US2104937A - Boiler superheater - Google Patents

Description

Jall- 11, 19358l c. s. TURNER BOILER SUPERHEATE'R Filed sept. fr, 1934 5 Sheets-Sheet l O O O o O 6 O O O O G o O G Nv n o o .w N 4 I/IM Uilm 9@ |17 BY JM( a www?? l y ATTOR EYS.

Jan. 11, 1938. C 5 TURNER l 2,104,937

BOILER SUPERHEATER Filed Sept. 7, 1934 3 Sheets-Shawl 2 6/ INVENTOR.

@arl's if/rmer" Jan. 11, 1938. c. s. TURNER BOILER SUPERHEATER Filed Sept. 7, 1934 3 Sheets-Sheet 3 Cil Patented Jan. 11, 1938 ATENT OFFICE BOILER SUPERHEATER Charles S. Turner, Detroit, Mich.

Application September 7, 1934, Serial No. 743,068

8 Claims.

This invention relates to boiler superheaters, and incorporates amo-ng its particular objects improvement of superheaters of the varieties disclosed in my copending applications Serial Nos.

;. 496,868, filed November 20, 1930, Superheater construction; 512,675, led January 31, 1931, Superheater construction; 534,490, filed May 2, 1931, Fluid cooled superheatei` construction; 590,108, led February 1, 1932, Superheater asl'. sembly; and 699,541, led November 24, 1933,

Superheater construction.

A further aim of the present invention is to provide an improved superheater particularly suited for installation in fire tube boilers of the .f locomotive type. It has been the common practice, in the installation of superheaters in such boilers, to place superheating elements in certain of the lire tubes, which are enlarged to receive them. Such superheaters work by convection,

and since they are not exposed to radiant heat,

and since the rate of possible heat absorption is very much less when convection is relied upon, a relatively very large superheating surface must be used, and this method of installing the superheater elements accordingly detracts from the efciency of the boiler by unduly reducing the number of re tubes eiective to assist in steam` generation. My invention therefore also comprehends so installing a superheater in such boilers as to offer no material obstruction to or reduction ofthe effective number of re tubes.

Still another object is the development of a superheater installation having an active portion disposed directly within the fire box of such a fire i. tube boiler at a point subjecting it to radiant heat at a relatively higher temperature than the tubes could withstand if empty, and the componentY units of which are so operated and designed as to be guarded against damage by overheating when empty of steam.

Still further my present invention aims to so arrange a water cooled superheater within the fire box of a re tube boiler as to provide a support for baffling means calculated to increase the length of the path of gases of combustion andv flame travel, and to replace or partly replace the conventional water tubes now ordinarily employed for that purpose.

Yet another object is the provision of an improved structural arrangement of such a superheater in a re tube boiler, in which the component superheater elements project through leg Vwaiter walls of the boiler which form the re box, yet are so arranged as to reinforce and strengthen .j the leg walls.

A further object contemplated by this invention is the provision of a novel water-regulated radiant superheater adapted for use in locomotive boilers and of very compact construction, in which no steam inlet connections to the superheater or discharge connections for the cooling water channels, or headers for these portions, need be located outside the boiler itself, and in which the superheated steam is discharged at a point so close to its destination as to enable the use of even shorter steam pipes than are em.- ployed in a non-superheated locomotive boiler.

Other objects and advantages will be apparent from the following description, wherein reference is made to the accompanying drawings illustrating preferred embodiments of my invention and wherein similar reference numerals designate similar parts throughout the several views.

In the drawings:

Figure l is a somewhat simplified and diagrammatic vertical section of the fire boX and adjacent rear portions of a re tube locomotive boiler, showing an illustrative installation of one of my improved water regulated superheaters.

Figure 2 is a plan view of the superheater assembly, taken substantially on the line 2 2 of Figure l and looking in the direction of the arrows, partly broken away and with the boiler and baiiling arch portions omitted to aord a better view of the superheater.

Figure 3 is an enlarged transverse section of a header and the extremities of one tube assembly, taken substantially on the line 3 3 of Figure 2 and looking in the direction of the arrows.

Figure 4 is a cross section of a tube assembly taken substantially on the line 4 4 of Figure 2 and looking in the direction of the arrows.

Figure 5 is a longitudinal sectional elevation of a locomotive boiler construction equipped with a superheater incorporating my invention in somewhat modied form.

Figure 6 is a horizontal detail section taken substantially on the line 6 6 of Figure 5 and looking in the direction of the arrows, and

Figure 7 is a view similar to Figure 4 of a modied tube assembly.

Referring now to the drawings, and particularly first to Figure 1, which will be seen to illustrate somewhat conventionally the rear portions of a locomotive boiler typical in many respects, reference character I 0 designates the main shell, from which the crown sheet I2 is supported in the usual or any desired manner, as by crown stays I 4, to define a re box I5. Forwardly from the fire box projects the main boiler section I6, con- 2 taining ire tubes, as Il, while leg Walls, as 20-2 I jacket the re box, the leg 2t constituting a downward extension of the front Wall, while the leg 2| defines the rear wall of the iire box; all in known manner.

It is desirable'that a baiing arch, as 2l2, of re brick or the like, be supported in such position within the fire box as to force the burning and burned gases to double back and pass therearound. Such arches' have in the past been carried by water cooled supports constituting water tubes connected to the iront and rear leg walls and serving to assist in steam generation. Steam generated in such water tubes, of which there are ordinarily not more than five or six, is delivered, in the conventional constructions referred to, into the main boiler I6, and collected with the remainder of the steam developed in the boiler in a steam dome as 25, whence it was either conducted through a dry pipe andto the cylinders or delivered to a superheater of one of the types previously used, ordinarily housed within certain of the fire tubes, as stated.

In carrying out my invention` I replace both of the usual elements last discussed, that is the superheater units within the fire tubes and the water tube arch supports, by water regulated superheater assemblies each consisting of a central Water conduit portion 30 and a plurality of circumferentially disposed steam tubes 313 assembled and contoured in the manner indicated in Figures 2, 3 and 4. As shown in Figures 3 and 4, the central water tube 3B is preferably provided with a smoothly cylindrical interior surface to facilitate cleaning, while its external surface is provided with flutes defined by radially projecting ribs 35. The ribs are preferably helically disposed about Vthe exterior of the tube as shown in Figures 1 and 2, and the channels between the ribs are curved conformably to the radius of the steam tubes 33, which are tted thereinto and welded in place, as at 36.

-A plurality of such water cooled superheater conduit assemblies, five being shown, are extended across the rire box, preferably from front to back and at an angle to the horizontal, each assembly being projected through a bushing, as 40,

extending through and `flanged on 'either side of one of the leg walls 22l to seal it therein. The bushings 40 and their lsecuring and sealing flanges are preferably sufficiently heavy to materially strengthen and reinforce `the plates forming the jacket walls, thus not only compensating for the weakening eifect of the apertures through which the tube assemblies project, but serving as reinforcing elements similar in action to 'staybolts. The assemblies may be slidable in the bushings to provide for expansion and contraction.

The ends of the tube assemblies project beyond the leg walls and into transverse front and rear header assemblies 42-44 and 42'-44' respectively. The steam header portions 42-42 are shown as of rectangular section, as indicated in Figure 3, and apertured along their facing Walls to receive the open ends of the steam tubes 33 as well as the central water tube of each element. To the vcentral water tube 3D of each element a projected extension 3l is 'attached which extends across and through the opposite wall of the steam header, in which it is'of course sealed, and opens into a water header 44 or 44 shown las 'carried by vthe wall of 'the steam header and formed of a half tube extending along the-outsideV of the farther wall and over the open ends of the extensions 3l, so that the latter open thereinto, the water header being welded to the steam header along its edges as at 45 to form a semi-cylindrical enclosure. Steam header 42 constitutes the inlet for Ysteam to be superheated, which is delivered thereinto through a dry pipe lill from the steam dome 25. The dry pipe may, as shown, beV projected through the boiler between the main shell and the crown sheet and connected to the steam inlet header 42 at the rear of the boiler. The cooling water is preferably fed to the assembly through a take off pipe til, tapped into the bottom of the boiler and connected to Water inlet header 44, while the offtake 48 delivers water and steam generated in the water tubes from outlet Water header 44 to the boiler, within and near the top `of which it discharges, as shown in `Figure l. From the steam outlet header 42 a pipe, as 5i), may conduct the superheated steam to the cylinders (not shown) or other destination.

The inflow of cooling vwater is preferably throttled by means of an inlet valve, as 52, adapted to so regulate the admission of Water that the effective level thereof may be held at any desired reduced point Within the .zone of heating. Preferably 'thermostatic ,controlling means as 55 is Aprovided connected to the valve, as by conduit 54, and arranged to open the valve and so raise the water level upon a rise of superheated steam temperature above a desired point, and close the valve to depress the level upon a fall of such temperature. Preferably a manually operable bypass is arranged around the thermostatic valve, as at 59, so that when no steam is flowing to control the thermostatic valve the Water tubes may nevertheless be flooded, to protect the dry steam tubes, by opening the hand bypass. It will be obvious that the mechanical arrangement of these and other lparts may be varied in many ways. It will also be understood that the generation of steam within the Water tubes 30 in combination with the throttled inlet makes possible maintenance of a depressed level. That is to say, while the presence of rising steam bubbles ofl increasing size involves the presence of entrained water throughout ordinarily the full height of each tube, so that the level may not be a 'sharply defined one, and some heat absorbing power arising from the presence of Water may exist all the Way to the top, there is neverthe less a definite and controllable though gradual reduction of heat absorbing capacity from the bottom to the top of the active portion of the pipe, and such a throttling of the Water inlet that gravity in effect maintains a reduced level in the water tubes. The presence'of some entrained water all the way to the top of the tubes, however, is a valuable safety factor under extremeV conditions, as it is sufficient to safeguard 'the tube. Y

VIt will be understood that the throttle valve 152 actually constitutes an expansion valve, since below it the pressure is greater than above by reason of the head of water in the boiler, the pressure in the steam tubes of the superheating elements above the valve being less by reason of the reduced quantity of liquid, and the free evaporation of suchy liquid which there takes place. By reason of such free vaporization of the throttled quantity of water, only gravity tends to -hold the 'water in the bottoms of the steam channels. A sharply defined water level is thus avoided, and the presence of some entrained iwater throughout the steam tubes assured by the rising bubbles of the rapidly boiling Water.

' Preferably a continuously rising gradient obtains throughout each water channel from its inlet until the discharge is reached; that is to say that while a downward discharge may be used, there are no return bends providing rising gradients after a falling gradient, and all possibility of water traps and steam pockets is thus eliminated.

Upon an inspection of Figure 4 it will be seen that the welded areas 36 form the only integral metallic connection between the water and steam tubes 35i-33, and therefore the only heat bridge through which any rapid heat transference can take place. The heat-bridging welds 3% will be seen to be arranged at the surface of the assembly in such fashion as to assist in the conduction of heat to the steam within tubes 33 in sections of the assembly containing virtually no water in central tube 3D, while Where or when water is present in the central tube, the tendency of heat to flow to the coldest object and the relative physical lengths of the heat paths between the steam and the outside of the assembly on the one hand, and the water and the outside of the assembly on the other, renders the latter path shorter than the former in terms of ease of heat flow, so that heat is removed from the outside of the assembly before it can reach the steam, and the walls of the steam channels are prevented from rising above a desired temperature. Because of the absence of a direct integral radial bridge between the water and steam channels, however, water and saturated steam in the former channel cannot desuperheat the steam in the latter by absorption directly through the walls. The methods of calculation of rates of heat transference and relative lengths of heat paths in proportion to relative temperatures, being well understood in the art, they need not be set forth here, the important consideration being the proportioning of the fins 35 and positioning of the welds 3E in such manner that despite the outer disposition of the steam channels, the water takes the excess heat from the outside Walls when and Where present in substantial amounts, (and not merely entrained with bubbles) thereby preventing the heat from reaching the steam and guarding against over superheating in such areas. Generally speaking, therefore, the active portion of the superheater is only that above the effective water level, while the parts are so proportioned that below such level substantial equilibrium is maintained, so that steam passing downwardly therethrough is not desuperheated, although it cannot obtain more heat to be additionally superheated. To preserve equilibrium and prevent desuperheating outside the zone of heat absorption, the welded joints 35 are preferably terminated at the boundary of the Zone of heating, as indicated in Figure l at 35.

In Figures 5, 6 and 7 a somewhat modied arrangement is shown in which no steam inlet or Water tube outlet headers, or other connections, need be arranged within the cab, and wherein saturated steam is delivered to the superheater directly at the dome and within the boiler, while the water tubes also terminate and discharge within this portion of the boiler. In this construction the superheated steam discharge is at the smoke box end of the boiler and close to the steam chestsso that long delivery pipes are also unnecessary.

, The superheater umts are shown formed of a spiraled assembly of integrated steam tubes 33a and a central Water channel portion which is in this instance fabricated of a plurality of channeled plates 30a curved conformably to the tubes 33a and extended sufficiently far to project between and space apart each two adjacent steam tubes and provide exposed edges adapted to be secured by the same welds 36m which secure the tubes. The plates 30a, by Virtue of their Welded integration with the surface of the assembly serve to conduct heat directly from the outside to the water where present on the one hand and on the other hand to so greatly restrict as to virtually prevent direct heat conduction between the steam and water conduits by reason of the insulating eect of the schisms or planes of cleavage bctween the plates and tubes. The operation and characteristics of the assembly may be substantially the same as those of the form first described and shown cross sectionally in Figure 4.

The lire tubes of a lower bank, as lla, are formed large enough to receive the forward ends of the units, which are extended therethrough and project into the smoke box 6B near the bottom thereof. The section of each unit which projects rearwardly into the fire box l5a from the bulkhead 6| is disposed at such angle as to properly Support the balliing arch 22a, and is y looped around the rear edge of the arch and again projected forwardly through the bulkhead 6| near the top thereof. Each unit so projected through the bulkhead may be sealed therein, as by means of the sleeve 11, to which it is Welded, while the looped U-sections preferably terminate just inside the bulkhead, at which point each is coupled to an extension as 'I8 serving to connect it to headers 42h-Mb, the former constituting the steam inlet header and the latter the water tube discharge header. The headers 42h-44h may be assembled in a manner generally similar to the headers l2-44 previously described, and similarly connected to the component tubes of the extensions 'i8 of the superheater units. The header assembly is preferably located at a high point, partly or entirely within the dome 25a, as shown, and the inlet to the steam header may be controllable by the throttle valve I0 of the engine. The tubes of the extension '18 need not be spiraled since the considerations which motivate the spiraling within the rebox (i e., equal absorption of radiant heat) are here not present. The discharge from the water tubes 3Q may be through one or more outlet pipes as 38h emerging from outlet header 4b and bent downwardly to discharge above the water level in such manner as to both guard against the splashing or surging of water into the water tubes and prevent the discharge of saturated steam and entrained water into the dome.

'Ihe forward extremity of each superheater unit is connected to a header assembly comprising steam outlet and water inlet headers 32a-34a respectively, shown as arranged within the smoke box 60. The water header 44a through which the water tubes 30a of the superheater units are supplied with water from the boiler is directly connected to the forward end of the boiler by water inlet pipe 41a., while the ow through the latter and so the effective level in the Water tubes is controllable by an inlet valve 52a, by which the Water supply may be throttled. The operation of this valve may be similarly controlled thermostatically in response to the temperature of superheated steam, as by the thermostatic means diagrammatically illustrated at 54a, while a hand operated bypass may be provided for like reasons, as at 59a. From the header 42a the superheated steam may be conducted directly to the steam chests through steam pipes 15, shown as extending within the smoke-box, though this is of course entirelyoptional, and outside connections might be used if desired.

In this construction also the steam is made to flow downwardly through the units during superheatng, saturated steam being collected from the drum directly at the throttle valve port in the dome, Which serves as a take-off and is directly connected to the inlet header 66, by which it is shown as carried. The only access to the superheater tubes 33 is thus arranged Well above the water level and within the steam dome in a position eectively guarded against splashing.

The bridging welds 36a are preferably provided only within the zone of radiant heat absorption, and terminate substantially at the boundary of such zone. This is particularly important at the outlet end of the assembly to prevent desuperheating of the steam. At the upper end of the assembly the termination of such welds is of course a matter of no consequence, since the steam and water tubes are here at substantially the same temperature. At the lower end of the assembly the line of termination of the bridging welds is designated 36o.

The operation of this form of my invention will be seen to be quite similar to that previously described. The admission of water to the steam channels is so controlled as to hold the water .at reduced eifeotive level, vand to vary the `effective superheating surface, while the design of 'the tubes is such as to perform the interprotective function previously discussed.

It will be understood that the lower ends of the looped units might be projected through the water leg 20a after the manner of the rst embodiment, if desired, and that the continuation thereof through the lower flues I'la, while affording some additional heat absorption, is of convenience particularly because affording delivery of steam at a point close to the chests. The ilues Ila, or if desired only the units Within them, may be inclined upwardly somewhat to insure the proper flow of steam generated in the water tubes. If the superheater units are grouped so closely in order to enable them to pass through a lower portion of the generally cylindrical boiler that they do not bridge the full Width of the firebox, additional support for the arch 22a may be furnished by simple water tubes as 23 arranged therebeside and connected at their forward ends to the boiler or front leg 20a and at their rear ends to back leg `2 la.

Although I have shown and discussed a crosssectional arrangement of steam and water tubes which I regard -as preferable, it will be understood that changes may be made without departure from the spirit of the invention, which is to be limited only by the scope of the subjoined claims. `Under extremely high ratings, for ex-v ample, it might be advisable to run the steam through the inner tube and the water throughV 1. In a locomotive construction, in combination with a iire tube boiler having a i'lrebox at one end and a smoke box at the other and including re tubes connecting said rebox and smoke box, said boiler also being provided with a collecting dome for saturated steam Vlocated above the Water level, a superheater assembly comprising integrated steamV and Water conduit portions looped through the rebox and terminating at their upper extremities appurtenant the dome, said steam conduit portions having inlet means within the dome, the water conduit portions having chscharge portions above the water level, at least the steam conduit portions oi said assembly extending through the re tube portion of the boiler and having discharge portions` appurtenant the smoke box, and controllable water inlet means for the lower ends of the water conduit portions.

2. In a locomotive construction, in combination with a fire tube boiler having a rebox at one end and a smoke box at the other and including iire tubes connecting said fire box and smoke box, said boiler also being provide-d with a dome located above the water level for collecting saturated steam, a superheater assembly comprising integrated steam and water conduits terminating at their upper extremities appurtenant the dome, the steam conduit portion having an inlet within the dome.

3. In combination with a firetuoe boiler having a rebox portion and having a collecting dome for saturated steam, a water regulated radiant superheater assembly comprising integrated steam and Water conduits extending through the fire box portion and to a position appurtenant said dome, the steam conduit portions having an inlet Within the dome.

fi. In combination With a nre tube boiler having a rebox portion and having a collecting dome for saturated steam located above the Water level in the boiler, a water-regulated radiant superheater assembly comprising integrated steam and water conduits extending through the rebox portion and to a position appurtenant said dome, the steam conduit portions having an inlet Within the dome and the water conduit portions having an outlet also arranged above the water level.

5. In combination with a re tube boiler having va rebox portion and having Va collecting dome for saturated steam located above the Water level in the boiler, a water-regulated radiant superheater assembly comprising steam andA water conduits having metallically integral portions extending through the rebox and being extended from said rebox through the boiler portion and at least a portion of said assemblybeing projected into the dome, said steam conduit portions having an inlet within the dome, and the Water con-duit portions having an outlet also located above the water level.

6. In combination with a re box and a fire tube boiler including water containing portions defining Wall portions ofY the fire box, and reV tubes extending from said re box through one of the water containing portions, steam collecting means for said boiler arranged above the water level therein, and a superheater comprising a plurality of assemblies of water and steam tubes, said tubes of each assembly being arranged for ready heat transference with one another, extending from said water-containing, and wall portions and through said re box, the water tubes of said assemblies being regulably Yconnected to a water-containing portion of the boiler and the steam tubes Athereof extending through 8. A superheater construction as set forth in claim 6 in which the water and steam tubes of said assemblies are helically intercoiled and integrally connected, and in which said fire box has a bafng arch supported by said assemblies.

CHARLES S. TURNER.

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