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– Liquid Nitrogen Pipe Freezing is used extensively for the exact examples of use that you gave. – Yes it will work on PVC, Copper, Steel, Cast iron etc. Obviously PVC being a poor conductor of energy to freeze the pipe requires a greater time. – It is important when freezing pipes that you do not freeze over joints or bends, keep to straight lengths of pipe.
Liquid Nitrogen requires to be stored under pressure in a thermal vessel and for costing, I suggest you talk to your local BOC agent or equivalent.
For freezing pipes say between 15mm – 50mm, you require to encase a section of pipe about 12″ long.