Temporary connection to DP system caused short circuit – DP undesired event

Comments:

Various DP equipment, including the DP status lights, were connected via UPS No. 2. Investigation found that the UPS tripped because of a break in the portable cable supplying the DP status lights to ROV control.

• The vessel does not have a permanent ROV system, when an ROV system is mobilised it is a requirement that the ROV control has DP status lights. This is achieved by installing a portable set of lights that are connected to the vessel’s DP system by a cable.
• The same cable had been in use for several years whenever an ROV system was mobilised.
• Inspection procedures have been modified to include portable wiring and a bend preventer/limiter used for future connections.

Considerations from the above event:

• Connection of ANY temporary system to a DP system should be as part of a formal management of change and properly risk assessed.
• The connection of ANY temporary system should be designed to tolerate a short circuit or any other failure.
• Additional systems that are connected to a DP system should be approved by manufacturer and class and should be extensively tested.
• The vessel is recorded as operating within DP equipment class 2, however only satellite derived position reference systems were recorded as being in use.