U.S. patent number 3,819,468 [Application Number 05/157,433] was granted by the patent office on 1974-06-25 for high temperature insulation module.
This patent grant is currently assigned to Sander Industries, Inc.. Invention is credited to Gary R. Kendrick, John R. Mase, Robert A. Sauder.
United States Patent |
3,819,468 |
Sauder , et al. |
June 25, 1974 |
HIGH TEMPERATURE INSULATION MODULE
Abstract
A ceramic fiber mat attached to the interior wall or surface of
a high temperature chamber or furnace or adapted to overlie an
intermediate insulating member positioned between the mat and a
furnace wall, the fibers in the mat lying in planes generally
perpendicular to the wall, the mat constituting an improved
insulation for the wall where the interior of the chamber or
furnace will be operating at temperatures in excess of 1600.degree.
F.
Inventors: |
Sauder; Robert A. (Emporia,
KS), Kendrick; Gary R. (Emporia, KS), Mase; John R.
(Emporia, KS) |
Assignee: |
Sander Industries, Inc.
(Emporia, KS)
|
Family
ID: |
22563696 |
Appl.
No.: |
05/157,433 |
Filed: |
June 28, 1971 |
Current U.S.
Class: |
428/99; 52/270;
52/699; 156/92; 428/114; 428/124; 428/223; 428/920; 52/506.02;
52/511; 156/71; 336/186; 428/119; 428/131; 428/902 |
Current CPC
Class: |
F27D
1/002 (20130101); Y10T 428/24273 (20150115); Y10S
428/902 (20130101); Y10T 428/24215 (20150115); Y10T
428/24174 (20150115); Y10T 428/24008 (20150115); Y10T
428/24132 (20150115); Y10T 428/249923 (20150401); Y10S
428/92 (20130101) |
Current International
Class: |
F27D
1/00 (20060101); C04b 043/02 () |
Field of
Search: |
;161/151,48,50,60,69,102,152,156,157,170 ;156/71,92 ;336/186
;52/270,699 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: McCamish; Marion E.
Attorney, Agent or Firm: Arnold, White & Durkee
Claims
What is claimed is:
1. An insulation module for lining the interior walls of a furnace,
comprising a rigid block of refractory material having two opposed
flat sides, one side being the cold face for attachment to the
furnace wall and the other side being the hot face for exposure to
the furnace heat, a resilient fiber insulation mat forming at least
the hot face and being held flat within the rigid block prior to
installation on the furnace wall, the fibers in the insulation mat
being generally randomly oriented in planes, such planes being
substantially perpendicular to the hot face.
2. An insulation module according to claim 1 further comprising a
hard surface self-contained within the rigid block prior to
installation on the furnace wall and being hidden beneath the hot
face and against which a fastener can bear to secure the insulation
module to the furnace wall.
3. An insulation module according to claim 1 further comprising an
internal fastener self-contained within the rigid block prior to
installation on the furnace wall and being hidden beneath the hot
face, whereby the cold face of the insulation module may be
fastened to the furnace wall without direct exposure of the
fastener to the heat at the hot face.
4. An insulation module according to claim 1 further comprising a
rigid base forming the cold face of the rigid block, the fiber
insulation mat being affixed to the rigid base.
5. An insulation module according to claim 4 wherein the fiber
insulation mat is secured to the rigid base with an adhesive
bond.
6. An insulation module according to claim 1 wherein the fiber
insulation mat includes a number of strips of fiber insulation cut
from a fiber blanket and arranged in side-by-side relation.
7. An insulation module according to claim 6 further including
strips of fiber insulation attached to the side edges of the rigid
block.
8. An insulation module according to claim 6 wherein the strips of
fiber insulation are connected to each other by a number of wires
extending transversely through the strips.
9. An insulation module for lining the walls of a high temperature
furnace comprising a rigid block of refractory material
pre-assembled prior to installation on the furnace wall, the block
having two opposed flat sides, one side being the cold face for
attachment to the furnace wall and the other side being the hot
face for exposure to furnace heat, a rigid base member forming the
cold face within the rigid block, a resilient fiber insulation mat
being affixed flat to the base member and forming the hot face, the
fibers in the insulation mat being generally randomly oriented in
planes, such planes being substantially perpendicular to the hot
face.
10. An insulation module according to claim 9 wherein the base
member comprises a substantially rectangular mineral block.
11. An insulation module according to claim 9 further comprising an
internal metallic fastener self-contained within the rigid block
prior to installation on the furnace wall and hidden beneath the
hot face, whereby the cold face of the insulation module may be
fastened to the furnace wall without direct exposure of the
fastener to the high temperature heat at the hot face.
12. An insulation module according to claim 9 wherein the fiber
insulation mat includes a number of strips of fiber insulation cut
from a fiber blanket and arranged in side by side relation.
13. An insulation module according to claim 12 including strips of
fiber insulation attached to the side edges of the rigid block.
14. An insulation module according to claim 12 wherein the strips
of fiber insulation are connected to each other by a number of
wires extended transversely through the strips.
15. An insulation module according to claim 14 further including
staples surrounding the wires extending through the strips of fiber
insulation and extending into the base member for attaching the
fiber insulation mat thereto.
16. An insulation module according to claim 9 including a washer
centrally located against the face of the base member at the
interface between the base member and the fiber insulation mat, the
washer being provided with a central hole, the base member being
provided with a hole in alignment with the hole in the washer and
extending through the base member to the hot face, a bolt extended
through the holes in the washer and the base member, and a threaded
nut threadedly engaging the end of the bolt lying adjacent the
washer.
17. An insulation module for lining the walls of a high temperature
furnace comprising a rigid block of refractory material being
preassembled prior to installation on the furnace wall, the block
having two opposed major faces, one major face being the cold face
for attachment to the furnace wall and the other major face being
the hot face for exposure to furnace heat, a rigid base member
forming the cold face within the rigid block, a plurality of strips
of resilient fiber insulation being arranged in side by side
relation and being affixed upon the base member on the side
opposite the cold face to form the hot face of the rigid block, the
strips being cut from a fiber blanket and being arranged in such a
manner that the fibers in such strips are generally randomly
oriented in planes, the planes being substantially perpendicular to
the cold face.
18. An insulation module according to claim 17 further comprising
additional strips of such fiber insulation affixed around the side
edges of the base member adjacent the hot face and being flush with
the hot face.
19. An insulation module for lining the walls of a high temperature
furnace and being preassembled prior to installation,
comprising:
a relatively rigid block of refractory material having a flat side
for attachment to the furnace wall as the cold face, said block
having substantially centrally located opening extending at right
angles to the cold face;
a washer disposed on the surface of said block remote from said hot
face and having a hole therein aligned with the opening in said
block;
a metallic stud extending through said hole in said washer and
through said opening in said block;
a threaded nut threadedly engaging the other end of said stud and
overlying said washer;
a plurality of strips of ceramic fiber blanket disposed in parallel
side-by-side arrangement over the surface of said block remote from
said cold face and forming a ceramic fiber mat completely covering
the face of said block, the fibers in said mat being generally
randomly oriented in planes, the planes being generally
perpendicular to the cold face of said block, said mat also
including strips of ceramic fiber at the side edges thereof
extending downwardly to said cold face to cover the edges of said
block.
20. An insulation-module for lining the walls of a high temperature
furnace and being pre-assembled prior to installation,
comprising:
a substantially rectangular mineral block having a cold face for
attachment to the furnace wall, said mineral block having a
substantially centrally located opening extending through the
thickness of said block;
a washer disposed on the surface of said mineral block opposite the
cold face and having a hole therein aligned with the opening in
said mineral block;
a metallic stud having a shank portion extending through said hole
in said washer and through said opening to the cold face of said
mineral block, the end of said stud adjacent said opposite surface
of said mineral block terminating in a stud tip of relatively
smaller cross-sectional area than said shank portion, said shank
portion leaving a groove therein adjacent said stud tip, a ring
retainer surrounding said shank portion and having radially
inwardly projecting fingers received in said groove;
a ring-shaped arc shield surrounding said stud tip and being
attached to said ring retainer, a threaded nut threadedly engaging
the other end of said stud and overlying said washer;
a plurality of strips of ceramic fiber blanket disposed in parallel
side-by-side arrangement over the surface of said mineral block
remote from said cold face and forming a ceramic fiber mat
completely covering said mineral block, the fibers in said mat
generally being randomly oriented in planes, the planes being
substantially perpendicular to the cold face of said block, said
mat also including strips of ceramic fiber at the side edges
thereof extending downwardly towards said opposite surface of said
mineral block to cover the edges of said mineral block;
a plurality of wire fasteners extending transversely through said
fiber strips and being bent at the opposite ends thereof to hold
said strips together, said wire fasteners being substantially
parallel to each other and to said one surface and being located in
said fiber mat adjacent the interface between said mat and said
mineral block; and
a plurality of hairpin-type fastening means surrounding each wire
fastener and extending into said mineral block to secure said mat
to said mineral block.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application briefly describes, but does not claim, a method
and apparatus for welding which is more fully described and claimed
in U.S. Pat. No. 3,706,870 issued Dec. 19, 1972, in the names of
the inventors Robert A. Sauder and Gary R. Kendrick and entitled
"Method and Apparatus for Stud Welding".
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for
insulating the interior of a high temperature furnace and more
particularly to a ceramic fiber mat constituting the hot face of
the insulation and wherein substantially all of the fibers in the
fiber mat lie in planes which are generally perpendicular to the
various walls of the furnace.
THE PRIOR ART
The problems involved in insulating the interior of a high
temperature furnace or, stated differently, the walls and ceiling
of such a furnace are well known. Historically, the interiors of
high temperature furnaces have been lined with various types of
bricks capable of withstanding these high temperatures. When the
brick lining wears out, however, it is an arduous and
time-consuming task to replace the old brick with a new brick
lining. On the other hand, efforts have been made to insulate the
interior of a furnace where the interior or hot face of the
insulation includes or consists of ceramic fiber material. Ceramic
fiber material, as referred to herein, is generally available in
the form of a ceramic fiber blanket which is customarily
manufactured in a manner similar to the conventional paper-making
process. As such, the fibers which constitute the blanket, (as is
also the case in connection with paper) are oriented in planes
which are generally parallel to the longitudinal direction of
formation of the blanket or sheet. When, as proposed in the past,
lengths of ceramic fiber blanket are placed against a furnace wall
or overlying an intermediate insulating member which, in turn,
would be attached to the furnace wall, the fibers will then be
lying in planes generally parallel to the furnace wall. Also, it is
believed that a majority of these fibers will be lying in a
direction which would tend to be colinear with the direction of
formation of the blanket itself, although a considerable number of
fibers are still in a more or less random disposition in these
planes, Nevertheless, where the fibers are disposed in planes which
are parallel to the furnace wall, there is a tendency for the fiber
blanket material to produce cracks which result from heat
shrinkage.
With certain types of insulation it is recognized that high
temperature problems sometimes involve melting, oxidation and other
types of deterioration of the insulating medium. As far as ceramic
fiber insulation is concerned, the high temperature problems are
generally cracking, delamination (peeling off of the surface
layers), and devitrification, all of which are believed to be
interrelated. At the lower temperatures of the recommended range of
the present invention, namely, 1600.degree. to 2800.degree. F,
devitrification will take place relatively slowly, whereas at the
higher end of the range, devitrification will take place quite
rapidly, followed, in short order, by cracking and/or
delamination.
In retrospect, the prior art broadly discloses the feature of
re-orienting fiber insulation, but only in connection with low
temperature insulation. For example, Di Maio et al. U.S. Pat. No.
2,949,593 and Slayter U.S. Pat. No. 3,012,923 both show the cutting
of strips of fibrous material from a sheet or mat of the same,
arranging the strips in a side-by-side relation to provide an end
fiber exposure, compressing the strips and, while still compressed,
applying an adhesive backing sheet of paper or cloth to one side
edge only of the resulting compressed block; thereafter when the
forces of compression are removed the resulting block will tend to
curl around the adhesive sheet so as to form a suitable insulating
body for pipe or the like. However, the resulting insulation is
necessarily low temperature insulation because the pipe is in
direct contact with the heating or cooling medium which it carries;
the insulation is used on the external surface of the body or pipe
to be insulated; the sole purpose in arranging the strips in an end
or edgewise exposure of the fibers is to permit compression of the
strips so that, after one side edge is secured in place by means of
the backing strip, advantage can be taken of the relatively greater
expansibility along the unsecured edge.
SUMMARY OF THE INVENTION
The present invention involves the use of a ceramic fiber mat which
can be applied either directly to the interior of a
high-temperature furnace or to an intermediate insulating member
which, in turn, is attached to one of the furnace walls. The term
"wall" should be construed as covering any side wall or ceiling,
removable or fixed, the area surrounding any access opening and any
other surface on the interior of the high-temperature chamber where
insulation is required or desired. The term "furnace" should be
construed as covering any high-temperature chamber, oven, heater,
kiln or duct with the understanding that the insulation is always
internal and always "high-temperature", namely capable of operating
at temperatures in excess of 1600.degree. F.
The ceramic fiber mat is preferably made up of strips which are cut
transversely from a length of ceramic fiber blanketing which is
commercially available. The strips are cut from the fiber blanket
in widths that represent the linear distance from the cold face to
the hot face of the insulating fiber mat. The strips which are cut
from the blanket are placed on edge and laid lengthwise adjacent
each other with a sufficient number of strips being employed to
provide a mat of the desired width. Naturally, the thickness of the
fiber blanket from which the strips are cut will determine the
number of strips required to construct the mat. The strips can be
fastened together by wires, or by ceramic cement or mortar which is
preferably employed in the region of the cold face of the mat. The
mat can be applied to the furnace wall or to an intermediate member
by means of a stud welding method or by ceramic cement, mortar, or
the like.
As disclosed herein, the present invention has particular
application for the internal insulation of furnace walls of high
temperature furnaces. For the purposes of the present invention,
"high temperature" will mean temperatures in excess of 1600.degree.
F and, preferably, in the range of 1600.degree. F to 2800.degree.
F. The ceramic fiber strips referred to herein are cut from a
ceramic fiber blanket which is commercially available from several
different manufacturers; these blankets are manufactured under the
trademarks or tradenames "Kaowool" (Babcock & Wilcox),
"Fiber-Frax" (Carborundum Co.), "Lo-Con" (Carborundum Co,), and
"Cero-Felt" (Johns Manville Corp.). Most of these ceramic fiber
blankets have an indicated maximum operating temperature of about
2300.degree. F. The end or edge fiber exposure provided by the
present invention not only provides an improved insulation up to
the maximum indicated operating temperatures suggested by the
manufacturers, but because devitrification and its deleterious
effects are largely eliminated, also permits operation up to about
2800.degree. F.
By arranging the fibers in an end or edgewise exposure; that is,
where the fibers are oriented in planes generally perpendicular to
the wall of the furnace, devitrification is not necessarily avoided
but its undesirable side effects are minimized or eliminated
because devitrification takes place at the ends of the fibers
rather than along the lengths thereof; thus cracking and
delamination are essentially avoided by the present invention even
up to a temperature of 2800.degree. F which is above the
recommended maximum temperature specifications imposed upon the
fiber blankets by the manufacturers.
The present invention also provides an insulation which will
maintain the outside (cold face) of the furnace within an
acceptable range. It is recognized that the minimum external
temperature will be dependent upon a number of different factors
including, but not limited to, the type, thickness and strength of
the outside furnace wall; ambient temperature conditions outside
the furnace wall. The use of the present invention, however, will
provide an outside temperature varying between 200.degree. and
350.degree. F which is considered to be an acceptable range, the
temperature being measured in still air at 83.degree. F.
Another advantage which accrues from the use of the fiber blanket
(or strips thereof) in the end or edge exposure of the fibers is
that the resulting mat has a certain resiliency in a direction
parallel to the insulated face. Thus, where metallic fasteners are
employed to attach the mat or composite block to the interior wall
of the furnace or oven by "burying" or imbedding the fastener in
the insulating member, this natural resiliency of the material will
tend to keep the ends of the fastening elements completely covered
at all times; this is true even if a tool is inserted in or through
the fiber material to engage the metallic fastener for turning or
welding purposes; after the tool has been withdrawn the natural
resiliency of the fibrous material, as presently oriented, will
cause the material to spring back and completely cover the outer
end of the metallic fastening member.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary plan view of an insulating mat made from
strips of a ceramic fiber blanket;
FIG. 2 is a fragmentary side elevation of the ceramic fiber mat
shown in FIG. 1;
FIG. 3 is an end elevation of the ceramic fiber mat shown in FIG.
1;
FIG. 4 is a plan view of another embodiment of a ceramic fiber mat
made in accordance with the present invention;
FIG. 5 is a side elevation of the ceramic fiber mat shown in FIG. 4
with certain internal connecting members shown in dotted lines and
further showing the association of the resulting insulating member
with a furnace wall;
FIG. 6 is an end elevation of the ceramic fiber mat shown in FIG.
5;
FIG. 7 is a view similar to FIG. 6 showing a method of stud welding
of the resulting insulating member to a furnace wall;
FIG. 8 is an enlarged and fragmentary detail view, with certain
parts in cross-section, of the stud, nut and associated structure
involved;
FIG. 9 is a view similar to the lower portion of FIG. 8 showing the
relationship of the various parts following the welding
operation;
FIG. 10 is an enlargement, on a slightly larger scale, of the
retaining ring shown in FIG. 8;
FIG. 11 shows a parquet-type arrangement of insulating members on a
furnace wall;
FIG. 12 shows an enlargement of insulating members on a furnace
wall with spaces between adjacent members being filled with
separate insulating elements;
FIG. 13 shows one embodiment of a separate insulating element to be
inserted between adjacent insulating members;
FIG. 14 is another embodiment of a separate insulating element to
be inserted between adjacent insulating members; and
FIG. 15 is still another embodiment of a separate insulating
element to be inserted between adjacent insulating members.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings in detail, FIG. 1 shows a portion of the
outer surface (hot face) of an insulating mat, generally designated
by the reference character 20, composed of a plurality of strips 22
which are cut transversely from a ceramic fiber blanket (not
shown). As indicated heretofore, these ceramic fiber blankets are
generally provided in widths of several feet, of thicknesses
generally ranging from one-sixteenth of an inch to three inches and
of almost any desired length; the manufacturer generally rolls up
the blankets lengthwise so that, when supplied, these blankets are
in the form of rolls whose diameters are dependent upon the length
of material in the roll. When the strips 22 are cut from the fiber
blanket they are cut in a direction of the thickness perpendicular
to the width and length so that the lowermost strip 22 shown in
FIG. 1 has a dimension T which represents the thickness of the
fiber blanket from which the strips 22 are cut.
The strips 22, after they are cut from the fiber blanket, are
placed on edge adjacent each other until the desired width of mat
is obtained as shown in FIG. 1. Obviously, the number of strips
required will depend upon the thickness T of the fiber blanket from
which the strips are cut. If a fiber blanket could be provided of
thickness twice that of T, then only one half of the number of
strips shown in FIG. 1 would be required. Furthermore, if it were
possible to provide a fiber blanket having a thickness equal to the
width of the resulting block or mat therefor, then only one such
strip would be employed in connection with each insulating
block.
The strips 22 are held together by any convenient means; as best
shown in FIGS. 1 to 3, the strips 22 are held together by means of
a plurality of stainless steel wires 24 which run transverse to the
strips approximately one-half inch from and parallel to the cold
face 26 of the mat. The ends of the wires 24 are bent at right
angles as shown so as to be retained in position. Various methods
and means can be used in conjunction with these wires 24 to attach
the mat 20 to a sheet or block of backing type insulation 28 (see
FIGS. 5 and 6); for example, a plurality of hairpin-type devices 30
can be placed over the wires 24 at various positions along their
length so as to project down below the cold face 26 of the mat 20.
Actually, these pins 30 will be driven into the block of backing
type insulation 28 and, preferably, these hairpin devices 30 will
be of the self-clenching type when they are urged against a hard
surface as will appear hereinafter.
Although the mat shown in FIGS. 1 and 2 (and the resulting
insulation member comprised thereof) is represented as having a
width of approximately one foot and a length of possibly several
feet, the preferred shape is shown in FIGS. 4 to 7. The resulting
insulating member shown in these figures would have a nominal
twelve inch by twelve inch face size and a 2300.degree. F
temperature rating. The actual face size will be
121/4".times.121/4", the additional 1/4" insuring fullness in the
installed insulation while providing a net twelve inch by twelve
inch coverage. Intermediate strips 22' and the outer strips 34
(later to be described) are cut to their respective sizes from one
inch thick ceramic fiber blanket. The block of insulation 28 is
mineral block insulation which, in this case, is cut to a size two
inches thick, ten inches wide and twelve inches long. Since the
outer strips 34 overlie the longitudinal side edges of the block
28, these strips would be two inches longer (in the vertical
direction as they appear in FIG. 7) than the intermediate strips
22'. It might also be mentioned that a hole 36 is drilled in the
center of the block 28 so as to receive a stud (later to be
described).
Parts 34 and 22' are now laid side by side to form the hot face and
are secured together by means of the stainless steel wires 24 which
are bent ninety degrees at the ends to hold them in place. As shown
in FIGS. 4 and 5, two such wires 24 are provided for the insulating
member shown in these figures, although additional number of wires
could be provided if desired.
The next step in the assembly of the insulating member involves the
installation of the stud which will now be described. The stud
comprises a central shank 38 having nut 40 threadedly mounted at
the upper end thereof. A washer 42 is provided on the shank 38
immediately below the nut 40. When installed, the washer 42 will
rest against the upper surface of the block 28. The lower end of
the shank 38 is provided with a stud tip 44 of relatively smaller
cross sectional area. Also mounted on the lower end of the shank 38
are a ring retainer 46 received in the groove 48 and a ring-shaped
ceramic arc shield 50 which is secured to the ring 46 by cement or
in any other suitable manner. The purposes of the foregoing
elements will be described hereinafter in greater detail.
At any event, after the stud (with associated elements attached) is
inserted into the hole 36 in the manner described above, the prior
assembly of parts 22', 34 and 24 are placed over the block 28 with
the lower parts of the side strips 34 overlying the two
longitudinal side edges of the block 28. Four hairpin-type
stainless steel fasteners 30 (two for each wire 24) are now
inserted into the seams between the strips 22' so as to engage the
wires 24. These fasteners 30 are driven through and clenched
against the back surface of the block 28. By providing a hard
surface, preferably steel, below the block 28 when the fasteners 30
are inserted, the lower ends of these fasteners will clench towards
each other as shown in FIG. 5. When the tool (not shown) for
inserting the fasteners 30 is withdrawn from the seams, the strips
22' will return to their original position without leaving any gap
or aperture because of the inherent resiliency of these strips.
The resulting insulation member, now complete, is ready for
installation against a furnace wall 32 by means of a stud welding
process which is more fully described and claimed in the patent
entitled "Method and Apparatus for Stud Welding" referred to above.
The method and apparatus for stud welding (as described in the
aforementioned copending application) forms no part of the present
invention but is described briefly hereinafter merely to show one
manner of attachment of the insulating member 20' to a furnace
wall. A stud welding gun 52 is inserted into the central seam
between the middle strips 22' until the lower end of the gun
engages the nut 40 of the stud. The stud gun is triggered and
current flows into the shank 38 and into the tip 44. The tip 44,
because of its relatively small cross sectional area burns away and
thus starts an arc. The stud shank 38 does not itself move at first
because it is supported by the self-locking ring retainer 46 which
is retained in the groove 48 as indicated heretofore. As best shown
in FIG. 10, the ring retainer 46 is provided with a plurality of
radial fingers 54 which project into the recess 48 to hold the ring
46 in position. As the welding operation continues, the intense
heat of the arc burns away the fingers 54, thus allowing the stud
shank 38 to plunge into the molten metal formed by the arc. At this
point, the weld is completed and the gun can be withdrawn. It
should be mentioned, however, that the ring retainer 46 and the
fingers 54 thereon are carefully sized so that the fingers will
burn away, melt, or soften in approximately two tenths of a second,
or within whatever period of time is deemed appropriate, all as set
forth more fully in the aforementioned copending application.
Now, it may be desirable to tighten the nut 40 on the shank 38.
This can be done by merely rotating the gun about the vertical axis
of the shank. It might be mentioned that the lower end of the gun
(or extension thereof, if desired) is provided with a hexagonal
opening corresponding to the size of the nut 40 and of sufficient
depth to accommodate for the upper end of the shank 38 after the
nut is tightened thereon. Thus the gun 52 serves a secondary
function as a wrench for the nut. When the stud gun is withdrawn,
the resiliency of the ceramic fiber strips will cause the strips to
return to their original position thus concealing and protecting
the studs from the severe heat in the furnace.
Returning now to further consideration of FIGS. 4 and 5, it should
be noted that the end strips 34 of the insulating member 20' are
preferably provided with a plurality of one inch deep cuts 56
spaced approximately one inch apart from each other so as to
relieve possible shrinkage stresses on parts 34 only.
As shown in FIG. 11, it may be desirable to arrange the blocks 20'
of FIGS. 4 through 6 in such a manner that the strips of adjacent
members are at right angles to each other to give a resulting
criss-cross appearance similar to that of parquet flooring. As
indicated heretofore, the arrangement of the fibers is such that
they are oriented essentially in planes which are perpendicular to
the furnace wall. This tends to eliminate or minimize the occurance
of cracks which result from heat shrinkage of ceramic fibers. The
arrangement shown in FIG. 11 tends to minimize or offset lineal
shrinkage of the strips themselves.
The method and apparatus for insulating a furnace wall must be
adaptable to walls which do not correspond, dimensionally, to the
usage of nominal twelve inch by twelve inch insulating members.
Also, it is recognized that the method and apparatus for insulating
a furnace should be adaptable to furnaces which have irregularly
shaped burner blocks and flue openings. As shown in FIG. 12, it is
possible to arrange and attach a plurality of insulating members
20' to the surface 32' of a furnace not readily adaptable for the
close end-to-end, side-to-side, arrangement shown in FIG. 11. In
the case of FIG. 12, spaces 58 are provided between adjacent
insulating members 20' in longitudinal or transverse or both,
directions, depending upon the dimensional limitations of the
furnace. The resulting spaces 58 can now be filled with specially
folded ceramic fiber blankets such as shown in FIGS. 13, 14 and 15.
The three fillers shown in the latter three figures are constructed
in substantially the same way as the strips 22; that is, they are
cut from a one inch thickness of four pound density ceramic fiber
blanket and folded over.
In FIG. 15, there would be a single sheet 60 which is folded once
so that its upper edges 62 provide the same type of end or edge
fiber exposure referred to herein. If the resulting space is larger
than two inches wide, then it is possible to go to the
configuration shown in FIG. 13 which is comprised of two strips 64
and 66, which are cut in the same manner described above. The
central strip 66 is relatively narrow in a vertical direction and
the outer strip 64 is sufficiently wide that it can be folded
around the central strip 66 as shown, the upper surfaces of strips
64 and 66 both providing the end or edge fiber arrangement referred
to above.
Again, if the resulting space between adjacent insulating members
20 are between an insulating member 20 and a duct, etc. is greater
than three inches, then it might be desirable to use the
configuration shown in FIG. 14 where an additional central strip 68
is provided. This strip 68 will lie adjacent the strip 66 and an
outer strip 70, slightly greater in width than the strip 64 will be
folded over the central strips 66 and 68 to provide the arrangement
shown.
The different embodiments shown in FIGS. 13, 14 and 15 can be held
in place by ceramic cement, stainless steel wire or by the friction
between the fibers alone.
FURTHER EMBODIMENTS AND MODIFICATIONS
Whereas the method of assembling the mat as described in relation
to FIGS. 1 to 3 has been set forth in terms of wires 24, fasteners
30, etc. it should be understood that other methods could be
employed to hold the strips together and to attach them to the
backing insulation block. For example, the ceramic fiber strips
could be attached to each other by means of suitable ceramic
cements or mortar materials which are preferably utilized in the
area adjacent the cold face of the fiber mat. Also, although the
mats have been shown as being connected to a backing insulation
block prior to application to a furnace wall, the mats could be
applied directly to the furnace wall.
As far as the manner of fastening is concerned, the foregoing
disclosure indicates that the mat of FIG. 1 or the composite block
of FIG. 4 can be attached to a furnace wall by means of mortar,
ceramic cement or various metallic fasteners. Since the ceramic
cement or mortar will generally be located adjacent the cold face
of the insulating member, there should be no particular high
temperature problem as far as the cement or mortar is concerned;
however, where metallic fasteners are concerned, it is generally
recognized that alloy pins, bolts, washers and screws which could
be used as fasteners have a maximum temperature limit in the range
of 2000.degree. to 2100.degree. F. By "burying" or imbedding the
fastener in the insulating member at a position spaced from the hot
face thereof, as disclosed in the present invention, it is possible
to use alloy pins, bolts, etc. without, at the same time, exposing
these metallic fasteners to such high temperatures as would
interfere with their effectiveness.
Although it is indicated that the mat of FIG. 1 could be applied
directly to a furnace wall by means of ceramic cement or mortar, it
is possible to precondition the cold face of the mat to permit the
use of the stud welding method of attachment disclosed herein. For
example, if a layer of cement or mortar is embedded in the mat
along the cold face thereof and allowed to harden, it is obvious
that the welding technique and fasteners described in connection
with FIGS. 7 to 10 could be employed, although a shorter shank 38
obviously would be necessary. The making of such a cement or mortar
layer at the cold face of the mat could also be done in connection
with the use of a high temperature cloth or stainless steel wire
mesh which would be applied to or imbedded in the mortar layer at
the cold face of the mat to improve the fastening capabilities
thereof.
Referring now to FIGS. 4 through 7, a suitable insulating block 20'
designed for operation at 1800.degree. F is one where the backing
block or mineral block 28 is about two inches in thickness and the
strips 22' are approximately one inch in width giving a total width
of the block, from the cold face to the hot face thereof, of about
three inches. A suitable insulating block 20' designed for
operation at 2600.degree. F is one where the mineral block 28 is
also two inches in thickness but where the strips 22' are four
inches in thickness giving an overall dimension of six inches from
the cold face to the hot face. By using strips 22 varying in width
from one inch to five inches or more, depending upon the
requirements of the particular furnace, it should be apparent that
insulating blocks and/or mats could be employed to cover the
recommended range of 1600.degree. F to 2800.degree. F.
Although the block 28 has been referred to as a mineral block whose
composition and properties are well recognized in the art, it is
also possible to use asbestos block or calcium silicate block,
these blocks being relatively rigid, especially as compared to the
fiber mat or strips, so as to provide relatively rigid backing
material for the mat. The strips 22 or 22' of the ceramic fiber mat
20 or 20', respectively, are preferably cut from a ceramic fiber
blanket having a density of four pounds per cubic foot. It is
understood that the manufacturers provide ceramic fiber blankets
which are available in densities ranging generally from three to
fourteen pounds per cubic foot. In the specific examples referred
to herein, the ceramic fiber material has a density of four pounds
per cubic foot. However, it should be understood that there might
be portions of the furnace where the lining would be subject to gas
currents which would give rise to erosion problems and, also, that
the furnace might have various access openings which would require
a lining of greater physical strength or density upon or
surrounding the openings; in either of the latter two cases it
might be desirable to use a ceramic fiber material of a higher
density in the available range referred to above.
Naturally, it is desirable to insulate a furnace wall in such a
manner that the outside (cold face) of the furnace is at a minimum
temperature. However, it is recognized that this minimum
temperature will be dependent upon a number of different factors
including, but not limited to, the type, thickness and strength of
the outside furnace wall; and prevailing air currents outside of
the furnace wall. The use of the present invention will provide an
outside temperature varying between 200.degree. F and 350.degree. F
which is considered to be an acceptable range.
The preferred embodiment of the present invention, as disclosed
above, describes the high-temperature insulating fibers which
constitute the mat as "ceramic" fibers. However, this invention
should not be tied down to any precise definition of "ceramic"; any
high temperature insulating fiber which possesses properties
similar to the ceramic fibers indicated herein and capable of
operating above 1600.degree. F could be used in conjunction with
the present invention and should be considered as falling within
the scope thereof.
Whereas the present invention has been described in particular
relation to the drawings attached hereto, it should be understood
that other and further modifications apart from those shown or
suggested herein may be made within the spirit and scope of this
invention.
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