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September 23, 2019   |   WorkBoat


Bisso’s new tractor tug: Tier 4 and Subchapter M

The challenge was to find the solution to comply with EPA’s Tier 4 strict emissions regulations, the Coast Guard’s Subchapter M requirements, and an increase in the bollard pull from 60 to 75 tons. Then the trick was to fit everything within the 98’ hull.

"To handle the increased power requirements we chose the proven Rolls-Royce Z-drive units and increased the size from US 205 to US 255. Then a decision had to be made with the type of NOx reduction system, all the while following the new Sub M requirements. We narrowed it down to two options, the GE’s EGR system and Caterpillar’s SCR system. We visited a GE Tier 4 complaint application on an Ingram towboat in Kentucky and a Caterpillar Tier 4 on a McAllister harbor tug in New York. Then after consultation with Main Iron Works and their naval Architect, Ashraf Degedy, the Caterpillar seemed the most likely arrangement to fit into our hull. Degedy and I visited the (Cat 3516E Tier 4, 110’) Caden Foss in San Francisco which sealed the deal. We took measurements of the extra equipment and Ashraf confirmed we could fit the package into our present hull. Then when I saw the tug working and operating from clutch to full ahead with no smoke, we were sold."

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