Jul 262011

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.

The ‘original’ drawings were different to the ships’ drawings and the on board electrical wiring. When the engineers traced out the differences, they identified that the wave compensator magnetic switches on board British Sapphire, British Emerald and British Ruby had been bypassed.
Says ATSB: “There was no evidence to indicate that the wiring had ever been changed on board British Sapphire, British Emerald and British Ruby, so it is likely that the wave compensator safety interlocks on board the three ships had not worked since commissioning as the magnetic switches had been bypassed since the system had been installed”.

Although the ATSB is satisfied that the safety action taken by BP Shipping and Davit International addresses these safety issues. The ATSB remains concerned about the adequacy of training in the use of wave compensation units on fast rescue boat davits and has released a safety advisory notice to national and international maritime training institutions about this safety issue.

Full report

See also:

British Cormorant FRB Drops, Injures

Tombarra Tragedy – Watch That Weight, Says MAIB

Tombarra Tragedy Highlights FRC Incidents

FRC Davit Wire Break Was A Head Job

Check Hydralift Davit Hydraulics

Watch That FRC Winch

When an FRB is just a drop in the Ocean

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