Patent Publication Number: US-8109208-B2

Title: Cheese vat having adjustable shaft seal assembly

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Invention 
     The present invention relates to a cheese process vat. More specifically, the present invention relates to a cheese process vat including a shaft seal assembly having a seal holder that is an adjustable shaft seal assembly. In yet another embodiment, the present invention relates to a method of cleaning an interior of a cheese process vat. 
     2. Description of the Related Art 
     In the 1970&#39;s, a number of companies manufactured enclosed vertically agitator shafted vats for making cheese and cheese-like products. These enclosed vats improved upon inconsistent cheese making results generally noted in the open cheese making vats that were common in those days. The enclosed vats also reduced the risk of foreign material contamination and the interior could be automatically cleaned with automatic, clean-in-place (CIP) spray systems. Initially, these vats had vertical agitator shafts. Such vats include the Damrow® Double O™ Vat and the Stoelting® Vertical Vat. 
     In the late 1980&#39;s, cheese process vats having horizontal agitator shafts were introduced. Known horizontal agitator shaft cheese process vats, such as that disclosed by Jay (U.S. Pat. No. 4,989,504), are dual horizontal agitator shaft cheese process vats that are believed to provide considerably improved product yields as compared to the prior vertically agitator shafted vats. 
     Cheese process vats have also been made having a single horizontal agitator shaft. Previous cheese process vats having single horizontal agitator shafts typically have a majority of their blade clusters or agitator panels on one side of the agitator shaft with blade panels generally confined to about 100° or less of the full 360° radius of the agitator shaft, creating a substantially unbalanced weight distribution with respect to the placement of the agitator panels within the agitator shaft assembly. Such vats include the Tebel OST, the Wincanton and the Stoelting single agitator shaft cheese process vats. 
     In these vats, during the initial stages of cutting the coagulum, the entire mass of coagulum has a tendency to rotate with the agitator shaft assembly. To compensate for this rolling/rotating action, it is usually necessary to increase the speed of the agitator shaft assembly, which is believed to negatively influence yield, by shattering the coagulum, thus allowing fat release and creation of cheese fines that are drained out of the curd with the whey when the whey is separated from the cheese curds. Further, if a horizontal agitator shaft assembly has a substantially unbalanced weight distribution with respect to the placement of the agitator panels along the agitator shaft, the motor, speed reducer and bearings experience uneven loads as the agitator shaft rotates. The loading along the shaft will generally alternate from a high positive load to one that might be called a free fall, regenerative or negative load. This can cause uneven wear and premature failure of the above mentioned parts. 
     Known methods of attaching blade clusters or agitator panels to the agitator shaft include welding the agitator panels to stubs located on the main agitator shaft. The blunt edges of the stubs during the cutting phase can damage the coagulum enough to negatively affect product yield. 
     The original enclosed cheese making vats employed vertical agitator shafts and therefore, did not require a sophisticated water-tight and sanitary seal assembly. The agitator shaft came through an opening in the top of the vessel, which was always above the level of the liquid. With the advent of cheese making vats with horizontal agitator shafts, however, it became necessary to seal the agitator shaft so milk or product would not leak as both ends of the agitator shaft are typically below liquid level during cheese making operations. Under rules promulgated by the USDA, it also became necessary to provide a suitable system to clean the seal assembly and, as further required by the USDA, provide a leak detection port which is open to the floor during the production of cheese. Existing cheese process vat seals consist of a combination shaft seal and face seal molded into one unit such as that disclosed by Jay (U.S. Pat. No. 4,861,044). Typically, the cleaning/sanitizing solution is pumped, through a hole that is molded into the seal between the shaft seal and the face seal. 
     Testing and evaluating the cheese making performance is contingent on the cheese making process. The cheese making process is made up of numerous steps that change for each type of cheese. Cheese making steps generally include, but are not limited to the following: 
     First, the sanitized vat is filled with fluid milk and combined with other cheese constituents like calcium, a starter culture a rennet solution and a coloring agent. As the cheese process vat is filling, the agitator shaft assembly automatically starts agitating the fluid milk when the milk fill weight reaches a first stir set point. During the “fill” step, other actions take place, including heating the milk in the vat body, if the milk temperature is not at a required set point. 
     To add any desired coloring agent, appropriate valves are opened and a color pump generally starts to add a coloring agent, preferably annatto, to the milk when the milk fill weight reaches a preset point. The coloring agent is metered into the milk. 
     When the milk fill weight reaches another preset point, another set of valves are opened and a pump begins to pump a starter culture into the milk. The starter is generally a bacterial culture in a medium such as milk that is added to enhance flavor and lower pH. Food colorings, calcium and the like may also be added at this point. 
     Once the vat is full of fluid milk, a modern, programmed cheese process vat will generally advance to a “stir” step commonly referenced as a “rennet stir” step. Rennet solutions include proteolytic enzymes that promote coagulation of the milk when the enzymes react with casein micelles to produce casein proteins that bind together to form a coagulum that is a protein matrix in which a portion of the milk fat is retained. Once the operator is aware of the appropriate time to add the rennet solution and operator initiates a programmed addition sequence, the agitator shaft will generally ramp up to a programmed agitation speed in a stir mode. 
     Known methods of introducing the rennet solution are known to include manual addition using a pail from the top of the vat, spraying over the top of the surface of the milk using spray nozzles or a gravity feed orifice from an overhead manifold. 
     Following the addition of the rennet solution, the agitator shaft assembly rotation speed is generally increased to a further programmed speed in the stir mode/direction to thoroughly mix the rennet into the fluid milk. In an attempt to obtain a homogeneous mixture, in which the rennet is evenly distributed to every part of the fluid milk within the vat body, the contents of the vat are often agitated aggressively. This can be counter productive, however, as the coagulum may not set as well under such conditions. After this step is timed out, the cheese process vat advances to an “anti-swirl” step in which the direction of the rotation of the agitator panels is reversed. 
     The “anti-swirl” step helps to slow down the action of the milk rotating in one direction. The agitator shaft assembly will then begin a cut mode at high RPMs and gradually reduce the agitating speed until stopped. After this step is timed out, the cheese process vat advances to a “set” step in which the casein matrix is allowed to set or coagulate. 
     The agitator shaft assembly does not rotate in the “set” step. In the “set” step, the milk protein coagulates while the agitator shaft assembly idles to permit the coagulum to form. After the programmed set time expires, the operator will check the set. When the set is ready, the operator will initiate a series of “cut” steps. 
     In the “cut” steps, the agitator shaft assembly gradually ramps up to a programmed speed in which the coagulum is cut into individual cheese curd matrices (cheese curd). After these steps are timed out, the cheese process vat advances to a “heal” step. 
     In the “heal” step, the agitator shaft assembly does not rotate. This step allows the outer skin or “shell” of the curd to develop in order to reduce “bleeding” of fat and moisture from the curd. After this step is timed out, the cheese process vat advances to a “forwork” step. 
     In the “forwork” step, the agitator shaft ramps up in a selected cut or stir mode. In this step, the curd is gently stirred at a relatively slow agitation speed. After this step is timed out, the cheese process vat advances to a “cooking” step. 
     In the “cooking” step, the agitator shaft assembly increases up to a programmed speed in the stir or cut direction. A vat steam shut off valve or hot water shut off valve generally opens to permit steam or hot water to circulate in the outer jacket surrounding the interior of the vat body. An intermittent agitating time parameter is available to help keep curd from knitting together at low agitator shaft assembly speeds. The “cooking” step will not advance until both the time and temperature required by the program are met. The cheese process vat will then advance to a “predraw/settle” step once cooking is complete. 
     In the “predraw/settle” step, the agitator shaft assembly does not run. The agitator shaft assembly is parked in a vertical position. Curd gradually drops into the whey fluid mixture in the vat body because it is denser than the whey that remains after the cheese curd is formed. After this step is timed out, the cheese process vat advances to a “predraw” step. 
     In the “predraw” step, the agitator shaft assembly does not run as it remains parked in the vertical position. A predraw valve opens and a predraw pump starts to remove whey from the vat body. Once a set amount of whey is drawn off, the predraw pump shuts off and the predraw valve closes. 
     Next, during an “end stir” step, the agitator shaft assembly increases to a programmed speed in the stir direction. The “end stir” step ends and a “curd transfer” step begins once the programmed time for the “end stir” step has elapsed. 
     Finally, in the “curd transfer” step, appropriate valves are opened and curd pumps will pump the curd and any remaining whey out of the vat body to finishing areas. During the curd transfer, the agitator shaft assembly speed increases and has the option to be in a “stir” mode or a “cut” mode. 
     Once empty, the interior of the vat is usually cleaned automatically with the use of internally mounted spray devices that are part of a sanitizing system generally called a “clean in place” (CIP) system. 
     Although cheese making has advanced significantly in the past 20 to 30 years, it will be appreciated that a cheese process vat that increases cheese yield is needed in order to make automated cheese making more efficient and less reliant upon operators that possess the knowledge of the “art” of cheese making. What is also needed is a cheese process vat that is easier to clean, easier to operate without undue wear on parts and easier to operate in ways that produce cheese more efficiently. What is further needed is a cheese process vat with a shaft seal assembly that is easily adjustable. 
     SUMMARY OF THE DISCLOSURE 
     The cheese process vat of the present invention preferably includes a cylindrical vat body having an interior that is substantially horizontal and sized appropriately to contain a resulting product. Preferred cheese process vats of the present invention further include a single, generally horizontal agitator shaft with agitator panels including blades that have two distinct functions. While rotating in one rotational direction, sharp edges on the blades cut the coagulum. For stirring operations, rotating the agitator shaft in the opposite direction, unsharpened edges of the blades stir the mixture without additional cutting. 
     The present invention further includes a unique arrangement of the agitator panels. In preferred embodiments, the agitator panels are substantially balanced along an axis of the agitator shaft in a generally planar fashion. Substantially balanced agitator panels provide uniform or even wear on parts, like motor parts, speed reducer parts, variable frequency drive parts and the like. This wear reduction minimizes lost production time and product loss due to mid-cycle vat break-downs caused by premature failure of the previously mentioned parts. 
     The agitator shaft assembly of the present invention preferably further includes disk-like collars that are welded to the agitator shaft while the agitator shaft is external to the vat body. If necessary, the agitator shaft can be straightened at that time with known methods and techniques. After installation of the straightened agitator shaft, the agitator panels are welded to the outer diameter of the disk-like collars. Welding to the outer diameter of the disk-like collars virtually eliminates any agitator shaft distortion caused by heat generated during the welding process. In addition, the disk-like collar is believed to be gentler on the coagulum when the agitator shaft rotates because the number of blunt edges being forced through the coagulum is minimized. 
     The blade clusters or agitator panels preferably have of a pair of thick, radially positioned primary blades attached to the collar, thinner secondary blades attached to the primary blades and parallel to a centerline of the agitator shaft and a set of radially arrayed tertiary blades, which are also thin blades, attached to the secondary blades. A complete agitator shaft assembly has multiple agitator clusters positioned to provide a substantially balanced assembly preferably arrayed in a single plane through the centerline of the agitator shaft. This substantially balanced array will preferably have substantial balance with respect to either or both of the surface area of the respective agitator panels arrayed on the respective opposite sides of the agitator shaft or the weight of the respective agitator panels arrayed on the respective opposite sides of the agitator shaft. 
     Additionally, the cheese process vat of a further embodiment of the present invention further includes an injection nozzle assembly, even more preferably, a plurality of injection nozzle assemblies. Each injection nozzle assembly can inject a stream of a rennet solution through the surface of the fluid milk within the vat body well below the surface of the fluid milk, thereby providing a more effective distribution of the rennet solution. This process of injecting the rennet mixture below the surface of the fluid milk improves the cheese making process by incorporating the aqueous rennet solution into the milk faster, more pervasively and more effectively. An effective incorporation of the rennet solution will create coagulation that is substantially uniform throughout the fluid milk thereby increasing yield. 
     The improved cheese process vat of a further embodiment of the present invention further includes an adjustable shaft seal assembly. Because the agitator shaft is secured in the vat body below the operating liquid level, a shaft seal of some sort will be necessary to prevent the contents of the cheese process vat from leaking through the joint between the seal assembly and the agitator shaft. Since a cheese process vat is subject to regulatory scrutiny, the shaft seal assembly also has to be easily cleanable and provide a leak detection port. The shaft seal assembly preferably includes a seal assembly subunit including an inner seal holder, a face seal and a separate shaft seal, each of which surround and are concentric with the agitator shaft; wherein the shaft seal and the face seal are engaged with and separated by the inner seal holder. The face seal and the shaft seal each have a seal body and a seal lip. The face seal lip extends away from the face seal body and is pre-loaded such that the face seal lip engages an inner face of the agitator shaft. The shaft seal lip extends away from the shaft seal body and is pre-loaded so that the shaft seal lip engages the agitator shaft. The inner seal holder defines a first portion of a fluid conduit channel and the agitator shaft, the inner seal holder, the face seal and the shaft seal cooperate to define a fluid accessible cleaning chamber to which cleaning fluid can flow via a fluid conduit channel that leads to the exterior of the vat. 
     As mentioned above, the adjustable seal assembly of a further embodiment of the present invention is preferably pre-loaded against the inner face of a concentric flange of the agitator shaft having a wear disk. The face seal lip and a shaft seal lip are designed and configured to act as check valves where liquid can pass in one direction only when under pressure, unless the seals fail. When the interior of the vat body is being cleaned and when the appropriate flow control valves are actuated, cleaning/sanitizing solution is allowed to flow into the chamber and because the shaft seal lip is designed to be angled toward the chamber, it stays closed and prevents the solution from leaking out into the joint between the agitator shaft and shaft seal assembly. Since the face seal lip is angled away from the chamber, the face seal lip actually opens up as the solution flows under pressure into the chamber, thus cleaning the chamber and the backside of the face seal lip. The seal assembly of the present invention preferably aids in detecting leaks due to the failure of the face seal. While in use, the face seal is positioned so that any leakage of milk or whey into the chamber from the interior of the vat body will leak onto the floor from the fluid conduit channel, providing a visual indicator to the operator that the face seal has failed and that seal maintenance is needed. 
     In preferred embodiments of the present cheese process vat the face seal may be adjusted without having to enter the vat body and without having to take the seal assembly apart and rebuild it. To adjust the face seal, the user simply loosens the external fasteners holding the seal assembly together and removes at least one shim from each fastener, then retightens the respective fasteners. The shims provide an easy way to adjust or increase lip pressure against the inner face of inner face wear plate. 
     Thus, it is an object of the present invention to provide a cheese process vat having a horizontal agitator shaft having substantially balanced agitator panels in both surface area and weight. 
     Thus, it is another object of the present invention to provide a cheese process vat having at least one injection nozzle assembly to inject rennet solution during the cheese making process. 
     Thus, it is yet another object of the present invention to provide a cheese process vat having an easily adjustable shaft seal assembly that includes a fluid accessible cleaning chamber. 
     These and other objects and advantages of the invention will appear more fully from the following description, made in conjunction with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views. And, although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, in which corresponding reference numerals and letters indicate corresponding parts of the various embodiments throughout the several views, and in which the various embodiments generally differ only in the manner described and/or shown, but otherwise include corresponding parts; 
         FIG. 1  is an elevated perspective view of a preferred cheese process vat of the present invention; 
         FIG. 1A  is a schematic plan view of the cheese process vat shown in  FIG. 1 ; 
         FIG. 2  is an elevated, exploded perspective view of the vat body of the cheese process vat of  FIG. 1 , showing the vat body of the cheese process vat from an elevated position on the side of the vat body opposite the side shown in  FIG. 1 ; 
         FIG. 3  is an elevated perspective view of the vat body of the cheese process vat shown in phantom from the perspective of  FIG. 2 , but illustrating the preferred agitator shaft assembly (not all parts of the vat body are shown for better clarity); 
         FIG. 4  is a cross-sectional view of the cheese process vat as seen from the line  4 - 4  of  FIG. 1 , but depicting the planar alignment of the agitator panels and position of a representative rennet injector assembly; 
         FIG. 5  is an enlarged, cross-sectional, side view of the rennet injector assembly illustrated in the area partially circumscribed by the line  5 - 5  of  FIG. 4 ; 
         FIG. 6A  is a partially broken away, partial cross-sectional, schematic side view of the vat body and the agitator shaft assembly of the cheese process vat of  FIG. 4  showing the preferred agitator panels in a vertical alignment; 
         FIG. 6B  is a partial schematic view of the agitator shaft and the agitator panels shown in  FIG. 6A , but illustrating respective surface areas A, B and C of respective planes passing through respective agitator panels  42   a ,  42   b  and  42   c  and ending at the distal edges of each of the respective agitator panels; 
         FIG. 7  is an enlarged partial, perspective view of a collar  76  interconnecting an agitator panel to an agitator shaft of the agitator shaft assembly shown in the area partially circumscribed by line  7 - 7  of  FIG. 3 ; 
         FIG. 8  is an enlarged partial cross-sectional, orthographic side view of the collar interconnecting an agitator panel to the agitator shaft as seen from line  8 - 8  in  FIG. 7 ; 
         FIG. 9  is an enlarged partial, orthographic top view of the collar interconnecting an agitator panel to the agitator shaft as seen from line  9 - 9  in  FIG. 7 ; 
         FIG. 10  is an enlarged partial cross-sectional side view of the preferred shaft seal assembly of the present invention shown in the area partially circumscribed by the line  10 - 10  of  FIG. 6A ; 
         FIG. 11A  is an enlarged partial, cross-sectional side view of the shaft seal assembly of  FIG. 10 , but illustrating the fluid forces applied to the face seal lip by a fluid in the interior of the vat body and showing the flow of such fluid in a circumstance where the face seal fails to prevent fluid from the interior of the vat body from entering the seal chamber  106 ; 
         FIG. 11B  is an enlarged partial, cross-sectional side view of the shaft seal assembly of  FIG. 10 , but illustrating the fluid forces applied to the face seal lip and the shaft seal lip by cleaning solution introduced under pressure into the seal chamber  106 ; 
         FIG. 12  is an enlarged, partial cross-sectional side view of the fluid forces similar to those shown in  FIG. 11B ; 
         FIG. 13  is an enlarged partial, cross-sectional side view of the seal assembly of  FIG. 10 , but where the shims  122  (see in  FIG. 12 ) have been removed in order to adjust the seal assembly subunit and decrease the distance between inner face of the agitator shaft and the face seal body; 
         FIG. 14  is an enlarged partial cross-sectional, perspective view of the inner seal holder  92  of the shaft seal assembly of  FIGS. 10 ,  11 A,  11 B,  12  and  13 ; and 
         FIG. 15  is an enlarged partial cross-sectional, end view of the preferred seal assembly of the seal shown in  FIG. 10  as seen from the line  15 - 15  of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and to  FIGS. 1-13  in particular,  FIG. 1  illustrates a preferred cheese process vat  10  of the present invention. The cheese process vat  10  has an enclosure or vat body  12  having an interior  28  (see  FIGS. 3-6A ), an agitator shaft assembly  14  (see FIGS.  3 , 4 ,  6 A and  6 B) and a seal assembly  16 , which is best illustrated in detail in  FIGS. 10-13 . The agitator shaft assembly  14  includes a hollow stainless steel agitator shaft  40  that extends between the respective ends  39 ,  41  of the vat body  12 . 
     The cheese process vat  10  is supported by a set of cradles  18  resting on a support frame assembly  20 . Preferably, the support frame assembly  20  and cradles  18  support the vat body  12  at an angle or tilt away from the horizontal such that contents of the cheese process vat  10  will drain completely with relative ease through a drainage port  22  (see  FIG. 6A ). The preferred cheese process vat  10  of the present invention further comprises a roof  24  on the top of the vat body  12 . The shape of the roof  24  corresponds to a vat access opening  26  in the vat body  12  (see  FIG. 2  in particular) and provides an area where someone may access the interior  28  of the vat body  12  (see  FIG. 3 ) prior to completion of the cheese process vat  10  of the present invention in which the roof  24  is preferably welded to the vat body  12  proximate the vat access opening  26 . Once the roof  24  is welded to the vat body  12 , the only way for a person to get into the interior  28  is to enter via a personnel access port or “manway”  36 . 
     The manway  36  is an important access portal for entrance into the interior  28  of the vat body  12  during completion of the assembly of a cheese process vat  10  of the present invention, because the agitator shaft assembly  14  will be completed inside the interior  28  when agitator panels or blade clusters  42   a ,  42   b ,  42   c  are passed into the interior  28 , via a roof opening  37  in the roof  24 , so that the agitator panels  42   a ,  42   b ,  42   c  can be welded onto the agitator shaft  40 . In preferred embodiments, the blade clusters  42   a ,  42   b ,  42   c  are welded to disk-like collars  76 , which were in turn welded to the hollow agitator shaft  40  before the agitator shaft is introduced into the interior  28  of the vat body  12 . Because the heat generated during welding procedures can cause an agitator shaft  40  to become warped or to develop an irregular axis about which it will be forced to rotate, welding the collars  76  to the agitator shaft  40  outside of the interior  28  is advantageous because of the greater availability of the counter measures to address the effects of heat on the straightness of the agitator shaft  40 . Once the collars  76  are welded to the agitator shaft  40 , and the agitator shaft is straightened, the agitator shaft can be inserted into the interior and the blade clusters can be welded to the respective collars  76  without much concern about the effect of the heat from the subsequent welding operations, because the collars provide significant heat dissipating capacity that significantly diminishes the risk posed by the need to weld the blade clusters  42   a ,  42   b ,  42   c  to the agitator shaft  40 . The roof  24  is actually welded in place before the blade clusters  42   a ,  42   b ,  42   c  are welded to the agitator shaft  40 , an assembly operation that can be completed following delivery to a cheese making facility where the cheese process vat will eventually be used. The blade clusters  42   a ,  42   b ,  42   c  could be placed in the vat body  12  prior to putting on the roof  24  or, as discussed above, they can be inserted through the roof opening  37  that exists in the roof  24 . In either case, the blade clusters  42   a ,  42   b ,  42   c  are preferably welded to the agitator shaft  40  after the roof  24  is welded to the vat body  12 . 
     Now referring also to  FIG. 1A , during the cheese making process, rennet is diluted in a container  30  with water or another aqueous fluid prior to pumping the rennet solution (not shown) to the interior  28  of the vat body  12  via a fluid line  32  connecting the container  30  to a injection nozzle assembly  60  via a pump “p”, so that fluid passing through the injection nozzle assembly  60  into the interior  28  of the vat body  12  can do so under pressure as required in order to inject a stream of fluid  63  into fluid milk (not shown) in the interior  28  via a plurality of fluid transfer assemblies  60  interconnected with a plurality of fluid transfer port  70 . Optionally, additives such as a food coloring agent, calcium, starter cultures and the like can also be pumped from the mixing container  30  through the fluid transfer line  32  to the respective injection nozzle assemblies  60  and the plurality of fluid transfer port  70 . 
     The mixtures of rennet and water or any other aqueous fluid, or calcium, coloring agents or other similar additives, with aqueous fluids, are either prepared in the mixing container  30  or are pre-mixed and then added to the mixing container  30 . In preferred embodiments, the mixture or solution is added to fluid milk (not shown) in the interior  28  under pressure created by the pump “p”. Although any of the aforementioned constituents can be mixed with the fluid milk in this way, the most critical is the rennet solution because of the preference for quickly mixing the rennet solution fully in the fluid milk as a means for obtaining an even distribution of the rennet within the entire volume of fluid milk in the vat body  12  during cheese making activities. In normal practice, the rennet solution is drawn into an interconnecting line  32   a  by a pump “P” that directs the rennet solution through a fluid transfer line  32   b  and into injection nozzle assemblies  60  (see also  FIGS. 4-5 ) via an injection nozzle tube  64 . The injection nozzle assemblies  60  (see also  FIGS. 4-5 ) inject the rennet solution into the vat body  12  and will be discussed in more detail below. 
     FIGS.  3  and  6 A- 9  show an agitator shaft assembly  14  of the present invention that may be used in conjunction with a vat body such as that of  FIGS. 1 and 2 . The agitator shaft assembly  14  includes a hollow, generally horizontal agitator shaft  40  and agitator panels or blade clusters  42   a ,  42   b ,  42   c  interconnected to the agitator shaft  40  with disk-like collars  76 . In preferred embodiments, each of the agitator panels  42   a ,  42   b ,  42   c  include at least one relatively thick, radially positioned primary blade  44  attached to the disk-like collar  76 , relatively thinner secondary blades  46  (see  FIGS. 6A-7 ) attached to the primary blades  44  (see  FIGS. 6A-7 ) so that they are positioned generally parallel to the axis or centerline  49  of the agitator shaft  40  and a set of relatively thin, radially positioned or arrayed tertiary blades  48  (see  FIGS. 6A-7 ) attached to the secondary blades  46 . It will be appreciated that the teachings of the present invention are not limited to a specific number or arrangement of blades and that each of the respective blade clusters or agitator panels may have either more of or fewer of any of the respective primary, secondary or tertiary blades. 
     The agitator panels  42   a ,  42   b ,  42   c  of the present invention will preferably further include large paddles  50  and small paddles  52 . The small paddles  52  and the large paddles  50  extend from the agitator panels  42   a ,  42   b ,  42   c  at an angle “a” (see also  FIG. 9 ), which will be from about 2 to about 25 degrees, preferably from about 5 to about 20 degrees, more preferably from about 10 to about 17.5 degrees, most preferably about 15 degrees to aid in circulating the contents of the vat body  12  during cheese making. 
       FIG. 6B  illustrates respective surface areas A, B and C of respective planes  43   a ,  43   b ,  43   c  passing through respective agitator panels  42   a ,  42   b ,  42   c  and ending at the distal edges  45   a ,  45   b ,  45   c  of each of the respective agitator panels  42   a ,  42   b ,  42   c . As discussed further below, the surface areas A and C of respective planes  43   a ,  43   c passing through the first and third agitator panels  42   a ,  42   c , respectively, when combined together, is preferably substantially the same as a surface area B of a plane  43   b  passing through agitator panel  42   b  and ending at distal edges  45   b  of the second agitator panel  42   b . It is preferably that the agitator shaft assembly of the present invention is substantially balanced with respect to the centerline  49  of the shaft in regard to surface area of respective planes passing through the respective agitator panels on one side of the shaft and the surface area of respective planes passing through the respective agitator panels on the other side of the shaft. It is also preferably that the agitator shaft assembly of the present invention is substantially balanced with respect to the centerline  49  of the shaft in regard to weight of respective agitator panels on one side of the shaft and the weight of respective agitator panels on the other side of the shaft. 
     In preferred embodiments of the present invention, the weight of the second panel  42   b  is substantially the same as the total weight of the two end panels  42   a ,  42   c  on respective ends  47   a ,  47   c  of the agitator shaft assembly  14 . In the preferred embodiments, the agitator panel  42   b , located in the middle of the agitator shaft  40 , is positioned on the opposite side of the agitator shaft  40  from the two end panels  42   a ,  42   b , thus rendering the agitator shaft assembly substantially balanced both in respect to weight of the opposing agitator panels and surface area of the planes passing through the respective opposing agitator panels and ending at distal edges thereof. It will be appreciated that, in alternate embodiments of the present invention, the agitator shaft assembly may include any number of agitator panels, but that it will be preferred to keep the agitator panels generally within a single plane extending through the centerline  49  of the agitator shaft and to keep balanced both the weight of opposing agitator panels and/or the surface area of planes passing through the respective opposing agitator panels and ending at distal edges thereof. 
     It will be appreciated that the agitator panels  42   a ,  42   b ,  42   c  stir and move the fluid milk, coagulum or whey/curd slurry(not shown) within the vat body  12  as the agitator shaft assembly  14  rotates. The primary, secondary and tertiary blades  44 ,  46 ,  48 , respectively, each have one sharpened edge  54  and an opposite, unsharpened edge  56 . Cutting of the coagulum occurs when the agitator shaft  40  is rotated in a direction where the sharpened edges are leading. Stirring occurs when the agitator shaft assembly  14  is rotated in the opposite direction, when the unsharpened edges are leading. 
     When the agitator shaft assembly  14  illustrated in FIGS.  3  and  6 A- 9  rotates counterclockwise into a coagulum or “set”, only about one-half of the coagulum (not shown) is penetrated by about one-half of the total agitator panel surface area, either the half associated with surface areas A and C or the half associated with surface area B. When that one-half of the total agitator panel area comes out of the coagulum, during its upward rotation, the other half of the coagulum is being penetrated by the other half of the total agitator panel surface area in its downward rotation. Because the total agitator panel surface area is divided generally in half between the opposing sides of the agitator shaft assembly, this action is less likely to cause the entire mass of coagulum to rotate with the agitator panels, as compared to known cheese process vats where these panels are not opposing panels, as they are in the present invention, but rather grouped panels gathered in a particular radial segment of the radially plane perpendicularly bisecting the agitator shaft. With the present invention, increasing the agitator shaft assembly speed is not necessary either for mixing, cutting or stirring as it has been seen to necessary when a larger percentage of the entire coagulum is moved by a grouped array of agitator panels that are unevenly balanced with respect to the agitator shaft. 
     In the cooking and stirring operations, since the agitator shaft assembly is balanced, only one half of the curd collection is potentially lifted by half of the total agitator panel surface area. Due to a phenomenon related to the angle of repose, some of the curds fall off the panel toward an area not populated with an agitator panel. As the agitator shaft rotation continues, the here-to-fore downward rotating agitator panels are now upward rotating and again, the curds, due to the angle of repose fall off the agitator panel toward an area not populated with an agitator panel. Throughout the stirring and cooking operations, this end to end movement enhances stirring, which is essential to heat transfer between the curds and whey, which are heated by the hot steam or hot water in the vat liner. An effective agitation will yield higher quality curds with a reduced risk of acid spots in the finished product. 
     The most preferred agitator shaft assembly  14  of the present invention has multiple blade clusters  42   a ,  42   b ,  42   c  that are positioned to provide a substantially balanced agitator shaft assembly. As shown in FIGS.  3  and  6 A- 9 , the agitator panels  42   a ,  42   b ,  42   c  are balanced by having a single agitator panel  42   a ,  42   c  on each end  47   a ,  47   c  of the agitator shaft  40  extending in the same radial direction as a larger agitator panel  42   b  extending from the middle of the agitator shaft  40  on the opposite side of the agitator shaft  40 , extending at approximately 180 degrees from the outer agitator panels  42   a ,  42   c . It will be appreciated that the previous arrangement is a preferred arrangement and that any configuration of the agitator panels wherein the agitator panels are balanced around the agitator shaft may be utilized in alternate embodiments. Further, it is highly preferable to include outer agitator panels  42   a ,  42   c  having extensions  58  that are shaped to correspond to the curvature of the ends of the vat body  12 . The preferred extensions  58  are a portion of the respective outer agitator panels  42   a ,  42   c , and the respective ends  39 ,  41  of the vat body  12  by only about an inch, preferably about a half an inch, leaving little room for cheese curd or chunks of coagulum to flow around the edges  47   a ,  47   c  of the outer agitator panels  42   a ,  42   c  as they sweep along the interior  28  of the vat body  12  proximate the respective ends  39 ,  41  of the vat  10 . The agitator panel extensions  58  provide for more efficient and effective cutting and stirring as one rotation of the agitator shaft assembly  14  will sweep the entire contents of the vat body  12 , but generally in two halves of the entire contents. The agitator panel extensions  58  include secondary blades  44  and tertiary blades  48  that stem from the outer primary blades  44  of the respective outer agitator panels  42   a ,  42   c  of which the respective agitator panel extension  58  is a part. 
     Referring now also to  FIG. 6B ,  FIG. 6B  illustrates respective surface areas A, B and C of respective planes  43   a ,  43   b ,  43   c  passing through of respective agitator panels  42   a ,  42   b  and  42   c  and ending at the distal edges  45   a ,  45   b ,  45   c  of each of the respective agitator panels  42   a ,  42   b ,  42   c . As previously discussed, it is preferably that the agitator shaft assembly of the present invention is substantially balanced about the shaft both with respect to surface area and weight of the respective opposing agitator panels. TABLE 1 below provides projected weights of respective agitator panels  42   a ,  42   b ,  42   c  (i.e. Panels A, B and C, respectively) for cheese process vats of the present invention having differing lengths and respective vat capacities of from 30,000 to 60,000 lbs. of fluid milk and projected surface areas A, B and C for respective planes  43   a ,  43   b ,  43   c  passing through of respective agitator panels  42   a ,  42   b ,  42   c  and ending at the distal edges  45   a ,  45   b ,  45   c  of each of a series of respective agitator panels  42   a ,  42   b ,  42   c  for such cheese process vats. In each case, the surface areas and the weight of the respective opposing agitator panels are substantially balanced. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Examples of substantially balanced agitator shaft assemblies. 
               
               
                   
               
             
            
               
                 Weight 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                 Panels 
                   
                   
               
               
                   
                   
                   
                   
                 Panels 
                   
                 A + C 
                 Panel B 
               
               
                 Vat Capacity 
                 Panel A 
                 Panel B 
                 Panel C 
                 A + C 
                 TOTAL 
                 (% of 
                 (% of 
               
               
                 (lbs. of milk) 
                 (lbs) 
                 (lbs) 
                 (lbs) 
                 (lbs) 
                 (lbs) 
                 total) 
                 total) 
                 Variance 
               
               
                   
               
               
                 30,000 
                 80.976 
                 106.133 
                 79.176 
                 160.152 
                 266.285 
                 60.14% 
                 39.86% 
                 20.29% 
               
               
                 35,000 
                 83.806 
                 111.793 
                 82.006 
                 165.812 
                 277.605 
                 59.73% 
                 40.27% 
                 19.46% 
               
               
                 40,000 
                 86.636 
                 117.453 
                 84.836 
                 171.472 
                 288.925 
                 59.35% 
                 40.65% 
                 18.70% 
               
               
                 45,000 
                 89.466 
                 123.113 
                 87.666 
                 177.132 
                 300.245 
                 59.00% 
                 41.00% 
                 17.99% 
               
               
                 50,000 
                 92.296 
                 128.773 
                 90.496 
                 182.792 
                 311.565 
                 58.67% 
                 41.33% 
                 17.34% 
               
               
                 55,000 
                 95.126 
                 134.433 
                 93.326 
                 188.452 
                 322.885 
                 58.37% 
                 41.63% 
                 16.73% 
               
               
                 60,000 
                 97.956 
                 140.093 
                 96.156 
                 194.112 
                 334.205 
                 58.08% 
                 41.92% 
                 16.16% 
               
               
                   
               
            
           
           
               
            
               
                 Area 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                 Panels 
                   
                   
               
               
                   
                   
                   
                   
                 Panels 
                   
                 A + C 
                 Panel B 
               
               
                 Vat Capacity 
                 Panel A 
                 Panel B 
                 Panel C 
                 A + C 
                 TOTAL 
                 (% of 
                 (% of 
               
               
                 (lbs. of milk) 
                 (in. 2 ) 
                 (in. 2 ) 
                 (in. 2 ) 
                 (in. 2 ) 
                 (in. 2 ) 
                 total) 
                 total) 
                 Variance 
               
               
                   
               
               
                 30,000 
                 1521.371 
                 2324.271 
                 1521.371 
                 3042.742 
                 5367.013 
                 56.69% 
                 43.31% 
                 13.39% 
               
               
                 35,000 
                 1708.634 
                 2698.798 
                 1708.634 
                 3417.268 
                 6116.066 
                 55.87% 
                 44.13% 
                 11.75% 
               
               
                 40,000 
                 1895.898 
                 3073.325 
                 1895.898 
                 3791.796 
                 6865.121 
                 55.23% 
                 44.77% 
                 10.47% 
               
               
                 45,000 
                 2083.161 
                 3447.85 
                 2083.161 
                 4166.322 
                 7614.172 
                 54.72% 
                 45.28% 
                 9.44% 
               
               
                 50,000 
                 2270.425 
                 3822.379 
                 2270.425 
                 4540.85 
                 8363.229 
                 54.30% 
                 45.70% 
                 8.59% 
               
               
                 55,000 
                 2457.688 
                 4196.906 
                 2457.688 
                 4915.376 
                 9112.282 
                 53.94% 
                 46.06% 
                 7.88% 
               
               
                 60,000 
                 2644.952 
                 4571.433 
                 2644.952 
                 5289.904 
                 9861.337 
                 53.64% 
                 46.36% 
                 7.29% 
               
               
                   
               
            
           
         
       
     
     Additionally, as previously mentioned, substantially balanced agitator shaft assemblies are highly desirable as the energy required to rotate the agitator shaft assembly is continuous and relatively uniform as opposed to intermittent and pulsing. A continuous and uniform load of this type is more efficient than an intermittent and pulsing load and is less detrimental to electric motors, AC frequency converters, gear reducers, bearings, couplings, seals, welded joints of the agitator shaft assembly components and the like. Minimizing wear on these motors, converters, parts and the like translates into less downtime and lower maintenance costs. 
     In preferred embodiments of the present invention, the agitator shaft assemblies of the cheese process vats will have substantially balanced weight and/or surface area distributions with respect to the opposing agitator panels of the present invention. In preferred embodiments of the present invention, the weight of the center panel  42   b  will be from about 40 to about 60% of the weight of the total combined weight of all the panels  42   a ,  42   b ,  42   c  of the agitator shaft assembly, and the surface area B for plane  43   b , which passes through of agitator panel  42   b  and ends at the distal edges  45   b  of each of center panel  42   b , will be from about 40 to about 60% of the total combined surface area (A, B and C combined) for planes  43   a ,  43   b ,  43   c  passing through of respective agitator panels  42   a ,  42   b ,  42   c  and ending at the distal edges  45   a ,  45   b ,  45   c  of each of the respective agitator panels  42   a ,  42   b ,  42   c  of the respective agitator shaft assembly. Similarly, the combined weight of the outer agitator panels  42   a ,  42   c  will be from about 40 to about 60% of the weight of the total combined weight of all the agitator panels  42   a ,  42   b ,  42   c  of the agitator shaft assembly, and the combined surface areas (A and C combined) for planes  43   a ,  43   c  passing through of respective agitator panels  42   a ,  42   c  and ending at the distal edges  45   a ,  45   c  of respective agitator panels  42   a ,  42   c  will be from about 40 to about 60% of the total combined surface areas (A, B and C combined) for respective planes  43   a ,  43   b ,  43   c  passing through respective agitator panels  42   a ,  42   b ,  42   c  and ending at the distal edges  45   a ,  45   b ,  45   c  of each of the series of respective agitator panels  42   a ,  42   b ,  42   c  of the agitator shaft assembly. 
     The present invention preferably includes disk-like collars  76  that are welded to the agitator shaft  40  while the agitator shaft is external to the vat body  12 . If necessary, the agitator shaft can be straightened at that time with known methods and techniques. After installation of the straightened agitator shaft  40  to the respective ends  39 ,  41  of the vat body  12 , the blade clusters  42   a ,  42   b ,  42   c  are welded to the outer edge  78  of the disk-like collars  76 . Welding the blade clusters  42   a ,  42   b ,  42   c  to the outer edge  78  of the disk-like collars  76  virtually eliminates any agitator shaft  40  distortion caused by the heat generated during the welding process. In addition, the disk-like collar  76  is gentler on the coagulum when the agitator shaft assembly  14  rotates because there are no blunt edges are being forced through the coagulum (not shown). By reducing disturbance of the coagulum, the product yield is increased. 
     As shown in  FIGS. 2-6A , the cheese process vat  10  of  FIGS. 1-3  preferably includes one or more injection nozzle assembly  60  interconnected to the vat body  12  at fluid transfer ports  70 , preferably at least one injection nozzle assembly for every 44″ of running vat body length, but where the injection nozzle assemblies  60  are not less than 2″ apart, to inject a rennet solution  62  or other additive solution (i.e. aqueous calcium, coloring agent or the like) into the fluid milk  73  (see in phantom in  FIG. 6A ) located in the interior  28  of the vat body  12 . The objective in determining the number and spacing of the injection nozzle assemblies  60  is to get an even distribution of rennet solution without injecting the rennet solution too quickly. The injection nozzle assembly  60  (see  FIG. 5 ) includes a supply tube  64 , which communicates with the fluid transfer line  32 , and an injection nozzle  66  having a nozzle opening  68 . Rennet is optionally diluted in water or another aqueous medium in a mixing container  30  (see  FIG. 11A ). Then the resulting rennet solution is preferably pumped by a pump “p” (see  FIG. 1 ) or otherwise drawn into a fluid transfer line  32  from the mixing container. In preferred embodiments, the pump “p” will be a centrifugal pump, a positive displacement pump or the like, most preferably a centrifugal pump. Alternately, it will be appreciated that the mixed additive solution (i.e. the rennet solution) can be premixed and then poured or otherwise delivered into the mixing container  30 . The fluid transfer line  32  communicates with a supply tube  64  that is part of each of the respective injection nozzle assemblies  60 . From the respective supply tubes  64 , the additive solution  62  flows through the injection nozzle  66  and out the nozzle opening  68 . The narrowing in the injection nozzle  66  or at the nozzle opening  68  adjacent to the supply tube  64 , is believed to create a “venturi” effect on the additive solution  62 , so that the solution is passed out of the nozzle opening  68  in a fluid stream  63  at a higher speed than the speed at which the solution  62  travels through the fluid transfer line  32  or the tube  64 . 
     When rennet solution then enters the vat body  12  as a fluid stream  63  after passing through the injection nozzle  66  and the fluid transfer port  70 , the fluid stream  63  penetrates the surface  72  of the fluid milk  73 . In preferred embodiments of the invention, by injecting the rennet solution in a fluid stream  63  through the surface  72  down into the fluid milk  73  at multiple locations in the interior  28  of vat body  12 , rather than 1) pouring, which puts too much of the rennet solution in one place at one time or 2) spraying with a spray nozzle, which only distributes the solution onto the surface of the milk, as often done by others, the rennet solution is diluted and distributed into the fluid milk more evenly and more rapidly, which results in a better overall mixing and distribution that reduces set time and contributes to a better, more even and complete, set and resulting coagulum. The is believed to be a very significant factor in contributing to the significant improvements in the yields that the inventors have been able to obtain from cheese making operations utilizing the present cheese process vats. 
     The injection nozzle assemblies are located above the surface  72  of the fluid milk  73  to provide for a way of injecting the rennet solution through and below the surface of the fluid milk  73 , while still meeting current regulatory sanitation standards. Preferably, a rennet fluid stream  63  generated from an injection nozzle assembly  60  is injected into the surface  72  of the fluid milk  73  at a speed greater than about 40 ft/s, more preferably greater than about 60 ft/s, most preferably greater than about 80 ft/s, and the fluid stream  63  of rennet solution preferably will have a diameter no greater than about 0.25 (¼) inches at the nozzle opening  68  and a width no greater than about two (2.0) inches in diameter at the surface  72  of the fluid milk  73  and will penetrate the surface  72  of the fluid milk  73  to an immediate depth of equal to or more than about six (6.0) inches. It will be appreciated that the fluid stream  63  will enter the surface of the fluid milk preferably in a limited area having a generally circular shape, but can alternatively have a generally oval shape or another alternate shape having irregular boundaries. Typically, in the art, the water to rennet concentration of the rennet solution is from about 15:1 to about 20:1, although this dilution ratio is easily modifiable to suit any manufacturer&#39;s preference or the particular activity level of any particular rennet preparation (i.e. single, double or triple strength rennet preparations or the like). 
       FIGS. 7-9  show the preferred disk-like collar  72  in accordance with the cheese process vat of the present invention. The disk-like collar  72  has an outer edge  78  and interconnects an agitator panel  42   a ,  42   b ,  42   c  to an agitator shaft  40  of the present invention. After installation of the straightened agitator shaft  40  into the vat body  12 , the agitator panels  42   a ,  42   b ,  42   c  are welded to the outer edge  78  of the disk-like collars  76 . Welding to the outer diameter or edge  78  of the disk-like collars  76  virtually eliminates any agitator shaft distortion caused by heat generated during the welding process. 
     Referring now also to  FIGS. 6A-6B  and  10 - 15 , it will be appreciated that as long as the agitator shaft assembly  14  in a cheese process vat such as the present vat resides below the surface of the potential fluid content operating level, a seal or a system providing seals will be necessary. Since a cheese process vat is subject to regulatory scrutiny, the seal or seal system will have to be sanitary and cleanable to certain regulatory standards; and also provide a leak detection port. 
     The preferred agitator shaft assembly  14  of the present invention is illustrated in  FIGS. 6A-6B  and  10 - 15 . The agitator shaft  40  is a cylindrical agitator drive shaft that is preferably a hollow core, stainless steel agitator drive shaft. The agitator shaft  40  includes concentric flange  83  having an inner face  87 . In preferred embodiments, the inner face  87  is located on the surface of an inner face wear plate  86  that is welded onto an inner face support member  84 . The inner face wear plate  86  is preferably made of a hardenable stainless steel that wears especially well and also provides a smooth surface against which an elastomeric seal will slide especially easily, without creating undue wear to either the surface of the inner face  87  on the wear plate  86  or to the seal lip  90 . 
     The preferred shaft seal assembly  16 ,  80  of the present invention is illustrated in  FIGS. 6A-6B  and  10 - 15 . It is an adjustable seal assembly  80  including a face seal  88  having a face seal body  89  and a face seal lip  90  that extends away from the face seal body  89 . The face seal lip  90  is pre-loaded in an adjustable seal assembly subunit  82 , so there will be a pre-loaded pressure or bias between the face seal lip  90  and the inner face  87  of the agitator shaft  40 , such that a tight joint is formed in between the face seal lip  90  and the inner face wear plate  86 . The seal assembly subunit  82  preferably includes the face seal  88 , an inner seal holder  92 , a shaft seal  111 , an outer seal holder  126  and a seal retaining plate  128  screwed to the outer seal holder  126  by screws  117 . The face seal  88  is engaged with a first end  93   a  of the inner seal holder  92  and the outer seal holder  126  and the shaft seal  111  is engaged with a second end  93   b  of the inner seal holder  92 . The seal assembly subunit  82  is assembled by placing the face seal body  89  in a first groove  94  in the first end  93   a  of the inner seal holder  92  and the outer seal holder  126  is slipped over the inner seal holder  92  and the face seal  88 . The seal assembly subunit  82  also includes the shaft seal  111  that is placed in a second groove  95  in the second end  93   b  of the inner seal holder  92 . The inner seal holder  92  and the outer seal holder  126  cooperate to define a “dovetail” groove  102  that holds the face seal body  89  in place within the seal assembly subunit  82 . The dovetail groove  102  is truncated so that the space diminishes between opposing sides of the dovetail groove  102  that grip the face seal body  89  as the face seal body  89  extends toward the face seal lip  90 . The seal assembly subunit  82  also includes the seal retaining plate  128 . The seal retaining plate  128  holds the other parts of the seal assembly subunit  82  together. In preferred embodiments, the extension  124  is an inner mounting flange ring  124  that is preferably secured to an outer mounting flange ring  114 , which is preferably welded to the vat body  12 . 
     The vat body  12  preferably includes the outer mounting flange ring  114  that is welded to the vat body  12  and the inner mounting flange ring  124  that is fastened by a plurality of outer screws  116  that cooperate to secure the inner mounting flange ring  124  to the outer mounting flange ring  114 . The seal assembly subunit  82  is fastened to the inner mounting flange ring  124  preferably by a plurality of nuts  119  and studs  118  that cooperate to secure the seal assembly subunit  82  to the inner mounting flange ring  124  when the plurality of studs  118  are screwed into reciprocally threaded stud receiving openings in the inner mounting flange ring  124  and the nuts  119  are then threaded on to reciprocally threaded ends of the studs  118 ′ to hold the subunit  82  in place on the second end  41  of the vat body  12 . It will be appreciated that the respective studs  118  and nuts  119  work together to fasten the respective parts of the cheese process vat  10  together, and that the respective screws  116 ,  117  similarly fastens such parts together, but that any number of other fasteners such as bolts (not shown), screws (not shown), a combination of standoffs and nuts, a diverse combination of such fasteners and the like may be used in the place of the combination of the respective studs  118  and nuts  119  or screws  116 ,  117  to fasten the respective parts of the cheese process vat  10  together in alternate embodiments and that the present invention broadly encompasses the use of any suitable fasteners that can be employed to secure the respective parts of the present cheese process vat together. 
     The preferred cheese process vat  10  of the present invention includes a pair of o-rings  127 ,  129  preferably made from a sanitary rubber product that will provide an effective seal for joints between the inner and outer mounting flange rings  124 ,  114  and the inner mounting flange ring  124  and the outer seal holder  126 . The first o-ring  127  is seated in between a joint formed between the outer mounting flange ring  114  and the inner mounting flange ring  124  and the second o-ring  129  is seated in between a joint formed between the inner mounting flange ring  124  and the outer seal holder  126 . The first and second o-rings  127 ,  129  create a seal to prevent the contents of the vat body  12  (not shown) from leaking through the respective joints to create unsanitary conditions. 
     When the seal assembly subunit  82  is in place, the combination of the face seal  88 , the inner seal holder  92 , the shaft seal  111  and the agitator drive shaft  40  of the cheese process vat  10  define a seal chamber  106  that has an fluid conduit channel  108  that communicates with an external cleaning solution inlet  110  that doubles as the leak detection port  110 . A portion of the fluid conduit channel  108  is defined by the inner seal holder  92  (see  FIG. 14 ) and it is extended to interconnect with the cleaning solution inlet/leak detection port  110 . 
     The seal chamber  106  doubles as a CIP chamber  106  to provide a passageway for cleaning/sanitizing solution fluids to pass into the interior  28  of the vat body  12  in a manner indicated by the arrows shown in  FIG. 11B . The cleaning/sanitizing solution which enters into the seal chamber  106  from the fluid conduit channel  108  that interconnects the seal chamber  106  to the cleaning solution inlet  110 , which will be discussed in detail below. The seal chamber  106  is bordered on one side by a shaft seal  111  having a shaft seal body  112  and a shaft seal lip  113  and on the other side by the face seal  88 . The face seal lip  90  and the shaft seal lip  113  are partially concave wing structures designed and configured to cooperate with the respective seal body to which the respective wing structure is attached to act as check valves to prevent fluid from passing thru the joint sealed by a wing structure that faces inward. For example, the face seal lip  90  faces outward against the inner face  87  with respect to fluid traveling in the direction of the face seal lip  90  from the seal chamber  106 , but inward with respect to fluid traveling in the direction of the face seal lip  90  from the interior  28  of the vat body  12 , so that the face seal lip  90  acts as a check valve to prevent fluid from leaving the interior  28  to enter the seal chamber  106  via any separation between the face seal lip  113  and the inner face  87 , because the flow of fluid from the interior  28  toward the facing face seal lip  90 , which faces inward toward the interior  28  or with respect to the interior  28 , and forces the face seal lip  90  against the inner face  87 , thereby biasing the face seal lip  90  even more against the inner face  87  during cheese making operations; and the shaft seal lip  113  faces inward with respect to the seal chamber  106  and therefore prevent fluid from leaving the seal chamber  106  via any separation between the shaft seal lip  113  and the agitator shaft  40 , because the flow of fluid toward the inward facing shaft seal lip  113  forces the shaft seal lip  113  against the agitator shaft  40 , thereby biasing the shaft seal lip  113  even more against the agitator shaft  40  during clean-in-place operations. Because the respective seals  88 ,  111  are designed and configured to act as check valves, as discussed above, fluids are expected to pass in only one direction only through joints blocked by the respective seals. The face seal  88  and the shaft seal  111  may be made of any suitable sanitary rubber product that is effective for the intended use. These products/materials include but are not limited to sanitary rubber products that are available in the market, such as VITON (FKM Fluorocarbon Rubber, Vinylidene fluoride-hexafluoropropylene), NITRILE RUBBER (NBR, Acrylonitrile-Butadiene Rubber), HNBR (Hydrogenated Nitrile), SBR (Styrene-Butadiene Rubber), EPDM (Ethylene Propylene Rubber), Chloroprene and the like. The rubber material must be certified to have passed the tests outlined in a document available from 3-A Sanitary Standards, Inc., entitled 3- A Sanitary Standards for Multiple - Use Rubber and Rubber - Like Materials Used as Product Contact Surfaces in Dairy Equipment , Number 18-03, published and available for purchase on the World Wide Web at http://3-a.org/, August, 1999. 
     In preferred embodiments, a portion of the seal assembly  16 ,  80  is preassembled. This preassembled seal assembly subunit  82  preferably includes an inner seal holder  92 , a face seal  88 , a shaft seal  111 , an outer seal holder  126  and a seal retaining plate  128 . Once assembled, the preassembled seal assembly subunit  82  can be slid onto the agitator shaft  40 , into an opening in the center of the inner flange ring  124  and onto studs  118  having preferably a tubular spacer  120  and shims  112  and then secured with nuts  119 . 
     Turning now with specificity to  FIG. 11A , when the interior  28  of the vat body  12  is filled with fluid milk (not shown), the fluid milk applies pressure to the face seal lip  90  that acts as a check valve with respect to fluid flowing from the interior  28  of the vat body  12 , unless the face seal  88  fails. The pressure, indicate by the arrows shown in  FIG. 11A , forces the face seal lip  90  against the inner face  87  on the inner face wear plate  86 , so that the contents of the vat body  12  (not shown) cannot get into the seal chamber  106 . The seal assembly  80  of the present invention also aids in detecting leaks of such fluid from the interior  28  into the seal chamber  106 , because such leaks, which can only occur if the face seal  88  fails, enable fluid to travel into the seal chamber  106  from where it can flow down through the fluid conduit channel  108  and out of the vat  10  via the cleaning solution inlet/leak detection port  110 . While in use, for instance the face seal lip  90  is positioned so that any leakage of milk or whey into the seal chamber  106  from the interior  28 , will flow through the seal chamber  106 , into the fluid conduit channel  108 , and out of the vat  10  via the cleaning solution inlet/leak detection port  110 , and onto the floor of the facility (see drops from cleaning solution inlet  110 ), providing a visual indicator to the operator that maintenance is necessary. 
     In order to clean the cheese process vat  10  of the present invention, cleaning solutions are pumped into the cheese process vat at various clean-in-place (CIP) ports  34  (See also  FIG. 1 ), which enable the cleaning solution to flow directly into the interior  28  of the vat body  12  from above. The cheese process vat  10  is also equipped with two or more additional spray devices (not shown) that are intended to automatically clean the interior  28  of the vat body  12 . Simultaneous, a supply port (not shown) near one end of the agitator shaft  40 , proximate an agitator shaft bearing (not shown), can direct further cleaning solution at agitator shaft bearing. An additional supply port, the cleaning solution inlet  110  and channel  108  permit the direction of cleaning solution into the seal chamber  106  to clean parts of the shaft seal assembly  80 , which will be further discussed in detail below. 
     Now referring with further specificity to  FIGS. 11  B and  12 , when the interior  28  of the vat body  12  is being cleaned via the overhead cleaning ports  34 , cleaning solution is also pumped into the seal chamber  106  through the cleaning solution inlet  110  and the channel  108 . The face seal lip  90  is angled away from the seal chamber  106  and will be forced away from the inner face wear plate  86 , if the solution is pumped into the seal chamber  106  under sufficient pressure to force the face seal lip  90  away from the inner face wear plate  86 , thus cleaning the seal chamber  106  and the backside of the of the face seal lip  90  and the inner face wear plate  86 . The cleaning solution that flows into the seal chamber  106  towards the shaft seal  111  will force the shaft seal lip  113  against the agitator shaft  40 , thereby creating a tighter seal and preventing cleaning solution from leaking past the shaft seal  111 . The cleaning solution that passes past the face seal lip  90  travels into the interior  28  of the vat body  12  to join with cleaning fluid the flows into the interior  28  of the vat body  12  from the overhead cleaning ports  34 . Typically the cleaning solution is disposed of through a drainage port  22  (See  FIG. 6A ), secured to the vat body  12 . The inside diameter of the drain (not shown) is tangent to the lowest surface of the vat  10 , and the vat is intentionally canted slightly toward the drainage port so that liquid will not pool inside the vat  10 . 
     In preferred embodiments, both the shaft seal  111  and the face seal  88  are captivated in the seal assembly subunit  82  in such a way that there is a pre-determined amount of pressure on the shaft seal body  112  and the face seal body  89 , so that milk, whey or cleaning solution cannot wick into the joint formed between these two elastomeric components and the respective opposing surfaces on the inner seal holder  92 , outer seal holder  126  and the seal retaining plate  128 , respectively. 
     The amount of force exerted on the face seal lip  90  may be adjusted without having to enter the interior  28  of the vat body  12 . On each stud  118  is a tubular spacer  120 . The tubular spacers  120  are machined to a length that will create a pre-determined compression on the face seal lip  90 . Preferably, on each stud  118  there will also be at least one C-shaped shim  122 . In the present embodiment shown in  FIGS. 10-12 , there are two C-shaped shims, but it will be appreciated that there could be more, perhaps three, four, five, six or more shims to provide greater flexibility for adjusting the shaft seal assembly  80 . To adjust the pressure on the face seal lip  90  when forced against the inner face  87 , the user simply loosens the nuts  119  on the studs  118 , so that at least one shim  122  can be removed from each of the studs  118  and then the respective nuts  119  can be retightened. The removable shims  122  provide a way to increase pressure on seal lip  90 . The shims are preferably C-shaped so they can easily be pulled out from under the outer seal holder  126  so that the nuts  119  may be re-tightened without having to remove the nuts  119  and the seal assembly subunit  82  to remove the shims  122 . The number and/or thickness of shims  122  are fully customizable to create numerous tightening increments and possibilities. It will also be appreciate that other types of shims that have either an open side or not may be used in alternate embodiments of the present invention without departing from the scope of the present invention. 
     Now also referring with specificity to  FIG. 13 , which illustrates a reoriented adjustable shaft seal assembly  80 ′ of the present invention in which the seal assembly subunit  82 ′ has been adjusted following the removal of the shims  122 , shown in the prior Figures, and the seal assembly subunit  82 ′ is positioned closer to the flange  83  to increase the compression of the face seal lip  90 . As compared to the seal assembly subunit  82 , shown in FIGS.  10  and  11 A-B, the seal assembly subunit  82  of  FIG. 13  has been adjusted by the removal of two shims  122  on each stud  118 . Once the shims  122  have been removed, the nuts  119 , can be loosened to facilitate the removal of the respective shims, and the seal assembly subunit  82 , the face seal  88  and the face seal body  89 , held tightly within the seal assembly subunit  82 , can be moved forward toward the concentric flange  83  and the inner face  87 , a small distance. This movement allows the face seal lip  90  to be forced even more against the inner face  87 , so that a first distance “X”, between the face seal body  89  and the inner face  87 , shown in  FIGS. 11A and 11B , is diminished from the first distance to a second distance “B”, shown in  FIG. 13 . The distance is diminished uniformly, thereby uniformly increasing the pressure on the face seal  88  and the inner face wear plate  86 . 
       FIG. 14  illustrates a preferred inner seal holder  92  that partially defines the seal chamber  106  as shown in  FIG. 10 . The inner seal holder  92  has a cylindrical body  96  having a first edge  98  and a second edge  100 . The first edge  98  includes a first groove  94 . As shown in  FIG. 10 , the inner portion of the first groove  94  mates with a portion of the outer seal holder  126  to form a dovetail groove  102  in which the face seal body  89  of the face seal  88  is secured. The dovetail groove  102  is sized and configured to reflect the parameters of the face seal body  89 , so that the face seal body  89  is only moderately compressed when the face seal  88  is placed in the first groove of the inner seal holder  92  and the outer seal holder  126  is forced over the face seal  88  and the inner seal holder  92 . The second edge  100  of the inner seal holder  92  has a second groove  104  in which the shaft seal body  112  will be engaged. As also shown in  FIG. 10 , the shaft seal lip  113  is positioned in the second groove  104  in such a way the shaft seal body  112  is moderately compressed when the seal retaining plate  128  is tightened against the outer seal holder  126 , the shims  122 , the tubular spacers  120  and the inner face mounting flange  124 . 
       FIG. 15  is an end view of the second end  41  of the cheese process vat  10 , showing an external portion of the shaft seal assembly  80  of  FIGS. 10-12  showing a preferred arrangement of studs  118  and nuts  119  and screws  116 ,  117 . This screw arrangement provides for a uniform tightening along the outer diameter of the inner mounting flange ring  124  and the stud/nut arrangement provides for a uniform tightening along the outer diameter of the seal assembly subunit  82 , although numerous other arrangements may be used. 
     EXAMPLE 1 
     Performance Testing 
     Testing whey from cheese making operations for remaining fat content in the whey is one of the most common tests used to compare cheese making efficiently, in different vats in cheese plants throughout the industry. The results are often used as a measure of performance. By testing the amount of fat in the whey, cheese plants can predict the performance of the cheese process vats. It is desirable to have as low a fat content in the whey as possible for each type of cheese. 
     Performance test results for whey from a single agitator shaft vat of the present invention were compared with test results for a well known dual agitator shaft vat. 
     The test procedure begins by collecting a small whey sample from the cheese process vat during the “predraw/settle” step. This sample of approximately 4 to 6 ounces is sent to a commercial laboratory where the sample is tested with a standard infrared spectroscopy test for fat quantity as a percentage fluid volume. The method used is a standard infrared analysis of the sample for the amount of fat, protein, lactose and total solids in the whey. A low fat content in the whey is generally believed to correlate with a higher cheese yield, which is clearly desirable to plant operators. The Whey Fat Test Results generated in this procedure are shown below in Table 1. The testing evaluation shows that the cheese process vat of the present invention is very competitive with the known dual vat system tested that is one of the more popular cheese process vats in the industry. In these test results, the cheese process vat of the present invention was lower in whey fats on 10 of the 12 days that were comparison test. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 The Percentage of Fat in Whey Determinations for 
               
               
                 Performance Testing in Example 1. 
               
               
                 Percent of Fat in Whey 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Present Single Agitator 
                 Dual Agitator Shaft 
               
               
                   
                 Day Tested 
                 Shaft Vat 
                 Vat 
               
               
                   
                   
               
               
                   
                 Day 1 
                 0.274% 
                  0.28% 
               
               
                   
                 Day 2 
                 0.302% 
                 0.289% 
               
               
                   
                 Day 3 
                 0.288% 
                 0.299% 
               
               
                   
                 Day 4 
                 0.263% 
                 0.274% 
               
               
                   
                 Day 5 
                  0.26% 
                  0.32% 
               
               
                   
                 Day 6 
                 0.253% 
                 0.266% 
               
               
                   
                 Day 7 
                 0.232% 
                 0.235% 
               
               
                   
                 Day 8 
                 0.232% 
                 0.224% 
               
               
                   
                 Day 9 
                 0.178% 
                 0.219% 
               
               
                   
                 Day 10 
                 0.198% 
                 0.261% 
               
               
                   
                 Day 11 
                 0.246% 
                 0.252% 
               
               
                   
                 Day 12 
                 0.232% 
                 0.236% 
               
               
                   
                 Ave.(mean) 
                 0.247% 
                 0.263% 
               
               
                   
                   
               
            
           
         
       
     
     It will be appreciated that the foregoing is only illustrative of the broad principles of the present invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described herein, the details may be changed without departing from the intended scope of the invention, which is defined by the attached claims.