Abstract:
The disclosed invention modifies existing centrifugal pump design by replacing a compression seal with a mechanical seal and lubricant reservoir. The mechanical seal creates a sealed chamber to lubricate the rotating shaft. The rotating shaft is covered in a shaft sleeve that facilitates the flow of lubricant to and from the sealed chamber. This improvement provides independent lubrication to the centrifugal pump to protect against seal failure.

Description:
BACKGROUND 
       [0001]    The present disclosure involves a centrifugal pump  100 . The mechanism of a centrifugal pump  100  is well known to those skilled in the art. The centrifugal pump  100  is connected to a source of fluid to be transported. A rotating shaft  102  rotates an impeller  306  creating a negative pressure to pull the fluid into the centrifugal pump  100  to be discharged. 
         [0002]    The outer portion of the centrifugal pump  100  is formed by centrifugal pump housing  302  coupled to a stuffing box  202  that seals the rear of the centrifugal pump  100 . The stuffing box  202  contains a stuffing box throat  204  with a stuffing box throat aperture  210  that allows the rotating shaft  102  to be inserted into the stuffing box  202  to connect with the impeller  306 . Due to the pressure of fluid within the centrifugal pump  100 , there is a potential for leakage from the stuffing box  202  where the rotating shaft  102  enters the stuffing box throat aperture  210 . The space between the rotating shaft  102  and the stuffing box throat aperture  210  is filled with a seal that typically encircles the rotating shaft  102  near the distal end of the stuffing box throat  204 . 
         [0003]    Seals used in a centrifugal pump  100  may take many forms. One example is compression packing, also known as rope packing. Compression packing encircles the rotating shaft  102  is such a manner that when the stuffing box  202  is installed on the centrifugal pump  100 , the compression packing is within the stuffing box throat  204 . A gland coupled to the stuffing box  202  exerts pressure into the stuffing box  202  and the compression packing to keep the compression packing in position. The displacement of the compression packing by the gland acts as a seal. 
         [0004]    In order for the compression packing to maintain integrity and act as a seal, it needs to remain lubricated. In oil field embodiments, the centrifugal pump  100  uses the fluid being transported as a lubricant for seals. If for some reason the centrifugal pump  100  runs during an interruption in the fluid flow, then the centrifugal pump  100  will operate without the benefit of lubrication. This will increase friction on the rotating shaft  102 , which will cause an increase in temperature that will ruin the seals. A ruined seal will force the operators to repair the pump or replace the centrifugal pump  100  and send the damaged centrifugal pump  100  for service. Additionally, even with proper lubrication, seals in a centrifugal pump  100  leak lubricant. 
         [0005]    Pump seals can fail for other reasons. Besides the interruption of fluid during operations, a centrifugal pump  100  may be started with insufficient prime. If there is no prime, then the fluid will not reach the seals to lubricate them. Once the centrifugal pump  100  starts operations, the movement of the rotating shaft  102  without adequate lubrication will cause friction, leading to heat buildup, compromising the seals. These and other previously unrecognized problems in the background of the invention lead to further development of the invention. 
       FIELD OF THE INVENTION 
       [0006]    The present invention relates preventing fluid from leaking from a centrifugal pump  100  by increasing the lubrication reliability of the seals of the centrifugal pump  100 . 
       SUMMARY 
       [0007]    The disclosed invention modifies an existing centrifugal pump  100  system to improve the seals of the centrifugal pump  100  by changing the seals themselves and providing said seals with an independent lubrication. Multiple references will be made to proximal end and distal end. Proximal will indicate towards the connection of the rotating shaft  102  and impeller  306 , while distal will indicate away from the connection of the rotating shaft  102  and impeller  306 . 
         [0008]    The disclosed invention creates a sealed chamber  304  within the stuffing box throat  204 . The stuffing box throat aperture  210  is constricted by an oil and grease seal  214  dimensioned to be inserted in the stuffing box throat aperture  210  and allow the exit of a shaft sleeve  104 . Within the stuffing box throat  204  is a stuffing box throat constriction  118  that narrows the stuffing box throat  204 . A stationary shaft seal  108  is installed towards the proximal end of the stuffing box throat constriction  118 . 
         [0009]    Next, a shaft sleeve  104  is inserted into the stuffing box throat  204 . The shaft sleeve  104  is dimensioned to pass though and be in contact with the inner surface of the oil and grease seal  214  as well as the stationary shaft seal  108 , but allow rotation of the shaft sleeve  104 . Coupled to the proximal end of the shaft sleeve  104  is a rotating shaft seal  106  made from a dry lubricant material. The shaft sleeve  104  is installed into the stuffing box throat  204  such that the shaft sleeve  104  passes through the stationary shaft seal  108  until the rotating shaft seal  106  makes contact with the stationary shaft seal  108 . When the centrifugal pump  100  is reassembled, a coil spring  112  is installed that encircles the rotating shaft  102 . When the stuffing box  202  is recoupled to the centrifugal pump  100 , the rotating shaft  102  will pass through the shaft sleeve  104 , in a manner that the shaft sleeve  104  will rotate as the rotating shaft  102  rotates. The coil spring will act on the rotating shaft seal  106 , which in turn applies pressure to the stationary shaft seal  108 . The pressure of the rotating shaft seal  106  pressing against the stationary shaft seal  108  creates a mechanical seal. The mechanical seal and the oil and grease seal  214  create the sealed chamber  304  that lubricant can be held in. 
         [0010]    A pair of openings are made in the stuffing box throat  204  at a substantially 45 degrees off from the horizontal axis. These openings allow at least one input tube  410  and at least one output tube  406  to be connected from the stuffing box  202  to a lubricant reservoir  402  located above the stuffing box  202 . These openings allow the lubricant to enter the sealed chamber  304  through the stuffing box lubricant inlet  308 . When the shaft sleeve  104  rotates, it acts as a gear pump, propelling a portion of the lubricant though the stuffing box lubricant outlet  310  with sufficient force to reenter the lubricant reservoir  402 . 
         [0011]    The shaft sleeve  104  may in an additional exemplary embodiment have a series of shaft sleeve indentations  116  that will assist in circulating the lubricant as the centrifugal pump  100  operates. The shaft sleeve indentations  116  alter the effectiveness of the gear pump created by the shaft sleeve  104 . 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0012]    For a more complete understanding of the present inventions and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numbers indicate features and wherein: 
           [0013]      FIG. 1  illustrates a combination of a coil spring  112 , a shaft sleeve  104 , a stationary shaft seal  108 , and a rotating shaft seal  106  over the rotating shaft  102  coupled to an impeller  306  in an exemplary embodiment, where the rotating shaft  102  and impeller  306  are shown in dotted outline. 
           [0014]      FIGS. 2A-2D  illustrate the installation of the stationary shaft seal  108  and the combined shaft sleeve  104  with rotating shaft seal  106  into a stuffing box  202  in an exemplary embodiment. 
           [0015]      FIG. 3  illustrates the integration of the invention within the centrifugal pump  100  in an exemplary embodiment. 
           [0016]      FIG. 4  illustrates the connection between a lubricant reservoir  402  and a stuffing box  202  in an exemplary embodiment. 
           [0017]      FIGS. 5A-5B  illustrate the stationary shaft seal  108  in an exemplary embodiment. 
           [0018]      FIGS. 5C-5D  illustrate the rotating shaft seal  106  in an exemplary embodiment. 
           [0019]      FIGS. 5E-5F  illustrate the rotating shaft sleeve  104  in an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The disclosed invention involves a stationary shaft seal  108 , a rotating shaft seal  106 , a shaft sleeve  104 , a coil spring  112 , an output tube  406 , an input tube  410 , and lubricant reservoir  402 . These items are used to create a mechanical seal within a centrifugal pump  100  that allows a lubricant reservoir  402  to preserve the seals of a centrifugal pump  100  independently of the fluid being transported by the centrifugal pump  100 . 
         [0021]    The disclosed items may be used to modify a preexisting centrifugal pump  100 . In an exemplary embodiment, the gland and the original stuffing box are removed to allow access to the interior of the centrifugal pump  100 . Removing the original stuffing box exposes the impeller  306  and the rotating shaft  102 . The packing surrounding the rotating shaft  102  is then removed in preparation for the installation of the invention in an exemplary embodiment. 
         [0022]    The disclosed invention uses a stuffing box  202  that differs from the original stuffing box. Within the stuffing box throat  204  in the exemplary embodiment is at least one stuffing box throat constriction  118 . This stuffing box throat constriction  118  is a narrowing of the stuffing box throat  204  toward at the proximal end of the stuffing box throat  204  where a stationary shaft seal  108  may be coupled. 
         [0023]    In the exemplary embodiment, the stationary shaft seal  108  is shown in  FIGS. 5A-5B , with the rotating shaft seal  106  shown in  FIGS. 5C-5D  and the shaft sleeve  104  shown in  FIG. 5E-5F . The process of modifying the seals in the exemplary embodiment is shown through  FIGS. 2A-2D . 
         [0024]    In an exemplary embodiment, the fixed components are installed first. The stationary shaft seal  108  is installed by placing it against the proximal end of the stuffing box throat constrictions  118 . The stationary shaft seal  108  is kept immobile by any means known to those skilled in the art. The stationary shaft seal  108  in the exemplary embodiment is held in position by stationary shaft seal indentation  504  that corresponds to an indentation in the stuffing box throat constriction  118 . The interaction of the stationary shaft seal indentation  504  may couple to the indention in the stuffing box throat constriction  118  in any manner known to those skilled in the art. For example, the stationary shaft seal indentation  504  and the indentation in the stuffing box throat constriction  118  may accept a fastener to keep them fixed relative to each other. The stationary shaft seal  108  includes a silicone seal  508  and a stationary shaft seal aperture  502 . The stuffing box  202  has an oil and grease seal  214  installed at the distal end of the stuffing box throat  204 . 
         [0025]    In addition to the fixed parts, there are rotating parts to be installed. A rotating shaft seal  106  in an exemplary embodiment includes a rotating shaft seal aperture  506 . In the exemplary embodiment, the rotating shaft seal  106  is made of tungsten carbide or silicon carbide. The rotating shaft seal  106  is used to apply pressure to the stationary shaft seal  108  when the centrifugal pump  100  is reassembled. The rotating shaft seal  106  is placed on the proximal end of the shaft sleeve  104 . The dimensions of the shaft sleeve  104  are such that the shaft sleeve  104  can pass through the stationary shaft seal  108  and the oil and grease seal  214 . The shaft sleeve  104  with rotating shaft seal  106  is installed in the stuffing box throat  204  in a manner where the distal end of the shaft sleeve  104  proceeds past the stationary shaft seal  108 , resulting in the face of the stationary shaft seal  108  and the face of rotating shaft seal  106  coming into contact. A substantial portion of the shaft sleeve  104  proceeds past the stationary shaft seal  108 . 
         [0026]    In an exemplary embodiment, a coil spring  112  is used to apply pressure to the rotating shaft seal  106 . To install the coil spring  112 , the impeller  306  is decoupled from the rotating shaft  102  and the coil spring  112  then is installed over the rotating shaft  102 . The impeller  306  is then recoupled to the rotating shaft  102 . When the seals are properly installed as described above, the stuffing box  202  is recoupled to the centrifugal pump housing  302  as shown in  FIG. 3 . The gland is no longer needed as it becomes a vestigial component in the exemplary embodiment. 
         [0027]    Once the stuffing box  202  is recoupled to the centrifugal pump housing  302 , the rotating shaft  102  now passes through the shaft sleeve  104 . The coil spring  112  pushes against the impeller  306 , applying force to the rotating shaft seal  106 , which in turn applies pressure on the stationary shaft seal  108 . The application of pressure on the stationary shaft seal  108  creates a mechanical seal in the proximal end of the stuffing box throat  204 .  FIG. 1  illustrates the coil spring  112  with the rotating shaft seal  106 , stationary shaft seal  108 , and shaft sleeve  104  over an outline of the location of the rotating shaft  102  and the impeller  306 . The oil and grease seal  214  form the barrier on the distal end of the stuffing box throat  204 . In the exemplary embodiment, the shaft sleeve  104  protrudes past the oil and grease seal  214 . The mechanical seal and the oil and grease seal  214  form a sealed chamber  304  in the stuffing box  202 . In this sealed chamber  304  the lubricant can be held to lubricate the stationary shaft seal  108  and the oil and grease seal  214 . 
         [0028]    Next a lubricant reservoir  402  is installed. As seen in  FIG. 4 , the lubricant reservoir  402  has a lubricant reservoir inlet  408  and lubricant reservoir outlet  404  to allow an input tube  410  and an output tube  406  to connect the lubricant reservoir  402  to the stuffing box  202 . The lubricant reservoir  402  may be mounted in any configuration known to those skilled in the art in a manner that allows the lubricant to naturally drain out the lubricant reservoir outlet  404 . This draining may occur from gravity or by a difference in pressure created by the rotation of the shaft sleeve  104 . 
         [0029]    The lubricant reservoir  402  may be placed in position in any manner know to those skilled in the art. One method may involve decoupling at least one of the fasteners that connect the stuffing box  202  to the centrifugal pump housing  302 . The lubricant reservoir  402  may be mounted on a projection that can be secured by placing the projection in the location of the fasteners such that when the fasteners are secured the centrifugal pump housing  302 , stuffing box  202 , and lubricant reservoir  402  are coupled together in a rigid configuration. 
         [0030]    In a further exemplary embodiment, the lubricant reservoir  402  may be mounted by replacing the stuffing box  202  all together by creating a modified stuffing box that already has the lubricant reservoir  402  mounted in any manner know to those skilled in the art. 
         [0031]    In an exemplary embodiment, the stuffing box  202  used is different from the original stuffing box that was decoupled from the centrifugal pump  100 . The stuffing box  202  used in an exemplary embodiment contains a stuffing box lubricant outlet  310  with an output coupler  414  located at substantially 45 degrees above the horizontal axis and a stuffing box lubricant inlet  308  with an input coupler  412  at substantially 45 degrees below the horizontal axis. 
         [0032]    In an alternative embodiment, the original stuffing box of the centrifugal pump  100  may be used as opposed to a stuffing box  202  specifically designed for use in the disclosed embodiment. The original stuffing box throat may be modified to include the stuffing box lubricant inlet  308  and stuffing box lubricant outlet  310  installed by any means know to those skilled in the art. The resulting modified original stuffing box acts substantially as the stuffing box  202  in the previous embodiments. 
         [0033]    In the operations of an exemplary embodiment, as the rotating shaft  102  rotates, the shaft sleeve  104  rotates as well, acting as a gear pump on the lubricant. As the lubricant fills the sealed chamber  304  through the stuffing box lubricant inlet  308 , lubricant comes into contact with the shaft sleeve  104 . The lubricant settles in the sealed chamber  304 , immersing the shaft sleeve  104  in lubricant. This provides a source of lubrication for the seals of the centrifugal pump  100  regardless of whether any fluid is being pumped through the centrifugal pump  100 . The rotation of the shaft sleeve  104  will force lubricant to be discharged through the stuffing box lubricant outlet  310  with sufficient force to reenter the lubricant reservoir  402  through the lubricant reservoir inlet  408 . The location of the openings of the stuffing box lubricant inlet  308  and stuffing box lubricant outlet  310  as disclosed above provide the optimum location to maximize the flow of lubricant to the lubricant reservoir  402 . 
         [0034]    In an additional exemplary embodiment, the shaft sleeve  104  further comprises shaft sleeve indentations  116 . These shaft sleeve indentations  116  assist the transfer of the lubricant into the lubricant reservoir  402 . In the exemplary embodiment, the shaft sleeve indentations  116  are characterized as being parallel to the long axis of the shaft sleeve  104 . The shaft sleeve  104  with shaft sleeve indentations  116  acts as a gear pump to move the lubricant by propelling the lubricant back into the lubricant reservoir  402  as previously discussed. The different shaft sleeve indentions  116  can alter the flow rate of the lubricant. Multiple shaft sleeve indentation  116  styles are possible. There may be indentations in any orientation without departing from the scope of the invention. 
         [0035]    In a further exemplary embodiment, the centrifugal pump  100  may be manufactured with the modifications previously discussed, with the stuffing box throat  204  comprising a stationary shaft seal  108  and an oil and grease seal  214  already installed. A rotating shaft seal  106  and a shaft sleeve  104  circumscribe the rotating shaft  102  as shown in previously disclosed embodiments. A coil spring  112  pushes against the impeller  306 , thereby pushing against the rotating shaft seal  106 . The force of the rotating shaft seal  106  against the stationary shaft seal  108  forms a mechanical seal on the proximal end of the stuffing box throat  204 , while an oil and grease seal  214  forms the seal at the distal end of the stuffing box throat  204 . The sealed chamber  304  between the mechanical seal and the oil and grease seal  214  receives lubricant from a lubricant reservoir  402 . The lubricant is received from a stuffing box lubricant inlet  308  at approximately 45 degrees below the horizontal axis of the centrifugal pump  100 . The lubricant leaves the sealed chamber  304  from a stuffing box lubricant outlet  310  at approximately 45 degrees above the horizontal axis of the centrifugal pump  100 . The rotation of the rotating shaft  102  sleeve acts as a gear pump, propelling lubricant back into the lubricant reservoir  402 . 
         [0036]    In an additional exemplary embodiment, the components for the previously discussed embodiments may be presented as a kit to alter an existing centrifugal pump  100  into one reflected in this disclosure. 
         [0037]    One of skill in the art will appreciate that embodiments provide improved seals for multiple pumping applications. Although specific embodiments are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose can be substituted for the specific embodiments shown. This specification is intended to cover any adaptations or variations of embodiments. For example, although described in terms of the specific embodiments, one of ordinary skill in the art will appreciate that implementations can be made in different embodiments to provide the required function. In particular, one of skill in the art will appreciate that the names and terminology are not intended to limit embodiments. Furthermore, additional apparatus can be added to the components, functions can be rearranged among components, and new components corresponding to future enhancements and future physical devices used in embodiments can be introduced without departing from the scope of embodiments. The terminology used in this application is intended to include all environments and alternatives which provide the same functionality as described herein.