Abstract:
There are a number of applications today where the pumping of abrasive slurries is necessary. The pumping mechanisms, though, can be complex, employing multiple transfer cylinders and movable pipes. These designs have their problems, specifically wear between poorly sealing surfaces. To reduce this problem, seals are provided that have multiple wear surfaces which include harder tiles secured over a softer core to benefit from the relative hardness or flexibility of each of the respective materials.

Description:
CLAIM OF PRIORITY  
       [0001]     This application claims priority from U.S. Provisional Patent Application No.  60 / 734 , 487  entitled “SEALING RINGS FOR ABRASIVE SLURRY PUMPS” filed on behalf of Alan Kirkland, on Nov. 8, 2005, which is incorporated herein by reference for all purposes. 
     
    
     TECHNICAL FIELD  
       [0002]     The invention relates generally to a wear ring and, more particularly, to a wear ring for use in pumping viscous and abrasive fluids, namely cement slurries.  
       BACKGROUND  
       [0003]     In concrete pumping applications, a common feature is the use of a multi-cylinder pump. A hydraulic actuator alternates piping between different cylinders. This configuration, though, does not lend itself to utilizing particular fittings that tightly seal the cylinders to the sections of piping. Moreover, it is well known that abrasive slurries are notorious for excessively wearing piping, fittings, and seals. Hence, when loose fitting seals, as with multi-cylinder pumps, are employed, the likelihood of both wear and failure dramatically increases because of the increased number of wearing surfaces.  
         [0004]     One conventional solution is to employ a generally uniform hard seal or ring. The seal can be made of a variety of hard materials, such as tungsten carbide. Hard material can withstand a substantial amount of abuse from abrasive slurries. However, the hardness of the material generally results in a brittle material, one that is subject to fracture. Fractures can cause the seal to fail. Therefore, hard materials lack the inherent flexibility of softer materials, but are better equipped to withstand abrasion than softer materials.  
         [0005]     Oftentimes, however, as a hydraulic actuator alternates piping between the different cylinders, the abrasive slurry is sheared. Typically, the shearing of the abrasive slurry, like concrete, causes stones and other abrasive components contained in the abrasive slurry to be sheared as well. Thus, by shearing the abrasive slurry, it is not uncommon to fracture very hard materials that provide seals between the sections of piping. However, if the hard materials are replaced with a softer material to avoid fracturing, then the good sealing properties of the harder materials can be lost.  
         [0006]     Therefore, there is a need for a method and/or apparatus for efficiently sealing abutted pipes in abrasive and viscous fluid pumping applications that provides both a good seal and the ability to withstand the shearing of abrasive slurries.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention, accordingly, provides a pipe seal for an abrasive materials pump. A core base ring is formed of a first material selected for strength and fracture toughness. Specifically, the core base ring has at least one aperture, a front side, and a rear side. A plurality of tiles of a first size, formed of a second material, are arranged along an inner surface of the at least one aperture. Also, a plurality of tiles of a second size, formed of a third material, are arranged along the perimeter of the aperture on at least the front side. Additionally, a plurality of tiles of additional sizes, formed of a fourth material, are arranged along at least a portion of the remainder of the front side. Moreover, the fourth material is harder than the first material, and the second material is harder than the fourth material. The third material is also harder than the second material.  
         [0008]     In an alternative embodiment of the present invention, an improved pump assembly for moving abrasive slurries is also provided. A pair of slurry conduits are provided where each conduit has a circular opening. A transfer conduit is also provided where the transfer conduit has a circular opening. The opening of the transfer conduit is also movable between the openings of each of the pair of conduits to establish fluid communication between one of the slurry conduits and the transfer conduit. A seal ring associated with at least one of the openings in the slurry and transfer conduits is also included. This seal ring comprises a core base ring, a plurality of tiles of a first size, a plurality of tiles of a second size, and a plurality of tiles of additional sizes. The core base ring is formed of a first material selected for strength and fracture toughness. Specifically, the core base ring has at least one aperture, a front side, and a rear side. A plurality of tiles of a first size, formed of a second material, are arranged along an inner surface of the at least one aperture. Also, a plurality of files of a second size, formed of a third material, are arranged along the perimeter of the aperture on at least the front side. Additionally, a plurality of files of additional sizes, formed of a fourth material, are arranged along at least a portion of the remainder of the front side. Moreover, the fourth material is harder than the first material, and the second material is harder than the fourth material. The third material is also harder than the second material.  
         [0009]     In yet another alternative embodiment of the present invention, a seal for an abrasive slurry pump assembly is provided. There is a core base plate formed of a first material selected for strength and fracture toughness having a front side and a rear side, said core plate having two or more ring shaped apertures of at least one selected inner diameter therein which extend from said front side to said rear side. Additionally, there is a plurality of first tiles formed of a second material arranged around each inner diameter of each of said ring shaped apertures, and there is a plurality of second tiles formed of a third material arranged to at least partially covering the front side. The third material is also harder than the first material, while the third material is harder than the second material.  
         [0010]     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:  
         [0012]      FIG. 1  is an isometric view of a multi-cylinder abrasive slurry pump utilizing wear rings in accordance with a preferred embodiment of the present invention;  
         [0013]      FIG. 2  is an isometric view of a wear ring of  FIG. 1 ;  
         [0014]      FIG. 3  is a front view of the wear ring of  FIG. 1 ;  
         [0015]      FIG. 4  is a side view of the wear ring of  FIG. 1 ;  
         [0016]      FIG. 5  is an isometric view of a multi-cylinder abrasive slurry pump utilizing a wear plate in accordance with a preferred embodiment of the present invention;  
         [0017]      FIG. 6  is an isometric view of a wear plate of  FIG. 5 ; and  
         [0018]      FIG. 7  is a front view of the wear plate of  FIG. 5 . 
     
    
     DETAILED DESCRIPTION  
       [0019]     Refer now to the drawings wherein depicted elements are, for the sake of clarity, not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views.  
         [0020]     A multi-cylinder concrete pump is the application for the wear ring  100  of the present invention, as required by the operation of the pump. As can be seen in  FIG. 1 , a multi-cylinder pump  300  employs two wear rings  100 , which are in accordance with a preferred embodiment of the present invention.  
         [0021]     Specifically, the pump  300  includes a pivot pipe  302  and a cylinder plate  304 . The cylinder plate  304  enables the pivot pipe  302  to move between supply pipes  306  and  308 . However, because of the problems associated with abrasion resulting from fluid contact with the concrete or other abrasive slurry, wear rings  100  are included on the face of the cylinder plate  304  and the pivot pipe  302 . In other words, the inner face tiles  106  and the outer face tiles  108  of the wear rings  100  of cylinder plate  304  and of the pivot pipe  302  face one another. Thus, a hard wear surface is provided where there is a poor seal between the pivot pipe  302  and supply pipes  306  and  308 .  
         [0022]     Referring to FIGS.  24  of the drawings, the reference numeral  100  generally designates a wear ring embodying features of the present invention. The wear ring  100  comprises a core base ring  102 , circumferential tiles  104 , inner face tiles  106 , and outer face tiles  108 .  
         [0023]     Generally, the wear ring  100  is formed to operate as a seal between two connecting pipes, one of which is movable relative to the other. Because the openings of the pipes slide past one another, there is considerable opportunity for abrasive wear. Specifically, the main wearing surface is located along the inner radius r 1  of the wear ring  100 , where continuous fluid contact with the abrasive slurry, such as concrete, occurs. However, because of the design, the front face  116  is also a surface that endures a substantial amount of wear.  
         [0024]     Underlying the wear ring  100  is the core base ring  102 . The core base ring  102  usually forms the majority of the volume of wear ring  100 . Typically, the core base ring  102  is formed of a relatively soft material, such as steel, that includes an inherent flexibility, strength, and ductility. Specifically, a material used for the core base ring  102  is chosen based on its fracture toughness, which is typically greater than 30 MPa-m 1/2  at standard temperature and pressure. Additionally, the hardness of the material of the core base ring  102  is about HRC  20  to about HRC  40 .  
         [0025]     Formed within the core base ring  102  are a number of grooves. An annular groove  110  is formed along the inner radius r 1  at nearly the depth of the core base ring  102 . A first surface groove  112  is also formed on the front face  116  of the core base ring  102  beginning at a radius r 2 , and a second surface groove  114  is formed on the front face  116  beginning at a radius r 3 . Relative to one another, the first surface groove  112  is radially wider and shallower than the second surface groove  114 .  
         [0026]     First surface groove  112  and second surface groove  114  are employed to house hard tiles. In particular, inner face tiles  106  are placed within the first surface groove  112 , and the outer face tiles  108  are placed within the second groove  114 . The inner face tiles  106  and the outer face tiles  108 , too, are made of a material that is harder than the material comprising the core base ring  102 . Typically, tungsten carbide, tantalum carbide, as well as other hard metals, carbides, and ceramics are employed to form the circumferential tiles  104 . Due to the increased hardness, there is also less emphasis on a need for a material with a relatively high fracture toughness. In fact, a material employed for the tiles can be chosen to have a fracture toughness of less than 10 MPa-m 1/2 . Moreover, the inner face tiles  106  and the outer face tiles  108  are typically secured into place by gluing, brazing, soldering, or welding. Therefore, a good sealing surface is provided by the inner face tiles  106  and the outer face tiles  108  due to their particular hardnesses. The inner face tiles  106  can also be arranged to extend to the aperture. Typically, the hardness of the inner face tiles  106  is about HRA  80  to about HRA  95 . Additionally, the hardness of the outer face tiles  108  is about HRA  70  to about HRA  90 .  
         [0027]     Located within the annular groove  110  are a plurality of circumferential files  104 . The circumferential tiles  104  are longitudinally arranged around inner radius r 1 . In other words, the circumferential files  104  are arranged such that the longest dimension of each generally rectangular file is orthogonal to inner radius r 1  to provide a substantially continuous wear surface. Typically, too, the circumferential files  104  can be arranged to extend to the front face  116  in order to cover the edges of the inner face tiles  106 . These circumferential tiles  104  are made of a material that is harder than the material comprising the core base ring  102 . Typically, tungsten carbide, tantalum carbide, as well as other hard metals, carbides, and ceramics are employed to form the circumferential tiles  104 . Due to the increased hardness, there is less emphasis on a need for a material with a relatively high fracture toughness. In fact, a material employed for the files can be chosen to have a fracture toughness of less than 10 MPa-m 1/2 , and the hardness of the circumferential tiles  104  is typically between about HRA  70  and HRA  90 . Moreover, the circumferential tiles  104  are typically secured into place by gluing, brazing, soldering, or welding.  
         [0028]     Specifically, in arranging tiles of varying hardnesses, there are several configurations that can be employed. For example, in one configuration, the materials of the core base ring  102 , of the outer face files  108 , of the circumferential files  104  and of the inner face tiles  106  have hardnesses that are about HRC  30 , about HRA  83 , about HRA  86 , and about HRA  90 , respectively. In an alternative example, the materials of the core base ring  102  and of the inner face tiles  106  have hardnesses that are about HRC  30  and about HRA  90 , respectively, while the outer face files  108  and the circumferential tiles  104  have hardnesses of about HRA  84 .  
         [0029]     The combination of employing a softer and more elastic inner core surrounded by a number of harder files allows for a very wear resistant sealing ring. The use of covering tiles with varying hardnesses relative to one another provides an abrasion-resistant surface that can resist abuse sustained by fluid contact with and shearing of abrasive slurries, such as concrete, that would otherwise cause other seals to wear more quickly or fracture more often. To reduce fracturing, the harder files “float” on the softer inner base core ring  102 . This ability to “float” means that impacts that result in use will not necessarily fracture the hard tiles. Additionally, the circumferential tiles  104  and the outer face tiles  108  are softer relative to the inner face tiles  106 . The inner face tiles  106  are comprised of a very hard material sufficient to resist abrasion, but has a higher likelihood of fracture when shearing forces are applied. The circumferential tiles  104  and the outer face tiles  108 , themselves, are less effective at providing a seal than the inner face tiles  106 , but are of sufficient softness to better resist fracturing that results from shearing abrasive slurries. Thus, circumferential tiles  104  and the outer face tiles  108  protect the inner face tiles  106 .  
         [0030]     Therefore, the wear ring  100  provides several benefits over prior-art designs. In particular, the wear ring  100  takes advantage of the hardness of tiles while also taking advantage of the flexibility of softer materials. Moreover, by utilizing tiles instead of an entire wear ring comprised of harder material, tiles can be individually replaced if, and when, fracture of particular tiles occurs. Hence, it is possible to refit the wear ring  100  several times during its lifetime, which reduces the overall cost to the user of the wear ring  100 .  
         [0031]     Alternatively, in another preferred embodiment of the present invention, a pair of cylinders can be fitted with a single wear plate  200 , as can be seen in  FIGS. 5-7 . In many cases, a pair or multiple pairs of cylinders are utilized. In these cases, not only are the wear rings subject to wear from the abrasive slurry, but intermediate plate surfaces may be subject to wear as well.  
         [0032]     Turning to  FIGS. 5-7  of the drawings, a multi-cylinder pump  300  employs wear plate  200 , which is in accordance with a preferred embodiment of the present invention where the wear plate  200  comprises a core base plate  202 , ring tiles  204 , and intermediate tiles  206 .  
         [0033]     Specifically, the pump  300  includes a pivot pipe  302  and a cylinder plate  304 . The cylinder plate  304  enables the pivot pipe  302  to move between supply pipes  306  and  308 . However, because of the problems associated with abrasion resulting from fluid contact with the concrete or other abrasive slurry, wear plate  200  is included on the face of the cylinder plate  304  while a wear ring  100  is provided on the end of the pivot pipe  302 . In other words, both the ring tiles  204  and the intermediate tiles  206  face in the direction of the pivot pipe  302 . Thus, a hard wear surface is provided where there is a poor seal between the pivot pipe  302  and supply pipes  306  and  308  and where there is frictional contact with the pivot pipe  302 .  
         [0034]     Underlying the wear plate  200  is the core base plate  202 . The core base plate  202  includes two wear rings: first wear ring  208  and second wear ring  210 . Between the first wear ring  208  and the second wear ring  210  is the intermediate plate surface  212 . Typically, the core base plate  202  is comprised of a soft material, such as steel, that includes an inherent flexibility. Specifically, a material used for the core base plate  202  is chosen based on its fracture toughness, which is typically greater than 30 MPa-m 1/2  at standard temperature and pressure.  
         [0035]     Secured to the front face  214  of the core base plate  202  are hard tiles. In particular, each of the first wear ring  208  and the second wear ring  210  have inner radii r 4  and r 5 , respectively. Secured along the inner radii r 4  and r 5  of the first wear ring  208  and the second wear ring  210  are ring tiles  204 , which form a nearly uniform surface along the circumference of the inner radii r 4  and r 5 . Without additional coverage by other tiles, intermediate plate surface  212  remains exposed, but intermediate tiles  206  are secured to the front face  214  of the core base plate  202  on the intermediate plate surface  212  to provide the additional coverage. Thus, most of the front face  214  of the core base plate  202  is covered by hard tiles.  
         [0036]     The hard material that comprises the ring tiles  204  and the intermediate tiles  206  is, typically, tungsten carbide, tantalum carbide, as well as other hard metals, carbides, and ceramics. Due to the increased hardness, there is less emphasis on a need for a material with a relatively high fracture toughness. In fact, a material employed for the tiles can be chosen to have a fracture toughness of less than 10 MPa-m 1/2 . However, the ring tiles  204  are softer relative to the intermediate tiles  206 . Specifically, the ring tiles  204  have a hardness from about HRA  70  to HRA  90  while the intermediate tiles  206  have a hardness of about HRA  80  to about HRA  95 . The ring tiles  204 , themselves, are less effective at providing a seal than the intermediate tiles  206 , but are of sufficient softness to better resist fracturing that results from shearing abrasive slurries. Moreover, these tiles  204  and  206  are typically secured into place by gluing, brazing, soldering, or welding.  
         [0037]     Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.