Patent Publication Number: US-8534184-B2

Title: Replaceable sleeve for a cylinder liner

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Application No. 61/119,189, filed Dec. 2, 2008, entitled “Replaceable Sleeve For A Cylinder Liner.” 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     The disclosure relates generally to mud pumps. More particularly, the disclosure relates to cylinder sleeves of mud pumps. Still more particularly, the disclosure relates to a replaceable cylinder sleeve, and applying radially compressive pre-load to the replaceable sleeve. 
     2. Background of the Disclosure 
     In extracting hydrocarbons from the earth, it is common to drill a borehole into the earth formation containing the hydrocarbons. A drill bit is attached to a drill string, and during drilling operations, drilling fluid, or “mud” as it is also known, is pumped down through the drill string and into the hole through the drill bit. Drilling fluids are used to lubricate the drill bit and keep it cool. The drilling mud also cleans the bit, balances pressure by providing weight downhole, and brings sludge and cuttings created during the drilling process up to the surface. Finally, the drilling fluid can reveal the presence of oil, gas or water that may enter the fluid from a formation being drilled and may reveal information about the formation through drill cuttings. A viscous drilling fluid is capable of transporting more and heavier cuttings, so viscous drilling fluid can be advantageous, and often additives are utilized to increase viscosity. 
     Slush or mud pumps are commonly used for pumping the drilling mud. The pumps used in these applications are reciprocating pumps typically of the duplex or triplex type. A duplex pump has two reciprocating pistons that each force drilling mud into a discharge line, while a triplex reciprocating pump has three pistons that force drilling mud into a discharge line. These reciprocating mud pumps can be single acting, in which drilling mud is discharged on alternate strokes, or double acting, in which each stroke discharges drilling mud. 
     The pistons and cylinders used for such mud pumps are susceptible to a high degree of wear during use because the drilling mud is relatively dense and has a high proportion of suspended abrasive solids. This translates into a relatively short lifetime of the cylinder and necessitates frequent replacement of the cylinder. As the cylinder in which the piston reciprocates becomes worn, the small annular space between the piston head and the cylinder wall increases substantially and sometimes irregularly. This decreases the efficiency of the pump. To counteract the effect of this wear, mud pumps typically utilize of an expendable cylinder liner apparatus. 
     The general construction of a mud pump cylinder liner apparatus involves using three pieces of tubular material: a sleeve, a hull, and a collar. The sleeve forms the inside surface of the liner apparatus, the hull is assembled by shrink fit over the sleeve, and the collar is a flange ring that is shrink fit around the hull and normally retains the liner apparatus in the mud pump cylinder. The shrink fit between the sleeve and the hull creates a mechanical radial compressive pre-load on the sleeve and serves to counteract the effects of the alternating axial compressive forces and internal pressures on the cylinder sleeve which can lead to fatigue and failure of the cylinder sleeve and necessitate the replacement of the cylinder liner apparatus. 
       FIG. 1  illustrates an embodiment of a prior art cylinder liner apparatus  10  and includes clamping collar  20 , cylinder hull  30 , and sleeve  40 . A central axis  15  passes through the longitudinal center of cylinder liner assembly  10 . Annular clamping collar  20  is centered about central axis  15  and includes a collar bore  22  having an inner diameter  24 . Cylinder hull  30  is concentrically disposed within collar bore  22  of clamping collar  20  to secure apparatus  10  to a fluid side of an existing mud pump module. Cylinder hull  30  includes a hull wall  32  having an outer diameter  34  and a hull bore  36  having an inner diameter  38 . Further, hull wall  32  outer diameter  34  is larger than inner diameter  24  of collar bore  22  in clamping collar  20 . Sleeve  40  is concentrically disposed within cylinder hull  30 . Further, sleeve  40  includes a sleeve wall  42  with an outer diameter  44  that is larger than inner diameter  38  of cylinder bore  36  in cylinder hull  30 , and an inner bore  41  for receiving the pump piston. 
     The motion of the reciprocating pump piston subjects the cylinder sleeve to alternating axial forces and internal pressures. The alternating internal pressures translate to alternating radial stresses in the cylinder sleeve that can lead to metal fatigue from the cyclic loading and sudden changes in direction of the piston motion. To counteract the effects of fatigue, radial compressive pre-load is applied to the cylinder sleeve such that the alternating internal pressure creates less fatigue stress in the sleeve than a sleeve with no pre-load. The radial compressive stresses are critical to ensure that the sleeve resists cyclic fatigue due to the cyclic pressures of the operating pump. 
     The method of imparting radial compressive pre-load using the prior art cylinder liner apparatus  10  includes heating cylinder hull  30  until inner diameter  38  of hull bore  36  is greater than outer diameter  44  of sleeve  40 , then inserting sleeve  40  into hull bore  36 . Next, cylinder hull  30  is cooled causing cylinder hull  30  to contract and decrease inner diameter  38  and radially contact and compress sleeve  40 . Then, clamping collar  20  is heated until inner diameter  24  of collar bore  22  is greater than outer diameter  34  of outer wall  32 . Cylinder hull  30  is inserted into collar bore  22 , and clamping collar  20  is cooled to cause clamping collar  20  to contract and decrease inner diameter  24  and radially contact cylinder hull  30 . Such a shrink fit cylinder liner assembly is complex and costly to manufacture. Further, the entire cylinder liner assembly  10  is discarded when only sleeve  40  wears out, thereby also adding to costs. 
     Accordingly, there remains a need in the art for cylinder liners that address the foregoing difficulties and overcomes other limitations of the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more detailed description of the embodiments, reference will now be made to the accompanying figures, wherein: 
         FIG. 1  shows a cross-sectional view of a prior art cylinder liner apparatus; 
         FIG. 2  shows a cross-sectional view of one embodiment of a cylinder liner apparatus employing a replaceable sleeve of the present disclosure, wherein the apparatus is in a loosely assembled configuration; 
         FIG. 3  shows a cross-sectional view of the cylinder liner apparatus employing a replaceable sleeve of  FIG. 2 , wherein the apparatus is in a fully assembled configuration; and 
         FIG. 4  shows a cross-sectional view of one embodiment of a hydraulic loading assembly of the present disclosure and a cylinder liner apparatus in a fully assembled configuration. 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings and description that follows like parts are marked throughout the specification and drawings with the same reference numerals. The drawing figures are not necessarily to scale. Features of the disclosure may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The disclosure is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments described and discussed herein may be employed separately or in any suitable combination to produce desired results. 
     Unless otherwise specified, any use of any form of the terms “connect”, “engage”, “couple”, “attach”, or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. The terms “pipe,” “cylinder,” “tubular member,” and the like as used herein shall include tubing and other generally cylindrical objects. In addition, in the discussion and claims that follow, it may be sometimes stated that certain components or elements are in fluid communication. By this it is meant that the components are constructed and interrelated such that a fluid could be communicated between them, as via a passageway, tube, or conduit. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings. 
     Generally, the present disclosure includes a replaceable sleeve for use with a cylinder liner apparatus in a fluid end portion of a mud pump. More particularly, embodiments of the present disclosure include a replaceable sleeve disposed within a two-piece hull or housing. An elastomeric tube may be disposed between the hull and the sleeve, and the hull pieces forced together over the sleeve and elastomeric tube thereby imparting radial compressive pre-load to the replaceable sleeve. 
     Referring now to  FIG. 2 , an embodiment of a cylinder liner apparatus  100  includes an annular collar  120 , a cylinder hull or housing  130 , a replaceable sleeve  180 , an elastomeric tube  190 , and a retainer  160 . A central axis  115  passes through the longitudinal center of cylinder liner assembly  100 . Annular collar  120  is centered about central axis  115 . Cylinder hull  130  is concentrically disposed within annular collar  120 . Annular collar  120  secures apparatus  100  to a fluid side of a mud pump. In some embodiments, collar  120  is integral with cylinder hull  130  and in other embodiments collar  120  is a separate component from cylinder hull  130 . Elastomeric tube  190  is concentrically disposed within cylinder hull  130 . Replaceable sleeve  180  is concentrically disposed within elastomeric tube  190 . 
     Cylinder hull  130  includes a hull bore  136 , and comprises separate mating components including a first hull portion  132  and a second hull portion  160 . First cylinder hull  132  includes a first end  134  and a second end  135 . Second end  135  includes an annular, inner retainer  138 . First cylinder hull  132  includes a bore  140  including a reduced inner diameter portion  142  forming a seat  144  at the second end  135 . The annular, inner retainer  138  extends from the reduced inner diameter portion  142 . First end  134  includes a reduced outer diameter portion or pin member  146  having a radially outwardly disposed annular groove  148  in which a seal  150  is disposed to sealingly engage first cylinder hull  132  with second cylinder hull  160 . Further, pin  146  includes a radially outwardly disposed retainer recess  152 . 
     Second hull portion  160  includes a first end  162  and a second end  164 . Second cylinder hull  160  includes a bore  166  with a reduced inner diameter portion  168  forming a seat  170  at first end  162 . Second end  164  includes an increased inner diameter portion or annular socket  172  that is slidingly engageable with pin  146  of first end  134  of first cylinder hull  132 . Further, annular socket  172  includes access to a retainer hole  174  that extends through the annular collar  120  and into socket  172 . 
     Elastomeric tube  190  includes a restrained end  192 , a free end  194 , an outer surface  195 , and an inner bore  198 . Elastomeric tube  190  may comprise any suitable elastic, compressible, and durable material including, without limitation, thermosets, thermoplastics, polymers, composites, or combinations thereof. In some embodiments, elastomeric tube  190  comprises an elastic, compressible, durable, low-friction and high strength Nitrile or Buna-N rubber. Further, elastomeric tube  190  includes an anti-extrusion ring  196  disposed on the outer surface  195  of the tube  190 . Ring  196  may comprise any suitable rigid, durable material including, without limitation, metals or metal alloys (e.g., stainless steel, aluminum, etc.), polymer (e.g., polyethylene), composite, or combinations thereof. In some embodiments, ring  196  comprises a rigid, durable, low-friction and high strength metal alloy. 
     Replaceable sleeve  180  includes a restrained end  182  and a free end  184  which has an offset length L O  relative to the longer free end  194  of elastomeric tube  190  that extends axially past the free end  184 . In some embodiments, L O  may be substantially zero or less than zero, i.e., free end  194  of elastomeric tube  190  may be at substantially the same axial location or at an axially inward location relative to the free end  184  of replaceable sleeve  180 . Replaceable sleeve  180  includes a lead-in  186  at free end  184  with the potential of compensating for mechanical misalignment that is present in most mud pumps and further allows for compression of the piston seal during assembly. Further, replaceable sleeve  180  may comprise any suitable rigid, durable material including, without limitation, metals or metal alloys (e.g., stainless steel, aluminum, etc.), polymer (e.g., polyethylene), ceramic, composite, or combinations thereof. In some embodiments, replaceable sleeve  180  comprises a rigid, durable, low-friction and high strength metal alloy such as high chromium cast iron or a ceramic. 
     During assembly, elastomeric tube  190  is placed within bore  140  of first hull portion  132  such that restrained end  192  abuts seat  144 . Sleeve  180  is placed through the bore  198  of sleeve  190  and into bore  142  of first cylinder hull  132  such that restrained end  182  abuts annular retainer  138  of second end  136  of first cylinder hull  132 , thereby securing replaceable sleeve  180  in first cylinder hull  132 . In another embodiment, sleeve  180  is placed within bore  198  of elastomeric tube  190  separately from the first hull portion  132 . Then, the assembly of elastomeric tube  190  and sleeve  180  is placed within bore  140  of first cylinder hull  132  such that restrained end  192  of elastomeric tube  190  abuts seat  144  and sleeve end  182  is positioned within bore  142  of first cylinder hull  132  such that restrained end  182  abuts annular retainer  138  of second end  136  of first cylinder hull  132 , thereby securing replaceable sleeve  180  in first cylinder hull  132 . 
     Pin  146  of first hull portion  132  is inserted into annular socket  172  of second hull portion  160  while simultaneously the assembled sleeve  180  and tube  190  are slidingly received in the bore  166 , such that free end  194  of elastomeric tube  190  contacts seat  170  of end  162 . Thereby, the hull portions  132 ,  160  capture the sleeve  180  and the elastomeric tube  190 , with the elastomeric tube  190  disposed between the sleeve  180  and the hull portions  132 ,  160 . The loosely assembled hull portions  132 ,  160  include a relative compression length L C . The position shown in  FIG. 2  illustrates a cylinder liner apparatus  100  that is partially assembled and prior to compression of elastomeric tube  190 , indicative of the steps in an embodiment of a method for replacement of replaceable sleeve  180 . To impart radially compressive pre-load to replaceable sleeve  180 , a force is applied to continue insertion of pin  146  into annular socket  172  causing compression of elastomeric tube  190  against seat  144 . Anti-extrusion ring  196  prevents elastomeric tube  190  from extruding into annular socket  172 . 
     Referring now to  FIG. 3 , pin  146  is forced into annular socket  172  until L C  is zero and pin  146  is fully inserted into annular socket  172 . Additionally, retainer recess  152  of first cylinder hull  132  aligns with retainer hole  174  of second cylinder hull  160  and one or more retainers  176  is inserted into both retainer recess  152  and retainer hole  174  to lock hull portions  132 ,  160  together to form the hull  130 . In this manner, the hull portions  132 ,  160  are releasably coupled by the retainer  176  about the sleeve  180  with the tube  190  disposed in between. Insertion of pin  146  into annular socket  172  results in high compressive loading of elastomeric tube  190  between cylinder hull  130  and replaceable sleeve  180 . Because elastomeric tube  190  is fully and closely contained, elastomeric tube  190  behaves as a very viscous fluid and distributes the axial compressive force of cylinder hulls  132 ,  160  as a substantially evenly distributed radial compressive force over replaceable sleeve  180 . The force applied by elastomeric tube  190  against replaceable sleeve  180  results in a radially compressive pre-load in replaceable sleeve  180  and secures replaceable sleeve  180  within cylinder hull  130 . The compressive stresses ensure that the sleeve resists cyclic fatigue due to the cyclic pressures of the operating pump sliding therein. 
     In the embodiments of cylinder liner apparatus  100  as shown in  FIGS. 2 and 3 , removal and replacement of replaceable sleeve  180  includes removing cylinder liner apparatus  100  from the fluid end of a mud pump. The next step includes removing one or more retainers  176  from cylinder hull  130  and separating first cylinder hull  132  from second cylinder hull  160  which necessitates removing pin  146  of first cylinder hull  132  from annular socket  172  of second cylinder hull  160 . This step relieves the compressive loading of elastomeric tube  190 , allowing it to return to an original length. In turn, the pressure applied by elastomeric tube  190  against cylinder hull  130  and replaceable sleeve  180  is relieved. At this point, replaceable sleeve may be exposed, accessed, and removed from cylinder hull  130  and replaced by another, unworn replaceable sleeve  180 . In some embodiments, elastomeric tube  190  is removed along with replaceable sleeve  180  and is reused with an unworn replaceable sleeve  180 . In some embodiments, elastomeric tube  190  is replaced by another, unworn elastomeric tube  190 . Cylinder liner apparatus  100  is then assembled as shown in  FIGS. 2-3  and described above. Thus, the only component of cylinder liner apparatus  100  that is discarded is sleeve  180 , the only part that sustains damage during operation. The remaining components of cylinder liner apparatus  100  are reused. 
     It is intended that the embodiments of cylinder liner apparatus described herein are packaged in what is referred to as a replaceable sleeve cylinder liner system including the components of replaceable sleeve cylinder liner apparatus  100 . Referring to  FIG. 3 , one embodiment of replaceable sleeve cylinder liner system includes annular collar  120 , a cylinder hull  130  having first cylinder hull  132  and second cylinder hull  160 , a replaceable sleeve  180 , an elastomeric tube  190 , and a retainer  176 . In all embodiments of replaceable sleeve cylinder liner system shown in  FIG. 3 , sleeve  180  is removed and installed during the replacement process as a component of assembled replaceable sleeve cylinder liner system. 
     The use of an elastomeric tube (e.g., elastomeric tube  190 ) to apply radial compressive pre-load to a replaceable sleeve (e.g., replaceable sleeve  180 ) in the embodiments described above makes it possible for a single operator to remove and replace a worn or damaged replaceable sleeve. An additional benefit resulting from the use of elastomeric tube  190  to apply radial compressive pre-load to replaceable sleeve  180  includes minimizing the small annular space between the outer diameter of the pump piston and inner diameter of the cylinder liner, thus extending the useful service life of the piston. Further, the application of radial compressive pre-load on a replaceable sleeve by surrounding the sleeve with an elastomeric tube which behaves as a highly viscous fluid imparting pressure in a pseudo-hydraulic manner may be employed to eliminate the need for mechanically creating radial compressive pre-load on a sleeve. Alternatively, the method of creating radial compressive pre-load on a mud pump sleeve through the application of pressurized fluid may be combined with the mechanical components practiced in the prior art. 
     A cylinder liner apparatus (e.g., cylinder liner apparatus  100 ) comprising a replaceable sleeve offers the potential for relatively inexpensive material and manufacturing costs, while permitting replacement of only one worn part, namely a replaceable sleeve. Thus, a cylinder liner apparatus of this disclosure allows reuse of the remainder of the cylinder liner apparatus and facilitates use of an economically-advantageous disposable replaceable sleeve. In this way, cylinder liner apparatus of this disclosure allow for a replaceable sleeve to be replaced in the field. Moreover, the compressive makeup force for cylinder liner apparatus of this disclosure can be applied at the pump when the replaceable sleeve is changed or at a separate work station at the well site. If the compressive makeup force is applied at the pump, a custom designed hydraulic loading assembly  200  is used, as shown in  FIG. 4 . Loading assembly  200  includes a first housing  210  that is stationary and captures first cylinder hull  132  and a second housing  220  that is moveable and captures second cylinder hull  160 . Further, loading assembly  200  includes a hydraulic cylinder  230  connected to a stationary base  240  and a hydraulic source  250 . 
     Thus, as taught herein, embodiments of a mud pump cylinder liner apparatus include a cylinder housing including a first hull portion and a second hull portion, and a replaceable sleeve disposed in the cylinder housing, wherein the first and second hull portions are releasably coupled to capture the replaceable sleeve in the cylinder housing, and wherein the first and second hull portions are releasable to provide access to the replaceable sleeve. The apparatus may further include an elastomeric material disposed between the replaceable sleeve and the first and second releasably coupled hull portions. The apparatus may further include an elastomeric tube disposed about the replaceable sleeve. The releasably coupled first and second hull portions may apply a compressive pressure to the elastomeric material creating radial compressive stress in the replaceable sleeve. The elastomeric tube may include a restrained end disposed within the hull portion and a free end disposed within the second hull portion, and the replaceable sleeve may include a restrained end disposed within the restrained end of the elastomeric tube and a free end disposed within the free end of the elastomeric tube, wherein a compressive pressure applied by the releasably coupled hull portions reacts the elastomeric tube free end and creates radial compressive stress in the replaceable sleeve. The apparatus may further include a retainer coupled between the first and second hull portions to maintain the coupling. The retainer may be removable to release the first and second hull portions and expose the replaceable sleeve. The first hull portion may include a pin member slidingly engageable in an annular socket of the second hull portion. The apparatus may further include an annular collar disposed on an outer portion of the cylinder housing. The replaceable sleeve may be configured to receive a pump piston. 
     In certain embodiments, a pump cylinder liner apparatus includes a first cylinder hull portion, a second cylinder hull portion, a replaceable sleeve, and an elastomeric tube disposed about the replaceable sleeve, wherein the first and second cylinder hull portions are releasably coupled to capture the replaceable sleeve and compress the elastomeric tube. The compressed elastomeric tube may impart a radially compressive pre-load to the replaceable sleeve. 
     In other embodiments, a method for replacing a sleeve in a pump cylinder liner apparatus includes providing a cylinder housing with a first hull portion and a second hull portion, capturing a replaceable sleeve between the first and second hull portions, and releasably coupling the first and second hull portions about the replaceable sleeve. The method may further include releasing the first and second hull portions to expose the replaceable sleeve and removing the replaceable sleeve. The method may further include inserting another replaceable sleeve between the first and second hull portions, re-capturing the other replaceable sleeve between the first and second hull portions, and re-coupling the first and second hull portions about the other replaceable sleeve. The method may further include disposing an elastomeric material between the replaceable sleeve and the first and second hull portions and compressing the elastomeric material as a result of capturing the replaceable sleeve and releasably coupling the first and second hull portions about the replaceable sleeve. The elastomeric material may be an elastomeric tube disposed about the replaceable sleeve. The method may further include imparting a radially compressive pre-load to the replaceable sleeve as a result of compressing the elastomeric material. The method may further include capturing an elastomeric tube between the replaceable sleeve and the first and second hull portions and compressing the elastomeric tube about the replaceable sleeve to pre-load the sleeve. 
     While embodiments of this disclosure have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teaching of this disclosure. The embodiments described herein are exemplary only and are not limiting. Because many varying and different embodiments may be made within the scope of the present teachings, including equivalent structures or materials hereafter thought of, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense. It is to be especially understood that the substitution of a variant of a claimed element or feature, without any substantial resultant change in the working of the apparatus, will not constitute a departure from the scope of the disclosure.