US3168297A - Furnace pipe insulation and method - Google Patents

Description

Feb. 2, 1965 J. R. BROUGH FURNACE PIPE INSULATION AND METHOD 3 Sheets-Sheet 1 Filed May 2, 1962 0 R wv/w mm mm m 7 h T m Feb. 2, 1965 J. R. BROUGH FURNACE PIPE INSULATION AND METHOD 3 Sheets-Sheet 2 Filed May 2, 1962 INVENTOR.

Afzamzys.

Feb. 2, 1965 J. R. BROUGH FURNACE PIPE INSULATION AND METHOD 5 Sheets-Sheet 3 Filed May 2, 1962 United States Patent 3,168,297 FURNACE PEPE ENSULATION AND METHQD John R. Brought, Gary, Ind, assignor to Inland Steel (Iompany, Chicago, llL, a corporation of Delaware Filed May 2, 1962, Ser. No. 193,575 22 Claims. (Cl. 263-6) This invention relates in general to furnaces and more particularly to an insulated pipe construction for use in high temperature furnaces. It deals specific-ally with an improved insulation construction and method of insulating water cooled furnace pipes.

This application is a continuation-in-part application of the copending application entitled Insulation, filed June 3, 1961, bearing Serial'No. 121,427, now abandoned.

It is a conventional practice in the iron and steel industry to provide reheating furnaces for bringing billets of steel up to required temperature in preparation for rolling operations. One well known type of furnace utilized is described as an underfired furnace. In the operation of such a furnace, fuel is burned in the lower regions of the furnace while billets of steel pass over the burning fuel and are. heated thereby to a predetermined temperature. The fuel might be natural gas, coke oven gas, or oil, or the like. it is not unusual for temperatures in the neighborhood of 2400 F. to be generated in such a furnace when a finished billet temperature of in the neighborhood of 2100" F. is sought for a rolling operation, for example.

In passing through a furnace while undergoing reheating to a predetermined temperature, the billets are conventionally supported on longitudinally extending skid means or tracks upon which the transversely extending billets slide. With billets of relatively small size, these tracks or skid means might be solid rails but for heavier billets and, for that matter, for all high temperature end discharge furnaces, water cooled skid means in the form of skid pipes are standard equipment.

These water cooled skid pipes normally have a wear strip welded on their upper surface and extending longitudinally of the pipes to support the billets in sliding relationship. In the underfired' reheating furnace, for example, the longitudinally extending horizontal skid pipes are carried by transversely extending horizontal crossover pipes which in turn are supported by vertically extending support pipes. Water preferably courses through all the pipes in a well known manner to provide cooling thereof.

In recent years the use of insulation on such Water cooled pipes has become popular because of the considerable water heat losses suffered when non-ii isulated water cooled pipes are utilized. With non-insulated water cooled, skid pipesin use. in an underfired furnace, for example, it would not be unusual for up to 25% of the input of natural gas, for example, to be. lost in heating the water rather than the steel billets. This, in turn, effects the furnace capacity, in many cases, since a furnace normally has a limited fan, stack, or burner capacity and only so much fuel can be pumped through it. in addition, where the ski pipes are not insulated, uneven heating of the billets frequently results and in some cases it is serious enough to prevent rolling thereof.

A number. of means for insulating Water cooled high temperature furnace pipes have been utilized in the past. For example, the Schmidt United States Patent No. 2,482,878, entitled Reinforced Refractory Pipe Insulation, discloses an insulation construction of the general type now in use in the iron and steel industry. Each of the insulation arrangements heretofore utilized has serious drawbacks, however. In the insulation construction disclosed in the Bloom United States Patent No. 2,693,352,

there is a tendency for the refractory material to flakeaway from the reinforcing reticulated metal structure exposing it to the heat of the furnace which not only considerably reduces the effectiveness of the insulation but materially shortens its life. refractory is caused by a marked temperature. diiference between the refractory material within or around the reinforcing metal structure and the overlying refractory material. a

It is an object of this invention to provide a new andimproved insulation construction.

it is another object to provide a-neW and improved insulation construction forwater-cooled high temperature furnace pipes.

It is still another object toprovide a new and improved insulation construction for'water cooled skid pipes, crossover pipes, and vertical support pipes inan underfired steel mill reheating furnace.

It is a further object to provide an insulation construc tion for water cooled high temperature furnace pipes which is highly durable.

It is yet a further object to provide an insulation construction for water cooled hightemperature furnace pipes which is substantially easier to apply and less expensive than insulations heretofore utilized.

It is still another object to provide a reinforced insulation construction for water cooled high temperature furnace pipes which requires a minimum of high cost, heat resisting, reinforcing material.

It is another object to provide an insulation constructi-on wherein the reinforced means incorporated therein does not set up lines or planes of weakness. in the insulas tion.

It is still another object to-provide an improved in-. sulated furnace pipe.

It is another object to provide a new andimproved method for insulatingfurnace pipes.

It is a further object to provide a method for insulating water cooled high temperature furnace pipes which. is simpler and less expensive and produces. results superior to those methods heretofore utilized.

It is a further object to provide a method for applying insulation to watercooled high temperature-furnace pipes which incorporates means for facilitating relatively in, creased support for the refractory insulation. utilized, while it remains in its plastic state.

The above and other objects are realized inaccordance with the present invention by providing a new and'im, proved insulation construction for Water cooled; high tem perature furnace pipes and? a method: for applying this insulation. Briefly, the invention contemplates encircling a conventional steel furnace pipe havinga water carrying capacity with coils of wire: and securing the coils .tothe pipe with tie-wires threaded through the coils- The coils are defined by wires, in. themselves. coiling'about axes encircling the pipe. Refractory material in a plastic state is applied to the pipe so that it. is in. intimate contact with the coils. 'andthe outer surface of the pipe.

One, aspect of the present invention lies in the utiliza tion of alternating orotherwise successively arrangedindividual' encircling coils of high temperature heat resisting alloy wire and ordinarycarbon steel wire. In such case, the coils are secured to the pipe by tie wiresof corresponding composition threaded through the coils.- Since these alternating or otherwise successively arranged coils of carbon steel Wire and high-temperature heat resistant alloy wire are spaced in, relatively close proximity of one another the refractory material is supported while in its plastic state without the use of a form. After the refractory is hardened by firing, however, substantially less support isneeded to. retain it on the pipe. and, there- T'hi-s flaking off of the fore, the coils of high temperature heat resistant alloy wire are sufiicient alone to effectively support the refractory wire; The ordinary carbon steel wire, due to its inherent physical characteristics and the high furnace temperatures, tends to lose its strength. By utilizing this arrangement of high temperature heat resisting alloy wire coils and carbon steel Wire coils, the number of alloy wire coils required is substantially reduced without seriously diminishing the life or effectiveness of the finished insulation.

Another aspect of the present invention lies in the utilization of a substantially continuous coil of high temperature heat resisting alloy wire Wound spirally of the furnace pipe in parallel realtionship with a substantially continuous spirally wound coil or coils of ordinary carbon steel wire. In such case, of course, tie wires of corresponding composition are threaded through the spirally Wound coils and the coils might be alternated, or otherwise successively arranged in a generally similar fashion.

Another aspect of the present invention lies in the utilization of relative larger 7 diameter ordinary carbon steel wirecoils and relatively lesser diameter high temperature heat resistant alloy Wire coils. This arrangement of the wire coils is such that anirregular stress pattern is set up in the hardened refractory insulation to virtually eliminate serious lines or plane of weakness in the insulation.

The invention, both as to its organization and method of operation, taken with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings, in which: 7

FIGURE 1 is a perspective view of conventionally arranged water cooled furnace pipes in an underfired steel mill reheating furnace;

FIGURE 2 is a front elevational View of a portion of support pipe or a cross-over pipe showing one form'of an arrangement of reinforcing wire coils prior to the application of refractory material;

FIGURE 3 is a rear elevational view of the arrangement shown in FIGURE 2;

FIGURE 4 is a view similar to FIGURE 3 showing the refractory insulating material applied to a portion of the pipe;

' FIGURE 5 is a top plan view of the reinforcing wire coil arrangement for a skid pipe, prior to the application of refractory material;

FIGURE 6 is a front elevational view of the pipe shown in FIGURE 5; x

FIGURE 7 is a'view similar to FIGURE 5 showing the refractory material applied to a portion of the pipe;

FIGURE 8 is a front elevational view of a portion of a support pipe or a cross-over pipe showing another form of an arrangement of reinforcing wire coils prior to the application of refractory material;

furnace, for example, is shown generally at 10. The description of the use of an insulation construction and the method of constructing it, embodying the features of this invention, as applied to furnace pipes utilized in an underfired furnace, is exemplary only, as will readily be understood and this construction might be utilized in various types of furnaces in the steel industry or otherwise. Of primary significance is the fact that furnaces of this type necessarily generate substantially high temperatures in operation; for example in the neighborhood of 2400 F. V

The section 10 shown actually forms one set of skid to the pipe 17.

means or tracks extending longitudinally through a furnace (not shown) along one side thereof while a similar set or sets of tracks embodying substantially identical sectional constructions might extend longitudinally of the furnace along its opposite side and center, for example. In this way, transversely extending billets of substantial length are supported on each end and in the center by skid means as they slide through the furnace while being brought up to heat.

Each section 10 of the skid means preferably includes vertically extending insulated support pipes 11 carrying horizontally and transversely extending insulated crossover pipes 12. The vertical support pipes 11 and the cross-over pipes 12 perform no other function than to support insulated longitudinally extending horizontal skid pipes 14.

Each of the insulated furnace pipes 11, 12, and 14, includes a conventional steel pipe 17 which might be comprised of one-half inch plate. The bare pipes might be anywhere from two to eight inches in diameter. These dimensions, of course, are merely exemplary and it will be understood that they could vary substantially within limits. The steel pipes 17 which form the backbone of the skid pipes 14 have wear strips 18 secured to their upper surfaces by welding, for example. The longitudinally extending skid pipes 14 might be positioned on the transversely extending cross-over pipes 14 by U-shaped brackets 19'of any well known construction welded to the upper surface of the steel pipes 17 in the insulated crossover pipes 12.

With regard to their insulation constructions, the ver tically extending support pipes 11 and the horizontal transversely extending cross-over pipes 12 are ordinarily substantially identical to each other. Consequently, only the cross-over pipes 12 will be described in detail since the makeup of the insulation construction associated therewith is common to each.

Referring now to FIGURES 2 through 4, where the construction of one form of an insulated cross-over pipe 12 is shown in detail, and particularly to FIGURE 2, the pipe 17 is shown to have a plurality of wire coils 21 encircling pipe 17 at generally regularly spaced intervals therealong. These coils include a plurality of ordinary carbon steel wire coils 22 and another plurality of high temperature heat resisting alloy Wire coils 23. The high temperature heat resisting alloy is preferably stainless steel although it is conceivable that other alloys might be utilized. Consequently, the succeeding description of this invention will frequently refer to stainless steel wire coils, though the coils could be formed of other metals.

It will be understood, of course, that stainless steel wire or wire of a generally analogous composition retains its optimum physical characteristics at substantially higher temperatures than ordinary carbon steel wire. Consequently, of course, the strength of the alloy steel wire coils is retained at temperatures high enough to cause ordinary carbon steel wire coils to deteriorate substantially in tensile strength, for example, and in other physical characteristics.

It will be seen that for every stainless steel wire coil 23 encircling the pipe 17 there are bracketing pairs of ordinary carbon steel wire coils 22. The significance of this relationship will be hereinafter discussed in detail. Threaded through each carbon steel coil 22 is a carbon steel tie wire 27 which has its opposite ends tied together, as at 28, to tightly secure corresponding individual coils 22 In turn, each stainless steel coil 23 has a corresponding stainless steel tie wire 29 threaded therethrough and tied at its ends, as at 30, for example.

33 alternating coils of stainless steel wire and carbon steel wire frequently are desirable in crosss-over and support 1pes.

p It will also be seen that the stainless steel coils 23 have a substantially smaller diameter than do the carbon steel coils 22. This relationship is significant in certain ap* plications. and will also be discussed hereinafter in detail. A view of the pipe 17 with its generally regularly spaced coils securely tied thereon is shown in FIGURE 3. The pipe appears as such immediately precedent to applying refractory cement thereto.

Referring now to FIGURE 4, it will be seen that a layer 35 of refractory cement has been partially applied to the pipe 17. When applied, this refractory material is in a plasticized state. It might be any well known type of high temperature refractory material, such as Chromite, for example, as has been pointed out.

The refractory material is packed in and around the wire coils 22 and 23 in its plastic state by hand or by any other well known method. It virtually encompasses and surrounds the generally toroidal coils and comes into intimate contact with both the wires and the surface of the pipe 17. After a pipe is completely covered with the plasticized refractory material layer 35 in this manner the refractory is permitted to harden.

It is during the period when the refractory material is in its plastic state that the ordinary carbon steel coils 22 are especially significant. This is true throughout the period during which the refractory cement is hardening. The ordinary carbon steel wire coils 22 have substantially large diameters and extend from the surface of the pipe 17 virtually to the surface of the refractory cement layer 35. In this manner, they provide completed reinforcement throughout the extent of the hardening layer 35 of refractory cement.

On the other hand, the coils of stainless steel wire 23 might be substantially smaller in diameter in which case their outermost extremities are relatively further from the surface of the layer 35 of refractory cement. Although they provide a substantial amount of reinforcement to the refractory cement in its plastic state, their primary purpose is to provide life long reinforcement of the hardened refractory material when the pipe is in operation in a high temperature furnace, for example.

In operative relationship, under temperatures in the neighborhood and exceeding even 2400" F., for example, the; refractory material is amply supported and reinforced by the stainless steel wire coils 23. When the outermost extremities of the coils 23 are somewhat removed from the surface of the refractory layer 35, the coils are substantially protected from damagingly extreme temperatures and consequently are additionally long lived and durable reinforcements for the refractory, although the coils might, in some applications, extend substantially to the surface of the refractory layer 35. On the other hand, the ordinary carbon steel wire coils, their primary purpose having been served in supporting the refractory cement in its plastic state, are more susceptible to high temperature deterioration.

The difference in diameter between the coils of stainless steel wire and ordinary carbon steel wire has other ramifications also. Since a somewhat undulated surface is defined by the outermost extremities of the coils along the length of the pipe 17, no significant lines or planes of weakness are set up in the hardened refractory and the danger of cracking and consequently serious deterioration of the insulation is considerably lessened.

The combination wherein stainless steel coils 23 are utilized for one-half or less than one-half of the total number of coils required, and the lesser diameters of the stainless steel coils, makes the resultant insulation construction, and process for applying it, substantially less expensive than generally similar insulations and methods heretofore utilized. In known constructions, for example, it has been common practice to use unitary reinforcing means which are composed primarily of high temperatureheat resisting alloys, due to their unitary nature, in order to insure the requisite high temperature reinforcing characteristics necessary to sustain reasonably long service life of the insulated pipes. The concept embodied in this invention provides optimium reinforcement of the refractory material in its plastic state immediately after application, during the hardening stages of the refractory cement, and after the insulated pipe is in service.

A considerably lesser amount of stainless steel is utilized than would, be required if all the coils were made of such material and in addition each of the stainless steel coils is of a lesser diameter thana corresponding ordinary carbon steel coil and consequently contains less wire. It will readily be seen that substantial savings in the expense of insulated furnace pipes of this nature are realized. Nevertheless, due to the specific utilization of the coils in this construction, an insulationis providewhich is'superior to similar known insulations.

Another form of the insulation construction embodying features of the present invention, which might be utilized in the support pipes and cross-over pipes, for example, is illustrated in FIGURES 8 and 9. Again, only a crossover pipe 12 is described in detail, since the makeup of the insulation construction inherent therein would be common to both the support pipes 11 and the cross-over pipes 12.

Turning now to FIGURES 8 and 9, the other form of insulation construction for cross-over pipes 12, referred to above, is shown in detail. Where applicable, components corresponding to components shown and described in relation to the insulation construction illustrated in FIGURES 2 through 4 will be identified by identical reference numerals plus 100. For example, referring particularly to FIGURE 8, the pipe 117 is shown to have a plurality of coils 121 encircling it at generally regularly spaced intervals therealong. These coils include an ordinary carbon steel wire coil 122 and another coil 123 of high temperature heat resisting alloy wire. The high temperature heat resisting alloy wire is preferably stainless steel although it is conceivable that other alloys might be utilized, as has been pointed out.

It will be seen that the stainless steel coil 123 encircles the pipe 117 in a spiral arrangement longitudinally of the pipe. Correspondingly, the ordinary carbon steel coil 122 encircles the pipe 117 in a spiral arrangement such that around any selected circumference of the pipe or along any longitudinal line on its surface the coils 122 and 123 establish an alternating sequence. Threaded through each carbon steel coil 122 is a'carbon steel tie'wire 127 which has its opposite ends tied to studs 131 to tightly secure the coil 122 to the pipe 117 (only one end of the coil 122 and one stud 131 is shown, of course). In turn, each stainless steel coil 123 has a corresponding stainless steel tie wire 129 threaded therethrough and tied at its opposite ends to studs 132 (only one of which is shown) welded to the surface of the pipe 117.

As pointed out, the coils 121 are arranged on the pipe 117 such that a substantially continuous stainless steel wire coil 123 is spirally wound in parallel relationship with a carbon steel wire coil 122. This creates an alternating sequence around any chosen circumference of the pipe. The sequence, however, is merely exemplary of the arrangements which might be used. In practice, for example, a single stainless steel coil 123 might be spirally wound with two or more carbon steel coils 122.,

As is the case with the insulation construction illus trated in FIGURES 2 through 4, it will be seen that the stainless steel coil 123 might have a substantially smaller diameter than does the carbon steel coil 122. This relationship is-significant for the reasons hereinbcfore dis cussed in relation to the insulation construction shown in FIGURES 2 through 4.

As seen in FIGURE 9, a layer 135 of refractory cement is applied to the pipe 117. When applied, the refractory material is in aplasticized state and might be any well known type of high temperature material such as Chromite, for example, as has also been pointed out.

In addition to the advantages inherent in the insulation construction illustrated in FIGURES 2 through 4, the construction described immediately above and illustrated in FIGURES 8 and 9 has certain added advantages. For example, only a single operation is required in encircling the pipe with each coil of wire, since the wire coils are preferably continuous. Consequently, labor costs are substantially low and installation time relatively short.

Another form of the insulation construction embodying the features of the present invention is illustrated in FIGURE 10. Again, only a cross-over pipe 12 is described in detail, since the makeup of the insulation construction inherent therein will be common both to the support pipes 11 and the cross-over pipes 12. Furthermore, of course, it will be understood that the significant aspects of thepresent invention are readily adaptable to use with skid pipes.

Returning now to FIGURE 10, once more, where applicable, components corresponding to components shown and described in relation to the insulation construction illustrated in FIGURES 8 and 9 will be identified by identical reference numerals plus 100. For example, referring particularly to FIGURE 10, the pipe 217 is shown to have a plurality of coils 221 encircling it at generally regularly spaced intervals therealong. These coils include an ordinary carbon steel wire coil 222 and another coil 223 of high temperature heat resisting alloy wire which is preferably stainless steel although it is conceivable that other alloys might be utilized, as has been pointed out.

It will be seen that the stainless steel coil 223 encircles the pipe 217 in a spiral arrangement longitudinally of the pipe. correspondingly, the ordinary carbon steel coil 222 encircles the pipe 217 in a spiral arrangement such that around any selected circumference of the pipe or along any longitudinal line on its surface the coils 222 and 223 establish an alternating sequence. Threaded through each carbon steel 'coil 222 is a carbon steel tie wire 227 which has its opposite ends tied to studs (not shown) to tightly secure the coil 222 to the pipe 217. In turn, each stainless steel coil 223 has a corresponding stainless steel tie wire 229 threaded therethrough and tied at its opposite ends to studs (not shown) welded to the surface of the pipe 217.

As pointed out, the coils 221 are arranged on the pipes 217 such that a substantially continuous stainless steel wire coil 223 is spirally wound in parallel relationship with a carbon steel wire coil 222. This creates an alternating sequence around any chosen circumference of the pipe or along any longitudinal line on its surface. The sequence, however, is merely exemplary of the arrangements which might be used. In practice, for example, a single stainless steel wire coil 223 might be spirally wound with two or more carbon steel Wire coils 222.

In the insulation arrangement shown in FIGURE 10, however, it will be seen that the stainless steel coils 223 are substantially of the same diameter as the carbon steel coils 222.v The outermost extremities of both coils, then, extend substantially to the surface of the refractory 235. Unlike methods of insulation using a metal reinforcement such as a reticulated wire structure where it has been considered necessary to cover the entire structure with a substantial thickness of refractory material 'in order to protect the metal structure from the furnace heat which would seriously Weaken or destroy the structure, the present inventions utilization of wire coils with tie wires threaded through them obviates this necessity g the utilization of separate wire coils in the manner of the construction shown in FIGURES 1 through 7, for example, as it does to a spiral construction.

Departing the construction of the various forms of vertical support pipes 11 and cross-over pipes 12, and referring now to FIGURES 5 through 7, the insulation construction and method of insulating skid pipes 14 is shown in detail. In essence, since a wear strip 18 is welded to the upper surface of the steel pipe 17 forming the backbone of skid pipe 14, to provide a sliding surface for the billets of steel being supported by the skid pipes, the coils of stainless steel wire are anchored to the pipe on opposite sides of the wear strip 18 while the ordinary carbon steel coils are tied in the manner hereinbefore 0 described in encircling relationship of both the pipe and the wear strip.

Referring specifically to FIGURE 5, it will be seen that studs 40 having collars 41 thereon are welded to the surface of the steel pipe 17 at generally regularly spaced intervals in longitudinal alignment along opposite sides of the wear strip 18. The studs 40 provide means for anchoring the opposite ends of the stainless steel tie wires 29 extending through the coils 23 of stainless steel wire. The tie wires 29 might be secured to the studs by being wrapped therearound and reversed to be wrapped around themselves, as seen in FIGURE 6. The use of studs is merely exemplary, however, and other means of anchoring the ends of the stainless steel wire might be utilized.

On the other hand, the coils 22 of ordinary carbon steel wire are secured to the pipe 17 without the benefit of anchoring studs. The tie wires 27 are threaded through corresponding coils 22 of carbon steel wire and tied over the wear strip 18, as at 45. The free ends 46 of the tie wires 27 securing the carbon steel coils 22 to the pipe 17 might be tied, as at 50, to one or more of the adjoining studs 40.

As seen in FIGURE 7, the layer 35 of refractory cement in its plastic state is applied to the surface of the pipe 17 such that it encompasses and surrounds the wire coils 22 and 23 and the studs 40. In this relationship it is in intimate contact with the surface of the pipe 7 -17, each of the wire coils'22 and 23 and the tie wires 27 and 29, and hardens in this relationship. During the hardening process, the refractory material is supported to a great extent by the larger diameter carbon steel coils 22. Considerable support is also offered, as will easily be understood, by the alloy steel coils 23 which are of somewhat smaller diameter and consequently do not extend as close to the surface of the layer 35 of refractory cement as do the carbon steel coils 22.

After the refractory cement is hardened, the tie wires 27 for the ordinary carbon steel coils 22 might be snipped on opposite sides of the wear strip 18, as at 51, where they protrude from the refractory material, and the pipe is ready for service. In practice, however, the protruding wires are ordinarily left intact for the heat of the furnace to soften and oxidize wherein they are sheared or broken by steel being pushed onto the skids. At intervals along the length of the skid pipes 14, the steel pipe 17 forming the backbone of the skid pipes might be left bare of insulation to afford a spot for con-tact by the brackets 19 in supporting relationship. However, this feature forms no part of the invention and it is not thought necessary that it be shown in detail.

Of course, the primary advantages inherent in the insulation construction of the skid pipes 14 are similar to those inherent in the insulation construction of the various forms of cross-over pipes 12 hereinbefore described. For example, since the coils are of somewhat varying diameter, no planes or lines of weakness are es 'tablished in the hardened insulation and consequently the durability and life of the insulation is greatly improved.

In the insulation construction utilized for both the cross-over and support pipes and the skid pipes, there are substantial advantages not found in the insulation constructions or methods for insulating high temperature water cooled furnace pipes utilized ,in the industry today. As has been pointed out, a substantial saving in cost is realized by virtue of the fact that the amount of high temperature heat resisting alloy wire required to secure durable insulation is considerably less than in known similar arrangements.

The specific arrangement of the alternating or otherwise interspersed coils of varying diameter carbon steel and stainless steel wire is such that the stainless steel coils can be better protected from the maximum temperatures generated in the furnace. In such case, as has been pointed out, the outermost extremities of the alternating coils define a somewhat undulating surface which does not set up lines or planes of weakness in the hardened refractory. The insulation construction which results is less expensive, more durable,- and easier to construct than similar known arrangements.

Moreover, when an insulation construction embodies only certain aspects of the present invention, as illustrated in FIGURE 10, for example, satisfactory anchorage is also provided for the refractory material; The tie wires hold the coils or remaining portions of the coils even if they are partially burned and merely become hooks embedded in the refractory. A- mere burning away of a portion of, the coil does not substantially lessen the strength of the reinforcement because the tie Wire retains the remaining portions of the coil which is embedded in the refractory and keeps it from falling off the pipe even if the refractory develops cracks. This is a great advantage of using the present coil and tie wire construction over certain forms of reticulated metal structure which are more or less dependent upon retaining continuity of the entire structure in order to retain their strength.

Although the coils 22, 23, etc., have been described herein solely as encircling the pipes 17, etc., it should be understood that they extend cireumferentially of their respective pipes in doing so. This is true in each embodi ment of the invention described.

While several embodiments described herein are at present considered to be preferred, it is understood that various modifications and improvements may be made therein, and it is intended to cover in the appended claims all such modifications and improvements as fall within the true spirit and scope of the invention.

What is desired to be claimed and secured by Letters Patent of the United States is:

l. A reinforced insulating covering for a furnace pipe comprising insulation means, said insulation means in cluding coil means fabricated of substantially high temperature heat resisting wire adapted to extend circumferentially of the pipe, said coil means including a series of circumferentially extending coil portions separated from each other along any longitudinal line through said insulation means, the wire of each of said coil portions in itself coiling about an axis adapted to encircle the pipe, means adapted to secure said coil means to the pipe, said insulation means further including a layer of refractory material encompassing and intimately contacting the wire of said coil means and adapted to intimately contact and surround the pipe.

2. An insulated pipe construction comprising a pipe, coil means extending circumferentially of said pipe and fabricated of substantially high temperature heat resisting wire, said coil means including a series of circumferentially extending coil portions separated from each other along any longitudinal line on said pipe, the wire of each of said coil portions in itself coiling about an axis encircling said pipe, means securing said coil means to said pipe, and a layer of refractory material surrounding said pipe and intimately contacting said pipe and the wire of said coil means.

3. The insulation of claim 1 further characterized in that said coil means of substantially high temperature heat resisting wire comprises a substantially continuous coil of wire extending ingenerally spiral relationship longitudinally in said insulation.

4. A reinforced insulationfor afurnace pipe comprising a coil of substantially high temperature heat resisting wire adapted to extend circumferentially of the pipe, means adapted to secure said substantially. high temperature heat resisting wire coil to the pipe, a coil of relatively lower temperature heat resisting wire spaced-from said substantially high temperature heat resisting wire coil and adapted to extend circumferentially of the pipe, means adapted to secure said relatively low temperature heat resisting wire coil to the pipe, and a layer of refractory material-intimately contacting andsurrounding the wire of said coils and adapted to intimately contact and surround the pipe.

5. The insulation of claim 4- further characterized in that said coils extend substantially. parallel to each other in generally spiral relationship longitudinally in said insulation. i

6. The insulation of claim 4 further characterized in that eachof said securing means includes tie wire means extending through said coils.

7. The insulation of claim 5 further characterized in that each of said securing means includes tie wire means extending through said coils.

8. The insulation of claim 4' further characterized in that said coil of substantially high temperature heat resisting wire is of a smaller diameter than said coil of relatively low temperature heat resisting wire.

9. The insulation of claim 5 further characterized in that said coilof substantially high temperature heat resisting wire is of a smaller diameter than said coil of relatively low temperature heat resisting wire.

10. An insulated pipe construction comprising a pipe, a coil of substantially high temperature heat resisting wire extending circumferentiaily of said pipe, means securing said substantially high temperature heat resisting Wire coil to said pipe, a coil of relatively. low temperature heat resisting Wire spaced from said substantially high temperature heat resisting Wire coil and extending, circumferentially of said pipe, means securing said relatively low temperature heat resisting wire coil to said pipe, and a layer of refractory material surrounding said pipe and intimately contacting said pipe and the wire of said coils.

11. The insulated pipe construction of claim 10 further characterized in that said coils of wire extend substantially parallel to each other in generally spiral relationship longitudinally of said pipe.

12. An insulated pipe construction comprising a pipe, a plurality of coils of substantially high temperature heat resisting wire extending circumferentially of said pipe, a substantially high temperature heat resisting tie wire extending through each of said coils, means anchoring the opposite ends of said substantially high temperature heat resisting tie wires to secure said substantially high tem perature heat resisting wire coils to said pipe, a plurality of relatively low temperature heat resisting wire coils interspersed and spaced from said substantially high temperature heat resisting wire coils and extending circumferentially of said pipe, a relatively low temperature heat resisting tie wire extending through each of said relatively low temperature heat resisting wire coils, means anchoring the opposite ends of said relatively low temperature heat resisting tie wires to secure said relatively low temperature heat resisting wire coils to said pipe, and a layer of refractory material surrounding said pipe and intimately contacting said pipe and the Wire of said coils.

13. The insulated furnace pipe construct-ion of claim 12 further characterized in that the diameter of said substantially high temperature heat resisting wire coils is less than the diameter of said relatively low temperature heat resisting wire coils.

14. An insulated furnace pipe construction comprising amass? i i a pipe, a coil of substantially high temperature heat resisting wire extending circumferentially of said pipe, a substantially high temperature heat resisting tie wire extending through said substantially high temperature heat resisting wire coil and securing said coil to said pipe, a relatively low temperature heat resisting wire coil spaced from said substantially high temperature heat resisting wire coil and extending generally parallel thereto circumferentially of said pipe, a relatively low temperature heat resisting wire extending through said relatively low temperature heat resisting wire coil and securing said relatively low temperature heat resisting wire coil to said pipe, and a layer of refractory material surrounding said pipe and intimately contacting said pipe and the wire of said coils.

15. The insulated furnace pipe construction of claim 14 further characterized in that the diameter of said relatively low temperature heat resisting wire coil is slightly greater than the diameter of said substantially high temperature heat resisting wire coil, the thickness of said layer of refractory material being slightly greater than the diameter of said relatively lowtemperature heat resisting Wire coil.

16. The insulated furnace pipe construction of claim 15 further characterized in that said coils of wire are disposed in a spiral arrangement circumferentially and longitudinally of said pipe.

17. The insulation construction of claim 15 further characterized in that said substantially high temperature heat resisting wire coil is stainless steel.

18. An insulated water coiled skid pipe construction comprising a pipe, longitudinally extending skid means secured to said pipe, a plurality of coils of substantially high temperature heat resisting wire extending circumferentially of said pipe, a substantially high temperature heat resisting tie Wire extending through each of said coils, V

stud means extending from said pipe on opposite sides of said skid means, the opposite ends of said substantially high temperature heat resisting tie wires being secured to corresponding stud means to secure said substantially high temperature heat resisting wire coils to said pipe, a plurality of relatively low temperature heat resisting wire coils interspersed with and spaced from said substantially high temperature heat resisting wire coils and extending circumferentially of said pipe, a relatively low temperature heat resisting tie wire extending through each of said ture heat resisting wire coils are substantially toroidal in configuration, the diameter of said substantially high temperature heat resisting wire coils being somewhat less than the diameter of said relatively low temperature heat resisting wire coils.

20. A method of insulating a pipe for use in high temperature furnaces comprising the steps of encircling the pipe with a coil oi substantially high temperature heat resisting wire, securing the coil of substantially heat resisting wire to the pipe with a tie wire passing therethrough, encircling the pipe with a coil of relatively low temperature heat resisting wire extending substantially parallel to said coil of substantially high temperature heat resisting wire, securing said coil of relatively low temperature heat resisting wire to said pipe with a tie wire passing therethrough, and covering the pipe and coils with a layer of plasticized refractory material such that the refractory material encompasses and surrounds the wire coils and comes into intimate contact with the surface of the pipe and the wire, and allowing the refractory material to harden in this relationship.

21. The method of claim 20 further characterized in that said coil of substantially high temperature heat resisting wire has a lesser diameter than said coil of relatively low temperature heat resisting Wire.

22. The method of claim 21 further characterized in that said pipe is encircled with a plurality of substantially high temperature heat resisting wire coils and a plurality of relatively low temperature heat resisting wire coils in sequential relationship, spaced longitudinally of said pipe.

Stanbery et al Apr. 8, 1930 Bloom Nov. 2, 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 168 ,297 February 2 1965 John R. Brough It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 1, line 61, for "ski" read skid column 3, line 14, for "realtionship" read relationship line 26, for "plane" read planes column 6, line 18, for "provide" read provided column 11, line 31, for "coiled" read cooled Signed and sealed this 29th day of June 1965.

(SEAL) Attest:

ERNEST w. SWIDER EDWARD J. BRENNER Aitesting Officer Commissioner of Patents

Claims (1)

1. A REINFORCED INSULATING COVERING FOR A FURNACE PIPE COMPRISING INSULATION MEANS, SAID INSULATION MEANS INCLUDING COIL MEANS FABRICATED OF SUBSTANTIALLY HIGH TEMPERATURE HEAT RESISTING WIRE ADAPTED TO EXTEND CIRCUMFERENTIALLY OF THE PIPE, SAID COIL MEANS INCLUDING A SERIES OF CIRCUMFERENTIALLY EXTENDING COIL PORTIONS SEPARATED FROM EACH OTHER ALONG ANY LONGITUDINAL LINE THROUGH SAID INSULATING MEANS, THE WIRE OF EACH OF SAID COIL PORTIONS IN ITSELF COILING ABOUT AN AXIS ADAPTED TO ENCIRCLE THE PIPE, MEANS ADAPTED TO SECURE SAID COILS MEANS TO THE PIPE, SAID INSUALTION MEANS FURTHER INCLUDING A LAYER OF REFRACTORY MATERIAL ENCOMPASSING AND INTIMATELY CONTACTING THE WIRE OF SAID COIL MEANS AND ADAPTED TO INTIMATELY CONTACT AND SURROUND THE PIPE.

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