Transfer vessel for molten metal pumping device

Abstract

A transportable vessel for use in transporting molten metal, wherein the transportable vessel is not part of a reverbatory furnace and can be moved to different locations. The vessel includes a transfer conduit in communication with a cavity of the vessel. A molten metal pump can be positioned in the transfer conduit to move molten metal out of an outlet, where the molten metal can move into another structure without the need to tip or tilt the transportable vessel.

Description

FIELD OF THE INVENTION

The present invention relates to a portable vessel, particularly a ladle, used in molten metal processing. The portable vessel (hereafter sometimes referred to as “vessel”) does not include a heating element and is not part of a reverbatory furnace. A molten metal pump may be included as part of a system utilizing the vessel. This application incorporates by reference the portions of U.S. patent application Ser. No. 13/797,616, filed on Mar. 12, 2013, by Paul V. Cooper and U.S. patent application Ser. No. 13/802,040, filed on Mar. 13, 2013, by Paul V. Cooper that are not inconsistent with this disclosure.

BACKGROUND OF THE INVENTION

As used herein, the term “molten metal” means any metal or combination of metals in liquid form, such as aluminum, copper, iron, zinc and alloys thereof. The term “gas” means any gas or combination of gases, including argon, nitrogen, chlorine, fluorine, Freon, and helium, which may be released into molten metal.

A reverbatory furnace is used to melt metal and retain the molten metal while the metal is in a molten state. The molten metal in the furnace is sometimes called the molten metal bath. Reverbatory furnaces usually include a chamber for retaining a molten metal pump and that chamber is sometimes referred to as the pump well.

Known pumps for pumping molten metal (also called “molten-metal pumps”) include a pump base (also called a “base,” “housing” or “casing”) and a pump chamber (or “chamber” or “molten metal pump chamber”), which is an open area formed within the pump base. Such pumps also include one or more inlets in the pump base, an inlet being an opening to allow molten metal to enter the pump chamber.

A discharge is formed in the pump base and is a channel or conduit that communicates with the molten metal pump chamber, and leads from the pump chamber to the molten metal bath. A tangential discharge is a discharge formed at a tangent to the pump chamber. The discharge may also be axial, in which case the pump is called an axial pump. In an axial pump the pump chamber and discharge may be the essentially the same structure (or different areas of the same structure) since the molten metal entering the chamber is expelled directly through (usually directly above or below) the chamber.

A rotor, also called an impeller, is mounted in the pump chamber and is connected to a drive shaft. The drive shaft is typically a motor shaft coupled to a rotor shaft, wherein the motor shaft has two ends, one end being connected to a motor and the other end being coupled to the rotor shaft. The rotor shaft also has two ends, wherein one end is coupled to the motor shaft and the other end is connected to the rotor. Often, the rotor shaft is comprised of graphite, the motor shaft is comprised of steel, and the two are coupled by a coupling, which is usually comprised of steel.

As the motor turns the drive shaft, the drive shaft turns the rotor and the rotor pushes molten metal out of the pump chamber, through the discharge, which may be an axial or tangential discharge, and into the molten metal bath. Most molten metal pumps are gravity fed, wherein gravity forces molten metal through the inlet and into the pump chamber as the rotor pushes molten metal out of the pump chamber.

Molten metal pump casings and rotors usually, but not necessarily, employ a bearing system comprising ceramic rings wherein there are one or more rings on the rotor that align with rings in the pump chamber such as rings at the inlet (which is usually the opening in the housing at the top of the pump chamber and/or bottom of the pump chamber) when the rotor is placed in the pump chamber. The purpose of the bearing system is to reduce damage to the soft, graphite components, particularly the rotor and pump chamber wall, during pump operation. A known bearing system is described in U.S. Pat. No. 5,203,681 to Cooper, the disclosure of which is incorporated herein by reference. U.S. Pat. Nos. 5,951,243 and 6,093,000, each to Cooper, the disclosures of which are incorporated herein by reference, disclose, respectively, bearings that may be used with molten metal pumps and rigid coupling designs and a monolithic rotor. U.S. Pat. No. 2,948,524 to Sweeney et al., U.S. Pat. No. 4,169,584 to Mangalick, and U.S. Pat. No. 6,123,523 to Cooper (the disclosure of the afore-mentioned patent to Cooper is incorporated herein by reference) also disclose molten metal pump designs.

The materials forming the molten metal pump components that contact the molten metal bath should remain relatively stable in the bath. Structural refractory materials, such as graphite or ceramics, that are resistant to disintegration by corrosive attack from the molten metal may be used. As used herein “ceramics” or “ceramic” refers to any oxidized metal (including silicon) or carbon-based material, excluding graphite, capable of being used in the environment of a molten metal bath. “Graphite” means any type of graphite, whether or not chemically treated. Graphite is particularly suitable for being formed into pump components because it is (a) soft and relatively easy to machine, (b) not as brittle as ceramics and less prone to breakage, and (c) less expensive than ceramics.

Three basic types of pumps for pumping molten metal, such as molten aluminum, are utilized: circulation pumps, transfer pumps and gas-release pumps. Circulation pumps are used to circulate the molten metal within a bath, thereby generally equalizing the temperature of the molten metal. Most often, circulation pumps are used in a reverbatory furnace having an external well. The well is usually an extension of a charging well where scrap metal is charged (i.e., added).

Transfer pumps are generally used to transfer molten metal from the external well of a reverbatory furnace to a different location such as a launder, ladle or another furnace. Examples of transfer pumps are disclosed in U.S. Pat. No. 6,345,964 B1 to Cooper, the disclosure of which is incorporated herein by reference, and U.S. Pat. No. 5,203,681.

Gas-release pumps, such as gas-injection pumps, circulate molten metal while releasing a gas into the molten metal. In the purification of molten metals, particularly aluminum, it is frequently desired to remove dissolved gases such as hydrogen, or dissolved metals, such as magnesium, from the molten metal. As is known by those skilled in the art, the removing of dissolved gas is known as “degassing” while the removal of magnesium is known as “demagging.” Gas-release pumps may be used for either of these purposes or for any other application for which it is desirable to introduce gas into molten metal. Gas-release pumps generally include a gas-transfer conduit having a first end that is connected to a gas source and a second submerged in the molten metal bath. Gas is introduced into the first end of the gas-transfer conduit and is released from the second end into the molten metal. The gas may be released downstream of the pump chamber into either the pump discharge or a metal-transfer conduit extending from the discharge, or into a stream of molten metal exiting either the discharge or the metal-transfer conduit. Alternatively, gas may be released into the pump chamber or upstream of the pump chamber at a position where it enters the pump chamber. A system for releasing gas into a pump chamber is disclosed in U.S. Pat. No. 6,123,523 to Cooper. Furthermore, gas may be released into a stream of molten metal passing through a discharge or metal-transfer conduit wherein the position of a gas-release opening in the metal-transfer conduit enables pressure from the molten metal stream to assist in drawing gas into the molten metal stream. Such a structure and method is disclosed in U.S. application Ser. No. 10/773,101 entitled “System for Releasing Gas Into Molten Metal,” invented by Paul V. Cooper, and filed on Feb. 4, 2004, the disclosure of which is incorporated herein by reference.

Molten metal transfer pumps have been used, among other things, to transfer molten aluminum from a well to a ladle or launder, wherein the launder normally directs the molten aluminum into a ladle or into molds where it is cast into solid, usable pieces, such as ingots. The launder is essentially a trough, channel or conduit outside of the reverbatory furnace. A ladle is a large vessel into which molten metal is poured from the furnace. After molten metal is placed into the ladle, the ladle is transported from the furnace area to another part of the facility where the molten metal inside the ladle is poured into molds. A ladle is typically filled in two ways. First, the ladle may be filled by utilizing a transfer pump positioned in the furnace to pump molten metal out of the furnace, over the furnace wall, and into the ladle. Second, the ladle may be filled by transferring molten metal from a hole (called a tap-out hole) located at or near the bottom of the furnace and into the ladle. The tap-out hole is typically a tapered hole or opening, usually about 1″-1½″ in diameter, that receives a tapered plug called a “tap-out plug.” The plug is removed from the tap-out hole to allow molten metal to drain from the furnace and inserted into the tap-out hole to stop the flow of molten metal out of the furnace.

There are problems with each of these known methods. Referring to filling a ladle utilizing a transfer pump, there is splashing (or turbulence) of the molten metal exiting the transfer pump and entering the ladle. This turbulence causes the molten metal to interact more with the air than would a smooth flow of molten metal pouring into the ladle. The interaction with the air leads to the formation of dross within the ladle and splashing also creates a safety hazard because persons working near the ladle could be hit with molten metal. Further, there are problems inherent with the use of most transfer pumps. For example, the transfer pump can develop a blockage in the riser, which is an extension of the pump discharge that extends out of the molten metal bath in order to pump molten metal from one structure into another. The blockage blocks the flow of molten metal through the pump and essentially causes a failure of the system. When such a blockage occurs the transfer pump must be removed from the furnace and the riser tube must be removed from the transfer pump and replaced. This causes hours of expensive downtime. A transfer pump also has associated piping attached to the riser to direct molten metal from the vessel containing the transfer pump into another vessel or structure. The piping is typically made of steel with an internal liner. The piping can be between 1 and 10 feet in length or even longer. The molten metal in the piping can also solidify causing failure of the system and downtime associated with replacing the piping.

If a tap-out hole is used to drain molten metal from a furnace a depression is formed in the floor or other surface on which the furnace rests so the ladle can preferably be positioned in the depression so it is lower than the tap-out hole, or the furnace may be elevated above the floor so the tap-out hole is above the ladle. Either method can be used to enable molten metal to flow from the tap-out hole into the ladle.

Use of a tap-out hole at the bottom of a furnace can lead to problems. First, when the tap-out plug is removed molten metal can splash or splatter causing a safety problem. This is particularly true if the level of molten metal in the furnace is relatively high which leads to a relatively high pressure pushing molten metal out of the tap-out hole. There is also a safety problem when the tap-out plug is reinserted into the tap-out hole because molten metal can splatter or splash onto personnel during this process. Further, after the tap-out hole is plugged, it can still leak. The leak may ultimately cause a fire, lead to physical harm of a person and/or the loss of a large amount of molten metal from the furnace that must then be cleaned up, or the leak and subsequent solidifying of the molten metal may lead to loss of the entire furnace.

Another problem with tap-out holes is that the molten metal at the bottom of the furnace can harden if not properly circulated thereby blocking the tap-out hole or the tap-out hole can be blocked by a piece of dross in the molten metal.

A launder may be used to pass molten metal from the furnace and into a ladle and/or into molds, such as molds for making ingots of cast aluminum. Several die cast machines, robots, and/or human workers may draw molten metal from the launder through openings (sometimes called plug taps). The launder may be of any dimension or shape. For example, it may be one to four feet in length, or as long as 100 feet in length. The launder is usually sloped gently, for example, it may be sloped gently upward at a slope of approximately ⅛ inch per each ten feet in length, in order to use gravity to direct the flow of molten metal out of the launder, either towards or away from the furnace, to drain all or part of the molten metal from the launder once the pump supplying molten metal to the launder is shut off. In use, a typical launder includes molten aluminum at a depth of approximately 1-10.″

Whether feeding a ladle, launder or other structure or device utilizing a transfer pump, the pump is turned off and on according to when more molten metal is needed. This can be done manually or automatically. If done automatically, the pump may turn on when the molten metal in the ladle or launder is below a certain amount, which can be measured in any manner, such as by the level of molten metal in the launder or level or weight of molten metal in a ladle. A switch activates the transfer pump, which then pumps molten metal from the pump well, up through the transfer pump riser, and into the ladle or launder. The pump is turned off when the molten metal reaches a given amount in a given structure, such as a ladle or launder. This system suffers from the problems previously described when using transfer pumps. Further, when a transfer pump is utilized it must operate at essentially full speed in order to generate enough pressure to push molten metal upward through the riser and into the ladle or launder. Therefore, there can be lags wherein there is no or too little molten metal exiting the transfer pump riser and/or the ladle or launder could be over filled because of a lag between detection of the desired amount having been reached, the transfer pump being shut off, and the cessation of molten metal exiting the transfer pump.

The prior art systems also require a circulation pump to keep the molten metal in the well at a constant temperature as well as a transfer pump to transfer molten metal into a ladle, launder and/or other structure.

It is also known to move molten metal from a furnace or other holding vessel to another part of a factory by placing it into a transportable vessel, such as a ladle, and then moving the transportable vessel such as by lifting and carrying it with a forklift. The molten metal in the transportable vessel is then poured into ingot molds or other structures by tilting or tipping the transportable vessel to pour molten metal out. This is a dangerous and relatively difficult procedure because molten metal can spill or exit the transportable vessel unevenly, and turbulence may cause oxidation and dross to form.

SUMMARY OF THE INVENTION

The present disclosure relates to a transportable vessel that does not have to be tilted or tipped to pour molten metal out of it. A pump can be placed into the vessel and operated in order to pump molten metal out of an outlet, and preferably into another structure. This avoids the potential dangers of spilling hot molten metal, and generally more accurately fills ingot molds or other structures. It can also reduce the amount of turbulence, thereby reducing potential dross formation and air bubbles or pockets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side perspective view of a transportable vessel according to aspects of the invention with the pump removed.

FIG. 2 is a top view of the transportable vessel of claim 1 with the pump positioned in the transfer conduit.

FIG. 3 is a side, partial cross-sectional view of the transportable vessel of FIGS. 1 and 2 taken along lines A-A.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to the Figures, where the purpose is to describe preferred embodiments of the invention and not to limit same, FIGS. 1-3 show one preferred embodiment according to an aspect of the invention. A transportable vessel assembly 10 includes a transportable vessel 100 and a pump 200.

Vessel 100 is preferably made of any suitable refractory material wherein such materials are known to those skilled in the art. Vessel 100 has a holding portion 101 with a wall 102 that includes an outer surface 104 and an inner surface 106. As shown, wall 102 is cylindrical although it could be of any suitable shape. Holding portion 101 also has an opening 108 at its top that leads to an inner cavity 110, which retains molten metal placed therein. A bottom 112 is solid and has an inner surface 114 and an outer surface 116.

Vessel 100 also includes a transfer chamber 120, which is preferably comprised of the same material as holding portion 101. The material may be a high temperature, castable cement, with a high silicon carbide content, such as ones manufactured by AP Green or Harbison Walker, each of which are part of ANH Refractory, based at 400 Fairway Drive, Moon Township, Pa. 15108, or Allied Materials. Such a cement is of a type know by those skilled in the art, and is cast in a conventional manner known to those skilled in the art.

Transfer chamber 120 includes walls 122, 124, 126 and 128, which define an enclosed, cylindrical (in this embodiment) uptake cavity 130 that is sometimes referred to herein as an uptake section. Uptake section 130 has a first section 132, and a wider second section 134 above first section 132. In this embodiment sections 130, 132 and 134 are all preferably cylindrical. A channel 136 leads from the bottom of cavity 110 to an opening 138 in uptake section 130. With this structure molten metal flows (preferably due to gravitational force) through channel 136 and to opening 138.

An outlet 140 is in fluid communication with second section 134 above first section 132. It is preferred that the outlet 140 be a short launder structure preferably between about 6″ and 6′ in length, although it can be of any suitable length. Further, it is preferred that, if a launder structure is used as the outlet, it is either formed at a 0° horizontal angle, or tilts backward towards the uptake section 130 at an angle of between 1°-3°, or 1°-5°, or 1°-10°, or at a slope of about ⅛″ for every 10′ of launder length.

Pump 200 includes a motor 210 that is positioned on a platform or superstructure 212. A drive shaft 214 connects motor 210 to rotor 300. In this embodiment, drive shaft 214 includes a motor shaft (not shown) connected to a coupling 216 that is also connected to a rotor drive shaft 218. Rotor drive shaft 218 is connected to rotor 300, preferably by being threaded into a bore at the top of rotor 300.

Pump 200 is supported in this embodiment by a brackets, or support legs 250. Preferably, each support leg 250 is attached by any suitable fastener to superstructure 112 and its flanges rest against the upper surfaces of walls 124 and 126, respectively, preferably by using fasteners that attach to flange 252. It is preferred that if brackets or metal structures of any type are attached to a piece of refractory material used in any embodiment of the invention, that bosses be placed at the proper positions in the refractory when the refractory piece is cast. Fasteners, such as bolts, are then received in the bosses. This method of attachment is known in the art.

When pump 200 is assembled with vessel 100, rotor 300 is positioned in uptake section 130 so that it is received in the narrower first section 132, wherein narrow first section 132 essentially acts as a pump chamber. There is preferably a space of ¼″ or less between the outer perimeter of rotor 300 and the wall of first section 132 in order to create enough pressure to pump molten metal upward into uptake section 130. As shown, rotor 300 is positioned in the lowermost part of first section 132 of uptake section 130 and the bottom surface of rotor 300 is approximately flush with opening 138. Rotor 300 could, however, be located at any suitable location where it would push molten metal upward into uptake section 130 with enough pressure for the molten metal to reach and pass through outlet 140, thereby exiting vessel 100. For example, rotor 300 could only partially located in section 132 (with part of rotor 300 in opening 138, or rotor 300 could be positioned higher in uptake section 130, as long as it fits sufficiently to generate adequate pressure to move molten metal upward and into outlet 140.

Once the pump 200 is attached to vessel 100 to create system 10, in use molten metal is placed in cavity 110, where it fills channel 136 and opening 138 (and may rise to the same level in uptake section 130 as the level in cavity 110). System 10 is then moved to another portion of the factory, such as by using a forklift. Molten metal is removed from vessel 100 preferably not by tipping or tilting it, but by keeping system 10 level and operating pump 200. The operation of pump 200 pushes molten metal upward through section 130, out of outlet 140 and into another vessel or structure.

Having thus described different embodiments of the invention, other variations and embodiments that do not depart from the spirit thereof will become apparent to those skilled in the art. The scope of the present invention is thus not limited to any particular embodiment, but is instead set forth in the appended claims and the legal equivalents thereof. Unless expressly stated in the written description or claims, the steps of any method recited in the claims may be performed in any order capable of yielding the desired product or result.

Claims

1. A transportable vessel for transporting molten metal from one location to another, the transportable vessel being a ladle that is not being part of a reverbatory furnace, the transportable vessel including: an upper perimeter;a cavity for retaining molten metal;a transfer conduit in communication with the cavity; the transfer conduit having an opening in communication with the cavity, a first section having a first cross-sectional area and a second section above the first section, the second section having a second cross-sectional area that is greater than the first cross-sectional area, and an outlet in fluid communication with the second section and leading out of the transfer conduit; wherein the first section is configured to receive a molten metal pump rotor;a transfer conduit upper perimeter having a frame, the frame configured to at least partially support a molten metal pump; anda molten metal pump including: a motor, a rotor, and a shaft, the shaft having a first end connected to the motor and a second end connected to the rotor, wherein at least part of the shaft is positioned in the second section and the rotor is positioned in the first section.

2. The transportable vessel of claim 1 wherein the outlet leads out of the transportable vessel.

3. The transportable vessel of claim 1 that is comprised of refractory material.

4. The transportable vessel of claim 1 wherein the first section is cylindrical and the second section is cylindrical.

5. The transportable vessel of claim 1 wherein there one or more walls separate the cavity from the transfer conduit and the opening is formed in the bottom of at least one of the one or more walls, wherein the opening allows molten metal to pass from the cavity to the opening.

6. The transportable vessel of claim 1, wherein the motor is above the cavity.

7. The transportable vessel of claim 1, wherein the molten metal pump has a platform for supporting the motor, and the platform of the molten metal pump is at least partially supported by the frame of the transfer conduit upper perimeter in order to support the pump.

8. The transportable vessel of claim 1, wherein the transfer conduit includes a first wall having a first outer surface and a second wall having a second outer surface, and the platform has a first side that includes a first centering bracket and a second side that includes a second centering bracket; the first centering bracket being juxtaposed the first outer surface and the second centering bracket being juxtaposed the second outer surface to help center the shaft and rotor in the transfer conduit.

9. The transportable vessel of claim 1, wherein the rotor has a plurality of blades.

10. The transportable vessel of claim 1, wherein the rotor is above the opening.

11. The transportable vessel of claim 9 wherein each blade is vertically oriented.

12. The transportable vessel of claim 9 wherein each blade is a dual-flow blade, with a first, angled portion that moves molten metal upward, and a second portion that moves molten metal outward.

13. The transportable vessel of claim 1 wherein the cavity has an uppermost portion and the outlet has a bottom surface, the bottom surface being lower than the uppermost portion.

14. The transportable vessel of claim 1 wherein the first cross-sectional area is circular.

15. The transportable vessel of claim 1, wherein the second section has a height, and the height is selected so that when the rotor is positioned in the first section, the motor is positioned above the cavity.

16. The transportable vessel of claim 1, wherein the pump does not include a pump base or support posts.

17. The transportable vessel of claim 14 wherein the first cross-sectional area has a diameter, the rotor has a diameter, and the diameter of the rotor is at least ¼″ less than the diameter of the first cross-sectional area.

18. The transportable vessel of claim 14 wherein the first cross-sectional area has a diameter, the rotor has a diameter, and the diameter of the rotor is at least 1/16″ less than the diameter of the first cross-sectional area.

19. A transportable vessel for transporting molten metal from one location to another, the transportable vessel being a ladle that is not being part of a reverbatory furnace, the transportable vessel including: an upper perimeter;a cavity for retaining molten metal;a transfer conduit in communication with the cavity; the transfer conduit having an opening in communication with the cavity, a first section having a circular first cross-sectional area having a diameter, and a second section above the first section, the second section having a second cross-sectional area that is greater than the first cross-sectional area, and an outlet in fluid communication with the second section and leading out of the transfer conduit; wherein the first section is configured to receive a molten metal pump rotor, the rotor having a diameter that is at least 1/16″ less than the diameter of the first cross-sectional area; anda transfer conduit upper perimeter having a frame, the frame configured to at least partially support a molten metal pump.

20. The transportable vessel of claim 19 wherein the outlet leads out of the transportable vessel.

21. The transportable vessel of claim 19 that is comprised of refractory material.

22. The transportable vessel of claim 19 wherein the first section is cylindrical and the second section is cylindrical.

23. The transportable vessel of claim 19 wherein there one or more walls separate the cavity from the transfer conduit and the opening is formed in the bottom of at least one of the one or more walls, wherein the opening allows molten metal to pass from the cavity to the opening.

24. The transportable vessel of claim 19, wherein the transfer conduit includes a first wall having a first outer surface and a second wall having a second outer surface, and the platform has a first side that includes a first centering bracket and a second side that includes a second centering bracket; the first centering bracket being juxtaposed the first outer surface and the second centering bracket being juxtaposed the second outer surface.

25. The transportable vessel of claim 19, wherein the cavity has an uppermost portion and the outlet has a bottom surface, the bottom surface being lower than the uppermost portion.

26. The transportable vessel of claim 19, wherein the first cross-sectional area has a diameter, the rotor has a diameter, and the diameter of the rotor is at least ¼″ less than the diameter of the first cross-sectional area.

27. A transportable vessel for transporting molten metal from one location to another, the transportable vessel being a ladle that is not being part of a reverbatory furnace, the transportable vessel including: an upper perimeter;a cavity for retaining molten metal;a transfer conduit in communication with the cavity; the transfer conduit having an opening in communication with the cavity, a first section having a first cross-sectional area and a second section above the first section, the second section having a second cross-sectional area that is greater than the first cross-sectional area, and an outlet in fluid communication with the second section and leading out of the transfer conduit; wherein the first section is configured to receive a molten metal pump rotor; anda transfer conduit upper perimeter having a frame, the frame configured to at least partially support a molten metal pump; andthe transfer conduit further including a first wall having a first outer surface and a second wall having a second outer surface, and the platform has a first side that includes a first centering bracket and a second side that includes a second centering bracket; the first centering bracket being juxtaposed the first outer surface and the second centering bracket being juxtaposed the second outer surface to help center a rotor shaft and the rotor in the transfer conduit.

28. The transportable vessel of claim 27 wherein the outlet leads out of the transportable vessel.

29. The transportable vessel of claim 27 that is comprised of refractory material.

30. The transportable vessel of claim 27 wherein the first section is cylindrical and the second section is cylindrical.

31. The transportable vessel of claim 27 wherein there one or more walls separate the cavity from the transfer conduit and the opening is formed in the bottom of at least one of the one or more walls, wherein the opening allows molten metal to pass from the cavity to the opening.

32. The transportable vessel of claim 27, wherein the cavity has an uppermost portion and the outlet has a bottom surface, the bottom surface being lower than the uppermost portion.

33. The transportable vessel of claim 27, wherein the first cross-sectional area is circular.

34. The transportable vessel of claim 33, wherein the first cross-sectional area has a diameter, the rotor has a diameter, and the diameter of the rotor is at least ¼″ less than the diameter of the first cross-sectional area.

35. The transportable vessel of claim 33, wherein the first cross-sectional area has a diameter, the rotor has a diameter, and the diameter of the rotor is at least 1/16″ less than the diameter of the first cross-sectional area.