Dropped object – Door detached from TMS during dive
- Safety Flash
- Published on 16 June 2021
- Generated on 18 September 2025
- IMCA SF 17/21
- 2 minute read
During offshore installation activities a Remotely Operated Vehicle (ROV) and Tether Management System (TMS) recovered to deck was observed to have a TMS door missing.
What happened?
The ROV team confirmed that the remaining doors on the TMS were attached. The aluminium TMS door (2 m x 1 m x 4 mm thickness, approximate weight 15 kg) is secured to the TMS frame with 2 pins on top of the door and 2 stainless steel latches on the bottom. In this instance, both the bottom latches failed allowing the door to detach from the TMS frame whilst subsea.
The water depth at the dive location was approximately 1400 metres. The vessel was located approximately 830 m from the nearest subsea asset. The surface current was approximately 1.5–2.0 knots. The door was not found. Analysis of the DROPS cone determined it was very unlikely that the TMS door would have struck or damaged any of the subsea assets.
Showing a TMS door in place
Showing a TMS door missing
A bottom securing latch
A failed latch
What went wrong?
Our members’ investigation noted that there had been no check to confirm secondary retention was in place on the TMS doors as described in the company ROV Operations Checklists.
The securing pins at the top of door did not contribute to the incident.
Actions
- Check and ensure that all fixings are in good working order and that where required, secondary retention is used.
- Review pre-dive/post-dive checklists and add any additional items as required based on the existing condition of the TMS. Purely as an example, for this specific TMS, our member added “confirm that tie wraps are in place”.
- Consider the potential environmental, safety, schedule and legislative impacts from items dropped/lost at sea.
Related Safety Flashes
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IMCA SF 17/19
16 July 2019
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IMCA SF 02/18
23 January 2018
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IMCA SF 11/11
27 October 2011
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