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.
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.
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 [email protected] 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.
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