What causes fault code CONV-BELT-SLIP (Conveyor Belt Slip — Zero Speed Fault)?

Belt tension too low — belt slipping on drive pulley, especially when loaded. Drive pulley lagging worn smooth — no grip on belt surface. Belt or chain broken — motor spinning but belt/chain is not connected. Gearbox coupler sheared — motor and gearbox turning but output shaft is not. Zero-speed sensor failed or misaligned — not detecting shaft rotation

How do I fix fault code CONV-BELT-SLIP?

STOP the motor immediately — belt slip generates extreme heat and can start a fire on rubber belts. Check if belt/chain is intact — visual inspection along the full length. Check drive pulley engagement — look for glazing or wear on belt contact surface. Verify gearbox output shaft is turning when motor runs — listen/feel for gearbox engagement. Increase belt tension at the take-up — adjust until belt stops slipping under loaded conditions. Replace drive pulley lagging if worn smooth — herringbone or diamond pattern for best grip. Check zero-speed sensor gap — should be 2-5mm from the target (bolt head or tooth on tail shaft sprocket)

Conveyor Belt Slip — Zero Speed Fault

CONV-BELT-SLIP

Zero-speed sensor on the conveyor tail shaft detected that the belt or chain is not moving while the drive motor is running. Indicates belt slip, chain skip, or mechanical disconnect.

high conveyor

conveyor belt slip zero speed tension lagging drive pulley

Probable Causes (ranked)

Belt tension too low — belt slipping on drive pulley, especially when loaded
Drive pulley lagging worn smooth — no grip on belt surface
Belt or chain broken — motor spinning but belt/chain is not connected
Gearbox coupler sheared — motor and gearbox turning but output shaft is not
Zero-speed sensor failed or misaligned — not detecting shaft rotation

Fix Steps

1 STOP the motor immediately — belt slip generates extreme heat and can start a fire on rubber belts
2 Check if belt/chain is intact — visual inspection along the full length
3 Check drive pulley engagement — look for glazing or wear on belt contact surface
4 Verify gearbox output shaft is turning when motor runs — listen/feel for gearbox engagement
5 Increase belt tension at the take-up — adjust until belt stops slipping under loaded conditions
6 Replace drive pulley lagging if worn smooth — herringbone or diamond pattern for best grip
7 Check zero-speed sensor gap — should be 2-5mm from the target (bolt head or tooth on tail shaft sprocket)

Field Trick

Put a piece of tape on the tail shaft and the belt. Run the conveyor and watch both. If the motor is running and the shaft turns but the belt doesn't move, the belt is slipping on the drive pulley. If the shaft isn't turning at all, something between the motor and the shaft is broken — check coupler, gearbox, chain/belt drive.

Suggested Replacement Parts

Parts matched to fault category: Proximity Sensor

Allen-Bradley 872C Inductive Prox Sensor 18mm P/N: 872C-D5NP18-D4 3-wire DC NPN, 18mm barrel, 5mm sensing range, shielded

AutomationDirect $42.00 Amazon $65.00 Grainger $78.00

IFM Efector IFS204 Inductive Sensor 12mm P/N: IFS204 12mm flush mount, 4mm range, M12 connector, PNP NO

AutomationDirect $38.00 Amazon $45.00 Digikey $52.00

Balluff BES 18mm Inductive Sensor P/N: BES M18MI-PSC80B-S04K 18mm barrel, 8mm range, PNP NO, M12 connector

AutomationDirect $48.00 McMaster-Carr $55.00 Amazon $50.00

Prices are estimates. Verify part numbers match your equipment before ordering.

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