Halter Completes Diesel Electric Supply Boat Contract For Acadian
The recent delivery of the Acadian Commander (shown right) and Acadian Explorer by Halter Marine, Inc., New Orleans, La., marked the completion of a six vessel contract with Acadian Marine Service, Inc. for the world's first diesel electric SCR tug/supply vessels.
The 217-foot w o r k b o a t s are powered by diesel generators supplying electricity, via a silicon controlled rectifier (SCR) system, to the ships' dc traction motors turning the propeller shafts. SCRs convert electricity from ac to dc and permit control over the dc output to vary the speed of bowthruster, tow winch, and propulsion motors.
Labeled the Mariner class after the lead ship Acadian Mariner, "the SCR vessels have introduced, and proven several new concepts in the design and operation of workboats for the marine transportation industry," stated Harold P. Halter, president and board chairman.
"Innovations like the SCR system itself, flexible horsepower, and engine room placement are just a few of the new ideas incorporated in the Mariner class," said Mr. Halter.
Up to five Detroit Diesel GM- 16V149TI diesel-powered 900-kw generators make up the flexible power system according to the horsepower demands of the charter. The skid-mounted generators are easily installed on prepiped and prewired foundations in a matter of hours.
The engine room on each vessel is located on the main deck level inside the forecastle. This arrangement allows easy access to the generators, has short exhaust runs, and eliminates the large engine room below deck for 30 percent more cargo area there. A relatively small compartment aft contains the Gulf Electroquip dc motors and Philadelphia gearboxes. Shaft brakes, reverse gears, and clutches are also eliminated since the electric motors handle those duties.
The Acadian Mariner was delivered in November 1978 with five generators onboard. The flexible horsepower concept allowed two generators to be removed when the vessel was chartered by the U.S. Navy Sealift Command since the 8,000 hp was unnecessary for work as a breakbulk and container carrier.
"We take the flexible power concept one step further," said Robert Jumonville, Acadian operations vice president, "by running only two of the three remaining generators whenever we're on schedule, the Acadian Mariner has experienced up to 35 percent fuel savings while still running at 12 knots." Operating in parallel, the generators supply ac power to a common bus, or power pool. Electrical needs are drawn from the pool either for ac service or fed to the SCR system for conversion to dc power. One generator provides enough power to turn both shafts for twin propeller handling and speeds up to eight knots.
When electrical requirements exceed the output of one generator another is put on-line, and another, until the load reaches the maximum capacity installed in the vessel.
"The extra generators remain idle until more horsepower is needed," explained Mr. Jumonville, "this obviously saves fuel and is the most efficient use of diesel engines." Diesels attached to generators run at a constant rpm and do not encounter the same resistance and loads found on conventionally powered vessels.
The Acadian Seafarer is operating in its full 7,200-horsepower mode with five generators and four traction motors as an oceanographic research vessel on charter to Texaco. The recently delivered Acadian Commander has also been chartered for seismic e x p l o r a t i o n by Digicon, Inc., Houston, Texas.
The underwater sound profile of the Mariner series is acous- tically lower than conventional supply boats due to the isolation of the diesel engines and subsequent lack of vibration. Large, quiet running vessels are favored as research ships because their low sound profiles do not mask the acoustical returns from seismic shots, said Mr. Jumonville. SCR vessels also have maximum torque available at all rpm for efficient towing of seismic arrays sometimes two miles long.
The 217-foot long vessels have a beam of 44 feet and a 16-foot depth. Each vessel displaces 2,400 tons loaded and is admeasured under 200 gross tons.
The Acadian Commander has a speed in excess of 13 knots turning two five-bladed, 108-inchdiameter stainless steel propellers inside foil-shaped kort nozzles. A bowthruster is powered by a GE-752 VDC electric motor. There are accommodations for up to 23 passengers and crew and, with alternate arrangements, up to 50 persons.
Pilothouse electronics include two Furuno radars, Drake SSB and Sailor VHF radios, Micrologic loran "C", Sperry a u t o p i l o t, R a y t h e o n depth recorder and magnetic compass.
The Mariner class vessels were built to American Bureau of Shipping classification A-l, Maltese Cross, full ocean towing, AMS, Circle "E" and ice class "C", by the New Orleans division of Halter Marine.