Originally Posted by poncho62
I don't think that he wants to cut the pipe, he wants to be able to take it apart with the minimum of damage to it.............
The big problem, I'm guessing, is that it is (1) rusted together just eough to not (fairly easily anyway) come apart with strong arm twisting, or (2) the ends of the pipe are crimped or crushed by the use of the clamps.
What the best option I can see then would be to "slice" the outer peice (carefully and minimally to allow re-use) as poncho says, and then take a pipe expander to "reshape" the inner and the outer pipes. Otherwise, maybe you have connections with a local exhaust place that would be able to remake a shorter extension that you could install in the place of what you cut. Either way, good luck.
In a while, Chet.