Unplanned release of stored energy: Worker struck and injured by tensioning tool

  • Safety Flash
  • Published on 21 December 2017
  • Generated on 22 February 2025
  • IMCA SF 32/17
  • 2 minute read

The International Association of Oil & Gas Producers (IOGP) has published Safety Alert 293 about an incident in which a worker was struck on the head and seriously injured when a tensioning tool came loose and hit him.

What happened?

A four-yearly task was in progress, to check the tension of bolts on the bearing of a floating storage and offloading (FSO) unit turret.

During moving the bolt tensioner, a part (the puller, weighing 13 kg) fell between the bearing stud bolts of the inner (static) and outer (rotating) bearing races. Before it could be removed the FSO weathervaned, trapping and compressing the tensioner part between the two rings of bolts. 

A crew member went to investigate further. As he crouched over the tensioner part, it suddenly came free and struck him in the head causing serious injury. He was promptly medevaced to hospital onshore.

turret working location

turret working location

Tensioner part trapped between bearing race stud bolts

tensioner part trapped between bearing race stud bolts

What went wrong? What were the causes?

  • The risk of a tensioner part falling and becoming trapped between the stud bolts was not recognised in the job safety analysis (JSA), work procedure or turret vendor documentation.

  • This risk was not recognised by the crew member, who placed himself ‘in the line of fire’.

  • No stop work authority was applied when the task deviated from the expected work process.

  • The design of the turret bearing races and stud bolts location allowed the tensioner part to become trapped and compressed when the FSO weathervaned.

Action taken

  • Provide additional safeguarding tools and equipment to prevent the tensioner puller from dropping in between the inner and outer stud bolt or even this tool and equipment could help to support the re-tensioner while moving along the race.

  • Investigate a manual handling tool that will reduce the risk of accidentally dropping the tensioner parts.

  • Review the JSA and work procedure to include routine and unexpected risks and provide troubleshooting guidance. Include JSA to consider weather limits for the work and use of a tug on the FSO stern.

  • Reinforce use of stop work authority if work deviates from normal conditions. Investigate if this task should be performed by a specialist contractor rather than the FSO crew.

  • Develop ‘line of fire’ awareness training.

  • Share information with other operating assets with an FPSO and future project FSO, to design out the hazard, e.g. put the two bearing races and rings of bolts at different elevations.

Latest Safety Flashes:

Crew transfer vessel (CTV) drifts onto turbine tower

A CTV drifted into and hit a nearby structure at 0.5 knots.

Read more
LTI: Fall from height during FRC maintenance

A worker fell 2.3 m to deck from a small boat in the davit, and broke a leg as a result. 

Read more
Near miss: narrowly avoided fall from height due to missing deck gratings

After a grating was removed, the Chief Engineer, on the way to inspect the work, nearly fell 4-5m.

Read more
MSF: A broken stretcher could have led to injury

The Marine Safety Forum (MSF) published Safety Alert 24-09 relating to a broken stretcher.

Read more
Positive story: Excellent galley hygiene and housekeeping

On a walk-around audit, a member highlights very high standards of housekeeping and hygiene in the galley on one of its vessels.

Read more

IMCA Safety Flashes summarise key safety matters and incidents, allowing lessons to be more easily learnt for the benefit of the entire offshore industry.

The effectiveness of the IMCA Safety Flash system depends on the industry sharing information and so avoiding repeat incidents. Incidents are classified according to IOGP's Life Saving Rules.

All information is anonymised or sanitised, as appropriate, and warnings for graphic content included where possible.

IMCA makes every effort to ensure both the accuracy and reliability of the information shared, but is not be liable for any guidance and/or recommendation and/or statement herein contained.

The information contained in this document does not fulfil or replace any individual's or Member's legal, regulatory or other duties or obligations in respect of their operations. Individuals and Members remain solely responsible for the safe, lawful and proper conduct of their operations.

Share your safety incidents with IMCA online. Sign-up to receive Safety Flashes straight to your email.