Its completly depend on Department by Department in University.In my department, I can get upto 6 hrs of Internship Hrs(CPT) however u wanna take it( 1 crd. each semister for 6 semister or 6 credit in one semister).

U can take part time CPT as many as u want it don't effect ur OPT time, but u can't take full time CPT more than a year, if u did it will cancel your OPT.

AJ