US2030265A - Water tube boiler - Google Patents

Description

www@ l Feb M, w36. J. o. NYGAARD WATER TUBE OILER Filed June 11, 1932 v4 sheets-snaai 1 q l? M Feb. M, i936.

J. o, NYGAARD WATER TUBE BOILER Filed June 11, 1952 .www m MW 4 Sheets-Sheet 2 Feb. 11, 1936. J. o. NYGAARD WATER TUBE BOILER 4 Sheets-Sheet 3 Filed June 1l, 1932 gaard,

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Feb M, 1936., J, o. NYGAARD WATER TUBE BOILER 4 Sheds-Sheet 4 Filed June ll, 1932 Patented Feb. 11, 1936 Ni'i'D STATES PATENT OFFICE Application June 11, 1932, Serial No. 616,717 In Norway June 12, 1931 14 Claims.

The present invention relates to an improved water tube boiler. This improvement results in a more compact and advantageous construction than hitherto and is based upon different important and new features forming parts of the total invention.

A principal and basic feature resides in this that a combustion chamber which is arranged in well-known manner as a centrally located core, is surrounded by at least two preferably circular layers of boiler tubes and one or more smoke gas channels, the tubes of at least one tube layer being at one or both ends mounted slidably in their headers, and these headers are supported by an exterior pulling member, preferably the surrounding boiler shell, so that the latter receives as tensile stresses the forces produced by the steam pressure and tending to press apart from one another the headers at both ends of the boiler tubes.

Another important feature resides in the combustion chamber constituting a central heat radiating Wall surrounded by at least two layers of boiler tubes and smoke gas channels receiving the principal proportion of the radiating heat and protecting to the greatest extent the exterior boiler shell against heat. The tubes of the inner layer may be provided with wings welded thereto along the portion of their periphery facing apart from the radiating wall. The said wings should be so located as to receive not only heat from sweeping smoke gases but also the radiating heat passing from said walls outwards between the tubes and thereby to conduct such heat to the eX- terior sides of the tubes.

The slidably mounted vaporizing tubes are provided vvith means to cause said tubes to vaporize the water received in one end from the collecting water header and to superheat in the other tube end the steam produced in the middle tube portion and to conduct such superheated steam to the header at said other tube end.

Each boiler tube layer may project into annular distributing and collecting headers divided into segments supported by the surrounding boller shell, the interior parts and members of the boiler being so shaped in relation to one another that they intersupport each other and are assembled in their relative position by4 the boiler shell surrounding and binding together the whole structure in such a manner that the several interior parts and members, upon the shell having been opened, may be picked out in a definite succession. Y

The most heat is supplied to the wall portion around the llame. When the gases in the smoke gas channel outside the said wall approach this wall portion, they have a temperature far below that of said portion, because they have given oi an essential part of their heat to the boiler tubes (Vaporizer and/or superheater) In order to obtain an eiiicient heat-delivery from the smoke gases also along the said wall portion, it is advantageous to arrange a heat-absorbing member, for instance an intermediate superheater between the wall and the smoke gases, so that the latter enter here in contact with the wall.

Such an intermediate superheater may consist of one or two layers of tubes, one of which may suitably be so-called wing-tubes, in order to form thereby a somewhat tight wall against the heat rays from the inner wall.

Other features of the invention will be eX- plained hereinafter in connection with the drawings.

Fig. l shows a diagrammatical longitudinal section of a boiler constructed in accordance with the invention. Fig. 2 shows a part of a cross section of same on the line II-II of Fig. 1 and shows the diiierent layers of boiler tubes, insulating material, smoke gas channels and combustion channel.

Fig. 3 shows in a larger scale a longitudinal section of the boiler portion adjacent the lowermost collecting and distributing headers and in a somewhat modied form.

Fig. 4 shows similarly a part of a longitudinal section of the boiler portion adjacent the uppermost headers.

Figs. 5 and 5a show in a larger scale longitudinal sections of a boiler tube with inserted steam guiding members.

Fig. 6 shows a cross section through a plurality of the tubes shown in Fig. 5 and adjacent parts.

Figs. and 8 show certain details.

In Figs. 1 and 2 the air inlet is shown at I. 2 is the combustion chamber, 3 the inner smoke gas 45 channel, 4 the exterior smoke gas channel which is divided up into smoke gas tubes arranged inside the boiler tubes.

5 is the gas outlet, 6 the water supply to the preheater, l' the conduit passing the preheated 50 water to the pump, 8 the conduit passing from the pump to the steam vaporization member, 9 outlet for steam, I0 the supply of combustible,

II inlet to the intermediate superheater and I2 outlet from same. I3 is the Wall surrounding the 55 combustion chamber and is supported by the glow-vault I4 above said chamber. I5 is the distributing header, It the tubes and I'I the collecting header for the water preheating member. I8 the distributing header, I9 the tubes and 2&3 the collecting header for the vaporizing and superheating members, 2l and 22 are the insulating layers outside and inside the water preheating members respectively. 23 is the boiler shell which is strongly anchored to the foot 24 and to the top piece 25, the latter 24 and 25 forming supporting members for the headers and serving also to receive the compressing strains from the medium in the longitudinal direction of the tubes and to transfer such strains to the boiler shell. 2S is the distributing header, 21a. the exterior, 2lb the interior tubes and 2B the collecting header of the intermediate superheater.

As indicated in Fig. l one or more of the tubes I@ (without interior tubes 4) are used as inlet 6 for feed Water. Into these tubes I5 the cold feed Water is pumped and passes up to the distributing header I5 and from the latter again downwards through all the normal tubes I6 (with interior smoke tubes 4) to the lower water collecting header I8, then from same through a lateral channel 'I out into an exterior conduit 5I containing an energie pressure pump 50. This pump now forces this feed water well preheated through a lateral inlet 8 into the distributing header I8. Fig. 7 indicates constructional forms of the members 5, 'I and 8.

In the constructional form shown in Fig. 3 the lowermost collecting and distributing headers are supported by ribs 29 of the intermediate superheater header 2G made as a closed ring and transferring the compressive strains from the medium (water or steam) to the shell 23, the header 26 resting in the ring 30 Which is safely anchored to the shell for instance by rivets or by welding. Fig. 3 also shows, how the inlet II to the header 26 and outlet I2 from header 28 may be suitably arranged. The ring SI, preferably divided into two parts, is a loose extension of the collecting header I'I and has principally for its purpose to conduct the smoke gases from gas channel 3 (Figure 1) through a curved path into the smoke gas tubes 4.

32 is a ring provided with feet 33, whereby the walls etc. forming the combustion chamber are supported on the header 2t and thereby on the boiler shell 23. 2!! is the foot piece, upon which the boiler rests. Sli and 49 (Figs. 3 and 4) are some brackets riveted or weided to the boiler shell and retaining the headers I'I, I3, I5, and 2B in position, when the boiler is out of operation. 35 is a shielding wall to prevent the smoke gases from reaching the wall I3 and the comparatively hot tubes 2lb. il! are soft packings (for instance an asbestos cord) to protect against the smoke gases under over-pressure. l2 is a calked tightening ring of copper or the like, 63 a protecting ring of a suitable material and 44 a spring-ring retaining it in position. 45 is a thin metal sleeve which may be attached to the tube end or be made by thinning out same and has engagement with a slide-bearing in the header I3. This sleeve which may also be attached to the slide-support and engage the tube wall represents a very eifrcient measure preventing leakage of water or steam out into a draining channel 46, from which a draining pipe il conducts suitably to the collecting header I or into the conduit l.

As shown in Fig. 4 the upper headers are supported, substantially by means of ribs 36, by the 'the layer located inside saine.

smoke gas outlet made as a closed ring 3l. The ring 3l receives the compressive stresses of the medium and transfers same to the shell, because it is in engagement with the bracket 38 which is fixedly anchored in the shell, for instance by welding. The brackets 3Q and 33 may, at the joining places be so shaped that they compel the two shell halves to be maintained in their semicircuiar shape and they also serve as means, whereby the two halves remain anchored to one another, Fig. 4 also shows, how the outlet 9 for superheated steam from header 20 may be suitably arranged.

'Ihe boiler tube shown in Fig. 5 may be for instance a vaporization and superheating tube I9 with an insertion member 39 which is shown in different shapes. 40a (Fig. 5a) represents means compelling the medium to take a helical path forwards around the insertion member and 49h (Fig. 5) represent means acting as throttling members for the superheated steam.

As it is advantageous that the radiating heat as well as the highest temperature of the smoke gases act only on the innermost layer of boiler tubes I9, these tubes should be provided with s0- f called wings 48 which may be welded to the tubes at their exterior side for instance as shown in Fig. 6. The wings t3 on adjacent tubes I9 may extend approximately together (Fig. 6) to form members receiving the proportion of the radiati ing heat from wall I3 which radiates outwards between tubes I9 and conducting the heat thus received inwards through the welded joints to tubes and this will effect a good equalization of the heat tension which would otherwise rise on account of the heat radiation received by the tubes 9 direct from wall I3.

It is useful to arrange the different layers of boiler tubes I9 and I5 in closed rings surrounding Each of their distributing and collecting headers I'I, I8, I5, 20 are therefore also suitably shaped as a ring which, owing to the assembling of same with the shell 23, may be divided up into two or more segments.

Such a ring-shaped collecting header 2|] may, as shown in Fig. 4, be held in position inside a header I5 outside same, if desired with a small recess therebetween to receive the asbestos cord 4I which prevents heat transmission from an inside hotter to an outside colder collecting header r and may simultaneously form a tightening means which permits the expansion of the inner member. The outermost collecting or distributing headers I5 and I'I are supported in the shell 23,

whereas the innermost one 20 carries the vault "1- I4 of the combustion chamber 2 (see Figs. l and 4), and the vault I4 also forms a stay for the wall or layer 22 around the same.

Taken altogether, the different heat receiving members and other parts of the boiler may be shaped in a natural manner so that they t harmoniously together, so that they may be put or placed into each other, support each other and maintain each other xedly and safely in position within the closed boiler shell '23 enclosing the Whole. The attaching together of the members by screws or bolts is avoided, and the boiler may be made with small dimensions as compared with its capacity.

By means of a construction according to the present invention the paths 2, 3, 4 of the smoke gases may at all places be made with just the cross section area required by the gases with regard to their temperature and to the velocity which may be safely imparted to them, and along bij the whole path the gas enclosing walls may constitute eiicient heating surfaces.

Transverse obstructions and other things giving rise to unintentional eddy formations are naturally avoided and on account of this fact in connection with a somewhat greater drop in pressure which might be imparted to the smoke gases, the latter will attain a considerably increased velocity past the heating surfaces, so that not only their area may be reduced, but in addition the smoke gases will thereby themselves and owing to the narrow passages prevent ashes etc. taken along with them from being deposited on the surfaces and from forming the undesired heat-insulating coatings which usually must be Y removed by special means.

While a liquid medium is contained in the distributing header I8, from which the vaporizing tubes I9 pass out, only a gaseous medium, according to the present invention, is present in the collecting header 29, wherein the tubes pass in. In other words there takes place in the tubes a total vaporization of liquid flowing in same. A further improvement consists in this that the vaporization has been completed when the medium has passed only a portion of the tubes I9, Whereas the remaining portion of the tubes operates as a superheating tube. Consequently in such case the steam will enter the -collecting header 20 in a superheated state, whereby an extra superheater is avoided.

A technical progress also resides in the feature that in the passage of the boiler tubes I9 a bar 39, another tube or the like is placed. This insertion member may suitably fill out the essential part of the said passage and is important in several respects. By means of this member the boiler tubes I9 may be made comparatively large, and still the gas quantity ilowing through same will not be too great in relation to the heating surface, even if no very high velocities of the medium be'chosen, and the insertion member 39, 49a may, similar to the well-known twisted metal ribbons, impart to the medium a helical path forwards, whereby well-known advantages are obtained.

A high increased velocity of the medium preferably several hundred meters per second is of great importance in the construction herein described, particularly if the medium is caused to vaporize completely within the tubes. As the velocity increases in direct proportion to the increase in volume during the steam formation, an initial velocity which is for instance doubled will correspond to a doubling of all velocities in front thereof. Consequently the heat transmission to the medium will increase, and steam bubbles on the heating surfaces are easier swept away. It will suit the purpose to increase the pumping-work and to allow a comparatively great drop in pressure through the tubes. Thereby the medium in a very narrowed passage may be caused to take on such a high velocity, especially in the superheating portion, that this whole portion may really be considered as an elongated throttling device causing a rather eiiicient turbulating and obstructing influence (increasing with the square of the velocity) assisting in transmitting the heat even to the superheated steam to such a degree that it approaches the heat transmission to the medium in the ordinary vaporization tubes. However, preferably the insertion member is made with a shape as shown at 49D suitable to the purpose and causing an irregular eddy formation.

A helical'shape as shown at 40d and with a suitable pitch on this portion will also cause an intensive eddy formation or a turbulating action throughout the medium, whereby the heat transmission will be sufficient.

The comparatively great drop in pressure taking place through the tubes will have the effect that the medium will be distributed practically uniformly in all tubes, even if the distributing and collecting headers are very narrow, and the medium therefore will flow in the tube passages with a comparatively considerable velocity. These narrow and small headers represent great savings and a simplification of the Whole construction.

'I'he insertion member may also be used to regulate the temperature of the tube proper in relation to the other tubes belonging to the same collecting header on account of their own heat extension, whereby detrimental heat stresses may be eliminated. The member 39 may expand freely by heat and may, at a too high temperature in tube I9, cause a decrease in such temperature, and vice versa at .a too low temperature in tube I9.

An embodiment of same is indicated in Fig. 8. As the pressure is higher in the distributing header I8 than in the collecting header 29, the tubes I9 are always pressed in the direction inwardly into header 20. If now the insertion member 39 which is fixedly attached in header 2U expands by heat less than tube I9, its free lower end (Fig. 8) moves upwards relatively to the lower end of tube I9, thereby acting as a controlling member for a narrowed passage porquantity passes to tube I9, whose temperature f will consequently increase.

The insertion member may also serve as a smoke gas tube. An example thereof are the tubes 4 which constitute insertion members within the tubes I6 and which .are therefore swept by smoke gases.

As already mentioned it is advantageous, however, to arrange the last and uttermost passages of the smoke gases in the boiler only in these smoke gas tubes 4, because thereby all the heat given off here will be received by the medium.

The member 39 may, if not removed in the manv ner explained below, be taken out after removal of the tightening plugs in the collecting headers.

Thereby it is easy to clean the comparatively wide boiler tubes.

Further it is very important that the boiler tubes I6, I9 iilled with the heat-receiving medium may slide with one or both ends in their longitudinal direction in the collecting or distributing header I8, 20, whereby any heat stress between the tubes owing to diiferent longitudinal heat extension is totally avoided. The same applies regarding the surrounding parts or the supporting places of the collecting headers. It is particularly advantageous, if the tubes-as in the construction indicated in the drawingsare not mere vaporization tubes, wherein the temperature would be rather uniform for all tubes, but are combined water preheating or steamsuperheating tubes. The tubes may suitably be attached in one header and be slidable in the other one and they should be adapted to be quite withdrawn from the latter. Thereby the insertion member may be easily removed and the tubes be easily cleaned, if necessary. If, as shown in the drawings, for the uttermo-st layer of boiler tubes IG, the insertion member is a smoke gas tube 4, the inner tube (the insertion member 4 itself) and the outer tube I6 may be attached each in its header I5 and I1 respectively, whereas they are slidable in the other header.

The tubes may be provided with tightening means, for instance as mentioned .above with a covered ring #l2 of copper or the like, where they pass out from their slide-support in the header. Owing to the draining channels 46 the pressure is relieved from this tightening means. These channels 6 may pass between the slide-supports all along the collecting header and in places where a preferably lower pressure prevails. The draining channel may be under atmospheric pressure, and in many cases the leaked medium will be steam which is conducted into the feed water.

The sleeves 45 are formed with a quite thin Wall, preferably of yellow metal, thin enough to cause the over-pressure on one side to press it against the wall, if the sleeve is fixed to the tube, or against the tube, if it is fixed to the slide-support. In the most cases only one draining channel is then necessary, at all events for the water preheating tubes. For the vaporization and superheater header one may arrange a channel 41 conducting the leakage water from draining channel 46 (Fig. 3) through the col lecting header I1 for the water preheating tubes, and further through .a channel with a conduit out to the feed water. Of course, these slidable tubes can not sustain the longitudinal compressive stresses exerted by the medium. "Ihese stresses may be counter-acted by other members, however, for instance by the boiler shell 23 proper, because the collecting and distributing headers may each be arranged in or be supported by brackets or supporting rings 3|, 31 which in some way is in engagement with the boiler shell or is anchored thereto. Of course, the tubes I9 must be supported at certain places between the headers I8 and 29 against the occurring stresses caused by the breaking or end thrust forces.

The boiler as shown in the drawings is intended to be used for gaseous or liquid fuel producing a small radiation. The wall around the combustion chamber will then serve as an indirect heating surface, because it receives heat from the gases by their sweeping over it and it transmits it further by radiation to the boiler tubes arranged around same. Such indirect heating surfaces might advantageously also be arranged in the interior of the combustion chamber, but in connection with coal powder stoking they will hardly be of ,any advantage seen apart from the fact that they would have a favorable influence upon the combustion of the coal powder.

If the boiler is to be built for instance for coal powder, the combustion chamber should have considerably greater dimensions, and within the wall should then also be mounted boiler tubes. The smoke gases may then also during their return passage move along the exterior side of the wall sweeping' the exterior side of the boiler tubes arranged around them, and may then pass through smoke gas tubes arranged as insertion members in the interior of the boiler tubes.

When assembling, the beginning is made for instance with the one shell half. Then in proper order one half of the different members and parts is inserted, one inside the other one the insulating layer 2I, the water preheating members I5, I6, I1, insulating layer 22, vaporization and superheating members I8, I9, 20, ring 3I and intermediate superheater 2B, 21a, 21h, 28, after having pushed in the wall I3 around the combustion chamber and the supporting ring 32, 33 into its cavity. Then the vault and. the smoke gas outlet, the closed ring 31 are put in position, whereupon follows the other half of the members mentioned above but in the inverse succession.

When both boiler shells are anchored together, the interior members and parts are now also coupled together in their safe positions inside the boiler in a manner suitable with regard to heat extensions.

These different details represent separately, as also mentioned regarding some of them, more or less important technical progresses in the steam boiler branch and assist in and form important links of the construction hereinafter described.

'Ihe invention comprises boilers for producing vapors from water and also from other fluids.

I claim:

l. A water tube boiler comprising a central combustion chamber formed inside a combustion chamber wall, a plurality of layers of boiler tubes surrounding the said wall and spaced therefrom to provide between the wall and the innermost tube layer a smoke gas passage connected with the outlet portion of the combustion chamber, collecting headers for the boiler tubes, the tubes of at least one tube layer being at an end mounted slidably in their headers, supports for the headers so arranged at either end of the tubes as to prevent the headers from being pressed apart from one another longitudinally of the tubes, and an exterior pulling member supporting in turn the said supports so as to receive as tensile stresses the forces tending to press apart from one another the headers at both ends of the boiler tubes.

2. A water tube boiler comprising a central combustion chamber formed inside a combustion chamber wall, a plurality of layers of boiler tubes surrounding the said wall and spaced therefrom to provide between the wall and the innermost tube layer a smoke gas passage connected with the outlet portion of the combustion chamber, collecting headers for the boiler tubes, the tubes of at least one tube layer being at an end mounted slidably in their headers, supports for the headers so arranged at either end of the tubes, as to prevent the headers from being pressed apart from one another longitudinally of the tubes, and an exterior boiler shell supporting in turn the said supports so as to receive as tensile stresses the forces tending to press apart from one another the headers at both ends of the boiler tubes.

3. A water tube boiler comprising a central combustion chamber formed inside a combustion chamber wall, a plurality of layers of boiler tubes connected in series and surrounding each other and the said wall and conducting water and steam in the longitudinal direction of the boiler, said tubes being spaced from the wall to provide between it and the tube layers smoke gas passages connected with the outlet portion of the combustion chamber to cause said gases to sweep the boiler tubes, means to draw off the smoke gases after their having passed through said passages, collecting headers for the boiler tubes, the tubes of at least one tube layer being at an end mounted slidablyin their headers,`supports for the headers so arranged at either end of the tubes as to prevent the headers from being pressed apart from one another longitudinally of the tubes, and an exterior boiler shell supporting in turn the said supports so as to receive as tensile stresses the forces tending to press apart from one another the headers at both ends of the boiler tubes.

4. A water tube boiler according to claim 2, wherein the tubes of the innermost layer are provided with wings welded thereto at the exterior tube side facing apart from the combustion chamber wall and so located as to receive not only heat from sweeping smoke gases but also the radiating heat passing from said wall outwards between the tubes and thereby to conduct such heat to the exterior sides of the tubes.

5. A water tube boiler according to claim 2, wherein the headers are made annular and composed of segments.

6. A water tube boiler according to claim 2, wherein heat-insulating material is arranged between the two uttermost boiler tube layers, in order to protect the surrounding boiler shell against heat.

'7. A water tube boiler according to claim l, providing in the interior of the slidably mounted vaporizing boiler tubes members filling out an essential part of the tube passage area and obstructing thereby the flow of water and steam through the tubes so as to cause said tubes to Vaporize the water received in one end from the collecting water header and to superheat in the other tube end the steam produced in the middle tube portion and to conduct such superheated steam to the header at said other tube end, said members being combined with means acting to regulate by the heat expansion of the members the quantity of water and steam passing through the tubes.

8. A water tube boiler according to claim 1, wherein the boiler tubes are so slidably mounted in their headers that they may be pulled quite out from same longitudinally.

9. A water tube boiler according to claim 1, wherein the tube slide-supports .of the headers are provided with at least one draining channel for leakage steam or leakage water, said channels being under a lower pressure than that prevailing at the corresponding place in the interior of the tubes.

10. A Water tube boiler according to claim 1, wherein the tube slide-supports of the headers are provided with a tightening member in the form of a sleeve formed with thin walls within the support.

11. A water tube boiler according to claim 1, wherein the tube slide-supports of the headers are provided with a tightening member in the form of a sleeve formed with thin walls within the support as an integral portion of the tube end.

12. A water tube boiler according to claim 2, wherein the headers are made in annular shape composed of segments contacting each other when assembled and held together in position by the surrounding boiler shell Without bolts or other connecting structure.

13. A water tube boiler according to claim 3, wherein between the heat radiating combustion wall and the boiler tube layer outside same means are provided to receive a principal proportion of the heat transported from the combustion chamber through said wall so as to protect to the greatest possible extent the exterior boiler shell against heat.

14. A water tube boiler according to claim 3, wherein between the heat radiating combustion wall and the boiler tube layer loutside same an intermediate steam superheater is provided to receive a principal proportion of the heat transported from the combustion chamber through said wall so as to protect to the greatest possible extent the exterior boiler shell against heat.

JOHAN OLSEN NYGAARD.

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