US3583689A - Segmental chain hangers - Google Patents

Abstract

The present invention concerns an improved and novel chain hanger element of the type used to support heat transfer chains within a rotary kiln. The hanger elements are emplaced adjacent one to another on the inside surface of a rotary kiln to support a plurality of heat transfer chains. These chains are hung within the kiln to assist in heat transfer between a hot gas stream and a solid material stream moving through the kiln, by continually passing successively through the hot gas and solid material streams as the kiln rotates. In accordance with the invention, the facing surfaces of adjacent chain hanger elements form an acute angle to the direction of thermal expansion/contraction and are substantially parallel one to the other. Accordingly, the space between adjacent elements available for thermal expansion is greater than the perpendicular distance between adjacent surfaces within which chain links tend to wedge.

Description

United States Patent 72] Inventor Henry Gildener Teaneck, NJ.

[21] Appl. No. 856,127

(22] Filed Sept. 8, 1969 [45} Patented June 8, 1971 [73] Assignee Pullman Incorporated Chicago, Ill.

[54] SEGMENTAL CHAIN HANGERS Primary Examiner-John J. Camby AttorneysJohn C. Quinlan and Margaretta LeMaire ABSTRACT: The present invention concerns an improved and novel chain hanger element of the type used to support heat transfer chains within a rotary kiln. The hanger elements are emplaced adjacent one to another on the inside surface of a rotary kiln to support a plurality of heat transfer chains. These chains are hung within the kiln to assist in heat transfer between a hot gas stream and a solid material stream moving through the kiln, by continually passing successively through the hot gas and solid material streams as the kiln rotates. In accordance with the invention, the facing surfaces of adjacent chain hanger elements form an acute angle to the direction of thermal expansion/contraction and are substantially parallel one to the other. Accordingly, the space between adjacent elements available for thermal expansion is greater than the perpendicular distance between adjacent surfaces within which chain links tend to wedge.

PATENTEI] JUN 8 IHYI 3,5 3; 9

sum 1 or 2 HENRY GILDENER INVI'JNIOIC.

HY $0M C ATTORNEY SEGMENTAL CHAIN HANGERS BACKGROUND OF THE INVENTION Rotary kilns have been in use for a number of years to heat or otherwise process minerals and ores in the manufacture of various end products such as cement, lightweight aggregate, alumina. magnesia and lime. Typically, the raw material is charged, either in a dry form or as a slurry, into the higher end of a refractory lined, cylindrical kiln which is slightly inclined from the horizontal to aid in the movement of the processing material. A hot, gaseous stream is passed through the kiln, countercurrent to the flow of the material to be heated. The source of the hot gas is usually one or more burners, located at the discharge end of the kiln. The kiln is rotated slowly to obtain the required contact between the gas and the processing material and thereby effect the necessary heat and mass transfer.

It is frequent practice in the design of such kilns to employ chains as auxiliary heat transfer devices. The chains are connected to hangers which are welded to the inside surface of the kiln shell in parallel ring patterns, continuous helix patterns or combinations of both, depending on the particular service of the kiln. The chains aid to transfer heat from the gas stream to the processing material in the following manner. The raw material is charged at a rate sufficient to fill only a part of the kiln, the remainder of which is occupied by the countercurrently flowing, hot gases. As the kiln rotates, individual chains are alternately first exposed to the hot gas stream and then submerged into the relatively cool process material, thereby transferring heat from the hot gas stream to the process material. Accordingly, by reason of the heat transfer process described above, the chains, as well as the chain hangers, undergo a cyclic temperature change and thermal expansion as a result of being heated in the gas stream and cooled in the process material with each revolution of the kiln. Superimposed upon this cyclic thermal expansion are incidental, nonperiodic thermal expansions caused by variances in the flow rates through the kiln, startup and shutdown and other process discontinuities.

The fact that the chain hangers will be subjected to the aforementioned thermal expansion is of major consideration in the design of chains and chain supports. Various methods have been used to support the chains. Chain hangers have been designed to consist of one or several long, continuous metal bands welded to the inside surface of the kiln and provided with holes or half-ring supports to which the chains are connected by means of shackles. This design has proven unsatisfactory because the metal bands tend to buckle upon thermal expansion. Further, while the bank is exposed to the hot gases and materials and thus goes through cyclic expansion, the kiln surface to which the band is welded (either directly, or to anchors which are in turn welded to the kiln surface) is insulated from these cyclic temperature changes by means of the refractory lining. Therefore, when the cyclic temperature changes are imposed upon the system and the bands start to expand, a relative motion is created between the band and the kiln surface causing welds to fail. To alleviate this problem, current practice is to provide short lengths of segmental hangers, each supporting only a small number of chains. These segmental hangers are welded to the surface of the kiln and spaced apart so as to provide room between adjacent hangers for thermal expansion.

The need to provide room for thermal expansion between adjacent hangers has introduced a second major problem in the design of chain systems. Because of the constant motion of the chains as they collapse and suspend during rotation of the kiln, there is a tendency for chains to become wedged within the room so provided between adjacent hangers. When wedging occurs, the effectiveness of the chain as a heat transfer means is greatly reduced. Further, a chain so wedged tends to ensnarl other chains. Since these chains can be as long as to feet and weigh from 60 to 200 pounds each and further, since they are coated with the processing material which frequently is of substantial weight, the stresses exerted on a hanger supporting an ensnarled network of chains is frequently enough to cause the hangers to fail.

Accordingly, in the design of such chain systems both the length of each segmental hanger and the space between adjacent hangers are carefully controlled so that adjacent hangers are close enough together to preclude the possibility of a chain link wedging between them and yet far enough apart to provide room for thermal expansion. A space between adjacent hangers of about three-eighths to five-eights of an inch is common, depending upon the magnitude of the expected expansion and the size ofa chain link,

Because of the narrow tolerance set by the two limiting criteria of a maximum gap to preclude chain wedging and a minimum space to allow for thermal expansion, extreme care must be taken to remain within these limits when welding the hangers in place. The conventional practice for installing the hangers is as follows. First, guide lines are inscribed on the inside kiln shell surface, conforming to the desired path of hanger emplacement. Each hanger is then carefully centered upon the proper guide line and a special jig, fixture or occasionally, an assistant welder, is employed to steady the hanger in its aligned position, as it is welded to the kiln shell. The next hanger is then aligned and held in place, a spacer usually being placed between adjacent hangers to insure that the space is provided. Any substantial error in the size of this space will cause either excessive stress due to thermal expansion (when the space is too small) or wedging of chains between hangers (when the space is too large).

The necessity of such extreme care in aligning and welding the hangers results in high installation costs. A fairly large kiln may require as many as I000 to 1200 of such chain hangers and, because of the delicate task of aligning and spacing, a minimum of one-half a manhour may be required to weld each hanger in place.

Further, because of the abrasive quality of the processing material and because of the constant motion of the chains as they collapse and suspend, the gap left between hangers for thermal expansion tends to wear wider and wider and the chain links tend to wear thinner and thinner. Ultimately, the aforementioned precautions notwithstanding, the gap is wide enough and the links are thin enough to allow chains to wedge between hangers.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved and novel chain hanger, which is one of a series of other hangers to be emplaced along a path, and which will undergo expansion at least in the direction of that path, as for example, the aforementioned chain hanger system. When such elements are so emplaced, a space, somewhat greater than the expected expansion must be provided between adjacent surfaces of adjacent elements which would otherwise tend to contact each other upon expansion. These adjacent surfaces will hereinafter be referred to as leading surfaces." It has been discovered that by a novel design of the leading surfaces, the required space for expansion may be provided for without leaving the heretofore required large gap between these surfaces. Gap" as used hereinafter refers to the shortest distance between two leading surfaces. This surprising and novel coexistence of a relatively large space and a relatively small gap is accomplished by having the leading surfaces form an oblique angle to the path of expansion and be substantially parallel with the adjacent leading surface.

Another object of the present invention is to provide a novel and improved segmental element suitable for use as a support and as part of a series of other elements emplaced along a path in close proximity to one another, all of which will undergo expansion at least in the direction of that path.

An additional object is to embody the foregoing objects into a segmental chain hanger to be welded, in series with and in close proximity to other elements, along a path, to the inside surface of a rotary kiln and to be used as a support for heat transfer chains. By means of the novel orientation described above, the allowable tolerance for this alignment of a hanger during installation will be increased. This surprising result will be more clearly described and illustrated below.

A still additional object is to embody all of the foregoing advantages into the design of a segmental chain hanger which can be installed without need of a fixture, jig or other external steadying means. This is accomplished by providing stiffeners, arranged transverse to the plane of the hanger so as to form a cross-shaped bottom and thus, allow the hanger to stand in place on said bottom as it is welded. A further advantage of such an embodiment is that the stiffeners provide additional surface area and thereby additional anchorage for the refractory lining of the kiln. A still further advantage of the stiffeners is that the weld applied to such a hanger may be concentrated around the center of the cross-shaped bottom, lessening the danger of weld cracking due to differential expansion between the shell and the hanger, while providing concurrently additional welding surface.

Another object of the invention is to provide cutouts in the hanger-plate which offset the weight added by the stiffeners and provide additional anchorage between the hanger and the refractory lining of the kiln.

Other objects and advantages of the present invention will be apparent to those skilled in the art from the following description and drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, is a longitudinal, sectional view of a part of an exemplary kiln illustrating, schematically, a possible arrangement of chain hangers.

FIG. 2 is a transverse section of the kiln shown in FIG. 1.

FIG. 3 is a sectional view of an exemplary chain hanger embodying the principles of the present invention, taken on line 3-3 of FIG. 4.

FIG. d is an isometric view of the exemplary chain hanger shown in FIG. 3.

FIG. is a sectional view of the hanger shown in FIG. 4 along line 5-5 of said figure.

FIG. 6 is a cross-sectional view of the hanger shown in FIG. 4 as viewed from line 66.

FIG. 7 is an enlarged schematic view of parts of two adjacent hangers embodying an aspect of the subject invention as superimposed upon corresponding parts of adjacent conventional hangers, shown in broken lines.

FIGS. 8a and 8b are schematic illustrations of the advantages enjoyed by employing the instant invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. II, the exemplary kiln 10 shown may be as large as about 400 to about 700 feet in length and about 16 to about feet in diameter. Helical chain hanger rows 11 are illustrated. It is to be understood that helical rows represent only one of several satisfactory configurations and that the embodiment of the subject invention would be equally useful if the hangers were arranged otherwise, as for example, in circular rows. For clarity, the chains themselves are omitted from FIG. ll.

Each hanger is welded to the shell 12 of the kiln 10. Subsequent to welding the hangers in place, the kiln is frequently lined with either castible refractory, cement, or some other suitable lining 13.

FIG. 2 illustrates one method of suspending chains from the hangers. As shown, the chains 14 are attached at both ends to the hangers 19 so that when the kiln is in any one position, approximately half the chains 14 are suspended. The remaining chains 26 are collapsed against the lower portion of the kiln. In operation, collapsed chains are covered with the processing material while the suspended chains are exposed to the hot gas stream passing through the kiln.

It will be obvious to one skilled in the art that while chains fixed at both ends to hangers are used as an example, the novel features of the present invention are equally applicable to both large and small kilns and other similar equipment wherein chains are affixed to hangers in a different manner, as for example curtain chains which are attached at one end only. It will further be apparent that the present invention is applicable to any equipment wherein chain hanger elements must be aligned within a given space in a manner to allow for expansion and contraction.

In accordance with the stated objectives, it is a purpose of the present invention to allow use of a relatively smaller gap between adjacent hangers and still provide for thermal expansion. Stated another way, the useful life of a given hanger will be increased by using a smaller gap; a smaller gap means that more wear can be tolerated before a chain can become wedged.

The invention will also decrease installation costs. As shown above, the gap must be small enough to prevent wedging of the chains and the space must be large enough to allow for thermal expansion. In a conventional hanger, the difference between the two criteria represents the allowable error in alignment. A hanger designed in accordance with this invention will increase this allowable error. By increasing the allowable error in alignment, easier and faster installation and reduced labor costs are obtained.

To achieve the above-stated objectives as well as other advantages which will become apparent from the following description, a preferred configuration of a chain hanger I5 is illustrated in FIGS. 3-7. The hanger 15, illustrated in plan view by FIG. 3, in isometric view by FIG. 4 and in cross section by FIGS. 5 and 6, is a flat, steel plate capable of supporting four chains. It is to be understood that the configuration illustrated is merely exemplary and one skilled in the art can easily apply the concepts to many other hanger configurations supporting any number of chains.

Referring to FIGS. 3 and 4, the hanger 15 having plate surfaces 2ll and a relatively long front edge 23, is welded to the inside surface of the kiln shell 12 along relatively short back edge 24. Holes 17 are provided to support the chains. The leading surfaces 20 are transverse to the path of major thermal expansion. As best viewed in FIG. 3, the two leading surfaces 20 are deflected so as to be at an oblique angle with the path of expansion and parallel to each other.

It is to be understood that a concept of the invention is to have the leading surface form an oblique angle with the path of expansion and be parallel to adjacent leading surface of an adjacent element. Accordingly, deflection of the surfaces in the manner described above is merely an exemplary configuration. The desired orientation may also be accomplished, for example, by beveling the leading surfaces of a platelike hanger so that an oblique angle is formed between the leading surface and the path of expansion. The bevel must be such that adjacent leading surfaces are substantially parallel to each other.

The significance of the above-described relationship (the orientation of the leading surfaces to the path of expansion) to the stated objects of the invention are best shown in FIG. 7. This figure depicts an enlarged, plan view of the leading surfaces 20 of two adjacent preferred hangers 15 designed in accordance with the invention. This preferred configuration is superimposed upon a similar view of two adjacent conventional hangers 16, illustrated with broken lines. The conventional hangers are positioned so as to provide a space for thermal expansion, shown as dimension A in FIG. 7. In the conventional design, the leading surfaces are perpendicular to the path of expansion and the space provided for expansion is equal to the gap (perpendicular distance) between adjacent leading surfaces. In contrast, the preferred configuration of the invention provides leading surfaces at an acute angle G to the path of expansion, and the gap, dimension B, within which a chain 18 must fit to be wedged, is significantly smaller than the space, dimension A, provided for expansion. In fact, the gap B is equal to the space A provided for expansion multiplied by the sine of the acute angle G formed between the leading surface and the path of expansion. Therefore, in accordance with the stated object of the invention, the preferred hanger, and any hanger designed in accordance with the invention, provides a gap smaller than the corresponding space for thermal expansion, whereas in conventional hanger designs the space and the gap are always substantially identical.

To further illustrate this feature of the invention the following geometrical and quantitative analysis is given. Referring to FIG. 7, if the dimension A is the minimum space required to allow for thermal expansion, it is clear that the size of the gap in the conventional configuration must likewise be equal to A. However, in the preferred configuration shown in FIG. 7, to provide a space for thermal expansion equal to A, a gap B, equal to A times the sine of the angle G, is required. Since the sine of an angle less than 90 is always less than one, when G is an acute angle the gap B will always be less than the space A. For example, if the minimum space A is three-eighths of an inch and the angle G is 30, the sine of 30 is 0.5 and the gap B is 0.5 times three-eighths of an inch, i.e., three-sixteenths of an inch.

The novel orientation of the leading surfaces results in another important advantage. As described above, two criteria limit the juxtapositioning of adjacent hangers; a maximum gap determined by the dimension needed to preclude chain wedging and a minimum space determined by room needed for expansion. For the conventional hanger the difference between the maximum and minimum represents the allowable tolerance in misalignment. FIGS. 80 and 8b of the drawings illustrate schematically how one aspect of this invention increases this allowable tolerance. Depicted in FIG. 8a are adjacent leading surfaces 42, 44, oriented in the conventional manner. The left-hand leading surface 44 (as viewed in the drawing) is shown positioned at the two extreme locations dictated by the two criteria of thermal expansion and chain wedging. That is to say, dimension C represents the minimum space required for thermal expansion and dimension D represents maximum gap allowable to preclude chain wedging. Dimension E, then represents the allowable error in alignment for conventional hangers.

The FIG. 8 b depicts adjacent leading surface 46, 48 of a hanger designed in accordance with the invention, drawn to the same scale as FIG. 8a. The same quantitative criteria of maximum gap and minimum space, dimensions D and C respectively, are applied. As FIGS. 80 and 8b graphically illustrate, the invention results in a considerably greater allowable error in alignment, shown as E in FIG. 8b. To more clearly illustrate this advantage a geometrical and quantitative analysis may be applied as follows. Referring again to FIGS. 8a and 8b, the geometry of the preferred configuration is such that the tolerance is equal to D, divided by the sine of the single G, less C. When, therefore, G is less than 90, the tolerance for the preferred configuration will always be greater than D minus C, the tolerance for the conventional configuration. For example, if D equals five-eighths of an inch and C equals foureighths of an inch, the tolerance for aligning conventional hangers is only one-eighth of an inch. For the preferred configuration, however, if the angle G is for instance 30, the other dimensions remaining as above, the tolerance is now sixeighths of an inch, six times as large.

Other aspects of the invention have been incorporated into the preferred configuration of the chain hanger illustrated in FIGS. 36, which further reduce installation costs. As best viewed in FIGS. 4, 5 and 6, stiffeners 33 are provided, transverse to the plane of the hanger. As illustrated in FIG. 5, these stiffeners, in addition to adding strength to the hanger, form a cross-shaped bottom. Thus, when installing a hanger with the preferred configuration, the need of a jig or fixture to support the hanger is obviated; the hanger is capable of standing in place as it is welded.

Another advantage of the stiffeners is that a length of weld greater than that applied to conventional hangers of equivalent size may be used In the preferred configuration,

such welding being concentrated, however, at the cross junction. Thus, the weld is confined within a considerably shorter length of the kiln shell relative to the direction of maximum thermal expansion. As so applied, the weld will be less vulnerable to the stresses caused by differential expansion of the shell relative to the hanger.

By providing cutouts 34 and 35, the weight added by the stiffeners is compensated for and the total weight of the hanger may be substantially unchanged despite the addition of stiffeners. The cutouts also serve to alleviate a problem peculiar to refractory lined kilns. The lining of such kilns tends to separate from the inside kiln surface and thereby expose this surface to the high temperatures which exist within the kiln, causing local "hot spots." To prevent this, the current practice is to weld steel clips to the kiln shell to provide anchorage for the refractory. The cutouts, and to a certain extent, the stiffeners, have the additional advantage of providing highly effective anchorage for the castable refractory lining and, thereby reduce the number of steel clips otherwise required.

Chain hangers embodying the present invention may be formed from a wide variety of steels, such as alloy steels, stainless, various types of carbon steel and substantially any other type of steel, the choice of which will depend upon the service for which they are employed. To resist wear, the hangers are preferably case hardened or otherwise treated so as to render them resistant to wear. The hangers may be formed from the well-known process of sand casting and hangers designed in accordance with the present invention may be manufactured by this process without difficulty.

It will be apparent that many specific configurations of hanger elements other than the foregoing specific examples are within the scope of the invention.

lclaim:

I. In a chain hanger having'leading surfaces at the ends thereof and adapted to support chains in a rotary kiln .in which kiln a plurality of said hangers are emplaced in end-to-end relationship with respect to each other and subject to end-toend thermal expansion, the improvement which comprises:

each of the leading surfaces of said hanger being disposed substantially parallel and juxtaposed to the adjacent leading surface of the chain hanger next in line on the path of emplacement, and

each of the leading surfaces being disposed at an oblique angle with respect to the path of expansion.

2. A chain hanger for emplacement on the inside of a metal vessel wall, which comprises:

a metal plate having plate surfaces, a relatively long front edge, a relatively short back edge adapted to be attached to the vessel wall, and leading surfaces at its sides adjoining the front edge, each leading surface disposed at an oblique angle with respect to a plate surface, and

means disposed adjacent to the front edge of the plate for support of chains.

3. The chain hanger of claim 2, wherein a leading surface is provided by an oblique deflection of a side portion of the plate relative to the surface of said plate.

4. A chain hanger according to claim 2, in which a stiffener is provided having at least two sides, one side of which being rigidly attached to one of the plate surfaces and another one extending transversely with respect to said plate surface in conformance with the shape of the vessel wall.

5. The chain hanger of claim 2 provided with cutout portions whereby a substantial reduction in weight is effected.

Claims (5)

1. In a chain hanger having leading surfaces at the ends thereof and adapted to support chains in a rotary kiln in which kiln a plurality of said hangers are emplaced in end-to-end relationship with respect to each other and subject to end-to-end thermal expansion, the improvement which comprises: each of the leading surfaces of said hanger being disposed substantially parallel and juxtaposed to the adjacent leading surface of the chain hanger next in line on the path of emplacement, and each of the leading surfaces being disposed at an oblique angle with respect to the path of expansion.

2. A chain hanger for emplacement on the inside of a metal vessel wall, which comprises: a metal plate having plate surfaces, a relatively long front edge, a relatively short back edge adapted to be attached to the vessel wall, and leading surfaces at its sides adjoining the front edge, each leading surface disposed at an oblique angle with respect to a plate surface, and means disposed adjacent to the front edge of the plate for support of chains.

3. The chain hanger of claim 2, wherein a leading surface is provided by an oblique deflection of a side portion of the plate relative to the surface of said plate.

4. A chain hanger according to claim 2, in which a stiffener is provided having at least two sides, one side of which being rigidly attached to one of the plate surfaces and another one extending transversely with respect to said plate surface in conformance with the shape of the vessel wall.

5. The chain hanger of claim 2 provided with cutout portions whereby a substantial reduction in weight is effected.

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