Crowley Marine Services recently accepted the delivery of Alert — the first of a trio of new 140 ft. (42.6 m), 10,192-hp Prevention and Rescue Response Tugs (PRT's) under contract with the Alyeska Pipeline Service Company for use in both Valdez Harbor and Prince William Sound
The general purpose PRT's are powered by twin Caterpillar 3612B engines generating the combined 10,192-hp driving two Kamewa Aquamaster azimuthing thrusters. The tugs are also equipped for firefighting, emergency response and oil spill recovery
. Recent sea trial proved that Alert was able to generate a certified bollard pull of 300,000-lbs., and a free running speed in excess of 16 knots.
The entire PRT trio was designed by Guido Perla & Associates, and was constructed at Dakota Creek Shipyard in Anacortes, Wash. for Vessel Management Services, a Crowley Maritime Corp. subsidiary that owns and leases vessels. Encompassing an oil spill recovery and storage capability for up to 43,000 gallons of recovered oil, the tugs' design features include Schuyler fendering, and a Markey TDS-40 towing winch.
Designated primarily for tanker and general towing, the tug is equipped to serve as an emergency spill response vessel. Outfitted with two Desmi skimmer units, two 1,800 ft. oil spill containment boom reels and two Kvichak Marine 20 ft. (6 m), 250-hp aluminum oil spill response skiffs, the tug also holds double protective wing tanks of B/12 minimum breadth — provided for the complete length of the engine room.
Two firefighting foam concentrate tanks are able to hold approximately 4,700 gallons each, are installed over and above the ABS FFV1 requirements. Accommodating 16 people including spill response personnel in two single, five double and one quadruple berth staterooms, remaining accommodation spacing are situated with a galley and pantry with cold storage, ship's office and decontamination station.
Responsible for the design of this vessel series is Seattle-based naval architectural firm Guido Perla & Associates
(GPA), who took the responsibility for regulatory compliance by entering plans to ABS for U.S. and International Tonnage Certificates. The firm's engineers worked to perform the structural and mechanical calculations, electronic load analysis, and short circuit analysis and drew up a fire and safety plan. GPA engineers also created composite drawings with machinery and wiring layouts and piping routing for the equipment, ensuring that construction and operational maintainability was free of interference.
Prior to construction, an automated layout of the vessel confirmed mechanical capability, while ensuring a working view of towing operations from the pilothouse. This 3-D computer model of the complete design was formulated using the latest releases of AutoCAD, Rhino, AccuRender, as well as GPA-developed software. Exporting this computerized information to GPA's 40-station network allowed for development of hull scientific, structural, mechanical and electrical designs. The company provided lines fairing, lofting and numerical control NC tapes for automated burning and marking of individual parts.