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"Derating"

"Derating"

"Derating"

(OP)
Hi,
English, is not my mother tongue.
In different cases, I heard the word "Derate" and/or "derating". What is the exact meaning of those?

Thanks

RE: "Derating"

Both basically refer to a reduction in some operating parameter or specification to improve the reliability of a system or component.

"I think there is a world market for maybe five computers."
Thomas Watson, chairman of IBM, 1943.
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

RE: "Derating"

From Miriam-Webster on-line

Main Entry: de·rate
Pronunciation: (")dE-'rAt
Function: transitive verb
: to lower the rated capability of (as electrical or mechanical apparatus) because of deterioration or inadequacy  

Usually applied to something that has a rating or permit associated with it.  e.g. "My electrical service was derated by the building inspector because it had pennies for fuses."

RE: "Derating"

Ingy:  the inspector should not derate it for the pennies, he should reject it.

Example of derating:

A certain wire has an ampacity of 100 A.  However, if the ambient temperature is expected to reach 50 deg C, then the ampacity must be DERATED (reduced) by 25%.  The ampacity of the wire at 50 deg C is therefore 75 A.

William

RE: "Derating"

A gas turbine may well be derated in perfect condition.  Both Rolls-Royce and Pratt & Whitney sell engines that are mechanically identical but have different power outputs depending on the rating plug in the engine controller.
Equally, take-offs on long runways are often "derated" - use less than full power for the take-off because you don't need it - this has a significant effect on engine life.

RE: "Derating"

My (The Little Oxford) dictionary simply says:

derate v.t. lower or abolish rates on.

(where "rates" typically refers to taxation)

RE: "Derating"

Are you sure it's not a poor pronunciation of "deaerate" (remove air from)?

RE: "Derating"

(OP)
Thanks,
So simply it means "decrease".
TheTick: No, I know the meaning of Deaeration.

RE: "Derating"

Another common usage for 'derating' is when a heating device is 'derated' to prevent it from overheating. This is often a code requirement as gas burning devices are only allowed to have a certain air temperature rise.

In this case we are decreasing the rating of the unit - derating.

RE: "Derating"

I believe during the muscle car era, OEMs would routinely 'derate' the horsepower of their engines to cut potential buyers a break on insurance.

regards,

Hydroformer

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