Stator tube removal and installation device

An apparatus for removing a stator tube from a position about a rotor of a progressing cavity pump is provided. The apparatus includes an actuator assembly having a base and a piston which is longitudinally displaceable relative to the base, and a pusher rod. The base of the actuator assembly is removably attachable to a discharge end of the stator tube. The pusher rod is longitudinally releasably attachable to the piston at a plurality of locations along the length of the pusher rod and is located to engage the rotor when the base is coupled to the stator tube. The pusher rod is coupled to the piston and the piston is driven by the actuator assembly. With only slight modifications the apparatus may also be used to install the stator tube on the rotor when operated in a substantially opposite way.

TECHNICAL FIELD

The present disclosure relates generally to progressing cavity pumps, and more particularly, to a device for removing and/or installing the stator tube of a progressing cavity pump.

BACKGROUND

A conventional progressing cavity pump system, which can be used to pump a wide range of fluids, typically includes an inlet chamber or suction chamber, and a generally cylindrical stator tube having a discharge port. The pump may include a rotor and a stator located inside the stator tube and having an internal bore extending longitudinally therethrough. The rotor may be rotationally disposed in the internal bore of the stator tube. The stator may be in the form of a double lead helical nut, in which case the stator may include a pair of internal helical grooves which define the internal bore. Likewise, the rotor may be a single lead helical screw rotor including one external helical lobe. The rotor may be rotationally disposed within the internal bore so that the external helical lobe of the rotor and the internal helical grooves of the stator define a plurality of cavities therebetween. The stator is typically formed from a resilient and flexible elastomeric material, and the rotor is typically manufactured from a metallic material. The rotor may be rotatably driven by a drive shaft which may be coupled to the rotor by a universal joint as is well known to those skilled in the cavity pump art. For additional information regarding the operation and construction of progressing cavity pumps, reference can be made to U.S. Pat. No. 2,512,764, U.S. Pat. No. 2,612,845, and U.S. Pat. No. 6,120,267.

As the rotor is rotatably driven within the stator bore, the cavities formed between the rotor and the stator progress from the suction end of the stator tube to the discharge end of the stator tube. In one revolution of the rotor, two separate sets of cavities are formed, with one set of cavities being formed or opening at exactly the same rate as the second set of cavities are closing. This pumping process results in a predictable, pulsationless flow of the fluid.

Because the stator is typically made from an elastomeric material, the stator may experience wear after a period of use. Therefore, it may be desirable to remove the stator tube and stator from the progressing cavity pump system for reconditioning or replacement. Accordingly, there is a need for a device for assisting in the removal and installation of a stator tube of a progressing cavity pump.

SUMMARY

In one embodiment, the invention is an apparatus for removing a stator tube from a position about a rotor of a progressing cavity pump, the rotor being rotatable relative to the stator tube to pump material through the stator tube. The apparatus includes an actuator assembly having a base and a piston which is displaceable relative to the base along a first axis, and a pusher rod. The base of the actuator assembly is removably attachable to a discharge end of the stator tube. The pusher rod is releasably attachable to the piston along the first axis at a plurality of locations along the pusher rod and is located to engage the rotor when the base is coupled to the stator tube, the pusher rod is coupled to the piston and the piston is driven by the actuator assembly.

The apparatus generally operates by pulling the stator tube off of the rotor while using the rotor as a fixed ground point which provides a resistive force. By adjusting the position of the pusher rod with respect to the piston along the first axis, the actuator assembly has an adjustable working length to enable the stator tube to be removed from the rotor of the progressing cavity pump.

Other objects and advantages will be apparent from the following description and the accompanying drawings.

DETAILED DESCRIPTION

As shown inFIGS. 1 and 2, a conventional progressing cavity pump system, generally designated10, may include an inlet chamber or suction chamber12and a cylindrical stator tube16having a discharge port14. The stator tube16includes a suction end30that is coupled to, and in fluid communication with the inlet chamber12. The pump10may further include a rotor18and a stator20located inside the stator tube16, the stator tube16having an internal bore22extending longitudinally therethrough. The stator20may be in the form of a double lead helical nut, in which case the stator20may include a pair of internal helical grooves23a,23bwhich define the internal bore22. Likewise, the rotor18may be a single lead helical screw rotor including one external helical lobe. The rotor18may be rotationally disposed within the internal bore22so that the external helical lobe of the rotor18and the internal helical grooves of the stator23a,23bdefine a plurality of cavities24therebetween. The stator20is typically formed from a resilient and flexible elastomeric material, and the rotor18is typically manufactured from a metallic material. The rotor18may be rotatably driven by a drive shaft (not shown) which may be coupled to the rotor18by a universal joint28as is well known to those skilled in the cavity pump art.

As the rotor18is rotatably driven within the stator bore22, the cavities24formed between the rotor18and the stator20progress from the suction end30of the stator tube16to the discharge end32of the stator tube16. In one revolution of the rotor18, two separate sets of cavities are formed, with one set of cavities being formed or opening at exactly the same rate as the second set of cavities are closing. This pumping procedure results in a predictable, pulsationless flow of the fluid.

Because the stator20is typically made from an elastomeric material, the stator20may experience wear after a period of use. Therefore, it may be desirable to remove the stator tube16and stator20from the progressing cavity pump system10for reconditioning or replacement.

FIG. 1illustrates one embodiment of an apparatus34for removing or installing the stator tube16. The stator tube removal/installation device34may include an actuator assembly36having a base37and a piston38which is longitudinally displaceable relative to the base37along a first axis62. The base37may include a cross bar48which includes a pair of opposed slots50which are shaped and located to receive a fastener47therethrough to couple the base37to the discharge end32of the stator tube16. The fasteners47that are used to couple the base37and cross bar48to the stator tube16may include spacers46located thereon for spacing the base37from the stator tube16when the base37is coupled to the stator tube16.

The piston38can be driven by the base37along the first axis62between an extended position, shown inFIGS. 3 and 5, and a retracted position, shown inFIGS. 4 and 6. When the actuator assembly36is in the retracted position a distal end39of the piston38(which is the end of the piston38that is located farthest from the stator tube16when the actuator assembly36is mounted to the stator tube16) is located adjacent to the base37. When the actuator assembly36is in the extended position the distal end39of the piston38is spaced away from the base37along the first axis62, preferably at the outer limit of the range of motion of the piston38along the first axis62. The movement of driving the piston38from an extended position to the retracted position or from the retracted position to an extended position is termed a stroke, and the distance that the piston38moves between the extended position and the retracted position, or vice versa, is termed a stroke length.

In the embodiment shown inFIG. 1, the actuator assembly36is a hydraulic cylinder assembly and the piston38is a hollow piston. However, various other actuators may be used to drive the piston38, including but not limited to pneumatic, electrically-powered and non-cylindrical drivers. Additionally, although the piston38is shown and described as tubular, the piston38need not be hollow or have a circular cross section.

The stator tube removal/installation device34shown inFIG. 1includes a pusher rod40that is received in and is concentric with the piston38. The pusher rod40is releasably attachable to the piston38along the first axis62at a plurality of locations along the pusher rod40. In the embodiment shown inFIG. 1, the pusher rod40has a length that is at least greater than a length of the piston38and includes a plurality of keyholes42spaced apart along the axial length of the pusher rod40by a distance about equal to a stoke length of the actuator assembly36. The piston38may also include a keyhole43located near its distal end39. Accordingly, the pusher rod40can be releasably coupled to the piston38for movement along the first axis62by aligning one of the keyholes42of the pusher rod40with the keyhole43of the piston38, and pushing a pin17through the aligned keyholes42,43.

As noted above, the pusher rod40need not possess a circular cross section, and the pusher rod40need not be received in the piston38. For example, the pusher rod40and the piston38may be positioned side by side or located in other arrangements. Additionally, any of a variety of methods or structures of coupling the piston38and pusher rod40may be used without departing from the scope of the invention such as clamps, fasteners, friction, and various inter-engaging geometries.

In order to remove the stator tube16of the pump10from the rotor18, the base37of the actuator assembly36is coupled to the discharge end32of the stator tube16such that the base37is located between the distal end39of the piston38and the stator tube16. The actuator assembly36should be coupled to the stator tube16to prevent the actuator assembly36from pushing itself away from the stator tube16when the actuator assembly36is activated. In one embodiment, a threaded fastener47is passed through each of the slots50and through an opening53of the discharge end32of the stator tube16, and nuts57are threaded onto each end of the fasteners47. The spacers46on the fasteners47provide a gap between the stator tube16and the actuator assembly36which may permit an operator to visually align the working end44of the pusher rod40with the discharge end of the rotor18as the base37is mounted to the stator tube16. Next, the stator tube16is disconnected from the progressing cavity pump system10(i.e. disconnected from the inlet chamber12). The piston38is then moved to its extended position, and the pusher rod40is coupled to the piston38such that the working end44of the pusher rod40is located and adjacent to the rotor18, as shown in FIG.3. Accordingly, as shown, the base37of the actuator assembly36is located between the working end44of the pusher rod40and the distal end39of the piston38.

The actuator assembly36is then activated or stroked such that the piston38and associated pusher rod40are moved in the direction of arrow A toward the discharge end of the rotor18. Because the rotor18is either fixed along the first axis62or because the rotor18and associated progressing cavity pump system10possess a great deal more mass than the stator tube16and base37, when the working end44of the pusher rod40engages the discharge end of the rotor18, the rotor18will exert a resistive force on the working end44of the pusher rod40. As a result of force exerted on the piston38by the actuator assembly36, the base37and associated stator tube16will be pulled in the direction of arrow B toward the distal end39of the piston38and away from the rotor18. The step of activating or stroking the actuator assembly36is then continued until the piston38is moved from its extended position (FIG. 3) to its retracted position (FIG.4). During this time, the stator tube16is pushed at least partially off of the rotor18by a distance approximately equal to a the stroke length of the actuator assembly36. Due to the shape of the rotor18and stator tube16, the stator tube16and the stator tube removal/installation device34may be rotated about the first axis62as the stator tube16is pulled off of the rotor18.

In the embodiment shown inFIGS. 1-7, the stroke length of the actuator assembly36is shorter than the length of the stator tube16, in which case the stator tube16cannot be removed from its position about the rotor18in a single stroke. Accordingly, the stator tube removal/installation device34must pull the stator tube16from its position about the rotor18in a series of repeated steps. To accomplish the removal operation in a series of steps, the stator tube removal/installation device34is provided with a variable working length that can be adjusted along the first axis62between each stroke of the actuator assembly36as the stator tube16is incrementally removed. Specifically, a pin connection may be used to enable the position of the pusher rod40to be adjusted with respect to the piston38along the first axis62using the pin connection.

In particular, when the stroke length of the actuator assembly36is shorter than the length of the stator tube16, the stator tube removal/installation device34must be adjusted and reactivated in order to fully remove the stator tube16from the rotor18. In this case, the next step in the removal operation is to deactivate the actuator assembly36such that the piston38reciprocates back from its retracted position to its extended position. Likewise, the pusher rod40, which is coupled to the piston38, is carried with the piston38and moved away from the rotor18such that the working end44of the pusher rod40no longer engages the discharge end of the rotor18. Then, as shown inFIG. 5, the pin17which couples the pusher rod40and the piston38is removed and the working end44of the pusher rod40is moved longitudinally along the first axis62such that the pusher rod40is located adjacent to the rotor18. The pin17is then passed through the aligned keyholes42,43to couple the pusher rod40and piston38together. In this manner the working length of the stator tube removal/installation device34can be adjusted to accommodate the new position of the stator tube16relative to the rotor18after the previous stoke of the actuator assembly36.

Referring toFIG. 6, the next step is to reactivate the actuator assembly36such that the piston38and pusher rod40move in the direction of arrow C. Again, when the working end44of the pusher rod40engages the discharge end of the rotor18, the rotor18exerts a resistive force which causes the piston38to push the base37and stator tube16in the direction of arrow D toward the distal end39of the piston38and away from the rotor18. The step of reactivating or stroking the actuator assembly36is continued until the piston38is moved from its extended position to its retracted position. Accordingly, the stator tube16is again pushed off of the rotor18by a distance approximately equal to a the stroke length of the actuator assembly36.

The steps of deactivating the actuator assembly36, decoupling the pusher rod40and the piston38, adjusting the longitudinal position of the pusher rod40with respect to the piston38along the first axis62, coupling the pusher rod40and the piston38, and reactivating the actuator assembly36, are then repeated as necessary until the stator tube16is completely removed from the rotor18.

In addition to the previously described removal operation, the stator tube removal/installation device34shown inFIG. 1may be slightly modified and used to install a stator tube16onto a rotor18. Specifically, in order to install the stator tube16onto a rotor18of a progressing cavity pump system10using the stator tube removal/installation device34, an I-bolt or other attachment mechanism may be installed on the rotor18so that a tension member52can be attached to the rotor18. As shown inFIG. 7, the tension member52may take the place of the pusher rod40when the stator tube removal/installation device34is used in an installation operation. In the embodiment shown inFIG. 7the tension member52is a chain. However, the tension member52may be nearly any structure that can carry a tension load, such as a rod nearly identical to the pusher rod40. Nevertheless, a chain may be preferred because each link of the chain provides an opening that can receive a pin therethrough. Furthermore, the tension member52is preferably generally flexible at least at its end that is coupled to the rotor18to accommodate any movement of the rotor18relative to the stator tube16. If the tension member18is not flexible itself, the tension member may otherwise flexibly coupled to the rotor18. Accordingly, if a rod is used as the tension member, the tension member may include a short length of chain, a universal joint, etc., to provide a flexible connection to the rotor18. In addition, various other methods and structure for attaching the tension member52to the rotor18may be used, such as passing the tension member52through a hole in the rotor18, passing the tension member52about the rotor18, etc.

In order to install the stator tube16on the rotor18, a working end54of the tension member52is attached to the rotor18, preferably at the discharge end60(See FIG.8). The tension member52is also passed through the stator tube16, the actuator assembly36and the piston38. Next the base37of the actuator assembly36is attached to the discharge end32of the stator tube16and the suction end30of the stator tube16is positioned adjacent to the discharge end60of the rotor18. The base37is coupled to the stator tube16to enable the actuator assembly36to remain properly aligned with the rotor18during the installation process. The tension member52is then coupled to the piston38for movement along the first axis62by passing the pin17through the keyhole43and a link in the tension member52. Of course various other methods or structures for coupling the piston38and the tension member52may be used. For example, referring toFIG. 13, a clip64having an outside dimension that is larger than an outside dimension of the piston38and having a slot66for receiving a link of the tension member52may be slid over a link of the tension member52adjacent to the distal end39of the piston38to prevent movement of the tension member52relative to the piston38toward the rotor18along the first axis62. The tension member52is preferably coupled to the piston38such that no more than a small amount of slack exists in the tension member52between the attachment to the discharge end of the rotor18and the connection to the piston38.

Referring toFIG. 9, the next step is to activate or stroke the actuator assembly36such that the piston38and tension member52are moved in the direction of arrow E away from the discharge end of the rotor18. Because the rotor18is either fixed along the first axis62or because the rotor18and associated progressing cavity pump system10possess a great deal more mass than the stator tube16and the base37, when the tension member52is pulled tight between the pin connection to the piston38and the discharge end60of the rotor18, the rotor18exerts a resistive force. As a result of force exerted on the piston38by the actuator assembly36, the base37and stator tube16will be pushed in the direction of arrow F away from the distal end39of the piston38and toward the rotor18. The step of activating or stroking the actuator assembly36is then continued until the piston38is moved from its retracted position to its extended position. Accordingly, the stator tube16is slid on to the rotor18for a distance approximately equal to a the stroke length of the actuator assembly36. The stator tube16may be rotated as it slides onto the rotor18.

Thus, when performing an installation operation, the stator tube removal/installation device34pushes the stator tube16to a position about the rotor18using the rotor18as an anchor point. In general, after the tension member52is attached to the discharge end60of the rotor18and the base37of the actuator assembly36is mounted to the discharge end32of the stator tube16, the tension member52, which is coupled to the piston38via pin17, is put in tension by driving the piston38away from the rotor18. Then, as a result of force exerted on the piston38by the actuator assembly36during its stroke, the base37and stator tube16are forced away from distal end39of the piston38and toward the rotor18.

Because the stroke length of the actuator assembly36may be shorter than the length of the stator tube16, the stator tube removal/installation device34may be required to be adjusted and reactivated in order to fully install the stator tube16about the rotor18. In this case the next step in the installation operation is to deactivate the actuator assembly36such that the piston38reciprocates back from its extended position to its retracted position (see FIG.10). Likewise, the distal end of the tension member52, which is coupled to the piston38, is moved toward the rotor18such that the tension member52is slack. Then, as shown inFIG. 11, the pin17coupling the tension member52and the piston38is removed and the tension member52is pulled through the piston38to remove any slack in the tension member52. The pin17is then repositioned to couple the tension member52and the piston38together. In this manner the working length of the stator tube removal/installation device34can be adjusted to accommodate the new position of the stator tube16relative to the rotor18after the previous stoke of the actuator assembly36.

Referring toFIG. 12, the next step is to reactivate the actuator assembly36such that the piston38and pusher rod40move in the direction of arrow G. Again, when the tension member52is pulled tight between the discharge end of the rotor18and the pin connection to the piston38, the rotor18will exert a resistive force. As a result of force exerted on the piston38by the actuator assembly36, the base37and associated stator tube16will be pushed in the direction of arrow H away from the distal end39of the piston38and toward the rotor18. The step of reactivating or stroking the actuator assembly36is continued until the piston38is moved from its retracted position to its extended position. Accordingly, the stator tube16is slid over the rotor18for a distance approximately equal to a the stroke length of the actuator assembly36.

The steps of deactivating the actuator assembly36, decoupling the tension member52and the piston38, adjusting the longitudinal position of the tension member52with respect to the piston38along the first axis62, coupling the tension member52and the piston38, and reactivating the actuator assembly36, can be repeated as necessary until the stator tube16is installed in the desired position about the rotor18. The stator tube16can then be coupled to the suction chamber12, and the tension member52can be uncoupled from the rotor18. Finally, the stator tube removal/installation device34can be uncoupled from the stator tube16.

Having described the invention in detail and by reference to the preferred embodiment, it will be apparent that modifications and variations thereof are possible without departing from the scope of the invention.