Roxul Industrial Insulation Process - Manual (Page 85)

1. System solutions
1.8 Cold boxes
Many industrial applications use gases such as
oxygen, nitrogen and argon. These gases are
obtained using cryogenic gas separation
technology, whereby air is condensed and
converted into a liquid. Afterwards, the various
elements can be separated using fractional
distillation.
So-called air separation plants are characterized
by an extremely low temperature of as low as
approximately -328 °F (-200 °C). In addition to the
risk of water and ice forming at this cryogenic
temperature, there is also the risk of pure oxygen
condensing against the cold parts of the system.
The presence of oil and grease may be enough
to cause the high concentration of oxygen to
spontaneously combust.
This is obviously an extremely hazardous
situation. The presence of oil and grease must
therefore be avoided at all times. It is vitally
important to well insulate all cold parts of the
system, such as vessels and pipes. Strict
specifications regarding the insulation are
therefore essential. A standard, frequently applied
in Europe, for the insulation of air separation
plants is the AGI Q 118 standard “insulation work
on air separation plants”. This standard describes
in detail the various parts of the installation and
the insulation to be applied. The construction
method naturally depends on the application.
The following instructions are limited
to the insulation of so-called cold boxes.
Cold boxes
An important component in gas separation plants
are the so-called “cold boxes”. Cold boxes are
(pressure) vessels that hold a gas or liquid at a
very low temperature. The distinctive feature of
cold boxes is the double-wall construction, which
allows the insulation to be fitted between the
inner and outer walls. The cold box is sealed after
the insulation has been fitted, so the insulation
can no longer come into contact with, for example,
water, snow, dust and contaminants.
Choice of insulation
The choice of insulation material depends on
a variety of parameters, including the user
requirement, standards (e.g. AGI Q118), the
operating temperature and the accessibility of the
installation. In many cases, mineral wool fibers
are used (e.g. ProRox
® GR 903), which contain a
very low proportion of organic substances- the
so-called “Linde Quality”. This can be easily
injected into the vessel and has a very long
lifespan. The material is easily removed for
inspection purposes.
Fitting the insulation
In compliance with the AGI Q118 standard, the
fibers are fitted manually or using an injection
technique. The hollow spaces in the installation
must be free of water and other liquids and
contaminants. All filling openings (and non-filling
openings) must be sealed. An optimum result is
achieved by pulling the packaged, loose fibers
apart before injecting or shaking them into the
vessel. The ProRox
® GR 903 must be injected or
shaken into the unit in even layers.
If necessary, the wool can then be tamped to
achieve the required density. To avoid damage to
the installation, manually filling certain parts of
the installation may be advisable. The ultimate
density of the fitted wool depends on how it is
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