Replacement

[prakash]

Hello,

As you know Optimum Replacement of a block or an item is mainly based on Planned, Unplanned Maintenance Cost and also on Reliability Parameters (beta and eta) as described at http://www.reliasoft.com/newsletter/2Q2000/preventive.htm (http://www.reliasoft.com/newsletter/2Q2000/preventive.htm).

There is a big difference in Optimum Replacements if there is a difference in Planned and Unplanned Maintenance Costs.

Rather than cost factors, is it not possible to assign the replacement of an item (probably) based on Expected Number of Failure, Number of System Downing Events, MTTFF or MTBF to achieve maximum reliability/availability of the system.

I will be pleased if you suggest me how could I use Replacement policy into BlockSim 7.0.2.

Thank you.
Prakash

[Arai.M]

Hello Prakash,
The optimization for optimum replacement in BlockSim 7 minimizes the cost, like you mentioned, given a cost for planned and umplanned maintenance and a reliability distribution.
If you wish to do this by failures, then your solution will be to do a preventive maintenance continously (interval = 0) as that will make the number of failures go to zero. If you wish to do this by number of events, then running to failure will give you the minimum number of events.
In fact, the only metric I see as actually making sense to optimize instead of cost is the availability, in other words, minimize the downtime. However, that could be put in terms of cost as well and the downtimes due to planned vs. unplanned maintenances should be known.
Now if we are talking at the system level, obtaining an analytical solution can become mathematically intracable very quickly. The input variables are too many and optimization is not possible. What you can do is vary the input of interest (pm interval) and observe the output that you are interested in optimizing (cost, downtime, availability, etc.)
Hope this helps,
Arai