Reliability Analysis Software

  • Thread starter Jason Beveridge
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Jason Beveridge

I am looking for some reliability analysis software in order to determine the SIL level of a DCS / Burner management system combination.
Something that is freely available or not too expensive would be best as I do not know when I may use it again. All suggestions greatly appreciated.

A non-software option may also be considered.

Jason Beveridge

Email: [email protected]
Software, including a free demo version, is available at
Doing the calculations by hand is covered in "Safety Shutdown Systems: Design, Analysis and Justification", by Gruhn & Cheddie, ISA, 1998, ISBN 1-55617-665-1
Running a SIL analysis is time consuming and hard work.

You have to have the MTBF for the individual modules, being considered, broken down into the failure modes which will cause:
(1) failed dangerous, detected,
(2) failed dangerous, undetected, plus
the individual module failure rates broken down into the failure modes which will cause:
(3) failed safe, detected,
(4) failed safe, undetected.

The goal is to minimize the failed dangerous failure rate.

After performing the Failure Modes and Effects, Criticality Analysis, the results of the FMECA are used to assign values for each kind of
failure mode. This is more or less documented in IEC 61508. Then, you can turn to the Markov Model in MEADEP. Lots of work to be done prior to running the Markov.

John Peter Rooney
ASQ Certified Reliability Engineer #2425.
Dear Jason Beveridge:
I do not know if I understand and if you are asking for the right thing. The Safety Integrity Level (SIL) of a configuration depends upon how the system (sub-system) will fail and if failed, is the failure noticed or announced? The worst thing is for the failure mode to be a failed
dangerous, undetected state. The goal is to minimize the failure rate value for the failed dangerous, undetected state. Now, the Markov State Transition approach is generally used for the model of such analyses. There are some
software application packages that do Markov, which is also good for, say digital design. MEADEP has already been mentioned.
So, my question revolves around your intention: are you running a IEC 61508 SIL analysis all by yourself on your company's design?
John Peter Rooney
ASQ Certified Reliability Engineer #2425.
I agree completely. Determining probabilities without knowing consequences (as defined by the "Effects" in the FMEA/CA) is pointless. Moreover, you need good failure rate data -- and
recovery probabilities (in the case of redundant systems) in order to define valid results.

Markov modeling is a necessary, but not a sufficient part of the process.