US2515443A - Vapor generator - Google Patents

Description

July 18, 1950 G. D. EB.BETS 2,515,443

VAPOR GENERATOR Filed NOV. 16, 1944 4 Sheets-Sheet 1 INVENTOR George D bbets BY ATTORNEY G. D. EBBETS VAPOR GENERATOR July 18, 1950 4 SheetS- -Sh eet 2 Filed Nov. 16, 1944 INVENTOR George D. Ebbets ATTORNEY G. D. E BBETS VAPOR GENERATOR July is, 1950 INVENTOR Gear 6 D. Ebbeis FQDMOOD Filed Nov. 16, 1944 ATT'IDRNEY G. D. EBBETS VAPOR GENERATOR July 18, 1950 4 Sheets-Sheet 4' Filed NOV. 16, 1944 B M K n3 kw \NVENTOR ATTORNEY Patented July 18, 1950 UNITED STATES TENT OFFICE VAPOR GENERATOR Application November 16, 1944, Serial No. 563,748

12 Claims.

The invention herein disclosed relates to a vapor generator of the water tube natural circulation type especially adapted for operation at high temperatures and high pressures, the form and construction of the unit being such that a minimum amount of metal is required for its manufacture and installation in relation to its high vapor generating capacity. Moreover, the unit is of simple construction involving a minimum number of separate parts.

In the selection of an appropriate boiler of this type it is desirable to provide a certain amount of tubular heat absorbing surface in the path of hot combustion gases leaving afurnace and, for a greater rate of heat transfer and for higher efficiency, to form such convection heated surface of small diameter tubes. For a high capacity boiler using small diameter tubes, the large amount of heating surface is preferably obtained by increased lengths of the heat absorbing tubes rather than by an increased number of relatively shorter tube lengths, one reason being that the longer tube lengths may be fitted to the same tube holes required for shorter lengths so that no additional drilling or increase in drum size is required for their installation.

Heretofore in high capacity natural circulation boilers employing long lengths of heat absorbing tubes connected at their Opposite ends to upper and lower drums, it has been customary to provide a suitable elevated support for carrying the entire weight of the boiler section, the upper drum resting on or being suspended from the elevated structure, and the tube bank or banks together with the lower drum being carried in suspension from the upper drum.

Other forms of boiler units have been constructed wherein the need for overhead suspensions has been largely eliminated as in the known type of integral furnace unit wherein the boiler section and its associated combustion chamber are in laterally adjoining relation'and are supported from below. However, in the bottom-supported units of the prior art, there has been a definite restriction in the permissible length of heat absorbing tubes which could be employed, and consequently a definite limitation in the steam generating capacities of such units using a given number of tubes; the boiler tube bank being required to act as :a column to support an upper drum as well as its own weight, and relatively short tube lengths being required to provide an inherent column strength adequate for the purpose.

It will be appreciated that in following the above prior practices in cases where a given high rate of vapor generation is required, .a selection of the high capacity top-supported type of unit generally involves a large proportion of unheated support metal having no direct con-. nection with the generation ofvapor, while a selection of the limited capacity bottom-sup ported type might require a duplication of units involving a large total metal weight for the capacity obtained.

My invention is therefore directed to the development of a low cost high capacity natural circulation vapor generating unit requiring a minimum weight and number of metal parts in its fabrication and installation, wherein a large percentage of the metal weight is economically utilized in providing heat absorbing surface.

An object of the invention is also the provision of a natural circulation water tube boiler having its component furnace and heating surface of a form and arrangement lending itself to ease and economy of manufacture and erection.

Another object contemplates a water tube boiler wherein long lengths of small diameter heat absorbing boiler tubes are arranged upright and collectively act as a column to support the weight of an overhead steam and water separator including its contained liquid.

A more specific object is directed to a natural circulation bent tube boiler section wherein upright heat absorbing tubes of small diameter act as a column to support an upper boiler drum.

the column strength of a group of such tubes being increased to enable proportionately longer tubes to be used than in former bottom-supported constructions.

An additional object is to provide a bottom supported natural circulation bent tube boiler.

having its upper steam and water drum supported on upright boiler tubes collectively acting as a column, the column strength of one or more groups of such tubes being increased by means also servingto direct heating gases over the,

tubes.

A further object is to increase the load carrying capacity of a group of upright heat absorbing tubes acting as a column without detracting from their ability to absorb heat.

Other objects include the provision of a vapor generating unit wherein the boiler and superheater sections are separately supported from below, each by a separate set of heat absorbing tubular elements.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of my invention.

Fig. 1 of the drawings is a sectional side elevation of a vapor generator constituting an embodiment of my invention; Fig. 2 is a plan view partly in section along line 2-2 of Fig. 1; Fig. 3 is an enlarged fragmentary view of the structure shown in Fig. 1; Fig. 4 is a partial section along line 4-4 of Fig. 3; Fig. 5 is a partial section along line 5-5 of Fig. 3; Fig. 6 is an enlarged fragment of Fig. 1 showing elements of the superheater supports; Fig. 7 is a sectional View of Fig. 6 taken along line l'l; Fig. 8 is an enlarged fragment of Fig. 7 showing -a detail; Fig. ,9 is an enlarged fragmentary section of Fig. 7 taken along line 99; and, Fig. 10 is a sectional view of Fig. 9 taken along line Ill-Ill.

The vapor generator illustrated in Figs. 1 and 2 is of a type wherein the setting provides a furnace or combustion chamber [5 and a boiler space I6 in laterally adjoining relation at approximately the same level; the walls of the setting including the floor and roof I land 3 respectively, upright front and rear walls 19 and 2| respectively, and the two upright side walls 23.

Burners 24 for burning the desired fuel or fuels are arranged in rows across the lower portion of the front wall [9 and heated combustion airis supplied from a suitable source through duct 25.

A boiler section 26 arranged for natural circu- 1 lation is disposed within the boiler space It where it is subject to the hot heating gases of combustion flowing from the combustion space l5 to the gas outlet 21 at the bottom rear of the setting. The boiler sectioncomprises an upper steam and water drum 28, a lower water drum 29, and

spaced groups or banks of upright boiler tubes 3|, 32 and 34 having their upper and lower ends connected respectively to the horizontally disposed upper and lower drums 28 and 29.

The walls of the setting are cooled by fluid carrying tubes having suitable connections with the drums 28 and 29 to form additional natural circulation vapor generating sections in parallel with the boiler section 26. One such section includes tubes 35 associated with the sloping floor I! having their lower ends connected to the lower boiler drum 29 and their upper ends to a cross header 36 from which tubes 31 extend upwardly along the front wall IQ of thecombustion chamber, the tubes 31 continuing as roof tubes 38 in an upwardly inclined direction toward the boiler drum 28 to which their upper ends are connected.

Other sections are formed by upright tubes 39 spacedalong eachof'the side walls 23, the tubes in each side wall having their lower ends connected to a lower side wall header 4| and their upper ends connected in'groups to the three up-' per sidewall headers;42, .43, and 45; the flow circuits being completed by insulated groups of make-up tubes 46 forming downfiow connections from the upper drum 28 to each lower side wall header 4|,and-by insulatedriser tubes 41 forming'upfiow connections from each'set'of upper side wall headers to the upper drum 28. The

upperheaders 42,43-and 45 are preferably arranged at successive levels corresponding in general to the progressively increasing height of the 4 l setting as determined by the upward inclination of the roof I 8. The riser tubes 41 are suitably bent as indicated in Fig. 2 to provide connections at one end normal to the upper headers 22, 43 and 45, and at their other ends normal to the upper boiler drum 28; each riser tube being continuous from its connection to a header to its connection to the drum. In general, the riser tubes 4'! extend horizontally in the planes of the respective headers except for certain intermediate bent portions 48 and 49 as indicated generally in Fig. l where steps are made from one plane to another.

A pendant superheater 5i having inlet connections 52 with the boiler drum 28 is formed with multiple-loop tube coils 53 extending downwardly into the space rearwardly of the boiler bank 3! which serves as a tubular screen for tempering the combustion gases before reaching the superheater and for limiting radiation to the-superheater tubes from the furnace chamber l5; the superheater having discharge connections 54 with its outlet header 56 from which superheated steam may be delivered for use as desired.

The problem of providing adequate support for a unit ofthe character described will be more fully appreciated from dimensions utilized in actual practice.

-, a steam output of approximately 525,000 pounds 3 rear wall 2l than the axis of the lower drum 29.

In each of the boiler banks 32 and 32 the tubes are suitably of 2 inches outside diameter, 0.121 inch thick, with approximately 99 tubes in each longitudinal row, and with eight such rows for bank 32 and ten for bank 34 including the row along rear wall 2|; the tubes in each longitudinal row being arranged at alternate spacings of 5% inches and 3% inches center-to-center, and the longitudinal rows being spaced 4 inches except for certain outer rows which are spaced 5 inches to accommodate longitudinal bafile portions to be later described. These banks are horizontally spaced 23 inches and the front screen bank M is horizontally offset from the axis of the lower drum about 10 feet measured tothe center line of the front row of tubes. The tubes in the screen bank 3| are suitably of 3% inches outside diameter, with the tubes in the two rear rows uni-.

formly spaced and in alignment, and with the tubes in the two front rows double-spaced and in staggered arrangement. The side wall tubes 39 adjacent the boiler section'26 are also of. 2 /2 inches outside diameter while those adjacent the combustion chamber are of 3 inches outside diameter, as are the frontwall and roof tubes 31 and 3B.

A foundation 5'! is provided by which the entire weight of the boiler 26, its water cooled fur- 1 nace l 5 and the superheater 5| is supported from below; the lower boiler drum 29 being received in a series of longitudinally spaced supports 58 secured to the foundation by which the drum is held stationary transversely of its length; the front wall header 36 and the lower side wall headers '4I eachrestin'g on a series of'foundation roller supports 59 and 6| respectively which per- For example, for a unit providing mit movement of the walls relative to-the foundation longitudinally and, transversely of their header lengths; and the water cooled floor I resting on other suitable foundation supperts 62. which also permit movement relative to the foundation 51.

The upright rear wall 2| andside .walls 23 are laterally supported at two levels by aknown form of tie-bar construction by which the inherent rig-- idity of the tube walls is augmented; such a construction including spacermembers E3, .and horizontal buckstays 64 and 85, suitably arranged and connected for holding the wall parts in the desired assembled relation whilepermitting expansion and contraction of each Welland its tubes in the plane of the wall.

In a water tube boiler of the arrangement shown, wherein the upperand lower drums 28 and 29 are at widely separated levels. and long lengths of boiler tubes are requiredto connect such drums, it is desirable to construct and arrange the main boiler tube banks 32 and 34, for example, so as to provide suff cient column strength enabling the weight of the upper boiler drum 26 and its contents to be carried solely by the boiler tubes and the entire weight of the boiler section 28 to be thus supported from below by the lower drum 29. v.

In accordance with the present invention, the column strength of certain boiler tubes is augmented by elements which alsoserve to ,direct the flow of heating gases through the boiler. v As seen in Fig. 1, and in more detail in Fig. 3, the boiler section is provided with baffle structures El, 88 and 69 which define heating gas passes extending generally longitudinally of the tube banks 32 and 34. The front baffle 61 extends upwardly from the lower drum 29 and terminates; at its upper end in spaced relationto the upper drum 28 to define a gas flow space II; the baffle 61 being positioned between the two front rows of tubes I2 and I3 whose lower portions are bent away from the main body of tubes32 to provide an offset baffle portion I4 defining an unobstructed gas turning space I5. The intermediate 1:

bafile 68 includes an upper longitudinal portion 16 extending downwardly alongthe bank 34 between the two front rows of tubes ,I8 and I9, and a lower inclined portion 8| extending partially across the tube bank 32 opposite the gas turning space I5; the lower baffle portion8I being -sup ported on inclined portions 82 of loops 83 formed. by alternate rear row tubes bent'away from the bank 32. The rear baflle 6 9 includes a lower, longitudinal portion 84 positioned between the front rows of tubes 18 and I9 of bank 34, an upper longitudinal portion 85 positioned between the rear rows of tubes 86 and Ill, and an intermediate portion 89 inclined upwardly across the bank 34 from the top end ofthelongitudinal bafile portion 84 to the bottomend; ,of ;the; long-i tudinal baflle portion 85. v

The hot gases from the combusl ibn chamber,

I5 are caused to flow over the front screen bank;

of boiler tubes 3I and over the depending, sup r: heater loops 53 in a single transversegpass, the gases entering the intermediate boiler tube" bank 32 through the gas space H adjacent the. .upper boiler drum 28 and turning around the upper end' of the front bafile 6! to flow downwardly between the baflies '61 and 68 longitudinally. of theytube I bank 32; the gases then turning within; the space.

I5 around the lower end of theflintermediate bafile 6-8 to flow upwardly between the baffles 682 and 69 longitudinally of the rear tubesybanknflr the gasesthen turning around the upper endof the rear baflle 69in the space adjacent the upper drum 28 to flow downwardly in the open pass 9I lined by tubes 86 and 92 of the rear bank 34 and by side Wall tubes 39; the gases traversing the lowerportion of the rear bank 34 to enter the outlet 21. I

Access doors 93, 94and 95 are provided in both side walls 23 at suitable locations to permit inspection and cleaning interiorly of the setting; the door 94 being available for access to the combustion chamber for which purpose certain tubes of the screen bank 3 I, such as are enclosed within the reference rectangle 91 (Fig. 2), are reversely bent to form loops 98, preferably midway of the width of the bank, to thus provide the necessary clearance space between adjacent tubes; the door 95being for access to the upper cavity IIII between-the spaced banks 32 and 34 for which purpose the upper inclined tube lengths I82 of loops 83 are displaced vertically to provide the necessary clearance space therebetween.

In order to provide the columnstrength required .to support the upper drum 28 by tubes connected thereto, the tubes of banks 32 and 34 are engaged by transversely arranged stiffener plates 8| and 89 which in the illustrated embodimentconveniently form portions of the gas directing baflle structures 88 and 69; plate 8| en--v gaging tubes in a majority of the rows inbank 32 and tubes I8 in a single row in bank 34;. and plate 89 engaging tubes in a majority of the rows in bank 34. .Such stiffener plates or baffles are preferably of known monolithic hardened plastic formation and provide close engagement peripherally of individual tubes in all directions transversely of their lengths; thereby increasing the column strength of the bank 32 or 34 with which each is associated and, furthermore, minimizing the vibration tendency of the long straight lengths of tubes. An additional stiffener I83 of similar formation is positioned across the upper portion of the tube bank 32 where it engages tubes of the bank not engaged by the stiffener 8i across the lower portion; the stiffener I83 preferably being sloped generally in the desired direction of gas flow at the upper location.

The stifieners M, 89 and I83 are especially effective since each is suitably guided at its ends to prevent lateral displacement. The detail ar-' rangement is illustrated in Fig. 4.- where the stiffener plate 8I, for example, is molded around the wall tubes 38 and extends to the inner face I84 of each side wall 23 except for a minimum clearance I afforded by a paper strip inserted prior to molding to prevent bonding to the side wall tile. The plate '8I is also molded around the upper surfaces of the supporting tubes 82 to pro vide grooves I86 within which the tubes 82 are embedded. Plates BI and 89 are each-molded to also provide flat joint surfaces I61 adjacent" the upper longitudinal ibafile portions I6 and 85. T The front longitudinal bafile BI', and the lon gitudinal bafiie portions "I6 and 85, are suitably formed of tile I08 laid up in mortar in successive horizontal r'ows; in baffle 61, certain tile being cut or otherwise. fitted around the horizontal row of spacerbars I09 which are secured "to aligned tubes of rows I2 and I3 adjacent the bend I II]; in each ofxportions I6 andi85, the bottom row of tile Ill8resting on a bracket I I2 secured-to the associatedrow of tubes I8 or 81.

j Thesuperheate'r;a5zl, .having loops or coils, 53 disposed between the boiler banks 3| and 32,15

preferably. supported separately; from-the boiler section 26, and in the present instance is so arranged that the major portion of its Weight is transferred to the upper sidewall headers 45 for support by the side wall tubes 33. In this manner-{the upright boiler tubes of banks 3I, 32 and 34 are relieved of a considerable weight load which, in previous constructions, such tubes would ordinarily be required to support. The presentcohstructionjtherefore, withless load to be carried by the boiler tubes, permits longer lengths' 'of boiler tubes to be installedand thus a greater amount of heat absorbing surface, for a given cross'section of tube bank or banks.

Each superheater coil 53 comprises four substantially straight uprighttube lengths I'I3 connected in series by loops II 4 and II5 at their upper" and lower ends respectively, each coil lying substantially in a plane transverse to the length of the boiler drum 28 and successive coils being arranged across the widthof the setting about as shown in Fig. 7 where loops II4 are disposed in pairs between successive tube rows formed by the inclined portions I I 6 of the screen bank tubes 3| and of'the roof tubes 38. The inlet and outlet connections 52 and 54 for each coil are similarly disposed except for the'end coils II! where such connections are bent as at H8 into the plane of the next adjacent coil 9 and its connections. g

' The superheater coils are suspended from the row of roof tubes 38 and the roof tubes in turn suspended from an overhead girder I2! having its ends resting on roller bearings I23 by which the total supported weight is transferred to the upper headers 45 and: thus to upright tubes 39 of'water cooled side walls 23. The majority of the coils 53 have their respective upper loops II4 supported from horizontally spaced bars I24 secured to their respective inlet and outlet coni I nections 52 and 54, a bolt I25 having its lower end suitably secured to each loop and its upper end arranged to engage the upper edges of a pair of bars I24. Each pair ofinlet connections 52 and each pair of outlet connections 54 is fitted with a clamp I26 formed of complementary members I21 welded as at I28 to each embraced tube and having their ends bolted together and resting on the horizontal upper surfaces of pla tform blocks I29 welded to successive'roof tubes 38. 'In the case of each end coil II'I, the bolt I25 engages a similar pairof bars I3I connected in suitable manner to a roof tube 38 at the end of the row; the end coils II! and Shaving I their inlet and outlet connections 52 and 54 each fitted with a clamp I32 similar to clamp I25, but engaging a single connection instead of a pair, and resting on additional platform blocks I29 arranged as previously described.

The structure for supporting th roof tubes 38 1 from the girder I2I includes a series of "angle clips'l 34 secured to successive tubes 38 andbolted to other angle members I35 which are suspended by a series of clevis rods I36 from a channel I31 adjacent the under side of a series of riser tubes 41; the channel I31 being suspended from pension structure as for girder I2I and causing the suspended weight to be transferredto the upper side wall headers 43 and thus toside wall tubes 39.

In describing the vapor generatorof the pres-.1:

. the overhead girder I 2I by bolts I38; thereby ent invention, an example has been given in which the center-to-center distance between the upper and lower drums 28 and 29 is 34 feet, or 163.2 tube diameters, using stiffener plates BI, 89 and I03 to augment the inherent column strength of the drum supporting tube groups. As a further detail of the arrangement it may be explained that at section 2-2 and above, where the tube lengths are vertical, the eight closely spaced longitudinal rows of bank 32 provide a centerline depth of 2 feet 5 inches, while the nine closely spaced longitudinal rows of bank 34 provide a centerline depth of 2 feet 10 inches; the overall depth across these two main tube groups at the level indicated being 7 feet 2 inches measured between the center lines of th outer tube rows 12 and 86.

Without the transverse tube bank stiifeners BI, 89 and I03, but assuming the same cross sectional pattern of boiler tubes, the maximum permissible elevation or distanc between drum centers would be from 20 to 25 feet, or 96 to tube diameters; the latter limit being related to 2 inchoutside diameter tubes of the wall thickness heretofore specified, while the lower limit would apply to tubes of a lower sectional modulus resulting from either a reduction in outside diameter or reduction in wall thickness, or both. These height limitations are determined by two considerations-first, the column strength of the tubes since they act as vertical columns to support their own weight combined with the weight of the upper drum and'a part of the roof; and second, the vibration tendency of any long straight tube. Any appreciable increase over the limiting heights of 96 to 120 tube diameters might therefore result in failure of the unstiffened tube bank through bowing and buckling 0f the tubes to'such an extent that they could not support themselves and the steam drum,or failure could result through excessive vibration of the tubes; the maximum length of tube without transverse support which is acceptable from a vibration standpoint being about the same as the similarly unsupported length permissible as a column.

dimensions being taken as the average vertical distances that the respective inclined stiffeners are spaced from the drum axis level which is farther away. Plate 89, for example, across bank 34 and farthest from the source of heat, is thus positioned at the maximum recommended distance of substantially 120 tube diameters from the level of the upperdrum axis; plate 18I, across bank 32, at a distance or substantially no tube diameters from the level of the upper drum axis; and plate I03, across the upper portion of bank 32, at the maximum recommended distance of substantially 120 tube diameters from theilevel of the lower drum axis.

As far 'as column action of the tubes is con cerned, the distanceof 34 feet or 163.2 tube diameters, as in the present embodiment, could be extended if desired by installing additional transverse stiif ener plates, especially if the plates are tied into the side wall of the boiler in the manner as shown in Fig; 4,'for example, whereby individual tubes are supported as columns and the entire tube group or bankis also supported as a column;

, 9 I-cl'aim:

l. A bottom supported bent tube boiler comprising a lower drum, an upper drum, and an elongated bank of upright small diameter tubes connected at opposite ends to said drums, a bafile extending upwardly from said lower drum adjacent the front of said bank and defining a gas inlet to said bank adjacent said upper drum, a baflle extending downwardly from said upper drum adjacent the rear of said bank and defin ing a gas outlet from said bank adjacent said lower drum, said front bafile having an intermediate lower portion offset from the majority of the tubes of said bank to form an unobstructed gas turning space, said rear bafile terminating in a downwardly inclined plate-like stiffener member of rigid monolithic formation extending partially across a lower portion of said bank toward said gas turning space, and a similar rigid plate-like stiffener mem-l-ier extending across an upper portion of said bank from said gas inlet, said last named stiffener member being positioned at an elevation intermediatethe height of said inlet and bein inclined in the general direction of gas flow into said bank.

2. A bottom supported bent tube boiler comprising a lower drum, an upper drum, and an elongated bank of upright small diameter tubes connected at opposite ends to said drums, a baffle extending upwardly from said lower drum adjacent the front of said bank and defining a gas inlet to said bank adjacent said upper drum, 2. bafiie extending downwardly from said upper drum adjacent the rear of said bank and defining a gas outlet from said bank adjacent said lower drum, said front baffle having an intermediate lower portion offset from the majority of the tubes of said bank to form an unobstructed gas turning space, said rear bafiie terminating in a, downwardly inclined plate-like stiffener member of rigid monolithic formation extendin partially across a lower portion of said bank toward said gas turning space, and a similar rigid plate-like stiffener member spaced throughout from said baffles and extending across an upper portion of said bank from said gas inlet, said plate-like stiffener members closely embracing individual tubes of said bank throughout their peripheries and constituting means for augmenting the inherent column strength of said bank, said drums having their longitudinal axes vertically separated a distance greater than one hundred twenty tube diameters, and each of said stiffener members being vertically spaced from the axis of the farther drum a distance less than one hundred wenty tube diameters.

3. A bottom supported bent tube boiler section comprising a lower drum, an upper drum, and horizontally spaced elongated front and rear banks of upright small diameter tubes connected at opposite ends to said drums, a front baille extending upwardly from said lower drum adjacent the front of said front bank and defining a gas inlet thereto adjacent said upper drum, an intermediate baffle extending downwardly from said upper drum adjacent the front of said rear bank and defining a gas outlet therefrom into said rear bank adjacent said lower drum, a rear baflle extending upwardly from said lower drum longitudinally of said rear bank and defining a gas outlet therefrom adjacent said upper drum, said front bafile having an intermediate portion forwardly oifset from a majority of the tubes of said bank to form a substantially unobstructed gas turning space, said intermediate bafile terminating at its lower end in a plate-like stiffener portion of rigid monolithic construction extending partially across said front bank toward said gas turning space, said rear baffle including an intermediate plate-like stiffener portion of rigid mono lithic construction extending across a lower portion of said rear bank at a level lower than said first named plate-like stiffener portion, and means including said plate-like stiffener portions for increasing the inherent column strength of said banks to provide a column strength sufficient to sustain the entire weight of said boiler section and the liquid contained therein during normal operation.

4. A bottom-supported vapor generating unit comprising a natural circulation bent tube boiler section having upper and lower drums, a front and a rear bank of upright tubes connected at opposite ends to said drums and having the major portions of their lengths substantially straight and vertical, said drums having their longitudinal axes in substantially the same vertical plane and said banks being horizontally spaced from said plane at opposite sides, said straight length tube portions in each of said banks being closely spaced in rows extending longitudinally and transversely of said drums, a pendant superheater disposed forwardly of said banks, a combustion chamber arranged forwardly of said superheater and having upright heat absorbing tubes in its side Walls having natural circulation flow connections with said boiler drums, means for directing heating gases from said combustion chamber over said superheater and boiler section, said gas directing means including rigid monolithic plate-like members extending across a majority of the tubes in said banks, means including said monolithic members for stiffening said banks of tubes to provide column strength sufficient to support the combined weight of said upper drum and said tubes and contained liquid, a foundation having means engaged by said lower drum for supporting the entire weight of said boiler section, means for transferring the major portion of the weight of said superheater to the upper ends of'said fluid cooled side walls, and means on said foundation for supporting the combined weight of said side walls and the superimposed weight of said superheater. r

5. A bottom-supported vapor generating unit comprising a natural circulation bent tube boiler section having upper and lower drums, a front and a rear main bank of upright tubes connected at opposite ends to said drums and having the major portions of their lengths substantially straight and vertical, said drums having their longitudinal axes in substantially the same vertical plane and said two main banks being horizontally spaced from said plane at opposite sides, said straight length tube portions in each of said banks being closely spaced in rows extending longitudinally and transversely of said drums, a combustion chamber arranged-forwardly of said banks and having fluid cooled side walls disposed transversely of said drums, said fluid cooled walls comprising upright heat absorbing tubes having connections with said boiler drums to form a secondvapor generating section of said unit, a pendant superheater' disposed between said combustion chamber and said banks, a screen bank of upright boiler tubes having connections with said upper and lower drums disposed between said combustion chamber and said superheater, means for directing heating gases from said'combustion chamber over saidscreen bank and said 11 superheater in a single pass and over said front and rear main banks in a plurality of generally longitudinal passes, said gas directing means including rigid monolithic plate-like members inclined across a majority of the tubes in each of said two main banks, means including said inclined members for stiffening said two main banks of tubes to provide column strength sufficient to support the combined weight of said upper drum and said tubes and contained liquid, 2

a foundation having means engaged by said lower drum for supporting the entire weight of said boiler section, means for transferrin the major portion of the weight of said superheater to the upper ends of said fluid cooled side walls, and means for transferring said superheater weight portion to said foundation through said upright side wall heat absorbing tubes.

6. A vapor generating unit comprising a combustion chamber and a vertically elongated bank .of' upright generating tubes laterally adjoining said chamber, an upper drum and a lower drum to which the upper and lower ends of said tubes are connected, said tubes having vertically disposed straight length portions closely spaced in rows arranged longitudinally and transversely of said drums, said combustion chamber having extended side wall portions paralleling said transverse tube rows at opposite ends of said bank, horizontally spaced vertical lengths of tubes exposed along the inner face of each of said side wall portions, and a monolithic plate-like stiifener member arranged transversely of said bank in close peripheral engagement with the majority of the straight length tube portions thereof, said member extending to said side wall portions and havin its ends formed with recesses each embracing one of said side wall tube lengths.

'7. A vapor generating unit comprising a combustion chamber and horizontally spaced banks of upright generating tubes laterally adjoining said chamber, an upper drum and a lower drum to which the upper and lower ends of said tubes are connected, said tubes having vertically disposed straight length portions closely spaced in rows arranged longitudinally and transversely of said drums, said combustion chamber having extended side wall portions paralleling said transverse tube rows at opposite ends of saidbanks, horizontally spaced vertical lengths of tubesexposed along the inner face of each of said side wall portions, and monolithic plate-like stiffener members arranged transversely of said banks in close peripheral engagement with the majority of the straight length tube portions thereof, one of said members having a portion inclined across the space between said banks, one of said banks including tube length portions formed in loops across said space for supporting said inclined member portion, each of said members extending to said side wall portions and having its ends formed with recesses each embracing one of said side wall tube lengths.

' 8. A vapor generating section comprising an upper drum and a lower drum having longitudinal axes in substantially the same vertical plane, upright tubes connected at upper and lower ends to said drums and formin a forward and a rearward tube bank horizontally spaced from said plane at opposite sides, a bafile extending upwardly from said lower drum adjacent the front of said forward bank and defining a gas inlet thereto adjacent said upper drum, a plate like stiffener member inclined downwardly toward said bafile across tubes of said forward bank, said bafile having a forwardly offset portionspaced from the lower end of said member, a'plate like stiffener member generally parallel to said first named member and extending across tubes of said rearward bank, and baflle means including said members for directing gases from said inlet over said banks of tubes.

9. A bottom-supported boiler-superheater unit comprising a boile'rsection having an upper and a lower drum and having upright tubes con nected at opposite ends to said drums, a pendant superheater disposed forwardly of the majority of said tubes, a combustion chamber arranged forwardly of said superheater and having fluid cooled side Walls formed with upright heat ab sorbing tubes therein having'fluid flow connections with said drums, means for directin heating gases from said combustion chamber over said superheater and said boiler section, said gas directing means including rigid monolithic plate-like members extending across and engagin the majority of said tubes to provide column strength sufficient to support the combined weight of said upper drum and said tubes and contained liquid, means for transferring the major portion of the weight of said superheater to said fluid cooled walls, and foundation means for bottom-supporting substantially the entire weight of said boiler-superheater unit including the combined weight of said walls and the superimposed weight of said superheater.

10. A vapor generating section comprising an upper drum and a lower drum having longitudinal axes in substantially the same vertical plane, upright tubes connected at upper and lower ends to said drums and forming a forward and a rearward tube bank horizontally spaced from said plane at opposite sides, a baflle extending from one of said drums toward the other of said drums adjacent the front of said forward bank and defining a gas inlet thereto adjacent said other drum, a plate-like stiffener member extending toward said baflle across tubes of said forward bank and terminating intermediate the height of said baflle in spaced relation thereto, a separate plate-like stifiener member extending across tubes of said rearward bank, and bafiie means including said members for directing gases from said inlet over said banks or tubes.

11. A bottom supported boiler component comprising a lower drum, an upper drum, and horizontally spaced upright tubes of small diameter in comparison with their lengths connected at opposite ends to said drum, said drums being horizontally arranged and having their longitudinal axes vertically separated a distance greater than one hundred twenty times the diameter of said tubes, the majority of said tubes being arranged in horizontally spaced banks and having the major portions of their lengths substantially straight and vertical, the majority of tubes forming said banks being confined to a horizontal width of space coinciding with the horizontally projected diameter of said upper drum, means for bottom supporting said lower drum, and stiffener means for augmenting the inherent column strength of said upright tubes to provide a column strength sufficient to support the combined weight of said upper drum and said tubes and the liquid contained therein during normal operation, said stiffener means comprising rigid plate-like members arranged transversely of said tubes and closely embracing said straight and vertical portions of individual tubes forming said banks, each of said members being vertically 13 spaced from the axis of each of said drums a distance less than one hundred twenty times the diameter of said tubes. 12. A bottom supported boiler component as claimed in claim 11 wherein said upper drum is of, 5

larger diameter than said lower drum and the longitudinal axes of said drums are disposed substantially in a common vertical plane intermedi ate said banks.

GEORGE D. EBBE'IS.

14 REFERENCES CITED The following references are of record in the file 01 this patent;

UNITED STATES PATENTS Number Name Date 1,733,474 Wan Brunt Oct. 29, 1929 1,748,113 Danks et a1. Feb. 25, 1930 2,112,202 Lucke' Mar. 22, 1938 2,114,252 Kolling Apr. 12, 1938 2,326,513

Bailey et a1 Aug. 10, 1943

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