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| Water
and water-based liquids are by far
the most commonly encountered pipe contents. Water is almost unique
in that it expands on freezing - the cause of burst pipes in cold weather
- and allowances have to be made to accommodate this expansion. Freezing
times are dependent on liquid temperature, pipe size, and local pipework
geometry, and in the case of water, are usually predictable. Additives
such as glycol which suppress the freezing
point make pipefreezing more difficult, but allowing additional time and
liquid nitrogen usually means that freeze isolation is possible, even in
very large pipelines (see our examples
pages)
Water based liquids such as slurries and sludges behave in a similar manner to water. Heavy oils (e.g. fuel oil, diesel) and crude oils can usually be frozen in favourable conditions, given sufficient time and liquid nitrogen, provided that pipe sizes are not too large. Light hydrocarbons
present a much greater problem due to their low viscosities and low freezing
points. In small pipe sizes, freezing these materials may be attempted,
although it is usually prudent to carry out experiments, or computer-based
numerical simulations before attempting operations with this class of substance.
Recent experimental work has used styrene
(with which we have also used our heat-flux
system), tetradecane, exxsol-d140.
Contact our London Office
if you have a pipefreezing requirement which involves freezing something
unusual.
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