CSS Sovereign - Cable Laying Ship

Hart Fenton and Van der Giessen were both able to bring their experience from the offshore market and the specialist ferry industry to combine with BT (Marine) Ltd's detailed knowledge of cable installation and maintenance vessels to create a unique and extremely capable vessel.

Hart Fenton undertook the initial design and specification and succeeded in achieving a vessel with a high degree of performance in adverse weather conditions.  Hart Fenton supervised the construction of the vessel at Van der Giessen.

The new ship cost £32 mill and enters service at a time when, according to BT Marine - BT(M), fibre optic cabling is being preferred to satellite communications. With an all- British crew of some 40 souls compared with 100 on the much older, actually 30 year old ship Alert that she replaces, she begins work in the North Atlantic on cable repair.

 BT Marine employs about 450 people and has a 140 year history which includes achievements in international cable laying. Laying the first UK-France cable in 1850 for example. The company was also involved in laying the first international subsea fibre optic cable in 1986. Today fibre optic cabling is taking over from the traditional cables.

In 1943 the world's first submarine cable amplifier, or repeater, was inserted into an existing cable between Anglesey and the Isle of Man, with the effect of immediately doubling the cable's capacity from 24 to 48 circuits.

 A 300 n mile cable with seven repeaters put under the North Sea between Scotland and Norway in 1954 was, at the time, the longest repeatered telephone line in the world. Two years later BT Marine went one better, laying the first transatlantic telephone cable between Scotland and Newfoundland.

Using special lightweight cable invented by its parent company, British Telecom, BT Marine laid the first all-British telephone cable beneath the Atlantic in 1961, linking the UK with Canada. 

The pace of technological progress quickened in the 1980s with the development of the fibre optic submarine cable. Capable of carrying far more messages and conversations than any other type of cable, it became apparent that the fibre optic cable was set to revolutionize global communications as the twenty first century approached. 

Then in 1988, BT Marine successfully installed the UK section of the world's first transatlantic fibre optic cable, Trans-Atlantic Telephone (TAT-8), linking the UK and France with the USA. Its 8000 circuit carrying capacity can be boosted to convey some 40 000 simultaneous phone calls using state- of-the-art Digital Circuit Multiplication Equipment (DCME). 

TAT-8 is the first of a new generation of fibre optic cables across the North Atlantic and TAT-9 which links the UK, France and Spain with the USA and Canada, was commissioned this year. There are plans for yet another system, TAT-10, due for completion in 1994.

A new ship needed

It was to ensure the maintenance of BT's position as a major player in cable laying and repair that a new ship was required incorporating all the latest advances in technology to allow her to lay or recover cable efficiently, and built to the latest international standards to ensure a useful working life of some 20 years. Why was she built in the Netherlands? Captain John Simkins makes no apology for this. "We put the order out to international tender. We received reactions from all over the world from some 27 yards asking for further details," he said. 

Captain Simkins is delighted with the quality of workmanship achieved by the Dutch yard which has kept the contract to schedule, and with its commitment to working as a team with BT Marine and the naval architects, Hart Fenton.

Design Considerations

The initial design of Sovereign was awarded to Hart Fenton & Co Ltd the British consulting naval architects in February 1988 and a final technical presentation was made to BT(M) in May 1988. 

The outline specification presented Hart Fenton with the challenge of submitting a preliminary design for a purpose built cable maintenance vessel which would be able to operate anywhere in the world. The vessel had to be able to perform well in difficult weather conditions while providing as safe a working environment as technically possible. It was determined at an early stage that the hull form had to be specially devised to minimise the motion of the ship at sea. 

Between September 1988 and January 1989 the consultants worked in close collaboration with BT(M) on the detailed design development, ensuring that the vessel would meet BT(M) 's requirements for a technically advanced cable maintenance vessel. Intended to operate as part of British Telecom's Atlantic Cable Maintenance Agreement involving other international telephone companies, the vessel has to contribute an emergency maintenance service for the repair of submerged telephone cables. 

Hart Fenton was awarded the contract to supervise construction of the vessel in November 1989, following a worldwide invitation to tender.

 Sovereign was ordered from van der Giessen-de Noord, Rotterdam in November 1989 and complies with the requirement of Lloyds »100 Al, ICE IC, CO, «LMC, UMS, DP (AM) PCR.

 Sea trials of Sovereign commenced in early October and these covered three main phases; the nautical operations, dynamic positioning, and cable trials which tested positioning, retrieval and maintenance of telephone cables. 

The Dynamic Position Control system in- stalled meets all requirements of Lloyds (AM) and Hart Fenton's trials endorse using the CEGELEC Simplex DP system.

 Sovereign is fitted with a CEGELEC DPS80 Simplex Dynamic Position Control system with independent back-up joystick, operable from the bridge. Processors in the system comprise a GEM80/302 micro-controller and associated input/output equipment which is capable of fully controlling the vessel. The portable joystick can interface to the DP system via one of four junction boxes situated around the vessel. 

The independent joystick system (US) comprises a GEM80/163 micro-controller which gives a reduced set of vessel control facilities.

 The following position measurement equipments are interfaced with the DP sys- tem:- - A Simrad HPR-309T ultra short baseline acoustic system with one tracking trans- ducer, - An Artemis Mk.lV radio positioning sys- tem, - Two CEGELEC Tautwire systems, one over the port side, one over the starboard side at approximately the midships position, and a universal radio interface facility. 

Sensors include two anemometers whose wind speed and direction signals are fed to the DP system to provide wind force compensation; two vertical reference units (VRUs). Both of which provide roll/pitch compensation for the radio systems (software dedicated). The VRUs are hardwired to the Simrad HPR Transceiver (via a switching arrangement enabling just one VRU to be connected at any one time) and provide roll/pitch compensation for the acoustic measurements.

 Two gyrocompasses provide synchro signals which are fed to the DP system to allow the vessel's heading to be sensed and control- led. The Gyrocompass signals are fed to the US system via a switching arrangement enabling just one gyro to be connected at any one time. 

The system includes the following control modes :- Joystick manual heading Joystick auto heading These modes are available at the DP con- sole, remote joystick and US panel. Dynamic positioning Model control Dynamic positioning with minimum power Track follow Auto pilot R.O.V. dynamic positioning Fast track These modes are available at the DP con- sole only

The US consists of a standalone cabinet housing the GEM80/163, with its associated I/O and a forward facing operator control panel which is mounted remotely from the cabinet.

 Peripheral equipment includes a Facit 4514 high speed dot matrix printer for alarm, event and statistics printout and a six channel pen recorder for continuous chart recordings of six parameters :- Fore/aft position error, port/stbd position error, heading error, bow thrust (filtered), stem thrust (filtered) and main propeller thrust (filtered). 

In addition a vessel simulator mode is selectable from a pushbutton on the DP con- sole provided that all thrusters are in MANUAL control. Simulation facilities are selectable from a simulation control panel in conjunction with the DP console simulation VDU display format. 

The dynamic positioning system is the heart of the ship and is what makes her so efficient in being able to maintain position and work on station in even a three knot current because of her reserves of propulsive power compared with other such ships. Sovereign is of course fitted with GPS which allows her position to be pinpointed any- where in the world within a few metres. This facility combined with her DPS station keeping ability is a formidable combination and when it is considered that cables are thou- sands of kilometres in length, the ability to lay without deviating from the required path is clearly a tremendous advantage.

A History of Expertise

Having said that, recently BT Marine needed to lift one of the earliest cables laid and not only found it to be in very good condition but also found it to be exactly where marked, it having been laid in position with the benefit of nothing much more sophisticated than a sextant and compass. That is of course not an argument against providing today ' s ships with the very best equipment available. 

On this question of the power installed in the ship, by comparison, whereas Sovereign can maintain station herself in a three knot current, Alert would require the assistance of tugs for anything in excess of a knot.

Design Features

Under normal circumstances the bow area is used for cable repairs and cable is laid over the stern. The vessel does of course have the usual distinctive bow and stern sheaves. On No.4 deck there are two French built, by Kley France S.A., cable drums which are driven by the action of eight hydraulic motors acting on teeth inside the wheels. To support the cable as it is run out from the tanks onto the drums and out over the sheaves there are provided tubular steel 'stools' that can be arranged at various positions about the deck and secured into place using webbing straps. 

For the repair and joining of cable, which needs to be done in clean conditions, especially in the case of fibre optic cable, there is located on the starboard side at No.4 deck level a workshop that can accept a loop' of cable from the work deck and can close doors around it to isolate the part being worked on from the rest of the cable. In order to super- vise cable operations in relative comfort there is provided an enclosed 'bridge' within the depth of No.4 deck which overlooks operational areas when the doors at the forward or after ends of the deck are opened. To minimise ship motions a flume type stabiliser is fitted. 

The after deck is particularly spacious, 580 m~, and looks enormous at present be- cause the 'A' frame has not yet been delivered; it not being needed at this time. 

A novel feature involves the stowage of the ship's own mooring lines. These are simply fed down a tube in the foredeck from where they are automatically fed to hawser bins. A sort of cable tank technology in reverse. 

Of course Sovereign is able to perform many more tasks than just cable laying duties. With her sophisticated facilities Sovereign can lay or bury control umbilicals, power cables and flowlines between offshore plat- forms and remote wellheads. She also has the potential to do work for the MoD and the Electricity Boards.

The Bridge

As could be expected visibility from the bridge, both fore and aft, is exceptional. It is also a very large area being the full length of the deckhouse. It is from here that the station keeping is mainly monitored and there is a comprehensive ballasting mimic diagram, full navigational and radio outfit plus an array of TV screens that can be used to monitor operations at various locations about the ship. 

Sovereign is propelled by a diesel electric system of two Brush 3045 kW/6.6 kV alternators driven by Stork Wartsila diesel engines type 12SW 280 3360 kW at 750 rev/min and a 4000 kW/6.6 kV alternator driven by a type 16SW 280 engine of 4485 kW at 750 rev/min. Although the engines are standard units, the high voltage diesel electric installation is rather rare in a vessel of this type. Computer controlled engine monitoring equipment based on Decca ISIS is fitted. Actual propulsion is by two Lips steerable nozzles fitted with 3100 mm diameter, four bladed propel- lers. These nozzles, of the S 2514 LSCP type are driven by two speed vertical motors. 

To aid manoeuvring and station keeping there are two Ulstein bow thrusters of the 375 TV type of 2150 mm diameter running at 288 rev/min. These develop 14.8 t of thrust.

Ship maintenance management system 

Consultants have supplied and implemented a computerized total ship maintenance management system for Sovereign. The fully integrated, PC based, system incorporates stock control, purchasing and costing; maintenance planning and resource management; plant condition base, history and defect analysis; and includes a sophisticated, easy to use, report generator. 

The system has been implemented as an adjunct to the BT Management Audit Pro- gram covering all aspects of the vessel's operation, cable, engine and deck machinery; communications, hotel, navigation and safety equipment; class and statutory certification. The system software, COMAC Delta, was selected for its capability of being upgraded to a fleet management system, COMAC EASE, when the individual ship databases can be communicated by satcoms or floppy disk transfer. 

Initially the maintenance planning (calendar and running hour based) will be run in parallel with a vibration monitoring program and eventually integrated within EASE.

 The stock management modules permit control of issues, reservations and purchase requests. Demands will be raised against a specific job or cost centre, where known items are required for a job a kit list may be compiled for automatic reservation of the items. For identification purposes system generated labelling is provided. 

The system will store and compile drydock/ refit jobs into a printed report which may be used as part of a tender document.

Ample work available