# Daily fuel consumption calculation

Discussion in 'Propulsion' started by YSS Caribbean, Jun 29, 2020.

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### YSS CaribbeanNew Member

Hi everyone,

I am studying at the moment a Unit about propulsion systems and in the assesment the following question is presented:
Using the following vessel information calculate:-

The estimated daily fuel consumption.

L = 30m

Vesselâ€™s service speed = 8kts

Displacement = 410t

Fuel coefficient = 76,000

NOTE: I have done the calculations and research but struggeling with myself to belive the actual result and thinking I made a mistake somewhere, but cant get a grip on it.

I come to the result: Fuel consumption/day = 0.37 t

My calculation path is in the attachment. Hope someone can just have a quick look- if I missed something.

Thanks a lot.

Last edited: Jun 29, 2020
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### TANSLSenior Member

Well no, it seems that this time you have not guessed right. Try again.

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### YSS CaribbeanNew Member

OK. Thanks. I give it another go.

I just noticed I twisted my numbers- it should read 0.37 t! But that would be even less!

But the formular is the correct one?

Thanks for the quick response!!!

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### TANSLSenior Member

I have no idea where that formula can come from and for what type of consumption it may be valid. For example, the consumption of many thing depends a lot on the time that the thing is working. That parameter doesn't seem to play a role in your formula.
Actually, what device or thing do you want to know its consumption?

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### YSS CaribbeanNew Member

Dear Tansl,

the formular came out of the lectors book. But I also researched it and also found it different other books.
For exaple here:
Reeds Vol 13: Ship Stability, Powering and Resistance https://books.google.com/books?id=lvcqAwAAQBAJ&pg=PA360&lpg=PA360&dq=calculating+the+daily+fuel+consumption+for+a+ship+with+the+fuel+coefficient&source=bl&ots=4qOsZjEOax&sig=ACfU3U3gblSOejsntbkj4cUiRawC5_8P3Q&hl=de&sa=X&ved=2ahUKEwiM94uou6fqAhVCqaQKHdWzA-0Q6AEwDXoECAoQAQ#v=onepage&q=calculating%20the%20daily%20fuel%20consumption%20for%20a%20ship%20with%20the%20fuel%20coefficient&f=false

It is very basic and often refered as the old method.

This is also the reason I have so limited information given and I am struggeling.

I looked at it again recalculated it - but still come to the same result.

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### TANSLSenior Member

I did not know that formula, sorry for my ignorance.
I still think that the consumption of an engine can vary quite a bit depending on the hours it is running (perhaps that formula refers to the hourly consumption). Consumption is likely to vary greatly with the revolutions per minute at which it is operating. It is also possible that it varies if it is the propeller of a barge or a frigate. It is also possible that an older engine consumes much more than a modern one ....
Finally, once my ignorance has been declared, I have no choice but to use my common sense and that sense leads me to be very suspicious of such a precious formula.
Define the motors you need and check their consumption in the manufacturer's catalog (although the manufacturer will tend to say that the consumption is less than what you will be able to check later)

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As always, first thing, is to check the units. Whenever there are coefficient/constants in an equation, you need to ensure the values you are using are the correct units.
In this case, it is correct and your calculated value is correct. Despite the extraordinarily low value.

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