Abstract:
A pump assembly having a power end and a fluid end, wherein the fluid end includes a plurality of pump bodies connected side by side between opposing end plates with a plurality of fasteners tightened to compress the pump bodies between the end plates. The power end and at least one of the plurality of pump bodies being connected together by a tie rod having a rod portion and a sleeve portion, wherein the sleeve portion surrounds the rod portion and abuts the power end at an end and at least one of the pump bodies of the fluid end at an opposite end.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 12/840,545, filed on Jul. 21, 2010, and entitled PUMP BODY, which claims priority to U.S. Provisional application No. 61/233,709, filed on Aug. 13, 2009, and entitled PUMP BODY; this application also claims benefit of priority to U.S. Provisional patent application No. 61/394,079, filed Oct. 18, 2010, and entitled PUMP ASSEMBLY WITH IMPROVED TIE ROD; the entire contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure is related in general to wellsite surface equipment such as fracturing pumps and the like. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    Reciprocating pumps such as triplex pumps and quintuplex pumps are generally used to pump high pressure fracturing fluids downhole. An example of a triplex or quintuplex pump is disclosed in commonly assigned PCT Application No. PCT/IB2010/053868, the entire contents of which are hereby incorporated by reference into the current disclosure. Typically, the pumps that are used for this purpose have plunger sizes varying from about 7 cm (2.75 in.) to about 16.5 cm (6.5 in.) in diameter and may operate at pressures up to 144.8 MPa (21,000 psi). In one case, the outer diameter of the plunger is about 9.5 cm (3.75 in) and the reciprocating pump is a triplex pump. 
         [0005]    These pumps typically have two sections: (a) a power end, the motor assembly that drives the pump plungers (the driveline and transmission are parts of the power end); and (b) a fluid end, the pump container that holds and discharges pressurized fluid. 
         [0006]    In triplex pumps, the fluid end has three fluid cylinders. For the purpose of this document, the middle of these three cylinders is referred to as the central cylinder, and the remaining two cylinders are referred to as side cylinders. A fluid end may comprise a single block having cylinders bored therein, known in the art as a monoblock fluid end. Similarly, a quintuplex pump has five fluid cylinders, including a middle cylinder and four side cylinders. 
         [0007]    The pumping cycle of the fluid end is composed of two stages: (a) a suction cycle: During this part of the cycle a piston moves outward in a packing bore, thereby lowering the fluid pressure in the fluid end. As the fluid pressure becomes lower than the pressure of the fluid in a suction pipe (typically 2-3 times the atmospheric pressure, approximately 0.28 MPa (40 psi)), the suction valve opens and the fluid end is filled with pumping fluid; and (b) a discharge cycle: During this cycle, the plunger moves forward in the packing bore, thereby progressively increasing the fluid pressure in the pump and closing the suction valve. At a fluid pressure slightly higher than the line pressure (which can range from as low as 13.8 MPa (2,000 psi) to as high as 144.8 MPa (21,000 psi) the discharge valve opens, and the high pressure fluid flows through the discharge pipe. In some cases, the pump is operated at 12,000 psi. In some other cases, the pump is operated at 15,000 psi. In some further cases, the pump is operated at 20,000 psi. 
         [0008]    In assembling and operating these pumps at such harsh conditions, zones of weaknesses have been identified which present a high potential for failure and injury. One example zone includes the tie rods used to connect the power and the fluid end of the pumps, and more particularly the threads at each end of the tie rods. As a precaution, tie rods that are generally used in the industry need to be periodically inspected and replaced in an effort to prevent the tie rod from becoming defective. 
         [0009]    It is therefore desirable to provide an improved tie rod and pump equipment to increase efficiency, flexibility, reliability, and maintainability. 
       SUMMARY OF THE DISCLOSURE 
       [0010]    According to an aspect of the present disclosure, one or more embodiments relates to a pump assembly comprising a power end, a fluid end, and a tie rod. The fluid end comprises a plurality of pump bodies connected side by side between opposing end plates with a plurality of fasteners tightened to compress the pump bodies between the end plates. The tie rod for connecting the power end and at least one of the pump bodies of the fluid end comprises a rod portion and a sleeve portion. The sleeve portion surrounds the rod portion and abuts the power end at an end and at least one of the pump bodies of the fluid end at an opposite end. 
         [0011]    According to another aspect of the present disclosure, one or more embodiments relate to a method comprising connecting a power end and a fluid end having a plurality of pump bodies side by side between opposing end plates with a plurality of fasteners to form a pump assembly. The method includes connecting the power end and at least one of the pump bodies of the fluid end with a tie rod, wherein the tie rod comprises a rod portion and a sleeve portion. The sleeve portion surrounds the rod portion and abuts the power end at an end and at least one of the pump bodies of the fluid end at an opposite end. 
         [0012]    These together with other aspects, features, and advantages of the present disclosure, along with the various features of novelty, which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. The above aspects and advantages are neither exhaustive nor individually or jointly critical to the spirit or practice of the disclosure. Other aspects, features, and advantages of the present disclosure will become readily apparent to those skilled in the art from the following detailed description in combination with the accompanying drawings. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]    To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings, which are not intended to be drawn to scale, and in which like reference numerals are intended to refer to similar elements for consistency. For purposes of clarity, not every component may be labeled in every drawing. 
           [0014]      FIG. 1  depicts a fluid end perspective view of a triplex pump fluid end assembly according to an embodiment of the disclosure. 
           [0015]      FIG. 2  depicts another fluid end perspective view of the triplex pump fluid end assembly of  FIG. 1  according to an embodiment of the disclosure. 
           [0016]      FIG. 3  depicts a power end perspective view of the triplex pump fluid end assembly of  FIGS. 1-2  according to an embodiment of the disclosure. 
           [0017]      FIG. 4  depicts a partially disassembled view of the triplex pump fluid end assembly of  FIGS. 1-3  according to an embodiment of the disclosure. 
           [0018]      FIG. 5  depicts a perspective view of one of the pump body portions of the triplex pump fluid end assembly of  FIGS. 1-4  according to an embodiment of the disclosure. 
           [0019]      FIG. 6  depicts a side sectional view of the pump body of  FIG. 5  according to an embodiment of the disclosure. 
           [0020]      FIG. 7  depicts a perspective view, partially cut away, of the pump fluid end assembly of  FIGS. 1-4  according to an embodiment of the disclosure. 
           [0021]      FIG. 8  depicts another fluid end perspective view of the triplex pump fluid end assembly of  FIGS. 1-3  according to an embodiment of the disclosure. 
           [0022]      FIG. 9  depicts a perspective view of the bore configuration of the pump body of  FIGS. 5-6  according to an embodiment of the disclosure. 
           [0023]      FIG. 10  depicts an exploded view of the triplex pump fluid end assembly of  FIGS. 1-3  according to an embodiment of the disclosure. 
           [0024]      FIG. 11  depicts a power end perspective view of the triplex pump fluid end assembly of  FIGS. 1-3  having a plurality of tie rods attached thereto according to an embodiment of the disclosure. 
           [0025]      FIG. 12  depicts a cross-sectional view of a tie rod according to an embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    Specific embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. Further, in the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the embodiments disclosed herein may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. 
         [0027]    The terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as “including,” “comprising,” “having,” “containing,” or “involving,” and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited. 
         [0028]    Referring now to all of the Figures, there is disclosed a pump body portion or fluid end, indicated generally at  100 . The pump body portion  100  comprises a body  102  that defines an internal passage or piston bore  104  for a receiving a pump plunger (best seen in  FIG. 7 ). The pump body portion  100  may further define an inlet port  106  and an outlet port  108 . The inlet port  106  and the outlet port  108  may be substantially perpendicular to the piston bore  104 , forming a 
         [0029]    conventional crossbore body portion  100 , best seen in  FIG. 6 . The piston bore  104  may comprise a pair of bores, such as that shown in  FIG. 9 . The intersection of the piston bore  104  and the inlet and outlet ports  106  and  108  defines at least one area  110  of stress concentration that may be a concern for material fatigue failure. In addition to the stress concentration, the area  110  is subject to operational pressure of the pump discussed hereinabove, which may further increase its fatigue failure risk. Those skilled in the art will appreciate that the pump body portion  100  may comprise bores formed in other configurations such as a T-shape, Y-shape, in-line, or other configurations. 
         [0030]    According to some embodiments, three pump body portions  100  are arranged to form a triplex pump assembly  112 , best seen in  FIG. 1 . Those skilled in the art will appreciate that the pump body portions  100  may also be arranged in other configurations, such as a quintuplex pump assembly comprising five pump body portions  100  or the like. 
         [0031]    A raised surface  114  extends from an exterior surface  116  of the pump body portions  100 , best seen in  FIG. 5 . The raised surface  114  may extend a predetermined distance from the exterior surface  116  and may define a predetermined area on the exterior surface  116 . In one embodiment, at least one pump body comprises a raised surface on an opposite exterior side surface of the pump body. In another embodiment, each pump body comprises a raised surface on the opposite exterior side surface of the pump body. While illustrated as circular in shape in  FIG. 5 , the raised surface  114  may be formed in any suitable shape. 
         [0032]    An end plate  118  is fitted on each of the outer or side pump body portions  100  to aid in assembling the body portions  100  into the pump fluid end assembly, such as the triplex pump fluid end assembly  112  shown in  FIG. 1 . The end plates  118  are utilized, in conjunction with fasteners  120 , to assemble the pump body portions  100  to form the pump fluid end assembly  112 . The end plates  118  may further comprise a raised surface  119 , best seen in  FIG. 10 , similar to the surface  114  on the pump body portions  100  for engaging with the raised surfaces  114  of the pump body portions  100  during assembly. 
         [0033]    The bores  104 ,  106 , and  108  of the pump body portions  100  may define substantially similar internal geometry as prior art monoblock fluid ends to provide similar volumetric performance. When the pump fluid end assembly  112  is assembled, the three pump body portions  100  are assembled together using, for example, four large fasteners  120  and the end plates  118  on opposing ends of the pump body portions  100 . At least one of the fasteners  120  may extend through the pump body portions  100 , while the other of the fasteners  120  may be external of the pump body portions  100 . 
         [0034]    As the fasteners  120  are torqued (via nuts or the like) to assemble the pump fluid end assembly  112 , the raised surfaces  114  on the pump body portions  100  and raised surfaces  119  on the end plates  118  engage with one another to provide a pre-compressive force to the areas  110  of the pump body portions  100  adjacent the intersection of the bores  104 ,  106 , and  108 . The pre-compressive force is believed to counteract the potential deformation of the areas  110  due to the operational pressure encountered by the bores  104 ,  106 , and  108 . By counteracting the potential deformation due to operational pressure, stress on the areas  110  of the pump body portions  100  is reduced, thereby increasing the overall life of the pump bodies  100  by reducing the likelihood of fatigue failures. Those skilled in the art will appreciate that the torque of the fasteners  120  and the raised surfaces  114  and  119  cooperate to provide the pre-compressive force on the areas  110 . 
         [0035]    Due to the substantially identical profiles of the plurality of pump body portions  100 , the pump body portions  100  may be advantageously interchanged between the middle and side portions  100  of the assembly  112 , providing advantages in assembly, disassembly, and maintenance, as will be appreciated by those skilled in the art. In operation, if one of the pump bodies  100  of the assembly  112  fails, only the failed one of the pump bodies  100  need be replaced, reducing the potential overall downtime of a pump assembly  112  and its associated monetary impact. The pump body portions  100  are smaller than a typical monoblock fluid end having a single body with a plurality of cylinder bores machined therein and therefore provides greater ease of manufacturability due to the reduced size of forging, castings, etc. 
         [0036]    An attachment flange  122 , best seen in  FIG. 3 , may extend from the pump body portion  100  for guiding and attaching a power end  150  (see  FIG. 12 ) to the plungers (see  FIG. 7 ) and ultimately to a prime mover (not shown), such as a diesel engine or the like, as will be appreciated by those skilled in the art. 
         [0037]    The attachment flange  122  may further comprise a plurality of holes  180  and have a plurality of tie rods  186  attached thereto, as shown in  FIG. 11 . According to at least one embodiment of the present disclosure, the tie rods  186  are substantially cylindrical in shape, comprising a body portion and at least one threaded portion  183  (see  FIG. 12 ) at an end that is adapted for matingly engaging the hole  180 . The body portion can be substantially uniform in diameter along the length of the body, as shown as rod  186   a  in  FIG. 11 . In another embodiment, at least one portion of the body of the tie rod is enlarged to form a stepped ring or shouldered portion  188 , as shown as rod  186   b  in  FIG. 11 . In some cases, the stepped ring  188  is formed towards the end of the rod  186   b  that will be attached to the attachment flange  122 . 
         [0038]    During operation, the threads at each end of the tie rods  186  are susceptible to fatigue. The threads at the power end of the triplex pump assembly  112  are particularly vulnerable. When the threads become defective, the tie rod  186  can no longer hold the pump assembly  112  tightly together. As a result, pump failure and injury/casualty to pump operators may occur. 
         [0039]    In at least one embodiment of the present disclosure, a tie rod  186  is provided which comprises at least two portions: a sleeve portion  182  and a rod portion  184 . In one embodiment, the sleeve portion  182  is substantially cylindrical in shape, with an internal hollow space to accommodate the rod portion  184 . The rod portion  184  can be substantially uniform in diameter. Alternatively, the rod portion  184  may have at least one stepped ring  188  as shown in  FIG. 11  of the disclosure. In some embodiments, the outer diameter of the rod portion  184  is smaller than the inner diameter of the sleeve so that the rod portion  184  can slide in and out of the sleeve portion  182  during assembly. Alternatively, the outer diameter of the rod portion  184  can be substantially the same as the inner diameter of the sleeve portion  182  so that substantial amount of friction can exist between the outer surface of the rod portion  184  and the inner surface of the sleeve portion  182 . In some embodiments, the sleeve portion  182  is a monolithic product; in some other embodiments, the sleeve portion  182  comprises a plurality of sub-components, such as two half cylindrical walls, etc., which can be attached together during the assembly to surround the rod portion  184  of the tie rod  186 . 
         [0040]    As shown in  FIG. 11 , a pump assembly  112  constructed in accordance with an embodiment of the present disclosure may include any number of tie rods  186  for connecting the power end  150  and the fluid end body portions  100 . For example, twelve tie rods  186  are shown for joining the fluid end body portions  100  and the power end  150 . Connection with the tie rods  186  may be made by machining complementary threaded bores into the attachment flange  122  or the power end  150  to be threadingly engageable with the threaded portion  183  of the tie rod  186 . Alternatively, connection between the fluid end body portions  100  and the power end  150  may be made by tightening a nut  190 , such as a heavy hex nut or the like, on the tie rod  186 . 
         [0041]    Referring now to  FIG. 12 , a cross-sectional view of a tie rod  186  is shown according to one embodiment of the current disclosure. The tie rod  186  comprises a rod portion  184  and a sleeve portion  182 . The sleeve portion  182  has a length that is substantially equal to the distance between the fluid end attachment flange  122  and the power end  150 . In one implementation of assembly, the sleeve portion  182  functions as a spacer between the power end  150  and the fluid end attachment flange  122 , abutting against the fluid end attachment flange  122  and the power end  150 . Therefore, the magnitude of fluctuation of the power end  150  and/or the fluid end body portions  100  can be partially transferred to the sleeve portions  182 . The load on the rod portion  184  is substantially reduced and the stress on the threads is decreased. As a result, the threads of the rod portion  184  are protected and the life of the tie rod  186  is prolonged. 
         [0042]    The preceding description has been presented with reference to some embodiments. Persons skilled in the art and technology to which this disclosure pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principle, and scope of this disclosure. For example, even though the Figures of the current disclosure illustrate a sleeve portion and a rod portion have a cross-sectional profile of a ring and a circle, respectively, other profiles and shapes such as triangular, square, pentagon, hexagon, and so on are also possible. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.