MODULAR, MULTI-STAGE, INTEGRAL SEALED MOTOR PUMP WITH INTEGRALLY-COOLED MOTORS AND INDEPENDENTLY CONTROLLED ROTOR SPEEDS

Abstract

An integral motor pump module directs at least 90% of its rotor discharge over at least 50% of its motor housing surface, thereby cooling the motor with little or no need for a separate flow path. The discharge can flow through an annulus formed between the motor and pump housings, and can extend over substantially all of the sides and rear of the motor housing. The rotor can be fixed to a rotating shaft, or rotate about a fixed shaft, which can be threaded into the motor and/or module housing. A plurality of the modules can be combined into a multi-stage pump, with rotor speeds independently controlled by corresponding variable frequency drives. The motor can be a radial or axial permanent magnet or induction motor. A separate cooling flow can provide additional cooling e.g. when pumping heated process fluids. Embodiments include guide vanes and/or diffusers.

Claims

1. A pump module having an integral motor, the pump module comprising: a module housing; a rotor suspended within the module housing, a front face of the rotor being oriented toward a proximal end of the pump module; a motor within the module housing, the motor being configured to drive a rotation of the rotor, the motor comprising: a motor housing located within the module housing; a stator within the motor housing, the stator comprising an electromagnet directed toward the rotor; and a magnetic device fixed to the rotor and configured to pass in proximity to the electromagnet as the rotor rotates; and a process flow path extending between the module housing and the motor housing over a length of the motor housing, and over at least 20% of a surface of the motor housing, the process flow path being configured such that at least 80% of the process fluid that flows through the pump module from a module inlet to a module outlet is caused by the rotor to flow through the process flow path in direct physical contact with the motor housing.

2. The pump module of claim 1, wherein the rotor is a centrifugal rotor configured to drive the process fluid from a central region thereof to a periphery thereof.

3. The pump module of claim 1, wherein the rotor is suspended by a rotatable shaft, and the rotor is fixed to the shaft.

4. The pump module of claim 1, wherein the rotor is suspended by a fixed shaft, and the rotor is configured to rotate about the shaft.

5. The pump module of claim 4, wherein the rotor is supported on the fixed shaft by a pair of bearings, one of which maintains an axial position of the rotor while the other of which provides radial support of the rotor.

6. The pump module of claim 4, wherein the rotor is supported on the fixed shaft by a single, one-way thrust bearing.

7. The pump module of claim 4, wherein the rotor is supported on the fixed shaft by at least one bearing that is lubricated by the process fluid.

8. The pump module of claim 4, wherein the fixed shaft is fixed to at least one of the motor housing and the module housing.

9. The pump module of claim 4, wherein the fixed shaft is fixed to at least one of the motor housing and the module housing by threaded attachment.

10. The pump module of claim 1, wherein the magnetic device fixed to the rotor is a permanent magnet.

11. The pump module of claim 1, wherein the magnetic device fixed to the rotor is a squirrel cage coil.

12. The pump module of claim 1, wherein the process flow path extends over at least 50% of a surface of the motor housing, and at least 90% of the process fluid that flows through the pump module from the module inlet to the module outlet is caused to flow through the process flow path in direct physical contact with the motor housing.

13. The pump module of claim 1, wherein the process flow path extends over at least 90% of an entire circumference of the motor housing.

14. The pump module of claim 1, wherein the process flow path is the only flow path within the pump module through which the process fluid flows from the module inlet to the module outlet.

15. The pump module of claim 1, further comprising a cooling flow path distinct from the process flow path, the cooling flow path being configured to enable an exchange of heat between the motor housing and a cooling fluid that is lower in temperature than the process fluid flowing in the process flow path.

16. The pump module of claim 1, further comprising guide vanes within the process flow path that are configured to direct flow of the process fluid through the flow path.

17. The pump module of claim 1, wherein the stator is configured to rotate independently of the rotor and in a direction that is opposite to a rotation of direction of the rotor.

18. The pump module of claim 1, further comprising a diffuser that is cooperative with the rotor but is driven by a separate diffuser motor and is thereby able to rotate independently of the rotor.

19. The pump module of claim 1, wherein the motor is a radial motor, whereby the electromagnet is directed toward a radial periphery of the rotor; and the magnetic device is fixed near the radial periphery of the rotor.

20. The pump module of claim 1, wherein the motor is an axial motor, whereby the electromagnet is directed toward a distal side of the rotor; and the magnetic device is fixed to the distal side of the rotor.

21. A pump comprising a plurality of interconnected pump modules according to claim 1.

22. The pump of claim 21, wherein at least two of the motors of the pump modules can be independently controlled so as to cause the corresponding rotors to rotate at different rates.

23. The pump of claim 22, wherein the two, independently controlled pump modules are controlled by separate variable frequency drives.

24. The pump of claim 22, wherein all of the pump modules can be independently controlled.

25. The pump of claim 24, wherein each of the pump modules is controlled by a corresponding variable frequency drive.

26. The pump of claim 21, wherein all of the pump modules are substantially identical to each other.

27. The pump of claim 21, wherein at least two of the rotors of the pump modules are supported by a common shaft.

28. The pump of claim 27, wherein the shaft is a rotatable shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 is a cross-sectional illustration drawn to scale of a prior art two-stage integral motor pump cooled by a dedicated cooling flow;

[0044] FIG. 2A is a cross-sectional, simplified illustration of a single-stage module of the present invention having a radial motor design;

[0045] FIG. 2B is a cross-sectional illustration drawn to scale of a two-stage embodiment of the present invention having an axial motor design;

[0046] FIG. 3 is a cross-sectional illustration drawn to scale of an embodiment similar to FIG. 2, but including a separate cooling flow path (cooling path not drawn to scale);

[0047] FIG. 4 is a cross-sectional illustration drawn to scale of an embodiment similar to FIG. 2, but including guide vanes in the process flow path; and

[0048] FIG. 5 is a perspective view drawn to scale of the outer housing of the pump of FIG. 2.

DETAILED DESCRIPTION

[0049] The present invention is an integral motor pump or pump module that is configured to direct the discharge of process fluid from a rotor over the surface of the integral motor housing, thereby reducing or eliminating any need for a separate, dedicated motor cooling flow path. For example, in the embodiment of FIG. 2A, the discharge 202 from the rotor 206 is directed to pass over and around the motor housing 204 of the module, so that the motor 212 is directly cooled by the discharge of the impellor 206, and does not require a separate, dedicated cooling fluid path.

[0050] In embodiments, more than 80% of the fluid that enters the module inlet 222 is directed through the discharge path 202 to the module outlet 224, and at least 20% of the motor housing 204 is in direct contact with the discharge path 202. In embodiments, more than 90% of the fluid that enters the module 200 flows from the inlet 222 to the outlet 224 through the discharge path 202 and at least 50% of the motor housing 204 is in direct contact with the discharge path 202.

[0051] In the two-module pump 220 of FIG. 2B, a central axis of the motor 212 in each stage is substantially collinear with the stationary shaft 208 about which the rotor 206 is rotated, such that the process fluid from the rotor 206 flows axially over the motor housing 204 through an annular region 202 formed between the motor housing 204 and the pump housing 218, whereby at least 90% of an axially-centered circumference of the motor housing 204 is in direct contact with the process fluid. In the embodiment of FIG. 2, the annular discharge flow region 202 surrounds substantially the entire circumference of the motor housing 204 in each stage, so that substantially the entire circumference of the motor housing 204 along its length and rear surface is in direct contact with the process fluid.

[0052] In the embodiment of FIG. 2A, the rotor 206 is fixed to a rotating shaft, while in the embodiment of FIG. 2B, it rotates on bearings 214 about a stationary shaft 208, which in the embodiment of FIG. 2B is threaded into the motor housing 204. In similar embodiment, the shaft 208 is threaded or otherwise supported by the pump or pump module housing 218, or by any combination of the pump or pump module housing 218 and the motor housing 204. In still other embodiments, there is no shaft, and instead a wear ring clearance on the front of the impeller acts as the primary radial and axial bearing.

[0053] In embodiments, the disclosed module is implemented as a single stage pump, while in other embodiments, such as FIG. 2B, a plurality of the disclosed modules are combined to form a multi-stage pump. While only two stages are shown in FIG. 2B for convenience of illustration, it will be understood that embodiments are extendable to an arbitrary number of pump stages. In some of these embodiments, the rotor 206 in each stage is independently driven, such that the rotor speed of each stage can be separately controlled. For example, a separate variable frequency drive (VFD) 216 can be dedicated to the control of each stage of the pump.

[0054] In the embodiment of FIG. 2B, in each stage of the pump 220 a plurality of permanent magnets 210 are attached to a rear side of the rotor 206, and are caused to pass close to electromagnetic coils 212 of an adjacent stator 214 as the rotor 206 is rotated. Rotors 206 in other embodiments include induction motors that utilize non-permanent magnets 210 such as squirrel cage rotor coils in which currents are induced by the stator electromagnets 212 during pump operation. Torque is thereby transmitted directly from the electromagnet motor coils 212 to the rotor 206 without the use of a rotating shaft. In embodiments, the motor coils 212 are sealed from the working fluid using static sealing methods 204, which eliminates any need for dynamic mechanical seals, and avoids the problems of alignment, leakage, and/or maintenance that would otherwise arise therefrom.

[0055] Axial and radial locating of the rotor 206 is provided in the embodiment of FIG. 2 by product-lubricated bearings 214 in each rotor stage. By using individual bearings 214 for each rotor stage, the bearings 214 in each stage can be designed to handle the loads from that stage only, and the risk of overloading bearings from combined stage loading in a multistage arrangement is completely eliminated. Using the working fluid as a lubricant for the bearings 214 in embodiments eliminates the need for an external oil lubrication system and greatly simplifies the overall pump design.

[0056] With reference to FIG. 3, motor cooling in embodiments directed to pumping of heated process fluid can be further augmented by including an externally cooled fluid path 300 through which either process fluid or a separate, dedicated cooling fluid is circulated. Fluid cooling of the motor allows higher performance limits and greater power density in the overall pump.

[0057] With reference to FIG. 4, embodiments include guide vanes. In the illustrated embodiment, guide vanes 400 control the flow of the process fluid in a section of the flow path 202 at the end of the motor 212 that turns radially inward toward the centerline of the module. The guide vanes 400 break the flow path into a plurality of separate but symmetric passages until the flow reaches the centerline and flows axially into the next stage. In embodiments, the guide vanes 400 direct the process fluid within the flow path 202 into close proximity with the motor housing 218. The guide vanes 400 can also provide a casing wall that can be used to route power cables from the sealed motor cavity 212, through the fluid passages 202, and out of the pump casing 218 to the variable frequency control 216. In embodiments, the guide vanes 400 can also act as fins to provide additional convective surface area to cool the motor 212, and/or to provide space for integral cooling passages 300 connected to an external cooling fluid source.

[0058] In the embodiments of FIGS. 2B-4, the pump 220 includes a plurality of completely modular pump stages. While only two stages are shown in these figures, it can be easily seen that any number of the stages can be combined in series without adding additional complexity or complication to the design, operation, and maintenance of the pump 220. In particular, high stage counts according to the disclosed design do not raise any issues regarding shaft size, shaft deflection, rotordynamics, bearing loads, motor alignment, or alignment between stages. FIG. 5 is a perspective view of the pump of FIG. 2.

[0059] With reference again to FIGS. 2B and 4, embodiments include a plurality of variable frequency drives (VFD's) 216, and in some of these embodiments the motor 212 in each stage of the pump is independently controlled by a dedicated VFD 216. One of the key benefits in some of these embodiments is that the first stage can run at lower speeds than the rest of the pump, so as to accommodate low net positive suction head (NPSH) and off-peak conditions. In some applications, varying the speed of only the final stage provides a useful approach precisely controlling the output pressure and/or flow.

[0060] Providing individual VFD drives 216 for each stage can also serve as a fail-safe redundancy, whereby if one stage fails, the rest will continue to operate and the pump will continue to function. The continued function after failure of a pump stage may be with reduced head and flow, or the speed of the remaining stages can be increased to compensate for the lost head and flow of the failed stage. This approach creates a failure scenario wherein the pump continues to operate, possibly at reduced head and flow, until an operator, after becoming aware of the stage failure, has time to safely shut down the system. In contrast, the failure of one stage in a traditional pump typically results in failure of the entire pump, with a complete loss of performance and a sudden, uncontrolled shutdown of the system.

[0061] In the embodiment of FIG. 2A, the motor is a radial motor that includes permanent magnets mounted about the periphery of the rotor, while the embodiments of FIGS. 2B-4 include motors in each pump stage that are disk or pancake style motors that include permanent magnets 210 mounted on the rear surfaces of the rotors 206. Induction motors are used in other embodiments. Some embodiments include variable speed drives that enable the synchronous operating speeds of the pump stages to rise above 3600 rpm.

[0062] In the embodiment of FIGS. 2A-5 the pump stages are centrifugal designs having radial flow impellers 206. Some of these embodiments include impellers with specific speeds below about 2,000 US units. Other embodiments include pump stages with radial flux motor designs.

[0063] In the embodiment of FIGS. 2B-4, combined radial and one-way thrust bearings 214 are used in place of separate axial and radial bearings. The illustrated embodiments include stationary shafts 208 inserted through the hubs of the impellers 206 and threaded into the pump stage housing 218, which facilitate easy assembly and maintenance without special tools. Using a sensor-less motor along with appropriate VFD drives 216 also reduces any requirement for instrumentation on each stage in the illustrated embodiments.

[0064] Certain embodiments include stages having an inverted rotor/stator configuration, whereby the rotor and the stator can both rotate independently from each other in opposite directions. And some embodiments include a plurality of rotors fixed to a common fixed or rotating shaft, combined in some embodiments with stators and/or diffusers that rotate individually, for example with separate motors driving the rotors and diffusers. In some of these embodiments, the diffusers are implemented in a manner similar to the disclosure of patent application U.S. Ser. No. 15/101,460.

[0065] The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. Each and every page of this submission, and all contents thereon, however characterized, identified, or numbered, is considered a substantive part of this application for all purposes, irrespective of form or placement within the application. This specification is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure.

[0066] Although the present application is shown in a limited number of forms, the scope of the invention is not limited to just these forms, but is amenable to various changes and modifications without departing from the spirit thereof. The disclosure presented herein does not explicitly disclose all possible combinations of features that fall within the scope of the invention. The features disclosed herein for the various embodiments can generally be interchanged and combined into any combinations that are not self-contradictory without departing from the scope of the invention. In particular, the limitations presented in dependent claims below can be combined with their corresponding independent claims in any number and in any order without departing from the scope of this disclosure, unless the dependent claims are logically incompatible with each other.