....So can this be done without mathematical models and can it be proved just theoretically, By explaining where the company can benefit just like you mentioned that in terms of cost, time and so on..???

No Beena this can not be done just theoretically!
As Jim Wynne stated, you will be disappointed with just theory.
What I am trying to explain that you need to go on production floor or machine shop, etc - ask questions and get a real numbers.
How many hours the piece(s) of equipment in Question was down during last month, year, etc.? Do they have any preventive maintanence program?
By doing this at the local Machine shop for example, you will be able to extimate the time of emergency repair and how much the shop would gain to keep it running foe extra (hour, day, etc.)
Enjoy your learning,
Mike