US2676792A - Method of and means for shutting down and reheating zinc pots - Google Patents

Description

April 27, 1954 s PEARSON 2,676,792

METHOD OF AND MEANS FOR. SHUTTING DOWN AND REHEATING ZINC POTS,

Filed Feb. 9, 1951 2 sheet -sheet i -Eq.Z

131257729 Wi Iliqm 8. Pearson April 27, 1954 w. 's. PEARSON 2,676,792

METHOD OF AND MEANS FOR SHUTTING DOWNAND REHEATING ZINC POTS Filed Feb. 9, 1951 2 Sheets-Sheet 2 Egz- Ina E 7721:? William S Pearson Patented Apr. 27, 1954 UNITED STATES PATENT OFFICE METHOD OF AND MEANS FOR .SHUTTING DOWN AND REHEATING'ZINC POTS William S. Pearson, Baltimore, Md, assi'gnor to Clifton Conduit Company,,Inc., Baltimore, Md., a corporation of Maryland ApplicationFebruary 9, 1951, Serial N0.'2'1'0, 226

9 Claims.

Thepresent invention relates to a novel method of and means for shutting down and reheating zinc pots such as are used in galvanizing articles.

Zinc pots used in galvanizing articles such as pipe are of large capacity, smaller sizes containing approximately 72,000 lbs. of molten zinc at one time and larger sizes have capacity of up to 300,000 lbs. of molten zinc at one time. While the zinc is in the pots, it is maintained continuously in amolten state by continuous heating, more zinc being added as it is used. Should itbecome necessary to shut down the zinc pot, Whether for repairs or because of fuel failure, or for any other reason, it has heretofore been necessary to remove the molten zinc from the -pot, generally by ladl ing it out. It has heretofore been considered essential to remove the major volume of molten zinc for the reason that as the zinc solidifies, it shrinks and therefore places great inwardly pulling, buckling stresses on the walls of the zinc pot. Furthermore, on reheating the pot, burning out of the side walls of the pot due to overheating and galvanic action results where it is attempted to remel't a solidified fill or content of zinc; During the ladling of the zinc from the pot, a large loss in time and labor, aswellas oxidation of the zinc is incurred. Then, since the molten zinc that has been ladled' out is necessarily placed in smaller containers or left in the ladles to cool and is therefore in relatively small batches or volume, upon reheating the several small batches further loss due to oxidation'results.

I An important object of the present invention is to provide a novel method of shutting down zinc pots without removing the molten zinc content, but leaving the zinc in the pot and allowing the same to cool therein, all without any damage to the zinc pot, either from the solidification of the mass of zinc or from the remelting thereof.

Another object of the invention is to provide a method of shutting down zinc pots which can be eifected quite speedily for emergency repairs or where for any'other reason it becomes necessary toeffect quick shut-down of the pot.

A further object of the invention is to provide a method of shutting down zinc pots which takes into consideration the reheating and remelting o a the zincwithout damage to the pot. 1

Still another object of the invention is to provideimproved' means for shutting down and also for reheating and placing back in service a zinc pot;

Yet another-obj ect' of the inventionistoprovide improved meansfor enabling repair" of zinc P91 2 without the necessity of removing the zinc therefrom when the pot is" shut down.

Other objects, features and advantagesof the present invention will be readily apparent from the ioilowing detailed description of a preferred embodiment thereof taken in conjunction with the accompanying drawings, in which:

Figure l is a top plan view of a zinc pot undergoing shut-d'own and showing the novel means of the present invention employed in the shut-down process;

Figure- 2. is a fragmentary enlarged vertical sectional view taken substantially on the line JET-11 0f Fig. '1 and showing more or less schematically certain apparatusi-nvolved in the practice oi the process of the present invention;

Figure 3 is a fragmentary top plan view of the zinc pot of Fig. 1 showing the same after the zinc. has solidified and with means in place on the body of solidified zinc for accommodating workmen thereon Figure 4 is an enlarged transverse vertical sectionalview taken substantially on line IV-IV of Fig. 3'; and" V Figure 5- is a transverse sectional. view similar to Fig. 4 but showing the zinc pot in the course of'reheating.

A zinc pot M comprises a steel vat having the upright walls thereof encased in a jacket ll of suitable refractory material defining heating chambers [2 along the respective opposite side walls of the pot and into which heating flames l3 (Fig. 5) are directed through suitable port holes l4 by means of appropriate burner nozzles (not shown) utilizing fuel oil or gas as fuel.

Withinthe zinc pot Hl a body of zinc i5 is maintained normally in molten condition as a result of the heating of the zinc pot. Articles such as sections of pipe to be galvanized are dipped intothe body of molten zinc.

On occasion galvanic action, especially adjacent the surface of the molten body of zinc may cause burning out of a portion of a Wall of the zinc pot, thusnecessitating shut-down and repair. Sometimes failure of the burners or of the fuel supply may necessitate temporary shutdown. Sometimes the only alternative to shutdown when there is a Work stoppage as may result from strikes or other causes is to keep the burners going with a consequent loss in fuel and stand-by maintenance.

' According to the present invention, however, the zinc pot can be shut down quickly and effectively and, without any danger of damage to the zinc pot, This is very easily effe ted by separating the main mass of molten zinc from the portion of the molten zinc body which is adjacent to the longitudinal sides of the zinc pot, and while maintaining the main body portion and the side portions thus separated permitting the body of zinc to solidify. The portions of the zinc body adjacent the longitudinal sides of the zinc pot, being exposed to the substantial heat transfer side walls of the zinc pot cool first and without any strain upon the pot side walls inasmuch.

as but a minor proportion of the total volume of zinc in the pot is substantially isolated from the major body of the zinc in the center or inner portion of the zinc pot. Thereafter the major central portion of the zinc body can cool off at whatever rate permitted by the prevailing temperature conditions. It is has-been observed that form of sheets of compressed asbestos board. This is a relatively hard, self-sustaining materialthat readily withstands, handling and sub stantial pressures while nevertheless being possessed of sufficient resilience to prevent breaking when subjected to reasonable bending stresses. 1

Asbestos board of approximately half-inch thickness appears to be ideally suited for this purpose.

When the zinc pot is to be shut down, a pair of pressed asbestos boards H (Figs. 1 and 2) of a any preferred length, and of a width somewhat greater than the depth of the zinc body 15, is secured in appropriately spaced, substantially parallel relation vertically on edge and coextensive to a supporting and positioning framework which in a simple form comprises a pair of angle bars l8. Each of the frame bars I8 is of a length which will completely bridge across the zinc pot l0, Attachment of the zinc divider boards H to the frame bars 58 is effected by engaging the upper margins of the boards between respective pairs of downwardly projecting suitably spaced attachment bars l9 carried adjacent to the opposite ends ofthe respective frame bars I8. Each pair of attachment bars I9 is preferably spaced apart approximately the thickness of the asbestos board and is secured to the margin of the asbestos board engaged thereby by suitable means such as a bolt 28. The respective pairs of attachment bars [9 on each of the frame bars [8 are spaced apart sufficiently to maintain the asbestos boards ll in the desired. spaced relationship, namely, to a spacing which is less than the width of the zinc pot It} to an extent which will provide a preferred narrow spacing between the side walls of the zinc pot and the respective asbestos boards it when the assembly is inserted in the zinc pot. The frame bars i8 are attached adjacent to the opposite ends of the asbestos boards ll so that the assembly comprises a substantially rectangular arrangement with the end portions of the frame bars l8 extending substantially equally to opposite si-desof the rectangular frame thus established.

When the frame bar and board assembly has 4 been completed, it can be readily .placed in the zinc pot by suitable lifting means such as an overhead conveyor 2i, schematically shown in Fig. 2. For this purpose carrying means such as cables or chains 22 may be secured to the frame bars 18 for central engagement above the frame assembly by a carrying-hook .23 of the overhead hoist or crane. Aconv'enient arrangement of the carrying elements 22 comprises attaching the ends thereof to the frame bars 18 adjacent to the carrying bars 19, with the flexible elements 22 looped upwardly for engagement by the crane hook 23. The asbestos board and frame assembly is placed in position with the boards ll in zinc dividing relation in the molten zinc body and with the frame bars I8 resting upon the upper edges of the zinc pot to maintain the asbestos board dividers in place.

Where the zinc pot is longer than can be conveniently accommodatedby available lengths of the asbestos divider boards If, two or more divider board assemblies may be used as shown in Fig. 1.

After the divider board assemblies have been positioned in the molten zinc, the zinc pot is allowed to cool down without any further attention and without necessary removal of any of the molten zinc unless it is desired to lower the surface level of the zinc for purpose of access to an upper portion of the zinc pot wall for repair purposes or the like.

After the zinc has solidified sufiiciently to lock the separator or divider boards ll inwplace, so that upper marginal positioning support of the boards is no longer required, the frame bars [8 can be detached from the separator boards and removed. In order to facilitate such removal, the upper margins of the separator boards ll are preferably disposed sufficiently above the surface level of the zinc body to maintain the depending attachment bars l9 free from the zinc body, especially after the zinc has solidified.

If it is desired to effect repairs in the upper wall portions of the zinc pot Ill, the solidified zinc body will serve as a support for the workmen, but the zinc body, even after solidification, retains a rather high temperature. Therefore, in order to hasten repairs, means are provided for substantially insulating the top of the solidifled or solidifying zinc body so as to permit workmen to work thereabove. To this end an insulating and supporting platform 24 is placed upon the top of the solidified zinc body (Figs. 3 and a), after the upwardly projecting exposed margins of the zinc separator boards ll have been broken off to the surface of the solidified The platform 24, in a simple form, comprises a pipe grille 25 dimensioned to rest upon the top of the solidified zinc body and preferably in marginally supported relation upon the minor side portions of the zinc body which normally will solidify at a higher elevation than the central major portion of the zinc body. In fact, through this arrangement the platform can be placed upon the zinc body even before the central portion is entirely solidified. A coolant such as water is run through the pipe grille 25 the ends of which may for this purpose be in the form of circulation connector extensions 2?. On top of the platform pipe grille 25 is placed a platform cover preferably of an insulating nature such as boards 28. This provides a platform upon which workmen can conveniently work even though the zinc bodyis still of such atempera- 5 ture that direct standing thereon would be hazardous, j v

When the zinc pot is to be reheated, the platform 24., if it has been used, is removed, and the burners started to provide the heating flames i3 .(Fig. 5). Since the minor layers of solidified zinc separated by the asbestos insulating separators I! are relatively thin, they will melt rather quickly and then heat the asbestos separators or dividers I1 sufiiciently so that they will loosen from the central body portion of the zinc and by reason of the substantially lower specific gravity of the asbestos board the latter will float to the top of the zinc body where they can be readily removed by means of the customary handling tongs used in association with a zinc pot. Then the major central .portion of the zinc body gradually melts, but by reason of the relatively high temperature to which the minor side portions of the zinc body have already been heated re-solidification of the side portions by transfer of the heat to the central portion will not occur but a continuous fluid condition will prevail between the side walls of the zinc pot and the melting core of the zinc body. Thereby the side walls of the zinc pot are saved from overheating.

It will thus be apparent that by practicing the present invention, the shut-down time for effecting repairs of zinc pots is greatly reduced. Great labor saving is also effected. Since only the upper surface of the zinc body is exposed to atmosphere great savings in zinc by minimizing of oxidation are also effected. Danger of damage to the zinc pot walls due to overheating is also avoided. so simple is the shut-down process that even a single workman can shut down the zinc pot in an emergency.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. The method of shutting down a zinc pot which comprises separating minor portions of a molten zinc body in the pot adjacent opposite walls of the pot from a major core portion of the molten zinc body, and cooling the molten zinc while maintaining the separation of the minor from the major portions of the zinc body.

2. The method of shutting down a zinc pot which comprises inserting into a molten zinc body in the pot separator panels adjacent to opposing walls of the pot but spaced therefrom, and maintaining the panels in position while the zinc solidifies.

3. In a method of shutting down a zinc pot, the steps of positioning in a body of molten zinc in the zinc pot a pair of pressed asbestos panels, and maintaining the asbestos panels in spaced adjacency to opposite walls of the zinc pot until the zinc has cooled sufficiently to retain the panels in position.

4. The method of shutting down a zinc pot which comprises securing a pair of separator panels in spaced parallel relation a distance slightly less than the space between opposite walls of the zinc pot, and placing the panels into a body of molten zinc in the zinc pot with said panels spaced from respective opposite walls of the zinc pot, and then allowing the body of zinc to solidify.

5. A method of shutting down and reheating a zinc pot which comprises substantially separating minor portions of a body of molten zinc in the zinc pot adjacent to opposite walls of the zinc pot from a major central core portion of molten zinc 6. body, cooling-and solidifyingthe zinc body, and then reheating'the zinc by heating said opposite Side walls until the minor portions of the zinc body are fluid, whereafter said core portion of the zinc body is remelted while said minor portions remain in a fluid side wall protecting state.

6. In a method of shutting down a zinc pot for effecting emergency repairs, the steps of placing separator panels in a molten body of zinc within the zinc pot and with the panels in spaced relation to opposite sides of the zinc pot and with major spacing between the panels to accommodate a major core of the zinc body, maintaining the panels in position in the molten zinc by engagement of upper margins of the panels exposed above the zinc body, substantially solidifying the zinc body, and detaching said exposed margins of the panels above the zinc body so as to accommodate a workmens platform above the zinc body.

7. In a method of shutting down a zinc pot for effecting emergency repairs of wall structure thereof without removing a substantial body of molten zinc within the pot, separating minor portions of the body of molten zinc adjacent to Opposite walls of the zinc pot from a major central core portion of the molten zinc body, and solidifying said minor portions of the zinc body and cooling the major central core portion of the zinc body suificiently to effect shrinkage of the upper surface thereof below the upper surface defined by the solidified minor portions of the zinc body, whereby an insulated workmens platform may be placed upon the tops of the solidified minor portions of the zinc body in bridging relation over said major central core portion of the zinc body so that said repairs can be effected while the major core portion of the zinc body is still in a hot state, said separation of the minor and major core portions of the zinc body prevent ing collapsing of the zinc pot walls as an incident to shrinking of said major central core portion.

8. In a pot structure including opposing walls and having therein a substantial body of molten metal such as zinc subject to substantial shrinkage on solidification, means for shutting down the pot without removal of the body of molten metal comprising spaced parallel upright incombustible panels, frame bars attached to the upper margins of the panels in upright condition spaced apart a predetermined distance less than the spacing between opposite walls of the pot but to accommodate therebetween a major core of the molten metal while separating minor portions of the molten metal between the panels and the zinc pot walls adjacent thereto while cooling the metal to a solid state, and means on said frame bars for transporting the panel and frame bar assembly into position with the panels in the molten metal as aforesaid.

9. In a pot structure including opposing walls and having therein a substantial body of molten metal such as zinc subject to substantial shrinkage on solidification, means for shutting down the pot without removal of the body of molten metal comprising spaced parallel upright incombustible panels, frame bars attached to the upper margins of the panels in upright condition spaced apart a predetermined distance less than the spacing between opposite walls of the pot but to accommodate therebetween a major core of the molten metal while separating minor portions of the molten metal between the panels and the zinc pot walls adjacent thereto while cooling the metal to a solid state, said bars having opposite end portions thereof extending beyond the panels to lie upon the upper edges of said opposite walls of the pot to support the panels with their lower edges above the bottom of the pot, and means appropriately spaced from the ends of said bars and depending therefrom for releasable attachment to the upper margins of the panels.

opposite 5 8 References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Bertrand June 18, 1889 Devereux July 23, 1889 Tim Feb. 13, 1906 Harding Aug. 26, 1930 Burke et a1. June 26, 1939 Amidon Oct. 8, 1940 McClintock Aug. 24, 1948

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