IMPORTANT NOTICE:
Twin Disc, Incorporated and Twin Disc Southeast
reminds users of these products that their safe operation depends on use in compliance with engineering
information that may be provided. Users are also reminded that safe operation depends on proper
installation, operation and routine maintenance and inspection under prevailing conditions. It is the
responsibility of users (and not Twin Disc, Incorporated) to provide and install guards or safety
devices which may be required by recognized safety standards or by the U.S. Occupational Safety and
Health Act of 1970 and its subsequent provisions.
MAIN GEARS - SERVICE
CLASSIFICATIONS
CONTINUOUS DUTY:
Often called "work boat duty", these marine
transmission applications are expected to operate continuously at full engine governed speed. The
propulsion engine power setting must be known and must be within the marine transmission's allowable
input rating for continuous day long or around the clock service.
Most displacement hull vessels are powered for Continuous Duty service. However, the actual engine
(and marine transmission) power loading depends on:
- The propeller used
- The vessel's work assignment
- The captain's choice of throttle setting during continuous service
Twin Disc recommends that all displacement and semi-displacement hull commercial applications be
classed Continuous Duty usage of the marine transmission.
INTERMEDIATE DUTY:
Pleasure or Commercial usage of planing or
semi-displacement hull craft can qualify for Intermediate Duty service Classification if full throttle
operation will average only a few hours per day with major portion of usage at partial throttle and
total annual usage will be 2000 hours or less.
PLEASURE CRAFT:
Maximum power capacity is intended only for
personal use, planing hull pleasure craft where full engine throttle operation will be less than 5% of
total time with balance of time 87% of full throttle engine rpm or less. Marine transmissions used in
long-range pleasure cruisers, sportfish charters or any commercial service should not be selected
according to Pleasure Craft Service Classification.
POWER TAKE-OFF
CLASSIFICATIONS
POWER TAKE-OFF DUTY CLASSES:
- Duty Class I: The clutch is used for disconnecting the power from
the load. When engaging, so little work is done that the clutch shows no temperature increase at the
pressure plate outer surface.
- Duty Class II: The clutch is used primarily for disconnect, but does
more work during engagement than in Duty Class I.
- Duty Class III: The clutch will engage within three (3) seconds,
never heat the pressure plate more than 100°F (56°C) above ambient, and once engaged is operated for
one (1) or more hours before disconnecting.
- Duty Class IV: The clutch will engage within four (4) seconds, never
heat the pressure plate more than 150°F (83°C) above ambient, and once engaged is operated for one (1)
or more hours before disconnecting.
- Duty Class V: The clutch is used to start large inertia loads which
require four (4) seconds to start the largest load, with the longest slip period per engagement not to
exceed ten (10) seconds. The clutch must be selected according to it's horsepower absorption
capability. Clutch applications in this Duty Class or those that require frequent engagements require
Twin Disc factory review.
PUMP & IMPELLER GUIDE
PUMP GUIDE:
For reference to the Jabsco pump types available,
review the Pump Selection Guide. This shows by example, the
variation in pump types.
