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| What is Pipefreezing ? |
| Pipefreezing is a means of isolating part
of a pipework system by freezing the pipe contents over a short section,
so that the contents form a solid plug.
This avoids having to drain the system down, and in many cases freezing can be carried out without shutting the system down. Once a specific part of a system has been isolated with pipefreezing, it is possible to carry out repairs, modifications, maintenance, leak detection, pressure testing, etc. |
| How is pipefreezing carried out ? |
| A container (usually referred to as a
jacket) is placed around the pipe, and then filled with liquid nitrogen.
Liquid nitrogen boils at -196oC, and so boils very readily on
the surface of the pipe within the jacket. This removes heat from the pipe
and its contents, which will in time freeze solid. As the nitrogen boils
off, it releases nitrogen vapour which is vented away to the atmosphere.
In certain situations, solid or gaseous carbon dioxide is used. This is not as cold as liquid nitrogen, and so freezing takes longer, but has the advantage of not exposing the pipe material to such low temperatures. |
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