CA1081570A

CA1081570A - Fuel burner

Info

Publication number: CA1081570A
Application number: CA276,860A
Authority: CA
Inventors: Gerald Shields
Original assignee: Modine Manufacturing Co
Current assignee: Modine Manufacturing Co
Priority date: 1976-08-16
Filing date: 1977-04-25
Publication date: 1980-07-15
Also published as: IT1078277B; GB1518786A; FR2362344A1; DE2721481A1

Abstract

Abstract of the Disclosure A fuel burning heater comprising a burner for hydro-carbon fuel that produces corrosive products generated by the burning of the fuel, a heat exchanger for the corrosive products comprising sheet metal having a core of a corrodible first metal and surface coatings exposed to said corrosive products of a corrosion resistant second metal, and lock seam joints uniting the sheet metal at the margins. Each lock seam comprises corrod-ible edges each surrounded and encased by margins of adjacent sheet metal in lapped contact so as to be substantially gas tight at the corrodible edges. An example of such a metal sheet is a soft steel sheet with a ferritic stainless coating ("chromized").

Description

~0~3~570 : ` FUEL BURNER
, B ackground o~ the Invention In fuel burning heaters that burn a hydrocarbon fucl there are produced corrosive heat generated gaseous products that are corrosive to ordinary steel. These corrosive products attack metals particularly at the joints where the joints are the usual welded, soldered, brazed or similar joints.
In order to solve this problem of corrosion from the gases it has been proposed to make these exposed metal parts such as heat exchanger flues entirely of stainless steel. This, o course, is expensive and joining stainless steel parts to each other presents problems.
The present invention solves these problems of handling the corrosive products generated by the heat or by the ~ombustion of a contaminated fuel by providing a sheet metal construction in those parts of the heater that are contac`ted by the corrosive products with the sheet metal having a core of a corrodible first metal that is relatively inexpensive and strong such as steel and an exposed surface coating of a corrosion :~
resistant second metal such as stainless steel. The core is exposed at the edges and the parts are joined with lock seam joints each comprising the exposed corrodible edges surrounded and encased by margins of an adjacent sheet and in intimate contact so as to be substantially gas tight at these edges and thereby protect the edges Erom corrosion by the gases. This construction is very efficient and relatively inexpensive and avoids welding, brazing, soldering or similar joining methods.
SUMMARY OF INVENTION
. . _ Thus broadly, the invention pertains to a fuel burning heater which includes a burner for hydrocarbon fuel which produces corrosive products by burning the fuel. The heater also includes a heat exchanger comprised of sheet metal parts including flues and headers. The sheet metal parts in contact ~ F~,D, `-`

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with the corrosive products are comprised of a sheet core of a corrodible firs-t metal with opposite surface coatings of a corrosion resistant second metal. The first metal is only exposed at the edges of the sheet metal and lock seam joints.
Each joint unites one sheet metal part to an adjacent sheet me~al part at adjacent margins of the respective sheets. Each lock seam comprises a corrodible edge of the one sheet metal part surrounded and encased by the mar~irl of the a~ jacellt slleet metal part. Similarly, a corrodible edge of the adjacent sheet metal part is surrounded and encased by the margin of the one sheet metal part. The adjacent margins are in intimate surface contact so that the joint is substantially gas tight.
Brief Description of the Drawings Figure 1 is an elevational view partially broken away ~or clarity of illustration of a space heateI^ cll~oclylng tllc invention.
Figure 2 is an enlarged fragmentary sectional view through one embodiment of a lock joint of this invention.
Figure 3 is a view similar to Figure 2 but illustrating a second embodiment.
Figure 4 is an enlarged fragmentary sectional view through a sheet metal structure used in the lleater of tllis invention.
Description of_the Preferred Embodiments A space heater embodying the invention is shown in fragmentary perspective view in Figure 1. This space heater 10 comprises a cabinet 11 with the customary adjustable deflector blades 12, a motor (not shown) operated fan 13 adapted to draw room air in through a cabinet inlet 14 and expel it af-ter being heated through the air outlet 15 where the direction of the air flow is controlled by the positions of the deflector blades 12, Spaced burners 16 at the bottom of the unit are for burning a hydrocarbon fuel and especially hydrocarbon gas with each burner 16 having an upwardly directed port 17 for the gases of combustion

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Jhich are received from each burn~r lG in~o the lower ends 18 of vertically extending flues or tubes 19.
The upper 20 and lower 18 ends arc connectcd to trans-verse lower 21 and upper 22 header plates that are ~nerally horizontal and parallel to each other. The top of the cabinet 11 above the hcader plate 22 is provided with an an~led deflector plate 23 for directin~ ~he ~aseous corrosive products awa~ from the inlet 1~ to the heat e~changer. The bottom of the cabine~ is providcd ~ith spaced sccondary air inlets 2~.
The burnill~ of the hydrocarbon fuel c3enerates corrosive produets either from the fuel, th~ air or fluids in the air. These tend to attack and destroy soft steel particularly at welded, soldered or brazed joints. As stated above, this problem could be solvcd by using parts that are entirely stainless steel but these present problems of joining and ar~ expensive. The presellt invell-tion solves this problem by providing a metal s~leet that has the construction illustrated schematically only in Figure ~. This sheet eomprises a core 25 with exposed edges 26 of a metal such as soft steel that is susceptible to attack by these corrosive 20 products but that has the advantage of being relatively inexpensive.
The core 25 contains a eorrosion resistant coating 27 of a metal such as stainless steel that is resistant to these corrosive produets. ~he thickness of the core and ~e coatings which are on both sides of tile core are shown exacJgerated in Fic3ure ~ for clarity o illustration.
Adjacent sheet metal parts such as the headers 21 and 22 and the flues 19 are joined in the manner illustrated in Figures 2 and 3 in enlarged detail by a lock seam joint 28 which is strictly mechanical and avoids thc use of brazinc3, soldering, weldincJ or 30 similar joining mc~lods. Sucll seclms also incluclc loncJ:itudincll seams 34 of the flues 19. Each lock seam 28 comprises the c~posed corrodi~lc edc3e 26 of one sheet such as thc flue 19 sheet surroundccl .. . .
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and encased by a folded over margin of a second sheet such as the header 22. Sufficient lateral pressure is applied as illus-trated by the pressure arrows 32 so as to make the lock seam joint substan~lly gas tight thereby protecting the exposed edge 26 from subst~ntial contact with the gaseous corrosive products.
The exposed edge 26 of this adjacent sheet is similarly protected by a similar margin lock joint. The lateral pressure 32 of course serves to encase both of the margins 26, as illus-trated in Figure 2, so that the effect is to have a lock joint 10 of interdigital construction which protects the edges of both ' adjacent metal sheets 19 and 22 with the remainder of ~e sheets of course being protected by the corrosion resistant coatings 27.
Figure 2 illustrates the embodiment in which the lock seam joint between the flue or tube 19 and the header illustrated at 22 is flat against the header sheet 22 and at right angles to the tubes 19. Figure 3 is a different embodiment in which the seam joint parts are directly opposite their location in Figure 2.
Here the lock seam 28 is flat against or superimposed on the flue 19 and at right angles to the header 22. The indi~idual flues 20 or tubes 19 may be formed by joining adjacent edges of the sheet metal making up the flue in a longitudinal seam 34 which of course has the lock seam construction illust.rated at 28.
Having described my invention as related to the embodi-ments shown in the accompanying drawings, it is m~ intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the appended claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fuel burning heater, comprising: a burner for hydrocarbon fuel producing corrosive products generated by the burning of the fuel; a heat exchanger comprising parts of sheet metal including flues and headers contacted by said corrosive products, said sheet metal of said parts comprising a sheet core of a corrodible first metal and opposite surface coatings of a corrosion resistant second metal with the first metal being exposed only at the edges of the sheet metal;
and lock seam joints, each joint uniting one sheet metal part to an adjacent sheet metal part at adjacent margins of the respective sheets with each lock seam comprising a corrodible edge of said one sheet metal part surrounded and encased by the margin of the adjacent sheet metal part; and a corrodible edge of said adjacent sheet metal part surrounded and encased by the margin of the said one sheet metal part and with said adjacent margins in intimate surface contact so that said joint is substantially gas tight.

2. The heater of claim 1 wherein each said lock seam joint is superimposed on one metal sheet and at an angle to the adjacent metal sheet.

3. The heater of claim 1 wherein said sheet metal parts of said heater comprise a plurality of vertical flues with opposite open ends and each flue located above a burner with means on the burner for ejecting and directing its said gaseous corrosive products upwardly into said flue, the heater including upper and lower header plates to which said ends of said flues are joined by said lock seam joints,

4. The heater of claim 1 wherein said sheet metal parts of said heater comprise a plurality of vertical flues with opposite open ends and each flue located above a burner with means on the burner for ejecting and directing its said gaseous corrosive products upwardly into said flue, each said flue comprising said sheet metal having side edges overlapped and joined by a said lock seam joint.

5. The heater of claim 1 wherein said sheet metal parts of said heater comprise a plurality of vertical flues with opposite open ends and each flue located above a burner with means on the burner for ejecting and directing its said gaseous corrosive products upwardly into said flue, the heater including upper and lower header plates to which said ends of said flues are joined by said lock seam joints, each said flue comprising said sheet metal having side edges overlapped and joined by a said lock seam joint.