USCG Homeport Marine Safety Alert: Recent failures of dynamic positioning (DP) systems on MODUs

The United States Coast Guard has recently issued the attached Marine Safety Alert about recent failures of dynamic positioning systems on mobile offshore drilling units.

Clarification has been sought on the following recommendations from the safety alert:

• Where ride-through capability is an essential part of the DP redundancy concept, it should be proven by live short circuit and ground fault testing.
• Perform regular thermal imaging surveys of DP system electrical equipment (e.g. switchgear, drives, motor controllers, etc.) as part of a preventative maintenance program to provide early detection of faulty or loose connections.

The response, which should be noted, was:

• Guidance does state that analysis and proper planning is required to undertake short circuit testing;
• The intent is to do this not at FAT, but on the vessel, with appropriate planning and safety precautions;
• Additional guidance is provided in the Marine Technology Society Techop guidance;
• One of the objectives is to have the test validate the model, so that subsequent testing can be done with analytical and modelling techniques based on a validated model;
• Any short circuit testing is to be accompanied by the proper planning and with appropriate risk mitigating measures in place.

The safety flash draws attention to the Marine Technology Society’s operational guidance which is available from the MTS dynamic positioning website www.dynamic-positioning.com. It should be noted that this guidance refers extensively to IMCA guidance.

We would also like to draw attention to the guidance contained within Offshore vessel high voltage safety.