It depends on a number of factors:

1. high tension vs. low tension

2. fabric vs. steel cord

3. dirty side vs. clean side or in combinations

4. belt safety factors for the operating conditions

5. wrap angles and ratio of pulley diameters to above conditions

6. proximity to drive

7. single vs. multiple adjacent drives

8. fluid couplings vs. inverter drives or direct drive without interposing controls

In general, we allow no less than 0.50 seconds belt dwell time between adjacent pulley contacts with belt. Usually, we strive for 0.75 seconds on belts in the range of 3-9m/s. The above have an influence as do other mitigating factors in the arrangement of the pulley system.

The above criterion give some guidance. It is not bullet proof. You will not that many installations have shorter spacings, and do have difficulty with belt splices, pulley shell failures, drive load sharing problems or drive hunting, and belt mal-tracking. ■