MCR vs maximum speed

[idham58]

hello guys,

anyone can explain the different between maximum speed and maximum continues rating speed?

[jehardiman]

Big overview is that maximum rated speed is the maximum speed the manufacturer expects the engine to run with any expectation of it holding together for the service life. Maximum speed is the speed achieved right before you blow something up.

[idham58]

too big overview..

how long the mcr can be used in one voyage without give major effect on engine lifetime?

[jehardiman]

Originally Posted by idham58

too big overview..

how long the mcr can be used in one voyage without give major effect on engine lifetime?

100%, excede it and you start eating into service life.

[idham58]

yup.. but i mean, how long 100% MCR can be used.. 1 minute? 1 hour? along the voyage?
give the usually usage.

[jehardiman]

Originally Posted by idham58

yup.. but i mean, how long 100% MCR can be used.. 1 minute? 1 hour? along the voyage?
give the usually usage.

100% of the time; that is the meaning of the term "continious", you can run it at the MCR speed/loading 100% of the time between scheduled servicing provided cooling, lubrication, and intake air requirements are meet. Diesel generators are often used like this. That said, there are things like "Full Power Hours" which is the maximum number of hours you can run before servicing, and then there are hourly checks, daily service, etc, etc.

[idham58]

ok.. thanks for the info.. have any other info regarding MCR? thanks a lot..

[jehardiman]

Try this site for one manufacturer's (CAT) take on ratings.

http://marine.cat.com/cda/components...&x=7&id=914324

[powerabout]

Its done on EGT and maximum sea water temp usually
I was on a vessel the other day with some Wartsila's and the manual has the ratings based on sea water temp and of course max egt but other things can alter that
The engine controls have 100% up to 115% for your monthly full power tests depending on the sea water temp

[FAST FRED]

The marine eng folks will usually supply about 4 power graphs , from 24/7/365 to just getting up on the plane, recreational. .

The trawler folks CAN use the max rating as it frequently is only 50% of the recreational rating.

Most boats are way overpowered (not ships tho) so MCR is seldom a big deal.

For best hard service life many will use 80% of MCR power and 90% of rated rpm.

This is fine IF you have selected an engine for super efficiency , as most diesels get the best HP/gal at near max throttle.

A good rule of thumb is 3 hp per ton (2240 lbs) of displacement for fast but not hull speed SL 1.2 , many folks will prefer SL 1.15 down to .9 for less fuel use.

FF