200907 Auxiliary blower failure
Auxiliary blower failure
MARS Report 200907
While approaching the pilot station of a port with a relatively difficult approach, the sudden failure of the main engine auxiliary blowers resulted in imminent danger due to the close proximity of rocky shoals. A Lloyd's open form (LOF) was signed in haste and salvage tugs were called for immediate assistance. A serious casualty was averted, the vessel anchored safely and both blowers were repaired with shore assistance.
On investigation, the following facts came to light. Both blowers had been used occasionally for several days prior to approaching port. This was due to insufficient scavenge pressure resulting from inferior fuel from one particular bunker tank. While trying out engines before entering port limits, no.1 blower bearings seized and the motor windings burnt out. At the same time, no.2 blower motor was checked and the insulation was observed to be zero. Despite this, the crew felt that the blower could be operated for the short distance to the berth and the master decided to proceed to embark the pilot with only no.2 auxiliary blower in operation.
Unfortunately, immediately after the pilot boarded, no. 2 blower motor also burnt out and vessel's main engine was immobilised, leading to an emergency situation.
Mariners should take note that the auxiliary blowers are meant to be used only during starting and low RPM manoeuvring, when the turbochargers cannot deliver the minimum required scavenge pressure to ensure efficient combustion. Should there be any need to use an auxiliary blower under normal sea speed, it is a definite indication of a fault in the scavenge system and immediate attention to identify and rectify this is needed. Auxiliary blowers are vital for main engine manoeuvring and their planned maintenance schedules should never be compromised.
Root cause
The crew grossly underestimated the risk involved in attempting to run the blower with zero motor insulation while proceeding to pick up the pilot in closed waters.