The Stevns Power photographed by Oddgeir Refvik.

On 19th October 2003 the Anchor Handling tug Stevns Power was lost with all hands in calm conditions while supporting the pipelaying vessel Castoro Otto offshore Nigeria. The circumstances surrounding this event were investigated by the Danish Authorities, whose report was published in June 2004. The only response by the marine press seems to have been 200 words on page 6 of the NUMAST Telegraph, the first paragraph of which states “A report on accident in which an anchor-handling vessel sank in just one minute off Nigeria has raised concerns about commercial pressures.”

This article is therefore intended to provide a little more information and to assist those engaged in such tasks to operate safely.

 The Castoro Otto is a ship shape vessel built in 1976. It is almost 200 metres long and has a heavy lift crane on the aft end. It is owned by the Italian company Saibos Construceos Maritimas. Its task off Nigeria was to lay pipe in 75 metres of water.

There are a number of ways in which pipe can be laid and that employed on the Castoro Otto was the most traditional. The pipes are transported to the vessel in lengths and craned aboard from the attendant supply vessel, thereafter the lengths are welded together and are deployed over the stern on a fabricated ramp known as the stinger. In order to keep the production line on the move the vessel is eased slowly forward by means of its moorings.

The Castoro Otto has twelve anchors, so the contracted anchor-handling tugs must  move the anchors forward one at a time. Two vessels are usually employed, one on each side and they are constantly lifting anchors, being heaved in towards the ship then re-running them on a new heading.

On 19th October the Stevns Power was running anchors on the port side of the ship, and the Maersk Terrier was working on the starboard side. On the Castoro Otto the winches are actually operated from the Bridge and a crew member is positioned on deck adjacent to the winch being operated to inform the winchdriver if things go wrong. The Stevns Power had picked up No 10 anchor, and it was being recovered towards the pipe-layer. The actions of the tug are slightly different depending on which anchor is being deployed. The two forward anchors lead virtually ahead, and the two aft anchors virtually astern. In these cases the tug picks up the anchor and moves in the direction of travel of the pipelayer. In the case of the beam anchors the tug lifts the anchor from the seabed and the Castoro Otto then heaves the anchor in until the wire is virtually off the seabed. Up to now the tug has been stern on the the pipelayer, but when sufficient wire has been heaved in it will turn in the direction of the new anchor position and begin to move in the direction of travel of the pipe. Soon there-after the winchdriver will begin to pay out the wire. This action saves a minute or two in the operation.

Also present at the location was the pipe carrier the Oil Traveller which was tied up the the Castoro Otto on the starboard side and the survey vessel the Inspector which was trailing astern of the pipe layer checking the pipe on the seabed with an ROV.

The report on the loss of the Stevns Power states that at 1705 the tug had lifted No 10 anchor off the seabed and that the mooring was being recovered at 1710. At 1715 the Stevns Power began to move towards the new anchor position by canting the ship to port with the intent finally of moving astern in the direction of travel of the pipe.

At this time the report states that “the Third Officer (at the winch) saw that the Stevns Power began to heel over to port side and a bit to the stern. Thereby the Stevns Power got a more aft trim.”

The 3rd Officer spoke to the bridge telling them to stop heaving because it was apparent to him that the tug was in trouble, and the winch operator immediately stopped the winch. However, the report goes on to say that the Chief Officer “saw that the Stevns Power heeled over to port and was taking in water on the aft deck in the port side. Immediately after Stevns Power heeled over to one side and sank very fast with the stern first.”

There were no survivors.

The Stevns Power, and its sister ships are well known to everybody who has worked in the marine sector of the offshore industry. It was originally the Maersk Beater and together with five sister ships supported pipelayers and exploration rigs from 1976 onwards. They were a ship type which was briefly in favour because due to their small size and relatively high power, they were able to carry out anchor-handling operations faster than the conventional anchor-handlers of the period, which always had trouble with windage, and deck length. One of its sisters, the Maersk Battler was the first ship to grace the pages of this website in 1998. Later the Stevns Power was photographed by Oddgeiri Refvik for us when it was at the Seaway Falcon off Egypt. The latter photograph was been used by the Danish media at the time of the event and in fact in the Danish Government report (All without permission).  

The crew of the tug consisted of three Danes, six Phillippinos and two Congalese. The Master had considerable experience in the business, the Mate was on his first trip on an offshore vessel and the Navigating Officer (2nd Mate) was on his second trip on the Stevns Power.

Both the Engineers and the Motorman were from the Phillipines and all had served on anchor-handlers before, two of them having undertaken several trips on the Stevns Power. One of the ABs had also done a previous trip on the ship and the Cook and the Second AB had just signed on.

The two Congalese were required to be there by the Republic of Congo, part of the usual agreement in Africa to employ persons native to the country where the units are operating.

Lacking anyone to talk to from the ship the Danish investigators interviewed personnel from the other anchor-handler, the Maersk Terrier, the Inspector and a number of former Masters of the ship and some other Danish anchor-handler masters.

The results of these discussions and the interviews with the crew of the Castoro Otto, indicate that the Stevns Power was probably trimmed too far by the stern and that the engine room escape hatch at the port aft corner of the ship was probably open.  The mooring was being recovered at high speed and on a number of occasions including the day of the accident the Stevns Power had indicated to the Castoro Otto that the recovery speed of the moorings gave them problems.

From the various calculations and observations which too place the Danish investigators have determined that the speed of recovery of the mooring resulted in the Stevns Power travelling astern at a speed of between 6 and 8 knots.

In all accidents there are many factors which must be concurrently in place for them to occur. We usually suggest during our major accident risk assessments that overtaking a bus on a blind right hand bend is not in itself dangerous. There has to be a vehicle coming the other way.

The factors to be considered and in the case of the Stevns Power included the  following – in no particular order:

The tug was trimmed too far by the stern, giving little freeboard at the roller.

The speed of recovery of the mooring was extremely fast.

The Safety Management System of the Company did not mention anchor-handling.

It is possible that the rudders went hard over due to the influence of sternway.

It is possible that the Master of the Stevns Power failed to react by operating engines or the winch when problems started.

The Chief Officer lacked necessary training in anchor handling.   

But regardless of all of the above there was a single factor which could have prevented this terrible tragedy. This is stated in the report as follows:


 You guys out there, remember the first principle KEEP YOUR SHIP WATERTIGHT.

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