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General arrangement 120 ton bollard bull AHTS

October 6, 2005

MAN B&W packages for Swire AHTS's

MAN B&W Diesel is to supply complete twin-screw medium speed propulsion packages for six 120 ton bollard pull Anchor Handling Tug Supply Vessels (AHTS).

The vessels will be built at the Batam, Indonesia, yard of Singapore's Labroy Shipbuilding and Engineering and will be operated by Swire Pacific Offshore Limited, Singapore.

The first newbuilding is scheduled to be launched at the beginning of 2007, and the following vessels are planned to follow at two month intervals.

The vessels have been designed by U.K.-based IMT Marine Consultants Ltd, with specific optimization for the worldwide operation of Swire Pacific Offshore activities.

Steven Birdsall, Senior Sales Manager of MAN B&W Diesel's International Offshore Group, says there were three decisive factors in Swire's choice of MAN B&W Diesel:

- The ability to procure a total propulsion package from the same manufacture, which included the main engines, gearboxes, shafting, propellers, nozzles and the propulsion control and management system.

- The capability for the same series engine to cover all propulsion power requirements on varying-sized AHTS's (60 to 120 ton bollard pull) allowing the possibility of interchangeability of spare parts and trained engineers, whom could be transferred from vessel to vessel.

- MAN B&W's willingness to tailor a perfect matching propulsion package, tuned to meet Swire's specific operational requirements for present and future projects."

Principal Particulars - 120 ton bollard pull AHTS

Length OA 66.0 m
Length BP 57.0 m
Breadth 16.0 m
Depth 7.30 m
Draft 6.20 m
Deadweight 2,100 t
Propulsion 2 x MAN B&W 9L27/38-VBS packages
Classification ABS Class +A1, Offshore Support & Towing Vessel, +AMS, + ACCU

Propulsion Package

A total main engine output of 2 x 3,285 kW will supply the propeller thrust, for a bollard pull of more than 120 metric tons. The ship service speed is optimized for 13.5 knots.

The MAN B&W Diesel twin-screw Alpha Propulsion System type 9L27/38-VBS, which has been specified for the newbuildings, includes:

Main Engines

Two MAN B&W 9L27/38 engines, fitted with full engine power PTO and integrated journal bearing at the front-end, driving a fire-fighting pump arrangement.

Reduction Gearboxes

Two MAN B&W Alpha AMG55 gearboxes, type 57VO55EV, with a speed reduction ratio of 800:141. Additionally, each gearbox is equipped with a 1,800 r/min PTO shaft for a 1600 kVA shaft alternator.


Two MAN B&W Alpha type VBS980 four-bladed controllable pitch propellers. The 3,800 mm ducted CPP systems are complete with tail, intermediate shafts and bearings, stern tube equipment, and MAN B&W fixed propeller nozzles type AHT.

Control System

In addition to the engine room control station, the Alphatronic 2000 Monitoring, Control and Safety System includes a main bridge control station and an aft bridge slave control station. The propulsion control is interfaced to a Joystick/Dyn Pos System, which manages the overall ship maneuvering via gyro compass, rudders and thrusters.

Port side propulsion arrangement