CA2423371A1

CA2423371A1 - Chimney with heat resistant anti-oxidant coating

Info

Publication number: CA2423371A1
Application number: CA 2423371
Authority: CA
Inventors: Charles Perrault
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-03-26
Filing date: 2003-03-26
Publication date: 2004-09-26

Abstract

The invention relates to an chimney, for example: a double or single wall chimney for a combustion heaters, with relatively thin walls and interior surfaces that are exposed to combustion gases coated with a heat resistant anti-oxidant coating.

Description

a [0001] Chimneys have been used for exhausting the bi-products of. combustion heaters in dwellings for the purposes of heating water, cooking, creating steam and many other functions. The present invention described herein using the example of an insulated thin metal double wall chimney for exhausting combustion gases, it will be understood that the invention is applicable to exhausting flue gases of many types of heating appliances, such as oil, gas, pellets, corn, propane, and biogases, used to heat air or liquids in domestic, commercial or industrial applications>

[0002] For the most part, the primary function of a manufactured insulated chimney is for the safe exhaustion of heat, moisture and combustion gases, each chimney segment tightly joined without leaking undesirable byprc;ducts of combustion into the dwelling.

[0003] In order to have a safe exhaust means, manufacturers usually provide a tubular, single or double walled metallic shell, in order to shield hot gases from combustibles. Prior art chimneys, the interior being unprotected metal such as stainless steel or the like, and as a result of the ever present acids, heat, creosote and moisture, in time will deteriorate through corrosion, resulting in an unsafe chimney.

[0004] The objects of the invention will be apparent from review of the disclosure, drawings and description of the invention below, and in reference to my previous US Patent Application, 09/868,728 which employs the same technology.
DISCLOSURE

[0005] A chimney for exhausting combustion gases from burning fuel, generally in the form of a circular tube and joined together in a suitable manner with metal bands or screws. The enclosure has an exterior wall exposed to ambient air, an interior wall exposed to flue gases and may have insulation between these walls defining a chimney. The top and bottom ends form a sealing enclosure between the inner and outer walls. The interior surface of the chimney is coated and joints are sealed with heat resistant anti-oxidant material, for example:
porcelain enamel, having a co-efficient of thermal expansion not substantially greater than the co-efficient of thermal expansion of the enclosure.

[0006] Since moisture and acids cannot penetrate the porcelain enamel coating, such a flue pipe is impervious to the hostile environment which is detrimental to bare metal . The coating does not tend to creep and porcelain enamel coated metal will flex with the metal. Porcelain enamel"s compressive strength is in the range of 20,000 psi.

[0007] Porcelain enamels possess excellent corrosion resistance in a variety of corrosive environments, including exposure to heat, combustion gases and corrosive wood burning fumes and the acids of natural gas. Long-term weathering tests conducted by the U.S. National Bureau of Standards (NBS) and the Porcelain Enamel Institute (PEI) confirm the resistance of porcelain enamel coated metals to various atmospheric conditions including corrosive industrial atmospheres, gases, smoke, salt spray and sea coast exposure. Porcelain enamel surfaces can be readily cleaned after such exposure and changes in appearance are almost imperceptible, especially among those coatings formulated to have a high degree of acid resistance resulting in a product that will not deteriorate and with a higher degree of safety.

[0008] Thin porcelain enamel coatings have very good flexibility and adhesion when applied to thin metal substrates.
For example, a 10-mil commercial steel sheet with two porcelain enamel coatings 5-mils thick is so flexible it can be shipped in 12-inch diameter coils without damage. Experimental porcelain enamels applied at a thickness of 1.5-mils to steel sheet 4-mils thick have been deformed to a radius of 1.5-inches without damage to the coating. Porcelain enamel coatings will flex with the base metal until the metal is permanently deformed.

[0009] The development of thinner coatings has increased the role of the base metal's mechanical properties, providing more flexibility, less brittleness and greater chip resistance.
Porcelain enamels, regardless of thickness, provide outstanding wear resistance and abrasion resistance, while also contributing to the strength of the metal substrate.

[0010] Lubricity of conventional glossy porcelain enamels is perhaps the highest of any known finish except the "no stick"

fluorocarbons. This feature enables self-cleaning or elimination of deposits in the chimneys interior.

[0011] The sheet steel is typically a mild steel with low carbon content which lends itself to the heat resistant anti-oxidant coating process which must be carried out in an oven at temperatures approaching 1600° F. The heat resistant anti-oxidant coating may selected to be a high temperature porcelain enamel or glass which contains a small amount of titanium (up to about 80) which tends to have the effect of making the interior heat resistant anti-oxidant coating surface of the chimney self cleaning. The heat resistant anti-oxidant coating and the metallic sheet steel base material must have complementary co-efficient of expansion that are selected in order that the heat resistant anti-oxidant coating steadfastly adheres to the base material during the many temperature excursions to which the heat resistant anti-oxidant coated sheet steel will be subjected over the life of the chimney. A variation in the choice of metal for the substrate will usually dictate a corresponding Variation in the coating to ensure that the coating is not subjected to excessive residual tension or residual compression as the metal substrate and the coating cool after firing or plasma arc deposition is completed.

(0012] The chimney is provided with male and female joints, and are joined together in such a fashion so as to be fundamentally air tight.

[0013] The chimney has top a top fitting to prevent moisture from entering and may have a bottom fitting for clean out and connector for joining the chimney to a heater.

[0014] The chimney also may have elbows and brackets to form a complete and secure flue gas exhaust means where interior surfaces of the chimney which are exposed to the hot exhaust gases are coated with a suitable heat resistant anti-oxidant coating such as porcelain enamel or glass material. This same anti-oxidant coating can be used on single wall pipe.

[0015] This anti-oxidant coated chimney used together with the anti-oxidant interior coated stove (Charles Perrault, US
patent 09/868,728) offers the highest degree of safety, efficiency, and forming an exhaust means not affected by corrosion or acids and will allow coastal communities to burn thousands of cords of salt water wood found on beaches.

[0016] The shape of chimney has been chosen to be as nearly cylindrical as is possible in order to achieve ease of manufacturing. Other shapes such as square, elliptical and polygonal are entirely possible.
DESCRIPTION OF THE DRAWINGS

[0017] In order that the invention may be readily understood, two embodiments of the invention are illustrated by way of example in the accompanying drawings.

[0018] Figures 1-3 show a first embodiment of the basic invention in a double wall chimney. Figure 4 shows a second embodiment with single wall pipe. Figure 1 is a perspective view of a chimney in accordance with a first embodiment of the invention.

[0019] Figure 2 is a top view of the chimney of Figure 1.

[0020] Figure 3 is a partial sectional view of the chimney in Figure 1.

[0021] Figure 4 is a perspective view of a single wall chimney in accordance with a first embodiment of the invention.

(0022] Figure 5 is a partial sectional View of the chimney in Figure 4.
[0100] Although the above description relates to a specific preferred embodiment as presently contemplated by the inventor, it will be understood that the invention in its broad aspect includes mechanical and functional equivalents of the elements described herein.

_ -Drawing Numbers 11. Flue chamber 13. Porcelain coating 14. Interior wall 15. Exterior wall 16. Insulation

Claims

1. A chimney for exhausting flue gases from burning fuel comprising:

a tubular enclosure with an inlet, and an outlet, the enclosure having an interior wall exposed to flue gases and an exterior wall exposed to ambient air defining a chimney, wherein:

the interior surface of the chimney is coated with heat resistant anti-oxidant material having a co-efficient of thermal expansion not substantially greater than the co-efficient of thermal expansion of the enclosure.

2. A chimney according to claim 1 wherein. the exterior surface, top and a bottom flanges of the chimney, are coated with heat resistant anti-oxidant material having a co-efficient of thermal expansion nct substantially greater than the co-efficient of thermal expansion of the enclosure.

3. A chimney according to claim 1 wherein the heat resistant anti-oxidant material is selected from the group consisting of:
glass; porcelain enamel and ceramic.

4. A chimney according to claim 1 wherein the enclosure is of ma=serial selected from the group consisting of: a decarburated steel; a low carbon mild steel; a sheet metal; a cast metal; a forged metal; and a welded metal assembly.

5. A chimney according to claim 1 wherein the heat resistant anti-oxidant material has a thickness of 3 mil to 10 mil.

6. A chimney according to claim 3 wherein the porcelain enamel includes up to 20 percent feldspar by weight.

7. A chimney according to claim 6 wherein the refractory material is selected from the group consisting of: feldspar; and silica.

8. A chimney according to claim 1 comprising:

an outer casing, an inner flue pipe having top and bottom openings;

with a top flange and a bottom flange fitted into the top and bottom ends defining joints therebetween, wherein the heat resistant anti-oxidant coating on the inner wall sealing said joints.

9. A chimney according to claim 8 wherein the inner and outer walls are constructed of sheet metal.

10. A chimney according to claim 8 wherein the ends have peripheral flanges parallel to and engaging the interior and exterior walls of the chimney.

11. A method of manufacturing an insulated chimney for burning fuel comprising:

an outer casing, an inner flue pipe, with an flue gas inlet, and a flue gas outlet, the enclosure having an exterior wall exposed to ambient air and an interior wall, the parallel walls forming an exhaust enclosure having top and bottom openings wherein the ends have peripheral flanges parallel to and engaging the interior and exterior walls defining joints therebetween, and thereby defining a chimney and, coating the surfaces of the chimney and sealing said joints with heat resistant anti-oxidant material having a co-efficient of thermal expansion not substantially greater than the co-efficient of thermal expansion of the enclosure.