Note: Descriptions are shown in the official language in which they were submitted.
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IN8ULATED PIPE APPARATU8
FIELD OF THE INVE~TION
This invention relates to an insulated pipe
apparatus for use as a conduit in a high or low
temperature fluid distribution system, and more
particularly to a method and means of manufacturing an
insulated pipe apparatus with an insulation system that is
easily manufactured and which is readily adapted for use
in a wide variety of thicknesses each for a wide variety
of conduit diameters.
~ACXGROUND OF THE INVENTION
Insulated pipe structures are commonly used in
heat distribution systems, where hot fluid or steam is
distributed to a desired location, or in cryogenic
applications. These systems can be used in residential or
industrial applications such as heating buildings or
maintaining the temperature of a particular system.
In one prior pipe apparatus described in U.S.
Patent No. 4,700,751, an insulated pipe apparatus includes
an inner conduit for carrying fluids. Insulating material
in the form of a sleeve surrounds and extends
substantially the length of the conduit. A plurality of
elongated voids are defined around the insulating
material. A fibreglass reinforced rigid outer casing
surrounds the voids. The elongated voids are continuous
and are of constant cross-section and means are provided
for sealing the ends of the pipe apparatus.
While pipe apparatus described in the above U.S.
patent has proven useful, it requires a sleeve of
insulating material which is formed with an internal
diameter which substantially matches the outside diameter
of the inner conduit. Since this type of insulated pipe
is manufactured in a wide variety of diameters,
manufacturers must maintain an inventory of
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insulated sleeves in a variety of sizes. These sizes
may vary from a 1" diameter pipe with insulation
thickness from 1" through 6" to a 36" pipe with
insulation thickness from 1" to 12" (in 1/2
increments). Therefore, an inventory of literally
hundreds of sizes is required. Maintaining this
inventory i5 expensive, and in many ca~es an insulated
sleeve of a desired size may not be available when
desi~ed,
An object of the present invention is to
provide a method and means of manufacturing an insulated
pipe apparatus in a wide variety of sizes and having all
of the advantages of the pipe apparatus described in the
above-referenced U.S. patent while maintaining an
inventory of insulating material-in a relatively few
sizes.
Another object of the present invention is to
reduce the cost of manufacturing an insulated pipe
apparatus.
Another object of the present invention is to
provide a drainable, dryable, pressure testable,
preinsulated pipe apparatus with enhanced insulative
properties and improved consistency.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and advantages will
become apparent upon reference to the detailed
description of the invention and the accompanying
drawing wherein:
Figure 1 is a view in perspective of a prior
art insulating sleeve.
Figure 2A is a view in perspective of the
present insulating sleeve prior to processing.
Figure 2B is a view in perspective of the
preferred embodiment of the insulated sleeve of the
present invention.
Figure 3 is a cross-sectioned view of an
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insulated pipe apparatus constructed with the insulated
sleeve of the present invention.
Figure 4 is a cut away view in perspective of the
insulated pipe apparatus of ~igure 3.
Figures 5A and 5B show alternative preferred
configurations for venting, drying, draining and air
testing ports extending from an annular void through an
end seal to external equipment.
Figure 6 is a cut away view in perspective
showing an insulated pipe apparatus with an attached end
cover.
Figure 7 is a cut away view in perspective of an
alternate embodiment of the present invention.
8U~laRY OF THE INVENTION
Briefly described, the present invention
comprises an insulated pipe apparatus which includes a
substantially cylindrical inner conduit for carrying
fluids. Compressible insulating material surrounds the
inner conduit and extends substantially the length of the
inner conduit. The compressible insulating material is
formed of a sheet of approximately trapezoidal sections
defined by "V"-shaped grooves which when wrapped around
the inner conduit form a circumferentially and
longitudinally contiguous sleeve along the length of the
inner conduit. A rigid outer casing resistant to
mechanical stress and moisture ingress, is disposed
coaxial and coextensive with the inner conduit and
surrounds the compressible insulating material.
A means defining a plurality of longitudinal
elongated voids may be disposed between the outer casing
and the compressible insulating material, wherein the
elongated voids are of substantially constant cross-
section and coextensive with the compressible insulating
material. Interconnecting means for interconnecting the
elongated voids and sealing the ends of the insulated pipe
apparatus are disposed between the outer surface of the
inner conduit and the rigid outer casing. The present
invention further
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contemplates the use of coupling means for connecting
the inner conduit to external equipment.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is adapted for use withan insulated pipe apparatus of the type described in
U.S. Patent No. 4,700,751 by substituting the present
insulating sleeve with the insulating sleeve described
- therein. Referring now to ~igure 1, a prior art
insulating sleeve is shown in perspective. In prior
insulated pipe structures, insulated sleeves are
constructed in sizes which match particular diameters o
conduits. In other words, for each diameter of conduit,
an insulated sleeve having a matching inner diameter is
required. In addition, for each inner diameter size, a
number of insulation thicknesses are required. The most
common insulated sleeve is shown in Figure 1, wherein
~ the insulated sleeve i5 formed in two matching sections
12, 14 which are joined at seams 16 over the inner
conduit 18 peior to encasing the structure. Since each
sleeve half is subject to various manufacturing
tolerances, the butt edges which comprise seams 16 do
not close completely, thus allowing heat dissipation
through the seams.
Referring now to Figure 2A, the present
invention contemplates the use of a single molded flat
sheet of insulating material 20 which may typically be
approximately 6 inches thick prior to preparation. The
sheet 20 is then cut or sliced along line 21 to a
desired thickness as required by a particular
application. The present invention also contemplates
the use of several standard thicknesses of single molded
flat sheet of insulating material 20 that can be
directly "V"-grooved for wrapping around inner conduit
22. In the preferred practice of the present invention
the insulating material 20 may suitably be constructed
with mine~al ~vl, urethane foam, foam glass, fiberglass
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or calcium silicate insulation boards which are
available from many insulation manufacturers. A
plurality of "V" shaped grooves 26 are then cut in sheet
20 as shown in Figure 2B. The "V" shaped grooves allow
the sheet 20 to be wrapped around inner conduit 22. "V"
grooved insulating boards have been offered in the past
for use in field applications on bare pipes. However,
this material is not suitable for use in a
pre-manufactured inslllated pipe because it lacks the
required structural integrity offered by the surrounding
enveloped corregated material 3B and because the "V"
grooves in field application material are prone to heat
loss. The present invention overcomes this problem by
using a comp~essible insulating material and disposing
the vertical angle of the walls 28 defining the "V"
groove at an angle which allows the walls 28 to compress
against each other when the insulating board iæ wrapped
around inner conduit 22 as shown at junctions 30. In
the preferred practice of the present invention, the
walls 28 are disposed at an angle of 10 to 15 degrees
with.respect to the vertical axis of the ~V" groove.
When insulating board 20 is completely wrapped around
inner conduit 22 the junctions 30 are under compression
thus providing improved structural integrity and
improved insulation at junctions 30. In addition to the
above, the insulating qualities of the insulating board
20 are further improved because of the additional radial
compression of the insulation caused by the tension of
the glass filaments 39 as they wrap around the
corregated material 38 squeezing it against the
insulation 30 during the filament winding process as
will be discussed in more detail below.
Once in~ulating board 20 is completely wrapped
around inner conduit 22, it is ready to be assembled in
accordanc~ ~7ith the method described in U.S. Patent No.
4,700,751 and which is explained by reference to Figures
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3 and 4. The pipe appacatus 32 includes an inner
conduit 22 for carrying fluids. The inner conduit 22
may be composed of fiberglass, PVC plastic, copper,
steel, steel alloy or other types of pipe materials.
Insulating material 20 is wrapped around inner conduit
22 in accordance with the scheme described above. A
rigid outer casing 34 surrourlds in~ulating material 20.
The rigid outer casing 34 is preferably formed of
reinforced fiberglass manufactured in accordance with
the teachings of U.S. Patent No. 4l700,751.
The pipe apparatus 32 further includes means 36
1 fnr creating a plurality of elongated voids between
casing 34 and sleeve of insulating material 20. Means
36 shown in Figures 3 and 4 comprises a corrugated
material 38, preferably made of fiberglass to resist
moisture penetration and corrosion and to increase
mechanical strength. It extends substantially the
length of casing 34. The cocrugated material 38
includes ridges 40 which define continuous and constant
cross-section voids 40 which extend along the surface of
insulating material 38 for substantially its entire
length. The voids thus formed enable the free flow of
air for venting, drying, air testing of the pipe
apparatus and for the free flow of moisture for draining
the voids. This increases the insulative properties of -
the apparatus and decreases the likelihood of corrosion
of the inner conduit.
The insulated pipe structure 32 is readily
adapted for use with the end seal shown in Figure 6 and
the coupling and interconnecting means shown in Figures
5A and SB for innerconnecting the continuous elongated
voids 40, for constructing insulated pipe structures of
desired lengths, and for coupling the insulated pipe to
external equipment. The interconnecting means comprises
an annular void 46. The corrugated material 36
terminates a sho~ dis~nce froln the inner face of disk
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52 of end seal 44. The insulating material 22 and the
rigid outeL casing 34 extend beyond the co~rugated
material 36 and contact the inner face of the disk 52,
thus defining the annular void 46. The end seal 44
preferably is in the form of a cap comprising the disk
52 and a cylindrical sleeve S4. The disk 52 is sealed
to the end of the rigid outer casing 34 and covers the
entire cross-section of the insulated pipe apparatus
except for the inner conduit 22 which passes through
central opening 56 in the disk 52. The inner conduit is
sealed around its circumference to the disk 52. The
inner face of the disk 52 defines one side of the
annular void 46. The cylindrical sleeve 54 is
continuous with the disk 52 and surrounds and is sealed
to the rigid outer casing 34. Heat in the inner conduit
is dissipated by conduction to the disk 52 and thence to
the cylindrical sleeve 54. This protects the rigid outer
casing 34 from thermal damage.
As discussed in ~.S. Patent No. 4,700,751, the
rigid outer casing 34 is composed of fiberglass
rein.forced material which is a composite consisting of a
matrix of resin in which fibrous reinforcements are
contained. Commercially available glass fibers have a
tensile strength of between 250,000 to 800,000 p.s.i.
Polyester resins are used to bind the fibers in a rigid
structure. The resins are the poly-condensation
products of dicarboxylic acids and dihydroxy alcohols.
Organic peroxides are used to catalyze the polyester
resin and initiate the copolymerization reaction. The
peroxides decompose to reduce the free radicals. These
free radicals are attracted to points by unsaturation
(reactive sites) and initiate the polymerization
reactions. This increases the casing's ability to
prevent moisture from entering the pipe apparatus and
from coming into Col:t~Ct wittl the insulating material
14. That ability i~ pecially usef~ll in underground
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situations where, as pointed out earlier, water is
almost always present. In above-ground applications,
ultraviolet inhibitors are added to the resin to resist
damage from the sun.
The rigid outer casing comprises several
wrappings or layers of this fiber-resin matrix. The
fiber reinforcing is spirally wrapped in layers as
illustrated irl ~igure 4. Filaments 26 are wound in such
a way so as to maximize their strength to resist
buckling while minimizing the weiqht of the outer
casing. Using a Netting analysis, it has been found
that the helix angle of the filaments should be
approximately 55 degrees and more precisely 54.75
degrees, in order to best compensate for the difference
between hoop (radial~ stresses and longitudinal
stresses.
Pigures 5A and 5B show preferred coupling means
for the connecting annular void 46 with external
equipment, whether the annular void is defined by
cutting back the insulating material 22 or the
corrugated material 36. The coupling is achieved by use
of a plurality of tubular ports 48 which extend from
the annular void 46 through the disk 52 or through the
cylindrical sleeve 54 of the end seal 44 and terminate
outside the end seal. The ports are sealed around their
circumference to the disk 52 or to the cylindrical
sleeve 54 and preferably terminate with a threaded or
other configuration suitable for reversible connection
to external equipment such as gauges, compressed gas
supplies, etc.
The pipe apparatus according to the present
invention preferably has a gel coat applied to the outer
surface of the rigid outer casing 34. The gel coat is
made from isophtalic acid polyester resins which are
thickened by the addition of the thixotropic agents,
such as aerosil. Pigments and ultraviolet inhibitors
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are also added in above-ground applications. This
chemically links with the substrate and provides the
! insulated pipe apparatus of the present invention with
I added resiliency, long life exposure properties, and
! aesthetic appeal.
Referring now to Figure 7, the present
invention is also adapted for use in insulated pipe
structures whlch do not require the draining and venting
means described above. In the embodiment shown in
Figure 7, the insulating material 22 is wrapped around
the inner conduit 20 in the manner described above. The
~5 outer casing 34 is then disposed in direct contact with
insulating material 22 such that the insulating material
is in radial compression as described above. The
struc~ure is then fitted with an end seal 44 of the type
shown in Figure 6. Sections of insulated pipe may be
coupled by joining the inner conduits of the various
insulated pipe sections.
In summary, an insulated pipe with improved
insulation has been described. Accordingly, other uses
and modification will be apparent to a person of
ordinary skill in the art without departing from the
scope of the present invention.
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