US1725920A - Series boiler and method of operating the same - Google Patents

Description

Aug. 27, 1929.

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SERIES BOILER AND METHOD OF OPERATING THE SALE Original Filed April 16. 1918 7 Sheets-sheet 7 INVENTOR. a I BY fli/A TTORNEYS.

Patented Aug. 27, 1929.

UNITED STATES PATENT OFFICE.

DAVID S. JACOBUS, OF JERSEY CITY, NEW JERSEY, ASSIGNOR TO THE BABCO CK-8z WILCOX COMPANY, OF BAYONNE, NEW JERSEY, A CORPORATION OF NEW JERSEY.

SERIESBOILEB-AND METHOD OF OPERATING THE SAME.

Original application filed April 16, 1918, Serial No. 228,827. Divided and this application filed June-' 11, 1920. Serial N6. 388,232.

This invention relates to series boilers and methods of operating the same of which the following is a full, clear and exact description, reference being bad to the accompanying drawings, forming part of this specification, and illustrating certain forms of apparatus suitable for carrying out my invention, in which Figure 1 is a diagrammatic sectional side elevation showing one form of my improved boiler provided with a handfired coal furnace, and showing, also, feedwater apparatus and superheat-limiting apparatus; Fig. 1 is a horizontal section taken through the tank 12 just above the float 21; Fig. 1 is a section taken along the plane of the line 1"1 of Fig. 1, Fig. 2 is a detail of the regulating valve controlling steam for driving the feed pump in Fig. 1; Fig. 3 is a view similar to Fig. 1, showing my improved boiler provided with an underfeed stoker, this view also showing a superheat-limiting device and a'device for regulating the temperature of the superheated steam; Fig. 4 is a view similar to Fig. 1, showing my improved boiler arranged with the interchanging device in connection with the feed-water system; Figs. 5 and Gare views similar to Fig. 1, showing a modified form of the boiler with its units arranged in a different relation; Fig. 7 is a sectional side elevation of my improved boiler showing oil-firing and arranged for practical use as regards the preferred general proportions of headers and tubes, although the view is partially diagrammatic; Fig; 8 1s a partial end elevation of a portion of Fig. 7, showing the supporting of the header, boxes, and Fig. 9 is a sectional side elevation, partly diagrammatic, with the boiler tubesplaced at an angle of about 15 to the horizontal and provided with the preferred form .of baffling for this type.

My invention relates to series boilers and is designed to provide an improved boiler of this type, on which I have conducted experiments for a considerable period of time. In the preferred form of my boiler, a series of boiler header boxes is used. with tubes, preferably of U-form, extending upwardly therefrom. Part of the tubes are economizer tubes, part of the tubes are boiler tubes, and part of the tubes are superheater tubes, for

superheating the steam. after it has been separated from the -water with which it flows through the boiler tubes.

Y My present application, which is a divi-f prior application Serial No.

sion of my 228,2 327 which was filed in the Patent Office April 16, 1918, relates more particularly to the superheater and associated parts, combined with a separating tank interposed between the-boiler tubes and the superheater tubes for the purpose of separating water from the steam and introducing the steam to i the superheater in a dry condition.

In the forms of Figs. 1 to 6. inclusive, the header boxes'are shown much larger and the U-tubes much shorter than I prefer to employ in practice, for clearness of illustration of the principles involved.-

In Fig. 1, 2 represents the header boxes and 3 the series of U-shaped tubes extending upwardly therefrom, the boxes being preferably transverse to the flow of the gases and protected therefrom by the refractory bottom 4: of the furnace chamber. In this type of boiler there is no definite line of division between the economizer portion'of the boiler and theboiler itself. Variations in the rate of feed of the boiler, the temper ature of the feed water, the temperature ofthe furnace gases and the capacity at which the boiler is run, may cause a portion of the heating surface, which is at one time economizer surface, to become boiler surface. (that is, evaporating surface), or vice versa. The superheater surface, it used, is, however, distinct and separate, although the superheater may be called upon to evaporate a certain amount of moisture carried into it by the steam. In this action, how ever, it does not difier from ordinary superheaters used with boilers, as the carrying of a small amount of. moisture into the superheater by the steam is an ordinary occurrence. In this form of Fig. 1, the economizer portion A is made up of the tubes most remote from the source of heat,which is indicated as a furnace 5 having a hand-fired grate 6. B indicates the boiler tubes (that is, the evaporating surface), and C represents the superheater' tubes, which, in this form. are nearest the source of heat; 7 being the oiftake flue for the gases. The

. boxes and tubes to the header 9, which is the foremost header of the boiler tubes proper. From this header 9 the steam, with a regulated amount of water, passes down through a pipe 11 into a tank 12, the pipe 11 having a hand-controlled valve 13. The pipe 11 also has a cross-over pipe provided with a hand-controlled valve 14 and leading to a pipe 15 which conducts the steam from the tank to the rear header 16 of the superheater. The pipe 15 also has a hand-controlled valve 17. From the superheater header 16 the steam flows through the U-tubes into the exit header 18, from which it flows through the outlet pipe 19.

The water fed to the economizer and boiler is controlled in the following manner:

The feed pipe 8 is provided with a loop adjacent to the tank 12, this loop having a valve, shown at 20, controlled by a float 21 lying on the body of water in this tank. The shaft of the float-lever extends through a stuffing-box in the side of the tank and is connected to the valve-stem of the valve or cook 20. Should the water level fall in the tank 12, more feed water is admitted through the pipe 8 into and through the series boiler, which will restore the water level in the tank. Should the water level rise in the tank, the supply of feed water will be reduced and the level will correspondingly fall ,in the tank 12. The feed water is forced into the boiler by a pump 22, to which water is supplied from the tank 23 through the pipe 24, water being supplied to the tank 23 through the valved pipe 25*. The steam for the feed pump enters through pipe 25, having a diaphragm-controlled valve 26, shown in detail in Fig. 2. This valve is controlled by the pressure in the water feed pipe 8, which has a branch 27 provided with a pressure gauge 28 and leading to one side of the flexible diaphragm 29. The pressure on this diaphragm is resisted by a spring 30 hearing against the plate 31, which acts on the center of the diaphragm. The spring 30 surrounds the stem of the control-valve 26 for the steaminlet pipe 25. By making the spring of proper strength, the valve may be arranged to close at the pressure desired on the exit side of the feed pump, which pressure is transmitted to the side of the diaphragm opposite the spring. The diaphragm-con trolled valve will, therefore, remain fully open until the pressure in the pipe 27 reaches a predetermined point, when the spring will be compressed and the valve will begin to close, thus reducing the speed of the feed pump, after which the valve will be adjusted to a position which will keep the pressure on the exit side of the pump within the desired range.

Instead of the diaphragm-controlled valve shown in Fig. 2, any well known device for controlling the speed of a feed pump may be employed to maintain a reasonable uniform pressure of discharge on the water from the pump.

The final header 9 of the economizer and boiler. sections is preferably provided with a safety-valve, shown in Fig. 1 at 33, and the outlet pipe 19 from the super-heater 18 is preferably provided witha branch 34 having a safety-valve 35 and a,.stop-valve 36. The stop-valve is used in starting up the boiler and to maintain a circulation through the boiler in case of a sudden shut-down.

I have also shown, in Fig. 1, a superheatlimiting apparatus. In this form, the steam from the pipe 19 flows through a pressureregulating valve 37 and a stop-valve 38, which is wide open under normal conditions, and thence down through the chamber 39 over the coil 40 of a superheat-limiting device, and thence to supply pipe 41, which passes to any desired apparatus.

The pressure generator in the coil 40 acts upon the superheat-limiting device, generally indicated at D, and which is fully described in my Patent, N 0. 1,328,997, which was issued January 27, 1920.

In Fig. 1 this device acts by admitting cold air to the interior of the boiler setting in case the superheat exceeds a certain predetermined figure. This air is admitted through the doors 42, which, in the figure, are indicated as open, the arrows showing the in-fiow of air therethrough.

The superheat-limiting device acts only in case of excessive superheat, the amount of superheat being normally such that the doors 42 are closed and no air is admitted through these door openings into the setting. The surface of the superheater C is so formed that the superheat will be normally below a figure which will give trouble. In case of a sudden shut-down, or any other irregularity in operation which would lead to ex cessive superheat, the superheat-limiting device D is brought into action in the same way as the safety-valve on a steam boiler is called into action when the steam pressure exceeds that for which the safety-valve is set. The superheatdimiting device herein shown is a safety device for preventing excess superheat and is not a .device for regulating the amount of superheat.

In starting up such a series boiler from a cold condition, all parts of the boiler, including the superheater, are filled with water under pressure. The air. within the boiler need not be removed. but by feeding in water at a high pressure, the volume of air pocketed in the boiler is comparatively small. Some water is preferably allowed to flow through the boiler before starting to remove a portion of the air which would otherwise be pocketed. this water being allowed to escape through the stop-valve 36.

At this time. when the apparatus is flooded with water preparatory to starting, the valves 13 and 17 are closed-and the valve 14 is open. After steam is formed, steam and water are allowed to escape through the valve 36. hen the flow of steam and water through the valve 36 becomes reasonably uniform, the valves 13 and 17 are slowly opened and the valve 14 closed. The water fed during the period of starting up is regulated by means of the'feed-valve 128. In starting up, the water is maintained at such a level in the tank 12 that the valve 20, which is controlled by the float 21, remains open, the waterlevel being indicated by a water glass, indicated at. 43. After starting up, the feed pump is governed to maintain a given height of water in the tank 12. which will cause the amount of water flowing into the tank through the pipe 11 to be governed by the amount of water which is allowed to flow from the bottom of the tank through a pipe, fitted with the throttle-valve 45, and into the feed tank 23. By adjusting the throttle-valve 45 the water may be blown from the tank 12 at any desired rate, and with the water in the tank 12 maintained at a constant level, the water in the steam which enters the tank 12 will enter the tank at the same rate as the water is blown away from the tank 12. The tank 12 is fitted with a blow-off connection 44 to remove any sediment accumulating in the tank and to drain the tank 12.

In operating the boiler, the pressure is kept within the desired range in the feed pipe, the pressure being indicated by the pressure gauge 28. The frictional resistance ofthe water and steam flowing through the series boiler is a material factor, and the pressure of the feed water entering through the pipe 8 must be sufliciently high to overcome the frictional resistance of the flow. This frictional resistance varies greatly, increasing with the load, and where a constant pressure is maintained in the steam discharged from the boiler, the pressure of the feed water entering through the pipe 8 must be correspondingly varied where it enters the boiler by, adjusting the feed valve 128. The steam and water from the box 9 enters the tank 12, where thetwo separate, and the steam passes up through the valve 17 to the header box 16 of the superheater, and thence through the superheat-limiting system to the point of offtake.

In Fig. 3 I show a form similar to that of Fig. 1, the similar parts being marked with the same numerals with the latter "a applied, the underfeed stoker 46 being employed.

In this figure I also show the coil 40-- of the superheat-limiting device as placed in the outlet pipe 39 of the superheater.

In this figure I also show an additional feature, consisting of the h'lllPQfllCillQLl-Stfiillll attemperating device marked 47. which acts to regulate the temperature of the superheated steam discharged from the superheater. This attemperating device is similar to one shown in my Patent Xo. 1.149.265,

.dated August 10, 1915, for method of and apparatus for regulating the temperature of superheated steam.

The attemperator admits a regulated amount of water into the superheater through the distributing pipe 48 and smaller pipe connection 49. which enter the superheaterheader box 16 at various points .in its length. The water admitted to the super heater is obtained from the tank 12 through the pipe 50, the pressure in the tank 12 being maintained somewhat higher than that in the superheater by throttling the steam leaving the tank by means of the valve 17*. The difference in pressure between the tank 12 and the superheater is indicated by the readings of thepressure gauges 51 and 52. The attemperator 47 regulates the amount of water supplied through the 'pipe 50 by opening and closing a stop-cock 53, being governed through the temperature of the superheated steam surrounding the coil 40. The superl'ieat-limiting device D is not brought into action except when, through some unusual circumstance, the superheat becomes higher than it should be. in which case cold air is admitted to the setting as before and the damper 54 is closed, this damper admitting forced blast to the stoker.

In this form, a float-valve 55, of any well known form, is attached to the outlet of the pipe 25 to regulate the amount of watersupplied to the feedtank. I also show threesets of superheater tubes, the intake ends or the tubes being extended down near the bottoms of the headers, shown at 56, to reduce the amount of water that would tend to pocket in the superheater headers.

In this figure I show a. diaphragm con trolled valve 26 for the steam pipe leading to the feed pump. The function of the diaphragm controlled valve 26 is the same as that of the valve 26 in Fig. 1. A pipe provided with a relief-valve 129 that may be i opened by excess pressure is placed on the discharge side of the feed pump, and in case of the closure of the float-operated valve 20",

resulting in an over-pressure, it bypasses some of the water back to the feed tank 23. The speed of the pump may be regulated by hand in starting up the boiler by adjusting the throttle and stop-valve G in the steam pipe leading to the pump.

' to be used as a closed tank. In this case, the

through the coil 57 within the tank 23.

water passing from the tank 12 through the valved pipe instead of passing directly to the feed tank 23 so as to mingle with the feed water therein, is passed B this coil, the heat contained in the watei which passes from. the tank 12 is returned to the feed water in the feed tank 23*. The water from the tank 12 is finally allowed to escape through the pipe 58and throttlevalve 59. The feed water enters the tank 23 through the valved connections 60, finally passing from the tank 23" through the pipe 24 to the feed pump 22". The upper part of the coil 57 is the hottest, and the hottest water in the tank 23 is in its upper part. The heat is, therefore, imparted from the coil 57 to the water in the tank 23 by the counterflow principle, which leads to a maximum of heat transfer.

This tank 23" may be either 0 en to the atmosphere by opening the relie -valve 61 or the space above the water in this tank may be maintained below the atmospheric pressure by applying suction through the pipe 62, which leads to a suction-producing device. Air and gases may thus be eliminated from the feed water, which is of advantage In minimizing corros on 1n the interior of p the economizer element of the boiler, andsis of further advantage in certain cases where the steam from the boiler is used in connection with condensing apparatus.

In this form. of Fig. 4 the water for regulating the temperature of the superheated steam, which is admitted through the throttling cock 53 is the same as the feed water which enters the economizer through the pipe 8 and is, therefore, of the same degree of purity; whereas, in the form of Fig. 3 the water for attemperating the steam was taken directly from the tank 12", and if there are impurities in the water, the water in this tank 12 will not be as pure as the feedwater. Where a certain amount of impurities is present in the water, it is, therefore, of advantage to use the arrangement shown in Fig. 4. v

In Fig. 5 I show diagrammatically an arranger'nent of my series boiler wherein the hottest ases first contact with a portion of the boiler heating-surface before they pass through the superheater. The economizer portion of the boiler is marked A and the boiler portion B"; this being divided into two parts, one part in front of the economizer part and the other adjacent to the then through the tube 63 through the other front boiler part, finally entering the header 9, and passing thence through the pipe 11 to a separator tank, not shown in this fig ure. C indicates the superheater part in which there is less danger of burning the superheater tubes than in the previous forms, where the hottest gases flowed over the superheater tubes.- The counterflow principle is still retained in the boiler portion and the same principle applies in the flow of the steam through the superheater, the flow in both cases being counter to the direction of the flow of the hot gases.

In Fig. 6 I show a form generally similar to that of Fig. 5, in that the boiler portion of the tubes B is divided into two parts; one part acted upon by the hottest gases and the other by the gases after they have passed the superheater portion C.

In this figure the separator tank12 is shown as a horizontal cylinder or drum, and the amount of feed water admitted to the boiler through the pipe 8 is regulated by a feed-regulating device 64 of well known construction, so as to maintain an approximately constant level of water in the tank 12. The water from the tank 12 ,-in this form, passes through the valved pipe 45 to the feed tank 23, a coil 65 being used to transmit the heat from the water passing from the tank 12 into the feed tank 23 and prevent loss of heat through the vapor escaping from the point where the hot water from the valved pipe 45 mixes with the water in the tank.

Figs. 5 and 6 are incomplete in certain essential features, to bring out more clearly the special features illustrated therein.

In Fig. 7 I show a series boiler arranged to be heated by an oil-furnace, and of a general form which experiments have indicated as preferable as regards the general proportions of the tubes and headers. The parts are marked with numerals in accordance with the-previous figures with the letter e applied, the boiler portion being divided into two sections B with the superheater C between them, so thatthe hot gases from the furnace contact with the portion of the boiler or evaporating tubes, thence over the superheater tubes, thence over further boiler tubes, and thence over the economizer tubes A", before reaching the uptake 7. The oil-burner 66 may be spaced along the front of the furnace, a part of which is broken away in the drawing, or any form of stoker or hand-fired gratemay be used.-

In this form, the feed water in the pipe 8 enters the rear header box 2, and thence flows upwardly through the economizer tubes 3 and thence downwardly to the header box 67. From this header box the water then flows upwardly through the tubes 68 into the header 69. The headers 69 are at a slightly higher level than the headers 67, and the tubes 68 are" spaced alternately with reference to the downtake tubes leading into the header box 67. The succeeding arrangement is similar, the downfiow tubes being spaced alternatelywith the upflow tubes of each box until the header 70 is reached. From this header the steam and water flow through tubes 71' which have wider bends, bridging the superheater tubes and entering the header 72. From the header 72 the steam and water flow progressively through the boiler tubes and finally enter the header 9. From this header the steam and water pass through a series of pipe connections 73 into across pipe 74. The water is separated from the steam in this cross pipe, and the water flows through continuousl a number of small pipe connections 75 through the valved connection 7 6, and to the tank 12 From the separating pipe 74, the steam, from which the greater part of the water has been separated, passes upwardly through the small pipes 77 into the superheater header 78. From this header the steam passes through the superheater tubes into the superheater header 7 4 from which it is taken away. The water is maintained at an approximately constant level in the tank 12 by any of the means thus far described,a certain amount of water being allowed to escape through the throttlevalve or the purpose previously set forth.

The preferred method of supporting the tubes in the headers is illustrated in Fig. 8, which also shows the arrangement of the down-flow and up-flow tubes for the headers. As shown, the support consists of cast-iron pieces 79 held in place by bolts 80, and secured, in turn, by the beams 81. The supporting piece 79 may interfere with the removal of the fittings opposite the ends of the tubes if it is necessary to remove those adjacent to these supports. 'In such. case, the bolts for one of the pieces 79 are 'removed with the piece, after which the fittings can be more readily manipulated. Each header is supported by more than one of the pieces 79, so that one piece may be removed without interfering with the header support. If necessary, the headers can be jacked upwardly in order to replace the supportin pieces 79. s

In t e series boiler of Fig. 9, the tubes 3 are placed at an angle of about 15 to the horizontal, the boiler having a hand-fired grate 6. The evaporating or boiler portion of the tubes is divided into two parts B, of which one part is directly above the furnace, in a position to absorb radiant heat and to be acted upon by the hottest gases leaving the furnace. Over this set there is a horizontally-ex'tending bafitle 117 at the rear end. and which has a vertical bafifle 118, a front baflle 119 being arranged as shown. The hot gases flowing along the lowermost tubes B rise through the front vertical pass, first over the evaporating tubes, then over the superheater tubes C, and thence over the boiler and economizer tubes, and are then drawn down through thesecond pass at the right-hand of the bafile 119, and then rise at the left of this battle to the take-off flue 120.

The baffle 119 has an extension 121 to preimproved series boiler. The feed water enters through the pipe 8 and passes into the upper header 122, and thence flows through the U-tubes and staggered small headers 123 until it reaches the cross box 124. From this box the steam and water pass through the tubes 125, which are bent to a wider radius, and flow into the header box 126. From this box the steam and water pass through the successive pipeslto the lower header box 127, and thence through a number of tubes or pipes to a cross pipe 11, and to the tank 12. From this separator tank the steam passes through the pipe 15 and valve 17 to the superheater C, and is finally discharged from the superheater to the outlet pipe 19. From the tank 12, the pipe connection 45 leads to a throttle-valve, and the connection 44 leads to a blow-01f valve.

The form of boiler shown in Fig. 9 does not completely embody the counte'rflow feature, butdoes embody it to a suflicient extent to give high efliciency. It is especially useful for certain conditions of service Where the boiler should be kept within. a certain specified floorspace.

- The withdrawal of steam and water to a separating tank or vessel, in which the water is separated from the steam, is an important feature. Where a superheater is used, the steam is thus taken in a comparatively dry state to the superheater. The provision of there are impurities in the water, as the steam, free, or practically free, from impurities, flows from the separating tank into the superheater, the impurities collecting in the water.

Bleeding the water from the steam and water drum or separating tank is also an important feature, as it makes it possible to use a feed-water regulator governed by the height of water in the steam and water drum; whereas should no water be bled from the steam and water drum, it would not be possible to use the regulator. The regulation of the amount of feed water to a series boiler has been one of the difiicult features of operation, this usually being accomplished through regulating the feed water to maintain a given amount of superheat. By regulating the feed water by means of the water level in the steam and water drum, the re u lation is greatly simplified and more reliable results can be secured than where an attempt is made to regulate the feed water through changes in the temperature of the superheated steam.

The action secured through bleeding out a certain amount of water from the steam and water drum is as follows:

To maintain a given height of feed water in the drum, the feed must be adjusted so that it will correspond to the steam evaporated plus the water drawn out from the drum. If the rate at which the water is fed is too low, the water level will fall through the water being bled away from the drum, and if too great, the water level will rise through more water being fed into the drum than is bled away from the drum.

Should no water be bled away from the drum, there would be no variation in the water level in the drum except that caused through over-feeding the boiler, which would result in the water level rising in the drum, and after rising in the drum, the water level would not fall even should too little water be fed to the boiler. The draining off of a regulated amount of water from the steam and water drum is, therefore, a most important feature, as it makes possible the control of the feed water through a regulator which acts through variation in the height of the water in the drum. The feed-water regulators used in connection with ordinary steam boilers are, in the main, operated through variation in water level in the boilers,-and by providing a series boiler where the feed water can be operated through the means of a variation in the water level, it is possible to employ standard apparatus for the purpose.

What I claim and desire to secure by Let ters Patent of the United States is:

1. That improvement in the method of operating a series boiler having both boiler and superheater tubes and a tank interposed between the two for separating water from the steam, which consists in bypassing the steam and water around said tank on starting the boiler.

2. That improvement in the method of operating a series boiler having both boiler and superheater tubes and a tank interposed between the two for separating water from the steam, which consists in bypassing the steam and water around said tank on starting the boiler, and passing the steam and water to said tank during normal operation.

3. The method of operating a series boiler having both boiler and superheater tubes and a tank interposed between the two for separating water from the steam, which consists in bypassing the steam and water around said tank on starting the boiler, and then gradually introducing the steam and Water to said tank and simultaneously reducing the amount bypassed, until at normal operation all of the steam and water pass to said tank.

4. In a series boiler comprising both boiler and superheater tubes, means interposed between the two for separating water from the steam, and means for bypassing the steam and water around said means.

5. In a steam boiler, a plurality of boiler tubes through which the steam and water are passed in series, a separating vessel into which the steam and water from said tubes discharge and in which the steam is separated from the water and contained impurities, a superheater to which the steam from said separating tank is led, means for drawing off from said separating tank the water and contained impurities, means for supplying feed water to said boiler tubes, and means for returning the heat in the water withdrawn from said separating tank to the feed water without mixing the feed water and the waterwithdrawn from the separating tank. A

6. In a series boiler comprising both boiler and superheater tubes, a tank interposed between the two and below the lowest point of either one of them for separating the steam and water, and means for regulating the feed to the boiler in accordance with the water level in said tank.

7. The method of operating a series boiler and attached superheater, consisting in escape at a given rate, governing the amount of feed water by means of the height/of water in said vessel, and passing the steam from said vessel through the superheater.

- 9. In a steam boiler, steam generating tubes and superheater tubes, aseparator located between said generating and superheating tubes, means to return water from said separator to said generating tubes and means to cause solids in the steam and water passing into said separator to be removed continuously from the system.

10. In a steam boiler, steam generating tubes and superheater tubes, a separator located between said generating, and superheating tubes, means to return water from said separator to said generating tubes and means to cause solids in the steam and water passing into said separator to be removed continuously from the system together with water that was unvaporized in the steam generating tubes.

11. In a steam boiler, steam generating, tubes and superheater tubes, a separator located between said generating and superheating tubes, and means to cause solids in the steam and water passing into said separator to be removed continuously from the system together with water that was unvaporized in the steam generating tubes, and

'means'to transfer heat'from said removed water and solids to water that is fed-into sa d steam generating tubes.

12. The process of steam generation which comprises heating water to produce steam,

removing steam together with unvaporized water and solids from the zone where the steam was produced, separating the steam from unvaporized water and solids, and imparting suiticieut additional heatto the steam to superheat it, and transferring heat from the separated .water and solids to wawater and solids to water that is to be heated to produce steam.

DAVID S. JACOBUS.

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