US2534747A - Open-hearth door construction - Google Patents

Description

H. w. WILSON ETAL 2,534,747

OPEN-HEARTH DOOR cousmucuou Filed June 12, 1946 2 Sheets-Sheet 1 2M 97 INVENTORS HERMAN 14/ ML so/v AML'S E HEYWORTH A 7" TORNEY Dec, 19, 1950 H. w. WILSON EI'AL OPEN-HEARTH DOOR cousmuc'rxon 2 Sheets-Sheet 2 Filed June 12. 1946 & ATTORAZEY Patented Dec. 19, 1950 I OPEN -HEARTH DOOR CONSTRUCTION Herman W. Wilson and James E. Heyworth, Cleveland, Ohio, assignors to Republic Steel Corporation, Cleveland, Ohio, a corporation of New Jersey Application June 12, 1946, Serial No. 676,261

This invention relates -to furnace doors, especially closures for furnaces of the types used in the manufacture or alloying of steel and other metals. In an important specific as ect the invention is designed to provide an improved and long-lived door construction for open hearth furnaces.

Because of the excessive heat and other unusually severe conditions encountered in steel furnaces of the open hearth type, difilc lty has arisen in providing doors that will not break down frequently. Charging doors have been proposed or made with various arrangements of water containers, sometimes in combination with a lining of refractory brick or the like, but structural failures have been frequent, necessitating constant servicing and often entire replacement of the door after only a short period of use. Both the high temperatures and the extraordinary expansions and contractions arising between successive heats of the furnace tend to warp the door or to break its water connections or to open seams in the water tank or tanks, especially at corner welds. Furthermore, even though the door is lined with. refractory material, conditions are such that the refractory breaks or spalls, and falls out, or often actually melts out. In consequence, it has been found that doors of the described type will usually not last for more than to heats and then they must be removed and relined and have any leaks welded. As a result, considerable delay is caused in furnace operations, or if attempt is made to repair the door. while the furnace is functioning, the physical hazard to the workmen is considerable, in view of the tremendous heat.

Still further difficulty has been encountered in the circulation of water through tanks or cooling systems of the prior types of door, in that sediment tends to collect in the bottom, impairing or nullifying the cooling effect so as to result in burn-throughs, and similar consequences occur because of air or other gas released by the water and collecting at the head of the tank, sometimes forming an air lock that impedes circulation and, in any case, resulting in overheating in localities where the water is displaced by air or gas.

Thu an important object of the invention is to provide a furnace door of the liquid-cooled 2 Claims. (01. 122 -49s) be suflicient to melt such material.

type which will stand up longer in operation and which at the same time is of relatively simple construction. Further objects are. to provide a door structure for open hearth furnaces and the like wherein positive and vigorous circulation of water is assured practically throughout the area of the door, wherein collection of sediment or of quantities of gas or air is minimized, and wherein various cooperating element may be individually replaced without materially impairing the structural integrity of the remainder of the door. Another object is to provide a furnace door of the stated character, including novel and improved means for keeping a refractory material in place or at least in protective relation to cooling conduits, even though the temperature may A still further object is to provide a door of the stated kind, wherein severe expansion and contraction of metal parts may take place without appreciable tendency to open seams or crack or warp the structural elements, a special object being to provide a door construction free of corner welds or like seams.

To these and other ends, including objects hereinafter apparent or otherwise incidental to the practice of the invention, and particularly including the provision of a' doorstructure that may be used for a great number of successive furnace heats without need of repair or replacement, a particularly advantageous embodiment of the invention is described herein and shown in the accompanying drawings, by way of illustrative example. It is believed that the principles of the invention will thus be made clear and the susceptibility of the device to modification in various respects will likewise become apparent to those skilled in the art.

Referring to the drawings:

Figure 1 is an elevational view of the door,-seen from its inside face, with certain portions invertical section;

Fig. 2 is a section on line 2-2 of Fig. 1 but with the refractory material omitted for the sake of clarity;

Fig. 3 is an enlarged plan view, i. e., of the top of the door;

Fig. 4 is an enlarged end elevation as seen from the left hand side of Fig. 1;

Fig. 5 is an enlarged section on line 5--5 of Fig. 1; and

Fig. 6 is an enlarged end elevation at the right hand side of Fig. l.

The specific device shown in the drawings is intended as a charging door for an open hearth furnace and is mounted to be raised vertically on the front of the furnace, as by means of the supporting plates 20, 2|, 22, having holes to receive suitable studs and linkage connected to suitable counterweights above the furnace opening, by which the door 'is supported. It will be understood that the furnace and the door supporting and operating mechanisms may be of known, conventional type, and are therefore not illustrated.

The door itself comprises a generally rectangular line of pipe designated 24, constituting the periphery of the structure, and a sinuous line of pipe generally designated 25, that distributively fills the space within the rectangle and includes a vertical array of horizontal pipe sections generally designated 21, spaced from each other and connected at alternate ends. In the device shown, the outer or peripheral line of pipe comprises four straight sections 28, 29, 30, 3|, joined at their ends by 90 Ls of pipe butt-welded-to the straight sections as shown. Thus a curved L 33 joins the top section 3| and side section 28; a similar curved L 34 joins the side section 23 and bottom section 29, but in this instance has a sidewise-opening port or coupling portion formed or welded therein at 35, the-opening being normally closed by screw plug 36, which is adapted to be removed for draining and cleaning the cooling system. Similarly, sections 29 and 30 are joined by a curved L 31, and sections 30 and 3| by a similar L 38, which is formed or otherwise designed to constitute a T element, providing an opening or pipe coupling extension 40 directed outwardly of the front of the door.

- The straight sections 21 of the sinuous line of pipe within the out r rectangle are preferably flattened vertically throughout nearly all of their length, as shown in Figs. 1 and 5, so as to have a horizontal dimension substantially larger than the vertical dimension. The ends of the sections can be round, however, so as to be joined by U-shaped coupling elements, or curved 180v Ls 42. Although the number of straight sections 21, i. e., the number of horizontal passages in the sinuous line, may vary with the size and other requirements of the particular door, there ordinarily should be at least several, and preferably a multiplicity of such sections, for example seven as shown in the drawings. The uppermost section 21a is welded at one end to a 90 L, turned upward, which in turn is welded to a coupling length of pipe 44. The pipe section 44 extends vertically through the upper peripheral pipe section 3|, being of smaller outside diameter than the inside diameter of the section 3! and being welded in watertight relation in appropriate holes bored in the latter. The opposite, round end of the flattened section 21a is welded to a 180 L 42 which in turn is welded to an end of the next lower horizontal section 2121, the latter being at its opposite end joined by a similar L to the succeeding section below, and so on, whereby a continuous passage for coolant is provided back and forth horizontally across the door through the desired multiplicity of conduit elements.

The lowermost horizontal section 21d at its 4 left hand end as seen in Fig. 1 is welded to a elbow 46 turned downwardly, from which the line of pipe continuing the Sil'lllOlls unit extends into the lower peripheral section 29 and then curves around and passes up centrally of the side section 30 and finally curves around in the L 38 into a conforming opening in a baiiie or wall 41 which otherwise blocks the outer pipe structure at the joint between the L 38 and the top section 3|. It will be understood that the vertically extending length of pipe 48 that goes up through the outer section 30 is, like the other parts of the sinuous pipe assembly, of substantially smaller diameter than the line constituted by the members 31, 30 and 38, whereby a passage for coolant is provided around the outside of the section 48 as well as within it. It will also be appreciated that the bends in the section 48 are provided by L's butt-welded to straight lengths or to each other, as in other portions of the pipe structure, although for clarity these welded joints are not specifically indicated in the drawings. The projecting outlet 40, which communicates with the interior of the L 38 but is not directly connected into the section 43, is butt-welded to a sidewise turned 90 L 50, in turn secured to a coupling section 5|.

The outer face of the door comprises a flat plate 53 of generally rectangular configuration conforming with that of the outer pipe assembly 24, welded tangentially to the latter throughout its length. Secured by welding to the inner face of the plate 53 are a multiplicity of shelf-like projecting pieces 54, in turn welded along the underside of their outer edges, to the upper surfaces of the flattened "pipe sections 21. The supporting shelves 54 are advantageously provided in suflicient'number to constitute a secure mounting for the central pipe asseinbly; thus in the illustrated arrangement there are three such shelves regularly spaced along the upper side of each horizontal pipe length 21, except at the central parts of the lowermost sections 210 and 21d, as presently explained.

Charging doors for open hearth furnaces are usually provided with a small aperture, sometimes called a wicket hole, through which the interior of the furnace may be inspected or access may be had for tools or instruments, without opening the door itself. In the present construction, cooling means are provided for such hole, economically in cooperation with the flow of coolant. through the sinuous length of pipe that distributively occupies the major area, of the door. The wicket hole structure comprises concentric hollow cylinders 55 and 56, which may actually be sections of pipe of respectively different diameters, traversing the door on a horizontal axis in the vicinity of the centers of the lower pipe sections 21c and 21d .The outer plate 53 is pierced in conformity with the outermost tubular member 55 and is welded thereto, and the space between the tubular members is closed at each face of the door by an annular plate 5"! welded around its outer and inner circumferences to the inner and outer surfaces of the pipe sections 55 and 55, as shown in Figs. 1 and 5. The ringshaped jacket thus dinning the wicket hole intersects the horizontal pipe sections 210 and 21d, and to efiect such intersection the last-mentioned pipes have a center portion or length cutout of each in conformity with the curved outer wall 55 of the wicket hole jacket. The wall 56 is pierced in conformity and for communication effected in the pipes 21c and 21d, and the joints I at. all places are welded watertight.

Thus the section 21c actually consists of two successive lengths connected in opposite openings near the top of the wicket hole jacket so that v the latter is part of the coolant path of the pipe,

, able to avoid by-passing water flow from the U-bend between pipes 210 and 21d, the described paths are separated by blocking plates 60, 6|,

' disposed in the annular space between members 55 and 56 and extending from the frontto the rear face of the door at a level approximately that of the lower wall of the pipe section 210. The inside surface of the Wicket hole may have the usual tool rest or reinforcing piece, for instance constituted by a 90 segment of a pipe of con forming shape 64, welded on the member 55 as shown.

To promote heat transfer and exchange, and to cooperate in retaining the refractory material in place, the inside of the plate 53 carries a multiplicity of projecting studs 65. These studs, for example extending almost to the plane of the further sides of the flattened sections .21 as shown. can be arranged in a plurality of rows between the pipes 21 and also in the similar spaces between the sinuous unit and the larger peripheral unit 24.

The entire space bounded by the peripheral unit and not otherwiseoccupied by elements described above, is filled with refractory material 68. Al-

- though a variety of refractories may be employed,

chrome ore prepared in an originally plastic condition is a useful example of such material, and also a somewhat similar composition produced under the trade name Krome-Neutragrog. Thus in building the door the entire assembly of pipes, backing plate 53, and studs 65, may be fastened together, and then the plastic refractory material, for example in'a stiff aqueous paste, is rammed into the space, preferably until it is at least flush with the further sides of the fiattened horizontal pipes 21 as shown in Fig. 5, or even covering them, e. g., up to a plane tangent to the peripheral unit 24. For the usual type of furnace, the door advantageously occupies an area larger than that of the opening to be covered, and thus at least a substantial part of the breadth of the peripheral pipe 24 overlaps the door frame of the furnace structure when the door is closed.

In practice a liquid coolant, such as water, is introduced under pressure through the inlet pipe 44 and withdrawn through the outlet pipe element 5|. The circulation is preferably effected under considerable pressure by a pump or other means (not shown), the path of the water being as illustrated by the arrows, i. e., entering the inlet 44 and then following the sinuous path including the horizontal pipe sections 21 in succession. As the water traverses the section 210 it passes through the upper part of theannular space for cooling the wicket hole, then continues around the 180 L and fiOWs back in section 21d where it similarly traverses the lower part of the wicket hole jacket. Passing into the left hand part of section 21d, the water then travels through the L 46 and on into the upwardly extending pipe section 48 (which is concentrically disposed in the section 30), and thence flows into the surrounding rectangular pipe assembly, from the opening in the wall 41. The coolant then circulates completely around the peripheral path 24,

there being ample space for flow around the outside of pipes 44 and 48, and finally discharges through the outlet fittings 40, 50 and 5|.

It will be observed that a single continuous path is provided for circulation of water, through the central and peripheral sections in succession. According to present preference the line of flow traverses the central portion first, where the heating effect is greatest and maximum heat exchange or cooling is desired, it being thus feasible to have a lower velocity of flow, by virtue of the larger cross-section, in the outer pipe system 24. At the same time, the wicket hole is effectively water-jacketed by a structure form ing part of the same continuous path of flow, so that this exposed portion of the door is efilciently cooled.

As will now be understood, actual connections for water supply and discharge may be made with appropriate flexible or jointed pipe, not shown. It may also be noted that while a variety of types of components may be used in the present invention, including various diameters and thicknesses of pipe and different pipe materials, eminently satisfactory results have been obtained in a door for an open hearth furnace utilizing steel pipe of /2 inch wall thickness, the outer pipe section 24 having an inside diameter of 6 inches and the central length of pipe having, in its circular configuration, an inside diameter of 3 inches, the flattened sections 21 conveniently having inside horizontal and vertical diameters of about 3% inches and 2 inches respectively.

To avoid possible formation of a pocket of air or gas in the corner of the L 38 adjacent the baffle 41, the latter is pierced by a small hole 10 near its upper side. For similar purposes, the baflles 60 and BI in the annular wicket hole jacket may be pierced by like holes, of small diameter, e. g., of the order of less than /2 inch. Although these vent holes in the bafiles 41, 60 and 6| may effect some small return or by-pass flow, the amount of the latter is relatively insignificant, and at the same time effective means is provided to relieve any air or gas bubbles that might otherwise tend to accumulate at these localities.

The operation of the door should now be selfevident, in that a continuous circulation of water from the inlet and through the successive pipe sections to the discharge is afforded. A notable advantage of the structure is that it removes heat more rapidly than prior types of door mentioned hereinabove, and likewise prevents the settlement of sediment at any point. The circulation of coolant is in effect a forced feed,

pressure type, in advantageous comparison with the commonly used older door arrangements wherein the circulation was essentially a gravity or thermal flow, by drift of the water upward in a tank or waterbox. In the present structure the comparatively small water passages have a tendency to cause turbulent flow and thus to carry along any particles of dirt that might otherwise tend to settle. There are no relatively stagnant localities or traps, either for settlement of mud or for the collection of air, and in consequence all the metal parts are effectively cooled without danger, of local overheating and consequent burn-through.

A further advantage of the illustrated device is that the center section, embodying the sinuous length of pipe, is in effect independently supported and thus separately replaceable; if after long use the section leaks or the pipes are found to have burned thin, this part can be easily and inexpensively replaced. Furthermore, these center pipes may expand or contract independently of the outer shell, thus avoiding warping and the creation of stresses that would tear the welds. In addition, the connections along the system are conveniently made with 180 return L's, eliminating the type of stress that tends to crack the welded corners of rectangular boxes or conduits.

The outer shell or frame, comprising the large pipe system 24, is similarly free of rectangular corners and is correspondingly susceptible of long use. In fact, .its rugged construction may well permit its lasting indefinitely, i. e., for reuse even if the center section has to be replaced. The welded pipe connections are likewise at localities where a pull occasioned by expansion or contraction is more even than at the corners, and the curvature of the bends is likewise important, in both the outer and center sections, to facilitate collant circulation.

The flattened shape of the horizontal pipes in the central unit 25 not only provides effective cooling over a greater region between faces of the door, but also contributes substantially to the maintenance in place of the refractory material, in accordance with principles believed to have been unappreciated heretofore. Thus the pipe structure is such that as the refractory softens and even melts because of the extremely high temperatures, a phenomenon occurs that can be described as a shelf formation. More specifically, as the molten or softened refractory flows downward, it comes into contact with and tends to gather upon the horizontal cooling pipes, and by reason of their relatively low temperature, freezes around them. In this manner the pipes are kept covered with refractory material so as to prevent their being locally overheated. At the same time, the flattened pipes, together with the solidified blanket of refractory around each, constitute shelves for supporting the molten or softened material above each section 21, thus tending to hold such material in place.

As will now be apparent, the wicket hole structure is of corresponding special utility in that it is effectively cooled by rapid water flow and yet is of an independently constructed nature, so

that it can if necessary be separately replaced,

i. e., separately of the remainder of the sinuous central unit. At the same time the design, including the described baffles and vents, is such as to prevent air looking or other conditions conducive to overheating.

Extensive operations for test of doors embodying the invention, in fact doors specifically constructed as shown in the drawings and herein described, have demonstrated exceptional utility.

Over a long furnace run of many heats, the improved door remains fully effective, develops no leaks, and retains much of the original refractory material, with the horizontal cooling pipes completely covered. With a prior brick-lined, tank-cooled construction, warped and leaking doors were an extremely frequent occurrence, causing innumerable furnace delays and requiring millwrights to be working on hot furnaces almost constantly. Thus it will be seen that the door of the present invention permits a great saving of time in-furnace operations, and is much safer in use since it is not necessary for repair personnel to be working constantly on hot doors at furnaces filled with molten metal.

It is to be understood that the invention is not limited to the specific apparatus herein shown and described but may be embodied in other forms without departure from its spirit as defined by the following claims.

We claim:

1. A furnace door comprising, in combination, conduit structure defining the periphery of the door and providing a defined, continuous path for flow of coolant around said periphery, the

path of said conduit structure being a closed plane figure, disposed in a vertical plane, a backing plate secured to the conduit structure along one face of the latter, to constitute an outer face for the door and to provide a region surrounded by said conduit structure and closed at one side by said plate, said region occupying nearly all of the area of the door, and means in said region, defining further paths for coolant flow, for cooling the portion of the door constituted by said region, said last-mentioned means comprising a multiplicity of horizontal pipe sections, each extending nearly across said region, said sections being interconected for coolant flow through them in succession, said sections being spaced from each other and from the peripheral conduit but distributively occupying substantially all of said region throughout a plane parallel to said plate,

each of said horizontal pipe sections being horizontally flattened at least nearly throughout its length and thereby having a horizontally fiat upper surface occupying a substantial part of the depth of said region perpendicular to said plate, and refractory material filling all of the spaces in said region and thereby constituting a body of refractory substantially filling said region and substantially surrounding said horizontal pipe sections, said horizontal pipe sections I being closely spaced in a vertical direction to each other, said spacing above each of the aforesaid fiat upper surfaces being sufficiently close so that upon softening of the refractory material by heat to a fiowable state, the said fiat surfaces as cooled by the coolant within the pipe sections will keep the spaces predominantly filled with the refractory material, against loss by flowing out. 2. A furnace door comprising, in combination, a length of pipe defining the periphery of the door and providing a defined, continuous path for fiow of coolant around said periphery. a second length of pipe having a substantially smaller cross section than the peripheral pipe and disposed centrally of the door and following a sinuous course to occupy distributively the area defined by the peripheral pipe, said sinuous length of pipe including a plurality of closely spaced parallel horizontal sections disposed in vertical array and each having a flattened configuration providing a larger horizontal than vertical dimension, curved pipe sections connecting said horizontal sections in series at alternate ends for effecting changes of direction of coolant fiow therein to follow the sinuous course, means interconnecting said first and second lengths of pipe in series for flow of coolant through them in succession, coolant inlet and outlet fittings connected to said lengths of pipe at one edge of the door, an outer face including a plate having a configuration similar to said periphery and welded tangentially to said first length of pipe, a plurality of studs projecting perpendicularly from said outer face inwardly of the door, and refractory material filling the otherwise empty spaces within said periphery defined by said first length of pipe, said horizontal sections being disposed close enough to each other to cooperate effective- 1y with said studs in holding said refractory ma- Number Name Date terial in place when the latter becomes fluid. 1,596,843 McDonnell Aug. 17, 1926 HERMAN W. WILS N. 1,690,619 Christy Nov. 6, 1928 JAMES E. HEYWORTH. 1,780,683 Newkirk Nov. 4, 1930 5 1,792,947 Watson Feb. 17, 1931 REFERENCES 1,844,866 Byrnes Feb. 9, 1932 The following references are of record in the 1,956,959 McDonnell May 1, 1934 file of this patent: 2,219,693 McDonnell Oct. 29, 1940 2,360,855 Dow et a1 Oct. '24, 1944 UNITED STATES PATENTS 10 2,391,010 Dalin Dec. 18, 1945 5:3 Name 3 2 2,395,757 Peters -4 Feb. 26, 1946 Knox Sep 853,698 Hunter May 14, 190': FOREIGN PAIENIS I 5,971 Knox Sept. 16, 1919 Number Country Date v1,515,021 Gerhardt Nov. 11, 1924, 199,198 Germany June 9, 190a

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