RBD with Series / Parallel Combination

[Jennifer.Bell]

Question regarding RBD's treatment in Blocksim.
My system has a series / parallel configuration similar to that in this link -


http://www.weibull.com/SystemRelWeb/blocksimtheory.htm#reliability_phase_diagrams_(rbd s).htm

Groups of three items are in series, and these groups are in parallel with each other.

The items in series have similar reliability curves, and I'm concerned with overlapping failures - The first in series might fail, then the second in that series fails before the first is repaired.

When any item in that series "branch" is failed, are the other items in that branch considered down as well? Or do they still have the ability to fail?

Thanks,

Jennifer

[Arai.M]

I am unsure of what you are asking so let me know if I did not interpret your question conrrectly.

I have three items in series and those three items are in parallel with other sets of three items in series. In the link you gave, it would be like having a number of engines (for simplicity, lets say 2) and each engine having three failure modes for example.

When one of the three failure modes occurs, from a reliablity perspective the path is down but the system is still operating. If any failure mode occurs during that time in the other engine, then I have a system falure.

Blocks have the option to operate even if the system is down (unchecking that item would mean that if the system is down, the components that are not failed, do not age (or fail) until the system is restored.

However, if the system is not down (such as in the example of one failure mode ocurring in one of the 2 engines), the other two failure modes still have a probability of occuring.

In your case, are you trying to replace all three items in series when one fails? or do you have a scenario where the other two items simply stop operating when the third one occurs? These scenarios would require to perform actions based on a group.

As an example, assume that a failure in one of the three items triggers a replacement of the other two. All three items need to have an identical non-zero group ID and a preventive maintenance upon maintenance of another group item.

If the other items simply stop operating, an inspection upon maintenance of another group item can be performed with a restoration factor of zero.