How to choose the materials for mechanical seals?

There are some rules when choosing the material for a mechanical seal. Etc, we can use ceramic/carbon/nbr, that means rotary use carbon for seal face, and ceramic for stationary seals. And oring use nbr.  Be careful when you use hard material for both rotary and stationary seal face, that means the temperature will be very high when mechanical seal running, so make sure you have cooling system for your mechanical seal, if not, the rubber parts of mechanical seal will be burned soon.