Page 56: of Maritime Reporter Magazine (April 2000)

Propulsion Performance Products "Diesel-electric drive conveys extraor- dinary freedom of configuration," says

DeJong. "Because the engines and gen- erators can go just about anywhere, you can place them forward and use their weight as trim ballast, creating more room for cargo aft." Forward placement also locates the engines close to the stacks, which shortens intake and exhaust plumbing. That lets the engines breathe, and therefore work, more easi- ly, with less exhaust back-pressure to overcome.

Versus controllable-pitch propulsion, electric drive can deliver equivalent per- formance with fewer moving parts.

Equivalent performance, because the propellers have full shaft horsepower on tap in all modes of operation. Fewer parts, because the system eliminates the valves, rams, and other hardware of CP hydraulics. Another advantage: multi- shaft maneuverability with only one engine running.

But that's not to suggest an either-or proposition. To the contrary, SCR-con- trolled dc motors can be. and have been, used to power CP propeller reduction gearing and virtually all other types of propulsion loads, from reduction gears with fixed pitch propellers to Z-drives to low-speed water jets and tunnel thrusters. The choice is a function of application. Which harks back to the original question of whether or not diesel-electric is the system for you.

Therefore, do consider SCR drive: • When propulsive power constitutes a small percentage of the total required for maneuvering, positioning, pumping, lighting, and so on: • when maximum torque and respon- sive control are necessary for dynamic positioning and bollard pull conditions; • when maneuvering agility, especially with rapid propeller reversals, is of para- mount importance; and • when physical criteria either preclude direct-diesel or render it cost-prohibitive - SWATH vessels with hulls or struts of inadequate size; sternwheelers and other vessels requiring forward-positioned machinery to avoid trim problems; con- figurations that would necessitate more than one machinery space to accommo- date direct-diesel, with a corresponding multiplication of cooling, intake, exhaust, ventilation, and control provi- sions.

And do consider it in spite of any con- cerns you may have about harmonic dis- tortion. Some vessel operators fear that, with a large electric plant, harmonic dis-

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Circle 312 on Reader Service Card

Circle 330 on Reader Service Card www.volmar.it £

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COMCOR Tech (NJ) 908 9798193 - Fax 908 [email protected] tortion reflected on the ac line could cause computers, navigating equipment and other sensitive electronic devices to malfunction. As Robbins points out, "It just isn't a problem. The potentially adverse effects of harmonic distortion are easily eliminated at the design stage.

The simplest and most economical method is to apply harmonic filters to the ship's sensitive equipment." By con- necting filters to these sensitive loads, instead of to the source, much less filter- ing is required to neutralize harmonic distortion.

As for the singular "don't": Do not consider an SCR drive system when main propulsion, particularly under con- sistent loads for extended periods, con- stitutes 80 percent or more of the total power demand. Only rarely will such applications gain much benefit from diesel-electric.

Circle 70 on Reader Service Card

Jeff McMahon is vice-president of Inter- nationa! Electric Company Inc., a

Houston, Texas-based manufacturer of

SCR drive systems for oil-well drilling and marine applications.

Drew Marine, MAN B&W

Launch Redesigned Fuel Mill

From left: Wilhelm Pape, MAN B&W manager;

Dieter Faustmann, Drew Marine regional mar keting manager: Jack Finnegan, manager of new business development for Drew Marine;

Nels Henrickson, Drew Marine vice president of marketing; and Peter Planitzer, MAN B&W manager.

Circle 247 on Reader Service Card 52

The Drew Marine Division of Ashland

Specialty Chemical Co. and MAN

B&W Diesel AG have launched produc- tion of redesigned Fuel Mill dynamic homogenizers through a new working relationship between the companies.

Under the manufacturing agreement,

MAN B&W will produce all of the homogenizers that Drew Marine pro- vides to shipowners worldwide for the full range of proven fuel-homogeniza- tion applications. In addition, MAN

B&W is integrating Fuel Mill units into its Fuel-Water Emulsification module.

Drew Marine's homogenizer is a milling machine equipped with concentric, cone-shaped gears with toothed surfaces that grind heavy fuel oil as it is pumped through the handling system. Drew

Maritime Reporter/Engineering News