US2207654A - Steam generator - Google Patents

Description

J. H. BROWN STEAM GENERATOR July 9, 1940.

Filed June 12, 1959 3 Sheets-Sheet 1 Join 15mm];

J. H. BROWN STEAM GENERATOR July 9, 1940.

Filed June 12, 1939 '5 Sheets-Sheet 2 Heme/7f July ,9, 1940. J. H. BROWN 2,207,654

STEAM -GENERATOR Filed June 12, 1959 3 Sheets-Sheet 3 Patented July 9, 1940 PATENT OFFICE STEAM GENERATOR John H; Brown, Galena, M0.

Application June 12,

6 Claims.

This invention relates to steam generators of the same general class as that disclosed in my prior Patent No. l,l2l,902;gr-anted July 4, 1922, and upon which the present invention represents an improvement. i

More particularly :the invention relates is steam generators. of the verticalboilertype in which the water is heated. in an external coil communicating with the boiler to cause a circulation of water through the coil. In this type of steam generator it has been proposed to place a check valve at one end of the coil so as to render the circulation intermittent instead of uniform. Thus, when steam is generated in the coil the pressure holds the check valve tightly seated and the steam in seeking its escape from the open end of the coil pushes ahead of it a portion of the hot water filling the coil. Upon the escape of the steam and hot water from the coil a vacuum is momentarily created which causes the check valve to open admitting a fresh supply of water to the coil to replace the steam and waterlost therefrom. This vaporization, discharge and replenishment of the water in the coil takes place very rapidly so as to cause a surging or pulsating flow of water through the coil. This surging of the water through the coil together with the almost explosive violencewithwhich steam is created therein serves to dislodge and carry off sediment which ordinarily would deposit within the coil, as Well as to sweep away the minute bubbles of water that tend to form on the innersurface of the coil and retard the transfer of heat through its wall. I

An important object of my invention is to provide in a steam generator of the above character a substantially closed system of circulation for returning through a short path the hot water discharged from the outlet end of the coil to the inlet end of the coil without the loss of any appreciable amount of its heat to the main body of water contained in the boiler. This permits therapid generation of steam commencing almost immediately after the apparatus is placed in service following from the fact thatonly a com paratively small volume of water (a little more than the capacity of the'coil) is directly exposed to the intense heat of the coal: or burnerflame, the heat being conserved within this small vol-- ume of liquid during its repeated passage through the coil until it has been entirely vaporized.

Another object of my invention is to provide means for admitting freshwater from the boiler into the closed system of circulation just mentioned for the purpose of automatically replen- 1939, Serial No. 278,767

ishing the supplyof Water converted into steam. In accordance with the preferred form of my invention, the hot water ejected from the outlet end of the coil is received in an overfiow chamber contained in the boiler and communicating with the intake end of the coil. A control valve responsive to the hydrostatic pressure within the chamber opens to allow water from the boiler to enter the chamber when the level of the water in the latter falls below a predetermined limit.v Preferably, also, this valve is thermostatically controlled to prevent the admission of water to the overflow chamber until the temperature of the water in such chamber has reached a predetermined value. In such case, the operation of the control valve is dependent upon both the pressure and temperature of the water in the overflow chamber. I

Another object of the invention is to provide in a steam generator of the above character a superheater arranged above the boiler and in the path of the waste combustion gases from the coil heatingmeans, the arrangement being such that a part of the'heat which otherwise would be lost up the stack is utilized to dry or superheat the steam delivered from the boiler.

A further object of my invention is to provide in a steam generator of the above character means for returning directly to the heating coil the hotcondensate from the system with which the steam generator is operatively connected--as for example a house heating system-so that the residual heat of such condensate is recovered without any substantial loss thereof to the main body of water within the boiler.

Still another object of the invention is to provide a steam generator of the above character which may be readily dismantled for shipment, repair or cleaning, and which is so simple in construction and operation as to admit of its installation, supervision and upkeep by relatively inexperienced persons.

Other objects and advantages will be apparen from the following detailed description of a'pregenerally cylindrical shape, the lower section r3 being cast in one piece and consisting of an outer shell 3a, an inner shell 3b arranged in spaced relation to the outer shell so as to afford an annular water space therebetween, and webs I 30 and 3d closing the top and bottom, respectively, of this boiler section. This lower boiler sec-.

tion which houses the heating unit is preferably made of some heat-resistant metal or may be fabricated from steel.

The upper section 2 comprises inner and outer shells 2a and 2?), respectively, arranged in spaced relation and defining an annular water space therebetween. The outer shell is closed at its upper end by a steam dome 20 while its lower end is provided with an inwardly directed flange 2d which rests upon the upper end of the outer shell 3a of the lower boiler section. The flange 2d is provided with cutaway areas 2h (see Fig. 6) for a purpose later to be explained.

The inner shell of the upper section is of sub"- stantially less height than the outer shell 2a and is closed at its upper end by a cover plate 2e which is centrally formed with a neck 2f of restricted diameter extending centrally upward through the dome 2c. The lower end of the inner shell is formed with an outwardly directed flange 29 which bears upon the upper end of the inner shell 3b of the lower boiler section 3 and. also underlies the inwardly directed flange 2d of its companion outer shell 2a. Bolts 4 extending through aligned openings in the overlapped flanges 2d and 2g tightly secure the outer and inner shells together.

The upper boiler section 2 thus rests upon the lower boiler section 3. Since the overlapped flanges 2d and 29 at the bottom of the upper section and the web 30 of the top of the lower section close oiT communication between the boiler sections, free passage of the boiler water between these sections is aflorded by a series of connector tubes 5 arranged upon the circumference of the boiler so as to bridge the abutting ends of the boiler sections. Opposite ends of each connector tube, as best indicated in Fig. '7, open through ports in the outer shells of the two boiler sections and are tightly secured by bolts 6 to the outer shells so as to avoid leakage and also to retain the boiler sections in rigid assembly, The web 30 closing the upper end of the lower boiler section is disposed a short distance below the top of this section and the recess thus defined is filled with fibrous packing material I.

Interiorly located within the lower boiler sec tion are heating means, illustrated in the present embodiment as a grate 8 upon which a coal fire may be maintained. In the larger installations of my steam generator a coal fire will usually be preferred, and such a fire may be suitably fed by a stoker or other automatic fuel supply mechanism, not shown. However any other suitable type of heating unitmay be employed, such as an oil or gas burner. A doorway 9 leading through the lower boiler section affords access to the fire on the grate, and similarly a doorway ll'l the grate.

Arranged within the upper boiler section and different elevations, with the interior of the upper boiler section.

- The lower or inlet end of each coil is extended by an exteriorly-threaded bushing l5 which is screwed part way into the end of the coil. En closed within this bushing is a slotted cage 16 i is provided for the removal of ashes from below containing aball ll, the cage and ball together The cage is inclined in v of pressure within the coil outside water forces the ball'away from its seat and passes intothe coil through the valve opening and through slots I8 in the cage.

Located at spaced intervals within the upper boiler section 2 are three upright overflow chambers [9 each operatively associated with one of the heating coils l2, l3 or M. Each chamber comprises a longitudinally closed receptacle the open upper end of which is disposed above the normal level of the water in the boiler and its closed lower end terminating a short distance belowthe inlet end of a coil. The bushing I5 is threaded through the wall of the overflow chamber so as to provide communication therewith. A conical nut 20 threaded upon the bushing is adapted to make a wedge fit with a companion boss 2| on the inner shell 2b so as to insure against leakage around the bushing where the latter passesthrough the shell.

The upper end of the coil is likewise extended by means of an exteriorly-threaded bushing 22 screwed part way into the open end of the coil. This bushing extends through a boss 23 in the cover plate 2e closing the top of the inner shell and its outer end is curved downwardly so as to deliver into the open slightly flared upper end of the overflow chamber 89. A conical nut 24 threaded upon the bushing is adapted to be turned "down tightly within a complementary tapered recess in the boss 23 to avoid leakage past the joint.

The lower end ofthe overflow chamber is provided with a thermostatic control valve which regulates the passage of water from the boiler into the overflow chamber. This valve comprises contraction. When the water within the overflow chamber reaches a predetermined temperature, the cage expands and releases the ball under whichconditions the ball is free to control the admission of water through the inlet port and the perforated top-of the cage which willoccur when the level of the liquid in the overflow chamber drops slightly below the level of the main body of liquid in the boiler (see' Fig. 4.) One such type of thermostatic element that may be employed for the cage 26 is exemplified in the patent of W. L. Derby, No. 1,983,269, granted December 4, 1934. I

For providing access to the lower end of the coil and to the check valve therein, a screwthreaded plug 21 closes an opening in the wall of the overflow chamber in line with the inlet end of the coil. A manhole cover 28 is likewise provided to close an opening in the outer shell 2a in line with the plug 21 to afford accessibility to the plug from exteriorly of the boiler. Feeding into" the overflow chamber adjacent its upper end is a drain pipe 29 through which the hot condensate is returned from the piping system with which the steam generator is connected, such for example as a house heating system. The drain 1 pipe 29, as best shown in Fig. 3, is threaded through the outer shell 2a and through the wall of the overflow chamber. It will be understood boiler may be provided adjacent the bottom of the boiler, this ofitake pipe. (Fig. 2) leading off through the outer shell 3a in the lower boiler section. Manholes 33 suitablylocated in. this lower section allow access to the bottom of the boiler for the removal of accumulations of sediv ment from time to time. A water gage 34 and a safety valve 35 are provided in accordance with customary practice. v

The neck 2 extending up from the cover plate 2e closing the inner shell of the upper boiler section passes through the dome 2c of the outer shell as has been previously stated, and the clearance between the neck and dome is closed by a packing gland 36 arranged to effect a tight seal between the parts but permitting expansion and contraction of the inner shell.

Supported .upon. the upper end of the neck is a superheater 31. This 'superheater comprises a horizontally disposed metal drum 38 closed at both ends by end plates 39. rounding an opening through the wall of the drum intermediate its length telescopes over the upper end of the neck 27 which projects above the dome 20, thus afiording communication between the neck and the interior of the drum. 'A pair of laterally spaced partition plates 4| and 42 divide the drum into three compartments, name ly a steam inlet compartment at one end of the drum, an intermediate flue compartment which is in communication with the neck 2f through the sleeve 40, and a steam outlet compartment located at the other end of the drum. The steam inlet compartment communicates with the boiler through a pair of flanged couplings 43 which are bolted together and which together extend between'an opening in the dome 2c of the upper boiler section and an opening through the wall of the drum 38.

Extending through the flue compartment an opening through the partition plates 4| and 42 are a series of heat-transfer tubes 44 for the passage of steam from the steaminlet compart- A sleeve 4!! surment into'the steam outlet compartment. The flue compartment has an offtake 45 which may lead to a stack venting to the atmosphere. The arrangement is such that the flue gases from the coal fire on the grate 8 after having passed over the coils l2, l3 and I4 to which they give up a large part of their heat, flow up through the neck 2 into the flue compartment of the superheater where they give up a portion of their remaining heat to the steam passing through the heat transfer tubes 44. The steam issuing from the heat transfer tubes into the steam outlet compartment is therefore drier and hotter than when it entered such tubes. the steam outlet compartment 42 via a duct 46 leading off from this compartment and communicating with the house heating system. A bafile 41 is' suitably provided in thesteam inlet compartment in the path of the steam from the boiler to remove moisture carried in suspension, and such moisture may drain back into the boiler through the couplings 43.

This steam leaves The operation of the steam generator described above is as follows:

. The boiler I having been filled with water from the'water supply pipe 30 to a level somewhat below. the open tops of the overflow chambers l9, the 'flre under the coils is started to heat the comparatively small volume of water in the coils.

Steam quickly forms within'the coils anddischarges out of the upper ends of the coils (the valves I'l along with some of the water which it pushes ahead'of it. The water erupted from the upper ends of the coils spillsinto the overflow chambers while the steam passes upwardly through the couplings 43 into the superheater 31 on top of the boiler. Following an eruption of steam' from a coil, the check valve normally closing the lower end of the coil opens in response to the vacuum thus momentarily created to admit a small quantity of water from the overflow chamber into the coil to take the place of the steam and water lost from the coil.

These eruptions take place very rapidly and explosively so as to produce a sustained pulsating movement of water through the coils which is advantageous for several reasons; First, it prevents or at least materially retards the deposit of sediment or salts carried in the boiler Water upon the inside of the coils which would reduce the heating efficiency of the steam generator; second, it effectively scours away the minute bubbles of steam which tend to form upon and cling to the inner surfaces of the coils and seriously interfere with the transfer of heat through the coils; and, thirdly, the forceful circulation of water through the coils. serves to of the coils.

The water ejected from the upper ends of the coils into the overflow chambers reaches an elevatedv temperature after the apparatus has been inoperation fora short time, and actually may be just below the boiling point. This water is maintained by the overflow chambers segregated from the main body of'water contained within the boiler and is recirculated through the coils until it has been converted into steam.

The control valves 25 admit make-up water to the overflow chambers to take the place of that lost as steam from the coils. Each control valve, as has already been described, is so conlower ends of the coils being closed by the check I structed that when the temperature of the water within an overflow chamberreaches a suitably high temperature-the temperature of the water in the boiler theoretically will always be cooler than that in the overflow chambers when the apparatus is in] operation-the valve will become operative .to maintain the level of the water in the overflow chamber constant. That is, as water is drawn into the lower end of a coil following each steam eruption therefrom, the level of the water in its associated overflow chamber will momentarily drop relieving the pressure on the valve and as a consequence the unbalanced pressure of the water in the boiler and overflow chamber will lift the valve and permit additional water. to flow into the overflow chamber until the normal water level in the latteris restored.

This influx of water into the overflow chambers' ordinarily will occur with the same rapidity as the steam eruptions from .the coils, so that instead of the operation of the control valves being periodic they will actually operate at such a high speed as to produce a sustained pulsating flow of water from the boilerinto the chambers. An advantage of this thermostatic control ofthe valves is that it prevents a valve from opening while the water in the closed circulating system is still comparatively cool, and thus permits of more quickly starting up the steam generator from a cold condition.

Another feature which contributes to the efficiency of the steam generator just described is the special arrangement of the drain pipes 29 for returning to the overflow chambers, the condensate from the system towhich steam is supplied by the steam generator, as for example, a house heating system. Such condensate usually contains a substantial amount of residual heat and instead of being discharged into the main body of relatively cool water in the boiler is most effectively utilized by addition to the store of hot water awaiting immediate introduction into the coils.

The steam from the boiler passes up through the couplings Q3 into the steam inlet compartment of the superheater 31, thence through the heat-transfer tubes 44 into the steam outlet compartment and thence by way of the conduit 46 to the system to be supplied with steam. The steam in passing through the heat-transfer tubes is dried and raised in temperature by reason of the abstraction of heat from the hot flue gases which exteriorly bathe these tubes in their travel from the neck 2 through the flue compartment into the ofitake 45.

When, for purposes of cleaning, repair or shipment, it is necessary to dismantle the generator, this is accomplished as follows: The boiler having been emptied by means of the ofitake pipe 32 and the drain and water supply pipes 29 and 30 having been disconnected from the boiler, the bolts securing the couplings Q3 together are disconnected and the superheater is lifted off of its supporting neck 2 The connector tubes 5 are next unbolted from the upper and lower boiler sections and the tOp section 2 is lifted from the bottom section 3. The bolts 4 which fasten together the outer and inner shells 2a and 2b of the upper boiler section are next removed, and the outer shell 2a is rotated relative to the inner shell 21) until the cutaway areas 2h of the flange 2d register with the overflow chambers, under which conditions the outer shell may be removed from the inner shell. Finally, by unscrewing the bushings ldand 22 from the ends of the coils, thepcolls are detached from the inner shell 2b;;and may be withdrawn therefrom. When the steam generator :is to be reassembled, the above operationsare simply reversed. f

Manifestly the, invention is capable of embodiment in forms other thanthat described above whichis to be regarded as exemplary rather than as restrictive of the invention.

, I claim: I

1. In a steam generator,v a boiler adapted to contain a. liquidto be vaporized, an external heating coil having its ends. extending through the Wall of said boiler, one end of said coil being open, and'a check valve associated with the other end of the coil operable to admit liquid into the coil but prevent its discharge therefrom, means for-heating the coil, fan overflow chamber 10 cated within the boiler, said overflow chamber being open at its upper endfor the escape of steam therefrom and forminga receptacle. extending between the ends of the. coil forreceiving and confining liquid discharge from the open end ofthe coil andreturning it to the other end of the coil, and a control valve for admitting water from the boiler into. the receptacle while preventing reverse flow, I l

2. In asteamgenerator, a boiler adapted to contain a .liquid to be vaporized, an external heating coil having its ends extending through the 'wall .of said boiler at difierent elevations, the upper end of said coil opening into the boiler abovethefnormal level of the liquid therein and a checkvalve associated with the lower end of the coil operable to admit liquid into the coil but prevent its discharge. therefrom, means for heating the coil, an overflow chamber located within the boiler and forming a receptacle extending" below the normal level of the liquid in the boiler and adapted to receive and confine liquid discharged from the upper end of the coil,

said overflow chamber having communication with the lower end of the coil and serving to supply liquid to" the coil; a control valve for admitting liquid from the boiler. into the overflow chamber, andian outlet for steam from said over flow chamber. j r Y 3.'In'a steam generator, a boiler adapted to contain a liquid to be vaporized, an external heating coil having its ends extending through the wallof said boiler at different elevations, the u'p'perend of the coil opening into said boiler and a' check valve associated with the lower end of the coil operable to admit liquid into the coil but prevent'its discharge therefrom, means for heating the coil, an overflow chamber providing a receptacle :extendingfrom above to below the normal level" of the liquid in the boiler and adapted to. receive and confine hot liquid discharged from' the upper end of the coil, said overflow-chamber being in communication with the lower end of the coil and serving to supply liquid to the coil, a control valve for automati-.

cally admitting liquid fromthe boiler into the overflow chamber in response to variations in the pressure of the liquid in'the overflow chamber, and an outlet for steam from said overflow chamber. I

4. Ina steam generator, a boiler adapted to contain a liquid to be vaporized, an external heating coil having its ends extending through the wall of said boiler at different elevations, the upper end of the coil opening into the boiler and acheck-valve associated, with the lower end of the coil .operable to admit liquid. into the coil butprellent its discharge therefrom, means for a receptacle extending from above tobelow the normal level of the liquid in the boiler and adapt ed to receive and confine liquid discharged from the upper end of the coil, said overflow chamber being in communication with the lower end of the coil. and, serving to supply liquid tdthe coil, and an outlet for steam adjacent the upper end of said overflow chamber, a control valve for automatically admitting liquid from. the boiler into the overflow chamber in response to variations in the pressure of the liquid in theoverflow chamber and temperature-responsive means for rendering the control valve operative; p v 5. In asteam generator, a boiler adapted to contain a liquid to be vaporized, an external heating coil havingits ends extending through the wallof said 'boilerat diiferent elevations, the upper end of the coil opening into the-boiler and a check valve associated with the lower end or, the coil operable to admit liquid into the coil, but prevent its discharge therefrom, means for heating the coil, an overflow :chamber providing a receptacle extending from above to below the normal level communication with the lower end of the coil andserving to supply liquid to the coil, and an outlet for steam adjacent the upper end of said overflow chamber, and a condensate-return pipe extending to exteriorly of the boiler and communicating with the overflow chamber.

6.-In a steam generator, an annular boiler adapted to contain a liquid to be vaporized, an external heating coileentrally located with respect to the boiler and extending through its wall, one end of the coil opening into the boiler and a check valve associated with the other end of the coil operable to admit liquid into the coil but'prevent its dischargetherefrom, means for heating the coil, an overflow chamber immersed in the liquid contained in the boiler, said overflow chamber having an open top located above the normal level of the liquid inthe boiler and adjacent the open end of the coil-to receive and confine liquid discharged from the coil, means providing communication between the overflow chamber and with the other end of the coil, and afcontrol valve for automatically admitting liquid from the boiler into the overflow chamber to maintain a constant volume of liquid therein.

, JOHN H. BROWN.

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