My offshore support vessel was standing by a drilling rig. We were using our dynamic positioning system. The ship’s propulsion is generated by four diesel electric generators. The propulsion system is combination of two bow thrusters and two stern azimuth pods. The engine room watch consists of one engineer always on watch. The charterer’s standing orders are to maintain constant watch in engine room during DP operations, and, depending on power load, 2 or 3 diesel generators are always to be running.
On this occasion, the weather deteriorated. Rain squalls were frequently passing with wind gusts up to force 7, with swell to 1.5 metres. The engine room was attended but only one generator was running.
- A combination of a squall and big waves resulted in large power demand from propulsion system.
- The second diesel generator started in auto mode but did not put itself on line. This resulted in alarms in the machinery space.
- The third diesel generator then started in auto mode but did not put itself on line, with further alarms.
- The fourth diesel generator started in auto mode. This did put itself automatically on line and delivered the necessary power to the propulsion system.
- The time frame was 6 minutes from increase from power demand till the fourth diesel generator could deliver the necessary power.
- During those 6 minutes, the vessel drifted from its position by several metres.
- Subsequently, in response to the alarms, other engineers were called to the engine room. The other diesel generators were put on line manually to deliver more power.
There was no damage but what could happen in such circumstances? Losing position close to a rig could lead to contact with it. Furthermore, with only one generator on line, there was an increased risk of a full blackout, resulting in a major incident.
- Follow the standing orders.
- The bridge watch officers, on seeing an approaching squall, should request additional generator(s) to deliver sufficient power.
- The engine room watch, on observing problems with the power management systems, should react immediately to avoid loss of position of the vessel.
We are keen to receive more reports from the Offshore Sector, and also on incidents from all sectors relating to marine engineering issues. We are therefore pleased to publish this report. We endorse the lessons learned described by the reporter.