>99.0025%

Unfortunately the minumum character set size means that others have to read this as well.■

You must delve a little deeper. First, separate plant from a sub-assembly such as a belt conveyor. Small belt conveyors typically have higher failure rates and lower time to repair (size, location, etc.).

Large and long overland conveyors have a more difficult and lower availability index due to the nature of detecting and correcting a repair ie. longer repair time due to size and location.

In order to provide a meaningful response, some key details need to be listed with necessary references. What items are in your failure rate analysis? What are the indexes you use and where are their references? Both failure rates and the more elusive Mean Time To Repair (MTTR). MTTR shakedown requires knowledge about detection, about notification of failure to maintenance crew, tools available (crane, trucks, crew size, location {top of a structure over stockpile?}, ....).

Good subject with lots of meat still on the bone. ■

I forgot weather conditions, a probability factor like the other listed details. Monte Carlo simulation is the best teacher on what questions to ask and enable the study with notes on the change in your availability index.

Once you have a comprehensive list and index portfolio, you then can ask how this will play out when you try to assess costs and benefits to improving the index. ■