Patent Publication Number: US-2019170137-A1

Title: Header ring

Description:
BACKGROUND 
     High pressure reciprocating pumps are often used to deliver high pressure fluids during earth drilling operations. A sealing arrangement is provided between a pump casing and a reciprocating plunger to reduce the likelihood of leakage and to protect the plunger from potential damage from any abrasive components that may be contained in the fluid being pumped. 
     The sealing arrangement can include a header ring, such as the header ring shown in U.S. Pat. No. 9,534,691. The header ring disclosed in some embodiments of the &#39;691 Patent is described as an annular body portion which is primarily made of a homogeneous elastomeric material. Bonded to the homogeneous elastomeric portion of body is an annular layer of a fabric reinforced elastomer, the layer covering the surfaces of a pedestal, a sealing lip, a bead and portions of the forward and rearward portions of the body forming surface. 
     SUMMARY 
     The invention provides, in a first embodiment, a reciprocating pump. The reciprocating pump includes a casing defining a pumping chamber, a plunger configured to reciprocate in an axial direction within the pumping chamber along a plunger axis, and an annular header ring positioned between the plunger and the casing. The annular header ring is formed solely of a fabric-reinforced rubber. 
     The invention provides, in another embodiment, an annular header ring defining a central axis. The annular header ring includes a first axial side, a second axial side opposite the first axial side, a first radial side extending between the first and second axial sides and defining an inside diameter of the annular header ring, and a second radial side extending between the first and second axial sides and defining an outside diameter of the annular header ring. The annular header ring is a body uniformly constructed entirely of a fabric-reinforced rubber. 
     The invention provides, in yet another embodiment, a method of forming an annular header ring. A rubber material is mixed with a fabric material to form a fabric-reinforced rubber having fabric fibers. The fabric-reinforced rubber is cut into sheets on a bias, turning the fabric fibers to an offset angle. The sheets of the fabric-reinforced rubber are joined, and the rejoined sheets are cut into ribbons. The ribbons are stacked or coiled into a preform. The preform is compressed in a mold chamber of a compression mold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a reciprocating pump including a fluid end. 
         FIG. 2  is a section view of the reciprocating pump of  FIG. 1 . 
         FIG. 3  is an enlarged view of the packing arrangement. 
         FIG. 4  is an enlarged cross section of a header ring taken along a plane that is parallel to the plunger axis. 
         FIG. 5  is a perspective view of a fabric or cloth reinforced elastomeric material for producing the header ring of  FIG. 4 . 
         FIG. 6  is an enlarged view of an alternative packing arrangement. 
         FIG. 7  is an enlarged view of yet another packing arrangement. 
         FIG. 8  is a cross-sectional view of compression molding plates. 
         FIG. 9  is a cross-sectional view of a header ring formed by the compression molding plates. 
         FIG. 10  is a cross-sectional view of a header ring having a modified inner surface. 
     
    
    
     Before any embodiments of the disclosure are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of supporting other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a reciprocating pump  100  including a power end  102  and a fluid end  104 . The power end  102  includes a crankshaft that drives a plurality of reciprocating plungers within the fluid end  104  to pump fluid at high pressure. 
       FIG. 2  is a section view taken through the central or plunger axis  210  of one of the plungers  202 . Each of the pumping chambers  208  of the reciprocating pump  100  includes a plunger  202  that reciprocates within a casing  206  of the fluid end  104 . With each stroke of the plunger  202 , low pressure fluid is drawn into the pumping chamber  208  and high pressure fluid is discharged. 
     A packing arrangement  204  is positioned between the casing  206  and the plunger  202  to form a seal therebetween. The fluid within the pumping chamber  208  often contains abrasive material that can damage the packing arrangement  204  and the plunger  202  if not sealed properly. 
     As illustrated in  FIG. 3  the packing arrangement  204  is disposed within a packing box  322  that is formed as part of the casing  206  of the fluid end  104 . The packing arrangement  204  includes a junk ring  302 , a first support ring  304 , a header ring  306 , a first pressure ring  308 , a second pressure ring  310 , a second support ring  312 , a lantern ring  314 , and a packing nut  320 . 
     Before discussing the packing arrangement  204  in detail it is important to understand the terms “upstream” and “downstream”. Any flow through the packing arrangement  204  or between the packing arrangement  204  and the plunger  202  flows from a high pressure side  324  of the packing box  322  to a low pressure side adjacent the packing nut  320 . Thus, upstream would be in the direction away from the packing nut  320  while downstream would be in a direction toward the packing nut  320 . 
     The junk ring  302  is positioned within the packing box  322  adjacent the high pressure end  324  and is preferably made of a hard material such as steel. The junk ring  302  is annular in shape with a cylindrical inside surface and a cylindrical outside surface. The junk ring  302  includes a planar lead surface that abuts a planar surface that defines the high pressure end  324  of the packing box  322 . Opposite the planar surface is a male chevron portion that faces toward the low pressure end  326  of the packing box  322 . 
     The first support ring  304  is annular in shape and includes a cylindrical inner surface that abuts the plunger  202  and a cylindrical outer surface that abuts the wall of the packing box  322 . The first support ring  304  also includes a female chevron portion that faces the high pressure end  324  and abuts the male chevron portion of the junk ring. A male chevron portion is positioned opposite the female chevron portion and faces toward the low pressure end  326 . In preferred constructions, the first support ring  304  is manufactured from a material such as polyether ether ketone (PEEK). 
     The header ring  306  is positioned on the low-pressure side of the first support ring  304  and on the high pressure side of the first pressure ring  308 . Alternatively, the header ring  306  may be positioned between the first and second pressure rings  308 ,  310 . The header ring will be discussed in greater detail with regard to  FIG. 4 . As a further alternative, as shown in  FIGS. 6-7 , the header ring may abut directly against the junk ring  302  or directly against the high pressure end of the packing box  322  (i.e., the high pressure end of the casing  206 ) without a junk ring  302  or first support ring  304  therebetween. 
     The first pressure ring  308  is an annular ring that includes a cylindrical inner surface that abuts the plunger  202  and a cylindrical outer surface that abuts the bore of the packing box  322 . A high pressure side of the first pressure ring  308  includes a female chevron portion arranged to receive the male chevron portion of the header ring  306 . An aperture  328  is formed in the female chevron portion and provides a relief should the arms of the female chevron portion be forced apart. A male chevron portion, opposite the female portion extends toward the low pressure end  326  of the packing box  322 . In preferred constructions, the first pressure ring  308  is formed from an elastomer impregnated aramid fabric. 
     The second pressure ring  310  is identical to the first pressure ring  308  and the second support ring  312  is identical to the first support ring  304 . The second support ring  312  is positioned on the low pressure side of the second pressure ring  310 . 
     The first and second pressure rings  308 ,  310  are the primary sealing components of the packing arrangement, bearing the brunt of the pressure applied by the high-pressure fluid within the pumping chamber  208 . Therefore, the pressure rings  308 ,  310  are stiff or inflexible and lack springiness (relative to the header ring  306 ). 
     The lantern ring  314  is an elongated annular ring that includes an inner cylindrical surface that abuts the plunger and an outer cylindrical surface that abuts the surface of the packing box  322 . The high pressure side of the lantern ring  314  includes a female chevron portion that is arranged to receive the male chevron portion of the second support ring  312 . One or more lube oil bores  318  pass between the inner surface and the outer surface and provide a flow path for lube oil that is delivered to the packing arrangement  204  via the lube oil passage  316 . In preferred constructions, the lantern ring  314  is formed from a metal such as aluminum, bronze, or an aluminum-bronze alloy. 
     Lube oil can be provided to the packing arrangement  204  via the lube oil passage  316  and the lube oil bore  318 . The lube oil creates a pressure seal that enhances the function of the packing arrangement  204  while provided lubrication between the plunger  202  and the packing arrangement  204 . 
     The packing nut  320  threadably engages the casing  206  and is movable between a first position and a second position in which the packing nut  320  compresses the lantern ring  314  against the stack including the second support ring  312 , the second pressure ring  310 , the first pressure ring  308 , the header ring  306 , the first support ring  304 , and the junk ring  302 . Collectively, the components of the packing arrangement  204  are compressed in the direction of the piston axis by the packing nut  320 , expanding radially to better contact the outer wall or bore of the packing box  322  and the outer surface of the plunger  202 . 
     As illustrated in  FIG. 4  the header ring  306  includes an annular outer surface  402  sized to abut the surface of the packing box  322 . An inner surface  404  defines a minimum inside diameter  412  that is preferably smaller than the outside diameter of the plunger  202  to assure solid contact with the plunger  202  to improve the seal. A first portion of the inner surface  404  is non-cylindrical and is defined by the revolution of a curved line about the center line of the header ring  306 . The inner surface  404  further includes a second portion—an annular step or cutout  414 , adjacent a high pressure side  408  of the header ring  306 . The cutout  414  may be adjacent to the first portion or may otherwise extend partially into the curved line defined by the first portion. 
     A low pressure side of the header ring  306  includes a male chevron portion and a knob portion  406  extending from the male chevron portion toward the low pressure end  326  of the packing box  322 . The knob portion  406  is sized to be received in the aperture  328  of the first pressure ring  308  when the packing arrangement  204  is assembled. 
     The high pressure side  408  of the header ring  306  includes a surface portion that is shaped to mate with the adjacent surface. As shown in  FIGS. 4, 6, and 7 , the high pressure side  408  of the header ring  306  is relatively flat to mate with the high pressure end of the packing box  322  or the low pressure side of the junk ring  302 . Alternatively, as shown in  FIG. 3 , the high pressure side of the header ring  306  may include a female chevron portion sized to engage the male chevron portion of the first support ring  304 . 
     The header ring  306  has greater elasticity than the pressure rings  308 ,  310  to maintain a constant force on the pressure rings  308 ,  310  when assembled in the packing arrangement  204 . Specifically, when the packing nut  320  is threaded to the casing  206 , the nut  320  compresses the rings  306 ,  308 ,  310 . The header ring  206  provides flexibility to compensate for minor compression fluctuations to maintain a constant axial force on the pressure rings  308 ,  310  for sealing. 
       FIG. 10  illustrates a header ring  306  having a modified geometry. Specifically, the header ring includes a radial step or cutout  1034  between the inner surface  404  and the axial step  414 . The step cutout formed by the radial and axial steps  1034 ,  414  may increase the flexibility of the inner surface  404  that contacts the plunger  202 . 
     The header ring  306  is formed entirely of a cloth or fabric reinforced elastomeric material, such as a fabric reinforced rubber, and more specifically an aramid reinforced rubber. The annular outer surface  402 , the inner surface  404 , the low pressure side including the knob portion  406 , and the high pressure side  408  of the header ring  306  are formed of the fabric reinforce rubber. Further, the area between the aforementioned surfaces  402 ,  404 ,  406 ,  408  is likewise made of the same fabric reinforced material. In other words, the header ring  306  is a body uniformly constructed entirely from the fabric reinforced elastomeric material without the presence of other dissimilar materials embedded within the body or forming outer layers of the body. Common trade names for aramid fabrics include Kevlar, Nomex, and Twaron. 
     To form the fabric reinforced rubber into the header ring  306 , a rubber material (e.g., hydrogenated nitrile butadiene rubber) is mixed with a fabric. The rubber material may be calendered (i.e., via a calender machine using rollers to smooth and thin the material) with the fabric to specification (e.g., with a 35-75 percent rubber pickup, with a 55-65 percent rubber pickup). The roll of rubber-fabric is then cut into sheets on a bias to turn the fabric fibers to an offset angle. The bias cut sheets are joined back together, and cut into ribbon. That ribbon is then turned on edge and stacked or coiled into the preform, as shown in  FIG. 5 . 
     Alternatively, the reinforced rubber may be formed via a dip coating or solution coating process. In the dip coating process, the rubber material is dissolved in an applicable solvent for the particular rubber chemistry, or is otherwise converted into a liquid or low viscosity flowable state using an organisol or plasticol. The liquid rubber is then applied to the fabric. The fabric may be pulled through the liquid rubber, or alternatively, the liquid may be applied via a spray coat (e.g., using pneumatic spray equipment, airless sprayers, etc.). Further still, the liquid rubber may be applied via a transfer roll mechanism in which the liquid is applied to the roll and the roll contacts with the fabric to transfer the liquid to the fabric. With a transfer roll mechanism, the coat weight is controlled by varying the roll speed relative to the fabric speed. Once the fabric has been coated, it passes into an oven to remove the solvent or gel the rubber into the fabric, thereby producing the solid rubber-fabric composite. The rubber-fabric material is then rolled and cut as described above. 
     The preform is placed into a mold chamber of a compression mold, such as the mold  510  shown in  FIG. 8 . As shown, the compression mold includes three mold components  510 A,  510 B,  510 C that collectively define the mold chamber. Pressure is applied to the mold components  510 A,  510 B,  510 C such that the fabric reinforced rubber is forced into contact with all areas within the mold chamber. As shown in  FIG. 9 , the fabric reinforced rubber is molded to the finished shape, producing the header ring  306 . Some flashing may be produced in the molding process, which can be removed via a post-processing step. 
     Other header rings may be formed of a homogeneous elastomeric material or may include a fabric-reinforced layer covering surfaces of a homogenous elastomeric material. Such header rings lack advantages of the header ring  306  discussed above. Specifically, a purely elastomeric header ring lacks the strength and wear resistance provided by the fabric reinforcement. Further, coating a homogeneous elastomeric material with a fabric-reinforced layer only provides limited advantages over the bare homogenous elastomeric material core. Specifically, the interface between the coating and the core provides an additional point of failure for the header ring. Further, as the plunger reciprocates against the header ring, the coating applied to the core can shear away from the core as the fibers of the coating that contact the reciprocating plunger are oriented substantially parallel to the axial direction defined by the movement of the plunger. 
     In contrast to the other header rings described above (i.e., the purely elastomeric header ring and the header ring having a fabric-reinforced coating), the header ring  306  is formed solely of the fabric-reinforced rubber, such that there is no interface within the header ring  306  that is parallel to the axial direction at or adjacent to the inner surface  404  (that contacts the plunger  202 ) of the header ring  306 . Further the manufacturing processes utilized to form the header ring orient the fibers of the fabric-reinforced material perpendicular to the axial direction (i.e., the direction of travel of the plunger  202 ), thereby increasing the shear strength of the header ring  306  in the contact region of the inner surface  404 . 
     Experimental testing has been conducted to compare the reliability of the fabric-reinforced rubber header ring  306  described above to an elastomeric header ring having a fabric-reinforced coating. Running at 9500 psi, the fabric-reinforced rubber header ring  306  experienced a failure rate of 2.5 percent after 144 stages. In comparison, the elastomeric header ring having a fabric-reinforced coating experienced a failure rate of 71.1 percent after the same number of stages. The fabric-reinforced rubber header ring  306  was tested to have an average life approximately five times greater than the average life of the elastomeric header ring having a fabric-reinforced coating. A second test was conducted at 10,200 psi with a 100 percent failure rate at 35 hours of the elastomeric header ring having a fabric-reinforced coating. The fabric-reinforced rubber header ring  306  had no failures when the test concluded at 138 hours. Increasing the average life of the header ring decreases downtime of the reciprocating pump  100  and likewise decreases maintenance work.