Alternator Belt Slipping

Hi! I need some help! My alternator belt keeps slipping off.  Generally it does it early in the morning with the first start of the day. We are on the second replacement belt. The first replacement belt got chewed up.....this belt is still fine, but even after putting it back on and tightening it up it will slip off the next morning. I've gotten some input that it might be a problem with the tensioner...anyone got any other ideas. Alternator is in good working condition. Battery is brand new (also just replaced) and both belts are new too. Thanks in advance for any help! 

PS....It's a 1996 Mitsubishi Galant ES.

funnycat38117.3769675926

either you tensioner is shot or your brackets are out of alighnment theres really nothing else that I can think of off hand

Hi....thanks for the input. Turns out my Harmonic Balancer is shot. We're just hoping that's the only thing that was causing the problem. Thanks again.

Yea i'm sure it is the rubber wears out of them but usualy you hear a knocking sound ...guess it just pushed forward and knocked the belt out of alignment