A recently installed GRF30-100 escalator experienced operational issues during initial use, displaying a PLC error code indicating overspeed or underspeed. Investigation revealed that the power supply was stable, and both the PLC and pulse receiver were functioning correctly. However, the pulse receiver installed on the service brake and the magnetic sensor block were misaligned, with an excessive vertical gap between them.
Cause Analysis
The escalator’s speed monitoring system relies on a flywheel coaxial with the motor mounted on the service brake. Beneath the flywheel is a magnetic sensor block, with the pulse receiver attached to the brake support and connected to the power switch. As the flywheel rotates, the pulse receiver collects signals from the magnetic block. The PLC uses these signals to monitor speed and control the escalator.
If the escalator speed exceeds 1.2 times the rated speed, the speed monitoring system cuts power to the escalator, in compliance with GB16899-1997 national standards. Misalignment and excessive vertical gap between the pulse receiver and magnetic block prevented proper signal detection, causing the PLC to trigger a power cut and stopping escalator operation.
Repair Method
To correct the issue, loosen the pulse receiver mounted on the service brake support. Align it precisely with the magnetic sensor block using the flywheel’s reserved holes, adjusting the vertical gap to 5mm. Once secured, the escalator operates normally.
Chain Wear and Slack Affecting Ride Comfort
Symptoms
After several years of operation, passengers may notice uneven movement or discomfort during use.
Cause Analysis
Most escalators use chain-driven transmission between the drive motor, main drive shaft, and handrail drive shaft. Over time, continuous engagement and disengagement of the chain with sprockets produces wear. Chains may ride above the pitch diameter of the sprocket, causing jerky motion, misalignment, or delayed handrail speed relative to steps.
Repair Method
Inspect all chain drives between the motor and main drive shaft and replace worn chains or sprockets as needed. Adjust the motor base tension cam to ensure proper chain tension. Similarly, check the handrail drive chain and sprockets, replace if necessary, and adjust the handrail tension bolts. Proper replacement and tensioning restore smooth and comfortable escalator operation.
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Post time: May-26-2026