Ace15, PKD is using an "Express Lane" or "Express Line" ticket system for Volcano and Hypersonic. It is free. They set up ticket machines outside of these two rides. You get a ticket which tells you what time to come back to ride.
Get there a little early. For example, if you are to ride at 4:00, get there about 15 minutes early. They have the express line set up that takes you straight in to the ride. On Volcano, they let the Express Line ticket holders take the whole next train, then let the people in line have the next train, then so on.
Beware, they stop giving out tickets at a certain time. I don't know what time it is, but it is fairly early. Be sure to get yours as soon as you can.