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Calculating Engine Load Factor??

 
 
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Old 03-05-2008, 03:24 AM   #1 (permalink)
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Calculating Engine Load Factor??

Can I get some guidance in calculating the engine load factor?

I am actually looking at purchasing a pair of CAT 3412E (E rating) engines and would like to get some guidance and pointers in how to calculate the load factor for the engine? It is mentioned in the engine conditions and definitions to use it upto a 30% load factor. This cannot mean an average of 30% of the rated RPM (2300)....right!!?? I am assuming that its a combination of the usage hours and the RPM ranges that the engines will be used during these hours....something like that.

Any help would be much appreciated. Thank you all in advance.
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Old 03-05-2008, 12:33 PM   #2 (permalink)
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I suspect you missed a word, not that I have access to a cat manual but from memory I believe is says "up to 30% full load factor" which means you can run the engine no more than 30% of the time at full load and max RPM
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Old 03-05-2008, 02:39 PM   #3 (permalink)
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Quote:
Originally Posted by Garry Hartshorn
I suspect you missed a word, not that I have access to a cat manual but from memory I believe is says "up to 30% full load factor" which means you can run the engine no more than 30% of the time at full load and max RPM
Ahhh.........how silly of me!! THANKS A LOT!! Yes it makes sense now!!!!
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Old 03-05-2008, 02:59 PM   #4 (permalink)
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Caterpillar E rating: High Performance - For vessels operating at rated load and rated speed up to 8 percent of the time, or one half hour out of 6, (up to 30 percent load factor). Typical operation ranges from 250 to 1000 hours per year.

Refer to the fuel burn spec at 100% load at each RPM. The LOAD FACTOR is the actual fuel burn divided by the maximum rated fuel burn. If your engine is rated to burn 100GPH at WOT and you are burning 30GPH, 30/100= 30% load factor. This doesn't mean you are limited to never pulling more power out of the engine, it just means that you are limited to full rated power for 30 minutes out of every 6 hours and over the life of the engine and the amount of fuel burned should not exceed 30 percent of what it would have burned if it had been running at max rated power output.

In a nutshell, an engine has a lifetime that can be measured in weight of fuel burned. You can run that weight of fuel through the engine in a short time period if you are extracting large amounts of power, or you can take forever to burn that much if you only extract small amounts of power. The load factor represents the relationship between fuel burn and the number of hours you are taking to burn it.

Reading back over that it is clear as mud ...
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Old 03-05-2008, 06:34 PM   #5 (permalink)
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Originally Posted by Marmot
Caterpillar E rating: High Performance - For vessels operating at rated load and rated speed up to 8 percent of the time, or one half hour out of 6, (up to 30 percent load factor). Typical operation ranges from 250 to 1000 hours per year.

Refer to the fuel burn spec at 100% load at each RPM. The LOAD FACTOR is the actual fuel burn divided by the maximum rated fuel burn. If your engine is rated to burn 100GPH at WOT and you are burning 30GPH, 30/100= 30% load factor. This doesn't mean you are limited to never pulling more power out of the engine, it just means that you are limited to full rated power for 30 minutes out of every 6 hours and over the life of the engine and the amount of fuel burned should not exceed 30 percent of what it would have burned if it had been running at max rated power output.

In a nutshell, an engine has a lifetime that can be measured in weight of fuel burned. You can run that weight of fuel through the engine in a short time period if you are extracting large amounts of power, or you can take forever to burn that much if you only extract small amounts of power. The load factor represents the relationship between fuel burn and the number of hours you are taking to burn it.

Reading back over that it is clear as mud ...
Thanks a lot Marmot for the very detailed explanation. Should one have to stick to this 30% load factor for all RPM ranges (actual fuel burn vs. the maximum power fuel burn for each RPM)? Or can one look at maintaining a 30% average load factor (actual burned fuel compared with the fuel burn at maximum rated power output)?

Thanks for ur time and input!
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Old 03-05-2008, 07:35 PM   #6 (permalink)
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"Should one have to stick to this 30% load factor for all RPM ranges (actual fuel burn vs. the maximum power fuel burn for each RPM)? Or can one look at maintaining a 30% average load factor (actual burned fuel compared with the fuel burn at maximum rated power output)?"

The load factor is based on the lifetime amount of fuel burned in relation to what the engine would have burned at max rated power. It is a moving target since you can run for a few hundred hours at low power and shift the load factor downwards.

The amount of fuel burned is directly proportional to load, more load more fuel burned, so there is only one load that will provide an instantaneous 30 percent and we don't really care too much about that since we bought the engine because we could get 2 or 3 times the power from it than the same engine is rated at for workboats. We just can't get it for as long as they can.

We measure every drop of fuel burned and compare that to what the engine would have burned at max rated power and that becomes the load factor.

It is a peculiar way of rating an engine and can be confusing. Exceeding the power factor will not effect warranty, it will just shorten the time between overhauls. Cat delivers the engine with a certain number of horsepower hours stashed away in the block and fuel lets them out. Once you put a certain amount of fuel in there all horsepower hours go away and the engine is worn out ... if you stick to the 30 percent figure you should get the number of hours that Cat advertises as being available, look at it that way.
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Old 03-05-2008, 11:06 PM   #7 (permalink)
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Hi,

Exceeding the Load Factor will very surely affect your warranty.

If you have a failure like a dropped valve or turbo/piston failure the Cat Tech will sure as heck look at how much fuel the engine has burned and the hours done all as a part of his paperwork to complete the warranty job. This I believe is one reason why the total fuel burn figure in the engine computer is non resettable.
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Old 03-06-2008, 02:42 AM   #8 (permalink)
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Originally Posted by K1W1
Hi,

Exceeding the Load Factor will very surely affect your warranty.

If you have a failure like a dropped valve or turbo/piston failure the Cat Tech will sure as heck look at how much fuel the engine has burned and the hours done all as a part of his paperwork to complete the warranty job. This I believe is one reason why the total fuel burn figure in the engine computer is non resettable.

Thanks a lot K1W1! i needed to clarify that....the impact on the warranty if the load factor is exceeded and now i know that the fuel burn figure cannot be reset!
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Old 03-06-2008, 04:50 AM   #9 (permalink)
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Hi,

The "instantaneous" fuel burn comes and goes as the engine runs, it returns to 0 when the engine is off.

The "trip" fuel shows how much was burned since the last time it was reset to 0

The "Total" fuel shows how much has been burned since the very beginning of the engines life. This is the one that can't be reset (by the end user anyway)
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Old 03-06-2008, 06:33 AM   #10 (permalink)
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The total fuel burn cannot be reset because that figure is central to calculating the load factor. If it were reset the load factor number would go away.

I will look for the Cat reference to warranty and post it unless someone else finds it or calls Cat first. Running higher load factors just uses up the engine faster, it doesn't damage the engine as long as the engine is operated within its rated power output and operating parameters so there is no connection between dropping a valve and running higher load factors.
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Old 03-06-2008, 09:07 AM   #11 (permalink)
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Found it! Cat has an online Marine Selection Guide with the following information:

Time at Full Throttle: “E” rated engines in typical pleasure craft
applications normally record less than 1% - 2% of operational time at full
throttle. Caterpillar develops engines with this rating to operate for up to
8% of the time at full throttle. Exceeding this amount of time at full throttle
operation will cause engine overhaul life to be reached sooner than
anticipated, but will not affect warranty. Please refer to the Marine
Engine Selection Guide (LEDM3457) for all other rating definitions.
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Old 03-06-2008, 12:58 PM   #12 (permalink)
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Hi,

CAT literature doesn't always mean what it says.

CAT will also have you believe there is no de rate at up to 50 Deg C.inlet air temp.

If there should be a failure- make a claim and then see how the Dealer who by the way is CAT's customer (not you the owner) and see how the whole process works.
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Old 03-06-2008, 01:59 PM   #13 (permalink)
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I'm not interested in getting into a pissing match trying to defend Cat but if they say there is no warranty issue then there is no warranty issue. Why would they waste their time making up and publishing something like that in a document intended to educate engine users or buyers about the meaning of their engine ratings and applications?

The other side of the issue is, as I wrote earlier, if the engine is operated within its rated power range and within its operating parameters, it is not overloaded or abused and will last for the number of horsepower hours it is designed to produce. Operating it at higher load factors does not overload the engine, it merely "wears out" the engine in less time.
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Old 03-06-2008, 03:12 PM   #14 (permalink)
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Quote:
Originally Posted by Marmot
Found it! Cat has an online Marine Selection Guide with the following information:

Time at Full Throttle: “E” rated engines in typical pleasure craft
applications normally record less than 1% - 2% of operational time at full
throttle. Caterpillar develops engines with this rating to operate for up to
8% of the time at full throttle. Exceeding this amount of time at full throttle
operation will cause engine overhaul life to be reached sooner than
anticipated, but will not affect warranty. Please refer to the Marine
Engine Selection Guide (LEDM3457) for all other rating definitions.

It is true that there is nothing specified in the rating conditions (LEDM3457) and nor in the CAT Marine Warranty description that the warranty will become void if the rating conditions are not followed. But at the bottom of the Marin Warranty description, under the limitations, it does state that CAT is not responsible for 'Failures resulting from improper use or installation'. I guess this provides them the grounds to void a warranty for not using the engines within the rating conditions. I have also discussed this with the CAT distributor in my area and they have specifically said that if I do not follow the rating definitions for the engine (30% load factor, 1000 hours, etc.) then the warranty will become void....
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Old 03-06-2008, 03:22 PM   #15 (permalink)
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If I were going to buy an engine from them I would make sure they put in writing that they are placing warranty conditions on the engine beyond what Cat is publishing. I wonder if they will do that? Considering that they also added an hour limit well under Cat's published specification adds to the issue. Have you contacted Cat headquarters to obtain a definitive statement on what conditions would void the warranty? Until you have that the issue is moot.
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