Faber tells Montag to "Stand back from the centrifuge." What does it mean? What does the "centrifuge" represent?

Our civilization is flinging itself to pieces. Stand back from the centrifuge.

If the government is inefficient, topheavy, and tax-mad, better it be all those than that people worry over it

Beatty is telling Montag what books can and can't do for humans.  He basically says that they are falling apart...like a centrifuge that flings everything from the center to the outside as it whirls itself around separating particles from one another.  The civilization is doing the same thing, and that Montag is getting involved in something he shouldn't be bothered with or he will get "burned".  No pun intended, but perhaps this is exactly Beatty's point.  He, in fact, is burned to death by Montag, and Montag believes later that Beatty continually badgered him intentionally so Montag would kill him.  He believes that Beatty wanted to die.

"Stand back from the centrifuge"--don't get involved...stay back at a safe distance so as to protect yourself.  Be Happy.