Patent Publication Number: US-2013232789-A1

Title: Threaded rod plunger installation tool

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to provisional application 61/225,142, filed Jul. 13, 2009. 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general to plungers used in reciprocating pumps, and, in particular, to a threaded rod tool for installing a plunger. 
     BACKGROUND OF THE INVENTION 
     Various kinds of pumps can be used in oilfield operations. One type of pump, for example, is a reciprocating pump. The reciprocating pump can be used to pump fluid such as chemicals, cement, or other media into a well. Reciprocating pumps typically increase the pressure within a cylinder by reciprocating a plunger longitudinally within the cylinder. Packing is generally used around the plunger and the plunger reciprocates as a crankshaft located within the pump rotates. As the plunger moves away from the cylinder, the pressure of the fluid inside chamber decreases creating a differential pressure across an inlet valve that allows the fluid to enter the cylinder. As plunger moves longitudinally towards the cylinder, the pressure of the fluid inside of the cylinder increases until the differential pressure across an outlet valve opens the outlet valve and allows fluid to exit cylinder. 
     Maintenance of the pump, typically includes repacking of the packing surrounding the plunger and revalving of the inlet and outlet valves mentioned above. To allow repacking or revalving, the pump is disassembled by removing a suction cover plate and removing the plunger, which can be quite heavy. Additional pump components, such as connecting rods and pony rods may need to be stroked out to push out the plunger. However, during assembly of the pump, the plunger must be reinstalled. The plunger is heavy and requires much effort to push it back into the cylinder through the packing elements. Frequently, installing the plunger requires maintenance personnel to hammer the plunger into place during installation, potentially damaging pump parts or injuring personnel. 
     Thus, installation of the plunger into the cylinder is time consuming, labor intensive, and potentially unsafe to personnel. 
     Thus, a technique would be desired that makes pump maintenance and plunger installation safer, less time consuming, and less labor intensive. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present invention, a threaded rod plunger installation tool is connected to a pump after maintenance is complete. The tool includes a threaded ring that threads into a cylinder opening. The cylinder opening is covered by a suction cover plate during operation and has threads on an interior surface. The threaded ring provides a reaction point during the installation of the plunger. The tool further comprises a nut with a handle and a pair of channels that slide over a lip formed on the exterior side of the threaded ring. The nut in this embodiment is separate from the rest of the tool. 
     In an embodiment of the present invention, the plunger installation tool further comprises a threaded rod that engages a threaded opening on the nut. The rod has an end that can engage the plunger and also has a bolt head on the other end that can be engaged by a driver such as a wrench. 
     During installation of the plunger the plunger is placed at the cylinder opening and the threaded rod plunger installation tool is mounted onto the pump. A driver such as a wrench or a motorized drill can engage the bolt head and rotate it and thereby advance the threaded rod into the cylinder opening. The nut prevents the threaded rod from backing out as it pushes the plunger into the cylinder bore. The installation tool advantageously generates sufficient force, in one example at least 2000 psi, to push the plunger into place. Once the plunger is properly in place within the pump cylinder, the threaded rod can be backed out of the nut by the driver and the plunger installation tool can then be removed for storage, allowing the suction cover plate to be placed back on the cylinder opening. 
     The threaded rod plunger installation tool thus advantageously provides a safer way to maintain and disassemble pumps because the plunger installation tool, rather than a hammer, can be used to push the plunger back into position within the pump cylinder. This also results in a less time consuming, potentially less damaged parts, and a less labor intensive method of maintaining and disassembling the pumps as hammering of the heavy plunger is eliminated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of a prior art reciprocating pump; 
         FIG. 2  is a sectional view of the pump of  FIG. 1 ; 
         FIG. 3  is an enlarged perspective view of the interior side of one embodiment of a threaded rod installation tool used to install the plunger back into the cylinder opening, constructed in accordance with the invention; 
         FIG. 4  is an enlarged perspective view of the exterior side of one embodiment of a threaded rod installation tool used to install the plunger back into the cylinder opening, constructed in accordance with the invention; 
         FIG. 5  is a sectional view of one embodiment of a threaded rod installation tool pushing the plunger back into the cylinder opening, constructed in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , reciprocating pump assembly or pump  12  includes a crankshaft housing  13  that comprises a majority of the outer surface of reciprocating pump  12 . Stay rods  15  connect crankshaft housing  13  to a cylinder housing  17  having a set of cylinders  37  ( FIG. 2 ). Each cylinder  37  is in communication with a fluid inlet  19  and a fluid outlet  21 . As shown in  FIG. 2 , a suction cover plate  22  connects to an end of each cylinder  17  opposite the housing that houses the stay rods  15 . Pump  12  can be free-standing on the ground, can be mounted to a trailer that can be towed between operational sites, or mounted to a skid such as for offshore operations. 
     Referring to  FIG. 2 , a portion of reciprocating pump  12  housed within crankshaft housing  13  is shown. Crankshaft housing  13  houses a crankshaft  25 , which is typically mechanically connected to a motor (not shown). The motor rotates crankshaft  25  in order to drive reciprocating pump  12  ( FIG. 1 ). In one embodiment, crankshaft  25  is cammed so that fluid is pumped from each cylinder  37  at alternating times. As is readily appreciable by those skilled in the art, alternating the cycles of pumping fluid from each of cylinders  37  helps minimize the primary, secondary, and tertiary (et al.) forces associated with reciprocating pump  12  ( FIG. 1 ). 
     A gear  24  is mechanically connected to crankshaft  25 , that is rotated by the motor through gears  26  and  24 . A connector rod  27  is connected to the crankshaft  25  at one end. The connector rod  27  connects to a crosshead  29  through a crosshead wrist pin  31 , which holds connector rod  27  longitudinally relative to crosshead  29 . The connector rod  27  pivots within a crosshead bushing  34  as crankshaft  25  rotates with the other end of connector rod  27 . A pony rod  33  extends from crosshead  29  in a longitudinally opposite direction from crankshaft  25 . Connector rod  27  and crosshead  29  convert rotational movement of crankshaft  25  into longitudinal movement of pony rod  33 . 
     A plunger  35  is connected to pony rod  33  for pumping the fluid passing through cylinder  37 . Packing  36  surrounds plunger  35 . A packing nut  38  is threaded into the cylinder housing  17 , and acts to maintain the packing  36  in the proper position within cylinder  37 . Cylinder  37  includes an interior or cylinder chamber  39 , which is where plunger  35  compresses the fluid being pumped by reciprocating pump  12  ( FIG. 1 ). Cylinder  37  also typically includes an inlet valve  41  and an outlet valve  43 . Valves  41  and  43  are usually spring-loaded valves and are actuated by a predetermined differential pressure. Inlet valve  41  actuates to control fluid flow through fluid inlet  19  into cylinder chamber  39 , and outlet valve  43  actuates to control fluid flow through fluid outlet  21  from cylinder chamber  39 . 
     Plunger  35  reciprocates, or moves longitudinally toward and away from cylinder chamber  39 , as crankshaft  25  rotates. As plunger  35  moves longitudinally away from cylinder chamber  39 , the pressure of the fluid inside chamber  39  decreases creating a differential pressure across inlet valve  41 , which actuates valve  41  and allows the fluid to enter cylinder chamber  39  from fluid inlet  19 . The fluid being pumped enters cylinder chamber  39  as plunger  35  continues to move longitudinally away from cylinder chamber  39  until the pressure difference between the fluid inside chamber  39  and the fluid in fluid inlet  19  is small enough for inlet valve  41  to actuate to its closed position. As plunger  35  begins to move longitudinally towards cylinder chamber  39 , the pressure on the fluid inside of cylinder chamber  39  begins to increase. Fluid pressure inside cylinder chamber  39  continues to increase as plunger  35  approaches cylinder chamber  39  until the differential pressure across outlet valve  43  is large enough to actuate valve  43  and allow the fluid to exit cylinder  37  through fluid outlet  21 . In one embodiment, fluid is only pumped across one side of plunger  35 , therefore reciprocating pump  12  is a single-acting reciprocating pump. 
     Maintenance of the pump  12 , typically includes repacking of the packing  36  surrounding the plunger  35  and revalving of the inlet and outlet valves  41 ,  43 . To allow repacking or revalving, the pump  12  is disassembled by removing the suction cover plate  22  and removing the plunger  35 . The connector rod  27  and pony rod  33  can be stroked out to slide the plunger  35  out and provide access to the packing  36  and valves  41 ,  43 . Frequently, installing the plunger  35  requires maintenance personnel to hammer the plunger  35  into place during installation. This approach to reinstall the plunger  35  can damage pump  12  parts and injure personnel. 
     Referring to  FIGS. 3-5 , an embodiment of a threaded rod plunger installation tool  50  is shown. The threaded rod plunger installation tool  50  can be placed proximate to the pump  12  after maintenance is complete. The tool  50  comprises a threaded ring  52  shown threaded on an outer circumference that screws into a threaded pump cylinder opening  53  ( FIG. 5 ). The tool  50  thus provides a reaction point during installation of the plunger  35 . The tool  50  further includes a planar shaped nut  54  with an attached curved handle  56 . The nut  54  lies in a plane that is substantially perpendicular to an axis of the ring  52 . A pair of side channels  58  is formed in an end of the nut  54  opposite where the handle  56  is mounted. The nut  54  can be held by the handle  56  and slid over a lip  60  ( FIG. 5 ) formed on the exterior side of the threaded ring  52 . The channels  58  on the nut  54  slidingly receives the lip  60  on the threaded ring  52 . The nut  54  can be solid or can have a plurality of holes  55  to reduce the weight of the nut  54 . Further comprising the plunger installation tool  50  is a threaded rod  62  that engages a threaded opening  64  on the nut  54 . The threaded rod  62  has a plunger engagement end  66  and a bolt head  68  on the other end for engagement with a driver such as a wrench. 
     During installation of the plunger  35 , as shown in  FIG. 5 , the plunger  35  is placed at the cylinder opening  53  and the threaded rod plunger installation tool  50  is mounted onto the threaded cylinder opening  53  with the threaded ring  52  portion. A driver such as a wrench or a motorized drill can engage the bolt head  68  to rotate it and thereby advance the threaded rod  62  into the cylinder opening  53 . The nut  54  prevents the threaded rod  62  from backing out. When the plunger engagement end  66  engages one end of the plunger  35 , the continued advancement of the threaded rod  62  in response to its rotation by the driver will force the plunger  35  into the bore  37  of the pump cylinder  17 . The installation tool  50  can generate sufficient distributed force, preferably at least 2000 psi, through the driver and reaction points created by the threaded ring  52  and nut  54 , to push the plunger  35  into place. After the plunger  35  is properly in place within the pump cylinder  17 , the threaded rod  62  can be backed out of the nut  54  by the driver. The plunger installation tool  50  can then be removed for storage and the suction cover plate  22  placed back on the cylinder opening  53 . 
     In another embodiment (not shown), the threaded rod plunger installation tool  50  has a hole at one end through which a rod can pass through and act as the driver rather than a wrench. 
     Reciprocating pumps  12  are large, and complex pieces of equipment with many parts that may have to be replaced as they wear out. Making the disassembly safer, simpler, and less time consuming is thus desirable because it makes pump maintenance safer and less labor intensive. By using a threaded rod plunger installation tool  50  that can install the plunger  35  back into the pump  12  via a mechanical wrench or power drill, the need for manually hammering the plunger  35  into place is eliminated. Thus, the dangerous and labor intensive task of installing the plunger  35  back into the pump  12  after completion of maintenance, is eliminated. 
     This written description uses examples to disclose the invention, including the best mode, and also enable a person of ordinary skill in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. These embodiments are not intended to limit the scope of the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.