Case Study - Kommandor Subsea

The Kommandor Subsea 2000 is a 78 meter long, 2500 ton, ship that operates in the North Sea as a support vessel for a remotely operated submersible vehicle (ROV) rated for depths up to 3000 meters. The ROV carries out pipeline inspections, oil rig underwater structural inspections, supporting pipe-laying operations and other very complex tasks. Propulsion is only from electric motors powered by the 5 generators on board; obviously a reliable power supply is top priority.

As the vessel sometimes operates as close as 10 meters from the legs of oil rigs, all equipment must operate efficiently with backup systems in place should something go wrong. The systems must always have enough power for the vessel to move safely away from the platform. Moreover, the maintenance of the systems must be to a very high standard as they need to comply with the many requirements in the various regulatory agencies.

“It is vital for us that the PMS [Power Management System] is reliable,” said Neil Brown, the ship's chief engineer. “A loss of power while the vessel is alongside a platform holds the potential for a major disaster. A blackout would endanger the personnel onboard and could result in the loss of the vessel.”

To hold its position near its target the ship uses a Dynamic Position (DP II) system – a computerized system of controlling a vessel's propellers and thrusters to automatically maintain the ship's heading and position via GPS. To ensure reliability and improve efficiency, in 2006 it was decided to replace the PLC-based power management system (PMS) with a DEIF Delomatic advanced power management system. Brown cites several advantages the new PMS has over the previous one:

  • While in auto-mode the PMS starts and stops the engines as required
  • The touch of just one button activates the DP II. The system does not allow fewer than the requested number of generators in operation.
  • The system synchronizes, load shares and maintains at least three generators while in DP II mode.
  • In case an engine’s pre-warning alarm is activated, the PMS automatically starts up a standby engine before shutting down the faulty engine.
  • If a switchboard load exceeds nominal load, the system starts up an extra engine. (Load dependent start.)
  • The system detects any switchboard failure and deselects the faulty section.
  • It features blackout prevention.

"All in all it's a pretty good piece of equipment,” Brown said.

Since the new PMS continually monitors the load and generators to maximize efficiency, the Kommander Subsea's owner, the British firm Subsea 7 Limited, reports a 12-30 per cent reduction in fuel consumption since the new system was installed.

“Not only does it help us cut back on fuel, it also reduces engine running hours which saves a lot of money on engine spares required,” said Brown.

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