96037 Tanker Aground

Tanker Aground
Milford Haven

Report No. OR06

The UK MAIB have published a report on their investigationinto the grounding of the tanker BORGA at Milford Haven on the 29 of October1995. The following is a précis of that report. It is interestingto note that, while there was no pollution caused as a result of this accident,the result of the SEA EMPRESS going aground in the same area a few monthslater caused one of the worst spills ever.
During the morning of 29 October 1995 the Norwegian motor tanker BORGAran aground in Milford Haven whilst under pilotage. The weather was goodwith a south-easterly force 3 wind and clear visibility. At the time ofthe accident the vessel was loaded with 112,180 tonnes of crude oil, butalthough the vessel's hull was damaged the cargo tanks remained intact andthere was no oil pollution. She is not a "double hull" tankerbut is constructed with segregated ballast and double bottom tanks.

Two attempts were made to pull the vessel off using tugs, but both wereunsuccessful. A third attempt after the vessel had been lightened by 8,500tonnes of cargo was successful and she was refloated. The bottom hull platingand framing suffered varying degrees of torn plating and scraping damageon both sides of the bow. Additional damage, including minor plate tears,was found on the port side in way of the bulkhead separating Nos 2 and 3double bottom ballast tanks.

The cause of the grounding was due to a failure to compensate quicklyenough for the vessel's rate of turn to port by applying sufficient starboardhelm following an alteration of course. The helm was put hard-to-starboardas soon as it was realised that the vessel's head was continuing to turnto port. Also astern propeller pitch was applied, bow and stern thrusterswere activated and both anchors were let go. Despite all these actions thevessel ran aground at 0755. BORGA had the manoeuvring characteristic that,although her head turned to port when her propeller pitch was at full speedastern, her head turned to starboard at slow speed astern.

During the lightening operation on the afternoon of the 29 October, theChief Engineer discovered that the mechanical coupling between the electricmotor and the hydraulic pump on the starboard steering gear had sheared.It is not known when it had sheared because the alarm system fitted to thehydraulic system is activated by an electrical failure and not by individualpump outlet pressure.

Recommendations have been made with a view to ensuring that the provisionsof the International Chamber of Shipping's "Bridge Procedures Guide"are more closely followed, and for consideration to be given to extendingthe existing steering gear electrical power failure alarm required by SOLASto include a low hydraulic pressure alarm.

Narrative

The day before the accident, the Chief Engineer noticed during his roundsof the machinery spaces, that small amounts of metallic dust and oil werepresent around the base of the starboard steering gear electric motor. Asthis was not considered to be unusual, a more detailed inspection was notcarried out. With the vessel's arrival off Milford Haven expected earlythe following morning, the standard EEC Tanker Check List, Ship/Shore SafetyCheck List and the Company vessel pre-arrival checks were started. Whilstthe vessel was waiting until the agreed pilot boarding time, the enginecontrol room was manned by the Duty Engineer and a rating and the vesselmaintained a position off the coast using the starboard steering gear onautopilot. At 0600, the second or port steering motor was started and thesteering was changed over to manual. All four generators were then placedon line and the three transverse thruster motors started.

With the helmsman on the wheel and the day watch turned to, the anchorswere cleared away ready for port entry. At 0700, the signal station wascontacted and the vessel turned towards the pilot boat, course and speedbeing adjusted as necessary to make the 0730 rendezvous. The Chief Officercame on the bridge at 0700, checked and completed the pre-arrival checklists as well as plotting the vessel's position on the chart. The Pilotarrived on the bridge at 0732 when the vessel was on a heading of 0320 (T)with the propeller pitch at 30% ahead. During pilotage, it was usual practiceon the BORGA for the Master to operate the main engine controls and forthe Chief Officer to record the engine movements in the Bell Book.

The Pilot, after receiving confirmation from the Master that the vesselhad no defects, asked for "Full Ahead" and a minimum of 10 knotsfor passing between the buoys. The Master increased the pitch to 60% andthe vessel slowly increased speed on a heading of 0360 (T) towards the entrancechannel to Milford Haven. At 0735, the vessel's speed was in the order of5 knots and still increasing, the pitch having been increased to 80%. TheChief Officer ascertained the position of the vessel at this time usinga manual radar bearing and range of Turbot Bank Buoy and plotted the positionon the chart. At 0740, another position was plotted on the chart with thevessel still on a heading of 0360 (T); the course was then adjusted to 0270(T). At 0745, with the vessel on a heading of 0260 (T), a further positionwas obtained using Middle Channel Rock.

At 0746, the vessel was entering the West Channel with a speed of 9.12knots over the ground, the pilot ordered a starboard alteration of courseto 0400 (T). As the vessel came onto the new heading the helmsman appliedabout 50 of port rudder to stop the vessel swinging as she steadied on thenew heading. The Master, who was standing by the engine controls, notedthe new heading and that the helmsman had responded correctly to the Pilot'sinstructions, the vessel taking up the new heading without any apparentdifficulty.

After they had been on the new course for about two minutes, the vesselsuddenly started to turn to port causing the helmsman to apply between 50and 100 starboard helm to correct the vessel's swing. The Chief Officerhad fixed the position of the vessel at 0749 using a manual radar rangeand bearing of Middle Channel Rock and was plotting the position on thechart. The Pilot asked the helmsman if he was coming to port and instructedhim to apply starboard helm, to which the helmsman replied that starboardrudder was already on. The Master, hearing this, noted that the rate ofturn indicator showed a high rate of turn to port. He was of the opinionthat the bow was moving rapidly towards Mill Bay buoy although the rudderindicator was showing between 400 and 500 to starboard. As a precautionarymeasure, he applied 60% astern propeller pitch. The Master checked the rudderindicator on the steering console and increased the starboard helm to 600.At the same time he observed a decrease in the rate of turn to port, watchedit steady and then again increase to port. While the Pilot was calling thesignal station on his VHF and informing them that the vessel had "acomplete loss of steering....", the Master using the portable VHF set,called the First Officer and told him to go forward immediately and letgo the anchors. The Pilot ordered hard to starboard.

The vessel continued to swing to port despite the fact that 600 of starboardhelm was being applied. The Pilot ordered full astern. The Master put theforward transverse thrusters full to starboard, the stern transverse thrusterto port and at the same time, pulled the main engine control back to fullastern. At 0753 the Pilot told the signal station that the vessel was aboutto go aground. The First Officer having arrived on the forecastle, let gothe port anchor first, followed by the starboard anchor. The weather atthis time was still force 3 with a northerly tidal stream of about 0.6 knots.At 0755 a further call was made reporting that the vessel was aground. ThePilot also asked for the Marine Pollution Control Unit to be advised ofthe situation.

Findings

• The primary cause of the grounding was the delayed removal of port helm which the helmsman had applied in order to return the vessel to the required heading and of which the Pilot, the Master and the Chief Officer were all unaware.
• The amount of port helm applied by the helmsman may have been reasonable in the circumstances. However, the manoeuvring characteristics of BORGA were such that even a short delay in removing the port helm required a significant amount of starboard helm to effectively reduce the rate of turn to port.
• It is possible that the helmsman failed to appreciate his delay in removing the port helm and considered that his application of 100 starboard helm after a course alteration of possibly only 30 would be sufficient to effectively arrest the turn to port.
• By putting the propeller pitch in the astern mode the rate of turn to port increased due to the manoeuvring characteristics of the vessel.
• It was reasonable for the Master to engage astern propulsion to reduce speed due to the closeness of the land and the speed at which it was being approached.
• Although the Master attempted to reduce the rate of turn to port by increasing the starboard helm, the increased angle would have lessened the effectiveness of the rudder response by reducing the side thrust.
• The Pilot correctly ordered starboard helm after the vessel had started turning to port.
• When the rate of turn then started to increase again the Pilot, with good reason, ordered full astern in an attempt to reduce or eliminate the consequences of a possible grounding.
• It is unlikely that the rapid turn to port was initiated in any way by the effect of hydrodynamic interaction.
• The appointment of an additional bridge watchkeeper would have permitted continuous close monitoring that the required course was being steered accurately, in accordance with ICS "Bridge Procedures Guide", and might have enabled the delayed removal of port helm to be recognised and reported,
• It is possible that more effective use could have been made of the anchors in reducing the speed of the vessel had appropriate personnel been stationed forward in readiness to drop the anchors immediately if required.
• The effect of the starboard steering gear drive coupling failure was to reduce the speed of the rudder response, it was not in itself a contributory factor in the grounding of the vessel.
• Although the steering gear alarm system as installed complied with SOLAS requirements, it did not detect the failure of the drive coupling between the electric motor and the hydraulic pump.
• BORGA's manoeuvring characteristic of her head turning to starboard on slow speed astern, and turning to port on full speed astern, were not noted on the Pilot Card. Neither did it give an indication of the maximum rudder angle for the most effective vessel response at high and low vessel speeds.
• I was surprised to read that the vessel was enteringharbour with no-one available on the fo'c'sle to drop the anchors immediatelythings started to go wrong. This is surely essential on any vessel, letalone a laden tanker, even if the crew numbers are at a minimum level. Theother surprising procedure on this vessel was that in addition to his otherduties, the Chief Officer was required to keep the "Bell Book"on the bridge. Which is more important monitoring the other membersof the bridge team to prevent an accident or record the time that it happens?Recording time is important but this can now be done electronically.