Page 61: of Maritime Reporter Magazine (October 1994)

U.S. FERRY PROJECTS UPDATE

Cy

Washington State Ferries

Design of Washington State Ferry's Jumbo Mark II passenger and vehicle ferry.

When the Washington State

Ferry System selected a synchro- nous, variable-speed AC motor with a cycloconverter drive for the pro- pulsion system on its three new

Jumbo Mark II ferries, the ships became the first public transporta- tion vessels to utilize the technol- ogy. A cycloconverter system is typi- cally used in situations requiring medium to high power (2,000 kW to 20,000 kW), slow speed (0 to 1,000 rpm), and where excellent dynamic response and precise speed control is necessary. It can accommodate rapid changes in direction and speed, deliver full power in both forward and reverse, and can apply full torque at any rpm supplying maxi- mum available power to the shaft.

To date, heavy industry has been the main user, but cycloconverter technology is making headway in the marine industry, first on ice- breakers where its high power char- acteristics won favor, and on cruise liners, where the electrical load re- quirements exceed the propulsion load. Utilizing a single electric gen- erating plant to supply both loads reduces the number of diesel power sources in the engine room, saving both space and money.

The Washington State ferries ac- commodate nearly 30 million pas- sengers annually. The complex to- pography of the Puget Sound re- gion makes ferry transportation es- sential for the citizens, and a chal- lenge to system officials. Reliabil- ity, high- and low-speed maneuver- ability, instant dynamic response, as well as high power capabilities are required elements on the state's car ferries. The unique structure and operating practices of the ves- sels further complicate propulsion system designs. The ships are double-ended to eliminate time-con- suming backing and turning around procedures. Cars drive straight through the vessels entering on one end, exiting on the other. All of the vessels maintain two pilothouses, two engine rooms and two self-con-

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Circle 327 on Reader Service Card Circle 332 on Reader Service Card tained propulsion systems. At the end of each run, the captain walks across the deck, enters the opposing bridge, switches over the controls, and pulls forward out of the slip.

There is a propeller at each end of the vessel, separate drives, and two motors in series on the shafting.

Each ship carries four diesel genera- tors, two per engine room. To main- tain the system's tight sailing sched- ule, docking time must be kept to a minimum. Vessels approach the dock at full speed, stop quickly and ma- neuver into the narrow slips unas- sisted. A double propeller/double rudder system gives them full lat- eral movements when needed. While underway, most of the power is de- livered by the stern propeller with just enough power to the bow pro- peller to keep it from impeding for- ward progress. The bow propeller is used to stop the boat, as it can do so faster than the stern propeller going in reverse. (Continued on page 4i

Blohm + Voss AG

Awarded Washington

State Ferry Contract

Blohm + Voss AG of Hamburg,

Germany has been awarded an order for sterntube seals and, sterntube bear- ings by Bird-Johnson Co. of Seattle, for delivery to Washington State Ferries

Jumbo MKII ferries project.

Washington State Ferries has cho- sen Simplex-Compact Multisafe four- ring seal with ceramic-coated liner and the leak-proof system to give the re- quired environmental protection.

With more than 40 years experi- ence in the design and manufacture of sterntube seals, and with more than 34,000 seal units sold, Blohm + Voss reportedly said it was proud to be associated with this prestigious project.

For more information on

Blohm + Voss

Circle 25 on Reader Service Card 48 Maritime Reporter/Engineering News