US2800113A - Steam generator - Google Patents

Description

y l957 e. w. KESSLER ETAL 2,800,113 STEAM GENERATOR Filed March 16, 1948 w 7 sham-sheet 1 I r v INVENTORS George MZ/(ess/erl y l/fl/V/VES b. flmmplv ATTORNEY y 3, 1957 G. w. KESSLER ETAL STEAM GENERATOR Filed March 16. 1948 7 Sheets-Sheet 2 ATTORNEY July 23, 1957 G. w. K'ESSLER L 7 2,800,113

. STEAM GENERATOR v Filed larch 16, 1948 E 7 Sheets-Sheet :5

INVENTORS' ,0, GeoryeW/(ex/er 9" By mun/5 Aflnmon I ATTORNEY I y 1957 G. w. KESSLER ET AL 2,800,113

STEAM GENERATOR Filed March 16, 1948 r w 5 Mm.Ke 0 mW WW. W 6 w m 3 z ww w 6 7 m v 4 (fall/M0153 l2. IIMMON ATTORNEY July 23, 1957' G. w. KESSLER ETAL 2,800,113

STEAM GENERATOR Filed March 15, 1948 32 is; I I s Fig. 10 429 INVENTQRSY 6:?0/yeW/(ess/er v 8 F y 9 my: liflnmou ATTORNEY y 1957 G. w. KESSLER EI'AL 2,800,113

STEAM GENERATOR Filed March 16, 1948 7 Sheets-Sheet 6 INVENTORS N J i H AH N w w W A 6M. M M 7, M? fi H United States Patent STEAM GENERATOR George W. Kessler, Bronx, N. Y., and Johannes H. Ammon, Akron, Ohio, assignors to The Babcock & Wilcox Company, Rockleigh, N. 1., a corporation of New Jersey Application March 16, 1948, Serial No. 15,178

13 Claims. (Cl. 122-235) This invention relates to water tube steam generators, and more particularly, to a steam generator in which the heat absorbing and fluid heating surfaces are formed by a number of long circuit tubes (i. e. as long as 600), forming unbroken and unbranched flow paths for water or other vaporizable liquid, from a common liquid inlet to a common liquid and vapor outlet. Some of these tubes have parts constituting the vapor generating wall tubes of a furnace from which gases pass over a convection section. Others of the tubes form convector units of banks of spaced tubes over which the gases pass in the convection section, and all of the tubes leading from a common liquid inlet have their parts so arranged in different heat absorption zones that the heat inputs to the tubes are substantially of the same order, at a given capacity of the generator.

The vapor generator of the invention is so constructed and arranged that it is capable of effective operation under a wide range of output conditions, particularly avoiding limitations of previous steam generators on the low load side of the operating range.

The vapor generator of the invention is characterized by a central furnace which is preferably axially fired for vertical movement of gases therein. The furnace, of polygonal horizontal section, preferably has a number of sides greater than 4 so that it approaches a circular cross section. This eliminates the formation of right angle bends in the furnace Wall tubes and promotes a high degree of thermal effectiveness in the installation by permitting the encompassing of the furnace by the heat absorbing units of each of several convection segments disposed in a gas pass space formed between the furnace and an inner casing. The tubular components of the various convection segments around the furnace are constructed and arranged as relatively small convector units of banks of spaced tubes independently supported, and with some of them of like construction to facilitate maintenance involving the removal and repair of the separate units. Cooperating with this construction, the inner casing is provided with removable casing sections at the positions of the convector units, and an outer casing, spaced from the inner casing, is similarly constructed.

It is an object of the invention to provide the above indicated construction in such a manner that a minimum of restraint upon one part or section of the circuit tubes forming the heat absorbing surfaces is imposed by an adjoining part or section.

It is also an object of the invention toprovide a vapor generator which has increased capacity relative to its weight and space occupied by it.

A further object of the invention is to provide a forced flow vapor generator, which is particularly adapted for operation at super-atmospheric heating gas pressure, and in which the several sections include an econornlzer, a vapor generating section, and a superheating section, all arranged in a novel combination, with various new features of construction, all contributing to the major objective of a reliable and effective high capacity vapor generating unit the operation of which is characterized by a high availability factor, low maintenance costs, and a Wide capacity range.

A more specific object of the invention is the provision of a central axially fired combustion chamber or furnace surrounded by separate segments of a convection section of forced flow water tubes arranged in such a manner as to minimize tube stresses induced by means maintaining the tubes in their operative positions, the arrangement of these components and the construction of the furnace being such that it can be advantageously adapted to the cyclonic firing of crushed solid fuel.

A major feature of the construction of the vapor generator of the present invention, contributing to the min imization of tube stresses-is the arrangement whereby the exposed heat absorbing tube lengths of each independent circuit or flow path are so positioned with respect to the different heating gas temperature zones that the portions of the flow near their inlet ends are subject to high inputs of radiant heat, while the portions adjacent the discharge ends of the flow path tubes are located in convection heat absorbing zones where the gas temperatures are such that much lower rates of heat input occur. The tubes of the circuits are so positioned with respect to the heating zones that no leading portion of a tube length receives heat at a low rate while a portionnearer its outlet end receives heat at a substantially higher rate.

The invention will be described by reference to the accompanying drawings in which an operative embodiment is shown, and other objects of the invention will appear as the description proceeds.

In the drawings:

Fig. 1 is a vertical section of the illustrativevapor generator, on the section line 1-1-of Fig. 2;

Fig. 2 is a composite multiple plane plan section with its correspondingly indicated .parts on the section lines A-A, BB, C-C, D-D, and BE of.Fig. 1;

Fig. 3 is a partial vertical section of-the left hand part of Fig. 1, on an enlarged scale;

Fig. 4 is a partial plan at a level near the top of the furnace on line G-G (Fig. 1), with the casing and other parts omitted to show parts of the tube circuits;

Fig. 5 is a plan of the vapor generator; 7

Fig. 6 is a side elevation, from the lower side of Fig. 5;

Fig. 7 is a plan of the structure of one of the several piers;

Fig. 8 is a vertical section through a pier nose, on the line 8-8 of Fig. 7; p

Fig. 9 is a vertical section on the line 9-9 of Fig. 8 showing the tubes of a pier in elevation;

Fig. 10 is a detail vertical section on the line 10-10 of Fig. 7, showing the structure at the base of one of the piers;

Fig. 11 is a partial exterior elevation of a part of the furnace wall showing the tube anchoring device;

Fig. 12 is a vertical section on line 12'12 of Fig. 11;

Fig. 13 is a partial horizontal section on the plane of line 13-13 of Fig. 14;

Fig. 14 is a vertical section on line 1414 of Fig. 13 showing convector unit 34 on an enlarged scale;

Fig. 15 is a detailed vertical section on line 1515 of Figs. 14 and 13;

Fig. 16 is a detail elevation from the position 16-16 of Fig. 17 of the superheater tube supports at the base of convector unit 34;

17 is a vertical section on line 17-17 of Fig. 16

Fig. 18 is a view in the nature of a diagrammatic plan of the superheaters, showing their series connections in pairs with one superheater of each pair operating on the counterfiow principle, and the other on the parallel flow principle; and

Fig. 19 is a section of one of the resistor constructions leading from the lower headers.

In Figs. 1 and 2 of the drawings there is shown a central furnace down-fired by burners such as 11 and 12. The furnace is hexagonal in horizontal section, having the sides, 13 to 18, inclusive. The walls of the furnace terminate at a position above the base of the installation, provrding a plurality of separated radial extensions of a central furnace space, arranged circumferentially so that gases may pass radially outwardly (as indicated by the curved arrows 21 and 24 of Fig. 1) into the separate upright gas passes 27 to 32 inclusive, of the segments of the convection section surrounding the furnace. In this space the separated streams of gases pass upwardly over successively arranged and superposed small convec tor units (such as 33 to inclusive, Figs. 1 and 3), corresponding units of the different passes being of similar, or identical construction. Each of these vertical arrangements of convector units may be considered as a segment of the entire convection section.

The generally annular gas pass space for the convec tion section is delineated by the furnace side walls and by an inner boiler casing 41. The latter involves removable sections or panels such as 42 to 64 inclusive, aligned radially with the positions of the various convector units. Spaced outwardly of the inner .casing is an outer casing similarly having a number of removable panels such as 71 to 78 inclusive (Figs. 1 and 2) through which access is gained to the inner casing and the convector units.

At the base of the installation and in the zone adjacent the radial furnace extensions or furnace gas exits there is provided a number of radially disposed piers to inclusive formed, in part, by some of the independent flow path tubes. These piers are circumferentially spaced as indicated in Fig. 2, and they act in conjunction with the wall tubes of the furnace to afiord the separate radial furnace extensions from which gases flow to the inlets of the six separate convection gas passes 27 to 32 inclusive of the segments of the convection section, to provide for the upflow of furnace gases at least to positions near the tops of the superheater sections such as and111. As the gases turn upwardly in each of such separate passes they first contact the spaced tubes of the screen sections constituting the initial convector units such as 33 and 37, there being one of such initial units in each of the six segments of the convection section. The piers have full length upward extensions of their refractory walls extending at least to the upper limits of the superheaters. The convector units above the superheaters are indicated generally at 34 to 36 inclusive and 38 to 40 inclusive. These are steam generating units and they are disposed in a substantially annular arrangement about the furnace and above the level of the superheaters.

The gases passing upwardly and beyond the top convector units such as 36 are concentrated in two upwardly extending gas passes 118 and 119 within the inner and outer economizer casings 120 to 123 inclusive, disposed, above the roof of the installation. The economizer sections 124 and 125, within these casings, are formed by banks of spaced tube sections connected at their ends for the series flow of a vaporizable liquidtherethrough. Such liquid is supplied to the inlet of each economizer by a feed water pump (Fig. ,5) having appropriate tubular connections 131135, and from the liquid outlet of each economizer section the liquid flows through appropriate tubular connections to the lower (or resistor) headers and 151 which are disposed at opposite sides of the installation. A feedwater, or economizer connection to the header 150 is shown in Fig. 2 at 15%. The economizer sections are constructed and arranged to facilitate access to the interposed oil burners for ignition, and other purposes. There may also be a' number of economizer sections corresponding to the number of convection section segments.

The tubes leading from each of the headers 150 and 151 present one half of the total number of unbroken vapor generating flow paths of the installation. At the left hand side of Fig. 2 the header 150 is shown as having 12 of the tubes of such flow paths connected there to. The inlet portions of these tubes are upright as in dicated at 152 (Fig. 1) and they are connected to separate tubular resistor constructions 171 to 182 extending horizontally and at right angles to the header 150. These resistor constructions provide for access to the inlets of the associated circuit tubes for the installation of different tubular flow resistance elements separately effective upon the tubes of different flow paths for the purpose of correcting inequalities in the distribution of flow. These resistors are of such a construction as that illustrated in Fig. 19 and are covered in a separate patent application (Ser. No. 51,022, filed September 24, 1948, now Patent No. 2,664,109) as the invention of R. F. lager. Each resistor includes an internal cartridge construction 800 slidably fitting within the outer tube 302 and having internal orifice disks $03-$67 and other parts 808811. The cartridge construction is removable through the outer tube opening closed by the closure construction 812818. Such removal is necessary when a resistor cartridge is to be replaced by one of greater or less flow resistance.

The tube circuit flow paths initially leading through the convector screen sections Some of the tubes of the independent flow paths leading from the header 150 have portions leading upwardly to the different levels of the successively superposed fiat coils of screen convector units in gas passes 2732, one of such upwardly leading parts being shown in Fig. l at 199. In the illustrative generator the flow path tubes extending upwardly from resistor constructions 174, 175, and 179 lead to the initial fiat coils of three similarly arranged and constructed screen convector units one of which is indicated in its entirety at 33. This unit consists of a series of flat coils 200-204, inclusive, such as are indicated in Figs. 1 and 3. Each fiat coil is made up of a series of spaced parallel tube lengths such as 210-217, inclusive, Fig. 2, serially connected at their ends by return bend tubular portions such as 220-226, the inner radius of each tubular bend being greater than the spacing of the parallel tube lengths connected by the bend. Each individual return bend portion may be regarded as a section constituting more than a semicircle, with one of its associated tube lengths (such as 210) tangentially related to the bend circle, and the other (such as 211) so related to the bend that its extension would constitute a chord of the circle of the bend. In the vertically successive flat coils of the convector units this arrangement of return bends relative to their immediate associated tube lengths is reversed, facilitating the stacking of the successive return bends one upon another in a convector unit, and also providing for the uniform staggered arrangement of the individual tube lengths in each convector unit- Thus the superposed flat coils of the convection screen 33 are supported one from the other by the contacting superposed return bends which are in alignment-and in contact through an arc of at least 180.

These return bends may be termed re-entrant return bends by way of distinguishing them from the U-shaped return bends of the prior art.

As an example of the disposition of the circuit tubes of the separate flow paths in difierent temperature zones from inlet to outlet of each tube, the tube having the screen inlet portion 199 (the lower left hand part of Figs. 1 and '3) successively forms the first two fiat coils 200 and 201 of the screen section 33 and then the fourth flat coil 203 of that section (reading upwardly in Fig. 3). From the position of the outlet of this coil this tube is bent as indicated at 198 and then extends upwardly out of the gas pass 27 and past the superheater section 110 (and at a position corresponding to position 205, alongside gas pass 30) to the level of the first flat coil 241 at the bottom of the convector unit 34 (Fig. 3) immediately above the superheater section 110 (shown in Fig. 3, and in the lower left hand part of Fig. 1). It then forms the flat coil 241 at this position. It thereafter extends upwardly and forms the succeeding flat coils 245, 249, 250 and 254, which are the fifth, ninth, tenth, and fourteenth fiat coils of convector unit 34. From this position this tube extends upward past coils 254 and 255, then radially as at 256 and 257, and then again upward to 258. It then similarly and successively forms the first, fifth, ninth, tenth, and fourteenth flat coils 261, 265, 269, 270 and 274 of the next superposed convector section 35. Beyond this position the tube has a portion 279 extending radially outwardly through the inner casing 41. It then forms the tubular connections such as 276 and 277 (Fig. to one of the tangential inlets 281 and 284 of one of the centrifugal steam and water separators 278 and 280.

The tube circuit flow paths initially leading through the pier tubes Referring now to the independent flow paths the circuit tubes of which form the heat absorbing surfaces of the piers 90-95, at the lower part of the furnace, there are six of such tubes leading from the separate resistor constructions 171, 173, 176, 178, 180 and 182. They are the first, third, sixth, eighth, tenth, and twelfth resistor constructions leading from the header 150 shown in the left hand part of Fig. 2. One of the tubes leads from the sixth resistor construction 176 along the removable wall section 65 of the inner casing section for the upright gas pass 27. At the end of this wall section, this tube continues inwardly of the installation at 67 in a somewhat radial direction through the wall section 65 of this gas pass. It is then bent at a right angle for extension horizontally along the inner surface of wall section 65, as indicated at 68. At the end of this wall section it is again bent at 90 to form the section 70' extending horizontally along the refractory wall of pier 90 (corresponding to the pier wall section 335 of pier 91). It then extends radially inwardly and around the nose 90' of this pier and along the opposite substantially radial wall 90" of the nose of this pier, and then outwardly along the right hand pier wall 97. It then similarly continues substantially horizontally along the various similar gas pass walls and walls of piers 91-95, arranged in succession around the furnace. After completing the circuit of the these pier walls and gas pass walls, the tube forming this particular flow path continues upwardly to the position indicated at 98 (see the left hand side of Fig. 2 above the indication of gas pass 27) where it forms the uppermost flat coil 204 of the screen convector unit 33 at the lower left hand part of Fig. 1. From that position, it continues upwardly past the superheater 110 and successively forms the second, sixth, seventh, eleventh and fifteenth coils 242, 246, 247, 251, and 255, of the convector unit 34 immediately above the superheater section 110. It then continues upwardly exteriorly of convector unit 34, and through a radially extending section 299 to the second coil 262 from the bottom of the next superposed convector unit 35 to form the second, sixth, seventh, eleventh, and fifteenth coils 262, 266, 267, 271 and 275 (reading upwardly in Fig. 3) of that section and then extends radially outwardly at 316 through the casings 41 and 70 and to one of tangential inlets 281 and 284 of one of the centrifugal steam and water separators 278 and 280.

It will be seen by reference to Figs. 1, 2, and 3, that the heat absorbing sides of each pier are formed by twelve superposed and contiguous coils in wall forming relation one upon another, six of these tubular coils leading from the lower header 150, indicated in the left hand side of Fig. 2, and the remaining six leading from the similar header 151 at the opposite side of the installation. Each of these pier coils is similar to the pier forming coil already described. Each segment of the convection section (and its gas pass) has two pier tube circuits represented by some of its flat coils. One of such circuits has been referred to as including the coil 204 of the screen section 33. A similar circuit includes the coil 202 (Fig. 3). Certain of the coils of convector units 34 and 35 are also involved.

The superposed contiguous tubes of the pier coils are maintained in vertical wall formation by columns such as 320 (Figs. 7, 8 and 9) each disposed within the nose of a corresponding pier. Each column is supported from the base of the installation, and preferably directly above one of the radially extending beams 321 to 326, inclusive, which are indicated in Fig. 2. Each pier construction is also completed by inwardly converging casing walls, such as 331 and 332, including the upright supports 333 and the plate sections 334. Between each of these sections and its associated pier tubes are portions of refractory strata such as 335 and 336, similar material also extending into each pier nose as indicated at 338 and 339 (Fig. 2).

The construction and arrangement of the illustrative installation at the positions of the piers is illustrated in considerable detail in Figs. 7 to 10, inclusive. In Fig. 7 the arrangement of the tubes and other structural elements of the pier 91 are shown. This construction is centered about a vertical plane including the longitudinal axis of the beam 321. To the latter are secured, in their proper angular relations, the horizontal base supports 700 and 701, in line with and supporting the associated sections of the inner casing construction. From positions along these horizontal members and spaced from the column 405 are the upright structural members 704 and 705 disposed at'the outer corners of the inner casing constructions adjacent the pertinent convection segments. From these positions along the base members 700 and 701, inwardly converging structural members 702 and 703 are disposed at the base of the walls at the adjacent ends of the pertinent gas pass constructions for the two adjacent convection segments. Directly above these members 702 and 703, there are disposed the pertinent inner casing segments and between the vertical planes of the vertical surfaces of these members are the metallic panels of those casing sections. Between these vertical planes and the vertical planes of the superposed pier tube sections such as 706 and 707, are disposed the strata of thermal insulation material or referred to.

At the position of the pier tube sections 706 and 707, there are the pier tube walls as indicated at R and S in Fig. 8, formed by the, superposed contiguous tube sections. These walls are supported by pedestals 710 and 711 secured to the column 320, and the successive tube sections may be held in wall forming alignment by such devices as those shown in Figs. 11 and 12.

Fig. 10 shows a pedestal plate 720 supporting the column 722 along the tubes of the wall R at the position indicated in Fig. 7. Also supported by the plate 720 is the upright 724 on top of which rests a pad 726 supporting the tubes of the pier wall.

From an inspection of Fig. 2, it will be noted that the return bend ends of the flat coils forming each screen convector unit immediately above the pier tubes extend beyond the walls formed by the superposed pier tubes at the opposite sides of the pertinent gas pass and to positions where they almost contact the refractory walls of the piers and of the pertinent gas pass extending upwardly beyond the uppermost pier tubes. This construction permits the coils of these convector units to rest upon the pier tubes and be supported thereby.

The circuit tubes of the flow paths initially leading through the furnace wall tube sections refactory material above Referring next to the tubes forming the independent flow paths of the furnace walls, three of these tubes lead tions 172, 177 'and 181 connected to the header 150,

reading upwardly from the left hand part of Fig. 2. Thus, with a similar construction and arrangement for the similar resistor header 151 at the opposite side of the installation there is a total of six furnace wall tubes of the independent flow paths leading from the lower headers as'a common inlet. An appropriate equalizing connection between the headers 150 and 151 provides for such a common inlet construction.

As an example of these furnace wall tube flow paths one tube will be traced, beginning at the seventh resistor construction 177 (Fig. 2). A leading portion 340 (Fig. 2), of this tube is parallel with the axis of the header 150. The tube then turns inwardly at right angles as indicated at 341 and extends in a direction along the wall of the gas pass 27 (as it is shown in Fig. 2) to an intermediate position 342, from which it extends substantially radially, as indicated at 343, toward the furnace wall 13. At 344, a position in the plane of wall 13, the tube is bent to extend, as indicated at 345, in the plane of that wall and then over the nose of the pier 90, and thence somewhat helically in the successive furnace walls 13 to 18, inclusive, until it reaches a position at the top of the furnace, as indicated, for example, by the top tube outlet connection 350 at the left hand upper corner of the furnace, (Fig. '1). From that position it extends radially outwardly at 300 and forms the successive flat coils 301-307, inclusive, of the uppermost convector unit 36, within the inner boiler casing. From the top of that unit it extends radially outwardly of the installation at 352 and through the inner and outer casings 41 and 70 and to one of the tangential inlets of one of the centrifugal steam and water separators 278 and 280. Thus, in the walls of the illustrative furnace there are six circuit tubes in superposed and contiguous relation disposed somewhat in the form of helical threads proceeding upwardly from the bottom, around the furnace to the top of the furnace wall and then leading through and from an upper convector unit from which steam and water flow to a centrifugal separator.

The superheater units The superheater units such as 110 and 111 (and 112 and 113, Fig. 2) are disposed above the screen convection units 33 and 37, the number of the superheater units corresponding to the number of convection section segments and separate gas passes therefor leading from the furnace extensions between the piers 90--95. It will also be noted froman inspection of Fig. 2 that the pairs of opposite side walls such as 355 and 356, 357 and 358 of the gas passes at the positions of the superheater units are parallel throughout their lengths.

The superheater units consist of banks of tubes of relatively short length formed by vertically flat coils of return bend tubes. The diameters of the return bends of. these coils are greater than spacing of the tube lengths immediately connected thereto, and the detail construction of each coil is generally similar to the construction of the converter coils previously described. Several of these vertically fiat coils are involved in each superheater unit and the coils are parallel to each other as indicated in Fig. 2. With this construction, the coils at the end of the superheater have their tube lengths disposed at a spacing from the pertinent superheater gas pass walls (such as 355-358) corresponding to the spacing of the coils. The superheaters are supported, and the spacing of their parallel tube lengths is maintained by hanger strap structures such as indicated at 360 and 362 and other associated elements which will be described in detail below. With this construction the gas flow passages through the Zones of the. superheaters are uniform. If they were otherwise, there would be non-uniform distribution of the high temperature gases and consequent damage by reason of theoverheatingof .some of the" across the associated gas pass and has its top tube length joined to a superheater outlet header 365 secured externally of the gas pass at the position of a removable inner casing section 42, Fig.3. Between the removable inner casing section 42' and the similar section 62 about the inlet header 366 is another removable casing section 63, this construction permitting the removal of an entire superheater unit for maintenance purposes.

The superheaters receive steam from the centrifugal steam and water separators 278 and 280 and they can effectively operate to raise the temperature of the steam to a value in excess of 1000 F. At such superheats, high gas temperatures are involved, the temperatures being so high as to damage the metal of the superheater tubes by overheating unless adequate limiting factors are involved. In the present installation, the danger of overheating the superheater tubes at a high superheat is pre' vented by a plurality of co-acting provisions one of which is the provision for a high rate of mass flow of steam through the tubes. Another limiting factor upon the metal temperature of the tubes is the construction and arrangement of the superheaters to the end that the lengths of 'superheat coils subject to the highest steam temperatures are subject to the lowest gas temperatures. These results are achieved by an arrangement in which the superheaters of the different segments of the convection section are'series connected in pairs in such a manner that the first superheater of each pair operates upon the counterflow principle and the second superheater of each pair operates on the parallel flow principle.

The arrangement of the superheaters in pairs is indicated somewhat diagrammatically in Fig. 18 of the drawings. Three pairs of superheater tubes are illustrated. The superheaters K and K constitute one pair; M and M another pair; and the third pair being constituted by the superheaters Land L. The superheaters K, M, and L may be regarded as inlet superheaters, each of them receiving steam directly from the one of the steam and water separators 278 and 280, and discharging that steam through an appropriate crossover pipe to one of the associated superheaters K','L, and M. One of the inlet superheaters such as K may be regarded as equivalent to the superheater shown at 111 in Fig. 1 and the directly opposite superheater M may be regarded as the equivalent of the superheater of the same figure.

Saturated steam from the top of the separator 280 is conducted through the tube 377 to the inlet header of the superheater K. This header corresponds to the upper header of the superheater 111. From that header the steam passes through the superheater coils in generally countercurrent relation to the gas flow to the superheater outlet header corresponding to the lower header of the superheater 111, shown in Fig. 1. From this header, steam flows through a crossover tube 9%, to the lower header of the superheater K. Thence it passes generally upwardly in parallel relation to the gas flow to the upper header of the superheater. From this header it passes through a tube 902 to a main superheater outlet 984 which is in the nature of an upright header.

The inlet superheater L receives its steam from the separators 278 and 280 through an equalizer tube 906 and a conduit including the tubular sections such as 375, 376, and 993, part of the conduit for this steam flow path being disposed beneath the tube 377 as it is indicated in Fig. 18. After passing through the coils of the super- ..hcater L in countercurrent relationto gas flow, the steam thereto.

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passes'through a crossover tube 910 connecting the outlet header of the superheater L to the inlet header of the superheater L. The steam then flows in parallel relation to gas flow through the superheater L. From the outlet header of this superheater, the stem flows through an outlet tube 912 to the main superheater outlet 904, parts of the tube 912 being disposed beneath other tubular sections indicated in the drawing.

Steam to be superheated by the superheaters M and M flows from the top of the steam and water separator 278 through a conduit indicated at 915 to the upper or inlet header of the superheater M. After flowing in countercurrent relation to the gas through the coils of this superheater, the steam flows through a crossover tube 916 connecting the outlet header of the superheater M to the inlet header at the lower part of the superheater M. From the header to the top of the superheater M, the steam flows through an outlet tube 917 directly to the main outlet 904.

In connection with the above described arrangement of the superheaters in pairs, and the steam flow to and through the connected superheaters L and L is intended to be indicated by the arrows 921 to 926, inclusive, and the similar steam flow through the pair of superheaters K and K is intended to be indicated by the arrows 930 to 933, inclusive. 7

Considering the superheater 110 (Fig. 1) as one of the outlet superheaters, it will be seen that the gases contacting the upper parts of the superheater coils have had their temperature lowered by heat transfer to the preceding parts of these coils. Hence, the gases contacting the coil tube lengths conducting superheated steam at its highest temperature .have the lowest gas temperature, this factor being of considerable importance in the prevention of damage to superheater tubes by over-heating. Another preventitive factor, increased steam mass flow, is afiorded by reason of the series connections of the superheaters in pairs.

The steam and water separators 278 and 280 from which the superheaters receive their steam are cylindrical pressure vessels with their major axes vertically disposed. Two of such separators are shown, each separator receiving steam and water from one-half of the entire number of the tube circuits constituting the independent vapor generating flow paths of the installation. They have their outlet parts such as 277, 287-298 (Fig. entering tangential inlet structures such as 281-286 at the top of the separator. Similar outlet parts 600618 enter the inlet structures 284-286 of the separator 278 on the other side of the installation. This sets up a whirling motion within the circular chamber in a separator. The steam is thereby separated from the water, the former rising to the top of the separator whence it flows to the superheater inlet headers.

Water flows from the bottom of each steam and water separator through appropriate connections such as 380-382 to the inlet of a recirculating pump 390 directly driven by the motor 391. Disposed upon, the same shaft is the feed water pump 130. From the outlet of the recirculating pump water flows to the lower resistor headers 150 and 151, this arrangement, and the control of the installation, being such that, as boiler load decreases, a higher percentage of the liquid within the system is recirculated. This has the highly advantageous effect of eliminating such low load restrictions as have been applied to prior art generators.

The casing constructions Returning now to the description of the casing constructions disposed around the furnace andthe convector units, attention is invited to the upper left hand part of Fig. 3. Here, several sections or panels of the casing are shown, each consisting of a metallic plate or plates with a metal sheathed inner refractory lining secured Each section or panel is removably secured to adjoining sections by flanges formed by extensions of the plate arranged to overlap adjacent sections. For example, between the outlet tube section 352 of the upper convector unit 36 and the fluid flow path outlets 279 and 316 at the top of the next subjacent convector unit 35 there is a casing section 47 consisting of'a plate 392 with an inner lining 393 of thermal insulation secured thereto and sheathed by sheet metal 393'. This plate has upper and lower extensions 394 and 395 by means to which this casing panel or section is secured to the adjacent superposed casing section 48 and the adjacent and similarly constructed lower casing section 46. There is a similar casing panel 49 (Fig. 1) above the top of the uppermost convector unit 36. When the two panels 47 and 49 are removed, as by the release of pertinent holding devices, such as welds or bolts, the intervening casing section 48 around the flow path outlet tubes such as 352 may be removed. Similarly, the casing section around the next lowermost flow path tubular outlets such as 279 and 316 may be removed after the removal of the next lower casing panel 45. The latter is constructed and arranged similar to that of the panel 47, described above.

When the adjacent outer casing sections '73 and 74 have been removed, the coils of the uppermost convector units 35 and 36 are then accessible for inspection, or other maintenance purposes.

Due to the polygonal arrangement of segments of the convection section about the central furnace 10, the problems involved in the construction of the inner casing, and in the removal and replacement of the casing components during the maintenance of the convection units are distinctly simplified. Maintenance costs are also thereby minimized. i

The outer casing 70 is of a construction of less Weight than that of the inner casing and its separate sections or panels are of greater area. The lining of these sections is also of thinner, and lighter weight insulating material.

The outer casing is preferably circular as indicated by the drawings, its various panels such as indicated at 71-82 in Figs. 1 and 2 are likewise metallic casing panels supported by the columns 401 to 406 which are in turn supported by the radial beams 321 to 326 at the base of the installation. The horizontal supports for the casing panels are indicated at vertically spaced positions at 410 to 415, in Fig. l. i

The top of the outer casing is closed by a roof 417 of sectionalized metal and insulation construction and beneath the roof there is a furnace roof 418 of construction somewhat similar to the inner casing construction described above. As indicated in Fig. 1, the furnace roof includes burner sections involving upper sheet metal elements such as 420 and 421 secured to supports such as 422 and 423, each roof section having a next lower stratum 424 of thermal installation secured thereto around the burner openings. Beneath this stratum is a thicker layer 425 of non-metallic refractory material of higher heat resistance.

At the bottom of the installation and between the opposite side sections 42 and 51 of the inner casing are three strata-427, 428 and 429 of insulating refractory material resting upon steel work exemplified by the elements 430 to 433, associated with the main radial beams 321-326.

Referring to Fig. 4, showing the construction of the installation in partial plan, or horizontal section, near the top of the furnace, it will be noted that the columns such as 404-406 disposed between the inner and outer casings, extend outwardly from refractory bodies 440, 441, and 442, of triangular horizontal section. These bodies are enclosed by metallic plate components 443, 444, and 445 which also form seats for the removable inner casing panels, such as 446 and 447, at a level near the top of the convector unit 35.

These bodies may be considered as upward refractory The means tying together the furnace wall tubes Referring now to the furnace wall tubes, it is important that these tubes be maintained inwall formation. The specific structure provided for this purpose, is shown in Figs. 11 and 12. There are here illustrated two furnace wall tubes 450 and 451, one directly above the other. The upper tube has metallic sleeves or hollow cylinders, such as the sleeve 452, welded to it at spaced positions distributed circumferentially around the furnace, such a weld being shown at 453. These sleeves or hollow cylinders are disposed so that they are in contact with, or in close relationship to, both upper and lower tubes 450 and 451. At positions likewise similarly spaced about the furnace, the lower tube 451 has similarly Welded to it sleeves or hollow cylinders, such as 454, spaced from the sleeves or cylinders 452 so as to allow for relative longitudinal movementof the tubes due to the thermal changes. The adjacent sleeves or hollow cylinders of each pair (such as 452 and 454), have extending through them a cylindrical pin 455 which has sufiicient tolerance or loose fit within the hollow cylinders to minimize stresses which would otherwise be imposed by excessive restrictions of the tubes. Each pin is held in place by a weld securing it to one of the associated sleeves or cylinders. Such a weld is indicated at 456.

It will be understood, of course, that such devices for tying the adjacent tubes together are distributed throughout the height and circumference of the furnace. It will be also understood'that these constructions are placed upon the outer sides of the furnace walls.

The convector section tube supports It has been indicated above that the superheater tubes are supported by hangers, and that the vertical spacing of the tubes is maintained in the same manner. The construction used for this purpose is also involved in the support of the tubes of the convector units immediately above the superheater sections, and these constructions will therefore be described together. They are specifically shown in Figs. l3l7, inclusive. Considering the convector unit 34 immediately above the superheater section 110, there are two vertically spaced and horizontal angles 460 and 461 (Fig. 14) secured at their ends to the columns 401 and 4136 (Fig. 13) at the exterior of the inner casing. Secured between these two horizontally and vertically spaced angles there are two pairs of spaced channels 462-465, the pairs being located toward the opposite ends of the tube bank of the convector unit. The channels are secured at their outer ends to the exterior beam or angle 461 as indicated in plan Fig. 13 and the inner ends of the channels rest upon lugs such as 464' and 465 (Fig. 15 welded to the wide upright bars 466470 extending vertically along the exterior sides of the furnace wall tubes and immediately adjacent and secured thereto. The upper ends of these bars are preferably fixed to the steel work such as parts 471472 (Fig. 1) extending from the top of the installation to a position between the upper part of the furnace and the convector sections 35 and 36 adjacent thereto. The inner ends of the horizontal channels 462-465 are secured to the bars 466, 467, 469, and 470 as by welding, at positions such as those indicated in Figs. 13 and 14. The channel members of each pair, as indicated in detail vertical section Fig. 15 and in plan Fig. 13 of the drawings, have their grooves or channels opening toward each other, and, distributed at spaced positions across the convector gas pass and throughout the lengths of members 462, 463, 464, and 465, are pins 471486, resting within the channels. Before each pin is placed in its operative position between the channels it is threaded through holes in the upper ends of tube strap links such as 490 and 491 (Fig. 15), the links of each pair normally depending between the top tube lengths such as 496 and 497 of alternatefiat coils of the convector 'section;-'as indicated in vertical section Fig. 14. The links of eachpa'ir are Welded or otherwise secured at their lower ends to upright tube straps such as 492 and 493,-these tube straps depending therefrom and extending through the bank of convector tubes with the opposite straps extending-aroundthe opposite sides of successive tubes and secured together between vertically adjacent tubes. This construction supports the lowermost flat coil 241 of the convector unit 34, and alternate coils above it, Each ,of 'these' hanger supported coils directly supports the coil immediately above it.

The superheater tube, supports.

Below the convector unit 34 the superheater section has its outlet header 365 supportedby the associated steel work at the positionof removable casing section 42' of the inner casing. Thus, with the upper tube lengths of the superheater coils secured to this header, the subjacent outer end portions of the successive return bends of the vertically flat superheater coils are directly supported by strap constructions 360 and 361 shown in Figs. 1 and 14 as disposed toward the outer ends of the superheater coils; These strap constructions are similar to those described above.

The inner ends of the superheater coils are supported by a plurality of constructions exemplified by that indicated in .detail, Figs. 16 and 17 of the drawings. This construction involves upright brackets 500 and 501 sejcured to the upright bar 467. These brackets have enlarged lower portions (or feet) such as 502 and 503 (Fig. 17) extending further outwardly radially of the installation from the lower ends of the upright bar 467 to provide. shelf like supports for the horizontally extending steel rod 505 extending transversely of the superheater section. There are two of the brackets 500 and 501 at the lower end of each of a plurality of the upright bars 466-47 0.

Secured at spaced positions along the rod 505, there are upright plate sections such as 506- 509, with one of the rods 505 threaded through openings in the plate sec- }tions. There is one of these plate sections for each upright flat superheater coil, and welded to the opposite sides of each of these plates are depending tube supporting straps such as 362 and 363, extending around the downwardly successive tube lengths of each flat coil and secured together between these tube lengths in a manner described above relative the superposed convector section. Similar, but shorterpauxiliary strap constructions 512 (Fig. 16) embrace, and are secured to, each of the plate sections 506509, and the contiguous top tube length of each pertinent superheater coil.

'Fig. 16, which is a detail figure showing the top return bend end at the upper part of a superheater coil and its manner of support, also discloses the manner in which the upright bar 467 is secured to the furnace wall. In

*this construction, the furnace wall tube 515 has an outwardly extending :stud 516 welded thereto. This stud 'extends through an opening 517 in bar 467. Beyond this opening is a plate washer 51'8 contacting adjacent parts of the bar and permitting the stud to extend therethrough. The out r end of this stud is welded to the plate washer as indicated at 520.

In considering the description of the illustrative fluid heat exchange installation, it has been appreciated that there are many components of the installation which are substantially similar in construction. It has therefore been deemed sufficient, in such cases, to describe only one of the similar components, or at most, a few of such components. For example, there are, in the installation, twenty-four unbranched and unbroken vapor generating flow paths provided by circuit tubes leading from a common inlet (the connected resistor headers) to a common outlet. Not all of these flow paths have been described in detail, but it is believed that enough of them have been so described that the invention will be clearly understandable to 'those skilled in the art. Again, there are several similar upright segments of .the convection section surrounding the furnace. substantially the same construction. Each includes, reading upwardly, a screen convector unit, a superheater unit, and a plurality of similarly constructed vapor generating convector units above the superheater, all in substantial alignment vertically. Each one of thesesegments has its own upright gas pass leading from an inlet at the base of the installation. They arealso similar in other respects, and, therefore, a detailed description of one has been deemed suflicient for an understanding of all of them.

In the interest of brevity, it has been considered that the installation is, in many respects, symmetrical, and that a description of its component elements in one-half, or one part, is sufiicient for a clear understanding of the elements of the remaining half, or other parts. For example, there are two similar resistor headers at opposite sides of the installation. These'headers have similar numbers of similarly constructed and arranged circuit tubes of the flow paths leading there-from. It has therefore been deemed sufii'cient for a clear understanding of all of such elements to describe only representative elements leading from one of these headers. These elements, or circuit tubes, from the left hand resistor header 1-50, lead, in groups, to the three convection section segments in the left hand part of the installation, as it is shown in Fig. 2. It is to be understood that the similarly arranged tubular elements from the opposite header 151 are correspondingly related to the convection section segments on the other side of the installation. Again, it has been deemed sufficient to describe the detail of one of the pier constructions at the base of the installation, this construction being considered representative of all of the pier constructions.

It will be seen from the above description that this invention provides a forced flow vapor generator which has the following advantages: M

1. Substantial stress reduction, aifordedby-(zz) adequate provisions for expansion; (b) the minimization of external loadings on the tubes; (c) arrangement of the circuit tubes whereby they receive the greater heat inputs in the inlet zones of the tubes; (d) the avoidance of alternate and adjacent high and low heat input zones along the lengths of the tubes to the fluid within the tubes; (2) the outlet zones of the flow circuits containing the greatest amount of steam are subjectedto the lowest rates of heat input.

2. Sectionalized boiler components; all boiler tube circuits are unbroken and unbranched flow path tubes. Those portions of the circuits which are subjected to furnace radiation can be repaired from positions within the furnace or from positions outside the boiler, in the case of the outer furnace walls. Boiler circuits or flow paths are grouped to six identical convector segments and the first two superposed convector units of each segment above each superheater in each segment, are of the same si ze. Therefore the tube banks of these units can be interchanged in and between boiler segments. This not i only facilitates access to the tubes but allows entire convector sections to be quickly removed and replaced by spare sections. The damaged sections can then be repaired and placed in stock.

3. Increased flexibility. The use of a cylindrical or polygonal arrangement provides for ample expansion in all directions. The tubes are held by Welded connections constructed and arranged to facilitate expansion and prevent external tube loading.

4. Improved method of water circulation. The illustrative vapor generator involves the use of a recirculating pump and a main feed water pump mounted on a single shaft. Separate pump housings are provided to prevent a steam bound condition. This arrangementprovides'for age of water recirculated in prior art installations.

These are of similar or through boiler circuits at overloads, as compared to priorart installations. This results from the fact that the amount of water recirculated increases as the ratings decrease and thus the water velocities entering the boiler circuits at the lower ratings can be held to satisfactory values without maintaining a large recirculating water flow at all ratings.

While in accordance with the provisions of the statutes we have illustrated and described herein the best form of our invention now known to us, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by our claims, and that cer tain features of our invention may sometimes be used to advantage without a corresponding use of other features.

We claim:

1. In a forced flow water tube vapor generator, helical coils of water tube sections defining the circumscribing wall of a central furnace, other water tubes presenting substantially identical convector units of spaced horizontal tube lengths arranged in upright alignment in separate gas passes housing convector assemblies, several of which encircle the furnace, each convector assembly including a superheater formed by a bank of horizontally disposed and spaced tubes of uniform length presenting a minor part of the total heat absorbing surfaces in each convector assembly gas pass, an inner casing spaced radially from the furnace wall to define gas pass space for said convector assemblies and walls of said gas passes, other wall means co-acting with the inner casing and the furnace to define separate convector assembly gas passes each including an upright superheater gas pass having a rectangular horizontal section, said space being in communication with the furnace, and a second casing spaced outwardly of the inner casing, both casings having removable sections aligned radially with the convector units whereby access tothe latter is facilitated.

2. In a forcedflow Water tube steam generator having tubes presenting several separate water circuits each similarly exposed to heat of furnace gases and each leading from a water inlet to a steam and water outlet, some of said circuits defining the boundaries of a central furnace, means for axially firing the furnace, others of said circuits presenting a'plurality of substantially identical banks of horizontal short tube lengths arranged as superposed convector sections throughout a space about the furnace and immediately adjacent thereto, convection superheaters with horizontal tubes of uniform length interposed relative to the convector sections in upright gas passes circumscribing the furnace, an inner casing spaced exteriorly of the furnace to provide gas pass space in which said convector sections are disposed, other wall means co-acting with the inner casing and the furnace to define upright superheater gas passes of rectangular cross section as parts of said upright gas passes, and an outer gas-tight casing spaced exteriorly of the inner casing, both of said casings having removable sections aligned with the convector units for access thereto.

3. In a forced flow vapor generator having several long tubes presenting the same number of independent and unbroken flow paths for the movement of a vaporizable liquid therethrough and through a plurality of different temperature zones, means forming a liquid inlet common separate upright gas passes substantially circumscribing the furnace, others of said tubes having parts constituting similar small convector units of banks of vertically spaced horizontal tubes disposed transversely of gas flow in'separate convection assemblies distributed in separate upright gas passes around the furnace in the various gas passes, a superheater including spaced horizontal tubes of uniform length interposed in each of said convection assemblies, wall means co-acting with the furnace and the refractory casing to present a superheater gas pass of rectangular cross section for each of said convection assemblies, pump means providing for the flow of vaporizable liquid through all of said tubes, said flow of vaporizable liquid being in excess of the vapor generating capacity of each flow path, and means receiving the fluid discharge from said flow paths and separating the vapor and the liquid thereinc 4. In a forced flow water tube steam generator of the type having tubes presenting a multiplicity of separate water circuits exposed to the heat from furnace gases and leading from a water inlet to a steam and'water outlet, some of said circuits defining the boundaries of the furnace, and means for firing the furnace; the combination therewith of gas pass Wall means presentinga plurality of upright gas passes arranged in ring formation about the furnace and having furnace gas communication with the furnace at their lower ends, tube hangers and superposed tubular convector steam generating units in each of the circumscribing gas passes, the superposed convector units in each gas pass including banks of tube sections disposed transversely of gas flow and formed by a plurality of conduits presenting continuous fluid flow paths leading through and from a lower convector unit upwardly through the tube sections of superposed convector units to a common steam and water outlet, said banks of tubes being formed by horizontally disposed platens with some of the platens supported in operative positions by said hangers and the remainder of the platens resting upon the supported platens.

5. In a forced flow water tube steam generator of the type having tubes presenting a multiplicity of separate water circuits exposed to the heat from furnace gases and leading from a water inlet to a steam and water outlet, the tubes of some of said circuits defining the boundaries of a furnace, and means for firing the furnace;'the combination therewith of a convection section including gas pass wall means presenting, withsome of the tubes, a plurality of upright gas passes arranged in circumscribing relation about the furnace and having furnace gas communication with the furnace, some of said circuit tubes forming vertically successive banks of horizontal steam generating tubes in said gas passes, a portion of each of said gas passes being of rectangular cross section, and a convection superheater of vertically spaced horizontal tubes of uniform length disposed in said portion of each of said gas passes. a

6. In a forced flow water tube steam generator of the type having tubes presenting a multiplicity of separate water circuits each exposed to the heat from furnace gases and leading as unbranched and unbroken flow paths from a Water inlet to a steam and water outlet, some of said circuits defining the boundaries of a furnace, and means for firing the furnace; the combination therewith of gas pass wall means presenting, with some of the tubes, a plurality of upright convection section segments having upright gas passes arranged in circumscribing relation about the furnace and having furnace gas communication with the furnace, said convection segments including banks of tubes extending across the gas passes and formed by horizontal platens of series connected tube sections, some of which rest directly upon similar underlying platens, and tube hangers supporting said underlying platens.

7. In a forced flow water. tube vapor generator of the ,type having tubes presenting a multiplicity of separate water circuits exposed to the heat from furnace gases and leading from a water inlet to a steam and water outlet, some of said circuits defining the boundaries of a furnace, and means for firing the furnace; the combination therewith of gas pass wall means presenting, with some of the tubes, a plurality of upright gas passes arranged in circumscribing relation about the furnace and having furnace gas communication with the furnace; the gas passes having opposite walls extending divergently outwardly from the furnace, some of said circuits presenting tubular coils having a plan configuration with opposite confines corresponding generally to the diverging walls of the gas passes, and a convection superheater in each of said gas passes, the superheater including horizontally disposed tubular sections ofuniform length disposed in a communication with the furnace; the gas passes having opposite walls extending divergently outwardly from the furnace, the circuit tubes within the gas passes being formed as superposed flat coils, others of said circuit tubes having parts formed as horizontally flat coils or platens having a plan configuration with opposite confines corresponding generally to the diverging walls of the gas passes, some of the coils being stacked within the gas passes and resting upon underlying coils so as to be independently free to separately conform to different thermal conditions, said coils or platens additionally consisting of horizontally disposed tube sections connected in series by re-entrant return bends, and hangers supporting the underlying coils;

9. In a forced flow water tube vapor generator of the type having tubes presenting a multiplicity of separate water circuits exposed to the heat from furnace gases and leading from a water inlet to a steam and water outlet, some of said circuits defining the boundaries of a furnace, and means for firing the furnace; the combination therewith of gas pass wall means presenting, with some of the tubes, a plurality of upright gas passes arranged in circumscribing relation about the furnace and having furnace gas communication with the furnace; superposed horizontally flat coils of series connected tube sections disposed in the gas passes and constituting parts of said circuits, the tube sections of'said coils being end connected by re-entrant return bends and many of said coils being supported only by resting upon the underlying coils, hangers supporting the underlying coils, and external casing spaced radially outwardly of the gas passes and having separately removable sections aligned with groups of said coils.

10. In a forced flow water tube steam generator, a furnace, and means for firing the furnace; the combination therewith of a convection section including gas pass wall means presenting a plurality of separate upright gas passes arranged in circumscribing relation about the furnace and having furnace gas communication with the furnace, each convection section including'a convection superheater, and means connecting the superheaters of different gas passes in pairs with one superheater of each pair receiving the generated steam and connected and arranged for counter-current operation while the other superheater of each pair receives the superheated steam from the first and is connected for parallel flow operation.

11. In a water tube steam generator, a furnace, and means for firing the furnace; the combination therewith of gas pass wall means presenting a plurality of convection section segments including upright gas passes arranged in circumscribing relation about the furnace and having furnace gas communication with the furnace, the gas passes having opposite walls extending outwardlyfrom the furnace, each convection section including a bank of tubes operating as a convection superheater, means series connecting the superheaters of dilferent gas passes in pairs for increased steam mass flow, each pair of superheaters including an inlet superheater in one of said upright passes connected for counterflow operation, the outlet superheater of each pair receiving its steam from the inlet superheater and connected and arranged for parallel flow operation.

12. In a fluid heat exchange installation, a furnace, a convection section, said convection section including similar segments each having its own separate upright gas pass with its gas inlet communicating with the furnace, means forming the walls of said gas passes, means forming a separate series of tubular convector steam generating units for each segment, means firing the furnace, a convection superheater in each upright gas pass, means series connecting a superheater in one gas pass as an inlet superheater with a superheater in another gas pass as an outlet superheater with the inlet superheater arranged for counterflow operation and the outlet superheater arranged for parallel flow operation, and means connecting the inlet superheater with a source of steam.

13. In a forced flow water tube vapor generator installation, substantially helical coils of once-through steam generating tubes defining the upright walls of a central furnace, other once-through steam generating tubes presenting substantially identical convector units of banks of spaced tube sections arranged in substantially upright alignment in separate convector assemblies encircling the furnace, means forming a separate gas pass for each of said assemblies, an inner casing spaced from the furnace to co-operate with the furnace walls to define gas pass space for said convector assemblies, said space being in pendently supported coils.

References Cited in the file of this patent UNITED STATES-PATENTS 989,812 Schmidt Apr. 18, 1911 1,793,867 Niclausse et al Feb. 24, 1931 1,809,270 Gleichmann June 9, 1931 1,812,472 Eule June 30, 1931 1,814,605 Mayr July 14, 1931 1,828,814 Lucke Oct. 27, 1931 1,828,870. Lucke Oct. 27, 1931 1,855,745 7 Keenan Apr. 26, 1932 1,895,790 Eule Jan. 31, 1933 1,908,265 Lucke May 9, 1933 1,978,560 Armacost Oct. 30, 1934 1,979,639 Rebber et al Nov. 6, 1934 2,011,423 Sheldon Aug. 13, 1935 2,046,383 Huet July 7, 1936 2,048,351 Melberg July 21, 1936 2,119,118 Sengstaken May 31, 1938 2,126,248 Eule Aug. 9, 1938 2,160,644 Clarkson May 30, 1939 2,170,345 Bailey et al Aug. 22, 1939 2,170,349 Bailey Aug. 22, 1939 2,270,863 Barnes Ian. 27, 1942 2,285,037 Lobo June 2, 1942 2,405,573 Frisch Aug. 13, 1946 FOREIGN PATENTS 63,373 Denmark Apr. 16, 1945

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