Cat® Marine EPA Tier 4 Engines Installed on McAllister Tug Duo



Environmentally conscious 3516E propulsion engines will power two azimuth stern-drive escort and rescue tugs destined for operation on the U.S. East Coast in milestone installation

Horizon Shipbuilding (Bayou LaBatre, AL) is in the process of installing the first production EPA Tier 4 certified units of its 3516E EPA CAT Marine engines, on a pair of tugs it is building for McAllister Towing & Transportation Co., Inc.

The pair of 100 foot azimuth stern-drive (ASD) escort and rescue tugs will each be powered by two CAT Marine 3516E EPA Tier 4 engines rated at 3,386bhp, supported by three CAT C7.1 EPA Tier 3 gensets rated at 118ekW and two CAT C18 EPA Tier 3 803bhp fire pump engines (Fi-Fi).  The equipment was delivered to Horizon Shipbuilding by Cat Marine dealers Thompson Cat and Foley Cat.

New York-based McAllister Towing & Transportation Co, Inc. said the new tugs would be among the biggest operating in its fleet and on the East Coast.  The first tug, the Capt. Brian A. McAllister (Hull 185), named after the company’s chairman, will be delivered in April 2017.  The second, the Rosemary McAllister (Hull 186), named after his wife, will follow in July.  The vessels will increase the McAllister fleet to 32 tractor units and will be its first Tier 4 tugs.

To meet the U.S. Environmental Protection Agency (EPA)’s more stringent Tier 4 Final emissions standards which came into effect this year, each 3516E engine is paired with a selective catalytic reduction (SCR) after-treatment system.  SCR uses a urea-based solution to reduce the oxides of nitrogen (NOx) contained in diesel exhaust down to nitrogen and water vapor.  The compact urea tanks on each of the McAllister tugs have a capacity 2,500 gallons.

Caterpillar’s SCR technology was specifically designed to comply with EPA Tier 4 as well as satisfying IMO Tier III emissions level requirements while minimizing customer integration impact and maximizing operating efficiencies.  “The 3516E shares much in common with the 3516C,” said Jason Spear, Caterpillar Marine 3500 Product Definition Engineer.  “Its advanced combustion design uses the optimum configurations and cylinder geometry, which enhances the back pressure capability, allowing the Cat Clean Emissions Module (CEM) to be the most compact and efficient SCR system on the market today.  Engineered from the outset for marine applications, the CEM offers versatile vessel integration options, serviceability, and lowest total cost of ownership.”

Throughout the installation process, CAT Marine has been holding regular design review meetings attended by Horizon Shipbuilding, Thompson CAT, and the CAT Engineering team.

“We are completely satisfied and fully appreciate the support we have received from Thompson CAT in helping us plan and design the Tier 4 urea system for the McAllister vessels,” commented Jesse Dunn, Horizon Shipbuilding Project Manager.

On delivery, the latest McAllister Towing tugs will be classified ABS Maltese Cross A-1 Towing, Escort Service, Fire Fighting (Fi-Fi 1) and Maltese Cross AMS.  With a bollard pull of 80 metric tons, the hull is designed for enhanced ship assist in addition to direct and indirect escorting.  The hull design was simulator tested to assist post-Panamax and ultra-large vessels.

In addition to confirming its environmental credentials, by opting for a Cat Marine solution, McAllister’s tug masters will benefit from improved performance and function resulting in more efficient workboat operation.  The 3516E’s electronic governing control unit minimizes fuel consumption and monitors engine operating parameters.  For user-friendly operation, the engine features an instrument panel with cold mode start strategy and programmable low idle.

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