The problem with the line blowing off seems not to be so much the clamp as the steel line that the hose attaches to.
Usually on a pipe that a hose attaches to, there is a crimp made on the end of the pipe which keeps the hose from backing off of the pipe. The hose can back off just until the clamp comes to the crimp in the pipe, then it typically can't back off over the crimp.
The pipe that the power steering hose attaches to has almost no crimp to it, which is the real cause of the problem.

Gilly