Missing screw and nut assemblies caused construction hoist accident that killed five

Missing screw and nut assemblies were the cause of a construction hoist collapse that killed five construction workers in Sweden last year.

The accident, at a construction site in Ursvik, Sundbyberg municipality, Sweden, happened on 11 December 2023 during construction of a 14-floor apartment block.

A rental company provided the hoist, a Scando 650 FC, to general contractor Andersson Company for the work, according to the Swedish Accident Investigation Authority, which has now released a report into the incident.

The hoist was assembled on 24 August and inspected by an accredited inspector. As construction continued, the hoist mast was extended.

The last extension before the accident was carried out on 5 December to allow the hoist to reach the ninth floor.

But on 11 December, between 0941am and 0942am, the construction hoist car collapsed from floor 9 with five workers on board. All five were killed.

The investigation by the Swedish Accident Investigation Authority found that five of the screw and nut assemblies required to hold the mast sections together were missing.

Between two of the sections, all four screw and nut assemblies were missing and the mast was only held together by the friction in the joints between mast tubes and support from a secondary structure.

The investigation report said, “The accident occurred when the load on the mast, where the four screw and nut assemblies where missing, became greater than the structure could hold, leading to the mast sections separating and the hoist car falling to the ground.

“It is likely that the screw and nut assemblies were already missing when a mast extension was performed on 1 November. However, this was not discovered in connection with the assembly, nor in the inspections and service measures taken after the assembly.”

The report found that the accident was caused by “omission to perform relevant safety inspections of the hoist assembly” that prevented detection of the missing screw and nut assemblies.

It added, “At system level, a causal factor was that the current requirements for safety measures in connection with the assembly of construction hoists are insufficient to ensure adequate safety for users.”

Recommendations

The report made a series of recommendations to different bodies. To the Work Environment Authority, Sweden’s regulatory authority that upholds laws about work environment and working hours, it recommended:

  • Investigate how safety measures applied in the assembly process of construction hoists can be improved.
  • Within the framework of its supervision of the systematic work environment management system, investigate how risks involving construction hoists are managed.

Its recommendation to Andersson Company Byggnads AB was to:

  • Integrate risks relating to construction hoists assembly in its systematic work environment safety management.

And its recommendation to construction lift and hoist supplier ABC Bygghissar och Byggmaskiner AB was to:

  • Improve routines for inspections and service activities with the goal to reduce the risk for assembly errors.
  • Take measures to ensure that established safety routines are followed and that deviations are reported and addressed.
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