Importance of familiarisation and paying attention

The DP Equipment Class 3 vessel was conducted in drilling operations, operating in open bus with all 6 thrusters and 3 of 6 generators online.

The environmental conditions were good with wind 214° x 9 kts / DP current 145° x 1.5 kts / Sig Hs 1.0 metre / swell 0.5 metre.

Selected into DP were 2 DPS (1 x Monitor Online), 1 x HPR & 1 x HAIN.

At 09:42 hrs the Senior DPO observed the loss of all (raw data) position reference systems from DP Operator Station 3 (OS3), which was in charge. No alarms had been activated on the DP System or any warning to the operators.

The SDPO recognised that no active references were selected in DP OS3 and therefore initiated DP OS2. The position reference systems calibrated and the Auto DP Status was reinstated.

It was confirmed that the DP backup was not affected over the period, so what happened?

Upon investigation, it became evident that the timeline leading up to the event held the key.

• The SDPOs had just carried out a crew change at 07:40 hrs, only 2 hours before the incident occurred. The oncoming SDPO, prior to taking the watch, spent the time on the bridge conducting familiarisation and reading his written handover notes.
  
  
• The SDPO took his first watch on the DP desk at 09:00 hrs carrying out hourly DP checks and familiarising himself with paperwork.
  
  
• Unbeknown to the SDPO he accidentally changed the DP operating mode and placed the DP system on stand-by, subsequently dropping the reference systems.
  
  
• The SDPO was distracted with trying to accomplish multiple tasks and had left the DP desk to attend separate non-related task – deviating from Masters Standing Orders.
  
  
• The SDPO failed to accurately perceive and process the contextual cues and DP system feedback indicating the system was operating in Standby mode, making an incorrect assessment due to the mismatch between their mental model and the actual system state.
  
  
• The DP System was inactive without references for a period of 3 minutes 52 seconds. This led to a vessel excursion of 34 metres.

Following the incident, modifications were recommended to restrict the physical changing of the control mode, where a more consensus action is required:

• Provide additional safeguards against human error specifically, to prevent the unintentional activation of Control Modes.
  
  
• Provide a secondary means of alerting system operators of unplanned deviations from set point whilst connected during well operations. Specifically, to provide a means of notifying operators of excursions during DP System Control Mode changes.

This is reminiscence of an event that occurred in 2016 where, whilst undertaking diving operations, the surge button was unknowingly deselected. Details can be found in DPE 02/16: Unintentional deselection of a DP control function and within NOPSEMA Safety Alert 62.

But the importance of maintaining full attention during the operator's time on the DP desk can never be underestimated, or forgotten. It is often regarded that the Senior DPOs should ‘know better’ but with seniority also comes additional responsibilities and so this is a good reminder to know when there is a time and a place to do certain tasks and when to concentrate on your task at hand, especially when unfamiliar with the vessel/system, or are getting refamiliarised.