Passenger Ropeways Case Study: Incorrect testing and setup of chairlift brakes
Stopping safely is a non-negotiable when it comes to passenger ropeways, and specifically, chairlifts. The service and emergency brake are used to stop a chairlift when the operator or safety system initiates a stop. The service brake applies to a disc or drum that is attached to the chairlift drive gearbox and the emergency brake applies directly to the drive bullwheel.
The CSA Z98-07 Safety Code for Passenger Ropeways and Passenger Conveyors states in clause 6.6.2 that “the emergency brake and the service brake, acting independently, shall decelerate the rope between a minimum of 0.45 m/s2 and a maximum of 1.5 m/s2 for the ropeway’s range of design loads, speeds, and loading directions.”
During the assessment of a fixed grip chairlift operation, a BCSA safety officer discovered that daily stop checks were not being recorded in the daily log. Upon questioning the maintenance and operating staff, the safety officer determined that the required daily stop checks were not being completed.
Further testing and inspection of the empty chairlift determined that the service brake stop was almost at the maximum deceleration rate allowed and the emergency brake-only stop was well below the minimum allowed deceleration rate.
On this chairlift, a service stop removed power from the drive and applied the service brake and an emergency stop removed power from the drive and applied the service and emergency brake. The emergency brake-only stop is not part of the normal stopping function, but as clause 6.6.2 states, each brake acting independently must decelerate the ropeway within the required rates.
Service break on an older chairlift
Listed below is the line from Annex J of the CSA Z98-07, showing the speed at which this ropeway operated and the maximum and minimum stop time and distance.
Lift Speed = 2.3 m/s Stop Time = Max 5.11 s Min 1.53 s Stop Distance = Max 5.88 m Min 1.76 m
An indicator that something was wrong with the emergency brake set up was that the service stop and emergency stop produced the same deceleration rate. Normally on this tyape of chairlift, the emergency stop is usually slightly faster than the service stop.
The safety officer then reviewed the last load test and determined that the current deceleration rates were far outside those achieved at the last load test.
A conditional pass certificate of inspection was issued with a non-compliance to be completed before public operation. The requirement listed in the conditional pass was to ensure that:
- the brake deceleration rates be set to the five year load test rates,
- the daily stop checks be completed and recorded on the log sheet,
- the required deceleration rates be posted at the drive station.
Because of this finding, and other items found during further inspections at this area, a Compliance Order was also issued relating to improving the areas maintenance program.
This situation demonstrates how important a good maintenance program can be including, but not limited to: supervision, training, documentation, research, oversite, review, and follow up.