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markschahl
Community Trekker

Repairable System Simulation - logNormal TTR?

As a recent upgrader to JMP Pro, I now have access to the Reliability Simulation tools. Previously, I had used RAPTOR from the USAF to do this type of work.
A common problem in logistics at a refinery or integrated chemical complex is sizing of buffer vessels between sequential units. Example:

 

Producer-A -> buffer tank -> User-B

 

I know:

User-B time to failure distribution (TTF) - a nice Weibull fit

User-B time to repair distribution (TTR) - a nice logNormal fit

 

 

In the options for Time to Completion there is no option logNormal distribution, only Normal. How long User-B is down is the information needed to calculate the size of the buffer tank so that Producer-A can avoid shutting down while User-B is down.

 

Two questions:

1) Is there good way to simulate logNormal distributed Time to Completion with JMP Pro 14.1?

2) Any plans to add other distributions like logNormal to this platform in the future (or should I add to the wish list)?

 

Thanks!

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1 ACCEPTED SOLUTION

Accepted Solutions
gzmorgan0
Super User

Re: Repairable System Simulation - logNormal TTR?

Mark,

Your question highlighted a new feature I had not explored. So, thank you.

Obviously, I am a novice here, and I am guessing.  An interim "kludge" might be Choice. I wonder if you could create a list of simulated logNormal wait times, and use that list.

  • Model it as choice with 5 values and save the simulator (script). 
  • The saved script should have that list and you could try specifying the reference to the generated list of logNormals, or copy and paste the list to the script.

I'd start out with a small list then try one with 1000 values. My guess is that JMP is just randomly selecting an index from 1 to n and using that value.  It is a kludge, but might provide reasonable results.

 

Maybe JMP developers have a better solution, or maybe 14.2 features more distributions.

 

It would be interesting to know if that works (let the blog know). I am still learning. If I get an example to work, I will update this post.

 

Thanks for the question. Since I am not currently doing reliability work, it would have been very low on my list. This is too cool to wait that long.

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2 REPLIES 2
gzmorgan0
Super User

Re: Repairable System Simulation - logNormal TTR?

Mark,

Your question highlighted a new feature I had not explored. So, thank you.

Obviously, I am a novice here, and I am guessing.  An interim "kludge" might be Choice. I wonder if you could create a list of simulated logNormal wait times, and use that list.

  • Model it as choice with 5 values and save the simulator (script). 
  • The saved script should have that list and you could try specifying the reference to the generated list of logNormals, or copy and paste the list to the script.

I'd start out with a small list then try one with 1000 values. My guess is that JMP is just randomly selecting an index from 1 to n and using that value.  It is a kludge, but might provide reasonable results.

 

Maybe JMP developers have a better solution, or maybe 14.2 features more distributions.

 

It would be interesting to know if that works (let the blog know). I am still learning. If I get an example to work, I will update this post.

 

Thanks for the question. Since I am not currently doing reliability work, it would have been very low on my list. This is too cool to wait that long.

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markschahl
Community Trekker

Re: Repairable System Simulation - logNormal TTR?

Thanks! That suggested work-around did the trick.

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