US3241530A - Scotch marine fire tube boiler - Google Patents

Description

2 Sheets-Sheet 1 E. T. BLOCKLEY ETAL SCOTCH MARINE FIRE TUBE BOILER INVENTORS -UGNE 7: BLCKLEY MCM] 4 7 TOR/VFY EVERETT MAG/VUSO/V BY? March 22, 1966 Filed July e, 1964 March Z2, 1966 E. T. BLocKLEY ETAL 3,241,530

SCOTCH MARINE FIRE TUBE BOILER Filed July 6, 1954 2 Sheets-Sheet 2 0h51 Q /fZg-Q/@f d@ /2 f Q QQ QQ f QQQ Q@ Q Q Q* INVENTORS EUGENE T. BLOC/L EY EVERETT E. MGM/50N nitd Stats Patent 3,241,530 SCUTCH MARINE FIRE TUBE BOILER Eugene 'I'. Blocliley, Chattanooga, and Everett E. Magnuson, Signal Mountain, Tenn., assignors to Eclipse Fuel Engineering Co., Rockford, lll.

Filed .luiy 6, 1964, Ser. No. 380,517 S Claims. (Cl. 122-410) The present invention relates to a liquid distribution system which is expressly designed for use in a Scotch marine fire tube boiler and by means of which heat transfer from the tire side to the liquid side of the boiler t which the distribution system is applied is more evenly distributed through the various heat transfer areas of the boiler than has heretofore been possible. According to the invention, this is accomplished by the provision of a novel pattern of liquid flow transversely past and in between the various tire tubes, including both the large furnace tube and the group or bundle of smaller lire tubes thereabove, as well as across the tube sheets, the pattern being such that all of the tubes will operate at substantially uniform and safe temperatures.

Inasmuch as in a Scotch marine fire tube boiler there is provision for firing of the boiler burner directly into the large furnace tube, with recirculation taking place through the bundle of smaller tubes above the furnace tube, it is apparent that the furnace tube is subject to an appreciable amount of radiant heat, as well as heat of conduction and heat of convection. The furnace tube, therefore, in the absence of an eicient liquid distribution system, is subject to sudden and extreme temperature changes over its entire area, as well as in localized regions or areas. Furthermore, without an eicient liquid distribution system to maintain all of the tubes, including the large-sized furnace tube, operating at normal temperatures, some of the tubes will operate at low temperatures while others will operate at high temperatures. This places a stress upon the tubes, as well as upon the tube sheets, resulting in strain at the juncture regions between the tube ends and the tube sheets. Repeated strain frequently results in failure of either the metal of the tubes or of the tube sheets. A common area of tube failure is at the bottom of the large furnace tube Where it is joined to the tube sheet that is remote from the burner. Cracking of the furnace tube at this region is not an uncommon occurrence in connection with normal operation of a Scotch marine boiler. An additional failure area is near the bottom of the tube sheet that is remote from the burner because there cracks frequently develop in the metal of the tube sheet between the furnace tube joint and the adjacent lire tube joints.

The water distribution system that is commonly employed in connection with a Scotch marine boiler involves simply a water inlet port and a water outlet port in spaced apart relation in the top region of the shell, together with means for introducing water or other liquid under pressure into the boiler shell through the water inlet port. Thus, the water which attempts to follow the line of least resistance in finding its way from the inlet port to the outlet port, short circuits across the central upper region of the boiler shell interior, making good wiping contact with only the medial regions of a few of the uppermost small diameter tubes. This allows for poor heat transfer near the ends of the tubes and at the tube sheets with consequent overheating of these regions of the tubes and sheets.

The present invention is designed to overcome the above-noted limitations that are attendant upon the construction and use of a conventional Scotch marine lire tube boiler and, toward this end, the invention contemplates the provision of a novel distribution system for the liquid phase of such a boiler, the system embodying a Water inlet and distribution manifold, and a diametrically opposite water outlet collection manifold which are po sitioned wholly within the confines of the boiler shell and are coextensive with the longitudinal extent of the shell. The inlet and distribution manifold is disposed beneath the large furnace tube of the boiler and has formed therein two longitudinally extending rows of spaced outlet ports which direct the water upwardly around the opposite side portions of the furnace tube in such manner that the water thereafter converges upon the bundle of re tubes above the furnace tube. The outlet collection manifold is disposed at the top of the shell and a single row of inlet ports therein draws the water or other liquid from the upper region of the shell a small distance below the top of the shell interior so that the space within the shell, above the single row of inlet ports, and at the sides of the collection manifold constitutes a chamber for the entrapment of steam or air which may collect within the shell interior is connection with use or operation of the boiler.

Although the distribution system of the present invention does, in fact, improve the over-all heat transfer through the walls of the various tire tubes, this is not the primary purpose of the invention, the primary purpose being to delegate an equal heat transfer load to all of the tubes in a Scotch marine boiler, including the large furnace tube and the bundle of small-sized tire tubes above the furnace tube, thereby equalizing relative tube elongation and shortening and reducing tube and tube sheet stresses under sudden changes in firing conditions, particularly in the end regions of the tubes.

The provision of a Scotch marine re tube boiler having a Water distribution system of the character briey outlined above and possessing the stated advantages being the principal object of the invention, other ancillary objects and advantages not at this time enumerated will readily suggest themselves from a consideration of the following detailed description.

In the accompanying two sheets of drawings forming a part of this specification, one exemplary embodiment of the invention has been shown.

In these drawings:

FIG. l is a sectional view, partly in elevation, and somewhat schematic in its representation, of a Scotch marine lire tube boiler embodying the novel water distribution system of the present invention;

FIG. 2 is a sectional view taken on the line 2 2 of FIG. 1;

FIG. 3 is an enlarged top plan view of the inlet and distribution manifold that is employed in connection with the distribution system of the present invention;

FIG. 4 is a fragmentary bottom plan View of the outlet and collection manifold that is employed in connection with the improved distribution system; and

FIG. 5 is an enlarged sectional View taken on the line 5 5 of FIG. l.

Referring now to the drawings in detail and in particular to FIG. l, the `boiler that is illustrated therein is designated in its entirety by the reference numeral 10 and is schematically portrayed -for a better understanding of the ilow of water or other liquid through the liquid phase of the system and of the ilow of combustion gases through the combustion phase. The details of the boiler shell such as any insulation which may be associated therewith, the mechanical connections between the various sections or :parts of the shell, the combustion chamber, the burner and its mountings, the control devices lfor boiler operation, and other boiler instrumentalities which may be employed and may vary widely' in their construction and design, have ybeen omitted from the disclosure in the interests of clarity since any relation which they may bear to the present invention is purely incidental.

The boiler 10 is essentially a Scotch marine re tube boiler and is in the category of a liquid phase boiler which is designed f-or raising the temperature of liquids having a high specific heat, such, for example, as water, certain ytypes of Dowtherm and other proprietary heat transfer liquids, and certain heat transfer oils. Briefly, the boiler 10 comprises a boiler shell 12 of generally cylindrical design, one end of the shell being closed -by a circular front tube sheet 14 and the other end of the shell being closed by a circular end wall 16. A rear tube sheet 18 is spaced a comparatively short distance forwards of the end wall 16 and divides the interior of the shell into a tube section 20 and a combustion section 22, the latter affording a rear turn-around or reentry chamber 24 for combustion gases, as will be described presently. The chamber 24 is lined with refractory material 26 in the usual manner.

The shell 12 is suitably supported upon standards 38, which, in turn, are mounted on a boiler base 32. The axis of the cylindrical shell extends horizontally. A conventional Aburner assembly which is schematically shown at 34 fires into a tubular combustion block 36 which is formed of refractory material and lits snugly within the front end of a large diameter, horizontally extending furnace tube 38. The latter has its rear end secured in the rear tube sheet 18 and sealed to the rim of an opening 40 therein in any suitable manner, as, for example, by welding. The forward region of the furnace tube 38 passes completely through an opening 42 in the front tube sheet 14 and is sealed to the rim of the opening by welding. The openings 4t) and 42 are centered and disposed in the lower regions of the tube sheets 18 and 14 (see FIG. 2) in accordance with conventional Scotch marine yboiler practice.

Immediately above and on opposite sides of the relatively large diameter furnace tube 38 is the usual crescent-shaped bundle t) of individual heat exchange fire -tubes 52, such tubes being of appreciably smaller diameter than the furnace tube 38. The tubes 52 preferably have their ends expanded against and welded to the rims of holes 54 and 56 in the front and rear tube sheets 14 and 18. The upper region of the boiler shell in the tu-be section 20 thereof is devoid of tubes so that the normal water line which is indicated at wl-wl in FIG. 2 lies appreciably above the level of the uppermost fire tubes of the bundle 5t) whereby all tubes are at all times submerged when the boiler is in operation.

The front ends of the heat exchange fire tubes 52 communicate with a flue gas collection chamber 60 having an upwardly extending stack 62. The Scotch marine boiler is thus of the dual pass type wherein the in terior `of the furnace tube 38 constitutes a combustion chamber 64, while the turn-around or reentry chamber 24 constitutes an extension of such combustion chamber. Combustion takes place in the chambers 64 and 24 on the first pass and the hot products of combustion make a second pass through the fire tubes 52 of the ybundle 50 and leave the boiler through the ue gas collection chamber 60 and the stack 62.

In connection with the liquid phase of the boiler 10, a liquid inlet 70 is provided mid-way between the front and rear tube sheets 14 and 18 and at the extreme bottom of 4the boiler shell 12. Similarly, a liquid outlet 72 is provid-ed midway between the tube sheets and at the extreme top 0f the shell.

The arrangement of parts thus far described is purely conventional in its design and no claim is made herein to any novelty in it, the present invention consisting rather in the hereinafter described novel distribution system for the liquid phase of the boiler.

The -boiler 10 is essentially a forced feed liquid phase boiler and, in order to induce proper How of liquid through i the tube section 2@ and across the tubes 38 and 52, the inlet 78 is operatively connected to a source of liquid under pressure, for example, press-ure which is induced by the provision of a suitable motor-driven pump 74 in the liquid inlet line '76 leading to the inlet 70.

In order to prevent short-circuiting of the liquid and to effect a more even distribution of the heat transfer effect within the tube section 20 `of the shell 12, as well as to distribute the heat transfer load equally among the tubes 38 and 52, an elongated distribution manifold 8i) is disposed within the shell in the lower region thereof and encompasses the liquid inlet '78. A similar liquid outlet collection manifold 82 is disposed within the shell in the upper region thereof. Both manifolds are disposed entirely within the cylindrical contines of the shell 12. The two manifolds 80 and 82 are similar in their design and construction but they assume opposite or inverted relationships within the interior of the boiler shell.

As best seen in FIGS. 2 and 5, the distribution manifold 88 is of inverted trough-like design and comprises an elongated side wall 84 and front and rear semi-circular end walls 86 and 88, respectively. The wall 84 is generally semi-circular in transverse cross section and is provided with two longitudinally extend-ing parallel rows of holes 91) therein, the rows being spaced apart approximately 30 on the curved side wall 84 -of the manifold 80 and being equally spaced from a medial longitudinal and radial plane of the wall. The angle of spacing is, however, not too `critical and other angles are contemplated. Furthermore, the specific number of holes involved is not critical and depends upon such variable factors as boiler capacity, the character of the liquid undergoing heating, and mechanical boiler design features. irrespective, however, of the spacing, angle and number of holes involved, the essential features of the invention remain undisturbed. The end walls 86 and 88 of the manifold 80 are imperforate except for the provision of small drain holes 91 and 92 at the extreme bottom portions of the end walls where they join the shell 12.

The collection manifold 82 is generally similar to lthe distribution manifold 80, and differs therefrom solely by the distribution of holes therein. The collection manifold 92 includes an upright trough-like side wall 94 and front and rear semi-circular end walls 96 and 98. A single row of holes 180 is formed in the wall 94 along the extreme bottom thereof. The end walls 96 and 98 are imperforate.

The two manifolds 80 and 82 have their rectangular rims secured by welding to the inner surface of the shell 12, the manifold 88 being inverted and encompassing the liquid inlet and the manifold 82 being upright and encompassing the liquid outlet 72. The longitudinal extent of both manifolds 88 and 82 is slightly less than the distance between the front and rear tube sheets 14 and 18 and the manifolds are so disposed that the end walls thereof are slightly spaced from the respective tube sheets which they oppose.

When the boiler 10 is set into operation, the relatively cold liquid (water) which passes into the shell 12 through the liquid inlet 76 under the influence of the pump 76 distributes itself within the `distribution manifold and flows longitudinally in opposite directions along the manifold toward the opposite ends thereof. This flow of liquid in the manifold, as well as through the tube section 20 of the yboiler shell 12, is represented by various ow arrows in FIG. 2. An appreciable portion of the liquid Iwhich emerges from the two rows of holes 90 will impinge against the underneath side of the furnace tube 38 on opposite sides of the vertical longitudinal plane of the tube and the streams of liquid will be deflected outwardly in such a manner that the total volume of liquid issuing from the manifold will be divided substantially equally, with one-half of the liquid passing upwardly around each side of the furnace tube 38. Above the level of the furnace tube 38, the streams of liquid will converge as they ente-r the bundle 50 of fire tubes 52 and then flow upwardly between the various tubes 52 and toward the collection manifold 82.

Because of the longitudinally spaced holes 100 in the collection manifold 82, liquid `will be taken off from the space ab-ove the tube bundle 50 at spaced points therealong and there will be little tendency for central drift of the liquid in the general direction of the liquid outlet 72 which otherwise would be the case in the absence of the collection manifold 82. The liquid will thus flow uniformly almost diametrically a-cross the shell at all longitudinal regions therealong.

During operation of the boiler 10, small steam and other gas bubbles may be created at the outer surface of the furnace tube 38 and these will rise in the body of liquid `within the -shell and collect in the extreme upper regions of the tube section of the shell in an area which has Ibeen designated at 110 in FIG. 2 and is herein termed a steam pocket. This steam pocket is connected through a small bleed port 112 and 'bleed line 114 to a suitable collector chamber (not shown) and the pressure of gas in the steam pocket is normally such that the water line wl-wl is maintained a -slight distance above the level of the row of holes 100 in the collection manifold 82.

Due to the presence of the colder incoming liquid in the vicinity of the furnace tube 38, much heat is transferred through the wall of the tube to this cold liquid. The liquid which reaches the tube bundle 50 assimilates appreciable heat from the furnace tube, but by the same token, the flue gases passing through the tire tubes 52 of the tube bundle 50 are appreciably cooler than are the gases in the furnace tube 38. Thus, there will be no undue chilling of the tubes 52 and equalization of heat transfer through all of the tubes, that is, both the furnace tube 38 and the tire tubes 52, will take place. By such an arrangement, substantially uniform heating is at-tained within the shell and maximum heat transfer eiciency results. What is more important, however, is the fact that thermal elongation of the various `tubes will tend to become equalized `and no one tube or group of tubes will become appreciably longer than any one other tube or group of tubes at any given instant and for `any given period of heat increase or decrease, for example, during fir-ing of the combustion chamber,

Any lateral displacement of either or both tube sheets 14 and 18 which may take place will thus be a more or less over-all displacement and will result in a gradual and uniform bulging of the tube sheets well within the capabilities of the welds or other sealing means at the tube ends to withstand such displacement.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes 1n the details of construction may be resorted to without departing from the spirit or scope of the invention. For example, while the exemplary form of Scotch marine boiler that is illustrated in the accompanying drawings and described in this specification is of the dual pass type wherein the flue gas collection chamber 60 is disposed at the front end of the boiler shell and wherein there is only one reentry chamber Z4, the liquid distribution Ssystem of the present invenltion is equally applicable to a Scotch marine boiler of the triple pass type wherein the collection chamber is disposed at the rear of the boiler shell and wherein a second reentry chamber is disposed at the front end of the boiler shell and the ue gases are caused to make a third pass rearwardly through the tube bundle 50 before leaving the tube section of the shell. Additionally, although the cross sectional shape of the -distribution manifold 80 and of the collection manifold 82 has been shown and described herein as being semi-circular, other shapes of trough-like conguration are contemplated. The only critical factor associated with the distribution manifold 80 is the disposition of the two rows of holes 90 wherein the holes are so positioned that they will direct their jets or streams of liquid upwardly against ythe wall of the furnace tube 38 on opposite sides of a central longitudinal vertical plane so as to attain the aforementioned divided flow of liquid around the furnace tube 38. Therefore, only insofar as the invention has particularly been pointed out in the accompanying claims is the same to be limited.

Having thus described the invention what we claim as new and desire to secure by Letters Patent is:

1. A Scotch marine re Itube boiler adapted for liquid phase heating and comprising a horizontally disposed cyilndrical boiler shell, front and rear spaced tube sheets disposed within said shell at the opposite end regions thereof and establishing therebetween a liquid phase tube section within the shell, a relatively large diameter furnace tube extending between the tube sheets and having its opposite ends secured in the tube sheets, a bundle of relatively small diameter reentry tubes partially encompassing said furnace tube, extending between the tube sheets and having the individual tubes thereof secured in the tube sheets, a burner positioned at the front end of the shell for firing into the forward end of the furnace tube, a reentry chamber at the rear of the shell for directing the products of combustion issuing from the rear end of the furnace tube into the rear ends of the reentry tubes, the tube section of said shell being provided with an inlet opening in communication with the bottom of the tube section of the shell directly below the furnace tube and with an outlet opening in communication with the top of the tube section of the shell directly above the furnace tube, an elongated tubular distribution manifold disposed entirely within the cylindrical confines of the tube section .of the shell and in communication with the liquid inlet opening, said distribution manifold nnderlying the furnace tube and extending from a region adjacent to one of said tube sheets to a region adjacent to the other tube sheet and in a direction parallel to the furnace tube, said distribution manifold being provide-d with two rows of longitudinally spaced holes therein, the rows being disposed on opposite sides of the central vertical plane of the furnace tube and the holes of the two rows being arranged to direct jets of liquid against the underneath side of the furnace tube on opposite sides of said central plane whereby a divided flow of liquid upwardly around the furnace tube will take place uniformly at all longitudinal regions of the tube section of the shell, and an elongated tubular collection manifold disposed entirely within the cylindrical confines of said tube section of the shell and in communication with said liquid outlet opening, said collection manifold overlying the bundle of reentry tubes and extending from a region adjacent to one of said tube sheets to a region adjacent to the other tube sheet in the longitudinal direction of the shell, said collection manifold being provided with a longitudinally extending -row of spaced liquid entrance holes therein.

2. A Scotch marine re tube boiler `as set forth in claim 1 and wherein said inlet opening is in communication with the bottom of the tube section of the shell suhstantially centrally between the tube sheets, and wherein said outlet opening is in communication with the top of the tube section of the shell substantially centrally between the tube sheets.

3. A Scotch marine re tube boiler as set forth in claim 1 and wherein the longitudinally extending row of spaced liquid entrance holes in the collection manifold is disposed at the bottom of the latter manifold and at a level appreciably below the top of the tube section of the shell.

4. A Scotch marine lire tube boiler as set forth in claim 3 and including, additionally, means establishing a gas bleed opening in the top of the tube section of the shell above the level of said row of spaced liquid entrance holes.

5. A Scotch marine re tube boiler as set forth in claim 1, wherein said inlet opening is in communication with the bottom of the tube section of the shell substantially centrally between the tube sheets, wherein the outlet opening is in communication with the top of the tube section of the shell substantially centrally between the tube sheets, and wherein the longitudinally extending row of spaced liquid holes in the collection manifold is disposed at the bottom of the latter manifold and at a level appreciably below the top of the tube section of the shell.

6. A Scotch marine re tube boiler adapted for liquid phase heating and comprising a horizontally disposed cylindrical boiler shell, front and rear spaced tube sheets disposed within said shell at the opposite end regions thereof and establishing therebetween a liquid phase tube section within the shell, a relatively large diameter furnace tube extending between the tube sheets and having its opposite ends secured in the tube sheets, a bundle of relatively small diameter reentry tubes partially encompassing said furnace tube, extending between the tube sheets and having the individual tubes thereof secured in the tube sheets, a burner positioned at the vfront end of the shell for firing into the forward end of the furnace tube, a reentry chamber at the rear of the shell for directing the products of combustion issuing from the rear end of the furnace tube into the rear ends of the reentry tubes, the tube section of said shell being provided with an inlet opening in communication with the bottom of the tube section of the shell directly below the furnace tube and with an outlet opening in cornmunication with the top of the tube section of the shell directly above the furnace tube, an elongated inverted trough-like distribution manifold, underlying the furnace tube, in sealing engagement with the inside surface of the shell, in communication with the liquid inlet opening, and extending from a region adjacent to one of said tube sheets to a region adjacent to the other tube sheet and in a direction parallel to said furnace tube, said distribution manifold being provided with two rows of longitudinally spaced holes therein, the rows being disposed on opposite sides of the central vertical plane of the furnace tube and the holes of the two rows being arranged to direct jets of liquid against the underneath side 4of said furnace tube on opposite sides of said central plane whereby a divided flow of liquid upwardly around the furnace tube will take place uniformly at all longitudinal regions of the tube section of the shell, and an elongated upright trough-like collection manifold overlying the bundle of reentry tubes, in sealing engagement with the inside surface of the shell, in communication with Athe liquid outlet opening, and extending from a region adjacent to one of said tube sheets to a region adjacent to the other tube sheet, said collection manifold being provided with a longitudinally extending row of spaced liquid entrance holes therein.

7. A Scotch marine fire tube boiler as set forth in claim 6 and wherein the longitudinally extending row of spaced liquid entrance holes in the collection manifold is disposed at the bottom of the latter manifold and at a level appreciably below the top of the tube section of the shell.

8. A Scotch marine lire tube boiler as set forth in claim 6 and wherein the longitudinally extending row of spaced liquid entrance holes in the collection manifold is disposed at the bottom of the latter manifold and at a level appreciably below the top Of the tube section of the shell, and said inlet opening and said outlet opening are disposed medially between the tube sheets.

References Cited by the Examiner UNITED STATES PATENTS 456,923 7/1891 Barnstead 165-160 1,139,334 5/1915 Bray 122-41() 2,387,883 10/1945 Dake 122-136 2,892,451 6/1959 Brown et al. 122-406X 3,171,388 3/1965 Ganz l22--l49 FREDERICK L. MATTESON, J R., Primary Examiner.

Claims (1)

1. A SCOTCH MARINE FIRE TUBE BOILER ADAPTED FOR LIQUID PHASE HEATING AND COMPRISING A HORIZONTALLY DISPOSED CYLINDRICAL BOILER SHELL, FRONT AND REAR SPACED TUBE SHEETS DISPOSED WITHIN SAID SHELL AT THE OPPOSITE END REGIONS THEREOF AND ESTABLISHING THEREBETWEEN A LIQUID PHASE TUBE SECTION WITHIN THE SHELL, A RELATIVELY LARGE DIAMETER FURNACE TUBE EXTENDING BETWEEN THE TUBE SHEETS AND HAVING ITS OPPOSITE ENDS SECURED IN THE TUBE SHEETS, A BUNDLE OF RELATIVELY SMALL DIAMETER REENTRY TUBES PARTIALLY ENCOMPASSING SAID FURNACE TUBE, EXTENDING BETWEEN THE TUBE SHEETS AND HAVING THE INDIVIDUAL TUBES THEREOF SECURED IN THE TUBE SHEETS, A BURNER POSITIONED AT THE FRONT END OF THE SHELL FOR FIRING INTO THE FORWARD END OF THE FURNACE TUBE, A REENTRY CHAMBER AT THE REAR OF THE SHELL FOR DIRECTING THE PRODUCTS OF COMBUSTION ISSUING FROM THE REAR END OF THE FURNACE TUBE INTO THE REAR ENDS OF THE REENTRY TUBES, THE TUBE SECTION OF SAID SHELL BEING PROVIDED WITH AN INLET OPENING IN COMMUNICATION WIH THE BOTTOM OF THE TUBE SECTION OF THE SHELL DIRECTLY BELOW THE FURNACE TUBE AND WITH AN OUTLET OPENING IN COMMUNICATION WITH THE TOP OF THE TUBE SECTION OF THE SHELL DIRECTLY ABOVE THE FURNACE TUBE, AN ELONGATED TUBULAR DISTRIBUTION MANIFOLD DISPOSED ENTIRELY WITHIN THE CYLINDRICAL CONFINES OF THE TUBE SECTION OF THE SHELL AND IN COMMUNICATION WITH THE LIQUID INLET OPENING, SAID DISTRIBUTION MANIFOLD UNDERLYING THE FURNACE TUBE AND EXTENDING FROM A REGION

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