US2034547A - Three drum boiler - Google Patents

Description

rch 17, 1936. A. u. WETHERBEE I 7 r THREE DRUM BOILER Original Filed Feb. 25, 1929 '4 Sheets-Sheet l 42 a6 a u H W/ 5: i. E %j7; 7 a4 33 E ch 17,1936. A. u. WETHERBEE 2,034,547

THREE DRUM BOILER Original Filed Feb. 25, 1929 4 Sheets-Sheet 2 March 17, 1936. u WETHERBEE 2,034,547

THREE DRUM BOILER Original Filed Feb. 25, 1929 4 Sheets-Sheet 3 March 17, 1936. A. u. WETHERBEE THREE DRUM BOILER 4 Sheets-Sheet 4 Original F iled Feb. 25, 1929 M MH H N ll lllll lliiliilll v M y Patented Mar. 17, 1936 Ashur U. Wetherbee, Evanston, Ill.

Continuation of application Serial Nb. 342,506, February 25, 1929. Thisapplication August 29, i952, Serial No. 630,927. Renewed February 7,

6 Claims.

This invention relates to boilers, and more particularly to boilers employing a plurality of drums connected in a ring circuit.

I have illustrated my invention, by way of ex- 5 ample, as applied to a boiler comprising three drums connected in a ring circuit. Though my invention is particularly adapted for a three drum boiler, it may be applied, in its. broader aspects, to boilers using more than three drums as will be understood by those skilled in the art, and. I do not, therefore, limit my invention to three drum boilers only.

One of the main objects of my invention is to provide a boiler of comparatively simple and inexpensive construction, and improved baflle means therefor, particularly improved bafile means which will permit expansion and contraction of the boiler tubes without undesirable stresses upon the battle means.

Figure 1 is a vertical central sectional view of ,a boiler constructed in accordance with my invention as applied, taken from front to back of the casing with parts in elevation;

Figure 2 is a section taken substantially on line 2 2 of Figure 1;

Figure 3 is a fragmentary sectional view adjacent one end of the water and steam drum, and associated parts, illustrating the manner of mounting the drum for sliding movement, with parts in elevation;

Figure 4 is a view similar to Figure 1, showing a modified form of boiler;

Figure 5 is a view similar to Figure 4, showing a second modification;

Figure 6 is a detail, on an enlarged scale, of the holding means for the central bafile.

This application is a continuation of my application for Three drum boiler, Serial No. 342,506, filed February 25, 1929.

In Figure 1 of the drawings I have illustrated my boiler as mounted in a casing which is reenforced by a frame 2 formed of structural steel. The frame and the casing are, in general, of known construction and need not be illustrated nor described in detail. The casing includes a furnace 3 at the rear of which is a fire wall 4 disposed in spaced relation to the back wall of the casing, the space 5 above the grate 6 constituting the combustion space of the furnace.

The boiler is mounted in casing l at the upper portion thereof. Frame 2 comprises two main side supporting beams l of I cross section. The boiler comprises an upper steam and water drum 8 disposedadjacent the back wall of the casing, alower ,mud drum 9 also disposed adjacent the back wall of the casing, and a water drum l0 disposed between drums 8 and 9 and at the front wall of the casing. These drums are connected together in a ring circuit by banks of tubes ll, I2 and I3. The tubes are bent and enter the 'drums radially thereof, in a manner well known in the art. Drum 8 is provided with a steam nozzle I l and associated dry pipe 15. This drum is also provided with suitable baffles adjacent to dry pipe '15 and'feed water pipe 16, respectively, 9

theilatter pipe extending along the drum 8 at the lower portion thereof for supplying feed waterto the drum in a known manner. The tubes vI I constitute thedowncomers, certain tubes conducting" more feed water than other tubes, the tubes l2 constitute the upgoers for the upward flow of steam and water therethrough at relatively high speed, and the bank of tubes l3 also constitute upflowtubes for conducting the steam and water, from drum Ill to drum 8 in which the steam is liberated.

The water drum It is anchored to the under faces of beams 1 in a suitable manner, as by means of brackets I? suitably secured to the heads of the drum, these brackets being riveted 2 or otherwise'suitably secured to beams l. The .water drum extends into a suitable recess formed inthe front wall of the casing, and the space between this drum and the front wall is sealed with a suitable packing material I8, such as asbestos 3 or magnesium. .The ends of the drum Ill extend into's'uitable openings l9 through the side walls of the casing and packing rings 20 of as- .bestos or magnesiumv close the spaces between the end portions of the drum and the surround- 5 ing walls of the openings I9. If desired, suit- I able closures for these openings may be provided, "as is known in the art.

vDrum..8 is seated, at each end, in a block or shoe 2| which is slidably mounted on the upper. face of beam 1. This shoe is disposed between rivets 22 and the outer face of the side wall of the casing, which is recessed to accommodate the shoe. At its ends drum .8 extends through suitable openings through the side walls of the casing and each end portion of the drum is provided with a covering 23 of heat insulating material, such material also possessing appreciable resiliency and extending between the drum and the surrounding wall of the opening through which the drum extends so as to form a closure therebetween. Magnesium is suitable for this purpose, though I preferably use asbestos in a highly fibrous form which will facilitate sliding ,movernent of the drum 8 on the beam 1 while,

maintaining a proper closure between the drum and the casing. An arch 24 extends over the upper portion of the drum 8 and is provided with an opening to accommodate the nozzle I4, this opening being of appreciably greater extent than the nozzle to permit the sliding movement of drum 8 referred to. The top of the casing is closed by a suitable roof structure 25 supported by T-bars 28 extending across the casing and suitably secured to frame 2.

Mud drum 9 extends into a recess at the upper edge of bridge wall 4, the space between this wall and the drum being sealed by a packing 2! of suitable material, such as asbestos. The ends of this drum extend into openings 28 through the side walls of the casing. Packing rings 29 of suitable refractory material are disposed about the ends of the drum and form a seal between the same and the surrounding wall of the openings 23. I preferably employ asbestos in a highly fibrous condition for the packing 29, though any other suitable material which possesses sufficient resiliency to permit appreciable movement of the mud drum may be used.

A baffle 39 formed of slabs or tiles of suitable refractory material, is supported upon the upper tubes of the bank of tubes l2 and extends upwardly from the mud drum 9 for approximately one-half the length of the tubes. An upper baffle 3| extends across the bank of tubes 13 from the lower row of tubes thereof to the next to the top row of tubes, this baflle being inclined upwardly and forwardly of the casing. An angle bar 32 is secured to the lower row of tubes of the bank l3 by U-bolts 33, or in any other suitable manner. The vertical flange of this bar fits into a groove 34 formed in the upper edge of a vertical baffle 35, the lower edge of which is rabbeted and seats upon the upper edge of baffle 35. The upper edge of baflle 35 is disposed closely adjacent the lower edge cf baffle 3|, so as to form a closure therewith. Groove 34 is of appreciably greater width and depth than the vertical flange or arm of bar 32 thus permitting movement of baflle 35 relative to the bar. This is of importance as permitting movement of baffle 35 in accordance with expansion and contraction of the bafile 39 and tubes I2, while also permitting relative movement between this baffle and the baffle 3| and tubes l3. In this manner I avoid subjecting the baflie 35 to stresses such as would tend to quickly destroy the baffle. I also provide simple and eflicient means for normally holding the bafile 35 in position while permitting ready removal and replacement thereof as required. This baflle is constructed of slabs or tiles of proper width fitted end to end across the casing to form a suitable barrier or baiile.

The hot products of combustion from the furnace flow upwardly along and across the lower banks of tubes and are then deflected by the baflle 3| forwardly of the casing across the tubes l3, these gases then passing through the space between baffie 3| and roof 25 and flowing downwardly across tubes I3 in a reverse direction, after which the gases flow across and along the tubes II and thence to the chimney opening or outlet 36 of the furnace. 7

It is particularly pointed out that in the boiler construction illustrated, water drum i9 is anchored to the under sides of beam l and the water. and steam drum 8 is slidably mounted upon the upper sides of these beams, the mud drum 9 being tube suspended from the drums 8 and I0 and being free for movement to accommodate expansion and contraction of the tubes II and I2. This provides a simple but highly eificient construction of boiler in which both the water drum and the water and steam drum are effectively supported in such manner as to prevent any tendency toward tipping of the boiler structure while permitting expansion and contraction of the tubes I3, due to the sliding movement of drum 8, as well as the tubes and I2. In this manner I eliminate undesirable stresses due to expansion and contraction of the tubes, such as would be apt to cause, injury to either the tubes or the drums if the drum 8 were not mounted for sliding movement and the mud drum 9 were not capable of movement to accommodate expansion and contraction of tubes l and I2. In the modified form illustrated in Figure 4, the casing |-A is, in the main, of known type but is of somewhat different construction than casing of Figure 1. This casing comprises a back wall 31 and a fire wall 38, the back wall being disposed at the back of the furnace 39. An arch 49 is disposed between the back wall and the fire wall and a series of tubes 4| extend through this arch, these tubes connecting the mud drum 9 to a header 42 at the top'of front wall 43 of furnace 39. A series of tubes 44 connect header 42 to water drum ID, the header 42 being at a lower level than the water drum and the tubes 44 being inclined upwardly and rearwardly of the casing |-A. The tubes 44 alternate with the tubes 4| and provide a suppoiting structure for the roof 45 of the furnace 39, the furnace roof being thus water cooled. The tubes 4| form a slag screen which extends above the fire box in the furnace A. Baflie 46 extends from the arch structure 4|] upwardly and forward ly of the casing to within a short distance of water drum l9. In this form I also employ the baffles 39, 3| and 35, of Figure 1. I also employ a supplemental baffle 41 which extends downwardly from the drum 8 between certain of the tubes II. This supplemental baflle 4'! is also preferably employed in the form of boiler illustrated in Figure 1, as shown, and is suitably secured to certain of the tubes by U-bolts 48 or in any other suitable manner. The hot products of combustion are thus caused to pass downwardly along the tubes and across the lower portion of these tubes and then upwardly along the remaining tubes H to the chimney or outlet opening 3'5, this opening being controlled by a suitable valve or damper 48. The tubes 4| and 44 and the header 42 are included in the circulating system of the boiler and the drum 8 is mounted for sliding movement on the beams I of the frame, mud drum 9 being tube suspended and free for movement to accommodate expansion and contraction of the tubes, as before.

In Figure 5 I have illustrated my invention as applied to a downdraft boiler.

In this form I have illustrated an upper header 49 and a lower header 59 at the front wall 52 of the furnace 5!. These two headers are connected by a pipe 53 to mud drum 9, this pipe entering the mud drum at a sufficient distance above the lower portion thereof to prevent entry of niud or sediment into pipe 53. A series of tubes 54 connect the upper header 49 to drum ID, the header being at a lower level than the drum and the tubes being inclined upwardly and rearwardly of the casing. These tubes 54 support the roof 55 of the furnace, such roof being of any suitable known or preferred construction. An arch 56 connects the front wall of the furnace casing |B with the furnace roof 55. A series of tubes 51 conrelatively staggered and inclined upwardly and rearwardly of the casing providing the upper grate of the furnace, front wall 5| being provided with a suitable opening defined by a door frame 58 for introduction of the fuel. The partly consumed fuel which passes between the tubes 5'! falls upon the lower grate 59, the ashes passing into ash pit 50 of the furnace in a known manner. The casing comprises a back wall 6| at the back of the furnace and a fire wall 62 adjacent the back wall of the casing, associated with the 'mud drum 9 in the manner previously described. A bafie 63 extends downwardly and forwardly of the furnace from water drum ID for a short distance along the tubes 51. A second baffle 64 is supported by the lower tubes of the lower bank and extends along the upper portions of such tubes to within a short distance of the drum II). A baflle 64A extends upwardly and forwardly from mud drum 9 across the space between the upper banks of tubes and the lower banks of tubes and across the tubes of the upper bank to next to the topmost series or rows of such tubes. A baffle 65 extends downwardly from drum 8 between the tubes of the rear bank. The hot products of combustion are thus caused, by the baflies, to pass across the tubes of the respective banks so as to scour the tubes and prevent the formation of a skin or film of gases about the same such as occurs where the gases flow lengthwise of the tubes. In this manner I assure effective heating of the water in the tubes, resulting in circulation of the steam and water at high speed and consequent rapid generation of steam.

As clearly illustrated in Figures 1, 4 and 5, the tubes ll of the bank connecting the steam and water drum and the mud drum, are short relative to the tubes 12 and I3 of the other two banks. This is advantageous as facilitating shipment of the drums and the banks of connecting tubes, as a unit. In such a unit, the tubes l2 and I3 may be made relatively long, so as to be highly effective for heat absorbing purposes which is desirable. The tubes l, which are not disposed over the furnace, do not need to be as highly efiicient for heat absorbing purposes as the tubes of the other two banks and may, therefore, be materially shorter than tubes I2 and I3 without reducing the steam generating efliciency of the boiler to an objectionable degree. By having tubes ll short, these tubes may be made sufficiently rigid and strong mechanically to support the weight of the steam and water drum 8 and the associated tubes IS, without any necessity for special bracing of the drum 8, during shipment of the unit.

Also, by having tubes ll short, the unit has low head room, when placed upon a flat car for shipment, so as to pass readily railway overhead clearances. The structure, consisting of the drums and connecting banks of tubes, is thus particularly well adapted for shipment as a unit upon a flat car, or other suitable vehicle, upon which it may be secured in a suitable manner, with the drum 8 uppermost, and without necessity of providing special bracing for drum 8. Numerous advantages result from constructing the tube and drum unit in this manner. One of the main advantages is that the unit, upon arrival at its destination, may be set as a unit in the casing therefor and withoutthe loss of time which would otherwise be required in properly assembling the drums and tubes. A further advantage is, that the entire unit can be-completely assembled, before shipment, at the factory and under the most efiicientworking conditions,assuring both speed and accuracy in assembly. I thus eliminate the heavy expense of field assembly of the drum and tube structure, and also assure accuracy in assembly, whichis highly important in boiler construction. In shipping the unit, it isv preferably disposed with the drum 8 above drum 9, though this position may be reversed, i. e., the unit may be disposed with drum 9 above drum 8. In either case, the short rigid tubes II serve to support the upper drum and a portion of the weight of the tubes connecting this upper drum to the water drum I0.

When the boiler is disposed upon a flat car for shipment in the manner above referred to, the inner rows of tubes of the bank of tubes ll support the main portion of the weight of the upper drum and the upper bank of tubes connected thereto. These tubes function efficiently and safely to support the upper drum and associated tubes. They possess sufiicient strength and rigidity to support the load under conditions encountered in shipment and come within a definite slenderness ratio. ratio of a tube is determined by the formula in which L equals the length of the tube and'R equals the radius of gyration. The slenderness ratio formula of The National Tube Company, for tubes supporting a static load, is

However, in the case of a boiler in transit, shipped by railway, the load is far from static. Due to impact, sudden stops and starts, vibration, and inertia, the tubes supporting the weight of the upper drum and associated parts are subjected to sudden and severe transverse stresses. In order to have proper strength and rigidity to en.- dure these stresses safely and surely, the shortest tubes of the rear bank should come within a slenderness ratio in which the value of is much lower than in the case of a static load. The slenderness ratio for these tubes should be at least as low as and preferably as low as The radius of gyration of a tube is determined by its wall thickness and exterior diameter. In water tube boilers, such as those disclosed herein, the lightest permissible wall thickness of the tubes is eleven gauge and the exterior diameter of the tubes is three and one-quarter inches. The radius of gyration for a tube of this wall thickness and exterior diameter is 1.1074 inches. By the formula a tube of the wall thickness and the exterior diameter stated would have a length of 6.459 feet. -75

In constructing a boiler in accordance with the formula -8O V the maximum permissible ratio of the length to the exterior diameter, of the shortest tubes connecting the mud drum and the steam and water drum, is approximately 27:1. If the preferred formula of is used, this ratio is reduced to approximately 24:1.

In the boiler illustrated in Figures 1 and 5, the ratio of the length to the exterior diameter, of the shortest tubes connecting the mud drum and the steam and water drum, is approximately 16:1, and in Figure 4 this ratio is approximately 18: 1. It will thus be seen that in all of the forms of my boiler illustrated, the shortest tubes of the rear bank come well within the formula and also well within the formula these tubes in each instance being materially shorter than required by either formula, though the length of these tubes may be greater in certain cases. and where required, provided such length does not exceed the maximum permitted by the formula This assures that these tubes are of sufficient strength and rigidity to support the weight of the upper drum and associated upper bank of tubes, when subjected to sudden stops and starts and vibration, which is of primary importance in shipping a boiler by railway in completely assembled condition and as a unit. A further important advantage of having the shortest tubes of the rear bank of a slenderness ratio within the formulae stated, with the preferred ratio of the length of these tubes to their outside diameter approximately 18:1, is that it renders possible a boiler capable of developing several hundred horse power when operating at its normal rated capacity, which boiler is of sufiiciently low head room to accommodate railway clearances so as to be capable of shipment by railway and as a completely assembled unit, as above mentioned. A further advantage of this construction resides in the fact that the angle included by the upper and lower banks of tubes is quite small, and the angles of these banks to the horizontal are quite small. The inclination of the tubes of the upper and lower banks is sufficient to eliminate the possibility of steam locking and dry tubes, while avoiding upward flow of the steam bubbles through the water in the tubes and obtaining a low hydraulic head relative to the distance of travel of the steam bubbles. This causes a complete emulsion of the steam bubbles with the water, resulting in unusually rapid circulation and assuring that the tubes are kept wet at all times, which contributes materially to the heat absorbing capacity of the boiler.

In the construction of boiler in Figures 1 and 4, the steam and water drum 8 is of appreciably greater diameter than the mud drum 9, and the mud drum and the water drum are of substantially the same diameter. It is the present practice in boiler construction to have the upper water and steam drum of the same diameter as the mud drum. I have found, however, that by increasing the diameter of the steam and water drum I obtain certain important advantages over the present practice. In practice, I prefer to have the water and steam drum approximately one-third greater in diameter than the mud drum 9. This relatively great diameter of the steam and water drum has numerous advantages. It provides greater water and steam storage space than heretofore, and also provides an increased steam liberating area avoiding splashing in the steam and water drum. Another important advantage of employing the steam and water drum or relatively great diameter is that it provides greater water endurance surface than is available in boilers constructed in accordance with the present practice, maintaining the water more nearly at a constant level. This is an important consideration in the operation of boilers.

In the several forms of my invention illustrated the setting or casing, including the furnace, has been illustrated as of more or less conventional construction. It will be understood, however, that the construction of the setting or casing may be varied within wide limits without departing from my invention which resides primarily in the construction and arrangement of the boiler drums and tubes and associated parts. The mud drum 9 is provided with a blowolf pipe It!) for blowing mud and sediment out of this drurn in a known manner.

As will be noted from the drawings, and as clearly illustrated the-rein, in all of the forms of my invention the angle to the horizontal of the lower bank of tubes is quite small, being less than 15 in each instance, and the angle between the upper and lower banks of tubes is quite small also. In Fig. 1 the angle between the upper and lower banks of tubes is but 17, as illustrated. In Fig. 4 this angle is but 15 /2", and in Fig. it is but 20 In each instance, the angle between the upper and lower banks of tubes is appreciably less than 22, and the angle of the lower bank of tubes to the horizontal is less than This particular disposition of and relation between the banks of tubes is advantageous as contributing to low head room and rapid circulation of the water, while permitting the use of unusually short tubes in the bank connecting the mud drum and the steam and water drum so that the boiler can be shipped with facility in its assembled condition and as a unit. Low head room, rapid circulation of the water, and the ability to ship the boiler as a completely assembled unit, are all important considerations in this art as contributing to the efliciency of the boiler in operation and the shipping thereof.

As is clearly illustrated in Figure 1, the rear bank of tubes is relatively short and the distance between the steam and water drum and the mud drum is not substantially greater than the diameter of the steam and water drum. This is advantageous as assuring rigidity of the tubes of the rear bank, as above pointed out, and by having these tubes relatively short and of ample diameter free flow of water downward through these tubes is assured, which promotes rapid circulation. By constructing the boiler in this manner, the space within the outline of the banks of tubes is substantially filled by the tubes and drums, so that a maximum area of heat absorbing surfaces is exposed to the hot gases from the furnace, which greatly increases the efificiency of the boiler. The boiler as a whole approximates cubiform and approaches a block formation substantially filled by the banks of tubes and the drums. This structure is particularly suitable for mounting in a cubiform casing, the boiler being disposed so as to fill substantially the casing above the throat of the furnace. With the boiler disposed in this manner the throat of the furnace extends substantially the full length of the lower bank of tubes, which is the main heat absorbing means of the boiler. This, in conjunction with the disposition of the drums and the banks of tubes so as to fill substantially the space within the outline of the tube banks, assures maximum heat absorbing eficiency, and results in a compact high duty boiler of exceptionally low head room, which steams freely and has rapid circulation.

In the form of boiler illustrated in Figure 4, I provide a greater number of tubes in the upper bank than in the lower bank. This is advantageous as facilitating expansion of the steam generated in the tubes thus promoting rapid circulation, particularly in a three drum ring circuit boiler.

As above indicated and as will be understood by those skilled in the art, changes in construction and arrangement of parts of my invention may be resorted to without departing from the field and scope of the same, and I intend to include all such variations, as fall within the scope of the appended claims, in this application in which the preferred forms only of my invention are disclosed.

What I claim is:-

1. In combination, in a boiler, a steam and water drum, a water drum, a lower mud drum, banks of tubes connecting the drums in a ring circuit, a bafile supported by the bank of tubes connecting the mud drum to the water drum and extending from the former toward the latter, a second baflle extending across the bank of tubes connecting the water drum to the water and steam drum, and a third bafile between the first and second bafiles and movable to accommodate expansion and contraction of the tubes of the bank connecting the mud drum to the water drum.

2. In a boiler, a plurality of drums, banks of tubes connecting the drums, two of said banks of tubes being disposed in juxtaposition, baflling for directing flow of gases about and between the tubes, said bafiling comprising a baille member extending between said two banks of tubes and supported by but unsecured to the tubes of one of the two banks, a cross-bar, supporting means therefor, and a loose sliding connection between said bar and the baffle permitting free movement of said bafile to accommodate expansion and contraction of the tubes supporting the bafile member, the bar holding the baflle member against movement out of operative position.

3. In a boiler, an upper drum, 2. lower drum, a front drum between the upper drum and the lower drum, an upper bank of tubes connecting the upper drum and the front drum, a lower bank of tubes connecting the lower drum and the front drum, a bank of tubes connecting the upper drum and the lower drum, and a baflle extending between the upper and the lower banks of tubes and closing the space therebetween, said baffle being supported solely by the tubes of said upper and lower banks.

4. In a boiler, a plurality of drums, banks of tubes connecting the drums, two of said banks of tubes being disposed in juxtaposition, bafiiing for directing flow of gases about and between the tubes, said baflling comprising a baffle member extending between said two banks of tubes and supported by but unsecured to the tubes of one of the two banks, a cross-bar supported by the tubes of the other one of said two banks, and a loose sliding connection between said bar and the baffle member permitting free movement of said baflle member to accommodate expansion and contraction of the tubes supporting the bafile member, the bar holding the baffle member against movement out of operative position.

5. In combination in a boiler, an upper drum, a lower drum, a front drum between the upper drum and the lower drum, an upper bank of tubes connecting the upper drum and the front drum, a lower bank of tubes connecting the lower drum and the front drum, a bank of tubes connecting the upper drum and the lower drum and materially shorter than the tubes of the other two banks, a baflle structure extending upwardly and forwardly from the lower drum and supported by the lower bank of tubes, said structure including a baflle member closing the space between the upper and the lower banks of tubes, and supported by but unsecured to the tubes of the lower bank, and means providing a loose sliding connection between the baflle member and the tubes of the upper bank and cooperating with the free support of the baflle member by the tubes of the lower bank to permit expansion and contraction of said bafile member independently of the tubes of said upper and lower banks.

6. In a boiler, an upper drum, a lower mud drum, a front drum above the mud drum, an upper bank of tubes connecting the upper drum and the front drum, a lower bank of tubes connecting the lower drum and the front drum, a bank of tubes connecting the upper drum and the lower drum, bafiling for directing flow of gases about and between the tubes, said baflling extending upwardly from the lower drum and across the space between the banks of tubes, and a cross-bar supported by the tubes of one bank, the bafiling comprising a member having an edge portion thereof in contact with but unsecured to said bar, said member being in part held in position by the bar while being capable of expansion and contraction independently of the bar.

ASHUR U. WETHERBEE.

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