a 24/48 shift will average a 56 hour week. FLSA (Fair Labor Standards Act) says anything over 53 hours has to be overtime, so overtime hours have to be added to the base. Usually, the FLSA will be based on a certain pay cycle (ours was 27 days) and if you worked all the days in the cycle, you would get about 12 hours of 1/2 time on top of your regular pay.
There are different pay cycles other than 27 days, so the amount of FLSA pay will vary from department to department, depending on which cycle they run. Some departments toss in a Kelly day off to reduce the total hours of hours worked per cycle to avoid the extra cost. Others have gone to a fourth shift, which reduces the hours per week to way below 56. Hours/pay is done a lot of different ways across the US.
Also, management positions are exempt. And things can change based on interpretation of the FLSA regs.