Abstract:
This invention relates to a method of fabricating or machining the fluid end of a high pressure pump and a fluid end produced by the method. The method includes sculpturing the front side of the fluid end which results in a non-planar surface. In this manner the internal stresses can be varied at critical points within the fluid end.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to the design of fluid pumps used for pumping fluid at a relatively high pressure into a well. One example of such a process is the hydraulic fracturing process for oil and/or gas well applications. These pumps are commonly referred to as frac pumps. Other uses may include pumping cement or other fluids into the well. 
         [0003]    In the case of frac pumps, the pumps are typically mounted on a truck/trailer and several may be used in series or in parallel to pump the fracturing fluid under high pressure into the well. As fracturing techniques become more popular and productive there is a continuing need to increase the horsepower capability of the pumps and the flow rate. However, as horsepower and operating pressures increase, so does the size of the pump and the failure rate. 
         [0004]    The present invention addresses techniques to balance and/or modify stress loads within the pump housing which permits larger capacity pumps to be fabricated using lighter housings than previously thought possible with less failure. 
         [0005]    2. Description of Related Art 
         [0006]    Known frac pumps comprise generally two sections, the power end and the fluid end. The power end includes a housing for the drive shafts for the reciprocating pistons that extend into the fluid end. The fluid end includes the inlet ports, outlet ports and the cylinders for the reciprocating pistons. The two ends are normally bolted together. The fluid end may include up to five or more separate fluid pump chambers. Examples of this type of pump can be found in U.S. Pat. Nos. 6,419,459 B1 and 7,341,435 B2. Currently the fluid end of the pump tends to be damaged due to pressure imbalances, fatigue, and higher pressures and horsepower. The current invention overcomes these difficulties by a technique referred to as sculpturing the normally flat end surface of the front side of the fluid end. This technique can be used to balance the forces within the fluid portion of the pump. This technique also allows for higher pressure with no increase in mass. These and other advantages of the invention will be more fully explained in the detailed description of the invention which follows. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The essence of the invention is the discovery that by varying the shape, that is, sculpturing the front side of the fluid end of a high pressure pump, the internal stresses within the fluid housing can be controlled. This allows the pump to be designed in such a manner so as to minimize the mass of the pump end to minimize the possibility of structural failure. For example a frac pump can be designed so that the tendency of the fluid end of the pump to be pumped off the power end is minimized as well as lowering the occurrence of structural failure within the housing due to internal pressure. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0008]      FIG. 1  is a perspective view of a fluid end of a conventional frac pump. 
           [0009]      FIG. 2   a  is a perspective view of a conventional fluid end having one pump chamber. 
           [0010]      FIG. 2   b  is a cross section of the fluid end of  FIG. 2   a.    
           [0011]      FIG. 3   a  is a perspective view of a fluid end of a pump according to one embodiment of the invention. 
           [0012]      FIG. 3   b  is a cross section of the fluid end of  FIG. 3   a.    
           [0013]      FIG. 4   a  is a perspective view of a fluid end of a pump according to a second embodiment of the invention. 
           [0014]      FIG. 4   b  is a cross sectional view of the fluid end of  FIG. 4   a.    
           [0015]      FIG. 5   a  is a perspective view of a fluid end of a pump according to a third embodiment of the invention. 
           [0016]      FIG. 5   b  is a cross sectional view of the fluid end of  FIG. 5   a.    
           [0017]      FIG. 6   a  is a perspective view of a fluid end of a pump according to a fourth embodiment of the invention. 
           [0018]      FIG. 6   b  is a cross sectional view of the fluid end of FIG.  6 Aa 
           [0019]      FIG. 7   a  is a perspective view of a fluid end of a frac pump according to a further embodiment of the invention. 
           [0020]      FIG. 7   b  is a cross sectional view of the embodiment of  FIG. 7   a.    
           [0021]      FIG. 8   a  is a perspective view of a further embodiment of the invention. 
           [0022]      FIG. 8   b  is a cross sectional view of the embodiment of  FIG. 8   a.    
           [0023]      FIG. 9   a  is a perspective view of a further embodiment of the invention. 
           [0024]      FIG. 9   b  is a cross sectional view of the embodiment of  FIG. 9   a.    
           [0025]      FIG. 10  is a perspective view of the fluid end attached to the power end of a high pressure pump. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]      FIG. 1  illustrates a conventional fluid end  10  of a high pressure pump. The fluid end includes an inclined top surface  20  having a plurality of bores  12  for receiving outlet valve mechanisms which are not shown. Fluid end  10  has a planar front side  11  and a rear side  13  that is adapted to be bolted to the power end  50 , shown in  FIG. 10 . Suitable bores  14 ,  15  are provided for receiving threaded bolts. A horizontally extending outlet passageway  16  is in fluid communication with each of the outlet chambers  21  of the pumps as shown in  FIG. 2B . Fluid end  10  further includes a lower extending inclined portion  19 . A plurality of inlet ports  22  are located in portion  19 . Planar front side portion  11  externals vertically between inclined surfaces  20  and  19  when the pump is secured to a truck bed. The rear side  13  of the fluid end includes a plurality of bores  23  for receiving the pistons (not shown) which are driven by the power end of the pump. The arrangement of the pistons, the fluid inlet, and the fluid outlet is commonly referred to as the “Y” design for a frac pump as shown in  FIG. 2   b . However, a “T” configuration could also be used. Stress values at locations  30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 , and  37  shown in  FIG. 2   b  were derived using finite element analysis techniques in order to demonstrate the principles of the invention. The solid model used for the analysis was created with Solid Works 2009—SP4.1 software. All the bores were completed exactly as shown in  FIG. 2   b . A pressure load in the bores was established as a baseline on all internal areas that see pressure. The baseline used is the current standard fluid end having a flat surface as shown in  FIG. 2   a . Cosmos Software was the finite element analysis software tool utilized in the tests. After establishing the baseline data, the only change made in the procedure was the configuration of the front face of the fluid end. The distance from the rear side  13  to the front side was 21.75 inches. Subsequent models indicated that as the distance became greater than 23 inches, sculpturing has very little effect on the stress levels. Von Mises stresses for the various locations in the standard design of  FIG. 2   b  are as follows: 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 POSITION 
                 Von Mises Stress (PSI) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 30 
                 4389 
               
               
                   
                 31 
                 3986 
               
               
                   
                 32 
                 4803 
               
               
                   
                 33 
                 7751 
               
               
                   
                 34 
                 49173 
               
               
                   
                 35 
                 54940 
               
               
                   
                 36 
                 32178 
               
               
                   
                 37 
                 55806 
               
               
                   
                   
               
             
          
         
       
     
         [0027]    The differences in stress at points  30  and  33  is believed to contribute to the tendency of the fluid end to separate from the power end. 
         [0028]    An embodiment of the principles of the present invention is shown in  FIG. 3   a . It should be noted that while  FIGS. 2   a  through  FIG. 9   a  show a single pump chamber, this is for convenience only and each embodiment may include several pump chambers located side by side in a common body as shown in  FIG. 1 . Referring the  FIG. 3   a , the fluid end of the pump is similar to that shown in  FIG. 1  with the exception that the planar face  11  has been modified to have a plurality of vertically extending groves  40  and ribs  39 . This change in the shape of the surface  11  of the fluid end portion of the pump has a significant impact on the pressure loads within and on the fluid end.  FIG. 4   a  illustrates a second configuration wherein there are three vertically extending ribs provided on the outside surface with grooves  40  between the ribs.  FIG. 5   a  illustrates another embodiment wherein a horizontally extending notch  51  is formed in the front side  11  of the fluid end of the pump. 
         [0029]    In the embodiment of  FIG. 6   a , a single wave-like rib  39  extends from the surface  11  of the fluid end of the pump. In the embodiment of  FIG. 7   a , a plurality of diagonal ribs  61 , in this case 5, with grooves between them are provided on the front surface  11  of the fluid end. According to another embodiment, as shown in  FIG. 8   a  the front surface is formed with two diagonally extending ribs  82  forming a wave like pattern.  FIG. 9   a  illustrates an embodiment wherein six ribs  91  are formed in the end face with seven grooves  92 . 
         [0030]    The effects of the various designs of the front surface  11  of the various embodiments on the stress measured at points  30 - 37  are summarized in the following table: 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 VON MISES STRESS VALUES FOR VARIOUS EMBODIMENTS S (PSI) 
               
             
          
           
               
                   
                 FIG. 2b 
                 FIG. 3b 
                 FIG. 4b 
                 FIG. 5b 
                 FIG. 6b 
                 FIG. 7b 
                 FIG. 8b 
                 FIG. 9b 
               
               
                   
                   
               
             
          
           
               
                 Position 
                 30 
                 4389 
                 2367 
                 6554 
                 6050 
                 4046 
                 3630 
                 4390 
                 4240 
               
               
                 Locations 
                 31 
                 3986 
                 6864 
                 9000 
                 6853 
                 4525 
                 3921 
                 4075 
                 4025 
               
               
                   
                 32 
                 4803 
                 2390 
                 1832 
                 1623 
                 7000 
                 5075 
                 5190 
                 4480 
               
               
                   
                 33 
                 7751 
                 3031 
                 1052 
                 1276 
                 7496 
                 8460 
                 8575 
                 8340 
               
               
                   
                 34 
                 49173 
                 49340 
                 48656 
                 47220 
                 49200 
                 47600 
                 52760 
                 49060 
               
               
                   
                 35 
                 54940 
                 62156 
                 65263 
                 49730 
                 53135 
                 55720 
                 52720 
                 53675 
               
               
                   
                 36 
                 32178 
                 36966 
                 37908 
                 31810 
                 31020 
                 31930 
                 31310 
                 33430 
               
               
                   
                 37 
                 55806 
                 59930 
                 56372 
                 45960 
                 50253 
                 51425 
                 50990 
                 55600 
               
               
                   
               
             
          
         
       
     
         [0031]    The above table illustrates that the stress levels within the pump chamber and the forces working on the upper and lower portions of the inside face  13  of the fluid end of the pump can be dramatically changed by altering the shape of the front face  11  of the fluid end. 
         [0032]    Based on this discovery, it is possible to select an appropriate design that will improve the reliability of the pump and increase its power handling capability with no increase in mass. 
         [0033]    For example in the case of the embodiment of  FIG. 3   b , the stresses applied at positions  30  and  33  are such that the difference between the two has been reduced to 664 psi while the stress at point  33  of  FIG. 3   b  has been reduced by 4720 psi compared to that at point  33  of  FIG. 2   b.    
         [0034]    Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims. For example, the inlet valves could be arranged in the top portion  20  of the fluid end and the outlet valves could be arranged in the bottom portion  19  of the fluid end. Outlet passageway  16  would then be relocated to the lower portion.