US2387883A - Heating apparatus - Google Patents

Description

HEATING APPARATUS 7 Filed July 27, 1943 3 Sheets-Sheet 1 ll. or 0 8 65 04 0: /4 4 1 Oct. 30, 1945. 2,387,883

G. E. DAKE HEATING APPARATUS Filed July 27, 1943 5 Sheets-Sheet 2 75 7/ 70 52 69 77 Y H J fi 55 50 76 Z/ 5555 55 4/ /6 7 9 3/ a 40 a 28 /2 52,592 58 J/ 650g 5. DA K5 Oct. 30, 1945. G. E. DAKE HEATING APPARATUS Filed July 27, 1943 3 Sheets-Sheet 5 Patented Oct. 30, 1945 HEATING APPARATUS George E. Dake, Parkersburg, W. Va., assignor to The Parkersburg Rig & Reel Company, Park ershurg, W. Va., a corporation of West Virginia Application July 2'7, 1943, Serial No. 496,357

7 Glaims.

This invention relates to a fire tube heating apparatus, and more particularly to such an apparatus principally intended for use in treating or breaking down oil emulsions.

An important object of the present invention is to provide a rugged and preferably portable heating apparatus which is particularly adapted for use in the oil fields for treating or breaking down all emulsions and wherein the structure of the apparatus is such as to render it easily assembled or disassembled to be readily set up and later serviced or inspected.

A further object is to provide such an apparatus which provides a particularly high degree of thermal efiiciency whereby most of the heating units are utilized in performing the desired work.

A further object is to provide a fire tube heating apparatus wherein the fire tube unit as a whole is so constructed as to utilize heat radiation, conduction and convection in such a manner as to evenly heat the body of liquid being treated throughout the length of the fire tube unit.

A further object is to provide a fire tube heater wherein the products of combustion flow in one direction through a fire-resistant tubular unit and in an opposite direction through a surrounding chamber housed within a steel or other metal heating tube, the path of movement of the products of combustion being of such length that most of the heating units will have been absorbed by the liquid under treatment before the products of combustion pass to the stack.

A further object is to provide novel mounting means for the heating means whereby either the burner unit or the fire tube unit or both may be readily removed from the apparatus for the inspecting or servicing of such units, or for the servicing or inspection of the interior of the apparatus A further object is to provide a demountable fire tube unit of the general character outlined above wherein the fire-resistant tubular member is formed of novel simple elements to reduce the cost of manufacture and increase the ease of assembly, while at thesame time improving the efiiciency of the apparatus.

A further object is to provide such an apparatus wherein the individual elements of the fireresistant tubular unit are so formed and arranged as to provide a turbulent or spiral flow of the flame and products of combustion from the burner to assist in the transfer of heating units to the liquid under treatment.

A further object is to provide novel inlet and outlet pipes for the material under treatment and novel means for mounting such pipes with respect to the apparatus to provide leak-proof joints while at the same time permitting the pipes to be easily inserted and just as easily removed for inspecting and servicing.

Other objects and advantages of the invention will become apparent during the course of the following description.

In the drawings I have shown several embodiments of the invention. In this showing 7 Figure 1 is a side elevation of one form of apparatus using a single fire tube,

Figure 2 is an end elevation of the same,

Figure 8 is an enlarged central vertical sectional view through the apparatus, parts being broken away,

Figure 4 is an axial sectional view through the fire tube, the refractory units being arranged to provide for a turbulent flow of flame and prod ucts of combustion,

Figure 5 is a transverse sectional view on line 5-5 of Figure 4, a portion of the outer casing and one of the supporting means for the fire tube being shown,

Figure 6 is a detailed perspective view of one form of refractory element,

Figure 7 is a similar view of a slightly modified form of such element.

Figure 8 is a sectional view of a fire tube similar to Figure 4 with the refractory elements so arranged as to provide for a spiral flow of the name and products of combustion,

Figure 9 is an end elevation of a modified form of apparatus showin the arrangement of parts when two fire tubes are employed,

Figure 10 is a similar view showing an apparatus employing three fire tubes,

Figure 11 is an end elevation of a modified type of refractory element formed of complementary sections, and

Figure 12 is a detailed fragmentary sectional view on line I2-l2 of Figure 11.

Referring to Figures 1, 2 and 3, the numeral H3 designates the cylindrical outer casing of the apparatus having dished heads H and I2 preferably welded thereto. The apparatus is preferably portable, and for this reason is provided with skids 13 secured to the casing It) by suitable preferably welded brackets !4. The skids may be braced with respect to each other by welded cross braces l5 (Figure 2).

The heating apparatus for the material in the casing It! comprises a fire tube unit indicated as a whole by the numeral 16 having burners to be described associated therewith. The fire tube unit I6 comprises a preferably steel outer casing I1 of cylindrical form closed at one end by a head I8 preferably welded in position in the adjacent end of the tube I1 at a point spaced from the head I2. Within the tube I1 is arranged a heat resistant tube unit indicated as a whole by the numeral I 9 and comprising a plurality of individual elements 20. The elements 20 are preferably formed of refractory material. If desired, however, the elements 20 may be formed of heat resistant cast iron or steel. Whatever material is used in the making of these elements, such material should possess a high degree of resistance to deterioration under heat and be capable of transferring heat by both conduction and radiation. These elements will be subsequently referred to as refractory elements and the tube I9 as a refractory tube. These elements when assembled, form a continous tube extending from the burner to be described to a point spaced from the head I8, whereby the flames and products of combustion from the burner will flow to the left as viewed in Figure 3 through the refractory tube, from the inner or left hand endof such tube, thence outwardly and back through the passage 2| formed between the refractory tube and the heating tube I1. If desired, a replaceable refractory disc I8 may be located in the end of the tube I1 to withstand erosion caused by de-' fleeting and directing thepassage of hot gases.

The refractory elements 20 may be of various forms and. the particular form illustrated in Figure 3 is shown in perspective in Figure 6. Such refractory element comprises a cylindrical body 22 having a plurality of radially extending longitudinal ribs 23 adapted to contact with the tube I1 to position each of the elements 20. Each of these elements is further provided with internal radial ribs 24 which are contacted with by the flame and products of combustion within the refractory tube and act thereon in accordance with the arrangement of the ribs 24 of successive elements 20. Each rib 24 is preferably in radial alignment with one of the outer ribs 23. The refractory elements are successively inserted from the right hand end of the tube I1 (Figure 4) and are pushed through such tube until the first inserted element engages stop means, such as the ring 25. When the ribs 23 and 24 are referred to are in staggered relation as shown in Figure 4, the flame and products of combustion will be agitated and will pass through the refractory unit I9 in a highly turbulent condition, thus insuring a wiping action of the flames and products of combustion against the successive cylindrical portions 22 of the re fractory elements. The ribs 23 are similarly arranged in staggered relation and accordingly will effect a similar turbulence in the products of combustion flowing toward the right in Figure 3 through the passage 2|. This turbulence in the passage 2I insures a wiping action of the products of combustion against the heating tube I1 and a consequent absorption of heat by this tube and a conduction of heat to the liquid in the casing ID.

A slightly modified form or refractory element is shown in Figure 7 and corresponding parts are indicated by the same numerals as in the previously described form. The only difference in the two units lies in the fact that the refractory unit in Figure 7 has a lug 26 projecting from one end thereof as a continuation of the cylindrical body 22, and the opposite end of such. y

is provided with a similarly shaped recess 21. The lug 2B is slightly off-set circumferentially from the recess 21 and when received in the recess 21 of the next adjacent refractory element, such adjacent elements will have their ribs only slightly circumferentially offset instead of staggered as in the previous form of the invention. The result of such arrangement is shown in Figure 8, and it will be apparent that instead of creating turbulence in the flow of the flame and products of combustion, there will be a spiral arrangement of the ribs internally and externally of the refractory unit, thus causing a spiral wiping of the hot gases against the inner face of the refractory unit and against the inner face of the heating tube I1. This provides the same results as the turbulence effected by the staggering of the ribs, a more effective heat transfer being accomplished.

It will be obvious, of course, that the spiraling of the ribs as in Figure 8 can be accomplished with the form' of refractory element shown in Figure 6, but the provision of the lugs 26 and recesses 21 facilitates the uniform relative spiraling of the ribs and insures against misplacement of the ribs of one unit relative to the ribs of the next adjacent units. Of course, the ribs 23 could be molded in spiral form, but this is unnecessary in order to secure the desired swirling action of hot gases, and the straight longitudinal ribs are somewhat more economical to manufacture.

The head I I is provided with an axial opening 30 in which is welded one end of a sleeve 3| and this sleeve is slightly larger than and freely receives the heating tube I1. The tube 3I is provided with a radial flange 32 welded thereto and the heating tube I1 is provided with a similar flange 33 bolted as at 34 to the flange 32 with a gasket 35 interposed between the two flanges to provide a leak-proof joint. Thus, while the heating tube I1 is readily insertable into the casing I0 and removable therefrom, the connecting means comprising flanges 32 and 33, bolts 34 and gasket 35 provide effective means forpreventing the leakage of liquid from the casing I0 around the tube I1. This tube, when in position in the casing I0, rests on a plurality of cross members 31, which may be in the form of angle irons welded at their extremities to the casing I0. To prevent destruction of the tube by concentrated corrosion and hot spots at points of contact with the supports, a plurality of spacing and reinforcing lugs 36 are welded to the tube at these points. These spacing lugs are so tapered (Figures 4 and 8) as to permit them to slide up and on the supports when the tube is inserted in the heater. Also provided is a guide ring 36' which contacts the spacing lugs and provides for support in transit. These spacing lugs also provide clearance between the outside of the tube and the guide ring and the supports 31 so that anyscale or salt that may deposit on the outside of the tube will not prevent removal of the tube. So long as this deposit does not become thickerthan the depth of these lugs, it will not cause obstruce tions when it is desired to remove the tube.

A burner casing 38 (Figure 3) has its inner end projecting into an enlarged axial recess 39' in the adjacent end of the adjacent refractory element 20 coaxial with the fire tube unit. The outer end of the burner casing 38 is preferably welded to a relatively heavy flange 39 bolted as at 40 to a flange 4I carried by the outer end of the tube l1.

A burner block 42 is arranged in the inner end of the burner casing 38 and seats against a plate 43 welded in the casing 38. Suitable burners are provided and in the present instance it is preferred to employ four burner nozzles 44 supplied with either gaseous or liquid fuel through pipes 45. The burner block 42 is provided with an opening 46 aligned with each burner nozzle 44, the plate 43 obviously being similarly apertured for the passage of fuel therethrough from each burner nozzle. A pilot burner pipe 41 projects axially through the casing 38 and through the burner block 40.

A plate 48 is attached to the flange 39 to extend across the outer end of the burner casing 38. The plate 48 supports all of the pipes 45 and 41 and is cut away as at 49 for the admission of air to support the combustion of the fuel leaving the nozzles 44. A cooperating adjusting plate 50 is slidable on the pipes 45 to govern the rate of admission of air into the burner casing.

An outlet connection 51 is welded to the tube I1 for the flow of products of combustion from the passage 2| to a conventional stack 52, the connection and the stack being flanged as at 53 to be bolted together as at 54. A suitable damper 55 is preferably arranged in the stack 52.

The liquid to be treated, such as an oil emulsion, is fed into the casing Ill through an inlet pipe 58. To enable the casing to receive this pipe, the head H is apertured as at 59 and a short tubular extension 611 is welded in the opening 59. An attaching flange 6! is welded to the outer end of the tubular extension 60 and is bolted as at 62 to a flange B3 welded on the inlet pipe 58, a gasket 64 being interposed between the flanges 5i and 63 to provide a leak-proof joint. The pipe 58 is provided in the bottom thereof with a few openings 65, which need not be over three in number, for the flow of oil into the bottom of the casing ID to insure circulation of the oil in the casing H) from the bottom thereof. These openings also permit any sediment or any relatively heavy foreign matter in the oil to drain into the bottom of the casing In, and sediment can be drained from the casing through a drawoif pipe 65.

The inlet pipe 58 extends throughout the greater portion of the length of the casing l0 and. may be supported in position by suitable saddles 61. Preferably substantially throughout its length, the top of the pipe 58 is provided with fairly closely arranged relatively small outlet openings 68 for the flow of the emulsion or other liquid upwardly toward the heating tube H.

The casing is provided adjacent the top thereof with means for drawing off the heated liquid and for this purpose an outlet pipe 69 is employed which may be identical with the pipe 58. The head 12 is apertured as at 1!! and a tubular member H is welded in this opening and flanged at its free end as at I2 to be bolted as at E3 to a flange I4 welded on the pipe 69. A gasket is interposed between the flanges 12 and 14 to provide a leak-proof joint. Within the casing Ill, the pipe 69 is supported by suitable hangers 15. The pipe 69 is provided with openings 76 in the bottom thereof, which may be identical with the openings 68, andthe top of the pipe 69 is provided with openings 11 which may be identical in size and arrangement with the openings 65. Both of the pipes 58 and 69 have their inner extremities closed so that liquid flowing into and out of these pipes must flow through the various openings 65, B8, 16, and 71, as will be obvious.

In Figure 9 of the drawings, a modification of the invention is shown wherein a heating apparatus of larger capacity is employed and is provided with two of the heating units. Most of the parts in Figure 9 are identical with those previously described and have been indicated by the same reference numerals. It will be apparent that two complete sets of the burner supply tubes 45 have been shown in Figure 9, and these tubes have the same burner nozzles and associated elements employed therewith as in the form 'of the invention previously described using a single burner unit. The inlet pipe 58 is identical with that previously described, and this is also true of the casing 10 except that the casing is larger in size to provide for greater capacity. The only difference in the structure of Figure 9 as compared with the form of the invention previously described, aside from the duplication of the heatingunits, lies in the fact that the lower end of the stack, instead of being directly secured to a. single stack connection 5 I, as in Figure 3, is flared as at 8B (Figure 9) and is bolted as at 8| to the flanges at the upper ends of the duplicate stack connections 5|, one of these connections being employed for each associated unit as will be ob-' vious.

In Figure 10 a further modification is shown wherein there is again involved largely a duplication of the same elements as previously described for providing a heating apparatus of even larger capacity, three heating units being employed as identified by the reference numerals applied to the various elements of the heating units and corresponding to the reference numerals of the identical elements in Figure 2. In the form of the invention shown in Figure 10, the upper or central heating unit has its stack com nection 5| arranged in the same manner as in Figures 2 and 9. The stack connections 5| of the other heating units are inclined upwardly and outwardly from the center of the apparatus and are bolted to vertical connections 82, the upper ends of which are directly welded to the lower end 83 of the stack, such portion of the stack forming a manifold to receive the products of combustion from the three heating units. The central portion of the manifold 83 is flanged as at B4 to be bolted as at 85 to the central stack connection 55. In the form of the invention shown in Figure 10 all of the elements are identical, except for the duplication of the heating units and the difference in the size of the casing 18, with the various units previously described, except for the addition of the two stack connections 82 and the use of th manifold 83. Thus it will be apparent that the same inlet and outlet pipes, the same burner units, the same fire tube units, etc; may be employed in the ap paratus as made in different sizes and capacities. This greatly simplifies the manufacture of parts of the apparatus for heaters of difierent capacities.

In Figures 11 and 12 of the drawings, there is shown a modified form of refractory element formed of a plurality of identical pieces adapted to be assembled to form a single element. Referring to Figure 11, the numeral designates the refractory element as a whole formed of a plurality of segments 9| adapted to be assem= bled in cylindrical form and each provided in its radial edge with a groove 92. The groove in each edge registers with the groove in the ad-. jacent contacting edge to. form a space to receive a cementitious filler 93 to join the elements together. Each segment is provided. atone end thereof with an outstanding rib 94, 'these ribs corresponding to the external ribs 23 of the refractory elements previously described. Each segmentis likewise provided with an inside rib 95, and these ribs correspond to the internal ribs 24 described in connection with the previous forms of refractory elements. The element 90 may be made with any desired number of sections, but it may be conveniently and economically formed of four sections as shown in Figure 11.

The respective side edges of the unit 90 are provided with a rib 96, and a groove 91, bothof which are annular. It will be obvious that the rib 9B of each refractory element is receivable in the groove 91 of the next adjacent element. The refractory element shown in Figures 11 and 12 is advantageous for two reasons. In the first place the making of the element in complementary sections simplifies the molding operation since no cored mold is required. In the second place, each element 90 can adjust itself to the heating tube I 1 when inserted, thus relieving it from internal strains which might cause it to crack when in use. It will be obvious that the casting in one piece of a device of the character'shown in Figures 6 and 7 can easily result in distortion of the ribs 23 so that the outer edges thereof do not lie in a true cylinder. Under such conditions an element l9 might fit too tightly in the tube ll, thus resulting in internal stresses under the influence of heat which would cause the element l9 to crack. This diificulty is eliminated in the sectional element 90, as stated, and the segments 91 being identical, the manufacture of such segments may be economically carried out.

The operation of the apparatus shown in Figures 1, 2 and 3 is as follows, assuming that the refractory element in Figure 6 is employed with the ribs 23 of the successive elements staggered as in Figure 4:

The apparatus is particularly intended for use in treating oil emulsions in the field, and such emulsions sometimes are treated by heating water and then mixing it with the emulsion in a separate receptacle while in other cases, the emulsion itself is circulated through the heater. The apparatus has general application for the heating of liquids, and accordingly reference will be made generally to the passage of liquid through'the casing 10; The liquid is fed to the casing in through the inlet pipe 58, most of the liquid being discharged upwardly through the openings 68. Some of the liquid will pass downwardly through th openings 65 to prevent the maintenance of the same liquid in the bottom of the casing ID, the openings 65 also permitting the settling out of the pipe 58 of any foreign matter which may collect in the bottom of such pipe. The flow of the-liquid takes place generally upwardly around the heating tube I! to absorb heat therefrom, and the liquid flows into the pipe 59 through openings 16 and 11 to be discharged from the apparatus.

The fuel from the burner nozzle is directed through the opening 46 Where it is intermixed with air and after passing through the throat of the opening 46, is ignited by the pilot 41. The

flame and products of combustion then pass longitudinally through the refractory tube unit l9. This tube, or a substantial portion thereof, may be heated to incandescence. and the hottest part of the flame and gases will be adjacent the burner openings with the temperature of the tube decreasing progressively toward the opposite end of the tube unit l9. An efiicient absorption of heat by the unit I9 is insured by the staggering of the ribs 24 to create substantial turbulence in the flame, the latter thus being caused to wipe against the interior of the unit l9 instead of providing a streamlined flow wherein the central portion of the flame would travel directly from end to end of the unit I9 without contacting with the wall thereof. a

It will be apparent that the intense heating of the inner wall of the unit [9 will result in the passage of radiant heat to the liquid in the casing ID, the gradient of this heat throughout the length of the unit l9 being in proportion to the temperature gradient. The burning of the fuel will have been completed by the time the flame reaches the left hand nd of the unit l9 as viewed in Figure 3, and the products' of combustion thereupon flow radially outwardly, as indicated by the arrows in Figure 3, to enter the passage 2| and flow to the right therethrough as viewed in Figure 3. The temperature of the products of combustion will be highest adjacent the left hand end of the tube I1 and the temperature will progressively decrease in the flow of the products of combustion toward the stack. Bythe conduction of heat through the metal of the tube l7 and thence by convection, the liquid in the casing [0 will absorb heat from the products of combustion, thus accounting for the progressive dropping in the temperature of the products of combustion as they approach the stack. Therefore, while the radiant heat has its temperature decreasing toward the left as viewed in Figure 3, the temperature of the products of combustion will decrease toward the right, and the result is the uniform absorption of heat by the liquid in the casing I0 throughout the length of the tube H. In actual practice, therefore, the apparatus has been found to be highly-efficient for utilizing the heat of a combustion for raising the temperature of the liquid being treated. As a matter of fact, extensive tests conducted with the apparatus indicate a thermal efficiency of 83%.

The products of combustion are relatively cool when they reach the right hand end of the passage 2| (Figure 3) and from such passage they flow upwardly through the stack 52. It will be obvious that the combustion is subject to flexible regulation by adjusting the plate 50, the conventional valves (not shown) in the pipes 45, and the damper 55. The size of the flame can also be changed by substitution of other nozzles 44. The apparatus possesses numerous structural advantages which render it particularly adapted for use in the field for treating oil emulsions, although the same advantages are present in any use of the apparatus. The inlet pipe 58 is readily removable to be inspected or serviced by removing the bolts 62, while the same operations may be performed as to the outlet pipe 69 by removing the bolts 13. The joints by which these pipes are secured in position are rendered leakproof by the Welding of the flanges 63 and 14 to the respective pipes, by the welding of the pipes 60 and H to the heads H and I2 respectively, and by the use of the gaskets 64 and 15. The burner nozzles readily may be removed for clean ing or other servicing by removing the bolts 40 and withdrawing the plate 39 together with the pipes 45 and 41 and the burners 44. The operation just referred to, of course, also provides for aeszssa the removal of the burner pipe 38 and burner block 12, and if it is desired only to remove the burner pipes and associated elements, this can be accomplished by leaving the plate 39 in place and removing the bolts 48.

The entire fire tube unit may be removed by disconnecting the stack bolts 54 and the bolts. 34, whereupon the heating tube and all of the ele merits arranged therein and associated therewith may be bodily withdrawn from the apparatus. Thus it will be apparent that all parts of the fire tube assembly are rendered accessible, and the removal of the entire fire tube unit permits the entrance of a workman into the apparatus through the tube 3| to inspect the interior of the apparatus or to make any necessary repairs therein. Each of the tubes 31, 60 and TI is larger than the elements introduced therethrough into the apparatus,- thus permitting such elements to be easily and freely inserted into position. The

flanged and bolted securing means for the elemerits, however,- provides a fully leak-proof joint at each necessary point.

The removal of the inlet or outlet pipe 58 or 69, or both, provides an opening or openings of ample size for the introduction of suitable tools for cleaning the interior of the casing l9 without having to remove the fire tube structure.

The operation of the apparatus using the arrangement of refractory elements shown in Figure 8 is substantially identical with that described. The refractory elements of the type shown in Figure 7 may be employed and the lugs 26 and recesses 21 may be properly oifset from each other to secure the desired spiral arrangement, and this arrangement of the successive ribs will occur automatically upon the insertion of each rib 26 in the recess 21 of the next adjaeentelement. The refractory element in Figure 6 also may be used with the ribs 23 spiralled, but it is necessary to set the successive elements by hand. The use of such an element as is shown in Figure '7 is therefore preferable in such arrangement. The spiralling of the ribs imparts a swirling motion to the fiame and to the products of combustion in the passage 2| to cause a wiping thereof against the respective walls of the refractory unit i9 and heating tube 11.

The operation of the forms of the invention shown in Figures 9 and 10 is identical with that previously described, the modified forms of the invention merely largely employing a duplication of certain of the elements of the apparatus to provide an apparatus of greater capacity as will be obvious. Each of the burner unit assemblies in Figures 9 and 10 is identical with that shown in Figure 3, and the same is true of the inlet and outlet pipes.

The form of the invention shown in Figures 11 and 12 adds nothing to the performance of the apparatus as a whole but possesses certain advantages in itself. The making of each refractory element of four pieces greatly minimizes the cracking of these elements and prolongs the life thereof, and each element assembly is relatively cheap to manufacture since the individual pieces are identical with each other and may be molded more quickly and easily because of their simplicity and the lack of the necessity for using a mold core.

From the foregoing it will be apparent that the present apparatus embodies numerous distinct advantages. Complete and efiicient combustion is secured due to the generous size and length of the combustion chamber as a whole, including the interior of the refractory unit i9 and the passage 2|. No flame comes into direct contact with any metallic surface, thus preserving the metal parts of the burner assemblies against oxidation. Before coming into contact with the heating tube H, the temperature of the products of combustion will have been reduced by the amount of heat radiated to the fluid. The heat transfer to the fluid being treated takes place evenly around and throughout the length of the heating tube i1, and this even distribution of heat minimizes the formation of scales on the outside of the heating tube. The high thermal efliciency of the apparatus is due to the utilization of radiation, convection and conduction for transferring heat to the liquid under treatment, as described above. The apparatus is obviously advantageous from the standpoint of ease of assembly and of dismantling for cleaning, inspecting or repairing the various parts of the apparatus.

It is to be understood that the forms of the invention herewith shown and described are to be taken as preferred examples of the same and that various changes in the shape, size and arrange ment of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

I claim:

1. A heating apparatus comprising an elongated casing, a pair of tubular elements in spaced parallel relation having sealed connection with said casing and open from endto end between the interior of said casing and the exterior thereof, an inlet pipe projecting through one tubular member and an outlet pipe projecting through the other tubular member, said pipes within said casing being provided with openings for the passage of fluid to be heat-treated in said casing, an annular flange carried by the outer end of each tubular member, a cooperating flange carried by each pipe, means for securing the flange of each pipe in leakproof relation to the flange of the associated tubular member, and a heating unit projecting into said casing between said pipes to heat the fluid flowing through said casing.

2. A heating apparatus comprising an alongated casing, a pair of tubular elements in spaced parallel relation having sealed connection with said casing and open from end to end between the interior of said casing and the exterior thereof, an inlet pipe projecting through one tubular member and an outlet pipe projecting through the other tubular member, said pipes within said casing being provided with openings for the passage of fluid to be heat-treated in said casing. means for efiecting detachable leakproof connection of each pipe to its associated tubular member, a relatively large tubular member having sealed connection with said casing in parallel relation to said pair of tubular members and open from end to end, a heating unit projectin through said relatively large tubular member, and detachable means for connecting said heating unit t the outer end of said relatively large tubular member.

3. A heating apparatus comprising an elongated casing, a pair of tubular elements in spaced parallel relation having sealed connection with said casing and open from end to end between the interior of said casing and the exterior thereof, an inlet pipe projecting through one tubular member and an outlet pipe projecting through the other tubular member, said pipes within said casing being provided withopenings for the passage of fluid to be heat-treated in said casing, an annular flange carried by the outer end of each tubular member, a'cooperating flange carried by each pipe, means for securing the flange of each pipe in leak-proof relation to the flange of the associated tubular member, a relatively large tubular member having sealed connection with said casing in parallel relation to said pair of tubular members and open from end to end, a heating unit projecting through said relatively large tubular member, an annular flange carried by the outer end of said relatively large tubular member, a cooperating flange carried by said heating unit, and detachable means for connecting the two last mentioned flanges.

4. A heating apparatus comprising a casing, means for introducing to and discharging from said casing a fluid to be heat-treated therein, a tubular extension communicating with the interior of said casing, said tubular extension having permanent leakproof connection with one wall of said casing and having its other end projecting outwardly therefrom, and a fire tube heating unit inserted into said casing through said tubular extension, said heating unit and the last named end of said tubular extension having cooperating annular flanges detachably secured in leakproof relation to each other, said heating means having an axial passage and an annular passage communicating with each other adjacent the end of said heating unit in said casing, and burner means mounted to project a flame into the other end of said axial passage.

A heating apparatus comprising a casing, means for introducing to and discharging from said casing a fluid to be heat-treated therein, a tubular extension communicating with the interior of said casing, said tubular extension having permanent leakproof connection with one wall of said casing and having its other end projecting outwardly therefrom, and a fire tube heating unit inserted into said casing through said tubular extension, said heating unit and the last named end of said tubular extension having cooperating annular flanges detachably secured in leakproof relation to each other, said heatingunit comprising a tube imperforate from the flange of said heating unit tothe end of such unit within the casing, the latter end'of said imperforate tube being sealed, a refractory unit concentric with and spaced'from said tube to form' an annular passage, said refractory unit having an axial passage communicating with said annular passage at said end of said heating unit, and burner means for projecting a flame into said axial passage from the other end thereof.

6. Apparatus constructed in accordance with claim 20 wherein the flange of said heating unit is intermediate the ends of said imperforate tube whereby the outer end thereof projects substantially beyond said flanges, said outer end of said imperforate tube having an annular flange, said burner means comprising a burner tube having a flange detachably connected to said last named flange and projecting into said imperforate tube, and a burner in said burner tube for directing a flame through said axial passage.

7. A heating apparatus comprising a casing, means for introducing to and discharging from saidrcasing a fluid to be heat-treated therein, and a heating unit projecting a substantial distance into said casing through one wall thereof, said heating unit having leakproof connection with said wall and comprising a tube having a sealing cap closing its inner end, a refractory unit in said tube formed of a plurality of refractory elements each having a cylindrical body and radially outwardly projecting ribs contacting the inner surface of said tube to axially aline the cylindrical bodies of said elements in spaced relation to said tube whereby the latter and the cylindrical bodies of said elements define an annular passage, the element adjacent the inner end of said tube being spaced from said cap whereby the space within said cylindrical bodies communicates with said annular passage, and a fuel burner for projecting a flame into said refractory unit adjacent the outer end thereof, at least some of said refractory elements having interior ribs to effect agitation of the flame passing through said refractory unit to increase the absorption of heat by said refractory unit from the flame passing 40 therethrough, said refractory elements and their interior ribs, the length of said refractory unit and the character of the flame from said burner being so related that combustion of the fuel from said burner is substantially completed within the 1 length of said refractory unit whereby the outwardly radiated heat from said refractory unit will decrease from said burner to said cap and the temperature of the products of combustion passing through said annular passage will decrease in the direction of flow of the products of combustion to substantially evenly heat the fluid in said casing from end to end of said heating unit.

GEORGE E. DAKE.

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