As part of its Safety Flashes, IMCA desribes a case of an injury onboard, involving a crew member who had his hand trapped by a moving belt, during maintenance of an Air Handling Unit (AHU) Humidifier.
The incident
A crew member was involved in routine maintenance of an Air Handling Unit (AHU) Humidifier onboard. The AHU was confirmed as electrically isolated and the worker visually checked that the belt was completely stopped.
The worker began the maintenance task as required, and happened to touch the belt with his right index and middle finger to check the tension.
At this point, an unexpected airflow within the ducting caused the air fan to rotate which caused the belt to move. This lead to his glove getting caught by the belt which in turn caused his right hand and forearm to be pulled towards the machine and caught between the belt and pulley. The movement caused his right forearm to get caught between the metal guard and fixed structure around the belt.
He was transferred to hospital, where he received surgery for fractures to his right hand and arm, and returned home to make a full recovery.
See also: Lessons learned: Crushed finger injury during wire transfer operations
Probable causes
By opening the doors of the AHU humidifier, an unexpected airflow was created by a vacuum from inside the AHU, that consequently rotated the air fan which then drew air from outside the AHU, causing the belt to move.
This previously unrecognized hazard was found only to happen when the ventilation outlet from the AHU to the accommodation E-deck is still in the open position,
…IMCA found.
This scenario was re-enacted with several other AHU’s onboard and only the 2 Top-deck AHU’s (#2 and #3) were found to have this unplanned event when the ventilation outlet was still in the open position.
Lessons learned
- A review and update of procedures taking into account the previously unrecognized hazard, providing clear instructions;
- Expecting the unexpected – particularly with any kind of large rotating machines, and when there is a great deal of potential energy that can be unexpectedly released.
