A/C Compresser noise

[iufan71]

On my way home from work today,started hearing a funny sound. Well made it home ok,truck wasnt getting hot or anything. But i open the hood,and i see little peices of black material all over my windshield washer bottle and everything in the area. Seems a little disc on the a/c compressor is just flapping around and makeing all kind of racket.I need to know do i just let the piece come off on its own,or is there a way to get the outer piece of the a/c pully of to take it off myself. Am going to try to post a pic or two of what i am talking about.