Component Failure Rate in Stanby Mode

[Rushabh J]

I am trying to predict the reliability of electronics control. The control is programmed such a way that 5 ICs would be active every 0.5 Sec. for 0.0012 Sec. and then it would go to it's sleep mode or idle mode. Main point is we are not switching it off but just keeping it in IDLE / SLEEP mode. For all this ICs I got the failure rate data in the working condition of IC. We got the Reliability Test Report conducted for 1000 Hrs.
I tried in RELEX as well as PRISM to find any option which takes care of standby/IDLE/Sleep mode failure rates, but it gives option to enter the mission profile time against different temperature. But I believe entering different temperature is not the solution . Because Ideally in stand by more failrue rate would change. My question is how to calculate the total Reliability. In the IDLE/Sleep mode time what should we consider the failure rate. Thanking in Anticipation.

[Pantelis]

Well you are correct by saying it would change.

Now as to what you are asking… First and based on the methods you mentioned, I am assuming you are attempting to solve this using “prediction” methodologies (or cookbook approaches) based on standards such as 217. These are nothing more than rough approximation that do not take into account every nuance, as mentioned, and were never intended to, as their purpose is to provide a rough initial approximation.

Now wrt to standby units there are formal methodologies of quantifying their reliability. What these methodologies do is quantify reliability based on active failure rate behavior and standby failure rate behavior. These methods require that you have knowledge of your quiescent (while in standby) failure rate behavior. An intro to this can be found at http://www.weibull.com/SystemRelWeb/standby_components.htm.

Hope this helps.

[tarik]

It sounds that you IC’s are active for a portion of time, then go into an idle stage then again become active.. and so on. There is a way (not a straightforward one though) to model this situation in BlockSim. I suggest you read this article:
http://www.weibull.com/hotwire/issue48/hottopics48.htm

The other approach I suggest is that you adjust your failure distribution, obtained under testing condition that assumed a continuous operation, to a failure distribution that reflects the fact that your components only operate for a portion of time. For example if you had determined that your components follow a Weibull(beta=3,eta=1000h) then to reflect that the components would actually only operate for 50% of the time, I would then use a Weibull(beta=3, eta= 2000h) instead (assuming that the component can’t fail during the idle stage, i.e no quiescent distribution).

[lenta]

Hi
Can u help me to do this exercise?
a)Is required to operate at an avarage availability of no less then 92 % - optimize spare parts for this system in steady state for 2 years.
b)Use the poisson distribution to estimate the number of needed spare parts for this period.Compare withe results of (a).
----AK-----AB------AC-------E----------F
every detail has 3 periods
1) time untill failure occurs
2) repair time
3) recycle time
If u know how to deal with this problem please write me to my e mail
leniashtein@gmail.com (leniashtein@gmail.com)
And i will send you numbers (3 times for every detail )
Thank you !

[lenta]

Hi
Can u help me to do this exercise?
A)Is required to operate at an avarage availability of no less then 92 % - optimize spare parts for this system in steady state for 2 years.
B)Use the poisson distribution to estimate the number of needed spare parts for this period.Compare withe results of A
AK-----AB------AC-------E----------F
every detail has 3 periods
1) time untill failure occurs
2) repair time
3) recycle time
If u know how to deal with this problem please write me to my e mail
leniashtein@gmail.com (leniashtein@gmail.com)
And i will send you numbers (3 times for every detail )
Thank you !