Patent Publication Number: US-2023160393-A1

Title: Stuffing box for vertical pumps

Description:
BACKGROUND 
     Vertical pumps are a type of centrifugal pump designed to move a fluid from a well or reservoir to an upper position. Vertical pumps comprise a bottom opening or suction bell where the liquid enters that is located at the lower side of the pump and a discharge which is located at the upper side of the pump where the fluid is discharged at higher pressure. Vertical pumps further comprise a driver which is usually an electric motor that is connected to the vertical pump shaft to transmit the torque to the impeller(s). Once the driver is turned on, the impeller rotates and moves the fluid from the bottom opening to the top opening. 
     The electric motor is located outside the vertical pump, whereas the impeller is located inside the vertical pump. The shaft is rotatably disposed in a top opening of the housing wall of the vertical pump. Therefore, the annular space between the shaft and the top opening of the housing wall needs to be sealed in a manner that the shaft is still rotatable. 
     Packing seals are used to seal the shaft against the top opening of the housing wall. Packing seals have a low cost, however, packing seals can cause premature wear on the shaft which can lead to a complete overhaul of the vertical pump. Packing seals require frequent adjustment to compensate the wear of the materials used in the packing seal. On average, a bi-weekly adjustment is performed by a technician. If the packing seal is adjusted excessively, the packing seal reaches high temperatures resulting in damages to the shaft. 
     Accordingly, there exists a need for a low maintenance sealing of the shaft against the top opening of the vertical pump. 
     SUMMARY 
     This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
     In one aspect the claimed subject matter relates to a stuffing box for sealing a top opening of a vertical pump, comprising: a housing with a vertical tube for rotatably disposing a shaft of the vertical pump, an annular bearing that: divides the vertical tube in a lower half and an upper half, and fills an annular space between an inner wall of the vertical tube and the shaft, such that as less fluid as possible passes from the lower half through the annular bearing to the upper half, an outlet pipe for discharging the fluid passing through the annular bearing. 
     Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Specific embodiments of the disclosed technology will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency. 
         FIG.  1    shows a cross-sectional view of a stuffing box, according to one or more embodiments disclosed herein. 
         FIG.  2    shows a top view of the stuffing box according to  FIG.  1    during a functionality test using an external water source. 
         FIG.  3    shows a flow chart of the initial operation of the vertical pump using the stuffing box to seal the top opening of the vertical pump according to  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION 
     In one aspect, embodiments disclosed herein relate to a stuffing box for sealing a top opening of a vertical pump. The stuffing box has a housing with a vertical tube for rotatably disposing a shaft of the vertical pump, an annular bearing that divides the vertical tube in a lower half and an upper half, and fills an annular space between an inner wall of the vertical tube and the shaft, such that as less fluid as possible passes from the lower half through the annular bearing to the upper half. In addition, the stuffing box has an outlet pipe for discharging the fluid passing through the annular bearing. In one or more embodiments, the stuffing box is a self-adjusted, force cooled, leak-proof seal packing. 
     Embodiments of the present disclosure may provide at least one of the following advantages. 
     The stuffing box provides a continuous flushing for lubrication of the bearing with the fluid and at the same time provides an outlet pipe to discharge the fluid. This reduces the pressure by fluid release, which reduces the leakage to a minimum. Furthermore, the stuffing box provides a higher reliability and low maintenance cost on a pumping application. The maintenance and replacement of parts is performed without removing the stuffing box from the top opening of the vertical pump. Advantageously, due to its simplicity, the stuffing box may be implemented on any pumping application and its dimensions can be customized to every design. 
     In one or more embodiments, the stuffing box is a hybrid design between a conventional pump packing and a mechanical seal. The stuffing box provides a combination of both seals for higher reliability and low maintenance cost on pumping applications. 
       FIG.  1    shows a cross-sectional view of a stuffing box  102 , according to one or more embodiments. The stuffing box  102  comprises an annular housing  104  with a vertical tube  106  going through the housing  4 . The housing  104  comprises stainless steel. A shaft  108  of a vertical pump is rotatably disposed through the vertical tube  106 . An annular bearing  110  divides the vertical tube  106  in a lower half  112  and an upper half  114 , where the lower half  112  is filled with a fluid once the vertical pump starts pumping the fluid. 
     Turning to the lower half  112 , an annular bushing  116  is disposed below the annular bearing  110  surrounding the shaft  108 . The annular bushing  116  reduces the pressure of the fluid in the lower half  112  towards the annular bearing  110 . An annular sleeve bearing  118  is disposed at a lower opening  120  of the housing  104 . 
     Turning to the upper half  114 , an annular pumping ring  122  is disposed above the annular bearing  110 . Above the pumping ring  122 , an annular floating seal  124  is disposed around the shaft  108 . Above the floating seal  124 , an annular packing seal  126  surrounds the shaft  108 . 
     The packing seal  126  further reduces or even eliminates the leakage of the fluid from the housing  104 . The number of sealing elements in the stuffing box  102  is reduced to a minimum, namely 3 elements. These elements are the annular packing seal  126 , the floating seal  124 , and the annular bushing  116 . Compared to prior art designs, which usually comprise  10  sealing elements, the heat generation, caused by the friction between the annular bearing  110  and the moving shaft  108 , is minimal. 
     The stuffing box  102  further comprises an inlet pipe  128  and an outlet pipe  130 . The inlet and outlet pipe  128 ,  130  connect the upper half  114  with an outside of the stuffing box  102 . A shaft sleeve  132  is disposed at an upper opening  134  of the housing  104 . Furthermore, the housing  104  comprises a flange  140  for attaching the stuffing box  102  to the top opening of the vertical pump. In one or more embodiments, the flange  140  is integrally formed with the housing as one piece. A gland pusher  136  is pushed against the flange  140  by four springs  138  that continuously adjust the gland pusher  136  against the flange  140  and the annular packing seal  126 . The springs  138  are self-adjusting. The self-adjusted springs  138  compensate the wear of the packing and provide a continuous adjustment through the spring force towards the flange  136 . The self-adjustment mechanism of the springs  138  requires no human intervention as a short frequency. 
     Once the vertical pump begins turning the shaft  108 , the impeller of the vertical pump pumps the fluid through the vertical pump generating an overpressure at the lower half  112 . The overpressure presses the fluid from the lower half  112  through the annular bearing  110  to the upper half  114 . The fluid is then discharged from the upper half  114  through the outlet pipe  130  to a sump pit by the pumping ring  122 . The fluid flushes and lubricates the annular bearing  110  while passing through the annular bearing  110 . 
     In one or more embodiments, a clean fluid (if needed) is injected into the upper half  114  through the inlet  128 , in case the fluid from the lower half  112  is dirty. The clean and dirty fluid mix in the upper half  114  and discharge through the outlet pipe  130 . 
     The floating seal  124  regulates the fluid to be discharged through the outlet pipe  130  and the fluid to be injected through the inlet pipe  128 . The pumping ring  122  uses the power of the shaft  108  for regulating the quantity of fluid for lubrication of the mechanical seal components. In this way, the annular bearing  110  is continuously flushed and lubricated. 
     Since the fluid in the upper half  114  has a much lower pressure than the fluid in the lower half  112 , the fluid in the upper half  114  does not have enough pressure to press out of the housing  104  through the floating seal  124  and the packing seal  126 . Reducing the pressure of the fluid minimizes the leakage of the fluid from the upper half  114  and thus from the housing  104  of the stuffing box  102 . 
     The clean fluid is used under dirty process conditions. The clean fluid prevents scale or solidifications inside the stuffing box which will reduce the life of the packing seal  126 . 
       FIG.  2    shows a top view of the stuffing box according to  FIG.  1    during a full functionality test by using an external water source and a power tool, which is a drilling machine used to simulate an electric motor, wherein the power tool rotates the shaft  108 . The functionality test needs to be performed at a shop before the stuffing box is installed at a field. 
     The four springs  138  push the gland pusher  136  against the flange  140  of the housing  104  and the packing arrangement is compressed with a continuous force for a prolonged time period, reducing the maintenance of frequent adjustments of the packing arrangement. 
     The functionality test was performed at a site on a vertical pump with a top opening sealed with the stuffing box. The vertical pump was pumping water from the external water source and only minor leakage occurred through the stuffing box. This leakage was fully eliminated by increasing the tension of the springs  138  on the gland pusher. 
       FIG.  3    shows a flowchart of the initial operation of the vertical pump using the stuffing box to seal the top opening of the vertical pump according to  FIG.  1   . The initial operation of the vertical pump begins with the first step  302 , which is the initial turning of the shaft by the electric motor of the vertical pump. The turning of the shaft turns the impeller and the movable mechanical components of the bearing. 
     In step  304 , the turning impeller of the vertical pump moves a fluid from the lower opening to the upper opening of the vertical pump and the moving fluid generates a pressure in the lower half of the stuffing box. 
     In step  306 , the pressure presses the fluid from the lower half through the bearing to the upper half of the stuffing box. The fluid passing through the bearing cools and lubricates the mechanical components of the bearing. 
     In step  308 , clean fluid is injected from the inlet pipe to the upper half of the stuffing box and the annular chamber  210 . The clean fluid mixes with the fluid passing from the lower half through the bearing. The clean fluid cleans the bearing in case the fluid from the lower half is dirty. 
     In step  310 , the pumping ring pumps the mixed fluid from the upper half of the stuffing box to the outlet pipe, where the fluid is ejected out of the stuffing box. The pumping ring is driven by the moving shaft. In one or more embodiments, the ejected fluid is returned to the fluid being pumped by the vertical pump. In other embodiments, the ejected fluid is disposed. 
     The operation of the vertical pump according to the method steps  302 - 310  is a continuous operation and continues as long as the vertical pump pumps the fluid. The fluid passes constantly through the bearing during the operation of the vertical pump and the pumping ring constantly pumps the fluid out of the outlet pipe. This constant operation of the of the vertical pump according to the method steps  302 - 310  keeps the bearing and its mechanical seal components lubricated during the pumping of the fluid by vertical pumps. 
     Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112(f) for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.