Advice on prn

Prn employees at my facility make more per hour since they do not have benefits. I am thinking of asking to go prn on my floor. In the past, some people have managed to get the prn rates while others are just dropped to prn and been told no to the pay increase. How can I approach this to give myself the best shot at getting the increase? I am hoping to go prn in June. I am willing to apply for another floor if it means more pay but it would be smoother to stay where I am. But if they do not pay me prn rates, I might look elsewhere.
I would think that regardless if you are changed to PRN or started as a PRN, you should be paid the higher PRN rates. I'm sure if your hospital does not do it that way, then they have some clause to cover themselves. Hmm...had not heard of that before, getting paid more for PRN. I don't know how much power you have in your wage, but it wouldn't hurt to just ask if you'd be getting the PRN rates. Hope you get it!