Comments: The seat for the stop solenoid on the port main engine was damaged causing a slight air leak past it, this acting on the stop cylinder piston caused a reduction in main engine rpm. The reduction in rpm caused a low voltage alarm followed by breaker trip and low frequency alarm. Power was lost … Continue reading “Bow thruster tripped due to lack of power”
Comments: The bow thruster gave an alarm that pitch was at maximum showing 114% on DP display. Investigation concluded that the full starboard maximum limit command/set point of the bow thruster proportional valve had been adjusted to 70%. During maximum pitch request the valve had to be permanently opened with constant and continuous hydraulic oil … Continue reading “Separate problem with two thrusters caused loss of DP”
Considerations from the above event: This event highlights the possible consequences of deselecting critical DP system buttons. Significant changes to any system should not be made during critical phases of an operation. It was considered highly likely that the DPO was performing multiple tasks when the surge button was unknowingly deselected. Tools are available within … Continue reading “Unintentional deselection of a DP control function”
Considerations from the above event: The crew followed good procedures by suspending operations in a controlled manner ready for investigation.
Considerations from the above event: Whilst it is not clear what caused this event it does stress the importance of field arrival and set up tests designed to identify operator station differences.
Considerations from the above event: All available means should be used to identify the faulty thruster and then shut it down as deselecting it from the DP system might not be effective. Depending on the time frame, it is recommended that the bulk transfer hose is disconnected prior to engaging manual control of thrusters. It … Continue reading “Thruster fault”
Considerations from the above event: It is not clear from the report whether it was the differential correction signal or satellite constellation that was shielded, however operators need to be aware of shielding and shadowing in similar situations. The GNSS constellation screen should be consulted and considered prior to moving closer to a possible obstruction. The … Continue reading “Instability of position reference systems”
Considerations from the above event: From the information provided it would appear that the vessel is set up so as to allow for the worst case failure (WCF). Therefore, if it had been deemed necessary, the vessel would have been capable of remaining on automatic DP following the failure of No 2 shaft generator.
Considerations from the above event: With only two diesel generators on line the DPO must be fully aware of the consequences of a worst case failure (WCF).
Considerations from the above event: The centre of rotation should not be changed during critical operations. Because of the likely increase in length of the lever to control heading, careful consideration regarding power availability and requirements is needed whenever the centre of rotation is changed. If wind sensors are being shielded this could have a … Continue reading “Change of a vessel centre of rotation”