ROTOR / STATOR SET

BACKGROUND TO THE INVENTION

THIS invention relates to a pump with a replaceable rotor / stator set and more particularly, but not exclusively, to a positive displacement pump in which the rotor / stator set can be replaced in situ without having to remove inlet and outlet piping connected to the pump. In a preferred embodiment, the positive displacement pump is a progressive cavity pump.

A positive displacement pump is a fluid displacement device that displaces a fluid by trapping a fixed amount of the fluid, and forcing (displacing) that trapped volume from the inlet end to the discharge end of the pump. Positive displacement pumps, unlike centrifugal pumps, theoretically can produce the same flow at a given speed (RPM) no matter what the discharge pressure. Thus, positive displacement pumps are constant flow machines. A progressive cavity pump is one type of positive displacement pump. It transfers fluid by means of the progress, through the pump, of a sequence of small, fixed shape, discrete cavities, as its rotor is turned. The pump typically comprises a rotor that is mounted on a flexible, rotating shaft. The pump also includes a complementary stator inside which the rotor fits. The rotor and the stator, as well as the flexible shaft, are encapsulated by an extension tube that forms an enclosed volume, and that also acts as an inlet conduit for feeding medium to be pumped to the rotor / stator set of the pump.

The rotor of a progressive cavity pump is of a helical arrangement, and is mounted eccentric to the flexible drive shaft, or alternatively by a coupling rod arrangement. The stator is in the form of a tubular structure of which the inner surface also has a helical profile. The rotor seals against the stator as it rotate, forming a set of fixed-size cavities in between. The cavities move when the rotor is rotated but their shape or volume does not change. The pumped material is moved inside the cavities from an inlet end of the rotor / stator set to an outlet end of the rotor / stator set.

In practice, it is at times required for the rotor and stator (referred to as the rotor/stator set) of the pump to be removed and/or replaced. This may typically be done for repairs or maintenance, or even if a rotor/stator set with different fluid displacement characteristics is required. In an operational environment, the pump is secured to inlet and outlet pipes that are of substantial diameter and therefore not resilient, and which are in themselves furthermore secured to support brackets. It is therefore not that simple to remove the pump, and long spools of piping often have to be removed in order to remove the pump. This significantly complicates the maintenance and/or repair process, which has a negative time and cost implication. It is accordingly an object of the invention to provide a positive displacement pump with a removable rotor/stator set that will, at least partially, alleviate the above disadvantages.

It is also an object of the invention to provide a positive displacement pump which will be a useful alternative to existing positive displacement pumps.

SUMMARY OF THE INVENTION

According to the invention there is provided a positive displacement pump with a replaceable rotor/stator set including:

a porting chamber having a first port which is in use in flow communication with an external conduit, and a second port which is in flow communication with a stator of the rotor/stator set;

a distal end arrangement having a first side which is connectable to the rotor/stator set, and a second side which is connectable to an external conduit;

a rotor/stator set located between the porting chamber and the distal end arrangement, the rotor/stator set having a first end that is in flow communication with the porting chamber, and a second end that is in flow communication with the distal end arrangement;

characterized in that an adjustable coupling is provided between the rotor/stator set and the distal end arrangement, wherein the coupling is adjustable between a connected position in which the coupling connects the rotor/stator set and the distal end arrangement, and a disconnected position in which it allows an end of the rotor/stator set to be displaceable relative to the distal end arrangement. There is provided for the first port of the porting chamber to be an inlet port which is in use in flow communication with a medium to be pumped, and for the second port of the porting chamber to be an outlet port through which fluid to be pumped flows from the porting chamber to the rotor/stator set.

Alternatively, there is also provided for the first port of the porting chamber to be an outlet port through which pumped fluid is discharged, and for the second port of the porting chamber to be an inlet port through which pumped fluid is received from the rotor/stator set.

The distal end arrangement may be a discharge arrangement, in which the first side is an inlet side of the discharge arrangement, and in which the second side is an outlet side of the discharge arrangement.

Alternatively, the first side may be outlet side of the discharge arrangement, and the second side may be an outlet side of the discharge arrangement.

There is provided for the coupling to be in the form of a telescopic coupling that includes a first coupling element and a second coupling element.

The first coupling element may in use be securable to an end of the rotor/stator set, and the second coupling element may in use engage the distal end arrangement.

The first coupling element and the second coupling element may be adjustably securable to one another, in order for an effective length of the coupling to be adjustable, whilst being securable relative to one another in a desired position.

Preferably, the first coupling element includes a sleeve section and a circumferential flange extending from the sleeve section. A first end of the sleeve section is preferably adapted to engage an end of the rotor/stator set, and more particularly to receive an end of the rotor/stator set therein.

There is also provided for a sealing arrangement, for example an O-ring, to be provided between the sleeve of the first coupling element and the end of the rotor/stator set, in order to form a seal between the first coupling element and the end of the rotor/stator set.

Securing apertures may be provided in the flange extending from the sleeve element.

Preferably, the second coupling element includes a sleeve section and a circumferential flange extending from the sleeve section.

A second end of the sleeve section is preferably adapted to engage the distal end arrangement, and more particularly to engage a receiving aperture provided in the distal end arrangement.

There is also provided for a sealing arrangement, for example an O-ring, to be provided between the sleeve of the second coupling element and the securing aperture of the distal end arrangement in order to form a seal between the second coupling element and the distal end arrangement.

There is furthermore provided for ends of the two sleeve sections slidingly to engage one another.

A sealing arrangement may be provided between the two sleeve sections.

Preferably, the second end of the sleeve section of the first coupling element slidingly fits inside the first end of the sleeve section of the second coupling. Location apertures may be provided in the flange extending from the sleeve element of the second coupling element.

The securing apertures on the flange of the first coupling element may be threaded in order to be engaged by a threaded connecting member.

Two diametrically opposed flanges may be provided on each of the first and the second coupling elements.

The distal end arrangement may include a discharge flange formation, and a support bracket.

The discharge flange formation defines a flange that can be secured to external discharge piping.

A proximal discharge opening is provided in the discharge flange, and a receiving groove, suitable for receiving the second end of the sleeve section of the second coupling, extends circumferentially about the discharge opening.

A sealing arrangement, for example an O-ring, may be provided between the discharge flange formation and the second end of the sleeve section of the second coupling. Preferably, the sealing arrangement is located in the receiving groove.

The support bracket of the discharge arrangement may include a substantially U-shaped bracket, with a plurality of securing apertures provided through the brackets for receiving tie-rods (for securing the discharge arrangement to the porting chamber) therethrough.

Preferably three securing apertures are provided. According to a further aspect of the invention there is provided an adjustable coupling suitable for use with a positive displacement pump that includes a rotor/stator set located next to a distal end arrangement, wherein the coupling is adjustable between a connected position in which the coupling connects the rotor/stator set and the distal end arrangement, and a disconnected position in which it allows an end of the rotor/stator set to be displaceable relative to the distal end arrangement.

The adjustable coupling may be in the form of a telescopic coupling comprising a first coupling element and a second coupling element, the coupling elements having complementary sleeve sections, one of which is configured and dimensions slidingly to fit inside the other.

According to a further aspect of the invention there is provided a method of removing a rotor/stator set from a positive displacement pump, the method including the steps of:

reducing the length of an adjustable coupling located between and end of the rotor/stator set and a distal end arrangement;

removing the coupling from an end of the rotor/stator set;

disconnecting an opposing end of the rotor/stator set from a drive shaft of the pump; and

removing the rotor/stator set from the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention is described by way of a non- limiting example, and with reference to the accompanying drawings in which:

Figure 1 is a schematic exploded perspective view of a distal end arrangement or discharge arrangement forming part of the pump in accordance with one embodiment of the invention;

Figure 2 shows the exploded perspective view of Figure 1 from an outlet end of the pump;

Figure 3 is an exploded perspective view of a pump in accordance with one embodiment of the invention; is a cross-sectional side view of the pump of Figure 3 with the adjustable coupling in an expanded position, and with the rotor/stator set in an engaged position;

Figure 5 is the cross-sectional side view of Figure 4 in which the adjustable coupling has been displaced to a collapsed position in order for the rotor/stator set to be in a disengaged position;

Figure 6 shows the pump of Figure 5 with the coupling removed;

Figure 7 shows the pump of Figure 6 with the rotor/stator set and the drive shaft having been displaced towards the discharge arrangement in order to provide access to the pin that connects the rotor to the drive shaft; Figure 8 shows the cross-sectional side view of the pump of Figure 5 with the rotor/stator set having been removed from the pump housing;

Figure 9 is an exploded cross-sectional side view of the pump of

Figure 4;

Figure 10 is a further embodiment of a first coupling element of an adjustable coupling of the pump of Figure 1 ;

Figure 11 is a further embodiment of a second coupling element of an adjustable coupling of the pump of Figure 1 ;

Figure 12 shows the coupling, comprising the coupling elements of

Figures 10 and 11 , in use; and

Figure 13 is a perspective view of the coupling including a protective bellows.

DETAILED DESCRIPTION OF INVENTION

Referring to the drawings, in which like numerals indicate like features, a non-limiting example of a positive displacement pump with a removable rotor/stator set in accordance with the invention is generally indicated by reference numeral 10. More particularly, the positive displacement pump is a progressive cavity pump suitable for surface use.

The pump 10 includes a porting chamber 20 having a first port, which in this embodiment is an inlet or suction port 21 that is in use connected to inlet or suction piping (not shown). It is desirable to be able to replace the rotor/stator set 40 of the pump without having to remove the inlet piping (not shown) from the inlet port 21 of the porting chamber 20. The porting chamber 20 also includes a second port, which in this embodiment is an outlet port 22 that is in flow communication with a rotor/stator set 40 of the pump 10. An adaptor ring 23 is secured to the outlet 22 of the porting chamber 20 and is used to secure the porting chamber 20 to a distal end arrangement, which in this embodiment is a discharge arrangement 30, as is described in more detail below. Apertures 24, for receiving tie rods 70, are provided in the adapter ring 23. In one embodiment of the invention three equispaced circumferential apertures 24 are provided, as this arrangement enables better access to the rotor/stator set 40 of the pump, compared to conventional four tie rod arrangements. It is, however, foreseen that any number of tie rods 70 could be used, and the conventional four tie rod design will therefore still be relevant.

A distal end arrangement, which in this embodiment is a discharge arrangement 30, is provided at an opposing end of the pump 10, and the rotor/stator set 40 of the pump is in use sandwiched between the discharge arrangement 30 and the porting chamber 20. The discharge arrangement 30 includes a discharge flange formation 31 which will in use be secured to outlet or discharge piping (not shown) through which a medium pumped by the pump will be conveyed away from the pump. As is the case for the inlet piping, it is desirable to be able to remove the rotor/stator set 40 without having to remove the outlet piping. The discharge flange formation 31 includes a flange 32 that mates with a complementary flange (not shown) provided on the outlet piping (not shown), as well as a number of apertures provided in the flange for securing the outlet piping and the flange 32 to one another. A discharge opening 33 is provided in a proximal zone of the flange 32, and is in use aligned with an outlet of a rotor/stator set 40 of the pump 10. A receiving groove 34 (best seen in the figures 1 and 5) is provided, and snugly receives an end of an adjustable coupling 50 as described in more detail below. A seal is formed between the discharge flange 32 and the adjustable coupling 50, and more particularly a seal (for example in the form of an O-ring) may be provided in the receiving groove 34. The discharge arrangement 30 also includes a support bracket 35 which is used to secure the discharge arrangement 30 to the porting chamber 20 by way of tie rods 70. Securing apertures 36 are provided for this purpose.

The pump 10 also includes a rotor/stator set 40 as is known in the art. The internal configuration of the rotor/stator set 40 can take many different forms and the detail design of the rotor/stator set is therefore not important in so far as this invention is concerned. The rotor/stator set 40 has a first end 41, which is in use disposed adjacent the porting chamber 20, and a second end 42, which is in use disposed adjacent the discharge arrangement 30. A rotor end 15 extends from the first end 41 of the rotor/stator set 40 and is in use secured to, and driven by, a drive shaft 14 of the drive arrangement (not shown) of the pump 10. The second end 42 of the rotor/stator set 40 is secured to, and brought into fluid commutation with, the discharge arrangement 30 by way of an adjustable coupling 50. The adjustable coupling 50 sealingly secures the second end 42 of the rotor/status set 40 to the discharge flange formation 31 in a configuration in which the rotor/stator set 40 can be removed from the pump 10 without the porting chamber 20 or the discharge arrangement 30 having to be displaced at all. This means that the rotor/stator set 40 will be removable from the pump without having to remove the inlet piping and the outlet piping connected to the porting chamber and the discharge arrangement respectively.

The adjustable coupling 50, which is best seen in figures 1 and 2, comprises a first (moving) coupling element 51 and a second (stationary) coupling element 55. The first coupling element 51 comprises a sleeve section 52 having a first end 52.1 and an opposing second end 52.2. A circumferential flange 53 extends partially about the first end 52.1 of the sleeve section 52 and securing apertures are provided therethrough. The second coupling element 55 also includes a sleeve section 56. The sleeve section 56 has a first end 56.1 and an opposing second end 56.2, with a circumferential flange 57 extending about the first end 36.1. The second end 52.2 of the sleeve section 52 of the first coupling element 51 is configured and dimensioned slidingly to fit inside the first end 56.1 of the sleeve section 56 of the second coupling element 55. This telescopic movement between the first coupling element 51 and the second coupling element 55 renders the coupling 50 adjustable, and more particularly adjustable between an extended or connected position as shown in Figure 4, and a contracted or disconnected position as shown in Figure 5. A seal (not shown) may be provided between an outer surface of the sleeve section 52 of the first coupling element 51 and the inner surface of the sleeve section 56 of the second coupling element 55.

The first coupling element 51 is furthermore configured and dimensioned in order to receive the second end 42 of the rotor/stator set 40 inside the first end 52.1 thereof. The second end 56.2 of the sleeve section 56 of the second coupling element 55 is in turn configured and dimensioned to fit inside the receiving groove 34 provided in the flange 32 of the discharge arrangement 30. Therefore, when the coupling 50 engages the discharge arrangement 30 as well as the rotor/stator set 40, and the coupling is in an extended position, a sealed fluid flow conduit will be formed thereby. Jacking bolts 60 are used to retain the adjustable coupling 50 in a desired configuration, and also to displace the adjustable coupling between the extended (or connected) position and the collapsed (or disconnected) position.

A further embodiment of the coupling 50 is now described with reference to Figures 10 to 13. Conceptually, the coupling is the same as the coupling shown schematically in Figures 1 and 2. The first coupling element 51 , shown in Figure 10, includes two stepped circumferential grooves (81 and 82) that are provided in the first end 52.1 thereof. In use, the outer groove 81 will receive a metal outer tube 44 of the rotor/stator set 40, and the inner groove 82, will receive the end of the stator 45 of the rotor/stator set 40, as is shown in Figure 12. In addition, there is provided for locating pins 83 to extend longitudinally outwardly from the inner groove 82, which pins will in use engage complementary apertures 46 (in the form of holes or a groove) formed in the end of the stator 45. The second coupling element 55 is essentially the same as the one shown in Figures 1 and 2, but with the notable addition of a pressure gauge port 59 and an O-ring groove 84. Finally, as is shown in Figure 13, the coupling also includes a protective rubber bellows 100 which will protect the coupling against the ingress of dirt and other contaminants, whilst still allowing relative movement between the first coupling element 51 and the second coupling element 55.

The process of removing the rotor/stator set 40 of the pump 10 will now be described with reference to all the figures, and in particular to Figures 4 to 8. The first step in the removal processes is to remove the end cover (not shown) on the drive side of the pump. This is followed by the removal of the locking tab (not shown) and finally the connecting pin (not shown), which will then allow a drive end of the drive shaft 14 to be removed. This is a procedure that is frequently used during pump maintenance, and is therefore not new or inventive per se. Next, the adjustable coupling 50 will be displaced from a connected, expanded position (shown in Figure 4) to a disconnected, collapsed position (as is shown in Figure 5) in order to release the second end 42 of the rotor/stator set 40 from the first end 52.1 of the first coupling element 51. This is done by rotating the jacking bolts 60, which then urges the first coupling element 51 towards the second coupling element 55. Once the adjustable coupling 50 has been displaced to the collapsed position, it can also be removed from the flange 32 of the discharge arrangement 30 and can subsequently be removed from the pump altogether, as is shown in Figure 6. At this point the second end 42 of the rotor/stator set 40 will be released from the discharge arrangement 30, but the first end 41 will still be secured to a drive shaft 14 of the pump 10. More particularly, a rotor end 15 extending from the first end 41 of the rotor/status set 40 will still be secured to the drive shaft 14. The additional space created between the second end 42 of the rotor/stator set 40 and the flange 32 of the discharge arrangement 30 now allows the rotor/stator set 40, as well as the drive shaft 14, to be slidably displaced towards the discharge arrangement 30, as is shown in Figure 7. The displacement of the rotor/starter set 40 provides access to the cap and pin that secures the drive shaft 14 to the rotor end 15. The cap and pin can therefore be removed, following the same process as removing the cap and pin on the other side of the drive shaft, and the rotor/stator set 40 can then be removed from the pump altogether, as is shown in Figure 8. In this way, the rotor/status set 40 can be removed without having to remove the entire pump, and therefore without having to remove any of the connecting pipework. The rotor/stator set 40 can be replaced by inverting the removal process as described above.

The inventor foresees that the new pump, and the new rotor/stator set removal procedure, will result in a significant reduction of downtime due to the fact that the entire pump 10 does not have to be removed when there is a requirement only to remove the rotor/status set 40 of the pump.

The above example shows and describes and embodiment where the pump run in a first direction, and in which the pump inlet is on the porting chamber side. However, it should be appreciated that these type of pumps can run in both directions, and that the porting chamber can in the inverse operational configuration be the discharge end, whereas the distal end arrangement (described as the discharge arrangement above) can be the inlet end. The same principle of the removable rotor/stator set will however be applicable. It will be appreciated that the above is only one embodiment of the invention and that there may be many variations without departing from the spirit and/or the scope of the invention.