Jensen designs two new Crescent Towing ASD tugs

DECEMBER 2, 2014 — Jensen Maritime, Crowley Maritime Corp.'s naval architecture and marine engineering firm, is providing customer Crescent Towing of New Orleans, LA, designs for two, new Azimuthing Stern Drive (ASD), 5,360 horsepower tugboats.

The 70 metric ton bollard pull tugs, which will be built by Steiner Shipyard, Bayou La Batre, AL, will be able to operate in a variety of modes making them capable of towing, ship assist and escort duties.

The vessels will have Tier 3 GE 8L250 main engines and Rolls-Royce US 255FP Z-drives.

The designs are based on Jensen's existing 92-foot ASD tug design, which has been driven by vessel performance and construction efficiency.

The tugs are the fourth and fifth vessels Jensen has designed for Crescent, with the most recent design having been delivered in 2010.

"The high horsepower and compact, deep-draft design of the 2010 tug allows us to better serve a wide variety of our customer's current and future needs in all aspects of ship assist," said Keith Kettenring, Crescent Towing's executive vice president.

Improvements made in the new designs will yield more horsepower and increased stability during the tugs' operation. Additionally, a modified staple placement is expected to increase steering forces by approximately 30 percent. To accommodate this increase, the tow point will be lowered and allowed to move further off center, increasing stability in working modes. Increased brake tension on the bow winch will also accommodate the increased steering forces. Finally, in the new design, tankage is divided to better control liquids on board, which will also improve stability and trim control.

"Horsepower is important for safety due to the increasing size, tonnage and draft of the ships calling on our ports now and in the future," said Mr. Kettenring. "Horsepower is needed to better control these ships to avoid accidents and environmental casualties."

"We customize each of our vessel designs to suit our customers' needs," said Johan Sperling, vice president, Jensen. "Jensen's capabilities really excelled on this project as we were successful in finding ways to improve both the efficiency and performance of this tug for the customer."

For this project, and many others like it, the naval architects at Jensen took functional design to the next level by incorporating all the details of the structural, electrical and mechanical and HVAC systems into a full-size 3D model through a process called production engineering. This resulted in a virtual vessel that could be inspected early in the design process for safety, maintainability and constructability. Jensen provided Crescent Towing all the structural assembly drawings and part nests (construction blueprints), that will drive the process of cutting and laying out steel pieces to minimize waste during construction of the new tugs.

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