Incident on personnel hoist at Tumbler Ridge

Incident overview

Workers were re-installing a steel wire rope cable that is used as part of the personnel hoists safety system. The steel wire rope was fed through the lift and the loose end was lowered down the personnel hoist hoistway. As the loose end of the steel wire rope was lowered down the hoistway it inadvertently made contact with a transformer terminal on an energized high voltage transformer.

Regulated industry sector

Elevating Devices

Location

Tumbler Ridge

Investigation conclusions

Site, system and components

This model of wind tower personnel hoist is suspended using a traction steel wire rope system.There is a backup safety on the hoist that also uses a steel wire rope, if the hoist descends too fast the backup safety will activate and stop the hoist using the secondary steel wire rope. The personnel hoist travels from one deck above the main entrance deck to the top deck located below the nacelle.

The high voltage transformer and it’s terminal that was contacted are located in the bottom level of the turbine, located below the main entrance deck. The bottom level is secured from personnel entry by a locked hatch.

Failure scenario(s)

Adjustments were being made to the hoistway so the steel wire rope systems were temporarily removed. After adjustments were complete the steel wire ropes were being reinstalled. Workers were re-installing the safety rope when it was fed through to the bottom deck level. The rope coiled up on that deck and slipped through a small opening in the floor where it contacted a 6KV terminal on a transformer in a controlled area below.

Facts and evidence

An incident report created by the asset owner was supplied along with pictures of the equipment involved and some of the damage. From the pictures the safety rope had clear heat damage at the point of contact where it lined up with the 6KV transformer terminal as well as damage where the rope lined up with the deck at the converter platform level.

Phone interviews with the two of the people that were performing the work at the time of the incident revealed a lack of knowledge of the proper technique outlined for installing the safety rope. The proper technique was outlined in the installation manual with notes on safe work practices, including directions that during rope installations the entire length of the rope

Impact

• Injury
  • Qty injuries: 0
  • Injury description: None
  • Injury rating: None
• Damage
  • Damage description: The safety back-up steel wire rope shorted a 6KV transformer terminal burning the steel wire
    rope.
  • Damage rating: Major

Incident rating

Major