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Publication numberUS1685388 A
Publication typeGrant
Publication dateSep 25, 1928
Filing dateDec 15, 1923
Priority dateDec 15, 1923
Publication numberUS 1685388 A, US 1685388A, US-A-1685388, US1685388 A, US1685388A
InventorsRaymond E White
Original AssigneeTubal Boiler Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Boiler construction
US 1685388 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

Sept. 25, 1928. I 1,685,388

R. E. WHITE BOILER CONSTRUCTION Filed Dec. 15, 1923 8 Sheets-Sheet 1 Sept. 25, 1928.

1,685,388 R. E. WHITE BOILER CONSTRUCTION Filed DEC- 15, 1923 8 Sheets-Sheet 2 Sept. 25, 1928.

1,685,388 R. E. WHITE BOILER CONSTRUCTION Filed Dec. 15. 1925 s Sheets-Shet s Sept. 25, 1928.

R. E. WHITE BOILER CONSTRUCTION 8 Sheets-Sheet 4 Filec} Dec. 15, 1923 Sept. 25, 1928.

R. E. WHITE BOILER conswnucnou' Filed Dec. 15, 1.923 3 Shees-Shet 5 QQQ Sept. 25,1928.

R. E. WHITE BOILER CONSTRUCTION B Sheets-Sheet 6 I Filed D60. 15, 1923 mum w Sept. 25, 1928.

R. E. WHITE BOILER- CONSTRUCTION Filed Dec. 15, 1923 8 Sheets-Sheet 7 Sept. 25, 1928. 1,685,388

R. E. WHITE BOILER CONSTRUCTION Filed Dec. 15, 1923 8 Sheets-Sheet 8 7 m ss s" 5 Qyflvenw Patented Sept. 25, 1928.




Application filed December li, 1923. Serial No. 680,804.

My invention relates to a novel form of boiler and the method of and means for constructing the same.

While I shall describe .in the following specification a specific embodiment, namely, a drumless water tube sectional type of boiler, it is to be understood that this is merely for purposes of illustration and that the invention v is not limited to such form alone. However, W I wish to call attention to the fact that my present invention is peculiarly adapted to a boiler section, or to a boiler, or, in fact, a containing vessel of any kind in which there is no great disparity between the sizes of the connected tubes or passageways. The invention is adaptable to banks of 'tubes,'or boiler sections, or any kind of heat transfer apparatus,

pressure containers and the like.

Referring to the accompanying drawings illustrating a preferred manner of practicing my invention Figure 1 is an elevational view of one of the blank sheets employed in making 511p a boiler section; I I

Fig. 2 is a similar view showing two of these sheets welded together around their perimeters to form a closed envelope, the

light lines indicating the marginal weld;

Figures 3 and 4c are longitudinal sectional and end elevational views of a typical form of'die mechanism in. which the metal is'expanded outwardly between these. lines of welding; v A

Fig. 5 is a side view of a section made in ac:

cordance with the steps illustrated in Figures Fig. 6 is a fragmentary view showing the bottom connection to the water manifold;

Fig. 7 illustrates the blank sheet employed in another practice of my process;

Figures 8 and 9 are side elevational and edge views respectivelyof this latter sheet after folding;

Fig. 10 is a side elevational view of the blank after it has been welded around the edges to form a closed envelope, and after the steam connection has been welded between the side walls of the envelope;

Fig. 11 illustrates in light lines the lines of contact maintained between the side Walls during the expanding operation carried on in apparatus of the type shown in Figs. 3 and l;

Fig. 12 is a side view of one form of boiler blank as employed in another performance of my process;

Fig. 16 is a similar view, indicating by dotted lines the profile of the section and the lines of contact between which the passageways are bulged outwardly in the plate;

Fig. 17 is a more or less diagrammatic showing of die mechanism in which the blanks are subjected to pressure to bulge out the passageways;

Fig. 18 is a sectional view through two blanks that have been subjected to the above expanding operations, these blanks being ready for oining into a section unit;

Fig. 19 is a sectional view through a boiler setting, illustrating a typical design of boiler section as constructed by my invention;

Fig. 20 is another sectional view through the same at right angles to Fig. 19;

Fig.21 is a transveise sectional view of'the boiler, and

Fig. 22 illustrates another design of boiler section produced by my invent-ion assembled.

in a circular type of boiler.

In carrying out one process of manufacturing a boiler according to my invention, two sheet metal plates 21 are first cut to approximately the size and general profile of the completed boiler section. These sheets are then ,matched and welded together aroundtheir perimeters, as indicated in light "lines at 22. This welding is preferably performed according to the Gefei process of seam welding, employing the electric roll-step method. In

the step of welding the two sheets together, a

nipple or plug connect-ion 23 is welded between the sheets at the upper corner, where it will be in line with a steam outlet conduit of the sect-ion. If desired, the water connection may be employed instead The result is a metallic envelope having integrally united edges and a nipple fitting welded therein through which fluid pressure may enter the envelope.

This envelope unit is now subjected to the expanding operation, wherein the circulating tube areas and the header-areas of the comwith recesses 32 corresponding to the bulged circulating tube and header areas in the completed section. The envelope is, of course, so matched with respect to these recesses 32 that the bulged tube and header areas will occur in the proper places in the envelope. The lower forming die 27is preferably heated, as by providing longitudinal burner openings 3- into which extend burner tubes 35. .21)

These burner tubes are supplied with fuel from suitable burner nozzles discharging into the tubes. The desirability of heating the dies and the sheet metal envelope is dependent upon the gauge of metal being worked and the depth of the draw necessary in the expanding operation. \Vith relatively light gauge materials, the expanding operation can be performed with the dies and the materialcold.

A high pressure fluid, such as high pressure superheated steam, or water, is now forced into the envelope through the nipple connection 23. This pressure will swell or expand the metal in the two walls of the envelope out into the upper and lower die recesses 32 for forming the circulating tube and header areas. The flat die surfaces 33 intermediate the parallel recesses 32 (which form the inclined circulating tubes) retain the intervening web portions between these tube areas in substantially the same plane as the original sheet, so that. the opposite web portions of both sheets can be subsequently welded together. The two walls of the envelope need not be rigidly clamped together between the tube areas during this expanding operation; and, in fact, it is pieferable to hold the sheets in such relation that they can slip on each other in the expanding operation, so that the metal can be drawn from all portions ofeach sheet and a uniform distribution and attenuation of the metal secured. Irrespective of whether or not the dies are forced together under any pressure, it is necessary that an exceedingly strong frame or other supporting structure be provided for holding the dies together against the very large outward pressure exerted through the walls of the envelope, tending to separate the dies.

Where steam is employed as the expanding fluid, the high temperature of the steam will assist the lower heated die 27 in heating the two walls of the envelope.

The envelope or section, after the completion of'the expanding operation, is illustrated in Fig. 5. While, of course, any preferred arrangement of circulating tubes and headers may be shaped in the section, I have shown a circulating arrangement which I consider has numerous advantages over present day boiler sections. It is opportune to remark that the present method permits of innumerable paths and circuits for the water and steam in each section, to meet the fancy of any steam engineer, without materially increasing the cost of the section. I-leretofore, the practice of subdividing a header into a-plurality of sections and of forming devious paths for the circulating water and steam was impracticable because of the very high expense of forming and welding these circulating tubes and headers together at various angles and in-close proximity. In the form shown, the outer header is constructed of outer and inner sections 25 and 26, which give a very large header area without increasing the thickness of the boiler section. Similarly, the rear header is constructed of outer and inner header areas 37 and 38. These co-operating header areas are, in each instance, connected by cross channels 39, arranged at any desired points for establishing cross communication between the header sections and the circulating tubes 40. The

for connection to the mud-drum of the boiler,"

as I shall hereinafter describe.

The next step in the process is to weld the two walls of the envelope together upon all the partition lines between the tubes and headers. This welding is preferably preformed according to the Gefei process of seam welding, employing the electric rollstep method; electric spot welding may, of course, be employed in lieu of the above method, but I find the roll-step method to be preferable because of its greater rapidity and the evenness of the seam. All of the joining lines or sunken areas 42 are welded together by this process, both between the circulating tubes 40 and between the diiferent portions of the headers. The ends of the welded lines 42 are preferably reinforced against separation by performing a pressure spot weld at each end of each line, as indicated at 43. The diameter of each of these spot a greater area of metal for providing ample reinforcement. Another expedient for reinforcing the ends of the seam welds is to drill these ends and rivet in suitable rivets where the spot welds are now shown. This rivet reinforcement of the endsof the seam weld mav be employed in conjunction with spot welding or without. For example, the end of each line of seam welding may be spot welded, as first described, and this spot we ded area then drilled for the reception of the rivet. This would integrally unite the two walls of the envelope around the rivet hole. A rivet reinforcement of the ends of the lines of welding is shown in Fig. 19.

The header areas and 37 and the endmost tubes 36 and 40 may be expanded out to the marginal weld 22, which circumscribes the edges of the sheets; or thes header and tube areas may be set inwardly considerably from the marginal weld 22, for the purpose of performing a second inner marginal weld 22 around the outline of these header and tube areas during the process of welding the intermediate lines 42. IVhen this second in-' ner marginal weld 22' is employed, the projecting flange or web and the outer weld 22 are preferably-trimmed off around the entire perimeter of the section. The advantage of this latter method is that the marginal weld is subjected to no strain or attenuation of metal during the expanding operation,

and furthermore, the metal which is drawn in the shaping of these outer header and tube areas has a relatively free sliding motion for an even distribution of the metal, the outer marginal weld 22 being spaced considerably from where the greater portion of this metal is drawn.

' The next step is to complete a feed water connection with the lower leg 41 of the rear header. As shown in Fig. 6, this lower leg 41 is out off to open up the bottom of the header; if the header is slightly crimped or distorted. this lower end is restored to cylindrical form by the insertion of a suitable shaping tool. A tubular drift is then forced up into this cylindrical 1eg,'and is securely welded therein, such as by a welding fillet 45 around the lower edge of the leg 41, or by.

spot welding or seam welding the leg 41 and the drift 4% together. The lower end of this tubular drift is tapered inwardly on a spherical curvature, as indicated at 46, and this spherical end seats on a conical seat 47 formed in the upper end of a connecting nipple 48. This nipple 48 is welded to the top of a muddrum or feed water header 49, having communicatipn therewith through the port 51 cut in the top of the drum 49. The spherical end 46, seating on the conical face 47, secures approximately a line contact therewith. For holding surfaces 46 and 47 together against the pressure prevailing in the section, a relatively fixed wedge-like plate 52 is extended transversely through the connecting tube 44,

being passed through directly opposite slots cut in the tube. This plate is welded in these slots to integrally unite the plate with the tube 44 and to seal the tube around the plate to hold the steam pressure. The ends of the .plate 52 project from the drift tube 44, and

hooking over each of these ends is an eye bolt 53. These two eye bolts extend down and. pass through apertures in theends of a saddle block 54, engaging under the drum 49 and receive nuts 55, by which the spherical surface can be drawn down into rigid engagement with the conical surface 47. It will be observed that the section is quickly releasable from the mud-drum 49 by merely unscrewing the nuts 55 sufficiently to allow the eye bolts 53 to be cleared from the upper shoulders of the plate The steam connection attaching to the upper steam outlet nipple 23 will be, hereinafter described in a description of a typical boiler setting built up of my improved boiler sectlons.

A modification of the foregoing method is illustrated in Figures 7 to 11 inclusive. According to this method, the blank is cut with two diagonally disposed portions which form both walls of the metallic envelope. In folding the two halves of the blank together a tubular conduit or enlargement 56 is formed along the lower diagonal edge of the envelope, as shown in Figures 8 and 9. After the completion of this folding operation the edges of the blank are welded together around the sides and top. as illustrated at 22 in Fig. 10 and as described in the preceding embodiment. Instead of folding the blank along the bottom edge it can, of course, be folded along one of the upright edges so that the tubular conduit will form a front or rear header, such arrangement being illustrated in Fig. 19. Referring again to Fig. 10, the ends of the tubularconduit 56 are pressed together and welded in the above welding operation. Thereafter'the envelope is put through the same step of expanding the tube and header areas between dies 27 and 28 by the application of an internal fluid pressure, as described of Figures 1 to fi'inclusive. This method is particularly adapted to the use of heavy nickel steel sheets, and when using this material, it is desirable to heat the dies and the sheets. In the formation of the passageways in the metallic envelope, the rear headers 37 and 38 and the front headers 25 and 26 are placed in communication with the ends of the lower tube or passageway 56. This latter tube is in closest proximity to the fire and constitutes a water circulating tube wherein the cold water first receives its high temperature. By forming this passageway in the folding of the blank there are no projecting flanges, rivets or other extraneous metal which might be subject to local overheating because of its immediate proximity to the fire.

This is a desirable construction when using heavy sheets or where riveting is essential. Boiler codes still exist which make riveting a prerequisite in this type of boiler section. In such event the joining lines 42 between tubes and headers are drilled after the expanding operation for receiving rivets 57 as shown in Fig. 12. The marginal weld 22 is reinforced by rows of rivets 57. The partitions or joining lines may be seam welded by the roll-step process and then drilled and riveted; this giving the tightness of joint secured by the weld and the" combined strength of the welded joint and the riveted joint. However, it is within the scope of my invention to dispense entirely with the welding between the circulating tubes and headers by riveting the walls of the envelope together along the partition lines between the tubes and header areas after these tubes and header areas have been formed. A marginal weld 22 around the entire perimeter is desirable in all embodiments of the invention because of the more eli'ective closure against leakage that it a fi'ords.

Feed water connection is made through atubulardrift 4.4 which is forced up into the bottom of the outer rear header 25. The two walls of the section are preferably welded and riveted together on both sides of said drift,

and the draft is preferably welded in the end of the header. The drift may be connected to the mud-drum of the setting in substantially the same manner as described of Fig. 6.

In Figures 15 to 18 inclusive I have shown a modified process involving a slightly different sequence of steps. Each envelope comprises two blanks 58 which are separately formed, as 1 shall now describe. Before any of the welding operations are performed thereon, each blank isinserted between the upper and lower members59 and 61 of a hydraulic or screw press. 'The perimeter of the blank is clamped between these members and a leather gasket 62 is preferably interposed between the blank and the upper clamping member 59 to provide a steam tight seal. The lower clamping member 61 is a forming die into which the blank is adapted to be expanded, having recesses 32 in the face thereof corresponding to the front and rear headers and the inclined circulating tubes. Steam or other fluid under pressure is admitted through pipe into the chamber 63 above the blank 58. This fluid expands the metal down into the recesses 32 to produce the bulged conduit portions 64 shown in Fig. 18. The blank may be heated during this expanding operation. as by applying heat to the lower die member 61. Obviously. when higlr pressure steam is employed as the medium for expanding or shaping the metal the temperature of this steam itself will bring the blank up toa relatively high heat.

After the two opposing blanks have been formed. they are matched as shown in Fig.

18. and thereupon the operation of joining the two blanks together is begun. The perimeters of the sheets are seam welded together and the contacting faces of the sheets between the tubeportions 64 are joined together by welding or riveting, or both,- substantially as described of the two preceding embodiments. The steam connection 23 is welded between the sheets in communication with the upper end of the rear header or with the steam outlet connection 36 during the welding operation.

As shown in Figures 13 and 14, the main group of circulating tubes 40 may be of circular, elliptical, or irregular section. \Yheu the rear header area is thicker than the front header, as shown in Fig. 22, it may be desirable to form the rear ends of the circulating tubes of elliptical section, as shown in Fig.

.13, so as to have these elliptical ends merge gradually into the greater-thickness of the rear header. Each tube is then gradually tapered back into circular section towards the sections in the boiler setting they are preferably staggered vertically, as shown in Figures 13 and 20. so that vertical flue area between the sections will be defiected through a sinuous path to bring the products of combustioninto contact with the under and upper sides of each tube 40. Another method of breaking up the straight line or column flue between the sections is illustrated in Fig. ll. Here each circulating tube 4 0 is of relatively shallow depth on one side and relatively deep on the other. this relation alternating between successive-tubes along the section.

y This is secured by forming relatively shallow depression in one wall of the section or envelope and a relatively deep depression in 1 the other wall of the envelope, to secure a passageway which is somewhat offset with respect to the vertical plane of the envelope. In the setting of the sections. these offset connecting tubes are staggered between sections so that the deeply projecting side of one circulating tube is opposite the shallow side of the circulating tube in the next section, whereby circulating tubes overlap vertically and break up any column effect between the sections.

It will be observed from the foregoing that the two walls of the envelope can be united by seam welding. spot welding or riveting, either singly or in any combination of these. The riveting may be confined to reinforcing the ends of the lines of seam welding, as shown in Fig. 19, or may be extended entirely alongthe lines of joining betweenthe envelope walls, as shown in Fig. 12. \Vhere the riveting is used in conjunction with seam welding along the lines of joining. the seam welding is made sufficiently wide to accommowith any of the processes disclosed in Figures 1 to 18 inclusive, and then riveting the walls of the envelope together along the partition lines between the tubes and conduit areas, instead of welding the partition lines together. The perimetral edges of the section may also be riveted together, but irrespective of whether these edges are riveted or not, I consider it advantageous to weld these edges so of the section. The one essential of the partition joining between the walls of the envelope is that of providing ample strength to prevent any separation of these walls over an extended area. It will be apparent that if a weld lets go internally it merely results in the side of the boiler section bulging outwardlyin this immediate area.

The step of heating the envelope, or the blank thereof in highly heated dies during the expanding operation, such as illustrated in Figures 3 and 4, is desirable when working nickel steel sheets, but is not essential with certain other metals, and metals of relatively light gauge. Also, it is not essential to perform the operation of drawing the tube and header areas of the sheets before the partition lines between the tubes are welded together, but this sequence is preferable, as the distribution of metal is made more uniform.

Figures 19, 20 and 21 illustrate my improved boiler sections in a typical boiler setting. The several steam generating sections are grouped in parallel relationship with the rear headers along the rear wall 78 of the boiler setting. It will be observed that this design of boiler section has a front secondary header 79 and a rear secondary header 81, the former of which connects with an interme diate cluster of circulating tubes 82, and the latter of which connects with the other ends ofthese tubes and with the lowermost circulating tubes 83. Thus the high rate of steam format-ion of the lowermost group of tubes is not interfered with by the upper and less active circulation. Freer steaming results. The several sections have connection with the common feed water header or mud drum 49 in the manner illustrated in Fig. 6. The boiler enclosure is preferably built up of front, side, rear and to walls of sheet metal 84, having a covering 0 heat refractory material 85. Figures 19, 20 and 21 also illustrate just one of the ramifications of my invention in the construction of the feed water preheaters or economizers 87. Each of these preheat ers is constructed of a sheet metallic envelope having upper and lower headers 88 and 89 connected by a plurality of vertical connecting tubes 91. The welding of the margins of this envelope and the expanding of these headers and connecting tubes will be obvious from the preceding description. Separate economizer units are placed across the front wall and both the side walls of the boiler setting, and co-operate with the abutting rear headers of the boiler sections in forming a combustion chamber circumscribed by water containing, heat absorbing walls. The solid heat absorbing surface interposed by each of these economizer sections forms a very effective heat barrier against outward loss of heat through the walls of the boiler setting. The interconnection of these economizer Sections will be obvious to one skilled in the art. The upper end of each boiler section has suitable connection through the coupling 92, connecting with the steam outlet fitting 28 with an individual superheating loop 93. The other end of each of these superheating loops connects through a detachable coupling 94 with a common steam collection drum 95 extending across the top of the boiler setting.

Fig. 22 illustrates the application of my invention to boiler sections of the type used in circular boilers, such as are disclosed in Vins low application Serial No. 344,355, patented 95 March 23, 1926, Patent Number 1,577,549. These boiler sections are illustrated in this .figure in horizontal section, and it will be noted that each section comprises a relatively large outer header 96 and a series of smaller inner headers 97. The envelope is preferably formed by folding a single sheet along a vertical edge of the section, preferably the outer edge, so that the large outer header 96 can be largely produced by the folding operation. This reduces the attenuation of the metal resulting from deep draws-in proximity to the outer header, The inner vertical edge, the other marginal edges and the joining lines between the tubes and the headers are welded together as before described. The circulating tubes 98 taper from the outer header 96 to the group of inner headers 97. The tapered form of the section has particular co-operation with the circular disposition of the sections in a round boiler. For example, the outer headers 96 may be placed in substantially contacting relation to form an outer water wall; one

or more groups of the inner headers 97 may be likewise engaged in abutting relation, particularly where a two pass boiler is desired. The intermediate circulating tubes may be slightl narrower to provideupwardly extending file areas between'the section.

In the operation of any of the preceding embodiments there is no need of maintaining a definitely fixedwater level, but in preference a level will be maintained at about the dash and dot level indicated in Fig. 12. In operation the circulation will be upwards in the front or inner headers, the water cast upwards in these headers being caught in the open mouths of the inclined circulating tubes above the water level and flowing back through these tubes in thin sheets in ideal condition for rapid steam formation. From the rear ends of these tubes the water precipitates down in the rear header areas, from whence it circulates forwardly again through the lower group of circulating tubes. As a result of this circulation, a hydrostatic balance will he maintained in operation with the level higher in the front header areas than in the rear. Any uneven expansion tending to develop because of unequal temperature above and below the water level will be opposed by the strength of the two solid sheets of metal, reinforced by. the expanded tube areas between the. sheets. i

By forming two front header areas, or by forming a separate channel up alongside the front header for the lowermost tubes. a much improved steam freeing action vis obtained. These multiple header areas provide a greater area and more numerous paths for the separation of the steam. The multiple header areas shorten the lengths of the circulating tubes compared to the aggregate areas of these headers. These shorter circulating tubes are an advantage in that they free'the steam generated therein more readily than do longer tubes which tend to blow the en- Gil tire water content of the tube by the trapping of the steam therein.

By the present construction the headers are much more effective as heating surfaces. By splitting up one header into a plurality of channels the aggregate area of header wall exposed to the heat is increased and all particles of the water and steam are brought closer to these heated walls. The present construction also permits of a greater number of sections being inserted in a given fur nace area than with prior sections of the same height and width, because of the fact that the headers are not so thick as in prior constructions, but are preferably of only slightly greater thickness than the tubes so that the sections can be placed closer together. This larger number of sections provides a greater baffling efiecton the products of combustion because it splits up the gases into a larger number of strata. and-the close spacing of the sections permitted by the relatively shallowheaders results in a close spacing of the heating surfaces and narrow gas channels.

The greater area of heating surrace in each section by reason of the marginal fins. the in.- tervening web portion between the tubes and thesectionalized construction of the headers result in a higher heat transfer capacity in each section, and the larger number of sections give a considerably greater total heating area for the entire boiler.

I do not intend to be limited to the particulars herein shown and described, as it will be obvious that my invention may be practiced in different ways and by difierent means within the general scope of the teaching herein disclosed.

I claim: a

1. A boiler section constructed of two sheet metal walls andcomprising a plurality of circulating tubes, a pair of inner headers com- .municating with said tubes, and a pair of outer headers communicating with said tubes.

2. A boiler section constructed of two sheet metal walls and comprising a plurality of circulating tubes. a first inner header communicating with said tubes. :1 second inner header disposed substantially in the plane of said tubes and said first inner header and communicating with said first inner header, a first outer header communicating with said tubes, and a second outer hhder disposed substantially in the plane of said tubes and said first outer header.

In witness whereof, I hereunto subscribe my name this 14th day of November, 1923.


Referenced by
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US2507094 *Sep 8, 1944May 9, 1950Stewart Warner CorpMethod of and apparatus for making spiral heat exchangers
US2515804 *Mar 18, 1948Jul 18, 1950Plastite IncInflatable toy
US2582358 *Jun 8, 1948Jan 15, 1952Northrop Aircraft IncMethod of producing stiffened skin panel
US3018543 *Jul 13, 1955Jan 30, 1962Stolle CorpChambered sheet metal laminates and method of making
US3512239 *Apr 19, 1967May 19, 1970Rosenblad CorpMethod of forming dimpled plate heat exchanger elements by the use of hydrostatic pressure
US3537165 *Jun 26, 1968Nov 3, 1970Air PreheaterMethod of making a plate-type heat exchanger
US5230870 *May 26, 1992Jul 27, 1993Johnson Arthur FMethod for converting noxious pollutants from flue gas into merchantable by-products
US5344617 *Jul 26, 1993Sep 6, 1994Johnson Arthur FApparatus for converting noxious pollutants from flue gas into merchantable by-products
DE1104917B *Dec 8, 1955Apr 20, 1961Perry J RieppelVerfahren zur Herstellung von Hohlkoerpern durch Blaehen geschichteter Metallteile
DE2007400A1 *Feb 12, 1970Aug 19, 1971Rosenblad CorpTitle not available
EP2607832A1 *Dec 6, 2012Jun 26, 2013Thesan S.p.A.Connection device for roll-bond panel heat exchanger
U.S. Classification122/265, 122/290, 29/890.51, 122/221, 122/360, 122/208, 122/DIG.160, 122/223
International ClassificationF28F3/00, B21D26/02, F28F3/14, F22B37/10, B23P15/26, B21D53/04
Cooperative ClassificationY10S122/16, F23B2700/01, F28F3/14
European ClassificationF28F3/14