Diver fouled on descending load
- Safety Flash
- Published on 9 February 2010
- Generated on 30 March 2026
- IMCA SF 01/10
- 2 minute read
A Member has reported that, during the work on a floating production storage and offloading unit (FPSO), a diver’s umbilical became fouled on a flexible riser.
What happened?
The riser had been disconnected from the underside of the FPSO by an air diver working at 40fsw. The diver had rigged up a tirfor for a lateral pull to aid separation of the riser which was secured to the support vessel crane and winch with 10T webbing slings.
When the lateral pull was applied, the flexible riser dropped, parting the slings resulting in an uncontrolled descent to the seabed at -100msw.
At this point, the diver’s umbilical was fouled on the crane wire resulting in the diver being dragged down to -70fsw before he could clear himself and return to the dive basket for recovery to the surface.
The company found the root causes to be the following:
- The riser was substantially heavier than expected and detailed by the client.
- Webbing slings were used as opposed to wire rope slings.
The company has introduced the following measures from lessons learnt:
- Umbilical management is critical for all diving operations. Excess and unwanted umbilical slack should be taken up at all times by the diver tender. The diving supervisor, diver and tenders should be alert and proactive in this respect.
- Webbing slings should not be used underwater particularly when contact with sharp edges is possible.
- Attention to detail when calculating weights underwater to include marine growth and dynamic loading should identify the need for proper and suitable rigging.
- The diver is to remain well clear and if possible return to surface when such activities are planned.
Members are reminded of the need for a robust risk assessment system and diving project plan to be in place before diving operations should commence.
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.