US3730073A

US3730073A - Chimneys

Info

Publication number: US3730073A
Application number: US00168885A
Authority: US
Inventors: P Potter
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-08-04
Filing date: 1971-08-04
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01

Abstract

A chimney comprising a corrugated outer shell, an inner shell incorporating a section having corrugations at desired spacings so as to compensate for any unequal expansion between the outer shell and the inner shell, and fiber-glass or other suitable heat insulation medium packed into the space between such shells, of which the following is a specification.

Description

G Miiitefil tiates Patent 1 i 1 Potter May 3, i973 1 CHIMNEYS 2,526,097 10/1950 Sveinson ..98/46 n l,6l5,9()9 2/1927 Nance ..l26/307 Invent Paar'ck 25 ommwmd 2.102.727 12/1937 Maher .237/55 Avenue, Hamilton, New Zealand [22] Filed: Aug. 4, 197i Primary Examiner-William F. ODea Assistant Examiner-Peter D. Ferguson [211 App! 168385 Almrney lrvin Thompson and Robert Patch [52] US. CL. .98/60, 110/184, LIX/I49 [57] ABSTRACT [51] lnt.Cl. ..E04h 112/28 A Chimney Comprising a Corrugated Outer Sm" an {58] Field of Search ..98/586(),45,46; 126/307; I 1

l w 49 inner shell incorporating a section having corrugations 237/55 110/ l at desired spacings so as to compensate for any unequal expansion between the outer shell and the Referenms Cited inner shell, and fiber-glass or other suitable heat insu- UNTED STATES PATENTS lution medium packed into the space between such shells, of which the following is a specification. 36%](19 8/[887 Dewey 126/307 R UX 11 Claims, 4 Drawing Figures Patented May 1, 1973 3,730,073

3 Sheets-Sheet l FIGJ.

Patonted May 1, 1973 s sheets-sheet 2 FIG.2.

Patented May '1, 1973 3 Sheets-Sheet 5 FIG 3 cniMNEYs This invention relates to improvements in chimneys.

A problem especially associated with chimneys of plants burning high sulphur-content fuels is that of corrosion and smut emission. When the fuel is burnt, the sulphur content forms oxides which will condense at temperatures normally ranging from 240-280F. to form sulphuric acid on the cooler surfaces of chimneys passing exhaust gas to atmosphere. Acid condensate deposited in this manner is the cause of the extensive corrosion found in the higher sections of steel chimneys. In addition, smuts will be formed by a build-up of minute particles of carbon on this layer of sulphuric acid and will lift off to enter the gas stream to discharge to atmosphere. Such smuts will create a nuisance to the locality by settling on the surfaces of buildings, paintwork, motorcars, etc., where they will cause staining and acid attack.

To prevent corrosion and to obviate the formation of acid smuts, it is necessary to maintain the inner surface of the chimney at temperatures above the acid dewpoint of the exhaust gases and to discharge the gases to atmosphere at the highest possible efflux velocity in order to obtain good conditions for dispersal With the advent of the high efficiency boiler discharging exhaust gases at temperatures as low as lF. above the steam temperature, the problems of corrosion and smutting have become more difficult to control. Moreover, as the head on a boiler is reduced below its designed maximum, then the exhaust gas temperatures are correspondingly lowered and the problems of corrosion and smutting will become more acute. By cladding the exterior of the chimney with an aluminum liner to form an insulating air gap of some inch wide, control of corrosion and smutting has been possible for modern boilers with loads of 75 percent of the related maximum output. At boiler loads below 75 percent of the rated maximum output, a modern high efficiency boiler will produce acid condensation in an aluminum-clad stack with the resulting detrimental effects of corrosion and smutting. It has, therefore, become increasingly obvious that a more efficient form of insulated chimney must be provided if a better control of exhaust gas temperatures is to be achieved. In this respect, observations of chimneys insulated with a layer of rockwool up to 2 inches thick has shown that positive control of corrosion and smut emission can be achieved with boiler loads below 50 percent of the rated maximum output, and that an insulated chimney is far superior to a chimney clad in aluminum with an air gap only.

The object of the present invention is to provide a chimney having such a construction and or arrangement of its parts that in use it will practically overcome the adverse conditions created by low temperature acid condensation in a high efficiency boiler.

Generally the invention consists of a chimney comprising a corrugated outer shell, an inner shell incorporating a corrugated section at'desired spacings so as to compensate for any unequal expansion between the outer shell and the inner shell, and fiber-glass or other suitable heat insulation medium packed into the space between such shells.

In further describing the invention, reference will be made hereinafter to the accompanying diagrammatic drawings, in which:

FIG. 1 is a longitudinal sectional view of the chimney shown broken in its height.

FIG. 2 is a cross-section of part of the chimney showing a typical joint between sections of the chimney length,

FIG. 3 is a similar view to FIG. 2 but showing a modified section designed as a free-standing chimney, and

FIG. 4 is a cross-section taken on the line 4-4 of- FIG. 3 on a reduced scale.

In giving effect to a preferred embodiment of the invention, the outer shell 10 of the chimney is corrugated by horizontal rolls 11 and formed out of sheet stainless steel, such as 166 type 304. Dependent upon the size of the chimney, the outer shell 10 can be built up by 4 foot standard lengths fully welded at length joints.

The inner shell 12 of the chimney consists of sections 13 constructed in molybdenum austenitic sheet stainless steel, such as 20G. Type 316. This inner shell is fabricated to form a one-piece gas-proof structure incorporating peripheral swages 20 at desired intervals, such as every 2 ft, to compensate for the unequal expansion between the outer shell 10 and the inner shell. The inner shell 12 is affixed to the corrugated outer shell 10 by a lower outwardly-flanged end 15 being tack-welded to brackets on the inner face of the outer shell, whilst the upper end of each section 13 is located inside the lower end of an upper inner shell section and fully-welded.

AS already mentioned the space between the outer shell 10 and the inner shell 12 is packed with fiberglass 16.

The chimney further includes a vortex or venturi top unit 17 also embodying partially corrugated outer and inner shells 18 and 19 formed of the same steels as earlier described. The inner shell 19 of this top is formed with one or more peripheral swages 20 for strength. The lower end of the shells 18 and 19 of the top 17 are arranged to co-incide with the top end of the constituted chimney stack of the outer and

inner shells

10 and 12, and secured thereto through an angle 21 welded to the outer surface of the inner shell 12 and jointing the outer shell 10 and top outer shell 18. Angles 22 also rigidly connect the upper end of the shells 18 and 19 of the top unit 17, and which angles 22 have brackets with holes 23 for affixing a cord spark arrestor or other conventional unit (not shown). The space between the shells l8 and 19 of the top unit 17 is also packed with fiberglass 14.

In a modification, as shown in FIGS. 3 and 4, vertical stiffeners 25 are incorporated in the space between outer and

inner shells

10 and 12 of the chimney stack. The number and size of the stiffeners 25 are dependent upon the height and siting of the chimney. Each stiffener consists of a suitable length of channel section steel positioned with one of its webs welded to the outer shell 10 and its lower end welded to a bottom plate 26 and outer angle 27 or angles welded to such plate and such shell. This angle 27 has holes drilled for securing by bolts 28 to a similar upper end of an upper section of the stack and through an asbestos ring 24.

With this chimney in operational use it will overcome the adverse conditions created by low temperature acid condensation in a modern high efficiency boiler. It has many advantages over a conventional chimney. Not only does this improved chimney incorporate the principle of insulation, but it also employs its own particular form of construction in materials more resistant to acid attack. The structural strength of the chimney is economically obtained by corrugating the outer shell in stainless steel to produce a strong light-weight section, self-supporting to the extended heights recommended by the Clean Air Act and impervious to atmospheric attack. The inner shell 12 is made up of stainless steel sections 13 with a very high elevated creep strength of any standard stainless steel available and has an improved corrosion resistance to acid attack.

The fiberglass packing l4 and 16 between the respective shells provides overall thermal conductivity approximately to 0.17 B.T.U.s. per sq. ft. per hour per F. Comparative thermal efficiencies for a bare metal chimney and for an aluminum clad chimney would be about 1.08 and 0.66. The special venturi or vortex top 17 of the chimney obtains the high velocities for efflux for good dispersal.

in comparison with the convention chimney, this improved chimney will control corrosion and smut emission as well as increase efflux velocities. The insulating properties will be about 6.5 times greater than a bare chimney and about 4 times greater than an aluminumclad chimney. it is maintenance free, both inside and outside. The chimneys lightweight form of construction allows it to be easily handled. With its structural strength being on the exterior of the chimney, it is less liable to damage during erection and service and will retain constantly its appearance. For the same height, its initial cost will be double that of a conventional chimney but its maintenance free life will be extended to the life of the plant it services.

What is claimed is:

1. An insulated chimney comprising a thin outer shell, said thin outer shell having corrugations therein to increase the structural modulus of section of a thin shell by maintaining the section round in the plane of bending, a thin gauge inner liner formed with corrugations at predetermined spacings sufficient to compensate for the differential expansion between the cool structural outer shell and the hot inner liner, and insulating material disposed between said outer shell and said inner liner.

2. A chimney as claimed in claim 1 wherein the outer shell is corrugated by horizontal rolls.

3. A chimney as claimed in claim 1 and wherein the inner shell consists of at least one section fabricated to form a one-piece gas-proof shell incorporating peripherally extending swages at desired intervals.

4. A chimney as claimed in claim 3 and wherein the inner shell is affixed to the corrugated outer shell by a lower outwardly flanged end welded to brackets on the inner face of the outer shell whilst the upper end of each inner section is located inside the lower end of an upper inner shell section and welded thereto.

5. A chimney as claimed in claim 1 and further including a vortex or venturi top unit also embodying outer and inner shells, and fiberglass or other suitable insulation medium packed mto the spaces between such shells.

6. A chimney as claimed in claim 5 and wherein the inner shell of the top unit is formed with one or more peripherally extending swages.

7. A chimney as claimed in claim 5 and wherein the lower end of the shells of the top unit are arranged to co-incide with the top end of the constituted chimney stack and secured thereto by angles welded to the outer surface of the inner shell and jointing the said outer shell and the top outer shell.

8. A chimney as claimed in claim 7 and wherein angles alsorigidly connect the upper end of the shells of the top unit and have brackets with holes for affixing a cord spark arrester.

9. A chimney as claimed in claim 1 and wherein vertical stiffeners are positioned in the space between outer and inner shells of the chimney stack.

10. A chimney as claimed in claim 9 wherein the stiffeners are welded to the outer shell and to steel rings, at the end of each liner section, the rings being welded to both rings and to an external angle or angles.

11. An insulated upright elongated chimney, comprising a thin metal outer shell, said outer shell having horizontal corrugations therein that are rounded in the plane of bending, a thin gauge metal inner liner disposed within said outer shell, said liner having horizontal corrugations therein spaced apart by portions of the liner that are straight in an upright direction, and insulating material packed between said outer shell and said inner liner.

Claims

5. A chimney as claimed in claim 1 and further including a vortex or venturi top unit also embodying outer and inner shells, and fiberglass or other suitable insulation medium packed into the spaces between such shells.

8. A chimney as claimed in claim 7 and wherein angles also rigidly connect the upper end of the shells of the top unit and have brackets with holes for affixing a cord spark arrester.