CA1087470A

CA1087470A - Boiler

Info

Publication number: CA1087470A
Application number: CA303,288A
Authority: CA
Inventors: Hans Viessmann
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-05-14
Filing date: 1978-05-15
Publication date: 1980-10-14
Also published as: ATA329678A; BE866913R; LU79658A1; CH635189A5; IT1109174B; FR2390681B2; FR2390681A2; NL7805147A; IT7823371A0; AT378257B

Abstract

BOILER

Abstract of the Disclosure The fire box unit inserted into a water casing of a boiler includes a tubular cast iron body fluid-tightly mounted in the apertures of the end walls of the steel sheet casing. The cast iron body is shaped to converge frusto-conically from its inlet to its outlet end and has a plurality of radially inwardly extending webs. A com-bustion chamber shell is mounted in the inlet end of the cast iron body and has a fuel burner inlet for burning a fuel in the chamber defined by the shell. A closure wall opposite the fuel burner inlet deflects the combustion gases of the burnt fuel towards the fuel burner inlet where the deflected gases are received in a gas guide chamber.
The shell with the gag guide chamber and a gas collecting chamber adjacent the closure wall at the outlet end of the cast iron body is supported on the webs and defines therewith gas flues leading from the gas guide to the gas collecting chamber. The gases in the flues heat the water in the casing and condensate tends to form in the bottom region of the tubular cast iron body protruding beyond the end walls of the casing. A shoulder damming the flow of the condensate in the gas flues in the end regions.

Description

374~
The presen-t inventi4n ~late~ to improvements in the boiler for heating water, disc]osed in my copending Canadian Patent Application Serial No. 288,355, filed October 7, 1977, and en-titled "~eating Boiler for the Combustion of Liauid or Gaseous Fuel".
The boiler comprises a casing for holding the water to be heated and including two end walls defining apertures and a side wall e~tending between the end walls, the casing walls being of steel sheet. A fire box unit is inserted in the casing and includes a tubular cast iron body mounted fluid-tightly in the apertures of the end walls of the casing, the cast iron body hav-ing an inlet end and an outlet end protruding beyond the end walls and having a plurality of radially inwardly extending webs distributed over the circumference of the tubular body. A com-bustion chamber shell is mounted in the inlet end of the tubular cast iron body, the shell having a fuel burner inlet for burning a liquid or gaseous fuel in the combustion chamber defined by the shell and a closure wall opposite the fuel burner inlet ; whereby the combustion gases of the burnt fuel are deflected back towards the fuel burner inlet. A gas guide chamber at -the fuel burner inlet receives the deflected gases and a gas collecting chamber is adjacent the closure wall at the outlet end of the cast iron body. The shell with the bas guide and collecting chambers is support3d on the radially inwardly ex-tending webs of the cast iron body and defines therewith gas flues leading f~rom the gas guide to the gas collecting chamber.

~' " . .

-2-!

`: . . . . .. ~ ~ . . ~ .. .

~` . . . . .
., . . . ~. .

~1387~L73~

The points of conn2ction between the ca~t iron bocly and the ~teel sheet casing are not machined and the good malleability of the sheet steel i~ combined with the cast iron body so that no welding is required for providing a fluid tight connection therebetween while the integral ca~ting of the radial webs with the tubular body provides the required ducts for the flue gases.
The combination of a ~teel sheet casing holding the water and a cast iron fire box unit inserted therein has the advantage that the casing may be readily connected to one or more ho-t water storage chambers, which ls practically impossible with an all-cast iron boiler because of the resultant complexity of the castings and the problems of providing fluid tight connections. Furthermore, this combination makes it possible to arrange several superposed cast iron fire box inserts in the water casing and to operate with separate ~uel burners so that it iq possible to operate a selected number of t~ese units, depending on the hot water requirements.
Operation of this advantageous boiler di;,closed in my copending application has shown that, while the gases in the flues heat the water in the casinc~, condensate tends to form in a bottom re~ion o:f the protruding ends of the tubular cast iron body in the gas flues.
In accordance with this invention, the boiler has been improved by shaping the tu~ular cast iron body to converqe frusto-conically from the inlet towards the outlet end, and `. .

' :

~87g~70 a shoulder dams the flow of the condensate in the botto~
region of at least the protruding lnlet end of the tubular cast iron body.
~ en a boiler of the indicated type is operated at different tempera-tures, a considerable amount of condensate will form in the ducts for the flue gases. I-t has proved to be very difficult to seal the connections between the end walls of the water casing and the fire box unit fluid tightly enough to prevent escape of condensate through the gasket. The condenqate tends to corrode and destroy the gaskets since it consists ,of sulfuric acid or sulfurous acid. If it passes out of~the gas flues, it will run down the steel sheet wall of the casing and ~r.roy the same or the insulating jacket surrounding it, : .
The above and other ob'jects, advantages and f2atures, of the invention will become more apparent from t~e following , :
detailed description of certain no~,~ pre~erred embodiments :
thereof, taken in conjunction with the accompanying schematic .:
drawing wherein '~::

I FIG. 1 shows on~ embodiment of the boiler in longi-tudinal cross sec-tion throug~ e axis of the boiler, , :~
FIG~ 2 is an end view of the boiler, partly ~ transverse ~ , ,,-cross section FIGS. 3, 4 and 5 are sim~lified long:itudinal sections o~
modified embodiments of the boiler, FIG. ~ is a partial longitudinal section o a port.ion ~'l of the boiler showin~ a modified detai.l, and . ! , ;
~ -:

' ~' -., ' - . - i ,~ - , : - . .: :
. - ~ - :
.

747~

FIG. 7 is a like partial section illustrating another rnodified detail~
Referring now to the drawing wherein like reference numerals desi~nate like parts functioning in a like manner in all figures, FIG. 1 shows the essential parts of a boiler for heating water according to the present invention.
This boiler comprises casing 29 for holding water to be heated and including end walls 3 and 4 each defining central apertures arranged concentrically about axis 31 of the boiler and side wall 12 extending between the end walls.
The casing walls are of steel sheet.
Fire box unit 1 is inserted in casing 29 and surrounded thereby. ~e fire box unit includes tubular cast iron body 2 mounted fluid-tightly in the apertures of end walls 3, 4 of casing 29 in a manner to be described hereinafter~ Cast iron body 2 is also arranged concentrically about boiler axis 31 and has inlet end 22 and an outlet end. The ends of the cast iron body protrude beyond end walls 3 and 4, and body 2 is shaped to converge frusto-conically from tha inlet toward3 the outlet end. As best sho~n in FIG. 2, a plurality o~F radially inwardly extending webs 9 are distributed over the circumference of tubular body 2, projecting from interior wall 5 of cast iron body 2 and being cast integrally therewith~
Combustion c~amber shell 7 is mounted in ~et en~ 22 of tubular cast iron body 2 and has a fuel ~urner inlet 13 for burning a ~aseous or li~uid fuel in the combustion ctlamber :
. .

.~ i : ', ~ .

~ ' :

~ ~ ` . . . . .
: . . , . . ~.

~4i 87~

defined by shell 7 ( the fuel burner not being shown ).
Clo~ure wall 14 opposite fuel burner inlet 13 deflects the combustion ga~es of the burnet fuel back towards the fuel burner inlet where gas guide chamber 10 receives the deflected gases, this chamber having a somewhat larger diameter than the combustion chamber. Gas collecting cham~er 11, which also ha~ a larger diameter than the combustion chamber, i~ adjacent closure wall 14 at the outlet end of cast iron body 2. The shell with the ~as guide and col~
lecting chambers i9 supported on radially inwardly extending webs 9 of cast iron body 2 and defines therewith gas flues 15 leading from ~a~ guide chamber 10 to gas collecting chamber 11. In view of the enlarged diameters of the gas guide and collecting chambers, webs 9 are higher in the center region supporting the portion of shell 7 defining the combustion chamber than in the end regions 9' of the webs so that ends " :: :
30 of ~he webs support the shell in ~he cast iron body, the ~hell being readily removably by sliding it along the supporting ends of the webs which hold ~he shell in position.
The ~héll may be o~ stainless steel.
The hot ga~es flowing in flues 15 Erom guide chamber 10 to collec~ing chamber 11 heat the water in the annular chamber defined between tubular cast iron body 2 and casing 29.
Particularly when the boiler is operated at changing temperatures, condensate will inevitably tend to form in the bo-ttom region of the tu~ular cast iron body in the gas ~lues~

; , :

. IL

. , ` :
` ` ` . `
`
:

~1379~7~

To prevent such condensate to reach gas~ets 34 which are interposed as a fluid-tight seal between I-he inlet and outlet ends of the cast iron body and closures 33 mounted thereover, shoulder 23 dams the flow of the conden~ate in the bottom region of the protruding inlet end 22 of the tubular cast iron body, the illustrated e~bodiments showing a like condensate damming shoulder 23' at the outlet end.
In the embodiment of FIG. 1, closure 33 at the outlet end is integral with flue connection 24 for removing the flue gase~ from gas collecting chamber 11. Inqulating collar 16 is mounted on inlet closure 33 and surrounds the fuel burner ~not shown) whose flame projects therethrough.
In the absence of shoulders 23, ~ ', conden3ate would flow into contact with gaskets 34 and would eventually des- -troy them. The conicity of tubular cast iron body 2 assures flow of the condensate formed particularly in the bo-ttom half of the boiler towards the inlet end which is in contact with the hottest part of the combustion gases. ~nis will facilitate evaporation of at least a portion of the condensate.
The lower the temperature of the gases, the higher the deg~e~
of condensation, i.e. the flue gases tend to condensate mostly towards the outle-t end, i.e. in the region of gas collecting chamber 11. Therefore, it is advantageous to assure flow of the condensate from that region towards the inlet end, i.e. into the gas guide chambe~ , wherein the temperature i~ hottest. As indicated, the conicity OL th~
-tubular cast iron bod~ forces this con~ensate flow even if it 7 1 ~:
., ' ''"' '".
, `; ' : ~ ' :

~87~
e~tends onl~ over three fourths or two thirc~s of -the len3th of tu~ular body 2 and the remaining length of the body at the inlet end is cylindrical.
If the tubular cast iron body of the fire box unit is frusto-conical along its entire length, i-t may be use~ul to shape the central portion of the shell d~fining the combustion chamber accordingly. Such an embodiment is shown in FIGS. 3 and ~ where shell portion 7' is frusto-conical and extends parallel to tubular cast iron body 2.
For this purpose, suppor-t ends 30' of radially extending webs 9 are similarly inclined from the inlet towards the outlet end so as to positio~ shell 7' coaxially in the boiler~
Su~h a cast iron unit may be cast with a "green" core, i.e. the body would be shape~ and cast vertically. Since all walls are conical and if the webs are thinner in front than in back, the form may be so prepared that the core is formed of sand in the interior. This make~ it possible to cast the body with a su~stantially dome-shaped end wall 33' (see FIG. 4) at the outlet end there~y body 2 assumes a be71 shape. A suitable opening may ~e cast into the dome-shaped erld wall to receive flue 2~' extending from the end wall for removing the gases from gas collectin~ chamber 11. The manufacturing cost of casting such a unit are le~s than when the tubular body has to be cast with separately prepared cores, which is neces3ary wlth cylindrical interiors.
The fire box unit i9 fluid-tightly connected with water casing 2~ without weldin~, which is very advantageous ~ecal~se welding steel sheet to cast iron is rather dif,icult ancl

3 i~ :

, ~87~7~ .

does not assure a fluid tight seal in -~iew o:F the difference in the thermal expansion coefficient be~ween the two materials.
One preferred fluid-tig}lt connection according to -this inven-tion is shown in FIG. 1. In this preferred embodiment of the connection, tubular cast iron body 2 has machined annular circumferential regions 25 and end walls 3, 4 of casing 29 having corresponding annular rims 26 forming a press or friction fit with the machined reyions of the cast iron body, Sealing medium 27 forms a fluid-ti~ht interface between the machined regions of the cast iron body and the annular rims of the steel shset end walls. The sealing medium may be a hea-t- and liquid-resistant putty which ', also operates as a lubricant. To provide the required friction fit, the inner diameter oF rim 26 is slightly less than the outer diameter of tubular body 2 at the machined regions.
The cast iron body has annular collars 28 adjacent machin~d reglons 25 to form abutments for end walls 3, 4 of t-he casing.
FIG. 6 illustrates a less desirable fluid-tight connection wherein end walls 3, 4 of casing 29 are threadedly connected with annular collars of the cast iron bocl~, with sealing ri~gs - ,, ox gas~ets making the threacled connection fluid-tight. This produces a fluid-tight but detachable connection ~etween ~ '' the steel shee-t walls of the casing and the cast iron kody , of the fire box unit~ ~' ~ o avoid su~jec~ing ~-teel shcet casing 29 to t'he~ load caused by mounting closures 33 on the boiler, cast iron body 2 is cast ~ith parts 32, 32' for affixinc3 the closures I
`~ to the cast iron bocly, ~or example hingedly. In t~.is manner, ' , :.,:

9 ~ ~:
'' - ' : -:

~.

~7~7~
the cast iron body is the carrier oE the boiler closu-es.
This makes the entire manufacture of the boiler more economical.
In ~he embodiment of FIG. 5, cast iron body 2 is shown to be conical only over part of its length while being cylindrical near the inlet end. In this e~mbocliment, the shell defining the combustion chamber may be cylindrical, as in FIG. l. As long as the tubular ca~t iron body tapers inwardly toward the outlet or colder end of t~e fire box unit, it has the advantage that t.he volume of the colder gas is reduced in relation to the volume of the hot-ter gas.
~ IG. 7 shows a modified emhodiment o the fluic1~tight connection between steel sheet end walls 3, ~ and tuhular cast iron body 2. In this e~.~bodiment, machined annular region 25' of tubular body 2 i5 frusto-conical and rim 2~' of the end wall is correspondingly frusto-coni~al to provide a press or friction fit therebetween. The tubular body has a slight circum~erential shoulder 25" spaced from machined re~ion 2S' by an annular groove~ The outer dlamet-er of shoulder 25"
is between the inner and ~uter d.iameters of rim 26'. In this manner, when rim 26' is moved against collar 28 for frictional enga~emen-t with machi~ed annular region 2S', the `
rim snaps lnto position over shoulder ~ and is thus securely positioned. I~ any leak should ever develop at this co.nnection, it may be readily repaired by placing a sealin~
tape thereover.
~ hile tubular ~ody 2 has heen illu.strated .15 C~/L'ndriCcl lt may be oval in cross sectlon.

..

'.' ' : ' , ~

Claims

What is claimed is:

1. A boiler for heating water, comprising (a) a casing for holding the water to be heated and including (1) two end walls each defining apertures and (2) a side wall extending between the end walls, the casing walls being of steel sheet, and (b) a fire box unit inserted in the casing and including (1) a tubular cast iron body mounted fluid-tightly in the apertures of the end walls of the casing, the cast iron body having an inlet end and an outlet end pro-truding beyond the end walls, being shaped to converge frusto-conically from the inlet towards the outlet end, and having a plurality of radially inwardly extending webs distributed over the circumferences of the tubular body, and (2) a combustion chamber shell mounted in the inlet end of the tubular cast iron body, the shell having a fuel burner inlet for burning a fuel in the combustion chamber defined by the shell, a closure wall opposite the fuel burner inlet whereby the combustion bases of the burnt fuel are deflected back towards the fuel burner inlet, a gas guide chamber at the fuel burner inlet for receiving the deflected gases, a gas collecting chamber adjacent the closure wall at the outlet end of the cast iron body, the shell with the gas guide and collecting chambers being supported on the radially inwardly extending webs of the cast iron body and defining therewith gas flues leading from the gas guide to the gas collecting chamber, the gases in the flues heating the water in the casing and condensate tending to form in a bottom region of the tubular cast iron body in the gas flues, and a shoulder damming the flow of the condensate in the bottom region of at least the protruding inlet end o' the of tubular cast iron body.

2. The boiler of claim 1, wherein the combustion chamber shell converges conically from the inlet towards the outlet end, the radially inwardly extending webs having support ends defining a correspondingly conical support for the shell.

3. The boiler of claim 1, wherein the cast iron body comprises a substantially dome-shaped end wall at the outlet end whereby the body assumes a bell shape, and further comprising a flue extending from the dome-shaped end wall for removing the gases form the collecting chamber.

4. The boiler of claim 1, wherein the cast iron body has machined annular circumferential regions and the end walls of the casing have corresponding annular rims forming a friction fit with the machined regions of the cast iron body.

5. The boiler of claim 4, further comprising a sealing medium forming a fluid-tightly interface between the machined regions of the cast iron body and the annular rims of the steel sheet end walls.

6. The boiler of claim 4, wherein the cast iron body has annular collars adjacent the machined regions to form abutments for the end walls of the casing.

7. The boiler of claim 1, wherein the cast iron body has annular collars for fluid-tightly but detachable connec-tion with the steel sheet end walls of the casing.

8. The boiler of claim 1, wherein the tubular cast iron body comprises integrally cast parts at least at one of the ends thereof, and further comprising a closure affixed to the cast parts.

9. The boiler of claim 1, wherein the cast iron body has frusto-conical machined annular circumferential regions and the end walls of the casing have corresponding frusto-conical annular rims forming a friction fit with the machined regions, the tubular body also having circumferential shoulders spaced from the machined regions. the outer diameter of the shoulders being between the inner and outer diameters of the rims.

10. The boiler of claim 9, wherein the cast iron body defines an annular groove spacing the shoulder from the rim.