Abstract:
A submersible pump-motor assembly for use in dispensing petroleum from petroleum storage tanks. The pump-motor assembly of the present invention enhances the performance characteristics of the pump-motor assembly by providing greater flow area around the motor stator while maintaining the alignment of the assembly&#39;s critical pump components. Such enhanced pump performance characteristics provide the petroleum dispensing station manager using such pump-motor assemblies with greater flow rates per dispenser or, when maximum flow rates are capped, potentially greater dispensing capacity.

Description:
BACKGROUND OF THE INVENTION 
   Description of the Prior Art 
   Referring to  FIG. 1 , in petroleum dispensing stations, submersible turbine pump-motor assemblies  10  are disposed in petroleum storage tanks  12  and are used to pump petroleum  14  from the storage tank  12 , which is usually located underground, to dispensers  16 . (In  FIG. 1  only one dispenser  16  is depicted, but it should be understood that in a typical petroleum dispensing station a single pump-motor assembly  10  provides fuel to a number of dispensers  16 .) Customers dispense fuel from a dispenser  16  into their vehicles through a nozzle  18 . The typical pump-motor assembly  10  includes a turbine or centrifugal pump and an electric motor which drives the pump. The upper end of the pump-motor assembly  10  attaches to a piping assembly  22  which connects to a manifold assembly  24  which, in turn, connects to a piping network  26  to distribute petroleum from the pump-motor assembly  10  to the dispensers  16  attached to the piping network  26 . 
   Petroleum dispensing station managers, service station owners for instance, ideally want to maximize the dispensing flow rate possible for each available dispenser to increase the total potential throughput through the station. For certain petroleum products, however, the maximum dispensing flow rate per dispenser is set by government regulation, and the station manager has no incentive to achieve greater flow rates. For instance, in the U.S., the government (i.e., the E.P.A) has set an upper limit of 10 gallons/minute (“GPM”) as the maximum flow rate per dispenser for certain petroleum products such as gasoline. In such cases, the petroleum dispensing station manager seeks to achieve the alternate goal of maximizing the dispensing capacity for each piping network  26 . In other words, station managers in such cases want to maximize the number of dispensers  16  operating at the maximum flow rate and pressure for a single pump-motor assembly. The present problem with maximizing dispensing flow rates and dispensing capacity is that dispensing flow rates and dispensing capacity are limited by the flow rates achieved by present system pump-motor assemblies at a given required pressure. Much of the flow rate limitations of present pump-motor assemblies are attributable to their design. 
   In present pump-motor assemblies, it is critical that the components of the pump assembly align with the motor&#39;s drive shaft; otherwise, vibration and other misalignment forces will affect the proper performance of the pump and may eventually cause the pump to fail. Referring to  FIG. 2 , a pump-motor assembly  10  presently used by petroleum dispensing stations is depicted. The pump-motor assembly  10  includes a motor unit  30  and a pump assembly  32 . A shell  20  encases the motor unit  30  and the pump assembly components. The shell  20  performs the critical function of holding the pump assembly components in alignment with the shaft  36  of the motor unit  30 . The shell  20  is formed with an inner diameter that is relatively equal to the greatest outer diameter of the motor unit  30 . The motor unit  30  typically includes an end bell  33 , a stator  31  and a lead housing  35 . The end bell  33  and the lead housing  35  have contact points  38 ,  39 , respectively, extending therefrom. The contact points  38 ,  39  have the greatest outer diameter of the motor unit  30 . As such, when the pump-motor assembly  10  is assembled, the shell  20  contacts the motor unit  30  at the contact points  38 ,  39 . The contact between the shell  20  and the contact points  38 ,  39  keeps the motor  30  and shell  20  in alignment. The shell  20  also contacts components of the pump assembly  32 . Specifically, in the pump-motor assembly  10  depicted in  FIG. 2 , the shell  20  contacts housings  40  and diffusers  42  of the pump assembly  32 . The contact between the shell  20  and the pump-assembly components performs the critical function of keeping the pump assembly components in alignment with the motor shaft  36 . In addition to the pump-motor assembly  10  depicted in  FIG. 2 , other similar pump-motor assemblies are available on the market. Such other pump-motor assemblies might have somewhat different component configurations than the pump-motor assembly  10  depicted (i.e., the pump housing and diffuser components may be integral in some form with one another rather separate as in the pump-motor assembly  10  depicted), but they still employ the principles discussed above (e.g., use of the shell for alignment purposes). 
   In addition to the alignment interaction, the shell  20  and the motor unit  30  also form a flow path  34  between the shell  20  and the stator  31 . Petroleum pumped up through the pump-motor assembly  10  to the piping assembly  22  is pumped around the stator  31  through the flow path  34 . The area of this flow path and, consequently, the flow rate of fluid through it, is defined and restricted by the outer diameter of the stator  31  and the inner diameter of the shell  20 . As explained above, the inner diameter of the shell  20  is fixed for alignment purposes. As such, the flow path  34  defined by the stator  31  and the shell  20  is very narrow with a very small cross sectional area. It has been found that the performance characteristics of the pump-motor assembly  10  are severely degraded by the flow of fluid through such a restricted flow path  34 . 
   Accordingly, there is a need for a pump-motor assembly that maintains alignment of its pump assembly components while providing greater fluid flow around a given diameter of the assembly&#39;s motor unit stator. Further, there is a need for a pump-motor assembly that achieves greater system flow rates and allows for maximizing dispensing capacity at a given required pressure. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the present invention, a pump-motor assembly includes a motor unit, a pump assembly having components and a shell having an expanded portion in which the shell encloses the pump assembly components and the motor unit with the expanded portion disposed around the motor unit and in which the shell aligns the pump assembly components to the motor unit. The motor unit may include an end bell and a lead housing. The shell may contact the end bell, the lead housing or both. The motor unit may include a stator and, in such a case, the expanded portion of the shell may be disposed around the stator. The inner diameter of the expanded portion of the shell may be at least four inches. 
   According to another aspect of the present invention, a pump-manifold assembly includes a manifold, a pump-motor assembly and a piping assembly connecting the pump-motor assembly to the manifold. The pump-motor assembly includes a motor unit, a pump assembly having components and a shell having an expanded portion, wherein the shell encloses the pump assembly components and the motor unit with the expanded portion disposed around the motor unit and wherein the shell aligns the pump assembly components to the motor unit. The motor unit may include an end bell and a lead housing. The shell may contact the end bell, the lead housing or both. The motor unit may include a stator and, in such a case, the expanded portion of the shell may be disposed around the stator. The inner diameter of the expanded portion of the shell may be at least four inches. 
   According to a further aspect of the present invention, a petroleum distribution system for use in a petroleum dispensing station includes a petroleum storage tank; a petroleum dispenser; a pump-manifold assembly, in fluid communication with the petroleum dispenser, having a pump-motor assembly. The pump-motor assembly is disposed in the storage tank and the pump-motor assembly includes a motor unit, a pump assembly having components and a shell having an expanded portion, wherein the shell encloses the pump assembly components and the motor unit with the expanded portion disposed around the motor unit and wherein the shell aligns the pump assembly components to the motor unit. The motor unit may include an end bell and a lead housing. The shell may contact the end bell, the lead housing or both. The motor unit may include a stator and, in such a case, the expanded portion of the shell may be disposed around the stator. The inner diameter of the expanded portion of the shell may be at least four inches. 
   According to another aspect of the present invention, a method for increasing fluid dispensing flow rate in a petroleum distribution system for use in a petroleum dispensing station includes providing a petroleum distribution system including a petroleum storage tank; a petroleum dispenser; a pump-manifold assembly, in fluid communication with the petroleum dispenser, having a pump-motor assembly and energizing the pump-motor assembly to pressurize the petroleum distribution system. The pump-motor assembly is disposed in the storage tank and the pump-motor assembly includes a motor unit, a pump assembly having components, and a shell having an expanded portion, wherein the shell encloses the pump assembly components and the motor unit with the expanded portion disposed around the motor unit and wherein the shell aligns the pump assembly components to the motor unit. 
   According to another aspect of the present invention, a method for increasing dispensing capacity in a petroleum distribution system for use in a petroleum dispensing station where the maximum dispensing flow rate is capped includes providing a capped maximum dispensing flow rate; providing a petroleum distribution system including a petroleum storage tank; a petroleum dispenser; a pump-manifold assembly, in fluid communication with the petroleum dispenser, having a pump-motor assembly and energizing the pump-motor assembly to pressurize the petroleum distribution system. The pump-motor assembly is disposed in the storage tank and the pump-motor assembly includes a motor unit, a pump assembly having components, and a shell having an expanded portion, wherein the shell encloses the pump assembly components and the motor unit with the expanded portion disposed around the motor unit and wherein the shell aligns the pump assembly components to the motor unit. The provided capped maximum dispensing flow rate may be ten gallons per minute. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description and accompanying drawing where: 
       FIG. 1  illustrates a petroleum distribution system incorporating a prior art pump-motor assembly; 
       FIG. 2  is a partial sectional view of a prior art pump-motor assembly; 
       FIG. 3  illustrates a petroleum distribution system incorporating a pump-motor assembly of the present invention; 
       FIG. 4  is a partial sectional view of a pump-motor assembly of the present invention; 
       FIG. 5  illustrates the performance characteristics of a two stage pump-motor assembly of the present invention versus a two stage prior art pump-motor assembly; and 
       FIG. 6  illustrates the performance characteristics of a three stage/two diffuser pump-motor assembly of the present invention versus a three stage/two diffuser prior art pump-motor assembly. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 3 and 4 , a pump-motor assembly  50  of the present invention for use in the petroleum distribution system of a petroleum dispensing station is illustrated. Referring to  FIG. 3 , the pump-motor assembly  50  is attached to the piping assembly  22  in the same or similar manner as pump-motor assembly  10  is attached to the piping assembly  22  in  FIG. 1 . Referring to  FIG. 4 , the pump-motor assembly  50  includes a motor unit  52  and a pump assembly  54  encased in a shell  56  having an expanded portion  58  between expansion points  57   a,    57   b.  The motor unit  52  includes a stator  59 , an end bell  60  attached to the stator  59  on the inlet side, a lead housing  62  attached to the stator  59  on the outlet side and a motor shaft  64  extending outward from the stator  59  and end bell  60 . The motor unit  52  may be any type of sealed electric motor used in submersible turbine pump units. The pump assembly  54  is multi-stage and centrifugal in design. The pump assembly  54  depicted in the embodiment of  FIG. 4  has two stages  66   a,    66   b,  but it should be understood that any number of stages may be used. In this embodiment, each stage  66  includes a housing  68   a,    68   b;  an impeller  70   a,    70   b;  and a diffuser  72   a,    72   b.  These components may be configured as necessary. For example, in this embodiment, the housings  68  and the diffusers  72  are separate components, but they could also be formed integral to one another in some form as well. In a preferred embodiment, the pump assembly components (i.e., the housing  68 , the impeller  70  and the diffuser  72 ) may be made of any plastic, metal or other suitable material. 
   In this embodiment, the components of the pump-motor assembly  50  are typically assembled in the following manner. The motor unit  52  is inserted in the shell  56 . In a preferred embodiment, the shell  56  is made from stainless steel but it may be made from any other suitable metal (e.g., aluminum, steel). Extending outward from the lead housing  62  is a motor plug  74  which connects to an electrical conduit disposed in the piping assembly  22  when the pump-motor assembly  50  is connected to the piping assembly  22 . Further, in this embodiment, the motor unit  52  is designed such that the end bell  60  and the lead housing  62  have contact points  76 ,  78 , respectively, and the outer diameter of each contact point  76 ,  78  is relatively equal to the inner diameter of the shell  56  such that when the motor unit  52  is inserted in the shell  56  the inner portion of the shell  56  at that point contacts the end bell  60  and the lead housing  62  at the contact points  76 ,  78 . The contact points  76 ,  78  do not have to be integral with the end bell  60  and the lead housing  62  as shown in this embodiment. For instance, in other embodiments, the end bell  60  could have a larger diameter than the lead housing  62  in which case a spacer could be placed around the lead housing  62  to accommodate for the diameter differential between the shell  56  and the lead housing  62 . The reverse, obviously, is also true. The lead housing  62  could have a larger diameter than the end bell  60  in which case a spacer could be placed around the end bell  60  to accommodate for the diameter differential between the shell  56  and the end bell  60 . 
   The contact between the shell  56  and the contact points  76 ,  78  of the motor unit  52  acts to align the shell  56  with the stator  59  and motor shaft  64 . As a result, the expanded portion  58  of the shell  56  is located between the two contact points  76 ,  78 . The motor unit  52  and the shell  56  form an annular flow path  80  between them. The flow path  80  around the stator  59  is defined by the outer surface of the stator  59  and the inner surface of the expanded portion  58  of the shell  56 . At the discharge end of the pump-motor assembly  50 , the shell  56  is crimped in along an annular recess  82  in the lead housing  62 , and a seal  84 , an o-ring in this embodiment, is seated in the annular recess  82 . The interaction between the shell  56 , the lead housing  62  and the seal  84  acts to seal the outer edge of the motor unit  52  and keep fluid flowing through the flow path  80  directed inward through channels  86  formed in the lead housing  62 . 
   With the motor unit  52  in place, the pump assembly  54  is assembled around the motor shaft  64 . In differing embodiments, the design of the pump components could be in many forms and the assembly of such components could be accomplished in various ways. In this embodiment, the pump components, and their related assembly, are as described as follows. A spacer ring  88  is inserted the end bell  60  of the motor unit  52  and the upper diffuser  72   b.  The upper stage  66   b  of the pump assembly  54  has an impeller  70   b  with a spline hub  90   b.  Assembled, the diffuser  72   b  seats over the spline hub  90   b,  and the spline hub  90   b  is disposed over the motor shaft  64  and engages a spline  65  formed on the motor shaft  64 . The housing  68   b  is disposed around the impeller  70   b.  The impeller  70   b  includes a seal extension  92   b  which interacts with a seal recess  94   b  formed in the housing  68   b  to form a dynamic seal between the impeller  70   b  and the housing  68   b  when the pump-motor assembly  50  is in operation. The components of the lower stage  66   a  of the pump assembly  54  are similar to those of the upper stage  66   b.  The outer diameters of the housings  68   a,    68   b  and the diffusers  72   a,    72   b  are relatively equal to the inner diameter of the shell  56  at that point. As such, the shell  56 , which is aligned with the stator  59  via the contact points  60 ,  62 , aligns the pump assembly components with the shaft  64  of the motor unit  52 . The assembly of the pump assembly  54  is completed by inserting a shaft spacer  96  over the end of the motor shaft and locking the components in place with a socket head capscrew  98 . A flat washer  100  and a lock washer  102  may be disposed between the shaft spacer  96  and the capscrew  98 . Assembly of the pump-motor assembly  50  is completed by inserting an end bell  104  into the shell  56 , abutting the lower stage housing  68   a,  and crimping the shell  56  around the end bell  104 . A bottom plug  106  is inserted into the end bell  104  to complete the pump-motor assembly  50 . 
   In operation, the motor unit  52  turns the motor shaft  64  which turns the pump impellers  70   a,    70   b.  The pressure differential created by the impeller rotation draws fluid into the pump-motor assembly  50  through the end bell  104 . Fluid drawn into the pump-motor assembly  50  generally follows the flow path indicated in  FIG. 4 . It should be understood that the flow through pump-motor assembly  50  is annular throughout the entire assembly and that the flow depicted is only through one side of the pump-motor assembly  50  for illustrative purposes. After passing through the end bell  104 , the drawn-in fluid is pulled up through an opening  110   a  formed in the lower housing  68   a  into the rotating lower impeller  70   a.  From the lower impeller  70   a,  the fluid passes through the lower diffuser  72   a.  From the lower diffuser  72   a,  the fluid continues through the upper stage  66   b  in a similar manner. The energized fluid leaves the pump assembly  54  and is pushed through channels  112  in the end bell  60  into the flow path  80  between the stator  59  and the expanded shell portion  58 . Once through the flow path  80 , the fluid flows through the lead housing channels  86  out of the pump-motor assembly  50  into the piping assembly  22 . 
     FIGS. 5 and 6  illustrate the improved performance of pump-motor assemblies of the present invention versus prior pump-motor assemblies, such as pump-motor assembly  10  depicted in  FIG. 2 . Referring to  FIG. 5 , curve  5 A is a pressure vs. flow curve for a pump-motor assembly with a straight shell and curve  5 B is a pressure vs. flow curve for a pump-motor assembly of the present invention having an expanded shell. For this test data, both pump-motor assemblies used the same motor unit and pump assembly components. The motor unit was a 2 hp motor, and the assembly included two impellers and two diffusers. The stator outer diameter for both systems was 3.72 inches. The inner diameter of the shell for the straight shell assembly (curve  5 A) was 3.916 inches, and the inner diameter of the shell at the expanded portion for the expanded shell assembly of the present invention (curve  5 B) was 4.000 inches. As such, the annular flow area for the straight shell assembly was 1.175 in 2 , and the annular flow area for the expanded shell assembly of the present invention was 1.698 in 2 . The expanded shell assembly, therefore, provided an increased annular flow area of approximately 45% over the straight shell assembly. 
   Curves  5 A and  5 B show the system pressure loss as the flow rate through the system is increased. The system for these tests was the pumping system which includes the pump-motor assembly, the manifold and the piping assembly which connects the pump-motor assembly to the manifold. The improved performance characteristics of the expanded shell pump-motor assembly are most evident at higher flow rates. For instance, at a flow of 90 gallons/minute through the system, the system pressure in the system using the straight shell assembly is only 5 psi (point “a”), and the system pressure for the system using the expanded shell assembly is approximately 12.5 psi (point “b”). Therefore, the system using the expanded shell pump-motor assembly had 7.5 psi greater system pressure available due to less restriction through the pump-motor assembly  50  (i.e., the pressure drop across the stator  59  was reduced by 7.5 psi at 90 GPM). 
   From a dispensing station manager&#39;s perspective, such improved pump-motor assembly pumping characteristics ultimately means greater flow rates per dispenser or, when maximum flow rates are capped, potentially greater dispensing capacity. For instance, at a set system pressure, such as 20 psi (which is the typical dispensing pressure for a dispensing station dispenser), the system using the straight shell assembly (curve  5 A) can only achieve a 60 GPM flow rate (point “c”) while the system using the expanded shell assembly of the present invention (curve  5 B) can achieve approximately a 73 GPM flow rate (point “d”)—an approximate 13 GPM greater flow rate. Where the maximum dispensing flow rate is set or regulated for a particular product, such as the E.P.A.&#39;s maximum regulated flow rate of 10 GPM per dispenser, the increased flow rate potential generated by pump-motor assembly  50  of the present invention translates into increased dispensing capacity for the dispensing station manager. For example, at a petroleum dispensing station with required dispensing pressure of 20 psi and a maximum dispenser flow rate of 10 GPM, a dispensing station manager using a prior art straight shell assembly can only use six (6) dispensers per pump-motor assembly. (Total Dispensers per Pump-Motor Assembly=Total Flow Rate+Maximum Flow Rate per Dispenser (i.e., 60 GPM/10 GPM=6 Dispensers)). On the other hand, a dispensing station manager using an expanded shell assembly of the present invention can use seven (7) dispensers per pump-motor assembly (i.e., 73 GPM/10 GPM=7.3 Dispensers). 
   This test data and similar results were also true for other pump configurations. Referring to  FIG. 6 , curve  6 A is a pressure vs. flow curve for a pump-motor assembly with a straight shell and curve  6 B is a pressure vs. flow curve for a pump-motor assembly of the present invention having an expanded shell. For this test data, both pump-motor assemblies used the same motor unit and pump assembly components as one another. The motor unit was a 2 hp motor, and the assemblies this time included three impellers and two diffusers. The motor stator and shell dimensions were the same for this test as they were for the test described above. The stator outer diameter for both systems was 3.72 inches. The inner diameter of the shell for the straight shell assembly (curve  6 A) was 3.916 inches, and the inner diameter of the shell at the expanded portion for the expanded shell assembly of the present invention (curve  6 B) was 4.000 inches. As with the assembly of the test described above, the annular flow area for the straight shell assembly was 1.175 in 2 , and the annular flow area for the expanded shell assembly of the present invention was 1.698 in 2 , giving the expanded shell assembly an increased annular flow area of approximately 45% over the straight shell assembly. 
   As with the graph described above, the curves  6 A and  6 B show the system pressure loss as the flow rate through the system is increased. The improved performance characteristics of the expanded shell pump-motor assembly are, once again, most evident at higher flow rates. For instance, at a flow rate of 90 GPM through the system, the system pressure in the system using the straight shell assembly was only about 12.5 psi (point “e”), and the system pressure for the system using the expanded shell assembly was approximately 17 psi (point “f”). Therefore, the system using the expanded shell pump-motor assembly had 4.5 psi greater system pressure available due to less restriction through the pump-motor assembly  50  (i.e., the pressure drop across the stator  59  was reduced by 4.5 psi at 90 GPM). 
   Again, from a dispensing station manager&#39;s perspective, such improved pump-motor assembly pumping characteristics ultimately means greater flow rates per dispenser or, when maximum flow rates are capped, potentially greater dispensing capacity. At the set pressure of 20 psi, the system using the straight shell assembly (curve  6 A) can only achieve an approximate 80 GPM flow rate (point “g”) while the system using the expanded shell assembly of the present invention (curve  6 B) can achieve approximately a 86 GPM flow rate (point “h”)—an approximate 6 GPM greater flow rate. 
   While the invention has been discussed in terms of certain embodiments, it should be appreciated by those of skill in the art that the invention is not so limited. The embodiments are explained herein by way of example, and there are numerous modifications, variations and other embodiments that may be employed that would still be within the scope of the present invention.