Abstract:
A pump assembly for use within a high pressure pumping system includes housing, a head and a base. The housing contains at least one centrifugal pump stage. The head and base are attached to the housing with corresponding internal threaded connections. The head and base are further retained to the housing with corresponding external flanged connections. The external flanged connections provide redundant connections that reduce the risk of separation between the housing and the head and base.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to the field of industrial pumping systems, and more particularly to pump systems used in high-pressure applications. 
       BACKGROUND 
       [0002]    High pressure pumping systems typically include a pump assembly that is driven by an electric motor. In many designs, the pump assembly is configured as a multi-stage centrifugal pump that includes a number of impellers and diffuses stacked within a tubular housing. When energized, the motor rotates a shaft that is directly or indirectly connected to the impellers and other moving parts within the pump assembly. The rotation of the impellers imparts kinetic energy to the pumped fluid, a portion of which is converted to pressure-head as the fluid passes through the diffusers. 
         [0003]    As shown in the PRIOR ART drawing of  FIG. 1 , a typical pump assembly  10  is constructed by stacking multiple turbomachine stages  12  within a tubular housing  14  that is capped on one end by a “head”  16  and on the opposing end by a “base”  18 . The base  18  is usually used to secure the pump assembly  10  to an intake, motor protector or motor. The head  16  is designed to connect the pump assembly to another pump, the production tubing or some other intervening component. 
         [0004]    Like other prior art designs, the housing  14  is connected to the head  16  and base  18  with a threaded engagement. Significantly, the engagement is created through the use of threads on the inner diameter (“ID”) of the housing  14  with the threads on the outer diameter (“OD”) of the head  16  and base  18 . In this configuration, the head  16  and base  18  can be made to be flush with outer diameter of the housing  14 . To contain the pumped fluid, o-ring seals  20  have been used in positions external to the threaded connections between the housing  14  and the head  16  and base  18 . 
         [0005]    While generally effective for lower-pressure applications, the prior art approach for connecting the pump housing to the head and base can be unsatisfactory in high-pressure installations. As the pressure of the fluid within the housing  14  increases, the housing  14  may expand, thereby decreasing the extent of engagement between housing  14  and the head  16  and base  18 . If the threaded connections between the housing  14  and the head  16  and base  18  are compromised, the pump assembly  10  may operate at decreased efficiency or fail entirely and allow the head  16  and base  18  to separate from the housing  14 . Accordingly, there is a need for an improved pump design that provides for increased resistance to failure at elevated working pressures. 
       SUMMARY OF THE INVENTION 
       [0006]    In preferred embodiments, the present invention includes a pump assembly for use within a high pressure pumping system. In a first preferred embodiment, the pump assembly includes a housing, a head and a base. The housing contains at least one centrifugal pump stage. The head and base are attached to the housing with corresponding internal threaded connections. The head and base are further connected to the housing with corresponding external flanged connections. The external flanged connections provide redundant connections that reduce the risk of failure between the housing and the head and base. 
         [0007]    In a second preferred embodiment, the invention includes a modular pump assembly that includes a first pump module connected to a second pump module. The first pump module includes a first housing that has a first pair of external flanges located at opposing ends of the first housing. The first pump module further includes a head enclosed within the first housing and a base enclosed within the first housing. Similarly, the second pump module includes a second housing that has a second pair of external flanges located at opposing ends of the second housing. The second pump module includes a head enclosed within the second housing and a base enclosed within the second housing. The second pump module is connected to the first pump module by securing one of the second pair of external flanges is connected to one of the first pair of external flanges. 
         [0008]    Thus, the preferred embodiments include pump assemblies that include the use of external flanged connections to back-up the internal threaded connections between the pump head, base and housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a cross-sectional view of a PRIOR ART pump assembly. 
           [0010]      FIG. 2  is a depiction of a pumping system constructed in accordance with a preferred embodiment of the present invention in a surface-mounted application. 
           [0011]      FIG. 3  is a front perspective view of a pumping system constructed in accordance with a preferred embodiment of the present invention in a subterranean application. 
           [0012]      FIG. 4  is a cross-sectional view of a first preferred embodiment of the pump assembly from the pumping systems of  FIG. 2  or  3 . 
           [0013]      FIG. 5  is a cross-sectional view of a second preferred embodiment of the pump assembly from the pumping systems of  FIG. 2  or  3 . 
           [0014]      FIG. 6  is a cross-sectional view of the two of the second preferred embodiment of the pump assemblies of  FIG. 5  ganged together. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    In accordance with a preferred embodiment of the present invention,  FIG. 2  shows a side view of a pumping system  100 . As shown in  FIG. 2 , the pumping system  100  is configured as a surface pumping system supported on the surface  102  by a support rack  104 . The surface-mounted pumping system  100  preferably includes a motor  106 , a pump assembly  108  and an intake  110 . The pumping system  100  further includes an intake manifold  112  and a discharge manifold  114  that carry fluid to and from the surface pumping system  100 , respectively. 
         [0016]    Turning now also to  FIG. 3 , shown therein is a perspective view of the pumping system  100  in a subterranean application. As shown in  FIG. 3 , the pumping system  100  is located within a casing  116  of an underground wellbore, which is drilled for the production of a fluid such as water or petroleum. As used herein, the term “petroleum” refers broadly to all mineral hydrocarbons, such as crude oil, gas and combinations of oil and gas. 
         [0017]    The pumping system  100  of  FIG. 3  preferably includes a seal section  118  and a screened intake  120  between the motor  106  and pump assembly  108 . The seal section  118  protects the motor  106  from thrust produced by the pump assembly  108  and the unwanted ingress of contaminated fluids from the wellbore environment and accommodates the expansion of lubricants within the motor  106 . The screened intake  120  provides an inlet through which fluids can pass from the wellbore into the pump assembly  108 . In this environment, the pumping system  100  also preferably includes production tubing  122  that provides a conduit through which fluids are pumped from the pump assembly  108  to the surface  102 . 
         [0018]    In a preferred embodiment, the motor  106  is an electrical motor that receives its power from a surface-based source. Generally, the motor  106  converts electrical energy into mechanical energy, which is transmitted to the pump assembly  108  through one or more shafts (not shown in  FIG. 2  or  3 ). In a particularly preferred embodiment, the pump assembly  108  is a multi-stage centrifugal pump that uses two or more impellers and diffusers to convert mechanical energy into pressure head. In an alternative embodiment, the pump assembly  108  is a progressive cavity (PC) pump that moves wellbore fluids with one or more screws or pistons. 
         [0019]    Turning to  FIG. 4 , shown therein is a cross-sectional depiction of the pump assembly  108  constructed in accordance with a first preferred embodiment. The pump assembly  108  preferably includes a housing  124 , a base  126  and a head  128 . The base  126  is preferably configured for attachment to the intake  110  or screened intake  120 , depending on the environment in which the pump assembly  108  is used. The head  128  is preferably configured for attachment to the discharge manifold  114  or the production tubing  122 , again depending on the environment in which the pumping system  100  is used. The head  128  can be used alternatively or additionally as an bearing support that is configured for threaded engagement with the housing  124 . The housing  124  is preferably constructed as a tubular, substantially cylindrical member that contains at least one turbomachinery stage  130 . Each turbomachinery stage  130  preferably includes an impeller  132  and a diffuser  134 . Each impeller  132  is connected to and configured for rotation with a shaft  136  that extends through the pump assembly  108 . 
         [0020]    The head  128  includes exterior head threads  138  that mate with interior head threads  140  on the inside of the housing  124 . Similarly, the base  126  includes exterior base threads  142  that mate with interior base threads  144  on the interior of the housing  124 . In this way, the head  128  and base  126  can be screwed into the housing  124  to place a compressive load on the diffuser  134  portion of turbomachinery stages  130 . The compressive load prevents the diffuser  134  from spinning within the housing  124 . The head  128  and base  126  each further include one or more o-ring seals  146  to prevent the passage of fluid through the threaded connection. 
         [0021]    The pump assembly  108  further includes a base flange  148  on the base  126 , an upstream flange  150  on the housing  124 , a downstream flange  152  on the housing  124  and a head flange  154  on the head  128  (collectively, “exterior flanges  148 ,  150 ,  152  and  156 ”). The base flange  148  is preferably slip-fit up to the load shoulder on the exterior surface of the base  126 . The upstream flange  150  and downstream flange  152  are preferably shrink-fit then welded to the exterior surface of opposing upstream and downstream ends of the housing  124 . Alternatively, the upstream flange  150  and downstream flange  152  can be formed with the housing  124  in unitary construction from a single piece of material. The head flange  154  is preferably welded to the outside of the head  128 . Each of the base flange  148 , upstream flange  150 , downstream flange  152  and head flange  154  are preferably configured as circular flanges that each contain a series of aligned bolt holes  156 . Bolts  158  or other suitable fasteners can be placed through the bolts holes  156  to provide back-up retaining force between the base  126  and housing  124  and between the housing  124  and head  128 . 
         [0022]    In this way, the pump assembly  108  includes both exterior flanged and interior threaded connections between the housing  124  and the each of the base  126  and head  128 . The use of interior threaded connections and exterior flanged connections provides a robust pump assembly  108  that is capable of performing at pressures of up to about 10,000 psi. 
         [0023]    Turning to  FIGS. 5 and 6 , shown therein is a side cross-sectional view of a second preferred embodiment of the pump assembly  108 . In the second preferred embodiment, the head  128  and base  126  are secured within the interior of the housing  124  by interior and exterior head threads  138 ,  140  and interior and exterior base threads  142 ,  144 . The housing  124  further encloses one or more centrifugal pump stages  130 . Because the head  128  and base  126  are internal to the housing  124 , the pump assembly  108  of the second preferred embodiment does not include the base flange  148  and head flange  154 . Instead, the pump assembly  108  includes only the upstream flange  150  and downstream flange  152  connected to the exterior of the housing  124  at the opposing upstream and downstream ends. In particularly preferred embodiments, the upstream flange  150  and downstream flange  152  are welded to the exterior of the housing  124 . 
         [0024]    As illustrated in  FIG. 6 , the second preferred embodiment of the pump assembly is particularly well suited for use in a modular pumping system in which multiple pumps are connected together. The use of the exterior flanges  150 ,  152  retains the axial loads produced between and by adjacent pump assemblies  108 . The internal forces within the pump assembly  108  are retained by the head  128  and base  126 , through the interior and exterior head threads  138 ,  140  and interior and exterior base threads  142 ,  144 . The use of external flanges  150 ,  152  increases the pump connection joint contact area and, provides back-up to the internal threaded connections between the housing  124  and the head  128  and base  126 . The exterior flanges  150 ,  152  on the opposing terminal ends of the concatenated pump assemblies  108  can be used for connection to the intake manifold  112 , discharge manifold  114 , intake  120  and/or production tubing  122 . The second preferred embodiment of the pump assembly  108  is capable of withstanding operating pressures of up to about 10,000 psi. 
         [0025]    It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functions of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. It will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems without departing from the scope and spirit of the present invention.