Detachable grip carrier slides backwards down the haul rope
Detachable grip ropeways have been operating in British Columbia since 1965, with the first detachable grip chairlift installed in 1987. During this time significant changes have occurred in the type and style of detachable grips, which has seen many of our ropeways upgraded with newer components.
Recently Technical Safety BC received a report of an empty detachable grip chair sliding backwards down the haul rope, contacting the following carrier that was occupied by three passengers – fortunately no injuries were sustained. This incident occurred at the steepest section of the ropeway, approximately half way up a 2,300-meter-long ropeway.
As the carriers entered the top station the operator noticed the two carriers were in contact and immediately applied an emergency stop. Lift maintenance was called and the passengers were unloaded from the rear carrier with a ladder. The two carriers were removed from the line and the ropeway was run to unload all passengers. The ropeway was then shut down and the passenger ropeway contractor immediately contacted Technical Safety BC to report the incident as required by the Safety Standards Act. Technical Safety BC then gave the contractor permission to start a visual inspection of all the other carriers for the same type of problem.
A safety officer visited the ropeway operator to complete an incident inspection. The grip that slid back was inspected in the shop and it was found to be missing the snap ring, which was mentioned in a service bulletin released by the manufacturer in 2005. The missing snap ring allowed the guide bushing to move, jamming into the grip housing.
The visual inspection of all the other grips on the ropeway confirmed this was an isolated incident specific to this grip – all of the other grips were assembled correctly.
Grip testing showed that the grip could open and close correctly, and it would still be within the required grip profile testing tolerances as it left the station, but the test rod mandrel could be moved freely between the grip jaws. The grip involved in this incident was last rebuilt in December 2017.
Depending on the vintage of ropeway, some manufacturers suggest that all detachable grips be checked by a second person after they have been rebuilt. The CSA Z98-14 does not specifically call for this but Technical Safety BC is advising all ropeway operators to implement and document a second check of all detachable grips after they are rebuilt. This second check should be done by a different person – not the same person who assembled and tested the grip.
This incident is still under review, but at this time Technical Safety BC feels it is likely this event would not have occurred if a second grip assembly check was undertaken by a different person. Additional passenger ropeway contractor requirements relating to this incident will be issued to the passenger ropeway industry either by an Information Bulletin, Directive, or Safety Order.