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Failure of chamber door hydraulic actuator - DEV imca
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Failure of chamber door hydraulic actuator

A member has reported the failure of a transfer under pressure (TUP) door hydraulic actuator. After divers had transferred from the chamber into the bell, an attempt was made to close the upper door using the hydraulic hand pump. The hydraulic actuator failed, causing the door to drop. Safety procedures in place prevented any injury to the divers.

Failed actuator
Failed actuator

Upon further investigation it transpired that the heliox gas mix had managed to migrate past the seals inside the rotary actuator and had pushed the hydraulic fluid out of the hydraulic lines, losing hydraulic control of opening and closing the door.

The actuator was removed from the chamber and stripped down completely. All the seals inside the actuator were found to be completely perished inside.

This particular actuator had never been removed, stripped and seals checked for over ten years due to the inaccessibility of the unit and being hidden under deck plating.

Members are reminded of the importance of identifying critical components and the subsequent inclusion of these components into the planned maintenance systems.

Safety Event

Published: 14 August 2007
Download: IMCA SF 07/07

IMCA Safety Flashes
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IMCA Safety Flashes summarise key safety matters and incidents, allowing lessons to be more easily learnt for the benefit of all. The effectiveness of the IMCA Safety Flash system depends on Members sharing information and so avoiding repeat incidents. Please consider adding safetyreports@imca-int.com to your internal distribution list for safety alerts or manually submitting information on incidents you consider may be relevant. All information is anonymised or sanitised, as appropriate.

IMCA’s store terms and conditions (https://www.imca-int.com/legal-notices/terms/) apply to all downloads from IMCA’s website, including this document.

IMCA makes every effort to ensure the accuracy and reliability of the data contained in the documents it publishes, but IMCA shall 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.