|
Plasti-Fab insulation is excellent
for insulating cold environments, such as pipes and vessels
containing cold liquids or gases at temperature from normal
room temperature down to and including cryogenic temperatures
- i.e., below -100 °C (-150 °F). Properly shaped insulation
coverings efficiently control condensation and heat transfer.
At cryogenic temperatures, extreme care
is necessary to ensure that vapour barriers are complete and
adequate. PlastiSpan insulation is not suitable for insulating
environments which will be maintained at heat service temperatures
greater than 60 °C (140 °F).
Insulation can be used to protect the
contents of the pipe or vessel from the effects of a freezing
exterior temperature. Examples of this application would be
utility and sewer lines buried in an area where the ground
temperature will be below freezing or which are exposed to
the weather for other reasons. Methods for accomplishing this
are dealt with the Plasti-Fab brochure 'Utilities Insulation'.
Plasti-Fab fabricates PlastiSpan insulation
for pipes and vessels to provide maximum thermal efficiency,
maximum physical properties and maximum economy to suit the
requirements of the application. PlastiSpan insulation is
a lightweight insulation which is easy to handle, ship and
install.
Pipe and vessel coverings are fabricated
with a butt joint or an optional tongue and groove longitudinal
joint. A factory applied foil jacketing can be supplied to
most pipe coverings or to vessel coverings in order to provide
a vapour barrier.
PlastiSpan insulation meeting the requirements of CAN/ULC-S701-97,
Type 1 has the lowest density of all the plastic foams used
for pipe and vessel coverings. It is the most economical foam
insulation and provides best value in where a vapour barrier is used, PlastiSpan provides a very reasonably priced installation.
PlastiSpanHD insulation meeting the requirements of CAN/ULC-S701-97,
Type 2 is higher in density than PlastiSpan insulation, Type
1. Its physical, thermal, and water vapour permeance are also
higher, yet it remains economical.
For both types, the vapour barrier may
be omitted if the ambient temperature is below 21 °C (70
°F) at all times and the differential between the pipe
surface and the ambient atmosphere is less than 17 °C
(30 °F).
The basic design criteria for selecting insulation thickness
on pipes handling cold liquids or gases is the amount required
to prevent condensation on the surface of the pipe covering.
This is due to the volume and velocity of the contents of
the pipe, which provides an almost unlimited capacity to absorb
heat.
Multiple layer insulation with joints staggered between layers
is recommended where the insulation thickness is over 76 mm
(3')' or where the operating temperatures are below -29°
C (-21° F). The Dimensional Standards Table on page 12
makes it possible to specify two-layer pipe coverings using
two standard-dimension single layered pipe covering. The two-layer
covering with joints staggered offers a better insulation
system where the operating temperatures are in the severe
service range (i.e.,below -29° C (-21° F).
Where liquids or gases are to be stored in vessels for periods
of time the heat gain or loss of the vessel is the criteria
which will determine the insulation thickness. Heat gain is
particularly critical, since it can cost up to ten times more
in terms of capital equipment and operating costs to restore
a low temperature system to equilibrium than it does for a
high temperature system.
Large vessels are often insulated to
reduce the heat gain of the contents over a period of time.
If the specific heat of the contents is known, the following
tables of heat gain through the vessel walls would allow calculation
of the residence time for the contents to reach a given temperature
or the capacity of cooling equipment required to keep contents
at a certain temperature.
*Temperature Differential is
between average air temperature and average temperature of
contents. Table considers only thermal resistance of insulation
and surface thermal resistance with 15 mph (24 km/h) wind.
Vessel wall and jacketing are both assumed to be metal (no
thermal resistance). Vessels are assumed to be indoors or
under a sun screen. If the vessel is exposed to the sun, the
direct heat load of the sun must be considered. See ASHRAE
Handbook of Fundamentals.
PlastiSpan pipe and vessel coverings
are almost always covered with metal jacketing. This jacketing
does not have sealed joints and a vapour barrier is usually
required under the metal jacket. This may be supplied as a
factory applied foil jacket, a field applied foil jacket,
or a field applied vapour barrier mastic. Selection depends
on the degree of vapour barrier required and the field installation
conditions to be expected. When a laminated foil is used as
a vapour barrier it is installed with the foil side against
the pipe covering and the kraft paper side against the metal
jacketing.
Permanently Fire Retardant Vapour Barrier Jacketing.
0.0007 aluminum foil, flame resistant adhesive, fibreglass
6 x 6 reinforcing, white chemically treated permanent fire
retardant non-bleachable 45 lb. Kraft paper.
·
Tensile Strength Machine Direction 50 psi (346 kPa).
· (ASTM D 828) Cross
Direction 50 psi (346 kPa).
· Puncture Beach (ASTM
D 781-44T) 50 psi (346 kPa).
· Water Vapour Permeance
(100 in2/24 hrs) 0.01 grains
· (ASTM E 96-53T(A)
(0.03 * ng/Pa * s * m)
· Delamination (oven
aged 120° F, 95% R.H.) none.
· Mullen Burst Test
(ASTM 774-63T) 70 psi (482 kPa)
Please contact us for further information
on the use of PlastiSpan insulation board for the above types
of construction.
|
