Rotortug infield support vessel details revealed

Construction of the ART 100-46 class Rotortug is described as ‘well underway’ at Damen Shipyards Sharjah, UAE and follows the earlier success for Rotortug in securing a significant order for three ART 100-42 infield support vessels to be built by ASL Shipyards Singapore for Shell’s Prelude LNG facility off northwest Australia (see MJ January 2017).

KT Marine Services Australia is a JV of Kotug International BV and Teekay Shipping Australia Pty Ltd and the order follows the awarding of a contract with ConocoPhillips to support its offshore operations in the Timor Sea.

Rotortug BV’s direction changed when it established an exclusive design contract with Robert Allan Ltd allowing the former to concentrate on development and marketing of the Rotortug and move away from the building element. The series can now be ordered through either party, the ART 100 series being the largest in the range but much more than just a beefed-up Rotortug ship-handling tug.

A look at the roles expected from the vessel illustrates the degree of complexity and is based on the demanding support requirements of the offshore oil and gas industry and includes: escorting, berthing and unberthing operations (over the bow or stern); tanker pull-back operations; anchor-handling; floating hose handling and maintenance; subsea support activities; fifi1 capability; pilot transfers; security duties and finally rescue and emergency evacuation capabilities.

The vessel will employ the standard Rotortug configuration of two azimuth thrusters forward and one aft, an interesting feature of which will see it achieve DP capability through the addition of a single transverse thruster aft. Quoted bollard pull figure for the 46m long vessel is 100 tonnes.

The bow and stern towing capability involves two powerful winches, the aft deck featuring a waterfall winch with both wire and synthetic ship-handling towlines with the foredeck home to a split-drum ship-handling and tanker pull-back winch. Deck machinery also includes: an 800mm diameter retractable towing staple, Kooiman Delta pins and fork, a stern roller, two tugger winches, two capstans and a deck crane.

It is designed for operation in ‘fairly significant environmental conditions’ with Robert Allan’s RAstar style hull-form being selected for its proven seakeeping performance in high sea states. It is stated the hull-form provides reductions in motion and accelerations compared with more standard wall-sided hulls. The design was refined during a model test programme conducted at the Vienna Model Basin with support from Robert Allan Ltd.’s CFD team to determine optimal appendage configuration balancing competing requirements for course stability, manoeuvrability, side stepping speed and resistance.

By Peter Barker