CA1038745A - Telescoping reflective thermal insulating structure - Google Patents

Abstract

TELESCOPING REFLECTIVE THERMAL INSULATING STRUCTURE
Abstract of the Disclosure An axially extensible and contractable reflec-tive thermal insulative structure is disclosed, comprised of two telescoping sections, each containing a plurality of reflective metal sheets, adjacent pairs of sheets are disposed such that telescoping motion is permitted while simultaneously proper spacing of the sheets is maintained. The insulation unit may be flat or curved.
In a preferred embodiment a restraining means controls the telescoping motion while preventing unintentional disassembly of the unit.

Description

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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 .~. : - .
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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' i ~ 69 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 , 8'741 ~i :
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 ",,: . ' , ' ' ' ' -7gl~ ~
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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Claims (10)

WHAT I CLAIM IS:

1. Pin extensible reflective metallic thermal insulation structure comprising:
(a) a first section; and (b) a second section;
(c) each of said sections comprising an inner plate and an outer plate and disposed therebetween a plurality of reflective sheets, said sheets being separated one from another by spacer means;
(d) each of said sheets in one of said sections slidably abutting a corresponding plate in the other of said sections;
(e) the outer plate of said first section slid-ably abutting and inwardly disposed of said outer plate of said second section;
(f) each sequential pair of sheets of one sec-tion being disposed between sequential pairs of sheets of said other section, and (g) restraining means cooperating with said outer plate of said second section to restrict the outward movement thereof;
whereby said sections can telescopically move relative to each other while simultaneously maintaining proper spacing of the sheets in each section.

2. The structure of Claim 1 wherein said inner plate of said first section slidably abuts and is disposed outwardly of said inner plate of said second section.

3. The structure of Claim 2 wherein said structure has an overall curved shape.

4. The structure of Claim 3 wherein said curved shape is semicylindrical.

5. The structure of Claim 2 wherein said structure has an overall flat shape.

6. The structure of Claim 2 wherein said restraining means comprises a rod member passing through all of said plates and sheets and secured on the inner and outer surfaces of said structure.

7. The structure of Claim 6 wherein said rod member comprises a bolt which is secured by a nut.

8. The structure of Claim 6 wherein said rod member comprises an unthreaded rod which is secured by a speed nut.

9. The structure of Claim 6 wherein each plate and sheet of said first section has therein a longitudinal slot and each plate and sheet of said second section has therein a clearance hole, all holes and slots being aligned, and said rod member passes through said slots and holes.

10. The structure of Claim 9 wherein said slots are positioned longitudinally inwardly of the end extremity of each sheet whereby said rod member prevents unintentional disassembly of said structure.