Fail Per E6 units?

[CKO]

Hi everyone

I do not quite understand the tabel data "Fail Per E6 units" in NPRD-95 regarding the unit of this number.

To me it seems like it has no unit at all.

Can anyone explain this number to me please, how it is calculated?

Best regards

CKO

[dnicholls]

The failure rate units in NPRD are generally in terms of failures per million operating hours. There are failure rate entries, however, that have the letter "M" following them, in which case the units are failures per million miles.

[CKO]

Ok so does that mean that entries with an M has to be converted if i want them in hours?

Another question is, how is hours related to velocity?

[dnicholls]

Entries with an M means that we did not have any operating hours associated with the data point (i.e., no velocity information); therefore, it is not possible to convert these entries from Miles to Operating Hours.

[CKO]

Can anyone verify this(post #4) please?

[Norbyzuka]

Failure rate with "1" E6 unity = 1*10-6/hours = 0.000001/hours
MTBF = 1 000 000 hours
M unity = failure rate / Miles.
some reliability software use "miles = hours" as ram commander without convertion.
I wish that NPRD-2010 will have E6 for all components.

[Highkeas]

Originally Posted by dnicholls

Entries with an M means that we did not have any operating hours associated with the data point (i.e., no velocity information); therefore, it is not possible to convert these entries from Miles to Operating Hours.

Often for reliability analyses I have to make engineering estimates.
In this case if you have miles just divide operating miles by average speed (make a conservative estimate) and you obtain operating hours.

An educated guess is better than nothing.

But any system should be subjected to testing to ensure it will meeting operating environments and duration.

[Highkeas]

Originally Posted by Norbyzuka

................
I wish that NPRD-2010 will have E6 for all components.

For mechanical systems it is often operating stress and other factors which drive reliability, not hours to failure.