Suspended Work Platform - Hoisting Cable Failure

Hazard Summary

A construction worker fell six (6) floors to his death when one of the hoisting cables of the suspended work platform he was working on failed. The worker had his full body harness on but he was not connected to the lifeline at the time of the accident.

The examination and testing of the hoisting motors and the failed suspension cable revealed that the hoisting cable failed as a result of an overload. The exact cause of the overload in the cable could not be determined. However, there was evidence that the platform had been repeatedly raised to its maximum level causing the hoist motor to frequently hit the thimble. The frequency of this action caused repeated excessive loading, which contributed to the failure of the hoisting cable. There was also evidence of abrasion to the cable by unspecified objects rubbing against its top three (3) feet.

Hazard Location

This hazard may occur whenever work is carried out on a suspended work platform. Failure of the suspension cable may occur when the platform is raised to its maximum height, causing the hoisting motor to repeatedly hit the upper connection of the cable and thereby subjecting it to excessive stress. Furthermore, equipment, sharp objects, or corrosive material coming into contact with the wire cable may cause abrasion.

Legal Requirements

Design, construction and usage of equipment

No part of a project shall be subjected to a load in excess to the load it is designed and constructed to bear, as required by section 31(3) of Ontario Regulation 213/91.

Adequate maintenance of equipment, materials and protective devices

• An employer shall ensure that the equipment, materials and protective devices provided by the employer are maintained in good condition, as required by section 25(1)(b) of the Occupational Health and Safety Act.
• A supplier of a machine, tool, device or equipment, under any rental, leasing or similar arrangement, for use in or about the workplace, shall ensure that the machine, tool, device or equipment, is in good condition. Furthermore, when the supplier has the responsibility for maintenance under the contractual agreement, the supplier shall ensure that the machine, tool, device or equipment is maintained in good condition. Both of these supplier's duties are outlined in section 31 of the Occupational Health and Safety Act.

Inspection requirements of equipment by a competent worker and by the supervisor

Suspended equipment must be inspected before each day's use by a competent worker [section 137(11) of Ontario Regulation 213/91] and at least once a week by the supervisor or a competent person appointed by the supervisor, as required, respectively, by sections 137(11) and 14 (3), (4) and (5) of Ontario Regulation 213/91.

Wearing of a fall-arrest system when working on suspended equipment

• A worker who is on or is getting on or off a suspended platform, a suspended scaffold or boatswain's chair shall wear a full body harness connected to a fall-arrest system, as required by section 141(1) of Ontario Regulation 213/91.
• A worker shall use or wear the equipment, protective devices or clothing that the worker's employer requires to be used and worn, as required by section 28(1)(b) of the Occupational Health and Safety Act.

Recommendations

Where work is being carried out from a suspended work platform, the following recommendations should be observed:

1. The hoisting device should be equipped with a height stop mechanism that will stop the hoist from reaching the top of the cable and hitting the connection to the outrigger beam.
2. Where possible, access to and egress from the platform should not be from the top level of the structure and should be at ground level.
3. A protective sheathing should be used above the hoist over the suspension wire cable in situations where there is a possibility of accidentally damaging the cable during destructive work applications or the use of power tools or corrosives.