Caterpillar Announces New Marine Diesel Engine Application Guidelines

Caterpillar Engine Division has revised marine propulsion rating definitions to simplify selection and help insure proper application.

The following four-level rating system matches Caterpillar marine propulsion systems to a particular application based on vessel operation: • Continuous—For service with full-throttle operation up to 100 percent of total time; • Medium Duty—For service with full-throttle operation up to 80 percent of total time with balance of time below rated rpm; • Intermittent—For service with full-throttle operation up to 50 percent of total time with the balance of time below rated rpm; • High Performance—For service with full-throttle operation up to 5 percent of total time with the balance of time below rated rpm.

Use of the correct rating based upon these definitions and guidelines provides optimum performance, long engine life, and extended overhaul periods.

In selecting a rating for a specific application, the most important consideration is the time spent at full throttle. The rating definitions identify the percent of time at full throttle and corresponding time at reduced rpm. This rpm reduction lowers horsepower requirements, as propeller demand follows a cubic speed/power curve.

For example, an engine operating at 90 percent of rated speed will be loaded by a typical propeller to about 73 percent of rated power.

Operating at recommended reduced speed controls the engine load at or below the continuous level. As a general guideline, typical operating parameters for each rating are summarized below: Ratings should be applied on the basis of vessel operation and not to an application based only on the type of boat or hull design. Vessel descriptions such as workboat, fishing vessel, or ferryboat, and hull design such as displacement or planing hull do not completely define the operation conditions of the vessel or the power demands required of the engine. These general conditions could have more than one rating applied depending on how the vessel is operated. It is important to remember that the rating selected should match the individual vessel operating profile.

For further information on these Cat guidelines, Circle 98 on Reader Service Card

Maritime Reporter Magazine, page 12, Apr 1984

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Maritime Reporter

First published in 1881 Maritime Reporter is the world's largest audited circulation publication serving the global maritime industry.