CASE STUDY

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CASE STUDY ON DP OPERATIONS IN 500M ZONE

An incident occurred at approximately 10:30 when a vessel was approaching a platform for a fuel transfer. Due to the restricted visibility at the time of arrival (250m), the vessel went on standby outside the 500m zone. The bridge team started the pre-entry checklist at 12:00. but this was not completed due to the restricted visibility preventing alongside work. It was decided to utilize the time on standby on DP mode to gain some DP time for the bridge team. The vessel set up on DP just over 1 mile from the platform. After a period of just over two hours on DP, the visibility had improved enough to meet the minimum visibility criteria and thus allow the decision to commence the operation. Weather conditions on location at the time were recorded as: wind direction: ENE; wind force: 2; sea height: lm; visibility: poor; temperature: 21C; tide direction 207 degrees true; tide rate: 0.7 knots. Pre-entry checks were recorded in the deck logbook. The pre-entry checks confirmed all equipment was operating correctly, and the vessel entered the 500m zone at 14:20. At 14:38, the chief officer was driving the vessel from the aft console and was going alongside the north face whilst the crane was preparing to lower the hose. This maneuver included thrusting to starboard. As they approached the required station, the chief officer moved the joystick to port to 'check' the starboard movement of the vessel and ease into position. While moving the stick from starboard to port, an unexpected clicking noise was heard, and he immediately felt the tension on the joystick slacken. He immediately deselected the joystick control and operated the manual thruster controls on the aft console whilst at the same time asking the second officer to conlact the installation and inform them there was a problem and they would be pulling off to investigate. The second officer informed the installation and then immediately called the master to the bridge.

Once the chief officer had thrusted off to approximately 40m, he decided to utilize the main propulsion to take a clear escape route straight ahead to exit the 500m safety zone. Prior to entry to the 500m zone, the main engines and rudders had been set up for split rudder configuration, with the port rudder set to 30 degrees to starboard and zero pitch on both main engines. The chief officer applied forward thrust on both engines by moving the propeller pitch to 30 per cent ahead and then prepared to pass control to the forward console where the second officer was in a position to accept control. Navigating from the forward console when going ahead is normal navigational practice, and transfer between the consoles was a routine task that was carried out regularly by all navigational officers. In order to hand over the control to the forward console, both thruster and pitch controls were set to zero, and control was then passed over from the aft console to the forward one where the second officer was stationed to accept control. At this point, the chief officer stated that the vessel began to veer to starboard. The second officer was of the opinion that the vessel was veering to starboard prior to this point. Both parties confirmed that the second officer had commented, "You can't go in there," which would suggest the vessel was already veering to starboard before control was passed. The second officer, on taking control on the forward console, noticed that the rudder indicator was over to starboard, although he could not confirm whether it was one rudder or both or exactly how may degrees to starboard it was showing. He realized that, if he applied ahead propulsion before putting the rudders to port, it would only aggravate the situation and increase the rate of turn to starboard. He therefore activated the forward thrusters to port to swing the vessel's head out of the starboard turn, and the vessel exited the restricted zone and, once well clear, recorded the time of exit at 14:48. The master arrived on the bridge and witnessed the second officer applying the forward thrusters to

BREACH OF PLATFORM BREACH OF PLATFORM BREACH OF PLATFORM BREACH OF PLATFORM

RESTRICTED ZONERESTRICTED ZONERESTRICTED ZONERESTRICTED ZONE

CASE STUDY

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correct the vessel's heading and counter the starboard turn. When the vessel reached a safe distance from the installation, the issue with the joystick was investigated, and it was decided to replace the aft joystick with one from the starboard bridge wing and test it fully. The test proved successful, and when the master was satisfied with the operational integrity of the joystick, the vessel went alongside to accept the fuel hose. Later investigation identified a spring in the joystick had broken. The bridge team confirmed they were aware of the restricted access zone, and they had an installation data card posted on the bridge. They also stated that they were aware that the zone was to protect the risers, and they were aware of the location of the risers. They did not intend to enter the restricted access zone. The second officer confirmed at least one of the forward rudder indicators was to starboard. The rudders had been selected in the joystick configuration. The vessel confirmed that the aft console has been selected prior to the joystick being selected, therefore the default on disengaging the joystick was to return the control to the aft panel. The failed joystick was only five months old. The chief officer and all the bridge crew were well aware of the platform's restricted area. There was never any deliberate intention to enter into it. The above case raises following questions:

1. Are all officers and DPOs on our vessels aware of the restricted zone on the rig they are operating with?

2. If so, why this restricted zone specified and did we ask the rig to share the installation data card?

3. Is this installation card posted on the bridge?

4. The chief officer thought that, when he experienced the slackening of the joystick, it had undermined its operational effectiveness; this was later proven not to

be the case. He instinctively decided the most suitable course of action was to pull off the installation immediately and vacate the 500m zone by the shortest route. On the premise that he believed the joystick had failed completely. Is this action by the Chief Officer correct? Would you act in a different way?

5. The decision was made to pass over control from the aft console to the forward console during the exit from the 500m safety zone. Do you think this decision is correct? What would you do in such a situation?

6. The chief officer has stated that, with hindsight, he should have continued to thrust to port and exit the 500m zone by that means before attempting to pass control. Do you agree with this given the status of Joystick? If so why and if not why?

7. Please read the statement carefully The second officer, on taking control on the forward console, noticed that the rudder indicator was over to starboard, although he could not confirm whether it was one rudder or both or exactly how may degrees to starboard it was showing. He realized that, if he applied ahead propulsion before putting the rudders to port, it would only aggravate the situation and increase the rate of turn to starboard. Would the situation be better served if the 2nd Officer had put the rudders to port and then applied the ahead propulsion? What maneuver would you adopt if you were in that situation.

Please list your Recommendations: Do we need any changes to our procedures in

light of the above. Please check the operational modes (i.e rudder

angle and pitch) of the propellers, thrusters and rudders upon changing over controls from DP to aft console; aft console to forward console and forward console to aft console. Do we need this information displayed on the bridge.

Compiled using information from the Marine Safety Forum