1. Scope and purpose
This manual covers standard maintenance procedures for pneumatic cylinders (according to the ISO 15552 and ISO 6431 standard) used in industrial equipment. Timely maintenance prevents air leaks, unstable operation ("stick-slip" effect) and premature failure of pistons and rods. Regulatory work should be carried out every 5,000 km or once a year, depending on operating conditions (dustiness, humidity, intensity of cycles).
2. Safety measures
WARNING: COMPRESSED AIR AND UNEXPECTED MOTION HAZARD. BEFORE STARTING WORK, THE LOCKOUT/TAGOUT (LOTO) PROCEDURE MUST BE PERFORMED. CLOSE THE AIR SUPPLY VALVE AND RELIEVE THE RESIDUAL PRESSURE IN THE SYSTEM.
Use personal protective equipment (PPE): safety glasses, gloves, special shoes. The work area must be clean, as contamination (dust, metal shavings) is the main cause of damage to new seals.
3. Necessary tools and materials
| Tool/Material | Specification | Quantity |
|---|
| Set of keys (corner/capsular) | According to the dimensions of the cylinder | 1 |
| Snap ring remover | Type C (internal/external) | 1 |
| Torque wrench | The range is 5–50 Nm | 1 |
| Lubricant for pneumatics | Compatible with NBR/PUR (e.g. silicone based) | 1 tube |
| Lint-free fabric | For cleaning internal surfaces | 5 |
| Cleaner (degreaser) | Non-aggressive to rubber seals | 1 bl. |
4. Checklist before servicing
| Element | Verification | Eligibility criteria | Notes |
|---|
| Piston rod | Visual inspection for scratches | Absence of burrs, corrosion | If there are burrs, the rod needs to be replaced |
| Cylinder body | Checking for deformations | No dents | Deformation leads to leakage |
| Fastening | Checking the tightening of bolts | Reliable fixation | Tighten if necessary |
| Air leaks | Hearing test / soap suds | No leaks under pressure | Mark the leakage areas |
5. Step-by-step procedure for replacing seals
- Dismantling: Disconnect the pneumatic tubes. Remove the cylinder from the mounts. Error: Failure to release pressure before disconnecting tubes can cause injury.
- Disassembly: Unscrew the bolts of the front and back covers. Carefully remove the piston rod without damaging the inner surface of the sleeve.
- Cleanup: Remove old seals. Wash the sleeve and stem with cleaner. Wipe dry with a lint-free cloth. Important: do not use abrasive materials.
- Installing the seals: Lubricate the new rings. Install the gasket in the grooves of the piston and cover. Observe the orientation of the sealing lips.
- Assembly: Insert the piston into the sleeve, being careful not to bite the seals. Tighten the cover bolts crosswise according to the tightening torque specified in the technical data sheet (usually 8-12 Nm for cylinders Ø40-50).
6. Adjustment of damping (amortization)
Adjust the damping screws on the cylinder covers:
- Turn the screw clockwise to increase resistance (more damping).
- Turn counter-clockwise to decrease resistance.
- Goal: the piston should slow down smoothly, without sharp shocks in the end positions.
7. Speed regulation (Meter-Out principle)
For stable operation, use chokes with a non-return valve (speed regulators) on the exhaust ports of the cylinder:
- Turn the knob clockwise to narrow the passage and reduce the speed.
- Increase the speed to the required level, checking the stability of the movement. Avoid too high speeds that cause vibration.
8. Checklist after maintenance
| Test | Expected result | Actual result | Status |
|---|
| Leak test | No hissing at 6-8 bar | | |
| Smoothness of movement | Smooth movement without jerks | | |
| Damping | Lack of impact at the end of the move | | |
9. Troubleshooting
| Symptom | Probable cause | action |
|---|
| Air leakage from the stem | Worn stem seal | Replace the sealing set |
| Piston jerks (stick-slip) | Lack of lubrication / wear | Lubricate / replace the seal |
| Unable to adjust the speed | Clogged throttle | Clean or replace the regulator |
10. Maintenance schedule
| The task | Frequency | time | Level |
|---|
| Visual inspection | Every week | 5 min | Operator |
| Checking for leaks | Every month | 10 min | Technician |
| Replacement of seals | Annually | 60 min | Technician |
11. Spare parts
| Description of the part | Typical specification | Category UNITEC |
|---|
| A set of seals | For the ISO 15552 Ø40 series | Seal Kits |
| Speed controller | G1/8, for an 8mm tube | Flow Controls |
Order the necessary spare parts through our e-catalogue: https://www.unitecd.com/e-catalog/
12. Links
- ISO 15552: Pneumatic cylinders.
- ISO 8573: Compressed air quality.
