Robert Allan Ltd. Develops a Comprehensive Design Package for ITB Marine Group’s New ATB Push Tugs

October 19, 2016

The ITB Marine Group Ltd. (ITB) is currently well into construction of the first of two, twin Z-drive, ATB pusher tugs for service on the West Coast of North America. The tugs are being built at their Annacis Island Shipyard near Vancouver. The tugs will be connected by an articulating pin system to the existing double-hulled oil barges ITB Reliant and ITB Resolution which will receive retrofitted pin ladders and stern extensions for connecting to the new tugs.

ITB had a well-defined statement of requirements for the tugs and a relatively clear vision of the desired layout. Accordingly, the general arrangement for the tug was developed in close collaboration with ITB Marine Group’s Chairman of the Board Captain Bob Shields.

Robert Allan Ltd.’s engineering team, led by Todd Barber, P.Eng. then supported ITB with the development of a very detailed and comprehensive design, engineering, and support package, which included:

  • Hull form optimization study using Computational Fluid Dynamics (CFD)
  • Extensive group of design drawings
  • Detailed resistance, propulsion, propeller design, and pin loading studies, again using CFD
  • Complete production design package as well as assistance with jigs for ITB’s yard
  • CFD manoeuvring studies to assist in developing the simulator model for training the operators
  • In construction support

The efficiency of various hull form options was investigated early on in the design process using CFD and resulted in the selection of the current relatively low depth to beam ratio hull form. This choice yielded excellent efficiency in a relatively easy to construct hull form.

The extensive design drawing package included the standard structural, machinery, and piping drawings but also included many detailed drawings such as stair construction details, ladders and railings drawings, detailed window and door schedules, loose tank structural drawings, anode arrangements, manhole arrangements, etc. These all support and assist ITB with a very high level of design and engineering and ensure a smooth building process.

CFD analysis was used extensively for many aspects during the design process:

  • Tug/Barge notch optimization
  • Resistance and propulsion
  • Verifying pitch of propellers
  • Verifying ATB connecting pin loads

Robert Allan Ltd. provided ITB with the complete production design package including definition of all steel parts and piping spools. Steel part NC cutting files provided all edge prep information and markings so that parts arrived at ITB’s yard “ready to weld”. The piping layout was worked out in 3D in close collaboration with ITB to ensure all of their maintenance and operational goals for the tugs were achieved at the “virtual” stage before construction commenced.

Inboard Profile Cutaway View of the Tug

Inboard Profile Cutaway View of the Tug

CFD was once again used to determine the manoeuvring characteristics such as crash stop distance, acceleration, turning circles, and zig zags. This information is being used to configure the simulator for training ITB’s operators on the new vessels.

Turning circle simulation in CFD

Turning circle simulation in CFD

Turning circle simulation in CFD

Turning circle simulation in CFD

The completed tugs will measure 24.90 m by 12.50 m x 3.65 m depth, have a fuel oil capacity of 99.8 m³ and a fresh water capacity of 14.4 m³. They will be under 24 m registered length and under 400 GRT. Propulsion machinery will comprise Cummins KTA 38 main engines each delivering 634 kW (850 BHP) @ 1800 rpm connected by Centa hollow carbon fibre floating shafts to Rolls Royce US 105 P9 12FP Z-drives with 1.6 m propellers and with integral slipping clutches. The ATB connection pins are Articouple model FRC 35S designed for 3m significant wave height. These are rated to permit the tug to stay in the notch during all loading/offloading operations by allowing relative vertical movement of the tug and barge while still connected. The fully air -conditioned and MLC compliant accommodations are laid out to a very high standard for a crew of up to 8 persons, with a spacious and bright mess/ lounge area, large sized cabins with en-suite facilities, and a good sized fitness room.

The tug is designed to Lloyd’s Register Class requirements and for Transport Canada compliance with the following notation: LR ✠ 100 A1 Tug, MCH, IWS, UMS

Robert Allan Ltd. is supporting ITB throughout the construction process with engineering assistance as and when needed by ITB. The first tug is starting to take shape at ITB’s Shipyard with delivery expected early in the second quarter of 2017.

These two new ATB units will significantly raise the bar for coastal transportation in terms of efficiency, safety, and crew comfort. For more information on these innovative new pusher tugs, or any other high-performance vessel designs developed by Robert Allan Ltd., please contact