Patent Publication Number: US-2018038373-A1

Title: Advanced material overflow transfer pump

Description:
This application claims the benefit of U.S. Provisional Application No. 62/121,805 filed Feb. 27, 2015, the disclosure of which is herein incorporated by reference. 
    
    
     BACKGROUND 
     The present exemplary embodiment relates to pumps for pumping molten metal, and will be described with particular reference thereto. The present pump embodiment may find particular use in handling molten aluminum, zinc, lead, and/or magnesium and alloys thereof. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications. 
     Pumps for pumping molten metal are used in furnaces in the production of metal articles. Currently, many metal die casting facilities employ a main hearth containing the majority of the molten metal. Solid bars of metal may be periodically melted in the main hearth. A transfer pump can be located in a separate well adjacent the main hearth. The transfer pump draws molten metal from the well in which it resides and transfers it into a ladle or conduit and from there to die casters that form the metal articles. The present invention relates to pumps used to transfer molten metal from a furnace to a die casting machine, ingot mould, DC caster or the like. The subject pump may similarly be used as transportable apparatus for on-demand use and/or for emergency pump out situations. 
     BRIEF DESCRIPTION 
     Various details of the present disclosure are hereinafter summarized to provide a basic understanding. This summary is not an extensive overview of the disclosure, and is intended neither to identify certain elements of the disclosure, nor to delineate the scope thereof. Rather, the primary purpose of this summary is to present some concepts of the disclosure in a simplified form prior to the more detailed description that is presented hereinafter. 
     According to one embodiment of this disclosure, a molten metal pump comprised of an elongated tube having a base end defining an inlet and a top end defining an outlet is provided. The elongated tube is constructed of a reinforced fiber material (RFM). A shaft is disposed within the tube with an impeller secured to the shaft and disposed proximate the base end. 
     According to an alternative embodiment, a molten metal pump comprised of an elongated RFM body is provided. The body includes a vortex region having a vortex region diameter, and an outlet region having an outlet region diameter. The outlet region diameter is greater than the vortex region diameter. An impeller is disposed in or adjacent an inlet. An RFM bearing is disposed in the inlet and positioned to engage the impeller. A shaft extends through the outlet and vortex regions and includes a first end engaging the impeller and a second end adapted to engage a motor. 
     According to a further embodiment, a molten metal pump having an elongated tube having a base end and a top end is provided. The elongated tube is comprised of reinforced fiber material (RFM). The base end defines an opening. A shaft is disposed within the tube and an impeller rotatable by said shaft positioned to at least substantially close the opening. The impeller is arranged such that a radial edge of the impeller forms a dynamic seal with an inner wall of the tube or a base edge of the tube forms a dynamic seal with an upward facing surface of the impeller. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following description and drawings set forth certain illustrative implementations of the disclosure in detail, which are indicative of several exemplary ways in which the various principles of the disclosure may be carried out. The illustrated examples, however, are not exhaustive of the many possible embodiments of the disclosure. Other objects, advantages and novel features of the disclosure will be set forth in the following detail description of the disclosure when considered in conjunction with the drawings, in which: 
         FIG. 1  is a perspective view showing a molten metal transfer system including the pump disposed in a furnace bay (this system is described in U.S. application Ser. No. 13/378,078; the disclosure of which is herein incorporated by reference); 
         FIG. 2  is a perspective partially cross-sectional view of the system of  FIG. 1 ; 
         FIG. 3  is a side cross-sectional view of the system shown in  FIGS. 1 and 2 ; 
         FIG. 4  is a perspective view of the pumping chamber; 
         FIG. 5  is a top view of the pumping chamber; 
         FIG. 6  is a view along the line A-A of  FIG. 5 ; 
         FIG. 7  is a representative impeller design; 
         FIGS. 8( a ) and 8( b )  depict a bottom end of a suitable pumping chamber from a cross-sectional perspective view and a cross-sectional plan view, respectively; 
         FIG. 9  is a schematic cross-sectional plan view of an alternate pump configuration; 
         FIG. 10  is a schematic cross-sectional plan view of a further alternate pump configuration; 
         FIG. 11  is a detailed cross-sectional perspective view of the pump of  FIG. 10 ; 
         FIGS. 12( a ) and 12( b )  depict an impeller suitable for use in the subject pump; 
         FIG. 13( a ), ( b ), ( c ), ( d )  are respectively a perspective view of an alternative pump configuration, a detailed view of the volute chamber, a perspective view of the RFM pump body, and an end view of the pump body; 
         FIG. 14  is a side elevation view (partially in cross-section) of a further alternative pumping chamber configuration; 
         FIG. 15  is a bottom view of the pumping chamber of  FIG. 9 ; and 
         FIG. 16  is a perspective view of a crucible configured to include the transfer pump of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The exemplary embodiment has been described with reference to the preferred embodiments. Modifications and alterations will occur to others upon reading and understanding the detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. 
     The present pump is designed for gently transferring molten metal from crucibles or melting/holding furnaces. It has particular usefulness with foundry and cast house applications, such as transfer of metal from a furnace to a crucible, emptying a crucible, and/or transfer to casting machines/crucible and furnace to furnace. The pump can empty small crucibles because the pump can be manufactured to be relatively compact (e.g. bowl metal immersion depth: 1100 or 800 mm; bowl diameter: from 275 (top) to 235 mm (bottom)). 
     In addition, by utilizing the lay-up technique of RFM manufacture, it is feasible to construct an elongated pump chamber having a substantially constant diameter for example, a 185 mm or smaller internal diameter and/or a 235 mm or smaller external diameter. Given the high strength and thermal shock resistance of RFM, it is similarly possible to construct a relatively thin walled pump chamber (e.g. &lt;50 mm). As such, a pump capable of insertion into into tight spaces, for example, a space less than 25 cm. in diameter is feasible. 
     The pump advantageously has a main body constructed from a composite ceramic material that is both tough and tolerant of mechanic abuse, making the system&#39;s bowl very durable, rigid and user-friendly. These materials are referred to herein as reinforced fiber materials (RFM). 
     The benefits of constructing the pumping chamber of RFM include improved safety: eliminates manual emptying procedures, tilting or using tapping ports; improved metal quality; increased productivity; and minimal pre-heating is necessary. 
     RFM provides at least the following additional benefits: 
     A. the system is easy to remove and reinsert into the molten metal because of its light weight (the system could be permanently mounted, but, it is not necessary). 
     B. Can design a thinner wall (contributing to the lighter weight and low thermal mass). 
     C. Good thermal shock resistance. 
     D. No preheat needed—After warming the system (above 100° C.) to insure no residual moisture in the refractory the RFM can be directly immersed into the molten metal without preheat. 
     E. Can be used for transfer from foundry crucibles to other vessels. 
     Advantageously, the present pump construction allows for 40% or more of the elongated tube to extend above the metal line. 
     With reference to  FIGS. 1-3 , the molten metal pump  30  of the present invention is depicted in association with a furnace  28 . Pump  30  is suspended via metallic framing  32  which rests on the walls of the furnace bay  34  (a transportable version is depicted in  FIGS. 13( c )-( d )  wherein supportive framing is not required). A motor  35  rotates a shaft  36  (comprised of graphite or ceramic, for example) and the appended impeller  38 . A reinforce fiber material (RFM) body  40  forms an elongated generally cylindrical pump chamber or tube  41 . Although the pump chamber and tube are generally depicted herein as cylindrical, it is noted that other shapes are also contemplated. For example, cylindrical is intended to encompass shapes such as elliptic, parabolic and hyperbolic cylinders. Furthermore, it is envisioned that the pump can function with chamber cross-section geometries such as rectangular or square. In addition, it is envisioned that the cross-section geometry can vary throughout the length of the pumping chamber. 
     Body  40  includes an inlet  43  which receives impeller  38 . Bearing rings  44  can be provided to facilitate even wear and rotation of the impeller  38  therein. In operation, molten metal is drawn into the impeller through the inlet (arrows) and forced upwardly within tube  41  in the shape of a forced (“equilibrium”) vortex. At a top of the tube  41  a volute shaped chamber  42  is provided to direct the molten metal vortex created by rotation of the impeller outwardly into trough  44 . Trough  44  can be joined/mated with additional trough members or tubing to direct the molten metal to its desired location such as a casting apparatus, a ladle or other mechanism as known to those skilled in the art. 
     Although depicted as a volute cavity, an alternative mechanism could be utilized to divert the rotating molten metal vortex into the trough. In fact, a tangential outlet extending from even a cylindrical cavity sized equally and concentric to tube  41  can achieve tangential molten metal flow. However, a diverter such as a wing extending into the flow pattern or other element which directs the molten metal into the trough may be beneficial. 
     In addition, in certain environments, it may be desirable to form the base of the tube into a general bell shape, rather than flat. This design may produce a deeper vortex and allow the device to have improved function as a scrap submergence unit. 
     The pump  30  includes a metal frame  108  surrounding the top portion (outlet chamber) of the RFM tube  41 , and includes a motor mount  102  which is secured to the pump  30 . A compressible fiber blank (not shown) can be disposed between the steel frame and the refractory bowl to accommodate variations in thermal expansion rates. Furthermore, the outlet chamber is provided with an overflow notch  123  to safely return molten metal to the furnace in the event of a downstream obstruction which blocks trough  44 . Overflow notch  123  has a shallower depth than trough  44 . 
     Turning now to  FIGS. 4-6 , the body  40  is shown in greater detail.  FIG. 4  shows a perspective view of the RFM body.  FIG. 5  shows a top view of the volute design and  FIG. 6  displays a cross-sectional view of the elongated generally cylindrical pumping chamber. These views show the general design parameters where the pumping chamber  41  is at least 1.1 times greater in diameter, preferably at least about 1.5 times, and most preferably, at least about 2.0 times greater than the impeller diameter. However, for higher density metals, such as zinc, it may be desirable that the impeller diameter relative to pumping chamber diameter be at the lower range of 1.1 to 1.3. In addition, it can be seen that the pumping chamber  41  is significantly greater in length than the impeller is in height. Preferably, the pumping chamber length (height) is at least three feet, or at least five feet, or at least seven feet. It is envisioned that the height of the pump from inlet to outlet can be less than 20 feet, or less than 14 feet. Without being bound by theory, it is believed that these dimensions facilitate formation of a desirable forced (“equilibrium”) vortex of molten metal as shown by line  47  in  FIG. 6 . 
       FIG. 7  depicts an impeller  38  which includes top section  68  having vanes  65  (or passages) supplying the induced molten metal flow and a hub  50  for mating with the shaft  36 . An inlet guide section  70  defines a hollow central portion  54 . Bearing rings  56  can be provided to provide smooth rotation of the impeller within body  40 . The impeller can be constructed of graphite or other suitable refractory material such as ceramic. It is envisioned that any traditional molten metal impeller design having a bottom inlet and side outlet(s) would be functional in the present overflow vortex transfer system. 
       FIGS. 8( a ) and 8( b )  provide a detailed view of one exemplary base end of the pump chamber  41 . In these illustrations, the base end  80  includes side wall  82 , bottom wall  84 , and an RFM bearing ring  86  (not shown in the preceding figures). An impeller receiving inlet  88  is formed in the bottom wall  84  and the bearing ring  86  through which molten metal is received. 
     The RFM material used to construct selected pump components including body  40  can include a ceramic matrix material with a fiber filler material. The ceramic matrix material can be a blend of, for example, Wollastonite and colloidal silica. An exemplary fiber filler material is fiberglass. These materials are blended together to form a slurry. 
     The body can be constructed in a series of layers, by laying precut grades of woven cloth onto a mandrel, adding the slurry and working it into the cloth to ensure full wetting of the fabric. This is repeated to build up successive layers of cloth and matrix material, until a desired thickness is achieved. An exemplary cloth material is glass. 
     Once the product has achieved the desired thickness, it is machined in green (unfired) form to shape the outer surface of the tubular body. The tubular body is then removed from the mandrel and placed in a furnace to dry. A non-stick coating, for example of boron nitride may be applied. 
     The present pump can be considered a portable overflow pump having particular suitability for the foundry market. The pump can be designed to gently raise and transfer molten metal from small crucibles or melting or holding furnaces. It can be used in foundry and cast house applications, such as pumping metal from a furnace to a crucible, emptying a crucible, transferring metal to casting machines and moving metal from one furnace to another. 
     The pump&#39;s compact size makes it easily transported from one vessel to another, and its RFM construction allows for quick metal insertion due to minimal preheating requirements. Its design efficiently raises and transfers molten metal, yielding less dross than traditional transfer methods. It is safer to use than traditional transfer methods that require operators to manually empty, tilt or use tapping ports. 
     Design benefits of the RFM Overflow Pump include the reduction of dross formation during the transfer process and a constant metal flow rate. Though it has a small diameter footprint, its design allows it to proficiently empty a small crucible of about 500 kilograms (1100 pounds) in less than about one minute. 
     The pump is lightweight and has excellent mechanical strength, is non-wetting to molten aluminum and has better heat retention and service life compared to cast iron, fibre laminated board stock and other precast ceramic materials. RFM can reduce downstream oxides and inclusions, help prevent dross buildup, contribute to lower furnace holding temperatures and yield higher quality castings. It also can be formed into complex designs and is highly resistant to thermal shock. 
     The inorganic material used to make the matrix (RFM) can be of any type provided that it is compatible with the fabric that is embedded therein; it can be molded or thermo-formed; and it is rigid, strong and sufficiently heat-resistant to handle molten metal and remain rigid at molten metal temperature. 
     The inorganic material can be a glue made from colloidal silica like the one sold under the tradename QF-150 and 180 by Unifrax. It can also be a sodium or potassium silicate slurry or a zircon-based coating like the one sold under the tradename EZ 400 by Pyrotek, Inc. 
     In one example, the RFM can comprise 8 to 25% by weight of an aqueous phosphoric acid solution having a concentration of phosphoric acid ranging from 40 to 85% with up to 50% of the primary acidic function of the acid phosphoric acid neutralized by reaction with vermiculite. It also encompasses from 75 to 92% by weight of a mixture containing wollastonite or a mixture of wollastonite of different grades, and an aqueous suspension containing from 20 to 40% by weight of colloidal silica, such as the one sold under the trademark LUDOX HS-40 by Sigma-Aldrich. The weight ratio of the aqueous suspension to the wollastonite within the mixture can range from 0.5 to 1.2. 
     To prepare the tube, one may prepare a slurry of the selected RFM and impregnate an open weave fabric with the slurry either by direct application or by dipping. The resulting product may then be left in a mold of preselected shape until the matrix has hardened. The rigid tube can be unmolded in less than two hours, without need of any drying and/or heating steps even though a 10 hour drying step at ambient temperature followed by a several hours of firing at elevated temperature (such as 375° C.) may be beneficial. 
     While the pump and impeller designs depicted in  FIGS. 2-8 ( b ) (a first embodiment) are highly effective in achieving the transfer of molten metal from a furnace, its usefulness may be most effective with furnace environments in which the molten metal is at a high temperature, for example, above 1,400° F. In environments where the molten metal temperature is less than, for example, 50° F. above the melting point of the metal being transferred, an alternative design may be desirable. Moreover, in a relatively low temperature molten metal environment it is feasible that the relatively high mass base and impeller components of the first embodiment can cause a decrease of molten metal temperature within the pump body that results in hardening of the metal and potential damage to the pump assembly. 
     For example, testing was performed using the first pump embodiment equipped with external and internal thermocouples in the base region. The pump was immersed into molten metal at a temperature of 1350° F. The Table below summarizes the recorded temperatures from immersion. 
     
       
         
           
               
               
               
            
               
                   
                   
               
               
                   
                 Temperature 
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Time 
                 Internal 
                 External 
                 Condition 
               
               
                   
                   
               
               
                   
                 0 
                 1247° 
                 1317° 
                 without graphite impeller 
               
               
                   
                 0 
                 1126° 
                 1332° 
                 with graphite impeller 
               
               
                   
                 4 min. 
                 1118° 
                 1330° 
                 with graphite impeller 
               
               
                   
                 6 min. 
                 1134° 
                 1331° 
                 with graphite impeller 
               
               
                   
                 9 min. 
                 1154° 
                 1330° 
                 with graphite impeller 
               
               
                   
                   
               
            
           
         
       
     
     As the skilled artisan will discern, the initial insertion of the pump into the molten metal can cause a significant decrease of the molten metal temperature inside the pumping chamber. This decrease in temperature is enhanced by the presence of the impeller. If the molten metal being transferred is maintained by the associated furnace at a temperature relatively close to the metal solidus temperatures, freezing of the pump is a possibility. 
     In accord with a second embodiment, the RFM bottom wall  84  (see  FIGS. 8( a ) and ( b ) ) has been removed. The RFM bearing ring  86  has also been removed and the mass of the impeller has been reduced. 
     With particular reference to  FIG. 9 , a base region of a pump chamber  100  receives an impeller  102 . Rather than form an interface between the impeller and a bottom wall of the elongated tube, a dynamic seal  104  is formed between a top surface  106  of the impeller main body  108  and a bottom edge  110  of a tube body  112 . 
     The impeller  102  can include a hub  114  receiving a shaft  116 . Vanes  118  extend from the hub on the top surface  106 . An inlet  120  is provided in a bottom surface  122  with passages (not shown) extending through the main body  108  to transport metal from outside the pump to the pumping chamber  100 . 
     As utilized herein, the term “dynamic seal” is intended to reflect a seal formed between the rotating impeller and the tube body. The dynamic seal is intended to encompass a range of fluid tightness from substantially absolute wherein a lubricating molten metal film is formed between the impeller and the tube body but through which substantially no molten metal flow occurs during operation to a situation wherein a measurable amount of molten metal can pass between the impeller and the tube body. However, it is desirable that the maximum quantity of molten metal entering the pumping chamber through the dynamic seal is less than the quantity entering through the impeller inlet. Moreover, it may be most desirable that the tube body act as a bearing surface during impeller rotation. 
     Turning to  FIGS. 10 and 11 , an alternative configuration is depicted wherein a dynamic edge seal  150  is formed between the radial edge  152  of the impeller  102  and an internal wall  156  of the tube body  112 . In either embodiment, it is conceivable that the impeller include a radial bearing ring  158 , but such bearing ring is optional, particularly if the impeller is constructed of a ceramic material. Also contemplated but not illustrated is a slight underhang (e.g. “j” shaped terminal portion) of the tube body configured to form a dynamic seal with a bottom facing corner of the impeller. 
     Turning now to  FIGS. 12( a ) and 12( b ) , an impeller  175  (comprised of graphite or ceramic, for example) without a bearing ring (comprised of silicon carbide, for example) is depicted. The impeller  175  includes a disc shaped body  177  having an upper surface  179  upon which a plurality of vanes  181  are disposed. Vanes  181  extend from a hub  183  in which a shaft (not shown) can be received. Hub  183  can be configured to include recesses  185  for receiving dowels that provide an interface through which the shaft imparts torque to the impeller. Impeller  175  further includes an inlet  187  in a bottom surface  188  in fluid communication with a plurality of passages  189  via which molten metal passes through the disc-shaped body  177  for discharge adjacent upper surface  179  where it is acted upon by the vanes  181  to impart the desired radial flow that creates the vortex through which molten metal is lifted upwardly within the tube for eventual discharge at the elevated outlet 
     As a visual comparison between the impeller of  FIG. 7  and the impeller of  FIGS. 12( a ) and ( b )  will demonstrate, a significant quantity of impeller mass has been eliminated by providing an open top vane architecture and an inwardly recessed inlet. In certain instances it may be desirable for the RFM tube adjacent the impeller to have an internal diameter between about 15 and 30 centimeters and for the impeller to have a volume of between about 500 and 1,500 cubic centimeters. As an example, it may be desirable to characterize this relationship as a ratio of impeller volume to tube cross-section area as less than about 3:1. Furthermore, it may be desirable for the walls of the RFM tube adjacent the impeller to be in a range between about 1.27 and 3.81 centimeters in width. In addition, it may be desirable to provide an impeller having vanes spaced from the walls of the pump tube to a greater extent than the portion of the impeller forming the dynamic seal to increase the quantity of molten metal resident therein. For example, the vanes may extend less than 75% of a distance between the hub and the radial edge of the disc-shaped body. 
     Referring now to  FIG. 13( a ), ( b ), ( c ), ( d ) , the advantages of utilizing an RFM tube are readily apparent. More particularly, in the depicted design, the pump  200  is constructed to be selectively movable between locations requiring lifting and transfer of molten metal. More particularly, the tube  201  can be constructed with a relatively thin wall, for example between about 18 and 50 mm due to the high strength and structural integrity of the RFM material. Furthermore, the tube can be constructed to have a cylindrical shape of at least substantially uniform diameter throughout its length. This is advantageous for insertion of the pump into tight spaces. In the depicted embodiment, a motor mount  203  overlays the volute chamber  205  and posts  207  secure the motor mount to a metal cladding  209  bound to a top edge of the volute chamber. Motor  211  is secured to the motor mount  203 . A shaft  212  extends between the motor and an impeller (not shown) disposed in base region  214 . 
     Three lifting eyes  213  are provided on the motor mount  203  to facilitate the movement of the pump  200  between desired locations. Moreover, pump  200  can be lifted via eyes  213  using a fork lift or ceiling hoist and transported to a crucible or furnace well for removal of molten metal. The pump  200  can be temporarily positioned by the lift mechanism in the apparatus being emptied and removed when the desired amount of molten metal has been removed. 
     With reference to  FIGS. 13( c ) and ( d ) , the pump body shows inlet  220  in base region  214 . Inlet  220  includes an RFM bearing ring  221 . The pump body further includes three legs  223  which allow the pump  200  to rest on the furnace/crucible floor while positioning inlet  220  above the floor to avoid ingestion of an excessive amount of solids. The volute end  225  of the pump is also illustrated and includes volute chamber  227  and outlet  229 . Overflow spillway  231  is also illustrated. 
     In operation, powering motor  211  rotates shaft  212  and the provided impeller wherein rotation of the impeller draws molten metal through inlet  220 . The impeller ejects the molten metal radially within the tube  201  (the internal diameter of the tube being larger than the external diameter of the impeller at the impeller outlet). The radially ejected molten metal forms a rotating vortex of molten metal that climbs the walls of the tube, reaching volute chamber  227  where it is directed horizontally outward through outlet  229 . 
     Turning next to the embodiment of  FIGS. 14 and 15 , an alternative construction of the pump chamber is depicted. More particularly, the pump chamber  300  has been constructed of RFM and includes three legs  301  which can be utilized to elevate the chamber  300  above the floor of the molten metal inclusive vessel, which has been found to reduce tendency for clogging. In addition, in this embodiment the chamber  300  is provided with a plurality of bores  303  oriented to receive bolts  305  provided for retaining an RFM bearing ring  307 , positioned to mate with a corresponding bearing ring of an impeller (not shown). 
     Turning next to  FIG. 16 , the inventive pump concepts contained within this disclosure are applied to a crucible configured. Moreover, crucible  400  is provided includes a tubular column  401  adjacent a side wall  403 . Tubular column  401  will include an inlet  402  in fluid communication with the main molten metal containing region  404  of the crucible. The crucible and/or the tubular column can be constructed of RFM. The tubular column  401  is provided with a volute top portion  405  facilitating the discharge of molten metal from the crucible via a spout  407 . A selectively removable motor  409 , motor mount  410 , shaft  411  and impeller  412 , collectively assembly  413 , can be introduced to the tubular column  401 , where upon rotation of the impeller by the motor creates the vortex of molten metal within the tubular column  401 , lifting the molten metal to the volute top portion  405  for ultimate discharge via the spout  407 . 
     Crucible side wall  403  can be equipped with posts  415  configured to receive and releasably mate with the motor mount  410 . In this manner, the assembly  413  can be selectively associated with a crucible for molten metal removal and then detached as desired. Advantageously, the assembly can be utilized to service multiple crucibles. 
     The invention has many advantages in that its design creates an equilibrium vortex at a low impeller RPM, creating a smooth surface with lithe to no air intake. Accordingly, the vortex is non-violent and creates little or no dross. Moreover, the present pump creates a forced vortex having a constant angular velocity such that the column of rotating molten metal rotates as a solid body having very little turbulence. 
     Other advantages include the elimination of the riser component in traditional molten metal pumps which can be fragile and prone to clogging and damage. In addition, the design provides a very small footprint relative to the traditional transfer pump base and has the ability to locate the impeller very close to the bay bottom, allowing for very low metal draw down. As a result of the small footprint. The device is suitable for current refractory furnace designs and will not require significant modification thereto. 
     The pump has excellent flow tune ability, its open design structure provides for simple and easily cleaning access. Advantageously, only shaft and impeller replacement parts will generally be required. In fact is generally self-cleaning wherein dross formation in the riser is eliminated because the metal level is high. Generally, a lower torque motor, such as an air motor, will be sufficient because of the low torque experienced. 
     Optional additions to the design include the location of a filter at the base of the inlet of the pumping chamber. It is further envisioned that the pump would be suitable for use in molten zinc environments where a very long, pull (e.g. 14 ft.) is required. Such a design may preferably include the addition of a bearing mechanism at a location on the rotating shaft intermediate the motor and impeller. Furthermore, in a zinc application, the entire construction could be manufactured from metal, such as steel or stainless steel, including the pumping chamber tube, and optionally the shaft and impeller.