Procedures for ploughing using DP discussed – DP observation

Comments:

The report concluded that the DPO was conducting too many concurrent tasks so that he did not sufficiently monitor the vessel speed during the time the vessel was being controlled with JSAH.  Further to this, company procedure/standing instruction have been changed so that changing the position of the targeted waypoint can be avoided except in the most necessary of cases.  If it is found necessary to change the waypoint position, then the ploughing operation should be temporarily suspended by stopping the vessel and selecting automatic DP.

Considerations from the above event:

• It would be of considerable benefit if plough pulling forces, which can vary greatly, were fully integrated to the DP.  It is not clear if this was the case and whether the direction of forces was interfaced;
• It appears that a proper evaluation of the operation was not made: familiarity of the system is required together with adhering to company procedures;
• A proper understanding of the relationship between position reference systems and forces is required;
• Consideration should have been given to reduce speed to the operational minimum, the slower the progress of the plough the less effect it will have on the vessel’s positioning capability, as inertia becomes less effective.