Note: Descriptions are shown in the official language in which they were submitted.
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TEL:E:SCOPING REFLECTIVE TH R~L INSULATING STRUCTURE
Back~round of the Invention
Field of the Invention
The invention herein relates to an all-
metallic reflective structure for use as thermal
insulation for pipes, vessels, walls or the like.
Description of the Prior Art
The concept of reflective thermal insula-
tion has heen known for some years. A number of
1~ all-metal devices have been described in the prior
art for the thermal insulation of pipes, vessels
and other heated objects by reflection of radiant
energy. Typical examples of reflective insulating -~
structures which have found commercial success are
-l- shown in U.S. Patents 2,841,203 and 3,028,278 (both ;
, to Gronemeyer~ and U.S. Patent 3,]90,412 ~o Rutter
et al). Reflective insulations, which are made in both
curved and flat configurations, generally consist of
inner and outer metallic plates between which are
21) placed a plurality of thinner metallic sheets. The
sheets are separated from each other and from the
shells by various types of spacing means, all of
which are designed to provide minimum contact and ;
thus minimum area for conductive heat 1OW. In the
aforementioned patents such spacer means include
slotted brackets and cone-shaped stand-offs. The ~ ;
sheets are generally polished to provide maximum
re~lectivity.
The all-metallic reflective insulations
differ substantially from the conventional thermal
insulation which comprises blocks of refractory or
low-conductivity material, generally ceramics or
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1 low-conductivity masses of fibrous materials such
as glass fibers or mineral wool. The metallic sheet
configuration of the reflective insulation provides
a much stronger insulation structure than is found
wi.th the brittle ceramic blocks or the fragile fibrous
structures. Further, the open structure of the re-
`` flective insulation permits easy cleaning of the in-
terior of the insulation, a distinct advantage when
the insulation is contaminated with corrosive or
radioactive liquids due to such accidents as pip~
ruptures or vessel leakages. Such advantages, as well `
as the efficient insulating properties, have led to
`l enthusiastic commercial acceptance of reflective in~
sulations, particularly in the nuclear power industry.
As the commercial use of such insulations
hai expanded, however, serious problems of fabrication
and installation have been encountered. One of the
most commonly occurring problems has been that of mis~
fit of parts. Unlike fibrous or ceramic insulations,
which are generally cut to fit the pipes or other
objects to be insulated on the job site with simple
tools such as portable saws, the complex metallic
structure of the reflective insulations virtually
requires that they be fabricated in a sheet metal
shop and transported to the job site for installation.
1 Normally~ the sheet metal fabricator designs and ~ ~-
;, builds the reflective insulation units from the con-
struction design drawings of the piping vessels or
other objects to be insulated supplied by the builder
of those objects. Very often, however, it is dis-
`) covered when the fabricated reflective insulation
~ units are delivered to the job site, that the workmen
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1 who erected the structure to be insulated deviated
slightly from the engineering specifications and
drawings in the actual dimensions of the finished
structure. The fabricated reflective insulation
unit, which was constructed to the exact engineering
specifications, thus does not properly fit on the
actual structure in the field. As an example, the ~;
engineering drawing might call for a section of pipe -~
, to be 36 inches long and the insulation manufacturer,
therefore, fabricates a reflective pipe insulation ~ ~
also 36 inches long. On delivery to the fieldl how- ;
ever, it is discovered that the pipefitter who in-
~; stalled the pi.pe misaligned it slightly, so that its -
, actual measured length is 37 inches~ The reflective
¦ insulation structure must, therefore, be completely
reabricated or modified to comp~nsate for the non- ~ ;
specification construction. A similar situation would,
of course, exist if the structure were slightly smaller
than specification; e.g., the pipe were 35 inches long
instead of the specified 36 inches. It has been sug-
gested that this problem of misfitting parts could be
j,! resolved by working directly from dimensions taken in
the field. However, such a procedure is extremely
time~consuming, since it requires that every structure
to be insulated must be individually measured. Further,
it substantially delays the completion of construction
projects, for fabrication of the reflective insulation
cannot begin until the structure to be insulated is
entirely assembled and in place. This, of course, com-
pletely defeats the scheduling principle which calls
for insulation to be available for installation as soon
as each portion of the construction project is completed.
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1 The problem has been further perplexing in
that it has hindered attempts of insulation manufac~
turers to design and supply insulation units of
standard sizes. Since present units cannot be manu-
factured in quantity and held in inventory for use on
a variety of proj~cts, but rather each insulation
section must be individuall~ tailored to a particular
size, reflective insulation has been unduly expensive.
This has placed it at a competitive disadvantage as
compared to the ceramic and fibrous insulations which
can be readily cut to size on the job.
Consequently, it would be of considerable
bene~it to provide a reflective insulation structure ~ -
which incorporates a degree of adjustability or ex~
- tensibility, such that it may be :readily ad~usted on
the job site to compensate for common discrepancies
between design dimensions and the actual dimensions
found on the completed structure.
It would further be of considerable benefit ~ -
to provide a reflective insulation structure which
may be readily fabxicated in quantity in predetermined
ll standard sizes, such that the economic benefits of
3 volume production could be obtained while yet per-
~l mitting the adaptability of sizes for which custom
gl fitting is now required.
Telescoping structures are also known in the
art. The old and conventional assemhlage of a single
male section slidably fitted within a single female
section is shown, e.g., in U.S. Patents 219,098; 372,075,
and 1,256,654. A simple refinement on that arrangement,
in which each section contains two rigid plates, with
the plates o the female section disposed outwardly of
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1 the corresponding plates of the male section, is
shown in U.S. Patent 724,210. A solid insulation
structure, in which -the abutting solid insulation
(asbestos) blocks slide apart to expose a reflective
surface, i5 shown in U.S. Patent 2,742,384.
Objects of the Inventlon
It is an object of this invention to des-
cribe a reflective insulation structure which is
readily adjustable to compensate for deviation in
the design size of the structures to be insulated.
It is also an object of this invention to
provide a reflective insulation structure which may ;
be readily fabricated to standard dimensions while
providing means for adjustment.
Brief Summary of the Invention
~ ~ .
The invention herein is an extensible re~
flective thermal insulation structure which is com- ;
posed of two telescoping sections. Each section con-
tains an inner plate and an outer plate and, spaced
therebetween, a plurality of reflective sheets, which
sheets are spaced one from another by spacer means
cooperating therewith. The outer plate of the first
section is slidably positioned inwardly of the outer
plate of the second section. Each sheet in one sec-
tion slidably abuts a corresponding sheet in the other
section. Ad~acent pairs of sheets in one section have
terminal portions positioned between adjacent pairs
of sheets in the other section and adjacent pairs co-
operate with each other to maintain relative spacing
of the reflective sheets. Preferentially, that pair
of sheets in the one section which are positioned
between the opposite pair of sheets have between
1 them stand-off means positioned adjacent to the
telescoping sliding terminal portions. Restraining
means are attached to at least the outer plate of
the second section to prevent outward expansion of
th~ structure. Praferably the restraining means is
attached to the inner and outer shells of the second
section and passes through the inner and outer plates -~
of the first section and all sheets. The inner and
outer shells and the sheets of the first section have
means cooperating with the restraining means to permit
telescoping movement of the sections relative to each
other but yet preventing separation of the two sec-
tions. lrhe insulating structure may be flat to in~
sulate wall sections or curved to insulate vessels,
pipe~ and similar curved objects. In a commonly used
curved configuration, the insulation assumes a hollow
cylindrical shape and is used to insulate lengths of
pipe.
Brief Description of the Drawings
~' 2() FIGS. la and lb illustrate respectively per-
spective views of a circular (cylindrical~ reflective
insulation section in place surrounding a pipe to be ~ ,~
insulated and a flat panel structure in place against
a flat surface to be insulated.
, FIG. 2 is an elevation view o~ the curved
structure of FIG. la, showing in a partial cut-away
section the internal telescoping structure of the
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insulation.
FIG. 3 is a partial cross-sectional view
taken on plane 3-3 of FIG. 2 showing the arrangement
o the reflective sheets and a typical means for
maintaining separation between the sheets.
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1 FIGS. 4a and 4b are enlarged schematic
detailed drawings of the telescoping structure of the
insulation, with FIG. 4b additionally illustrating
means separating adjacent reflective sheets.
FIG. 5 is an exploded view illustrating
schematically a means permitting telescoping movament
while restraining separation, misalignment, or rotation. -
. Detailed Description and Preferred Embodiments
The invention herein is most readily under-
stood by reference to the accompanying drawings. Two
common configurations of the reflective insulation
structure are shown in FIGS. la and lb. (Other con~
figurations have also been used and are well ]cnown to
those skilled in the art; as will be evident, these
are also applicable to the present invention.) FIG.
la shows a cylindrical pipe insulation 2 disposed sur-
roundLng a hot pipe 4 which is to ~e insulated. The
pipe insulation is normally constructed in two semi~
cylindxical sections 6 and 8 and dimensioned with inner
J. 20 and oute~ diameters such that the sections can be fitted
~! closely around the pipe and then sealed together to
form a continuous cylindrical insulating structure.
Bands, clamps and other conventional devices (not
shown~ may be used to secure the cylindrical structure.
Conventionally, each semicylindrical structure has at-
tached thereto at each end arcuate end plates such as
10 and 12 respectively. Such end plates of a section
serve to close off the internal space of the structure
and to provide support means to maintain the cylindrical
shape and to properly position the insulation about the
pipe. The outer shells of the two semicylindrical halves
are conventionally extended slightly, as shown at 7 and
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1 9, to provide an overlap covering the joint between
the halves.
FIG. lb shows a flat reflective insulation ~;
structure 14 positioned to insulate a hot flat surface ;~
4'. This structure contains rigid sidewalls such as
16, a top (or outer plate) 18 and a bottom (or inner
plate) 20. This structure is mounted in place on the
surface to be insulated by clamps, bands or other means. ~ ~ -
Disposed within each of the structures is a
plurality of reflective metal plates generally designated
22. The number of plakes, their spacing and the total
thickness of the insulation will be determined by the
hot side temperature and the amount of temperature drop
to be obtained. The sheets are polished and are sepa~
rated one from another by separation means such as the
cone-shaped projections or:stand-,~.,f~s 24. Such projec~
~: tions are shown in greater detail in aforesaid U.S.
Patent 3l190,412. Where there are no end plates, as : ::
in the flat structure 14, flange 26 an~/or strap 28 may
2() be used to restrain the reflective sheets and prevent
them from coming out of the outer framework.
Thus far, the general structure of the re- ;
flective insulation of this invention is conventional,
such being shown in the aforesaid U.S. patents to
Gronemeyer and Rutter et al. I~ will be immediately .::
' apparent, however, that these conventional structures .
,, are necessarily of fixed dimensions and cannot be
altered from these dimensions without substantial
refabrication. The improved structure to be described
in the subsequent portions of this specification over-
comes this severe deficiency of the prior art structures
and provides an insulation which is readily adjustable
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1 to meet the varying conditions found in the field.
In the improved structure herein, each in-
sulation structure is divided into two sections, a
first or female section 30 and a second or male sec-
tion 32. (For the purposes of this descxiption, each
semicylindrical portion of the pipe insulation shall
be considered as a separate structure.) These sections
are constructed such that the outer shell or plate
34 of second section 32 slidably engages the outer
shell or plate 36 of first section 30 and is disposed
inwardly thereof. Inner shell or plate 38 of second
section 32 is similarly slidably engaged with inner
shell or plate 40 o~ first section 30 and generally
also lies inwardly thereof. tIt is possible to design
the structure such that inner she:Ll 38 lies outwardly
of inner shell 40, but such a structure is considerably ~ ~;
j~ more complex than that where the positions are reversed, `~
f~ ~nd therefore the structure previously described is
much preferred.) Each of sections 30 and 32 contains
Z/) its own set of re1ective insulation sheets 22 or 22',
respectively. These are essentially longitudinally
co-extensive with the inner and outer shells of the
section. Normally, each individual sheet overlaps
with and slidably engages a correspondiny sheet o
the other section, as is shown in detail in FIGS. 4a
and 4b. (I~ is po~sible to desiyn a structure wherein
one section contains more reflective sheets than does
the other section, and therefore some of the excess
sheets may not be in slidable relationship to sheets
- 30 of the former section. However, no technical advantage
~ is gained by such an arrangement and since it merely
; increases the complexity of the structure unduly, this
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1 arrangement is not preferred.)
The details of the novel telescoping struc- ;
ture of this invention, which has the dual function
; of permitting telescoping and maintaining the required
; separation o~ the reflective sheets, is evident from
inspection of FIGS. 4a and 4b. As indicated, each
drawing shows in partial section a portion of sections
30 and 32. In FIG. 4a four pairs o~ corresponding
plates or sheets, designated respectively 42a and 42bt
44a and 44b, 46a and 46b and 48a and 48b are shown.
In FI&. 4b portions of many of the same sheets are
shown, and also portions of the outer shells 34 and 36
~ of respectively sections 32 and 30 are shown.
,~ Each of the pairs of sheets 42a-42b, ..................... ~-
48a-48b slidabl~ engage each other and can move freely
in a longitudinal direction~ Rotative or late~al move-
m~nt is prevented by the strap 28 o~ the flat structure
or an equivalent component in the cylindrical structure
(not shownj but see, e.g., aforesaid U.S~ Patent
2,841,203). Rotation and lateral movement will also be
prevented by the preferred "nut~and-bolt" restraining
means described below. The direction of telescoping
motion is indica~ed by the large arrow between FIGS. 4a
and 4b. Nut and bolt 43, or similar restraining means
passing entirely through the slotted sheets and plates
of section 32, retains those sheets in fixed relation-
ship to each other longitudinally, and permits section
32 to telescope as a unit relative to section 30.
In addition to providing for the telescoping
action of the present structure, the novel structural
design of this invention also acts simultaneously to
maintain the proper spacing between the adjacent sheets
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1 of reflective insulation. Each sequential pair of
sheets in a single section is sandwiched between a pair
of sheets from the o~her section. The tendency of each
pair of sheets to spread apart is thus counteracted by
an equal and opposite spreading tendency of adjacent
pairs from the other section and the equally opposed
forces thus act to maintain the desired spaciny of the
respective sheets. This is clearly illustrated in FIGS.
4a and 4b. In FIG. 4a the pairs A and B of section 30, ~ -
comprising respecti~ely sheets 42a-44a and 46a-48a, are
; disposed between respectiv~ly sequential pairs Y and Z
of section 32, comprising respectively sheets 42b-44b
and 46b~48b. Similarly pair C comprising sheets 44b
and 46b is disposed or sandwiched between sheets 44a
and 46a of pair X of section 30. Thus the tendency
of any pair of sheets su~h as C t~ expand outwardly
and deviate from the desired separation is counter-
acted by the similar tendency of adjacent pairs A and
I B/ with the net result that all sheets tend to maintain
1 20 their desired relative spacing.
~ The cooperating and interacting staggered
I pairs of sheets transmit the separation forces in~
wardly and outwardly until the rigid inner and outer
shells are reached. Desired spacing of the inner
and outer shells is maintained by restraining means.
Since the position of the inner shell or bottom of
first section 30 is fixed by the position of the pipe
4 or surface 4' to be insulated, such restraining
means may comprise, e.g., an inelastic band strapped
., 30 around the outer shell of section 30 in the cylindrical
s configuration 2 or fixed brackets restraining top 18 of
, the 1at configuration 14. Preferred, however, is a
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1 structure in which rod memher 50 passes entirely through
~ all plates and sheets and is secured on the inner and
- outer surfaces of the insulation to limit expansion. In
a typical embodiment of this preferred structure, illus-
trated in FIGS. 2 and 4b, bolt 56 projects entirely
through the inner and outer shells and all sheets of
both sections. A relatively thin, flat head 58 on bolt
56 engages the inner shèll 40 or bottom 20 of first
section 30 and is fixedly attached to the structure by
threading or sliding nut 60 onto the opposite end of
bolt 56 to engage the outer shell 36 or top 18 of sec-
tion 30 (with washer 62 normally being placed between
nut 60 and the surface of outer shell 36 and top 183.
Clearance for bolt head 58 between inner shell 40 or
3 --
!~ bottom 20 of section 30 and the outer surface of pipe
4 or wall 4' can be obtained by the use of stand-off
, 64; such a structure is shown in U.S. Patent 3,648,734.
`! An equivalent result is obtained by use of an unthreaded
rod and speed nut in place of the threaded bolt and nut -~
2() described above. ;
Freedom for telescoping movement is provided
by the incorporation of longitudinal slots 64a ... in
;~ each of the inner and outer shells and sheets of second `~
or male section 32. The corresponding inner and outer ~ -
shells and sheets of first or female section 30 are -
provided with clearance holes 66a, ... for bolt 55.
(A t~pical assemblage, illustrated with outer shells 34
and 36, is shown in exploded view in FIG. 5.) The
structure is therefore free to telescope the entire
length S of the slots 64a, .... . Since the slots do
not extend to the extreme end of the inner and outer
shells and sheets of second section 32, that section
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1 cannot become disengaged from its telescoping rela~
tionship wîth first section 30. This structure thus
both provides for telescoping motion and prevents dis-
assbmely of the unit.
In a typical example of this structure, a
semicylindrical pipe covering intended to insulate
10-inch nominal diameter steel pipe was designed to
a nominal length of 36 inches. Each of sections 30
and 32 was designed to a length of 20 inches, thus
providing a 4-inch overlap. Two-inch slots in the
inner and outer shells and all sheets of section 32
were designed in the longitudinal center of the 4-inch
overlap area; the two slots were circumferentially
spaced apartl being disposed generally at opposite - ;`
sides of the semicylindrical stxucture, approximately
as shown in F~G. 5. Correspondinc; bolt clearance
holes were designed in the inner and outer shell~ and
all sheets of first section 30, also in the longitudinal
center of the overlap area. This arrangement provided
for a 2-inch adjustment in the overall length of the
structure, for an actual adjustable size of 36 + l inch. ~
A preferred arrangement of the sheets i5 shown ~ ;
in FIG. 4b. In this preferred configuration the sepa-
rating means, such as cones 24a, 24b, 24y, and 24z which
separa~e the adjacent pairs, are placed such that the
spacer means in those pairs of plates (e.g., A', B'~
Y' and Z') which are disposed between the next adjacent
pairs, are placed closer to the end extremities of sec-
tions 30 and 32 than are those spacers (cones 24c and
24x3 which separate the other pairs of sheets (such as
C' ~ld X'~. This permits each pair of plates to provide
the maximum thrust against the next adjacent pair, since
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1 in most cases the metal sheets will hava some degree
of flexibility and resilience.
T~e structures herein can be constructed of
a number of different types of metals or alloys. The
particular material chosen will be determined by the
temperatur~s to be encountered, the desired s~rength
of the structure, service life, customer requirements,
corrosion resistance requirements and cost, among other
things. Typical materials which may be used include
steel, titanium and aluminum sheets, with a preferred
material being stainless steel. Surfaces of the sheets
and shells may be and generally are polished to enhance
the reflectivity.
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