Technical Field
[0001] This invention relates to an improved system used to support elements of electric
heating in the form of tapes or wire conductors, applicable to the lining of ceramic
fiber refractories.
Background Art
[0002] The petroleum crisis, from which the energy crisis in general has resulted, has determined
with increasing pressure the development of systems of thermal insulation and of alternative
sources of energy. The substitution of other higher cost sources of energy, for example,
electric for the thermal energy from combustion of petroleum products has also increased
the use of insulation.
[0003] For a case of better insulation, the applicable of ceramic fiber resolved the related
problems with highly satisfactory performance. However, the application of electric
energy in ceramic fiber lined furnaces has created difficulties and practical problems
in the face of technical limitations or the cost of the systems of support of the
elements of electric resistance, which are the "in-situ" generators of thermal energy
required in furnaces and other equipment, and principally in industry.
[0004] The electric resistance supports used normally in this case are usually composed
of several pieces, including refractory or stainless steels, of sophisticated manufacture,
high cost and are not always available. Therefore, to obtain high temperatures "in-loco"
of around 800°C, INOX 310.steel is used, and for 1100°C, INOX 310 or INCONVEL 601
is employed.
[0005] Systems for hanging electrical.heaters using metal hangers all suffer from the problem
that the creep strength of the metal decreases with temperature increase leading to
failure of the system.
[0006] Other methods of supporting hangers.for electrical heaters in systems using ceramic
fiber are shown in U.S. Patent 4,272,638 and U.S. Patent 4,154,975. Both of these
patents disclose complicated and expensive systems.
[0007] There remains a need for a system that is inexpensive, stable at high temperatures
and easy to install in a variety of ceramic fiber wall systems.
Disclosure of the Invention
[0008] Such solution of the above problem consists essentially in providing electrically
inert pieces of certain structure, proper for insertion into insulating linings of
ceramic fiber. Normally such insulating lining is attached to the housing of ; the
equipment or a hard refractory layer is applied intermediately or superficially to
the walls of the housing with ceramic fiber overlaying the hard refractory.
[0009] For such purposes, the invention provides a supporting device and system applicable
for heating elements of a certain form and structure, described later and illustrated
in the attached drawings. Such supporting devices are firmly anchored in the ceramic
fiber blankets covering the housing or in pre-molded modules of ceramic fiber, installed
on the housing in a state of compression which on the average typically makes up 30%
and may use batten strips to adjust for shrinkage between such modules in use.
[0010] The electrical support system of the invention utilizes a series of ceramic hanger
elements having a generally wedge shaped pointed end adapted to be inserted into the
ceramic fiber, a coupling member having a generally flat surface generally perpendicular
to the axis of said wedge and a hook adapted to support an electrical heater element
located at the opposite end of said hanger from said wedge shaped pointed end. The
hanger further comprises a coupling portion joining the hook and wedge shaped portion..
The coupling member is generally planar and adapted to bear against the ceramic fiber
when in use. The wedge shaped portion is composed of at least one planar member generally
perpendicular to the plane of the hook and at least one planar member generally in
the plane of the hook.
[0011] The structure and application of the.sustentation device and inventive electrical
hanger system will be better understood when referred to in the drawings attached.
Brief Description of the Drawings
[0012]
Figure 1 represents a type of support device in longitudinal vertical cut.
Figure 2 represents a type of support in longitudinal horizontal view.
Figure 3 represents a section along B-B of Figure 1.
Figure 4 shows a type of anchorage of the support ; devices of electric resistance
in the forms of a helicoid wire in which modules of ceramic fiber are used and hold
the hanger elements.
Figure 5 shows the same type of anchorage in which the electric resistance is shown
in the form of tape or ribbon.
Figure 6 shows the support device in two methods of suspension of electric resistance.
Figures 7 and 8 represent an alternative design of the support device of the invention.
Best Mode for Carrying Out the Invention
[0013] Illustrated in Figures 1 and 2 is the support device, made by molding and/or sinterization
of an electric insulating ceramic material. The device is here shown in the form of
a molded device, with an end in the form of hook 1 and the opposite end in the form
of a wedge 2.
[0014] As illustrated in Figures 7 and 8, there are alternate embodiments of the hanging
elements of the invention. These elements generally indicated as 20 differ from the
embodiments of Figures 1 and 2 in that they do not have barbs 21, 23 and 25. They
further differ as on the flat surface of 7' there are formed a series of ridges 27
and valleys 29 which act to increase the surface area of the hanger element.
[0015] In a particularly preferred form of installation utilized in the invention, the hanging
elements are coated with a refractory cement prior to insertion into the insulating
ceramic fiber. The ceramic fiber is at least partially slit with a knife prior to
insertion and then the hanging element coated with the refractory cement is inserted
into the cut. The series of ridges and valleys increases the surface area for bonding
of the ceramic cement to the ceramic fibers. It further inhibits withdrawal of the
hanging element.
[0016] The materials forming the hanging elements of the invention-may be any material which
is generally non-conductive and also temperature resistant at the intended'use temperature
of the furnace. Typical of materials suitable for the hanger elements of the invention
are silicon carbide and alumina.
[0017] Alumina while having very desirable temperature proporties is expensive. Preferred
materials for the system of the invention are mullite for applications up to about
2300°F and cordierite for applications up to about 1600°F as these materials are easily
formed, chemically stable and heat shock resistant.
[0018] The refractory cement utilized in mounting the hangers of the invention may be any
material which is operable at -the anticipated temperatures and is suitable for easy
application onto the hanger element. Preferred materials are air drying water base
refractory cements, such as fire clay refractory cements.
[0019] As may be observed in Figures 1, 4, 5 and 6, the hook part is placed externally from
the lining, sometimes in modules of ceramic fiber and in the form of body 3 of a pyramid
trunk or similar shape, of a trapezoidal transversal section, pointed outward and
on whose end is formed a shoulder of rectangular transversal section of a relatively
small height, forming a straight hook 4, leaving a space 5 for placing the electric.
resistance in the form of wire or tape.
[0020] The opposite end 2 has a general shape of a tapered wedge, with point 6 slightly
rounded and with projections 7 and 7', to reinforce its anchorage in the insulation
or in the respective module of ceramic fiber 10. Projection 7 serves to provide structural'support
for the hook 1 and also minimize side movement of the sustentation member. The projections
of 7' serve to supply support or bearing surface to support the hangers and electrical
heating elements without breaking down the fiber.
[0021] The hangers of the invention may be any desired size that will provide sufficient
anchorage in a particular wall to support the electrical device to be used. A'typical
size is about 6-1/2" overall length. The length and thickness will also vary depending
on the ceramic material forming the hanger.
[0022] The coupling piece 9 represented in Figure serves to hold support 1 jointed to wedge
2 which is anchored inside the insulation of ceramic fiber. The coupling piece 9 in
contact with the ceramic fiber stabilizes the hook 1 and helps prevent its sagging
into the fiber so as to hang down and become dislodged.
[0023] As illustrated in Figure 4, the devices of support 1, 2 are anchored in the module
of ceramic fiber 10, with part 2 firmly fitted under compression and fastened inside
insulation 10, with the aid of projections 7, 7' and 31, 33 and 35 serving for sustentation
of the electric resistances in the form of wire 11, as is well shown in Figure 4.
[0024] As illustrated in Figure 4, the supports 1, 2 are found placed in two horizontal
rows, with hooks 4 of the upper row turned upward and those of the lower row turned
downward, so as to hold wire 11, and to prevent it from slipping. To make holding
better for wire 11, held in sine wave or in zig-zag alternately around the upper and
the lower supports, the supports of the lower row are found separated from those of
the upper row to the right, as seen in Figure 4 by the observer.
[0025] Figure 5 is an illustration similar to Figure 4 except that the electric resistance
37 is shown as a ribbon or tape, adapted to space 5 of support 1. In this case it
is anchored in the ceramic fiber module 10, also two rows of supports 1 and 2, and
in both their hooks are turned outward. As may be seen, in relation to the upper row,
the electric resistance 37 in a spiral or helicoid form, rests on the | respective
spaces 5. The tape 37 may be fastened to the supports, for example, by a wire of the
resistance itself, or another adequate one in case this becomes necessary.
[0026] In Figure 6 in the lower row, the case of application of spiralled or helicoid resistances
of a larger gauge 39 is illustrated. The element 4l is a heater of smaller gauge that
may be placed on hook 5. In this case supports of larger dimensions are avoided, with
more difficult anchorage in the mass of ceramic fiber, by pieces in the form of a
joint double-L forming a type of hanger 12. The upper branch of the junction of pieces
in L is simply placed in the space 5 of support 1 and the lower branches of the L
will hold the larger size resistance. To provide for possible differences in the gauges
of the electric resistances for each specific case, these parts 12 can be prepared
in the form of an L, with dimensions of the lower branch, each of which adapted to
each case. Parts 12 can be prepared of any thermal resistant material, which does
not need to be properly insulated electrically because of the refractory nature and
the insulation of supports 1 and 2.
[0027] The heating elements of Joule effect of electric resistance are supported on supports
1 and may be fastened to this by a wire of the same material or may be suspended.
The fastening of the elements is of interest especially for these heating elements
comprising spiral wires on a ceramic core.
[0028] The type of fastening of the invention eliminates any ; necessity of using refractory
or stainless steels, and I generally substitutes a large variety of parts with one
piece only with large economy of material and labor. As may be easily deduced from
the illustration of Figures 4, 5 and 6, the electric resistance system is very easily
assembled, and may be completed in a short period of time even by non- specialized
personnel, and therefore at a greatly reduced cost.
[0029] Although described with reference to certain preferred embodiments, it would be clear
to people skilled in the art that there are other variations in the hanger device
and system of the invention which are obvious and are intended to be included by the
present specification and claims. Further the hanger device could be formed with a.somewhat
differently shaped wedge-shaped surface or with more than one planar member parallel
to the plane of the hook. While the hangers and mounting system of the invention have
been illustrated as installed in a ceramic fiber module, it is also within the invention
to install the system in ceramic fiber wall systems of other construction or to insert
the devices into the folded fiber blanket which may be inserted between the modules.
1. A support or sustentation method for elements of electric heating in furnaces and
in equipment insulated with ceramic fiber comprising a structural material resistant
to electricity in the form of pieces of complex construction, comprising a part at
the free ends in the form of hooks, parts at the opposite end in the form of wedges
anchored in the insulating lining or module of ceramic fiber with the aid of coupling
pieces joining said hooks and wedges wherein the hooks of said pieces cooperate to
hold the heating elements of the electric resistance heaters.
2. A support or sustentation method in accordance with claim 1, wherein the parts
in the form of hooks have a body of a general form of a trunk or pyramid or similar
of a transversal trapezoidal section where a wire or tape of electrical resistance
is placed.
3. A support or sustentation method, in accordance with claim 2, wherein the parts
in the form of wedges have a tapered point with projecting shoulders of the wedge,
respectively, upward and toward the sides to reinforce the anchorage of the device
in the insulation.
4. A support or sustentation method, in accordance with claim 3, characterized by
its alternate arrangement in horizontal rows, with coupling and anchorage in the insulation,
with hooks in position of the upper row, turned upward and those of the lower row
turned downward, to assure a firm positioning of the elements of the electric resistance
in the form of wires or tapes in a sine wave development.
5. A support or sustentation method, in accordance with claim 3, further comprising
arrangement in horizontal rows for direct reception of the heating elements in the
form of tapes or spiralled or helicoidal wires in the respective spaces of the hooks
turned upward in alignment, with eventual fastening with the same material as these
elements.
6. A support or sustentation method, in accordance with claim 5, characterized by
the fact that, for applying spiralled wires of a larger diameter, complementary pieces
are placed in the respective hooks in the form of adouble-L hanger, joined in the
upper part by a horizontal transversal branch supported in the open space and where
the lower free branches have a width corresponding to the mentioned wire..
7. A high temperature hanger for use in ceramic fiber furnace walls comprising a wedge
shaped pointed end adapted to be inserted into the ceramic fiber, and a hook located
at the opposite end of said hanger from said wedge shaped pointed end.
8. The hanger of claim 7 wherein said wedge shaped end comprises at least one generally
planar member generally transverse of the plane of said hook.
9. The hanger of claim 8 wherein said wedge shaped end further comprises at least
one planar support element generally in the plane of the hook.
10. The hanger of claim 9 wherein said hook is planar.
11. The hanger of claim 7 wherein a coupling member having a generally flat surface
joins said wedge shaped pointed end and said hook and said flat surface is adapted
to bear against said ceramic fiber during use.
12. The hanger of claim 8 wherein said wedge shaped end comprises a series of ridges
and valleys on its surface.
13. The hanger of claim 8 wherein said wedge shaped end comprises barbs.
14. The hanger of claim 7 wherein it has an overall length of about 6.5".
15. A method of sustentation of electrical heating elements comprising inserting a
plurality of hangers into the ceramic fiber lining of a furnace, said hangers comprise
a wedge shaped pointed end adapted to be inserted into the ceramic fiber and a hook
located at the opposite end of said hanger from the pointed end and suspending electrical
heating elements from said hooks.
16. The method of claim 15 wherein said hangers are in a plurality of rows with said
hangers of each row offset vertically from said hangers in rows parallel to it.
17. The method claim 16 wherein electrical ribbon heaters are suspended from said
hooks.