During deep sea navigation at full sea speed, with the chief engineer's approval, the Electrician was engaged in isolating each of the four engine room supply fans for routine planned inspection, maintenance and operation of fire dampers. In order to ensure unrestricted supply of air for the main engine turbochargers, a watertight door leading to the upper deck from the engine room was temporarily secured open. As the work was about to begin, a heavy passing shower caused rainwater to splash on to the running generators through this open door. A rating, who was unaware of why the door was left open, ran up and secured it shut.
When the electrician stopped the first supply fan, there was insufficient air available for the main engine turbochargers, causing sudden depressurisation within the engine room. As a result, the following simultaneous hazardous events occurred:
- Surging of main engine turbochargers and activation of associated alarms;
- Overflow of hydraulic and lubricating oils and boiler feed water from open ends of sight gauge glasses of storage tanks;
- Boilover of hot water from cascade tank observation port;
- Swinging open of unsecured, hinged door of incinerator, causing ash and soot to be ejected at high velocity, which entered the eyes of personnel in the vicinity, and temporarily affected visibility at mid-level platforms;
- Engine room doors became unopenable for a considerable time;
- Feeling of pain and discomfort in eardrums of personnel.
Root cause/contributory factors
Lack of effective communication (risks appear to have been assessed correctly and appropriate control measures were implemented, only to be undone by a well-meaning, uninformed crew member).
Other lessons learnt
- Modern high-power main engines require a 'pressurised' engine room when operating at or near their rated output, requiring all supply fans to be running.
- Routine maintenance involving stoppage of supply fans must only be attempted when the main engine is stopped.
- If for any reason, a supply fan is to be stopped with the main engine running, the engine revolutions must be reduced to a suitably low speed in advance and, if safe to do so, additional doors and other openings to be kept open.
- Any critical maintenance job must be preceded by a meeting, wherein all affected must be effectively briefed on the work plan and special procedures and precautions to be observed.
- Prominent notices/placards must be posted at important locations.
- When not in use, all gauge glass cocks must be closed.
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