CA2046059A1 - Flow coat galvanizing - Google Patents
Flow coat galvanizingInfo
- Publication number
- CA2046059A1 CA2046059A1 CA 2046059 CA2046059A CA2046059A1 CA 2046059 A1 CA2046059 A1 CA 2046059A1 CA 2046059 CA2046059 CA 2046059 CA 2046059 A CA2046059 A CA 2046059A CA 2046059 A1 CA2046059 A1 CA 2046059A1
- Authority
- CA
- Canada
- Prior art keywords
- zinc
- conduit
- molten zinc
- vat
- linear element
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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- Coating With Molten Metal (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
FLOW COAT GALVANIZING
This continuous galvanizing method and apparatus passes a linear element to be galvanized, e.g., wire, rod, or tube, through a surrounding, relatively short length of conduit which is attached as a cross-tee to the end of a delivery pipe rising from a centrifugal pump submerged in a vat of molten zinc, and continuously flooded with liquid zinc to coat the linear element. The zinc flowing from the open ends of the conduit, and falling as excess from the element being coated, drops back into the vat for recirculation. The vat is covered to provide a substantially closed operating space above the pool of molten zinc to enable the coating to take place in an inert atmosphere.
FLOW COAT GALVANIZING
This continuous galvanizing method and apparatus passes a linear element to be galvanized, e.g., wire, rod, or tube, through a surrounding, relatively short length of conduit which is attached as a cross-tee to the end of a delivery pipe rising from a centrifugal pump submerged in a vat of molten zinc, and continuously flooded with liquid zinc to coat the linear element. The zinc flowing from the open ends of the conduit, and falling as excess from the element being coated, drops back into the vat for recirculation. The vat is covered to provide a substantially closed operating space above the pool of molten zinc to enable the coating to take place in an inert atmosphere.
Description
2046GS~
FLOW COAT GALVANIZING
This ~ nvention relates to a continuous process for galvanizing linear materials such as wire, rod, tube, or pipe, by immersing the axially moving linear S element incrementally in molten zinc.
BACKGROUND OF THE INVENTION
The galvanization of the exterior surface of pipe or conduit as part of the continuous manufacture thereof from an endless strip of sheet metal has been practiced commercially for a number of years. The process basically consists of roll-forming the metal strip into tubular form after drawing it from an endless supply, welding the seam, scarXing and dressing off the weld, and passing the continuously formed tube through a pickling bath and rinse. The tube is then passed through a preheating station and then through a bath of molten zinc, after which the excess zinc is removed, the tube cooled to handling temperature in a water bath, and the tube sheared into finite lengths.
Such an integrated continuous manufacturing process is disclosed, for example, in U.S. Patent 3,226,817, wi h particular emphasis on the galvanization step of the process in U.S. Patents 3,226,817, 3,259,148 and 3,877,975.
In the galvanizing stations of such prior integrated processes, the continuously-formed, rapidly moving tube, after appropriate preparation, was passed through an elongated trough positioned above a pool of molten zinc in a large vat, from which a stream of the liquid metal was pumped to maintain a substantial and overflowing body of molten zinc in the trough as well as to replace the zinc being carried away from the trough as a fluid coating on the tube.
The amount of zinc pumped from the vat to the upper trough was substantial, and as those skilled in the art will appreciate, the formation of dross at the walls of the vat and the trough, and their consequent "
, ~
20~6~
FLOW COAT GALVANIZING
This ~ nvention relates to a continuous process for galvanizing linear materials such as wire, rod, tube, or pipe, by immersing the axially moving linear S element incrementally in molten zinc.
BACKGROUND OF THE INVENTION
The galvanization of the exterior surface of pipe or conduit as part of the continuous manufacture thereof from an endless strip of sheet metal has been practiced commercially for a number of years. The process basically consists of roll-forming the metal strip into tubular form after drawing it from an endless supply, welding the seam, scarXing and dressing off the weld, and passing the continuously formed tube through a pickling bath and rinse. The tube is then passed through a preheating station and then through a bath of molten zinc, after which the excess zinc is removed, the tube cooled to handling temperature in a water bath, and the tube sheared into finite lengths.
Such an integrated continuous manufacturing process is disclosed, for example, in U.S. Patent 3,226,817, wi h particular emphasis on the galvanization step of the process in U.S. Patents 3,226,817, 3,259,148 and 3,877,975.
In the galvanizing stations of such prior integrated processes, the continuously-formed, rapidly moving tube, after appropriate preparation, was passed through an elongated trough positioned above a pool of molten zinc in a large vat, from which a stream of the liquid metal was pumped to maintain a substantial and overflowing body of molten zinc in the trough as well as to replace the zinc being carried away from the trough as a fluid coating on the tube.
The amount of zinc pumped from the vat to the upper trough was substantial, and as those skilled in the art will appreciate, the formation of dross at the walls of the vat and the trough, and their consequent "
, ~
20~6~
erosion due to the scouring action of the recirculating zinc, was likewise substantial. ~he accelerated erosion of the pump impeller and pump housing in this strenuous service required their replacement in days rather than weeks, but was regarded as a necessary maintenance burden to be tolerated as part of the continuous integrated manufacture of galvanized pipe and tube.
SUMMARY OF THE INVENTION
The present invention is based upon the discovery that effective galvanization does not require immersion of the traveling tube or pipe in the molten zinc for the length of time provided by the elongated upper trough of the prior art installations. Effective galvanization is accomplished by the method and apparatus of the invention by passing the tube or pipe through a flowing fountain of zinc confined by a T-section at the top of the delivery pipe of the pump.
The traveling tube or pipe is thus surrounded by molten zinc drawn directly from the pool in the vat without transfer to a secondary pool in an immersion-trough positioned above the main pool in the vat. The reduction of the circulating amount of zinc permitted by this arrangement has greatly reduced the erosion of the pump parts and extended their useful life by an order of magnitude.
DESCRIPTION OF THE DRAWINGS
The invention is described in reference to the accompanying drawings, in which:
FIGURE 1 is a diagrammatic, sectioned elevational view of galvanizing station in accordance with the i~vention, as installed in an integrated line ~or the continuous manufacture of galvanized steel tube or pipe;
FIGURE 2 is a diagrammatic end view of the submersible pump and galvanizing apparatus, lifted from the surrounding walls of the zinc vat; and 20~5g ~ IGURES 3 and 4 are enlarged en~ views of the T-head of the galvanizing apparatus, atop the riser pipe from the pump, showing the relationship of the flow-confining T-head to different diameters of tube or pipe passing tbrough the T-head.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGURES 1 and 2 for a general description of the method and apparatus of the inven-tion, FIGURE 1 shows galvanizing station 10 in an overall system for the continuous manufacture of galvanized pipe or conduit 12. While the method and apparatus illustrated were developed in the stated context, the invention is believed applicable to the continuous galvanization of other linear metal product such as wire or rod.
The conduit 12 passes through the galvanizing station from right to left as viewed in FIGURE 1, delivered in rapid axial motion from a roll-forming station where an endless band of metal is progressively rolled into tubular form with abutting edges which are closed by an electrically welded seam which is scarfed and dressed en route to the galvanizing station. In preparation for galvanizing, which is essentially total immersion of the conduit 12 in molten zinc, the conduit is first cleaned by a pickling bath of acid, followed by a neutralizing rinse, after which the tube is preheated immediately before entry into the galvanizing station.
Preheating is conveniently accomplished by passing the conduit axially through an induction heating coil. As these pregalvanizing steps are well understood in the art, they are not here shown, reference simply being made to the Krengel patent, No. 3,259,148, in which one such system is illustrated and described.
The galvanizing station 10 is essentially an elongated vat 14 of molten zinc constructed in generally rectangular form of welded steel plate and formed to provide a space 16 above the predetermined level of the 2~6~59 pool 18 of liquid zinc therein, maintained in molten condition at about 850~ F., i.e., about ~00 F. above the melting point of zinc. The heating means, not shown, may be gas or oil burners directed against the bottom of the vat.
The space 16 above the pool of liquid zinc is closed by a series of covers 20, 22, and 24 having downwardly extending perimeter flanges 26 which are received in troughs 28 extending around the periphery of the vat and transversely of the vat, as well, to permit the use of multiple covers for convenient access to the interior of the vat for maintenance purposes. The troughs 28 in which the cover flanges are received are partially filled with a granular material, such as sand, lS which forms a barrier to the escape of the inert gas with which the space 16 above the molten zinc is filled and maintained slightly above atmospheric pressure to prevent, or at least limit, the entry of air into that space.
As earlier noted, the conduit 12 enters the g~lvanizing station from the right immediately from the preheater, the housing for which is normally abutted against the entering end of the galvanizing station with an intervening packing of mineral wool or the like to limit the entrainment of ambient air into the galvanizing zone above the molten metal. The conduit enters the station 10 through a hole in the vat wall and thence through a larger tube 30 intended to bring the conduit into more intimate contact with the inert purging gas. The tube then passes through the galvanizing apparatus 32 of the invention and exits the galvanizing zone through an aligned h~le 34 in the far wall 36 of the space.
It will be noted that the far wall 36 of the space is positioned above and extends downwardly into the pool 18 of molten zinc at some distance removed from the end wall 38 of the vat proper, providing a small ;2 ~46~5~
area 40 of open access to the pool of zinc through which the inventory of molten zinc is maintained by the periodic addition of pigs of the metal. That open area also serves the further purpose of receiving the molten zinc trimmed from the outer surface of the conduit 12 by an air knife 42 which consists of a series of nozzles in an annular manifold directed to deliver a cutting stream of compressed air onto the surface of the conduit to trim the excess zinc therefrom, propelling the same in a flat trajectory onto the exposed area 40 of the pool of molten zinc.
In such a manufacturing line, the workpiece conduit 12 travels at a good rate of speed, not infre-quently in excess of 600 feet per minute.
The galvanizing apparatus 32 per se is shown mounted on the central vat cover 22. It comprises essentially a submersible centrifugal pump 44 secured as by welding to the lower end of a thick-walled mounting pipe 46 welded to the underside of the vat cover.
Supporting structure 48 mounted on the upper side of the cover 22 provides two bearings 50 for the vertical shaft 52 of the pump, which is driven at its upper end from a variable speed, vertical electric motor 54 by a V-belt entrained on a pair of speed-reducing pulleys 56 and 58.
At its lower end, there is keyed onto the shaft 52 a double-sided pump impeller (not shown) which when rotating draws the molten zinc from the pool through a central intake in the bottom plate of the pump and a similar central hole in the top plate of the pump, through which the shaft 52 passes with wide clearance to admit the zinc to the upper impeller blades. Access by the liquid zinc to the upper central opening is provided by ports in the supporting structure between the upper plate of the pump and the mounting pipe 46. The mounting pipe 46 completely shrouds the pump shaft from the inert gas in the space 16, eliminating the need for 2046(~S~3 shaft seals between the shaft 52 and cover 22 to prevent the escape of the gas.
The pump delivers the molten zinc to a riser pipe 60 which carries the liquid metal upwardly to a T-head 62 aligned to receive the rapidly moving conduit 12 therethrough. To support the T-head firmly, a pair of brackets 64, welded to the mounting pipe 46 of the pump, encircle the T-head 62 in a split-block configuration in which the two parts of each bracket are secured together by screws to maintain the T-head firmly in position.
The variable speed pump 44 is driven at a speed adequate to deliver a constant upward flow of molten zinc sufficient to surround the conduit traveling through the T-head 62, which, in contrast with the trough type of galvanizing apparatus heretofore employed, may be relatively short, i.e., of the order of 20 inches, with the excess zinc spilling from the ends of the T-head to fall directly into the pool from which it was pumped, it being noted that the surface of the pool 18 beneath the confined, nitrogen-filled space is free from the frothy oxide layer at the uncovered left-hand end of the vat.
In one apparatus of the illustrated kind, the cross-head of the T has an inside diameter of 2-7/8 inches, and has been used successfully in the illus-trated setup to galvanize pipe up to 2.197 inches in outside diameter, i.e., nominal two-inch thin wall electrical conduit, and down to 0.706 inch O.D., i.e., nominal half-inch thin wall conduit for electrical wiring. As will be apparent from FIGURES 3 and 4, different sizes of tube, pipe, or conduit to be galvanized require the pumping of varying amounts of zinc to completely immerse the traveling workpiece on its passage through the T-head, a larger amount of zinc being required for smaller tube in a cross-head of given size, particularly as it is preferred to pump the zinc 2~a~6~5~
at a rate sufficient to flood the annular space between the traveling workpiece and the surrounding T-head for at least a portion of the length of the T-Head. The pumping requirements, however, are much reduced from those of the prior art galvanizing apparatus such as illustrated by Krengel Patent No. 3,259,148, because the pumping of zinc in quantity sufficient to maintain the molten metal in a separate sizable trough above the pool of zinc is not required by the illustrated apparatus, the pressure head to which the zinc must be pumped is reduced, and the galvanizing process may be carried on with less recirculation of the molten metal.
These differences result in very significant benefits.
First, a very noticeable reduction in the erosion of the pumps has been experienced. Whereas pump life had heretofore ranged from one to three days depending upon severity of service, the reduced pumping requirements of the present invention have increased pump life to in excess of thirty days, an order of magnitude improvement.
Secondly, elimination of the upper immersion trough, and the reduction of the recirculating currents in the molten metal at the lower pumping requirements of the apparatus of the invention, have resulted in a noticeable reduction of the formation of dross, and consequent longer life for the steel walls of the zinc vat. Moreover, ~hile not yet realized in existing zinc vats, it is apparent that without the necessity for maintaining an elongated upper galvanizing trough separate from the main body of molten zinc in the vat, the vat itself can be downsized by approximately one-hal~, which will effect further economies of maintenance to the zinc vat and at the same time reduce the amount of energy required to maintain the constant inventory of molten zinc.
2~16~
Lastly, the invention has made possible a significant reduction in the amount of scrap generated on start-up, with concomitant improvement in manufac-turing safety, and reduced the time required to switch the line from galvanized to non-galvanized manufacture.
As to scrap generation, each time the roll-stands of the roll-forming station are changed to set the line up to make a different size of pipe or conduit, adjustments at the roll-forming, and sometimes the welding, stations are usually required before an acceptable seam-closing weld is achieved. Only then is it safe to begin galvanizing, for to pass a zinc-filled, open-seam tube into the cooling bath at the temperature and heat energy levels involved is to invite explosion ~y flash-vaporizing the cooling water.
To avoid this danger, the line must be rununtil an acceptable seam is produced before galvanizing may proceed. In the upper trough and lower vat combina-tion, a not insignificant further amount of time was required to bring the zinc in the upper trough up to the overflow level to produce acceptable product. This in turn resulted in the production of scrap even after an acceptably welded seam was produced.
In the apparatus of the invention, the short lift of the molten zinc from the pool 18 to the cross-head 62 at the top of the riser pipe 60 results in the almost instantaneous production of quality product with little or no scrap of galvanized conduit incident to start-up. The rapid emptying as well as refilling of the riser pipe 60 and cross-head 62, moreover, has reduced changeover of the line from galvanized to non-galvanized manufacture, and vice versa, to simply turning the pump motor off or on, and, either way, results in almost negligible scrap with substantially instantaneous changeover.
The features of the invention believed new and patentable are set forth in the accompanying claims.
SUMMARY OF THE INVENTION
The present invention is based upon the discovery that effective galvanization does not require immersion of the traveling tube or pipe in the molten zinc for the length of time provided by the elongated upper trough of the prior art installations. Effective galvanization is accomplished by the method and apparatus of the invention by passing the tube or pipe through a flowing fountain of zinc confined by a T-section at the top of the delivery pipe of the pump.
The traveling tube or pipe is thus surrounded by molten zinc drawn directly from the pool in the vat without transfer to a secondary pool in an immersion-trough positioned above the main pool in the vat. The reduction of the circulating amount of zinc permitted by this arrangement has greatly reduced the erosion of the pump parts and extended their useful life by an order of magnitude.
DESCRIPTION OF THE DRAWINGS
The invention is described in reference to the accompanying drawings, in which:
FIGURE 1 is a diagrammatic, sectioned elevational view of galvanizing station in accordance with the i~vention, as installed in an integrated line ~or the continuous manufacture of galvanized steel tube or pipe;
FIGURE 2 is a diagrammatic end view of the submersible pump and galvanizing apparatus, lifted from the surrounding walls of the zinc vat; and 20~5g ~ IGURES 3 and 4 are enlarged en~ views of the T-head of the galvanizing apparatus, atop the riser pipe from the pump, showing the relationship of the flow-confining T-head to different diameters of tube or pipe passing tbrough the T-head.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGURES 1 and 2 for a general description of the method and apparatus of the inven-tion, FIGURE 1 shows galvanizing station 10 in an overall system for the continuous manufacture of galvanized pipe or conduit 12. While the method and apparatus illustrated were developed in the stated context, the invention is believed applicable to the continuous galvanization of other linear metal product such as wire or rod.
The conduit 12 passes through the galvanizing station from right to left as viewed in FIGURE 1, delivered in rapid axial motion from a roll-forming station where an endless band of metal is progressively rolled into tubular form with abutting edges which are closed by an electrically welded seam which is scarfed and dressed en route to the galvanizing station. In preparation for galvanizing, which is essentially total immersion of the conduit 12 in molten zinc, the conduit is first cleaned by a pickling bath of acid, followed by a neutralizing rinse, after which the tube is preheated immediately before entry into the galvanizing station.
Preheating is conveniently accomplished by passing the conduit axially through an induction heating coil. As these pregalvanizing steps are well understood in the art, they are not here shown, reference simply being made to the Krengel patent, No. 3,259,148, in which one such system is illustrated and described.
The galvanizing station 10 is essentially an elongated vat 14 of molten zinc constructed in generally rectangular form of welded steel plate and formed to provide a space 16 above the predetermined level of the 2~6~59 pool 18 of liquid zinc therein, maintained in molten condition at about 850~ F., i.e., about ~00 F. above the melting point of zinc. The heating means, not shown, may be gas or oil burners directed against the bottom of the vat.
The space 16 above the pool of liquid zinc is closed by a series of covers 20, 22, and 24 having downwardly extending perimeter flanges 26 which are received in troughs 28 extending around the periphery of the vat and transversely of the vat, as well, to permit the use of multiple covers for convenient access to the interior of the vat for maintenance purposes. The troughs 28 in which the cover flanges are received are partially filled with a granular material, such as sand, lS which forms a barrier to the escape of the inert gas with which the space 16 above the molten zinc is filled and maintained slightly above atmospheric pressure to prevent, or at least limit, the entry of air into that space.
As earlier noted, the conduit 12 enters the g~lvanizing station from the right immediately from the preheater, the housing for which is normally abutted against the entering end of the galvanizing station with an intervening packing of mineral wool or the like to limit the entrainment of ambient air into the galvanizing zone above the molten metal. The conduit enters the station 10 through a hole in the vat wall and thence through a larger tube 30 intended to bring the conduit into more intimate contact with the inert purging gas. The tube then passes through the galvanizing apparatus 32 of the invention and exits the galvanizing zone through an aligned h~le 34 in the far wall 36 of the space.
It will be noted that the far wall 36 of the space is positioned above and extends downwardly into the pool 18 of molten zinc at some distance removed from the end wall 38 of the vat proper, providing a small ;2 ~46~5~
area 40 of open access to the pool of zinc through which the inventory of molten zinc is maintained by the periodic addition of pigs of the metal. That open area also serves the further purpose of receiving the molten zinc trimmed from the outer surface of the conduit 12 by an air knife 42 which consists of a series of nozzles in an annular manifold directed to deliver a cutting stream of compressed air onto the surface of the conduit to trim the excess zinc therefrom, propelling the same in a flat trajectory onto the exposed area 40 of the pool of molten zinc.
In such a manufacturing line, the workpiece conduit 12 travels at a good rate of speed, not infre-quently in excess of 600 feet per minute.
The galvanizing apparatus 32 per se is shown mounted on the central vat cover 22. It comprises essentially a submersible centrifugal pump 44 secured as by welding to the lower end of a thick-walled mounting pipe 46 welded to the underside of the vat cover.
Supporting structure 48 mounted on the upper side of the cover 22 provides two bearings 50 for the vertical shaft 52 of the pump, which is driven at its upper end from a variable speed, vertical electric motor 54 by a V-belt entrained on a pair of speed-reducing pulleys 56 and 58.
At its lower end, there is keyed onto the shaft 52 a double-sided pump impeller (not shown) which when rotating draws the molten zinc from the pool through a central intake in the bottom plate of the pump and a similar central hole in the top plate of the pump, through which the shaft 52 passes with wide clearance to admit the zinc to the upper impeller blades. Access by the liquid zinc to the upper central opening is provided by ports in the supporting structure between the upper plate of the pump and the mounting pipe 46. The mounting pipe 46 completely shrouds the pump shaft from the inert gas in the space 16, eliminating the need for 2046(~S~3 shaft seals between the shaft 52 and cover 22 to prevent the escape of the gas.
The pump delivers the molten zinc to a riser pipe 60 which carries the liquid metal upwardly to a T-head 62 aligned to receive the rapidly moving conduit 12 therethrough. To support the T-head firmly, a pair of brackets 64, welded to the mounting pipe 46 of the pump, encircle the T-head 62 in a split-block configuration in which the two parts of each bracket are secured together by screws to maintain the T-head firmly in position.
The variable speed pump 44 is driven at a speed adequate to deliver a constant upward flow of molten zinc sufficient to surround the conduit traveling through the T-head 62, which, in contrast with the trough type of galvanizing apparatus heretofore employed, may be relatively short, i.e., of the order of 20 inches, with the excess zinc spilling from the ends of the T-head to fall directly into the pool from which it was pumped, it being noted that the surface of the pool 18 beneath the confined, nitrogen-filled space is free from the frothy oxide layer at the uncovered left-hand end of the vat.
In one apparatus of the illustrated kind, the cross-head of the T has an inside diameter of 2-7/8 inches, and has been used successfully in the illus-trated setup to galvanize pipe up to 2.197 inches in outside diameter, i.e., nominal two-inch thin wall electrical conduit, and down to 0.706 inch O.D., i.e., nominal half-inch thin wall conduit for electrical wiring. As will be apparent from FIGURES 3 and 4, different sizes of tube, pipe, or conduit to be galvanized require the pumping of varying amounts of zinc to completely immerse the traveling workpiece on its passage through the T-head, a larger amount of zinc being required for smaller tube in a cross-head of given size, particularly as it is preferred to pump the zinc 2~a~6~5~
at a rate sufficient to flood the annular space between the traveling workpiece and the surrounding T-head for at least a portion of the length of the T-Head. The pumping requirements, however, are much reduced from those of the prior art galvanizing apparatus such as illustrated by Krengel Patent No. 3,259,148, because the pumping of zinc in quantity sufficient to maintain the molten metal in a separate sizable trough above the pool of zinc is not required by the illustrated apparatus, the pressure head to which the zinc must be pumped is reduced, and the galvanizing process may be carried on with less recirculation of the molten metal.
These differences result in very significant benefits.
First, a very noticeable reduction in the erosion of the pumps has been experienced. Whereas pump life had heretofore ranged from one to three days depending upon severity of service, the reduced pumping requirements of the present invention have increased pump life to in excess of thirty days, an order of magnitude improvement.
Secondly, elimination of the upper immersion trough, and the reduction of the recirculating currents in the molten metal at the lower pumping requirements of the apparatus of the invention, have resulted in a noticeable reduction of the formation of dross, and consequent longer life for the steel walls of the zinc vat. Moreover, ~hile not yet realized in existing zinc vats, it is apparent that without the necessity for maintaining an elongated upper galvanizing trough separate from the main body of molten zinc in the vat, the vat itself can be downsized by approximately one-hal~, which will effect further economies of maintenance to the zinc vat and at the same time reduce the amount of energy required to maintain the constant inventory of molten zinc.
2~16~
Lastly, the invention has made possible a significant reduction in the amount of scrap generated on start-up, with concomitant improvement in manufac-turing safety, and reduced the time required to switch the line from galvanized to non-galvanized manufacture.
As to scrap generation, each time the roll-stands of the roll-forming station are changed to set the line up to make a different size of pipe or conduit, adjustments at the roll-forming, and sometimes the welding, stations are usually required before an acceptable seam-closing weld is achieved. Only then is it safe to begin galvanizing, for to pass a zinc-filled, open-seam tube into the cooling bath at the temperature and heat energy levels involved is to invite explosion ~y flash-vaporizing the cooling water.
To avoid this danger, the line must be rununtil an acceptable seam is produced before galvanizing may proceed. In the upper trough and lower vat combina-tion, a not insignificant further amount of time was required to bring the zinc in the upper trough up to the overflow level to produce acceptable product. This in turn resulted in the production of scrap even after an acceptably welded seam was produced.
In the apparatus of the invention, the short lift of the molten zinc from the pool 18 to the cross-head 62 at the top of the riser pipe 60 results in the almost instantaneous production of quality product with little or no scrap of galvanized conduit incident to start-up. The rapid emptying as well as refilling of the riser pipe 60 and cross-head 62, moreover, has reduced changeover of the line from galvanized to non-galvanized manufacture, and vice versa, to simply turning the pump motor off or on, and, either way, results in almost negligible scrap with substantially instantaneous changeover.
The features of the invention believed new and patentable are set forth in the accompanying claims.
Claims (7)
1. In a continuous process for galvanizing linear elements such as pipe, tube, rod, or wire, an improved method of applying molten zinc to the cleansed and preheated linear element to be galvanized comprising:
passing the linear element axially through a length of tubular conduit open at both ends;
supplying molten zinc to said conduit from a pool of molten zinc beneath said conduit at a rate sufficient to immerse the linear element in molten zinc as it passes through said conduit; and collecting by gravity the excess zinc flowing from said conduit and dripping from the coated linear element.
passing the linear element axially through a length of tubular conduit open at both ends;
supplying molten zinc to said conduit from a pool of molten zinc beneath said conduit at a rate sufficient to immerse the linear element in molten zinc as it passes through said conduit; and collecting by gravity the excess zinc flowing from said conduit and dripping from the coated linear element.
2. The method of Claim 1 wherein the molten zinc is pumped to the underside of said tubular conduit intermediate its ends at a rate sufficient to flood the annular space between said linear element and said conduit for at least a portion of the length of said conduit.
3. The method of Claim 2 wherein the flow rate of the zinc pumped into the conduit is adjustable to the flooding requirements of linear elements of different cross-sectional size.
4. In an apparatus for the continuous galvanization of a linear element such as pipe, tube, rod, or wire, having a galvanizing station including a vat for holding a pool of molten zinc and maintaining said pool in a pumpable liquid state, a cover for the vat to maintain a substantially closed space above the pool of molten zinc, means for introducing an inert gas continually into said space to purge the space of atmospheric air, and ingress and egress openings in the walls defining said space for the passage through said space of said linear element to be coated with molten zinc;
an improved applicator for coating said linear element comprising a submersible centrifugal pump suspended from the vat cover to position the pump body below the surface of the molten zinc, a delivery pipe rising from the pump body to convey a stream of molten zinc upwardly from the pool, a cross-tee at the delivery end of the delivery pipe in axial alignment with said ingress and egress openings so as to encircle said linear element traveling through said space; and a motor for driving the pump continuously at a rate adequate to immerse said linear element in molten zinc while passing through said cross-tee.
an improved applicator for coating said linear element comprising a submersible centrifugal pump suspended from the vat cover to position the pump body below the surface of the molten zinc, a delivery pipe rising from the pump body to convey a stream of molten zinc upwardly from the pool, a cross-tee at the delivery end of the delivery pipe in axial alignment with said ingress and egress openings so as to encircle said linear element traveling through said space; and a motor for driving the pump continuously at a rate adequate to immerse said linear element in molten zinc while passing through said cross-tee.
5. The arrangement of Claim 4 wherein the body of the submersible pump is suspended from the vat cover by a rigid thick-walled mounting pipe welded to the underside of the cover, the pump impeller is driven by a shaft extending upwardly through the pipe to bearings mounted on structure secured on the top side of the vat cover, the enclosure of the drive shaft within said mounting pipe seals the passage of the drive shaft through the vat cover against the escape of gas from said space, and said motor is mounted on said structure atop the vat cover and connected to drive the pump drive shaft through a speed reducing drive.
6. The arrangement of Claim 5 wherein the speed of rotation of the pump drive shaft is variable to control the amount of zinc pumped to said cross-tee.
7. The arrangement of Claim 5 wherein the motor is a variable speed motor to control the amount of zinc pumped to said cross-tee.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US71785291A | 1991-06-25 | 1991-06-25 | |
| US717,852 | 1991-06-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2046059A1 true CA2046059A1 (en) | 1992-12-26 |
Family
ID=24883753
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2046059 Abandoned CA2046059A1 (en) | 1991-06-25 | 1991-07-02 | Flow coat galvanizing |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2046059A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115466916A (en) * | 2022-09-20 | 2022-12-13 | 哈尔滨工业大学（威海） | Ultrasonic galvanizing device and galvanizing process thereof |
-
1991
- 1991-07-02 CA CA 2046059 patent/CA2046059A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115466916A (en) * | 2022-09-20 | 2022-12-13 | 哈尔滨工业大学（威海） | Ultrasonic galvanizing device and galvanizing process thereof |
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