When rating criticality using a numerical system, the numbers can be ascending (e.g., 1 is least critical) or descending (e.g., 1 is most critical). Does anyone have any experience that speaks to which works better? It seems like many people think of most critical by assign it "1" for "first." However, if considering a mathematical system, does it make more sense to represent a higher criticality with a higher number?

This seems trivial, I know, and it is probably just six of one, 1/2 dozen of another. As I assess our system and possibly revamp it, I just don't want to accidentally paint myself into a corner with a system that won't obey sorting and arithmetic rules (assuming I may need them down the road).

Mark

yes mark.
there are two ways to go. I favour high being critical because if you run a matrix and multiply frequency and consequence to get a number usually high risk goes to the left on the x axis and high consequence go up on the y axis. High numbers then mean high risk. you can use a scalar number after that to convert the numbers back to a 1 - 10 scale or similar

I like to use both in different situation.

When doing a risk analysis or asigning RPN's in a FMECA analysis I use high as critical for the same reason as APM.

For equipment criticality and work order priority in our CMMS I like low being critical because I find it more intuitive for planners, mechanics and operators to use.

For example, in our CMMS we have equipment criticality set up as A, B or C, with A being most critical. Work order priorities are 1, 2 or 3 with 1 the highest priority (0 for emergency work). Therefore planners know that any A1 work orders are their highest planning priority.

Combining eqpt criticality with work order priority clearly like A1 seems a good idea especially if eqpt criticality does not appears directly in work orders.