I have an orbital sander that uses stick on type discs. Can it be converted to the hoop and loop discs?
Maybe. If you want to try, get yourself some self adhesive velcro and put the hook part on the sander (I believe the discs have the fuzzy part, right? ). I know that this works in many other applications, can't say as I've tried or seen it done on a sander or dusty environment. The most that's going to happen is it isn't going to work an you remove the velcro and go back to using the adhesive backed discs. There may also be a different orbital base for your sander that will accept hook/loop, check with the manufacturer or authorized dealer in your area.
Some of the RO sanders have hook and loop plates that you can use to retro fit, check with you manufacturers web site. Just trying to stick a hook pad on the sander you have will probably not hold very well or will pull off when you change the sanding disks a few times.