Jul 112011
 

Following a man-overboard exercise during which an ERRV has drifted farther than expected from an offshore facility the master, apparently ‘subconsciously’, set the vessel on autopilot. Tidal set put the vessel on collision course with the facility but the master, unaware that the vessel was on autopilot, was unable to regain steering and a contact incident resulted.

Says  Marine Safety Forum, MSF, has issued a report into the accident says: “Recently an ERRV made contact with a fixed installation causing some damage to the vessel and minor damage to the installation.The ERRV involved was configured with port and starboard 360°azimuth main propulsion units forward and an electrically powered 360° azimuth secondary thruster aft, The ERRV had been on location for 3 days before the incident occurred. The vessel had given over side work cover to the installation on numerous occasions over these three days. The vessel’s master had 25 years’ experience as Master and the previous nine years had been on ERRV. The Master had served on that particular vessel for five trips previous and was familiar with the arrangements. The ERRV had been set up with one main port azimuth thrusters and the after thruster, the starboard main thruster had been shut down and although ready to start was not running.
The ERRV was informed that over side cover would be required immediately after the departure of a Platform Supply Vessel (PSV) which was working alongside the installation. The Master of the ERRV decided he would have adequate time for a vessel initiated Man Overboard exercise, before the over side cover was required, and commenced the exercise. An FRC engine fault was identified and it was recovered. The exercise was completed with the deployment of the second FRC although due to the extended length of the exercise the ERRV had drifted substantially further from the installation than was originally intended.
Within minutes of the conclusion of the FRC exercise the PSV had left the 500 meters, and the ERRV was requested to attend for over side cover. Due to the greater than anticipated distance from the 500m zone the balance of probabilities would suggest the Master decided to engage the
auto-pilot for ease of transit and seemed to carry out this action subconsciously.
On approach to the 500m zone the Master then tried to stop the vessel using the manual control and turned the directional control and reduced thrust expecting the vessel to alter course and reduce speed so he could then stop on the outside edge of the 500 meter zone with the intention of
carrying out the pre-entry to 500m checklist. It was noted that the act of turning the thruster’s control had no effect and the vessel was still approaching the installation head on.
The Master’s initial perception was he had lost directional control of the azimuth thrusters. His initial reaction was to come astern, which would have been a suitable action on a conventional propulsion vessel to alleviate the situation. He turned the thrusters control astern and applied more
power to try and counteract the head way momentum of the vessel, still not realising the auto-pilot was engaged which in effect overrides the manual directional control of the azimuth propulsion; this did the opposite of the required affect and the vessel increased speed straight ahead toward the installation. The Masters next reaction was to contact the engine room to inform them he had no control and sent the chief officer to the engine room to inform the Chief Engineer. In the meantime the Master had applied the vessels after electrically powered thruster, which has much less available power than the forward propulsion units, to try and counteract the forward momentum and this resulted in the after thrusters overloading the electrical supply source and “blacking out”.

The Chief Engineer managed to reach the engine room and stop the port propulsion unit and start the Starboard one, this was not realised on the bridge and due to the auto-pilot still being engaged, if the Starboard thrusters had been engaged it may have only aggravated the situation. The Chief Engineer then proceeded to restore the electrical power arrangement. During this period the vessel which was now coasting on her own momentum, proceeded to make contact with the installation and came to a stop with the forward area underneath the platform. During the approach period the Master had maintained composure to inform the installation on the VHF prior to contact that contact was imminent.
Post contact the ERRV launched and FRC and went round the vessel looking for any signs of hull /Installation damage and found no signs of pollution or hull breach. At this time the Chief Engineerregained the electrical power configuration for the after thruster and it was engaged to “back” the vessel out from under the installation. The Installations umbilical’s were still wrapped around the vessel mast and some damage was caused to both the mast and the umbilical’s on withdrawal.
The vessel was then noted to be shipping water from the port thrusters unit, due to the impact and on “patching” the leak and confirming the pumps were coping was released to undergo an emergency dry docking and allow a full investigation to take place.
Critical Factors were identified as:

1. Perceived loss of functionality of steering and power to the Primary Steering / Propulsion System.
2. Non-use of emergency steering/propulsion system
3. Vessels track over the ground was influenced by tidal set and led directly towards the installation
The findings of the investigation were:

  • The initial heading towards the standoff point outside of the 500 metre zone should have had a greater offset from the installation to take account of the tidal effect. Looking at the vessels tracks there was a slight heading offset on approach that was cancelled out by the tidal effect. Had there been no environmental effects the vessel would have passed approximately 30 – 50m clear of the installation.
  • The vessel’s heading was being controlled by the autopilot, although the Master was not aware of it.
  • Finding himself in a quickly developing situation the Master concentrated on trying to slow down and stop the vessel by applying the stern thrust.

Other option available to avert collision were
1. Switch off autopilot and revert to manual control
2. Apply the emergency steering which would override the pilot and an off course alarm would have sounded an alerted the Master that the auto-pilot was engaged.
3. Apply the port propulsion unit’s emergency stop, which would have allowed the vessel to have been controlled from the stern thruster.

In light of the investigation recommendations the following actions have been implemented.
1. Issue alert to the industry of the lateral learning’s from the investigation
2. Formal Induction process for all bridge watch keeping officers should include familiarisation of all propulsion units and manoeuvring systems including actions to take in an emergency
3. Regular hands on practise to be carried out using emergency propulsion and emergency steering controls.
4. Vessel’s approach procedures to be reviewed to confirm that the vessel should have sufficient offset to prevent incursion into the 500m zone until the checks can be undertaken.
5. Review power management configurations to ensure that in the event of a primary system failure, alternative or backup systems are available.

Download the report/alert

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