Abstract:
A self-anchoring mast for deploying a high-speed submersible mixer in a tank includes operably connected first and second mast members ( 20, 22 ) and a foot member  46  operably connected to the second mast member for supporting the mast in a tank. The second mast member includes a track ( 36, 38 ) for slidably receiving a bearing of the mixer to change the orientation of the mixer in the tank.

Description:
GOVERNMENT INTERESTS 
     The U.S. Government has rights in this invention pursuant to Contract No. DE-AC09-96SR18500 between the U.S. Department of Energy and Westinghouse Savannah River company. 
    
    
     FIELD AND HISTORICAL BACKGROUND OF THE INVENTION 
     This invention was made with Government support under a contract awarded by the U.S. Department of Energy. The Government has certain rights in the invention. 
     The present invention is directed to the deployment of submersible mixers in a tank, and more particularly to a self-anchoring mast for deploying a high-speed submersible mixer in high-level waste (or other industry) tanks to allow the contents to be agitated for processing or transfer. 
     Installation of submersible mixing or agitation equipment in tanks usually requires internal attachment and/or support structures, within the tank, to affix the mixer to the tank wall or floor. This is particularly true when high-energy machines, such as the 50 HP Flygt mixer are installed, in order to safely anchor the unit, to remain stable under the machine&#39;s 1,600 pounds of reaction thrust from a high speed (860 RPM) propeller. If the tank is not originally built with the necessary anchoring systems, personnel must enter the tank to install the anchoring systems. Otherwise, high energy mixers cannot be considered without some other (external) support structure. In hazardous industrial tank applications, such as chemical, volatile or radioactive tanks, this factor alone often precludes high energy mixer installation or requires extensive external support systems. 
     Further, it is often found that deployment of smaller scale agitation equipment is attempted in a tank with the use of cumbersome and expensive tank top superstructures to support the agitator and to provide reaction capability for the mixer&#39;s thrust. In case of large units, such as the 50 HP/1600 pounds thrust of a rotating mixer mast assembly (and larger units), the extremely large bending moment created by the mixer thrust reacted through a 40 to 45 foot moment arm, make the forces and required superstructures prohibitively large and expensive. For example, the 1,600 pound thrust of the subject unit reacted through a 45 foot tank top structure would require a mast and tank-top superstructure capable of resisting a bending moment of more than 72,000 pounds (without a safety margin) before the unit could be expected to remain stable within the tank. Similar large scale superstructures for full scale waste tanks cost hundreds of thousands of dollars to millions of dollars to design and install when related factors, such as structural loading, tank and superstructure codes and hazard ratings, seismic and other natural phenomena design are taken into account. 
     Masts built for radioactive waste tank deployments also require incorporation of a segmented design to facilitate removal of top sections for temporary radiological containment packaging for eventual reuse or final disposal. 
     Therefore, there is a need in the industry for a mast which is self-anchoring and can be quickly deployed in a tank without having to provide support components internally or external to the tank. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     The principal object of the present invention is to provide a self-anchoring mast for deploying a high-speed submersible mixer in a tank which can be quickly deployed, for example, within 30-60 minutes, in a tank with no prior fixtures, supports or other attachments needed within the tank to anchor it for operation. 
     An object of the present invention is to provide a self-anchoring mast for deploying a high-speed submersible mixer in a tank which is preferably about 7,000 pounds center-loaded and allows a high energy mixer, such as a 50 HP mixer, to be lowered into a tank while properly anchoring the entire mast system against the mixer thrust. Smaller mixers with lesser reaction thrust can also be deployed by using similar lighter masts, and larger masts may be used for larger or more powerful mixers, both without the requirement of fixed internal anchors or supports within the tank. In summary, the mast of the invention can be easily used as a tool for installing or deploying small to high energy mixing systems. Another object of the present invention is to provide a self-anchoring mast for deploying a high-speed submersible mixer in a tank which deploys vertically through tank-top openings as small as twenty-two inches. 
     Yet another object of the present invention is to provide a self-anchoring mast for deploying a high-speed submersible mixer in a tank wherein the mixer can operate vertically and be remotely repositioned within the tank for horizontal discharge. 
     An additional object of the present invention is to provide a self-anchoring mast for deploying a high-speed submersible mixer in a tank wherein the mixer can be remotely raised and lowered to operate at any level within the tank. 
     Yet an additional object of the present invention is to provide a self-anchoring mast for deploying a high-speed submersible mixer in a tank which does not require any tank top superstructure. 
     Still yet an additional object of the present invention is to provide a self-anchoring mast for deploying a high-speed submersible mixer in a tank in which a motorized tank top rotation system allows a user to set the rate and sweep angles of up to 360°. 
     Still yet an additional object of the present invention is to provide a self-anchoring mast for deploying a high-speed submersible mixer in a tank which can be quickly installed or removed from the tank with a portable crane. 
     A further object of the present invention is to provide a self-anchoring mast for deploying a high-speed submersible mixer in a tank which allows effective and efficient agitation of the tank contents by allowing the mixer to be periodically reoriented and/or rotated to direct the mixer discharge to different areas or zones of the tank. The rotation capability allows a single mixer to mix more areas of each tank. Further, the “sweep” angle of rotation, as well as the speed of sweep or rotation, are easily variable in order to focus mixer discharge on certain areas of the tank and to help coordinate single or multiple mixers in a larger tank with each other and with the overall fluid motion in the tank. 
     In summary, the main object of the present invention is to provide a mast for deploying a high-speed submersible mixer in a tank which is self-anchoring and allows the mixer/mast assembly to be quickly deployed in the tank with no prior fixtures, supports or other attachments needed within the tank to anchor it for operation. 
     In accordance with the present invention, a self-anchoring mast for deploying a high-speed submersible mixer in a tank, includes a first (or upper) mast member, a second (or lower) mast member operably connected to the first mast member, and a foot member operably connected to the second mast member for supporting the mast in a tank. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, novel features and advantages of the present invention would become apparent from the following detailed description of the invention, illustrated in the drawings, in which: 
     FIG. 1 is an elevational view a stationary mast of the invention, shown being lowered in a tank; 
     FIG. 2 is a elevational view of a rotatable mast of the invention, shown with a mixer in a horizontal position; 
     FIG. 3 is an enlarged view of the rotatable mast shown in FIG. 2, shown positioned on the bottom of a tank; 
     FIG. 4 is an enlarged view of the rotatable mast shown in FIG. 2, showing the mixer in a vertical position prior to being deployed in a tank; 
     FIG. 5 is a partial, enlarged view taken in the direction of arrow X in FIG. 4; 
     FIG. 6 is a partial, enlarged bottom perspective view taken in the direction of arrow Y in FIG. 2; and 
     FIG. 7 is view taken along line  7 — 7  of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As best shown in FIG. 1, a stationary mast assembly SM of the invention, shown being lowered in a tank T, includes an upper mast member  10  and a lower mast member  12  in the form of two laterally spaced supports  14  and  16 . As shown, a mixer M is mounted in between the supports  14  and  16 . 
     As best shown in FIG. 2, a rotatable mast assembly RM of the invention, includes an upper mast member  20  and a lower mast member  22 . The upper mast member  20  includes a hollow pipe  24 , preferably eight inches in diameter and filled with concrete, with a rounded and flanged base  25  for mounting and bolting to a similar flanged surface on the lower mast member  22 . 
     As best shown in FIGS. 2,  3  and  6 , the lower mast member  22  is in the form of a rectangular block  26  mounted to the bottom  28  of base  25 . The block  26  includes a L-shaped track  30  on each side  32  and  34  thereof (FIG.  5 ). Each track  30  includes a vertically extending portion  36  and a horizontally extending section  38  defining a continuous recess therebetween. The track  30  is dimensioned to receive cam follower or bearing units  40  of the mixer M mounted on the support plates  39  and  41  thereof (FIG.  5 ). The bearings  40  slide or travel in the track  30  thereby allowing the mixer M to be positioned horizontally in a deployed position (FIG.  2 ), or in a down position prior to deployment in a tank (FIG.  4 ). In order to move the mixer M between the down and deployed positions and to adjust its position within a tank, a manual or powered hoist mechanism  42  is connected to the mixer M. In FIG. 2, reference numeral  42  designates a submersible mixer power cable for the mixer M. 
     In order to support the mast RM on the floor F of tank T, a foot assembly  46  is mounted at the bottom  48  of the lower mast member  22 . As best shown in FIG. 7, the foot assembly  46  includes a base  50  and a load bearing assembly  52 . A threaded shaft  54  connects the bearing assembly  52  with the bottom  48  of the lower mast member  22 . In FIG. 7, reference numerals  56 ,  58  and  60  designate a thrust bearing, a bushing and a spacer, respectively. Likewise, reference numeral  62  designates a pivot ball, and reference numeral  64  designates a retainer plate for pivot ball  62 . 
     The foot assembly  46  not only supports the entire weight of the mast RM and mixer M (which is typically more than 7,000 pounds) on the tank floor F, but also provides the necessary frictional force to maintain the mast RM anchored to the floor F, and allows the mast RM carrying the mixer M, to be rotated through sweep angles up to 360°. It is noted that since the tank floors could have surface irregularities, the overall configuration of the foot assembly  46  provides automatic angle adjustment, upon landing, to assure the necessary stability and support for the mast RM. 
     Although not shown, a motorized rotation system would be provided adjacent the top of the upper mast member  20  to provide power to rotate the mast RM. Preferably, the rotation system would include user-adjustable sweep angle trip arms, sweep travel limit switch and sweep reversal time delay to allow each mast SM/RM to be set for the range or degree of sweep desired within a tank, with a user-selected time delay between one direction of sweep travel and the subsequent (reversed) direction of sweep. The mast SM/RM may also be equipped with programmable logic controllers (PLC&#39;s), to allow the operating patterns (sweep rate, hold time at various tank positions, positions relative to other masts, etc.) of multiple mast assemblies, within the same tank, to be totally synchronized and programmed. 
     The novel construction of the rotatable mast RM of the invention, allows a user to adjust and operate the mixer M in its horizontal discharge position for any liquid level within the tank. This is accomplished by the L-shaped track  30  provided on the block  26  of the lower mast member  22 . In particular, the elevation of the mixer M within the tank can be easily changed by allowing the mixer bearings  40  to ride in the track  30 . This feature not only allows the mixer M to gradually “mix” its way down into a tank with large bottom deposits, but also allows the mixer M to continue to adjust and operate (mix) as a tank is draining or the mix slurry is being pumped down. This is believed to be a valuable feature as this process continues to deliver increasing mixing energy, per unit of liquid volume, to the same tank as the tank liquid level decreases. This additional energy per unit volume of the fluid is widely recognized as providing significant improvements to the effectiveness of process mixing, particularly in partially mixed tanks. Further, this allows the mixer level to be easily readjusted in the event multiple mixing cycles (refilling the tank to allow continued mixing of residual contents) need to be preformed with successive tank liquid levels. The refilling/re-mixing can be carried out by utilizing the mast RM of the invention to clean waste tanks and prepare them for final closure. This process can also be used for tank cleaning in industrial applications. 
     While this invention has been described as having preferred ranges, steps, materials, or designs, it is understood that it is capable of further modifications, uses and/or adaptations of the invention following in general the principle of the invention, and including such departures from the present disclosure, as those come within the known or customary practice in the art to which the invention pertains and as may be applied to the central features hereinbefore set forth, and fall within the scope of the invention and of the appended claims. It is further understood that the present invention is not limited to the claims appended hereto. 
     PARTS LIST 
     SM Stationary mast assembly 
     RM Rotatable mast assembly 
     M Mixer 
     T Tank 
     F Tank floor 
       10  Upper mast member of SM 
       12  Lower mast member of SM 
       14  &amp;  16  Supports 
       20  Upper mast member of RM 
       22  Lower mast member of RM 
       24  Pipe 
       25  Base of upper mast member  20   
       26  Block 
       28  Bottom of base  25   
       30  L-shaped track 
       32  &amp;  34  Sides of block  26   
       36  Vertical section of track  30   
       38  Horizontal section of track  30   
       39  Support plate 
       40  Bearings 
       41  Support plate 
       42  Hoist mechanism 
       44  Power line 
       46  Foot 
       48  Bottom of lower mast member  22   
       50  Base 
       52  Load bearing assembly 
       54  Pin 
       56  Thrust bearing 
       58  Bushing 
       60  Spacer 
       62  Pivot ball 
       64  Retainer plate