Abstract:
The liner retainer assembly includes a cylinder that is mounted on a module of the fluid end of a pump. The cylinder has an aperture for receiving a liner and a retaining piston. A retaining nut is secured on the end of the retaining piston and engages one end of the liner. The retaining piston forms a fluid cavity and a spring cavity within the cylinder. The spring cavity houses a plurality of springs which bias the piston, retaining member, and liner towards the module, thus providing a resilient securing force. The fluid cavity communicates with a supply of hydraulic fluid for biasing the piston away from the module to relieve the springs. By pressurizing the fluid cavity, the springs are compressed to disengage the retaining member from the liner and allow the unthreading of the retaining member and then the removal of the liner.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an assembly for quickly securing and releasing a component to a pump housing and more particularly to a retainer assembly for releasably mounting a piston liner within a hydraulic cylinder on the module of a pump. 
     2. Description of the Prior Art 
     Heavy duty large horsepower pumps are used to pump fluids or slurries with entrained solids. In the oil industry, for example, slush or mud pumps are used to pump viscous fluids, such as drilling muds, cement, or other well fluids. Although mud pumps may be either centrifugal or reciprocating type pumps, typically mud pumps are reciprocating pumps using one or more pistons and hydraulic cylinders with liners to generate the high pressures required to pump these viscous fluids in and out of the well. 
     Mud pumps include a fluid end and a power end. In the fluid end of one type of a triplex mud pump, for example, there are three sets of suction modules and discharge modules in fluid communication. A suction manifold is connected to the fluid inlets of the suction modules for receiving fluids and passing those fluids to each of the suction modules. A discharge manifold is connected to the fluid outlets of the discharge modules for discharging the pumped fluids. Each module encloses a set of flow passages with check valves for controlling the direction of flow of the fluids. A check valve is disposed at the suction module fluid inlet to only allow fluids to enter the suction module inlet end of the module and another check valve is disposed at the discharge module fluid outlet to only allow fluids to exit the the discharge module for flow into the discharge manifold. 
     Each discharge module includes a liner retainer flange attached to the discharge module. The liner retainer flange attaches to a replaceable liner within which a pump piston reciprocates. The piston is a generally cylindrical steel member having a polymer, such as polyurethane, bonded to its outer diameter for sealingly engaging the inner cylindrical wall of the liner to ensure a fluid tight seal required for drawing the low pressure fluids through the suction manifold and module flow passages. The seal integrity must be maintained to withstand the high discharge pressure on the discharge stroke. The power end contains the gears that reciprocate the pump piston within the liner for pumping the fluid through the module passages in the fluid end and thence out the discharge valve. 
     In operation, on the suction stroke, the pump piston draws fluids through the suction manifold and suction valve as the piston strokes within the liner. On the discharge stroke, the check valve in the discharge module opens simultaneously as the suction valve closes preventing suction back flow into the suction module. Fluid in the liner is compressed and pressure is built up until the pressure overcomes well bore pressure so as to pump the mud into the well. The piston then reverses for another suction stroke whereby the check valve in the suction module opens and the discharge valve closes simultaneously, the piston now making a suction stroke. 
     As the piston reciprocates within the liner, friction wears the liner. Further, the fluid passing through the fluid end includes particulates and other solids which wear away and destroy the liner and piston. When the liner and piston degrade, the fluid seal is lost and the pump becomes much less efficient. Also, the reciprocation of the piston in the liner causes pulsations that over time cause the liner to become loose within the containment of the liner retainer flange thus resulting in a degradation of the seal at the face of the liner and the seal at the face of the liner wear plate. Therefore, it is important to be able to replace the liner as a part of routine maintenance (or when emergencies occur from seal failure while drilling) to ensure that the pump operates efficiently and can control well pressure. It is also important to have a means for fastening the liner to the liner retainer flange so as to ensure that the liner remains firmly secured despite extended reciprocation of the piston assembly within the liner. 
     Typically each liner retainer flange, and the cradle of the pump power end are all secured to the fluid end module by studs and threaded connections. Because of the environment in which the mud pump operates and the corrosive nature of the fluids being pumped, the studs and threaded connections, such as nuts, become corroded and are difficult to unthread for the replacement of the liner. Often, the threaded connections have been over tightened, making it even more difficult to unthread. Where the liner is retained by an end cap, a steel bar is inserted into a guide hole in the side of the end cap and then the cap is unscrewed using a significant amount of torque. This end cap is very heavy as it must have sufficient strength to keep the liner from moving, even with pressures up to 7500 psi. Where a nut or end cap resists unscrewing, a sledge hammer is used to hammer on a socket wrench or a special hammer wrench is used to loosen the nut or cap. Such activity is obviously dangerous. In some regions of the world local laws prohibit the use of sledge hammers for personnel safety reasons or to avoid the risk of an explosion due to sparks. 
     Prior art liner retention systems include spring mechanisms around each stud with an end flange for securing the liner against a fluid end module. Hydraulic pressure is applied to the spring mechanism of each stud by a small hydraulic pump to remove the clamping force of the spring mechanism. The release of the clamping force allows the removal of the clamping flange of the liner retention system. Individually actuated spring loaded studs cause an uneven pressure to be applied to the clamping flange. Further, the clamping force is limited because of the limited space available to hold numerous springs. 
     The present invention overcomes the deficiencies of the prior art. 
     SUMMARY OF THE INVENTION 
     The liner retainer assembly of the present invention includes a liner retainer flange that is mounted on the discharge module of the fluid end of a pump. A pressure actuated hydraulic clamping piston with related actuated, conical dished washers and necessary static and sliding seals is disposed within the retainer flange . The hydraulic pressure actuated clamping piston is configured to receive and hold the liner. The hydraulic clamping piston and an end cap maintain the liner in contact with the module during actuation. The hydraulic clamping cylinder includes a counterbore which is divided by the hydraulic piston into a fluid cavity and a spring cavity. The spring cavity houses a plurality of springs which bias the hydraulic piston, end cap, and liner towards the module, thus providing a strong clamping securing force when the hydraulic pressure is released. The fluid cavity communicates with a supply of hydraulic fluid for biasing the hydraulic piston away from the module to activate the springs. By pressurizing the fluid cavity, the springs are compressed so as to disengage the liner retaining end cap from the liner and allow the unthreading of the liner end cap to then remove the liner. 
     The liner retainer assembly permits preloading or prestressing of the liner against the module of the fluid end of the pump so that the liner will not loosen upon the reciprocation of the pump piston within the liner. Further, the liner may be easily secured and unsecured from the module without the necessity of a sledge hammer or other methods for applying excessive amounts of torque to a securing fitting. The assembly of the present invention permits the easy and quick replacement of the liner as necessary. 
     Other objects and advantages of the invention will appear from the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a detailed description of a preferred embodiment of the invention, reference will now be made to the accompanying drawings wherein: 
     FIG. 1 is a cross-sectional view of a typical liner inserted into a liner retaining flange housing assembly constructed in accordance with the present invention. 
     FIG. 2 is a cross-sectional view and partial exploded view of the liner retaining flange assembly of FIG. 1 illustrating the application of hydraulic pressure for the attachment of a retaining cap. 
     FIG. 3 is a cross-sectional view of the liner retaining flange assembly of FIGS. 1 and 2 following the attachment of the retaining cap prior to energizing the Belleville washers. 
     FIG. 4 is a cross-sectional view of an alternative exemplary embodiment of a liner retaining assembly of the present invention. 
     FIG. 5 is a cross-sectional view of a portion of the piston housing showing hydraulic communication taken along plane V—V in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring first to FIGS. 1 and 2, there is shown a fluid end module  10  and a cradle  28  of the pump power end. The pump is of the type used to pump fluids, such as drilling muds, cement or the like. Pumps of this type are well known. A wear plate  14  defines a bore  16  which leads into liner  20 . The module  10  is used for the transfer of fluid from the suction manifold and suction module (not shown) to the discharge manifold (not shown) and discharge module. 
     An exemplary liner retaining flange assembly  18  of the present invention is used to secure liner  20  within a hydraulic cylinder  30  mounted on module  10  and liner retainer flange  22 . Those of skill in the art will understand that a pump piston (not shown) attached to the power end of the pump is reciprocated within the liner  20  to effect the desired pumping action to flow fluid through the fluid end module  10  of the pump. Hydraulic cylinder  30  provides an open end into which the liner  20  is inserted. Module  10  also provides a counterbore  12  for the adjacent wear plate  14  against which it is desired to retain the liner  20  during operation of the pump piston. It can be appreciated that the purpose of wear plate  14  is to avoid the end of liner  20  wearing module  10  due to the reciprocation of the piston within liner  20 . However, wear plate  14  may cause wear to the module  10  if the liner  20  is not securely affixed. Wear plate  14  may be replaced should that wear become excessive. It is noted that the end of the liner  20  adjacent the wear plate  14  includes an internal annular groove  59  with seal member  61  for sealingly engaging the wear plate  14  and the other open end  15  of liner  20  includes an external annular load-bearing shoulder  60  which retains end cap  64  (FIG.  2 ). 
     The hydraulic cylinder  30  includes a threaded, reduced diameter portion  24  and an enlarged diameter portion  32 . Reduced diameter portion  24  is secured in a threaded or splined relation at  23  to liner retainer flange  22  that is located in an abutting relation to the module  10 . Bolted studs  26  secure the cradle  28  of the pump power end, the liner retaining flange  22  and hydraulic cylinder  30  to module  10 . 
     The enlarged portion  32  of hydraulic cylinder  30  includes an inner clearance cavity  33  which has a reduced diameter neck, forming a hydraulic cavity  58  to activate hydraulic piston  42  which in turn compresses springs  56  which are restrained from escaping from the spring cavity  35  by retainer ring  48 . Hydraulic sealing is accomplished by sealing rings  39  and  49 . End cap  64  is held in place with external threads  46 . A hydraulic fluid port and fitting  38  is disposed through the wall of enlarged diameter portion  32 . 
     When these components are assembled, the annular flange  44  of piston  42  forms hydraulic cavity  58  and outer spring cavity  35 . The hydraulic fluid port and fitting  38  communicates with hydraulic cavity  58  for applying hydraulic pressure to flange  44 . The spring cavity  35  houses a plurality of axially compressible Belleville springs or washers  56 . Retainer ring  48  has external threads  50  which threadingly mate in a complimentary fashion with the internal threads  34  of enlarged diameter portion  32 . The washers  56  bear against the retainer ring  48  and annular flange  44 . Enough springs are used so as to insure sufficient force is generated to prevent movement of liner  20  when pump pressure is at maximum. The retainer ring  48  secures the washers  56  and hydraulic piston  42  within the enlarged diameter portion  32  of hydraulic cylinder  30 . O-ring  49  provides a fluid-tight seal between the piston  42  and enlarged diameter portion  32 . 
     Upon assembly as shown in FIG. 1, hydraulic piston  42  has previously been inserted into enlarged diameter portion  32  of cylinder  30  to form cavities  58  and  35 . Belleville washers  56  are inserted into outer spring cavity  35  and retainer ring  48  is threaded into place. The liner  20  is inserted into the outer hydraulic cylinder  30  of liner retaining assembly  18  so that the end of the liner  20  with seal  61  abuts wear plate  14 . 
     Referring particularly to FIG. 2, the retaining assembly  18  is shown ready to secure the liner  20  in place. A hydraulic hose  62  is secured to the external port and fitting  38  for supplying hydraulic fluid to inner hydraulic cavity  58 . As fluid pressure is supplied to cavity  58 , fluid pressure is exerted against flange  44  urging piston  42  outward toward retainer ring  48 . As annular flange  44  of piston  42  is so moved, springs  56  are axially compressed. As springs  56  are compressed, the threaded end  46  of piston  42  extends further away from wear plate  14  and module  10 . 
     In the outward and extended position of piston  42 , end cap  64  is threaded onto the threaded end  46  of the piston  42  so the threads  46  mate with the threads  66  of end cap  64 . End cap  64  need only be hand tightened. It is noted that liner load bearing shoulder  60  mates with the shoulder  68  on end cap  64 . 
     Referring now to FIG. 3, the retaining assembly  18  is shown completely assembled with the liner  20  securely affixed within the hydraulic cylinder  30 . Once end cap  64  has been affixed, the fluid within the hydraulic cavity  58  is evacuated through port and fitting  38  permitting the springs  56  to bias flange  44  toward wear plate  14  and module  10  and bias end cap  64  against the other end  15  of liner  20 . As the hydraulic pressure in the hydraulic cavity  58  is released, stored energy from the compression of springs  56  is released to load the liner  20  longitudinally. As a result, the energy stored by compressing springs  56  is transmitted to the liner  20  in order to load it longitudinally against wear plate  14  and module  10 . 
     In order to remove the liner  20 , the procedure is substantially reversed. Fluid is introduced into the hydraulic cavity  58  through port and fitting  38  in the same manner as previously described to compress springs  56  and external piston  42 . Once spring forces are removed, end cap  64  may then be unthreaded. Fluid is bled off, springs  56  are decompressed and the unit is stabilized. 
     It is noted that the arrangement of the present invention permits a liner to be replaced rapidly and easily and without the use of extra tools or having to apply excessive torque. Further, a prestress force is applied to the liner  20  so that it is longitudinally compressed against wear plate  14  and module  10 . This load or prestress securely holds the liner  20  against the wear plate  14  despite repeated reciprocation of the pump piston within liner  20 . 
     Referring now to FIGS. 4 and 5, an alternative embodiment for an exemplary retaining assembly  70  is illustrated with the liner  20  inserted and securely affixed therewithin. For simplicity, like reference numerals are used for like or similar components. FIG. 5 is a cross-sectional view of the hydraulic cylinder  36  taken along plane V—V in FIG.  4 . 
     In this embodiment, hydraulic cylinder  36  defines a plurality of individual piston chambers  72 . There are  4 ,  6 , or  8  chambers  72  (depending on the holding force required) which are azimuthally spaced around hydraulic cylinder  36 . Each piston chamber  72  contains a wear cylinder sleeve  101  with an individual piston  74  that is reciprocably disposed therein. Wear sleeve  101  includes threaded bores  103  for receiving bolts to assist in the replacement of sleeves  101  when excessive wear has occurred. Each piston  74  provides an elongated shaft  76  and a radially extending flange  78  so that when disposed within the chamber  72 , the chamber  72  is divided into a spring retaining chamber  80  and fluid chamber  82 . The shaft  76  of the piston  74  is threaded at  84  for threadingly receiving a nut  86 . Fluid may be introduced into the fluid chamber  82  through an associated hydraulic fluid port and external fitting  38 . 
     A cover  88  is placed over the open end  15  of liner  20 , the cover  88  having a central opening  90  through which liner  20  is disposed. The cover  88  also includes apertures  92  for the disposal of each piston shaft  76 . The cover  88  serves to provide a solid surface against which Belleville springs  94  may be compressed. O-ring seals  96  surround the flange  78  of each piston  74  to ensure fluid sealing. 
     An end cap  98  is shown disposed over the cover  88 . The end cap  98 , like the cover  88 , provides apertures  100  for receiving piston shafts  76 . However, the central aperture  102  is only large enough to permit a portion of the liner  20  to be disposed therethrough, creating a shoulder  104  which mates with the shoulder  60  of liner  20 . 
     Referring particularly to FIG. 5, a plurality of fluid passages  106  are provided in hydraulic cylinder  36  which interconnect and communicate with each piston chamber  72  and each of the ports and fittings  38  on the hydraulic cylinder  36 . The fluid interconnection permits all of the fluid chambers  82  (FIG. 4) to be filled with fluid by using only one or a few of the hydraulic fluid ports and fittings  38  for injecting fluid. The common communication with all fluid chambers  82  also allows the common hydraulic actuation of all the pistons  74  (FIG.  4 ). 
     In operation as shown in FIG. 4, the liner  20  is installed and removed in a manner similar to that described with respect to liner retaining assembly  18 . Fluid is introduced into each individual fluid chamber  82  urging the associated piston  74  to move toward the open end  15  of liner  20 . Energy is stored through axial compression of the Belleville springs  94 . The end cap  98  is placed onto the liner open end  15  so that the shoulder  104  engages shoulder  60  of liner  20 . Nuts  86  are then tightened onto each piston  74 . Again, the nuts need only be hand tightened. Fluid is then evacuated from the fluid chambers  82  and the Belleville springs  94  bias pistons  74  toward the wear plate  14  and the module  10 , thus loading liner  20  longitudinally against wear plate  14  and module  10 . 
     While preferred embodiments of this invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system and apparatus are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.