeter | DC voltage measurement function | Checking the supply of electromagnetic coils of distributors |
| Thermal camera | Range -20°C...+300°C | Detection of local overheating (friction) or air leaks |
| Air flow meter | According to the diameter of the piston | Checking the throughput of pneumolines |
4. Initial assessment checklist
| Parameter | What to check |
|---|---|
| Input pressure | Does it correspond to the passport data (usually 6 bar)? |
| Filter status | Is there a pressure drop across the filter-regulator? |
| Visual inspection | Are there any visible air leaks, damage to the stem, bends in the tubes? |
| History of changes | Was work done on the system the day before? |
5. Diagnostic system
Diagnosis is based on the exclusion method:
- Analysis of the air network: If the inlet pressure is less than 5 bar, the cylinder will operate unstable.
- Distributor Check: If the distributor does not open fully, airflow is restricted.
- Speed control: Check throttle settings (flow control).
- Mechanical check: Disconnect the rod from the load. If the cylinder works normally without load, the problem is in the mechanical part or the lubrication of the guides.
6. Malfunction matrix
| Symptom | Probable reasons | Diagnostic test | Expected result |
|---|---|---|---|
| Slow motion (both ways) | Insufficient pressure, clogged throttle, wear of piston seals | Measure the pressure, check the patency of the throttles | The pressure is 6 bar, the throttle is open |
| Jerks/instability | Lack of lubrication, wear of seals, mechanical jamming | Measure air consumption, check movement resistance | Smooth movement without jerks |
7. Root cause analysis
Seal wear: Occurs due to the abrasive effect of particles or aging of the material. It is confirmed by measuring the air flow between the cavities through the exhaust hole when applying pressure to one cavity. Leads to a loss of effort and a drop in speed.
Insufficient lubrication: Leads to increased friction between the cuffs and sleeve. It is characterized by an elevated body temperature (detected by a thermal camera).
8. Step-by-step repair procedure
- Replacing seals: 1. Relieve the pressure. 2. Disassemble the cylinder. 3. Remove the piston rod. 4. Clean the sleeve. 5. Install new seals with the application of a consistent lubricant (for example, based on silicone). 6. Assemble and test.
- Adjustment of the throttles: Open the throttle to the maximum, then gradually close it until the required speed is reached. Check the reliability of fixing the screw.
9. Preventive measures
| The reason | Strategy | Method | Interval |
|---|---|---|---|
| Air pollution | Air purification | Checking the filter | Every month |
| Seal wear | Planned replacement | Monitoring of leaks | Every 6-12 months |
10. Spare parts
| Description | Specification | When replacing | Category UNITEC |
|---|---|---|---|
| A set of seals | According to the article | When effort falls | Pneumatics/Seals |
| Throttle | G1/8" - G1/2" | In the absence of regulation | Pneumatics/Armature |
Order spare parts on the website: https://www.unitecd.com/e-catalog/
