Thank goodness we are slowly learning "A more detail about MOC" .. !!!
It seems that your intention here is to save piping capital cost and come up with a quick solution
Rather than instituting a management system to monitor your Firewater Aux/C/Wt interconnections, why not install a modern dedicated cooling water piping system and be done with it ?
According to the US Fire Codes, if your water tank/reservior is properly sized, it can serve both the Fire Protection and plant cooling needs.
It's just more piping .. your plant has grown and demands more Cooling Water !!!
What happens when there is a fire and your fire fighters find the hydrants already piped up and no place to connect !!!!
This is how plant fires get out of control .... operators "forget" that there are several interconnections to the fire water system and, when there is an emergency, the fire protection system cannot perform ...
You cannot use your MOC system as a Management crutch in this case ...
I agree with LittleInch .....
MJCronin
Sr. Process Engineer