Patent Publication Number: US-2019178243-A1

Title: Multi-Piece Fluid End

Description:
BACKGROUND 
     Fluid ends are used in oil and gas operations to deliver highly pressurized corrosive and/or abrasive fluids to piping leading to a wellbore. Fluid is pumped throughout a fluid end by a plurality of plungers disposed within bores formed in the fluid end body. An engine attached to a power end causes the plungers to reciprocate within the bores. The power end is attached to the fluid end via a plurality of stay rods. Stay rods are known in the art as elongate steel rods. 
     Fluid used in high-pressure hydraulic fracturing operations is typically pumped through the fluid end at a minimum of 5,000 to 8,000 psi; however, fluid will normally be pumped through the fluid end at pressures around 10,000-15,000 psi during such operations. 
     The corrosive and/or abrasive fluid pumping through a fluid end at high flow rates and pressures causes the fluid end to wear faster than a power end. Thus, a fluid end typically has a much shorter lifespan than a power end. A typical power end may service five or more different fluid ends during its lifespan. The stay rods used to attach the fluid ends to power ends may be reused with each new fluid end. 
     In fluid ends known in the art, such as the fluid end  300  shown in  FIGS. 14 and 15 , a flange is machined into a fluid end body to provide a connection point for a plurality of stay rods. A flange  302  is shown formed in a fluid end body  304  in  FIGS. 14 and 15 . A plurality of stay rods  306  interconnect a power end  308  and the flange  302 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a fluid end attached to a power end. 
         FIG. 2  is a side elevation view of the fluid end and power end shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the fluid end shown in  FIG. 1 , taken along line A-A. The inlet manifold has been removed for clarity. 
         FIG. 4  is a cross-sectional view of the fluid end shown in  FIG. 3 . The inner and outer components of the fluid end have been removed for clarity. 
         FIG. 5  is a cross-sectional view of the fluid end shown in  FIG. 1 , taken along line B-B. The inlet manifold has been removed for clarity. 
         FIG. 6  is a partially exploded perspective view of a back side of the fluid end. A plurality of stay rods used to attach the fluid end to the power end are shown installed within a second body of the fluid end. 
         FIG. 7  is a perspective view of the power end shown in  FIG. 1  with the stay rods attached thereto. The fluid end has been removed for clarity. 
         FIG. 8  is a perspective view of a front side of the second body of the fluid end shown in  FIG. 6 . The components installed within the second body have been removed for clarity. 
         FIG. 9  is a perspective view of the power end of  FIG. 7  with the second body of  FIG. 8  attached thereto. The first body of the fluid end has been removed for clarity. A portion of the fastening system used to secure the second body to the power end is shown exploded for reference. 
         FIG. 10  is a side elevation view of the power end and attached second body shown in  FIG. 9 . The second body and stay rods attaching the second body to the power end are shown in cross-section. 
         FIG. 11  is a perspective view of a back side of an alternative embodiment of a fluid end. 
         FIG. 12  is a cross-sectional view of the fluid end shown in  FIG. 11 , taken along line C-C. 
         FIG. 13  is a cross-sectional view of the fluid end shown in  FIG. 11 , taken along line D-D. 
         FIG. 14  is a perspective view of a fluid end known in the art attached to a power end. 
         FIG. 15  is a side elevation view of the fluid end and power end shown in  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION 
     The inventors have recognized that current fluid end designs including those shown in  FIGS. 14 and 15  are problematic for several reasons. First, for those designs having a flange, the machining required to create a flange reduces the strength of the fluid end by producing stress concentrations that reduce the effective life of the fluid end. Second, machining the flange into the fluid end also entails wastage of significant amounts of removed raw material, and requires a significant investment of time and labor, thus resulting in increased manufacturing costs. 
     One solution to the issues presented by a machined flange is to remove the flange and attach the stay rods directly to the fluid end body. However, this solution requires uniquely designed stay rods that must be replaced with the fluid end each time the fluid end reaches the end of its lifespan. Such an approach may thus be disadvantageous during actual operation of the device. 
     To address these problems, the inventors have designed a multi-body-piece fluid end, embodiments of which are shown in  FIGS. 1-13 . Such designs, particularly those that are flangeless, may lead to less stress being placed on the fluid end during operation, resulting in increased product life. This design also uses fewer raw materials, reducing manufacturing costs. Still further, the construction of the fluid end permits it to be attached to a power end using traditional stay rods. 
     In general, fluid ends with multiple body pieces are contemplated by the present disclosure. Thus, the fluid end body is not formed from a monolithic piece of material as in certain prior art designs. As will be described below,  FIGS. 1-2 , for example, illustrate a fluid end with two body pieces,  20  and  22 ; this design achieves savings in raw materials (and thus cost), and also leads to less stress on the fluid end during operation, in part because of the flangeless design. That is, neither of body pieces  20  or  22  includes a flange, such as flange  302  shown in  FIGS. 14-15 . As used herein, a “flange” is used according to its ordinary meaning in the art, and includes a piece of a structural member that has a wider portion as compared to another portion of the structural member, such as a rim, rib, collar, plate, ring, etc. In  FIGS. 14-15 , for example, the flanged member has the shape of a half I-beam, or alternately a sideways “T”-shape. As used herein, a “flangeless” fluid end body piece is one that does not include a flange. 
     In embodiments with two body pieces, the second body piece, upon installation, is closer to the power end than the first body piece. In such an arrangement, a front side of the second body piece may engage with a back side of the front body piece in various manners. In certain embodiments, the first and second body pieces may be in flush engagement, meaning that the entire surface of the front side of the second body piece (excluding bores and through holes since these areas have no surface) is in contact with the back side of the first body piece. The concept of flush engagement thus includes embodiments in which the front side of the second body piece and the back side of the first body piece have the same surface dimensions, as well as embodiments in which the back side of the front body piece has at least one surface dimension that is larger than a corresponding surface dimension of the front side of the second body piece. In the former scenario, the front side of the second body piece may be said to align with and abut the back side of the first body piece. In other embodiments, the front side of the second body piece might have one or more beveled edges, such that it has slightly smaller dimensions than the back side of the first body piece. Flush engagement between the front side of the second body piece and the back side of the first body piece includes embodiments in which the engaging portions of the two surfaces are planar, as well as embodiments in which the surfaces are not planar. Alternately, the front side of the second body piece may be partially engaged with the back side of the second body piece, meaning that not every portion of the front side of the second body piece contacts a portion of the back side of the first body piece. Note that partial engagement between the two body pieces may exist both when the two pieces have the same surface dimensions (for example, certain portions of one or both of the pieces may project such that only those portions contact the other piece), as well as when the second body piece has at least one surface dimension that is greater than a corresponding surface dimension of the first body piece. 
     The present disclosure also contemplates fluid ends with more than two body pieces. For instance, the front side of the second body piece may engage with the back side of the first body piece via one or more spacer elements. For example, washers might be used to separate the first and second body pieces at a distance. In other embodiments, the spacer element may be a thin intervening body piece configured to be situated between the first and second body pieces. The portion of the fluid end nearest the power end upon installation can also be composed of multiple individual pieces (“a plurality of second fluid end body pieces”), each of which has a front side that can engage with the back side of the first body in one of the various manners described above. Whether the portion of the fluid end nearest the power end is composed of a single piece or two or more sub-pieces, this portion being flangeless may advantageously reduce internal stress on the fluid end and extend its life. 
     Turning now to the figures,  FIGS. 1-2  show a fluid end  10  with two body pieces attached to a power end  12 . The power end  12  comprises a housing  14  having a mounting plate  16  formed on its front end. A plurality of stay rods  18  attach to the mounting plate  16  and project from its surface. As will be discussed in more detail later herein, the fluid end  10  attaches to the projecting ends of the stay rods  18 . 
     The fluid end  10  comprises a first body  20  releasably attached to a separate second body  22 . The first and second bodies  20  and  22  both have a plurality of flat external surfaces  24 ,  26 . Each surface  24 ,  26  may be rectangular in shape. The exterior surfaces  24  and  26  of each body  20  and  22  may be joined in the shape of a rectangular prism. However, the corner edges of such prism may be beveled. As will be discussed in more detail later herein, a back side  28  of the first body  20  is attached to a front side  30  of the second body  22 . In some embodiments, the bodies  20  and  22  are attached such that a portion of the external surface  24  of the first body  20  is in flush engagement with a portion of the external surface  26  of the second body  22 . 
     With reference to  FIG. 4 , a plurality of rectilinear first bores  32 , one of which is shown in  FIG. 4 , are formed in the first body  20 . The plural first bores  32  are arranged in side-by-side relationship. Each of the first bores  32  extends through the entirety of the first body  20 , interconnecting the top and bottom ends  34  and  36 . At each of its opposed ends  34  and  36 , the first bore  32  opens at the external surface  24 . The diameter of each first bore  32  may vary throughout its length. Adjacent the top end  34  of the first body  20 , each first bore  32  is closed by an installed component  38 , as shown in  FIG. 3 . Each component  38  is releasably held within its first bore  32  by a retainer element  40  and fastening system  42 , as shown in  FIGS. 1-3, 5 and 6 . 
     The components  38 , retainer elements  40 , and fastening system  42  shown in  FIG. 3  may comprise those described in U.S. patent application Ser. No. 16/035,126, authored by Foster, et al. (the &#39;126 Application), the entire contents of which are incorporated herein by reference. Likewise, the inner components of the fluid end  10 , shown in  FIG. 3 , may comprise those inner components described in the &#39;126 Application. 
     At the bottom end  36  of the first body  20 , each of the first bores  32  is joined by a conduit  44  to an inlet manifold  46 , as shown in  FIGS. 1-2 . Fluid enters the fluid end  10  through the conduits  44  of the inlet manifold  46 . 
     Continuing with  FIG. 4 , a plurality of rectilinear second bores  48 , one of which is shown in  FIG. 4 , are formed in the first body  20 . The plural second bores  48  are arranged in side-by-side relationship. Each of the second bores  48  extends through the entirety of the first body  20 , interconnecting the front and back sides  50  and  28 . At each of its opposed sides  50  and  28 , each second bore  48  opens at the external surface  24 . Each of the second bores  48  intersects a corresponding one of the first bores  32 . Each second bore  48  may be disposed in orthogonal relationship to its intersecting first bore  32 . 
     Adjacent the front side  50  of the first body  20 , each second bore  48  is closed by an installed component  52 , as shown in  FIG. 3 , which may be identical to the component  38 . Each component  52  is releasably held within its second bore  48  by a retainer element  54  and fastening system  56 , as shown in  FIGS. 1-3 and 5 . The retainer element  54  may be identical to the retainer element  40 , and the fastening system  56  may be identical to the fastening system  42 . 
     With reference to  FIGS. 4, 6 and 8 , a plurality of rectilinear bores  58 , one of which is shown in  FIG. 4 , are formed in the second body  22 . The bores  58  are arranged in side-by-side relationship. Each of the bores  58  extends through the entirety of the second body  22 , interconnecting the front and back sides  30  and  60 . At each of its opposed sides  30  and  60 , each bore  58  opens at the external surface  26 . Each bore  58  includes a counterbore  59  formed adjacent the back side  60  of the second body  22 , as shown in  FIGS. 4 and 6 . Each bore  58  formed in the second body  22  registers with a corresponding one of the second bores  48  formed in the first body  20 . When the bodies  20  and  22  are joined and aligned, each bore  58  becomes an extension of its associated second bore  48 , as shown in  FIG. 4 . 
     With reference to  FIG. 3 , a plunger  62  is installed within each pair of aligned bores  48  and  58 . A sealing arrangement  64  is installed within each pair of aligned bores  48  and  58 , and surrounds the plunger  62  within those bores. Each sealing arrangement  64  comprises a stuffing box sleeve  66  that houses a series of annular packing seals  71 . The stuffing box sleeves  66  and packing seals  71  may be selected from those described in the &#39;126 Application. 
     A retainer element  68  is installed within each bore  58 , and holds the stuffing box sleeve  66  within such bore. Each retainer element  68  is secured to a flat bottom  69  of the counterbore  59  of its associated bore  58 . A fastening system  70  holds the retainer element  68  in place. The seals  71  are compressed by a packing nut  72  threaded into an associated retainer element  68 . The retainer elements  68 , fastening system  70 , plungers  62 , and packing nuts  72  may be selected from those described in the &#39;126 Application. 
     Turning back to  FIGS. 1-2 , the power end  12  comprises a plurality of pony rods  74 . Pony rods are known in the art as elongate rods that interconnect the crankshaft of a power end to each of the plungers positioned within a fluid end. Each pony rod  74  extends through a corresponding opening formed in the mounting plate  16 . Each pony rod  74  is attached to a corresponding one of the plungers  62  by means of a clamp  76 . An engine attached to the power end  12  drives reciprocating movement of the pony rods  74 . Such movement of the pony rods  74  causes each plunger  62  to reciprocate within its associated pair of aligned bores  48  and  58 . High pressure fluid pumped through the fluid end  10  by the plungers  62  exits the fluid end  10  through one or more outlet conduits  78 . 
     With reference to  FIGS. 6 and 7 , each stay rod  18  comprises a cylindrical body  84  having opposed first and second ends  80  and  82 . External threads are formed in the body  84  adjacent each of its ends  80  and  82 . These threaded portions of the body  84  are of lesser diameter than the rest of the body  84 . A step separates each threaded portion of the body from its unthreaded portion. Step  85  is situated adjacent the first end  80 , and step  86  is situated adjacent the second end  82 . 
     Continuing with  FIG. 7 , a plurality of internally threaded connectors  88  are supported on the front surface of the mounting plate  16 . Each connector  88  mates with the threaded first end  80  of a corresponding stay rod  18 . An integral nut  90  is formed on each stay rod  18  adjacent its first end  80 . The nut  90  provides a gripping surface where torque may be applied to the stay rod  18  during installation. Once a stay rod  18  has been installed in a connector  88 , its second end  82  projects from the front surface of the mounting plate  16 . In alternative embodiments, the stay rods  18  may thread directly into holes formed in the mounting plate. 
     With reference to  FIGS. 8-10 , the second body  22  is secured to the stay rods  18  using a fastening system  92 . The fastening system  92  includes a plurality of washers  94  and a plurality of internally threaded nuts  96 . A plurality of bores  98  are formed about the periphery of the second body  22 . The number of bores  98  may equal the number of stay rods  18 . A single stay rod  18  is installed within each of the bores  98 , at its second end  82 , as shown in  FIG. 10 . Each bore  98  includes a counterbore  100  formed adjacent the front side  30  of the second body  22 , as shown in  FIGS. 8 and 10 . Adjacent counterbores  100  may overlap each other, as shown in  FIGS. 8 and 9 . In alternative embodiments, each bore may be spaced from each adjacent bore such that their respective counterbores do not overlap. 
     A stay rod  18  is installed by inserting its second end  82  into the opening of the bore  98  formed in the back side  60  of the second body  22 . The stay rod  82  is extended into the bore  98  until the step  86  abuts the back side  60 , as shown in  FIG. 10 . 
     When a stay rod  18  is installed, its second end  82  projects within the counterbore  100  of its associated bore  98 . To secure each stay rod  18  to the second body  22 , a washer  94  and nut  96  are installed on the second end  82  of the stay rod  18 , as shown in  FIGS. 9 and 10 . Each nut  96  and its underlying washer  94  press against a flat bottom  102  of the counterbore  100  within which they are installed. Each nut  96  is fully submerged within its recessed counterbore  100 . 
     With reference to  FIGS. 3-6 , the first body  20  is secured to the second body  22  using a fastening system  104 . The fastening system  104  comprises a plurality of studs  106 , a plurality of washers  108 , and plurality of internally threaded nuts  110 . Each stud  106  comprises a cylindrical body  116  having a pair of opposed ends  112  and  114 , as shown in  FIGS. 3-5 . Each of the ends  112  and  114  is externally threaded. 
     A plurality of internally threaded openings  118  are formed about the periphery of the first body  20 , as shown in  FIGS. 3-5 . The first end  112  of each stud  106  mates with a corresponding one of the openings  118 . Once a stud  106  has been installed in the first body  20 , its second end  114  projects from the body&#39;s external surface  24 , as shown in  FIG. 6 . 
     A plurality of through-bores  120  are formed about the periphery of the second body  22 , as shown in  FIGS. 3-5 . The through-bores  120  are alignable with the plural studs  106  projecting from the first body  20 . 
     To assemble the first and second bodies  20  and  22 , the plural studs  106  are installed in the plural openings  118  of the first body  20 . The first body  20  and installed studs  106  are positioned such that each through-bore  120  formed in the second body  22  is aligned with a corresponding stud  106 . The first and second bodies  20  and  22  are then brought together such that each stud  106  is received within a corresponding through-bore  120 . When the bodies  20  and  22  are thus joined, the second end  114  of each stud  106  projects from the back side  60  of the second body  22 . Finally, a washer  108  and nut  110  are installed on the second end  114  of each stud  106 , as shown in  FIGS. 2-5 , thereby securing the bodies together. 
     Continuing with  FIG. 5 , one or more pin bores  122  may be formed in the first body  20  adjacent its outer edges. Each pin bore  122  may receive a pin  124  that projects from the external surface  24  of the first body  20 , as shown in  FIGS. 5 and 6 . These pins  124  may be installed within a corresponding bore  126  formed in the second body  22 , as shown in  FIGS. 5 and 6 . The pins  124  help align the first and second bodies  20  and  22  during assembly of the fluid end  10 . 
     The concept of a “kit” is described herein due to the fact that fluid ends are often shipped or provided unassembled by a manufacturer, with the expectation that an end customer will use components of the kit to assemble a functional fluid end. Accordingly, certain embodiments within the present disclosure are described as “kits,” which are unassembled collections of components. The present disclosure also describes and claims assembled apparatuses and systems by way of reference to specified kits, along with a description of how the various kit components are actually coupled to one another to form the apparatus or system. 
     Several kits are useful for assembling the fluid end  10 . A first kit comprises the first body  20  and the second body  22 . The first kit may also comprise the fastening system  92  and/or the fastening system  104 . The first kit may further comprise the components  38  or  52 , sealing arrangements  64 , retainer elements  40 ,  54  or  68 , fastening systems  42 ,  56  or  70 , packing nuts  72 , plungers  62 , and/or clamps  72 , described herein. 
     With reference to  FIGS. 6-8 , the positioning of the bores  98  around the periphery of the second body  22  corresponds with the positioning of the stay rods  18  on the mounting plate  16 . Thus, each second body  22  is constructed specifically to match different stay rod  18  spacing configurations known in the art. 
     As shown in  FIGS. 2-6 , the second body  22  has a lesser thickness than the first body  20  (thickness being measured in  FIG. 2  along the line A-A, for example). However, the bodies  20  and  22  have the same depth and height, so that they form a rectangular prism when assembled. Thus, the front side of the second fluid end body and the back side of the first fluid body may have the same dimensions in some embodiments. In other embodiments, the dimensions of these opposing sides may be different. Also, it is noted that the corner edges of such prism may be beveled. 
     The first and second bodies  20 ,  22  may be formed from a strong durable material, such as steel. Because the first body  20  must receive fluids under conditions of high pressure, it may be formed from stainless steel or cast iron. In contrast, the second body  22  does not receive high pressure fluids: it serves only as a connection between the power end  12  and the first body  20 . The second body  22  can thus be formed from a different, lower strength, and less costly material than the first body  20 . For example, when the first body  20  is formed from stainless steel, the second body can be formed from a less costly alloy steel. Alternatively, the first and second bodies may be formed from the same material, such as stainless steel. 
     In order to manufacture the fluid end  10 , the first and second bodies  20  and  22  are each cut to size from blocks of steel. Multiple first or second bodies  20  or  22  may be forged from the same block. In such case, the bodies  20  and  22  may be forged by dividing the block parallel to its length into multiple rectangular pieces. Because a flange is not forged from the block, material that is typically discarded may instead be used to form one of the first or second bodies  20  or  22 . If the bodies  20  and  22  are formed from the same material, the first and second body  20  and  22  may be forged from the same block. 
     After the bodies  20  and  22  are formed, the bores and openings described herein are machined into each body  20  and  22 . The studs  106 , as well as the internal components shown in  FIG. 3 , including the components  38 , retainer elements  40  and fastening system  42 , are next installed in the first body  20 . After the necessary bores have been formed in the second body  22 , the sealing arrangements  64 , retainer elements  68 , fastening system  70 , plungers  62  and packing nuts  72  described herein are installed. Prior to operation, the second body  22  is attached to the power end  12 , and the first body  20  is attached to the second body  22 . 
     During operation, the pumping of high pressure fluid through the fluid end  10  causes it to pulsate or flex. Such motion applies torque to the fluid end  10 . The amount of torque applied to the fluid end  10  corresponds to the distance between the power end  12  and the front side  50  of the fluid end: the moment arm. 
     In flanged fluid ends, such as the fluid end  300  shown in  FIGS. 14 and 15 , the applied torque is known to cause fatigue failures at the flanged connection point. A flanged connection point  310  is shown in  FIGS. 14 and 15 . Flanged fluid ends require space between the flange and the fluid end body to operate a wrench, as shown by a space  312  in  FIGS. 14 and 15 . Such space is not needed with the fluid end  10 . Thus, the moment arm associated with the fluid end  10  is decreased from that associated with flanged fluid ends. Therefore, less torque is applied to the fluid end  10  during operation than flanged fluid ends, which makes the fluid end  10  less susceptible to fatigue failures. 
     Turning to  FIGS. 11-13 , an alternative embodiment of a fluid end  200  is shown. The fluid end  200  comprises a first body  202  attached to separate second body  204 . The second body  204  is machined to have a lesser thickness than that of the second body  22 , shown in  FIGS. 1-2 . As described later herein, providing the second body  204  with a lesser thickness allows the first and second bodies  202  and  204  to be attached together using a single fastening system. 
     Continuing with  FIGS. 11-13 , the first and second bodies  202  and  204  each have a plurality of flat external surfaces  206  and  208 . The surfaces  206  and  208  may be rectangular in shape. The exterior surfaces  206  and  208  of each body  202  and  204  may be joined in the shape of a rectangular prism. However, the corner edges of such prism may be beveled. 
     With reference to  FIG. 13 , a plurality of rectilinear first bores  210 , one of which is shown in  FIG. 13 , are formed in the first body  202 . The plural bores  210  are arranged in side-by-side relationship. Each first bore  210  extends through the entirety of the first body  202 , interconnecting its top and bottom ends  212  and  214 . At each of its opposed ends  212  and  214 , the first bore  210  opens at the external surface  206 . 
     Adjacent the top end  212  of the first body  202 , each first bore  210  is closed by an installed component  213 . Each component  213  is releasably held within its first bore  210  by a retainer element  215  and fastening system  217 , as shown in  FIGS. 11-13 . The components  213 , retainer elements  215 , and fastening system  217  may be selected from those described in the &#39;126 Application. 
     Continuing with  FIG. 13 , a plurality of rectilinear second bores  216 , one of which is shown in  FIG. 13 , are formed in the first body  202 . The plural second bores  216  are arranged in side-by-side relationship. Each second bore  216  extends through the entirety of the first body  202 , interconnecting its front and back sides  218  and  220 . At each of its opposed sides  218  and  220 , each second bore  216  opens at the external surface  206 . The second bores  216  each intersect a corresponding one of the first bores  210 . Each second bore  216  may be disposed in orthogonal relationship to its intersecting first bore  210 . 
     Adjacent the front side  218 , each second bore  216  is closed by an installed component  221 , which may be identical to the component  213 . Each component  221  is releasably held within its second bore  216  by a retainer element  223  and fastening system  225 , as shown in  FIGS. 12 and 13 . The retainer element  223  may be identical to the retainer element  215 , and the fastening system  225  may be identical to the fastening system  217 . 
     Continuing with  FIG. 13 , a plurality of bores  222 , one of which is shown in  FIG. 13 , are formed in the second body  204 . The bores  222  are arranged in side-by-side relationship. Each bore  222  extends through the entirety of the second body  204 , interconnecting its front and back sides  224  and  226 . At each of its opposed sides  224  and  226 , each bore  222  opens at the external surface  208 . Each bore  222  formed in the second body  204  registers with a corresponding one of the second bores  216  formed in the first body  202 . When the bodies  202  and  204  are joined and aligned, each bore  222  becomes an extension of its associated second bore  216 . 
     With reference to  FIG. 12 , a plurality of bores  228  are formed in the outer periphery of the first body  202 . Each bore  228  includes a counterbore  230  positioned immediately adjacent the front side  218  of the first body  202 . The bores  228  are each alignable with a plurality of corresponding through-bores  232  formed about the periphery of the second body  204 , as shown in  FIGS. 11-12 . 
     A fastening system is used to secure the first body  202  to the second body  204 . The fastening system comprises a plurality of stay rods, similar to stay rods  18 , and a plurality of nuts and washers. The stay rods are installed within each aligned bore  228  and  232 . A nut and washer is torqued on the end of each stay rod within each corresponding counterbore  230 . The bodies  202  and  204  are attached such that the back side  220  of the first body  202  is in flush engagement with the front side  224  of the second body  204 . 
     Continuing with  FIG. 12 , in order for a stay rod to extend the length between the first and second bodies  202  and  204 , the second body  204  is machined to have a lesser thickness than the second body  22 , shown in  FIGS. 1-6 . Such decrease in size is possible because a plurality of sealing arrangements  234  used with the second body  204  are primarily positioned outside of the second body  204 , as shown in  FIG. 13 . Each sealing arrangement  234  comprises a stuffing box sleeve  236  that houses a series of packing seals  238 . The stuffing box sleeves  236  and packing seals  238  may be selected from those described in the &#39;126 Application. 
     As shown in  FIG. 13 , each bore  222  formed in the second body  204  includes a counterbore  242  that opens on the back side  226  of the second body  204 . A removable box gland  240  is closely received within each counterbore  242 . The removable box glands  240  are each tubular sleeves having open first and second ends  241  and  244 . Each second end  244  has a flanged outer edge  245  that is sized to be closely received within each counterbore  242 . Each sealing arrangement  234  is housed at least partially within a corresponding removable box gland  240 . 
     A plurality of openings  246  are formed in the flanged outer edge  245  of each box gland  240 . The openings  246  correspond with a plurality of openings (not shown) formed in a flat bottom  250  of each counterbore  242 . A plurality of fasteners may be installed within the opening  246  and the opening formed in the bottom  250 . When installed, the fasteners releasably secure each box gland  240  to the second body  204 . 
     Continuing with  FIG. 11-13 , a retainer element  252  and fastening system hold the sleeve  236  within the box gland  240  and aligned with bores  222  and  242 , as shown in  FIG. 13 . The retainer element  252  and fastening system may be the same as the retainer element  68  and fastening system  70 , as shown in  FIG. 3 . The seals  238  are compressed by a packing nut  254  threaded into an associated retainer element  252 , as shown in  FIG. 13 . A plunger  258  is installed within each pair of aligned bores  216  and  222 . 
     Several kits are useful for assembling the fluid end  200 . A first kit comprises the first body  202  and the second body  204 . The first kit may also comprise the fastening system described with reference to  FIG. 13  to attach the bodies  202  and  204 . The first kit may further comprise the components  213  or  221 , removable box glands  240 , sealing arrangements  234 , retainer elements  215 ,  223  or  252 , fastening system  217 ,  225  or the fastening system used with the box gland  240 , packing nuts  254 , and/or plungers  258 , described herein. 
     The bodies  202  and  204  may be formed of the same material as the bodies  20  and  22 . Likewise, the bodies  202  and  204  may be manufactured in the same manner as the bodies  20  and  22 . 
     The plurality of washers used with each fastening system  92  and  104 , shown in  FIGS. 3-6, 9 and 10 , may be configured to allow a large amount of torque to be applied to the nuts without using a reaction arm. Instead, the washer itself may serve as the counterforce needed to torque a nut onto a stud. Not having to use a reaction arm increases the safety of the assembly process. The same is true for the washers that may be used with the fastening system described with reference to  FIG. 12 . 
     The nuts used with the fastening systems  92  and  104  may also comprise a hardened inner layer to help reduce galling between the threads of the nuts and studs during the assembly process. The same is true for the nuts that may be used with the fastening system described with reference to  FIG. 12 . An example of the above described washers, nuts, and methods are described in Patent Cooperation Treaty Application Serial No. PCT/US2017/020548, authored by Junkers, et al. 
     Changes may be made in the construction, operation and arrangement of the various parts, elements, steps and procedures described herein. For example, certain embodiments of the second fluid end body piece (or pieces) are described above as “flangeless.” In other embodiments, a minimally flanged fluid end body piece may also be utilized. Consider the surface dimension of the wider portion of the flanged piece to the narrower portion of the piece-for example, the height of the portion of flange  302  in  FIG. 14  to the height of the narrower portion that engages with the first body piece. In one set of embodiments, the ratio r of the height (or other corresponding surface dimension) of the narrower portion to the height (or other corresponding surface dimension) of the wider portion may be 0.90&lt;r&lt;1.0; in other embodiments the ratio r may be 0.95&lt;r&lt;1.0.