Thanks for all the interest. Yes it freezes the liquid inside the pipe solid and it adheres to the pipe forming an ice plug. We have frozen chilled water, fire and domestic water lines. We've also frozen ethlyene glycol and fuel oil at a nuclear power plant. If its liquid - minus 325 will make it solid.
As far as fracturing the pipe, mild steel below minus 50 is brittle as glass. Engineers say the pipe will fracture. To date since 1992 the only fractures we've had we made under controled conditions to see what we could get away with.
See ya's in the server where may freeze capabilities are limited by my poor aim.