Belt and sheave alignment
Tension, align, and replace V-belts on belt-drive recip and screw compressors.
This guide is general field reference for trained, qualified service technicians. It is not a substitute for the original equipment manufacturer's service manual, applicable codes (NEC, OSHA, ASME, local), or the judgment of a licensed professional. Procedures, torque values, pressures, refrigerants, and safety requirements vary by make, model, jurisdiction, and revision. Always verify against current OEM documentation and follow your employer's safety program. Working on compressed-air, electrical, pressure-vessel, and refrigerant systems can cause serious injury or death. By using this guide you accept all risk; AirCompDX and its authors disclaim all warranties and are not liable for any damage, injury, loss, or code violation arising from its use.
LOTO and bleed receiver. Spring-loaded motor bases can pinch — keep fingers clear when releasing tension.
- Straightedge or laser sheave alignment tool
- Belt tension gauge (sonic or deflection)
- Socket set
- Matched-set V-belts (banded or single set from one production batch)
- Sheaves if worn beyond OEM gauge
- 1LOTO and remove guard
Open the disconnect, LOTO, bleed tank, remove belt guard.
- 2Release tension
Slack the motor mount adjustment, roll the belts off — do not pry over the sheave or you'll crack the cords.
- 3Inspect sheaves
Use a sheave-groove gauge or new-belt edge test. If a new belt sits below flush in the groove, the groove is worn — replace the sheave, not just the belts.
- 4Align sheaves
Straightedge or laser across both sheaves. Parallel and angular misalignment under 0.5° each. A 1° misalignment cuts belt life by ~50%.
- 5Install matched belts
Always replace as a matched set. Roll into grooves by hand with the motor at minimum center distance.
- 6Tension to spec
Use a sonic tension meter or deflection gauge. Target deflection ≈ 1/64" per inch of span at the published deflection force. Re-tension after 24 hours of run-in.
- 7Run-up and recheck
Reinstall guard, restore power, observe belt tracking. Re-tension after the first 24 h and after the first 100 h — V-belts seat into new grooves.