Abstract:
A positive displacement fluid pump with increased service life is described. The positive displacement pump includes a plunger, a suction bore and a discharge bore. The plunger, the suction bore and the discharge bore form a pumping chamber. The diameter of the suction bore is greater than the diameter of the discharge bore. The difference in the diameters of the suction bore and the discharge bore allows for less fluid to be discharged through the discharge valve than what is being put into the bore through the suction valve and helps in increasing the service life of the pump. A method of operation of such a positive displacement pump is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS(S) 
       [0001]    This international patent application is based on co-pending U.S. Provisional Patent Application Ser. No. 61/824,617; Attorney Docket No.VP-13-1 PCT entitled, “Positive Displacement Pump”, filed May 17, 2013, the priority of which is hereby claimed and the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to a positive displacement pump which moves the fluid by changing the volume of its pumping chamber. More particularly, the present invention provides a method and system to improve the operational life of the positive displacement pump. 
         [0004]    2. Description of the Related Art 
         [0005]    Positive displacement pumps are the most commonly used fluid pumps in the industry. Positive displacement pumps displace a known quantity of fluid with each revolution or reciprocating action of the pumping elements. This is achieved by trapping fluid between the pumping elements i.e., a pumping chamber and a stationary casing. Typically, these pumps include two main sub-assemblies, the fluid end pump and the power end pump. The fluid end pump includes an input bore, or suction bore, for introducing the fluid inside the pumping chamber and an output bore, or a discharge bore, for discharging the fluid outside the pumping chamber. The input and output bores are provided with at least two check valves to ensure fluid movement in one direction from suction bore to the discharge bore. The conventional technologies in the fluid end pumps have the inlet bore diameter and outlet bore diameter of the same size. Whenever there is a fluid flow in the pump, the amount of fluid entered from the inlet bore gets discharged from the outlet bore in a single motion. Due to the quick discharge of the fluid, there exists a momentary state in the fluid end pump such that there is no fluid inside the pumping chamber. This results in cavitation in the pump chamber. The cavitation causes degradation of various parts of the pump and decreases the service life of the pump. In addition to that, the pumping process also causes generation of vibrations which further increase the wear and tear of the components of the positive displacement pumps. 
         [0006]    Various methods and technique have been provided in the past to overcome the mentioned drawbacks. For example, use of a pulsation dampener is well documented in the art. The pulsation dampeners are typically placed immediately downstream from a reciprocating pump, often with a relative size and configuration proportional to the volume of desired fluid displacement per stroke of the pump and the maximum allotted magnitude of the pressure peaks experienced by the pump during each pulsation. Pulsation dampeners thus aid in reducing pump loads and minimizing pulsation amplitudes to the pump, the pump&#39;s fluid end expendable parts and to equipment downstream. As a result, pulsation dampeners increase the relative operating performance and life of the pump, the pump&#39;s fluid end expendable parts and any equipment downstream from the pump. U.S. Pat. No. 5,888,056 by Kim Seong Cheol discloses a diaphragm pump having a simple structure for preventing the pulsation of liquid being discharged from the chamber. 
         [0007]    The pumps of the prior art tend to be difficult and expensive to assemble, as well as difficult to service economically. 
         [0008]    A few designs have been developed in the past to overcome the problems mentioned above. However, a need continues to exist to improve the lifetime of positive displacement pumps and minimize the need for maintenance of their internal components. 
         [0009]    References related to the art, and incorporated by reference herein: U.S. Pat. No. 5,888, 056—Diaphragm Pump—discloses a diaphragm pump having a structure to prevent pulsation of liquid being discharged, ultimately protecting pipes from damage and reducing noise level. 
         [0010]    U.S. Pat. No. 7,011,507—Positive Displacement Pump—discloses a high flow rate positive displacement pump where fluid is moved by changing the volume of its pumping chamber with a piston or diaphragm, and having different size chambers for inlet and outlet flow. 
         [0011]    US 2012/0189477—Pump Pulsation Discharge Dampener with Dual Pressure Drop Tube Assemblies Having Unequal Sizes.—discloses a pump discharge pulsation dampener with dual outlets in a reciprocating system. 
         [0012]    In light of the foregoing, there exists a need to provide a system and method that overcomes one or more shortcomings of the conventional positive displacement pumps. 
       SUMMARY 
       [0013]    An object of the present invention is to provide a positive displacement pump with an increased service life. 
         [0014]    Another object of the present invention is to provide a pump with maximized fluid into each bore (inlet and outlet bore) during use. 
         [0015]    Yet another object of the present invention is to provide a redesigned fluid end pump to minimize the pin-hole formation and cavitation in the bore of the pump. 
         [0016]    Yet another object of the present invention is to provide a fluid end pump with minimized vibration. 
         [0017]    Embodiments of the invention provide a design of a fluid end of the positive displacement pump. The pump includes a movable plunger, a pumping chamber, an inlet bore for providing an inlet for a fluid in the pumping chamber, and an outlet bore for providing an outlet for the fluid. The volume of the discharge chamber varies as the plunger strokes. The inventive pump comprises a diameter of the outlet bore being less than the diameter of the inlet bore such that the design maintains a continuous flow of fluid passing through the outlet bore. The design also maximizes the passage of fluid during use of the pump. The positive displacement pump further includes a seat, valve, retainer valve, and a valve spring. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0018]    The features of the present invention are set forth with particularity in the appended claims. Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the scope of the claims, wherein like designations denote like elements, and in which: 
           [0019]      FIG. 1  illustrates a cross-sectional view of a positive displacement pump; and 
           [0020]      FIG. 2  illustrates a cross-sectional view of a suction bore and a discharge bore of a positive displacement pump. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0021]    The invention is described in detail below with reference to several embodiments and numerous examples. Such discussion is for purposes of illustration only. Modifications to particular examples within the spirit and scope of the present invention, set forth in the appended claims, will be readily apparent to one of skill in the art. Terminology used herein is given its ordinary meaning consistent with the exemplary definitions set forth immediately below. 
         [0022]    As used in the specification and claims, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “an article” may include a plurality of articles unless the context clearly dictates otherwise. 
         [0023]    Those with ordinary skill in the art will appreciate that the elements in the Figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the Figures may be exaggerated, relative to other elements, in order to improve the understanding of the present invention. 
         [0024]    There may be additional components described in the foregoing application that are not depicted on one of the described drawings. In the event such a component is described, but not depicted in a drawing, the absence of such a drawing should not be considered as an omission of such design from the specification. 
         [0025]    While the specification concludes with the claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawings, in which like reference numerals are carried forward. 
         [0026]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of the invention. 
         [0027]    A cross-sectional view of a positive displacement pump  100  is shown in  FIG. 1 , in accordance with various embodiments of the present invention. The positive displacement pump  100  is a reciprocating pump having two main sub-assemblies: a power end pump (not shown) and a fluid end pump  102  as shown in the figure. The positive displacement pump  100  is configured to reciprocate one or more plungers  104  (only one shown in  FIG. 1 ). Each plunger  104  is preferably connected by a suitable rotatable crankshaft (not shown) mounted in the power end pump. 
         [0028]    The fluid end pump  102  mainly includes the plunger  104 , a suction bore  106 , and a discharge bore  108  as shown in  FIG. 1 . The plunger  104 , the suction bore  106 , and the discharge bore  108  are enclosed in a housing  110  or a fluid cylinder  110 . One end of the plunger  104  is fixedly connected to a plunger clamp  112 , while the other end of the plunger  104  is movable with respect to the plunger clamp  112 . The volume enclosed between the plunger  104 , the suction bore  106  and the discharge bore  108  forms a pumping chamber  114 . The overall volume of the pumping chamber  114  changes along with the movement of the plunger  104 . The movement of the plunger  104  helps to draw the fluid in or out of the pumping chamber  114 , depending on the direction of a stroke thereof. 
         [0029]    It should be appreciated that the plunger  104  can be made hollow from the inside and provided with a flat head design. It should also be appreciated that the plunger  104  can also use any other type of head designs such as a round head design, and the like. The thickness of the walls of the plunger  104  is about 1 inch. The thickness of the walls can vary in accordance with desired use thereof, and a range of thickness is about 0.75 inch to 2.0 inch. The plunger  104  is preferably nickel coated to prevent corrosion and minimize wear and tear of the plunger  104 . The use of an anti-corrosion coating, such as nickel, enhances the service life of the fluid end pump  102 . The plunger,. as well as the bores can also be made from special grades of stainless steel such as SS 17-4PH or equivalent alloy steel materials such as 4330 modified steel. Other materials can include cast iron, or (while costly) titanium. A preferred tensile strength for the materials of use with the invention is about 186000 psi having a yield of about 173000 psi. The materials may be tempered up to 800° F., and quenched to achieve tensile and yield strength. 
         [0030]    The suction bore  106  is configured to act as an inlet of the pumping chamber  114  for the fluid and the discharge bore  108  is configured to act as an outlet of the pumping chamber for the fluid. Both the suction bore  106  and the discharge bore  108  are provided with at least one valve, i.e., an inlet valve  116  and an outlet valve  118 , to control flows of fluid from the suction bore  106  and the discharge bore  108  respectively. A plurality (not shown) of packing nuts  120  are also provided to hold the inlet valve  116  and the outlet valve  118  in place. The packing nuts  120  can be removed during the servicing of the fluid end pump  102 . 
         [0031]    The inlet valve  116  and the outlet valve  118  further include a valve spring  122 , shown at base of plunger and a retainer ring  124 . The valve spring  122  and the retainer ring  124  are configured to work together to keep the valves  116  and  118  in place from blowing off the top. The valve spring  122  and the retainer ring  124  also allow a consistent amount of fluid to pass from the valves  116  and  118 . 
         [0032]    According to an embodiment of the disclosure, the diameter of the suction bore  106  and the discharge bore  108  are made of different sizes as shown in  FIG. 2 . The diameter of the suction bore  106  (i.e., D 1 ) is greater than the diameter of the discharge bore  108  (i.e., D 2  ). In other words, D 1 &gt;D 2 . The time taken for a specific amount of fluid coming in the pumping chamber  114  will be less as compared to the time taken for the same amount of fluid going out of the pumping chamber  114 . Thus, the fluid remains inside the pumping chamber  114  for more time as compared to that in the pumps of the prior art or discussed in the background section of this application. The presence of fluid inside the pumping chamber  114  effectively works as a lubricant and keeps the fluid end pump  102  positively fed. This will minimize the likelihood of cavitation.  FIG. 2  shows the edges around the bores, or radius, to be somewhat sharp. As an option, the bores may be designed with smooth curves or smooth edges allowing for easier fluid flow there through. 
         [0033]    In an example, the diameter of the bores are 2 to 8 inches, wherein the suction bore  106  is approximately 2 to 8 inches, in particular 2 to 6 inches and more particularly 2 to 4.0 inches, with more particularly 4.61 inches, while the diameter of the discharge bore  108  is no more than 20% less than the suction bore, but for exemplary purposes is approximately 3.0 inches, and more particularly 3.83 inches. A 20% differential in size between D 1  and D 2  is recommended. The diameter sizes are not limited only to the dimensions mentioned herein. The diameters of the suction bore  106  and the discharge bore  108  can be changed appropriately by the manufacturer or user as per the requirements, maintaining the diameter D 1  greater than the diameter D 2 . 
         [0034]    Generally, the diameter does not vary by more than about 20%; however, this size differential can be optimized according to the specific pump employed and needs of the user, and may be for example 10 to 15% different in size between discharge and suction bore, and more particularly, 5 to 10% different in diameter sizing. 
         [0035]    The fluid end pump  102  is also provided with one or more seal rings  126 . The seal rings  126  are generally provided at each of the opening shown opposite the plunger, not at either of the bores of the pumping chamber  114 . The seal rings  126  are configured to seal the pumping chamber  114  from the outer atmosphere. Thus, the seal rings  126  stop the internal fluid from leaking out of the pumping chamber  114 . In addition, the seal rings  126  also maintain a high pressure inside the pumping chamber and protect the pump from exploding. 
         [0036]    According to an embodiment of the disclosure, the measured input pressure P in  (at the suction bore) is about 90 psi to about 100 psi, while the measured output pressure, P out  is about 8 psi to about 14 Kpsi (at the discharge bore); P out  should be higher than P in . The pumping hours of the modified inventive pump were found to be about 600 hrs. Further, the pump packing life will increase due to the positive prime of the fluid bore. 
         [0037]    If it is desired to pump oil/fluid from wells of greater depth, it is within the scope of the present invention to provide two or more pumps in series. The pumps are connected in series with multiple air, feed and power or flow supply lines, with each pump on a cycle controller at the surface regulated by a timing device. The series of pumps operate in the same manner as described herein. The length of each individual pump can be any practical length, for example from about 4 to about 30 feet, but generally is from about 6 to about 10 feet. The diameter of the pump chamber can vary depending upon the well bore/casing diameters, and needs for the pump. In general, the pump diameter size is about 2 to 8 inches, generally from about 2 to 6 inches, more particularly 2-4 inches. While the pump chamber has been described herein as cylindrical in length having a circular cross section, the cross section can be any configured shape, such as square, triangle, etc. 
         [0038]    Those skilled in the art will recognize that the design of the present disclosure may be utilized with a wide variety of single and multi-cylinder reciprocating pumps as well as possibly other types of positive displacement pumps. For example, the number of cylinders of such pumps may vary substantially between a single cylinder and essentially any number of cylinders or separate pumping chambers. Often, the number of cylinders varies between 3 and 5 cylinders on separate pumping chambers. But this number depends on the needs of the user. 
         [0039]    Those skilled in the art will also recognize that the complete structure and operation of a suitable pump system is not depicted or described herein. Instead, for simplicity and clarity, only so much of a pump system as is unique to the present disclosure or necessary for an understanding of the present disclosure is depicted and described. 
       EXAMPLES 
       [0040]    Field examples were conducted with an existing SPM brand triplex fluid end pump, TWS 2250, having a modified chamber or suction bore, wherein the diameter of the suction bore was 4.61 inches, while the diameter of the discharge bore was 3.83 inches. The pump dimensions were 5′×5′×5′ of the external housing and having a 3 cylinder crank shaft, and an 8″ stroke. The power source was supplied by a diesel, CAT (Caterpillar Engine Transmission), 12 cylinder, 7 speed transmission to operate the power train. The suction side of the pump was primed with standard fluid and powered by a Mission Magnum (“MM XP”)brand, 12×14 XP system. The external power source employed was a Detroit diesel engine, although any brand is acceptable provided they meet the power limits needed. Here, a 600-800 HP (horsepower) pump ran the MM XP at a rate of about 30-120 barrel fluid/min. The MM XP ran at about 1400-1600 rpm, and a gradual progression of sand/fluid addition began. The pumps were set up in a series of 18, with the individual pumps operating at about 5-6 barrels fluid/minute/rate. In the wellbore, high pressure fluid was pumped through the top end of the pump and discharging at a rate of about 5,000-15,000 psi, with an average employed being about 11,000 psi. The discharge rate can vary depending on the desired need and requirements. A high pressure pipe was employed having a 1502 union connection. The guar gel/water based fluid used to be pumped into well, had a viscosity of about 25-30 centipoise. The sand employed was a 20/40 ratio mix, which can be purchased by such manufacturers such as Carbo Ceramics or Momentum. Sand was added to fluid during a 2 hour pumping time for an ultimate sand/fluid ratio of 30/70. A step progression was utilized for addition of the sand and fluid as follows: 0-3 lbs. sand: gallon of fluid to make a slurry mix. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Time 
                 Sand (%) 
                 Fluid (%) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0-30 
                 min 
                 0 
                 100 
               
               
                 30-45 
                 min 
                 5 
                 95 
               
               
                 45-1 
                 hr. 
                 10 
                 90 
               
               
                 1-1.45 
                 hr. 
                 20 
                 80 
               
               
                 1.45-2 
                 hr. 
                 30 
                 70 
               
               
                   
               
             
          
         
       
     
         [0041]    It was found surprising, as well as superior, that the modified inventive pumps employed were in use with no changes observed to the bore or the pumps after 2 hours of continued use. No maintenance of the pumps was required after 2 hours of continued use, and the pumps remained only warm to the touch (approximately 120-130° F.). Prior art pumps were found to be hot to the touch under similar to identical conditions, and lead to cavitation/destruction of the pump. During use, the inventive pump remained stable and did not shake, even when pumping at 11,000 psi. Ultimately, studies showed the inventive pumps&#39; lifetime was over 600 pumping hours before needing any change outs or maintenance. In comparison, standard pumps failed at about 200-300 hours average of use under similar or same conditions. 
         [0042]    These pumps were tested for several days, under outside temperature conditions of about 98° F. The above tests utilizing this modified bore pumping system demonstrate the uniqueness of the invention. 
         [0043]    The advantage of using the present invention modified bore-pump system is readily seen, particularly when one considers small amount of capital investment required and the extended shelf life of the resultant pump. 
         [0044]    The present invention has been described herein with reference to a particular embodiment for a particular application. That is, for high pressure targeted applications in the oil/gas industry, and in particular for use in fracking formations. While the objective is to perfect the fluid end pump in a high pressure environment, it can also be employed in lower pressure environments, or lower pressure job needs. Although selected embodiments have been illustrated and described in detail, it may be understood that various substitutions and alterations are possible. Those having ordinary skill in the art and access to the present teachings may recognize additional various substitutions and alterations are also possible without departing from the spirit and scope of the present invention, and as defined by the following claims.