What they do
In belt-driven machines, belts transmit power and set the speed ratio. In direct-driven machines, a coupling joins the motor to the airend and absorbs misalignment and shock. Both wear with use.
Symptoms of a problem
Look for:
- Squealing, belt dust or visible cracking
- Vibration, noise or loss of output
- Overheating bearings or uneven wear
- Slipping or a failed coupling element
Identify the part
To identify:
- Compressor make, model and serial number
- Belt type and profile, number of belts, or coupling type and size
- Pulley or hub dimensions
- Photographs of the existing parts and any markings
Alignment and tension
Belts need the correct tension and matched sets, and couplings need correct alignment. A new part fitted to a misaligned drive will fail early, so alignment is checked as part of the job.
Before you order
Confirm that the belts or coupling are matched sets and suit the machine's power and speed.
Ask for the supply status of the item: whether it is genuine, OEM-approved or an alternative, and whether it is in stock or must be sourced.
Check the lead-time basis and the warranty terms that apply.
Frequently asked questions
Should I replace all belts together?
Yes. A mixed set of old and new belts wears unevenly, so belts are replaced as a matched set.
How often should I check belt tension?
Check at the intervals in the maintenance schedule and after the first run-in period of new belts.
What causes a coupling to fail?
Misalignment, overload, age and contamination. We look at the cause when replacing the element.
Field guide
Belts and couplings: what wears, and how to tell
Belts and couplings carry every kilowatt from the motor or engine to the compressor. When they slip, crack or misalign, delivery falls, bearings run hot and other parts start to fail. Most problems are visible long before a breakdown if someone looks.
| Sign | Likely cause | What to do |
|---|---|---|
| Squeal at start or under load | Belt slipping: low tension, glazing or oil contamination | Check tension, clean pulleys, replace glazed or oily belts as a set |
| Cracks across the belt back | Age, heat or a pulley too small for the belt section | Replace the full set; check pulley diameters against the specification |
| Belt rubbing one side, edge wear | Pulley misalignment | Re-align motor and compressor pulleys with a straightedge or laser |
| Black dust under the guard | Belt wear from slip or misalignment | Find the cause before fitting new belts |
| Coupling element cracked or missing pieces | Misalignment, age or shock loads | Replace the element and check alignment; inspect motor and airend bearings |
| Vibration that changes with load | Worn coupling, loose pulley or soft foot | Stop and inspect; do not keep running |
Good practice
- Replace multi-belt drives as a matched set, never one belt at a time.
- Re-check tension after the first hours of running, as new belts stretch.
- Keep oil and condensate off belts; find and fix the leak.
- Record the belt section and length, pulley sizes and coupling type in the machine file, so the right parts can be ordered next time.
On automatic belt-tensioning systems, check the tensioner itself: a seized tensioner gives the same symptoms as a loose belt.
What to send for a quotation
- Compressor make, model and serial number (nameplate photo).
- Belt markings: section and length, and the number of belts.
- Coupling type and the motor and airend shaft details if known.
- A photo of the drive with the guard removed and the machine isolated.
Send it through find my part or the spare parts enquiry, or call +91 99590 60718 or +91 92468 88812.