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Another
option is a pipe freeze (also know as a line
freeze, freeze stop, freeze plug or cryo-plugging.)
The procedure here is much less involved and
invasive. A special cuff, sort of like a tube
split in half the long way, is attached to the
pipe where you need the stop. The cuff is filled,
little by little with liquid nitrogen (which is
about 320 degrees below zero) to gradually cool
the equipment and the pipe. Once the pipe is
sufficiently cooled the flow of liquid nitrogen is
increased until the contents of the pipe become a
chunk of ice blocking the flow in the pipe. This
creates a stable line stop. Pipe freezing requires
no holes or permanent changes to the line. As soon
as the work is complete, the liquid nitrogen is
withdrawn, the cuff is removed, the pipe and
frozen plug thaw and you are back in business. |
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Most type of
pipe are tolerant of the temperature involved in
pipe freezing. Types of pipe commonly frozen are
Stainless steel
Carbon Steel
Copper
Aluminum
Lead
Pipe freezing is commonly
used to service many types of industries including
hotels and resorts, apartment complexes, malls and
shopping centers, water and sewage treatment plants,
industrial and commercial production facilities,
power plants,
hospitals and many other
institutions.
Applications where pipe
freezing may be used include fire protection
systems, pump replacement, chiller modifications,
valve insertion or valve replacement, oil filled
electrical cable pipe repairs, pressure testing and
leak testing to name a few.
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There is a bit of fun science
involved in pipe freezing. Most people associate
frozen pipes with water damage to property and
costly repairs to systems.
So why don’t the pipes
break during this process? Well, here is the answer.
When pipes freeze in an uncontrolled situation they
freeze first along the pipe wall and then toward the
center. When the ice slug completely blocks the flow
in the pipe the ice keeps expanding along the length
of the pipe which increases the pressure the water
is under between the ice and a valve. The pressure
of the water builds and builds until finally the
pressure inside the pipe is more than the pipe can
take and it breaks in the unfrozen area where the
pressure was building. The pressure of the radial
expansion of the ice does not create enough stress
to cause a system to fail. |
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