A fail safe interlock device should have prevented the drop
Incorrect electrical installation of a ‘fail-safe’ interlock and early activation of a wave compensator led to a fast rescue craft being dropped 18 metres while being deployed in an emergency, says Australia’s Transport Safety Bureau. The chief engineer, who was being medically evacuated, second mate and fourth engineer were injured in the incident on board the Isle of Man registered liquefied natural gas tanker British Sapphire.
ATSB says that that, in the process of lowering the rescue boat, the wave compensator mechanism on the fast rescue boat’s davit was activated early, before the rescue boat had reached the water. A fail safe interlock device should have prevented this by placing the wave compensator into standby mode, only becoming operational when the fast rescue boat was waterborne. However, the electrical installation of the interlock was incorrect and meant it could not work as designed, allowing the wave compensation unit to always operate and the fast rescue boat to make the uncontrolled descent to the sea.
The investigation identified safety issues relating to the commissioning, maintenance, testing, operating instructions and procedures for the fast rescue boat’s wave compensator and its safety interlock system. Further safety issues were identified relating to the job hazard analysis for the use of the fast rescue boat, crew resource management principles and approved training courses for fast rescue boats.
Tests were carried out on board the three sister ships, British Sapphire, British Emerald and British Ruby. with the wave compensator not working correctly on any of them. However, a crucial discovery was made when the engineers on board one of the ships noticed that the electrical drawings had been altered in red pen. As a result of this finding, BP Shipping asked Davit International to supply a set of ‘original’ electrical drawings. These drawings were then forwarded to the ships for further checking.
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