Patent Application
20230358238
The disclosed concept pertains generally to canned motor pumps, and more particularly to canned motor pumps having arrangements therein for preventing damage to the stator thereof in the event of a bearing failure. The disclosed concept further pertains to arrangements for use in preventing damage to bearings, and more particularly to arrangements used in canned motor pumps for preventing damage to bearings associated therewith. The disclosed concept further relates to kits for retrofitting canned motor pumps with arrangements for preventing damage to the stator thereof in the event of a bearing failure.
Canned motor pumps are known for long life under normal operation. A canned motor pump is a pump and electric motor positioned/connected on a common shaft. The rotating element consists of an impeller, a shaft, and an assembly of electrical components referred to as the rotor. The rotor may be of differing arrangements. For example, without limitation, the rotor may be a squirrel cage induction type with laminations, rotor bars, and end rings, all enclosed by a thin cylindrical metal sheet referred to as the rotor can.
The stationary portion of the electric motor is the stator, and consists of magnet wire and laminations, and is also enclosed in a cylindrical metal can (stator can). The aforementioned cans (i.e., rotor and stator cans) protect the electrical parts of the motor from the process fluid, which is circulated within the motor as a coolant. Typically the rotor is supported by two or more radial bearings that center the rotor within the stator and provide stability and electrical balancing. A flaw of conventional canned motor pumps is that when the radial bearings wear, the annular gap between the stator and rotor closes, causing the stator and rotor to contact, typically resulting in tearing of the stator can and the influx of process fluid. The influx of process fluid causes the motor to short. Such failure is a very expensive failure when it occurs. Depending on the process fluid, the stator may be fouled and not recoverable for repair.
Hence, there exists a need for an improved arrangement that reduces and/or eliminates such failures that commonly result from wear of the radial bearings.
Embodiments of the disclosed concept address shortcomings of conventional arrangements by providing solutions that reduce/eliminate failures that commonly result from wear of a radial bearing or bearings. As one aspect of the disclosed concept, a limit ring for use in a pump arrangement is provided. The limit ring comprises: a cylindrical body positioned about a central longitudinal axis and having a first end and an opposite second end; a central passage defined through the cylindrical body centered about, and extending along the longitudinal axis between the first end and the second end, the central passage having a circular cross section when viewed along the longitudinal axis; and a number of channels defined in the cylindrical body radially outward from the central passage, each channel extending between the first end and the second end.
The number of channels may comprise a plurality of channels.
Each channel of the number of channels may open into the central passage.
Each channel of the number of channels may open outward from the cylindrical body.
Each channel of the number of channels may extend in a straight line parallel to the longitudinal axis.
The cylindrical body may be formed from a high friction material.
As another aspect of the disclosed concept, a canned motor pump is provided. The canned motor pump comprises: a main housing; a rotor having a shaft extending from both a first end and an opposite second end of the rotor; a first radial bearing positioned in a first bearing support coupled to the main housing, the first radial bearing supporting the shaft extending from the first end of the rotor; a second radial bearing positioned in a second bearing support coupled to the main housing, the second radial bearing supporting the shaft extending from the second end of the rotor; a stator having a generally tubular shape positioned within the main housing radially outward from the rotor such that an annular gap is defined between the rotor and the stator; and a limit ring positioned adjacent at least one of the first or second radial bearings, wherein the limit ring comprises: a cylindrical body positioned about a central longitudinal axis and having a first end and an opposite second end; a central passage defined through the cylindrical body centered about, and extending along the longitudinal axis between the first end and the second end, the central passage having a circular cross section when viewed along the longitudinal axis; and a plurality of channels defined in the cylindrical body radially outward from the central passage, each channel extending between the first end and the second end, wherein the limit ring is positioned about the shaft extending from one of the first end of the rotor or the second end of the rotor such that the shaft extends through the central passage of the limit ring, and wherein a portion of the limit ring between a pair of the channels is spaced a distance from an adjacent portion of the canned motor pump that is less than a minimum distance between the rotor and the stator.
Each channel of the plurality of channels of the limit ring may open into the central passage of the limit ring.
Each channel of the plurality of channels of the limit ring may open outward from the cylindrical body of the limit ring.
Each channel of the plurality of channels may extend in a straight line parallel to the longitudinal axis.
The cylindrical body of the limit ring may be formed from a high friction material.
The limit ring may be a first limit ring; the first limit ring may be positioned adjacent the first radial bearing and positioned about the shaft extending from the first end of the rotor such that the shaft extends through the central passage of the first limit ring; the canned motor pump may comprise a second limit ring that comprises: a cylindrical body positioned about a central longitudinal axis and having a first end and an opposite second end; a central passage defined through the cylindrical body centered about, and extending along the longitudinal axis between the first end and the second end, the central passage having a circular cross section when viewed along the longitudinal axis; and a plurality of channels defined in the cylindrical body radially outward from the central passage, each channel extending between the first end and the second end; the second limit ring positioned adjacent the second radial bearing about the shaft extending from the second end of the rotor such that the shaft extends through the central passage of the second limit ring; and a portion of the second limit ring between a pair of the channels of the second limit ring is spaced a distance from an adjacent portion of the canned motor pump that is less than the minimum distance between the rotor and the stator.
The limit ring may be positioned in one of the first bearing support or the second bearing support; each channel of the plurality of channels of the limit ring may open into the central passage of the limit ring; and the portion of the limit ring between the pair of the channels of the limit ring may be spaced the distance from the shaft extending from the first end of the rotor or the second end of the rotor.
The limit ring may be positioned in a portion of the stator; each channel of the plurality of channels of the limit ring may open into the central passage of the limit ring; and the portion of the limit ring between the pair of the channels of the limit ring may be spaced the distance from the shaft extending from the first end of the rotor or the second end of the rotor.
The limit ring may be positioned about the shaft extending from the first end of the rotor or the second end of the rotor; each channel of the plurality of channels of the limit ring may open outward from the cylindrical body of the limit ring; and the portion of the limit ring between the pair of the channels of the limit ring may be spaced the distance from a portion of the stator.
As yet a further aspect of the disclosed concept, a kit for retro-fitting a canned motor pump is provided. The kit comprises: a limit ring comprising: a cylindrical body positioned about a central longitudinal axis and having a first end and an opposite second end; a central passage defined through the cylindrical body centered about, and extending along the longitudinal axis between the first end and the second end, the central passage having a circular cross section when viewed along the longitudinal axis; and a number of channels defined in the cylindrical body radially outward from the central passage, each channel extending between the first end and the second end; and a bearing support having a first portion structured to house the limit ring therein and a second portion structured to be coupled to a housing of the canned motor pump.
The kit may further comprise a radial bearing and the bearing support may be further structured to house the radial bearing therein adjacent the limit ring.
The kit may further comprise a second limit ring comprising: a cylindrical body positioned about a central longitudinal axis and having a first end and an opposite second end; a central passage defined through the cylindrical body centered about, and extending along the longitudinal axis between the first end and the second end, the central passage having a circular cross section when viewed along the longitudinal axis; and a number of channels defined in the cylindrical body radially outward from the central passage, each channel extending between the first end and the second end.
The kit may further comprise a second bearing support having a first portion structured to house the second limit ring therein and a second portion structured to be coupled to the housing of the canned motor pump.
The kit may further comprise a second radial bearing and the second bearing support may be further structured to house the second radial bearing therein adjacent the second limit ring.
These and other objects, features, and characteristics of the disclosed concept, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the disclosed concept.
As used herein, the singular form of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. As used herein, the statement that two or more parts or components are “coupled” shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, “directly coupled” means that two elements are coupled in direct contact with each other. As used herein, “fixedly coupled” or “fixed” means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other.
Directional phrases used herein, such as, for example and without limitation, top, bottom, left, right, upper, lower, front, back, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.
As used herein, the statement that two or more parts or components “engage” one another shall means that the parts exert a force against one another either directly or through one or more intermediate parts or components.
As used herein, the word “unitary” means a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body.
As used herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
As used herein, a “coupling assembly” includes two or more couplings or coupling components. The components of a coupling or coupling assembly are generally not part of the same element or other component. As such, the components of a “coupling assembly” may not be described at the same time in the following description.
As used herein, “correspond” indicates that two structural components are sized and shaped to be similar to each other and may be coupled with a minimum amount of friction. Thus, an opening which “corresponds” to a member is sized slightly larger than the member so that the member may pass through the opening with a minimum amount of friction. This definition is modified if the two components are said to fit “snugly” together or “snuggly correspond.” In that situation, the difference between the size of the components is even smaller whereby the amount of friction increases. If the element defining the opening and/or the component inserted into the opening is/are made from a deformable or compressible material, the opening may even be slightly smaller than the component being inserted into the opening (i.e., an interference fit). This definition is further modified if the two components are said to “substantially correspond.” “Substantially correspond” means that the size of the opening is very close to the size of the element inserted therein. That is, not so close as to cause substantial friction, as with a snug fit, but with more contact and friction than a “corresponding fit,” i.e. a “slightly larger” fit.
A top view of a pump arrangement 10 including a canned motor pump 12 in accordance with one example embodiment of the disclosed concept is shown in
Continuing to refer to
Continuing to refer to
Each limit ring 28 and associated radial bearing 18 are aligned by a respective bearing support 24 or 26 about shaft 16 to provide tightly controlled running clearances. Each limit ring 28 functions to prevent contact between rotor 14 and stator 20 in the event of failure of one or both of radial bearings 18 by supporting shaft 16 before such contact between rotor 14 and stator 20 can occur. Accordingly, in the example shown in
Each limit ring 28 is formed from a high friction material that increases amp draw due to drag on rotating shaft 16 when shaft 16 engages limit ring 28, thus tripping power to the motor before the bearing(s) is/are destroyed. In example embodiments of the disclosed concept, limit rings 28 formed from non-asbestos organics (NAOs, e.g., brake pad material) and ceramics, although other materials that can both provide abrasive friction to the metal shaft 16 may be employed without varying from the scope of the disclosed concept. For example, semi-metallics containing metallic fibers in a non-metallic binder that provides abrasive friction may be employed. Additionally, varying the surface finish of shaft 16 and the limit ring 28 can also increase friction between limit ring 28 and shaft 16. When installed about shaft 16, the arrangement of channels 40/lobes 42 of limit ring 28 provides for a limited number of close touch points between shaft 16 and limit ring 28 such that coolant can flow through channels 40 with very little to no impedance.
As a non-limiting example, in one embodiment of a canned motor pump 12 in accordance with the disclosed concept, an annular gap AG2 between rotor 14 and stator 20 of 0.026 inches was employed with a bearing clearance of 0.002 inches. The annular gap AG1 between cylindrical body 30 of limit ring 28 and shaft 16 is set at a point that is greater than maximum bearing clearance but less than the rotor-to-stator clearance, i.e. AG2. In this example, annular gap AG1 was set at 0.016 inches so that in the event of a bearing failure shaft 16 contacts limit ring 28 before rotor 14 contacts stator 20 and initiates the motor current and vibration previously noted. Although shown with limit ring 16 positioned between radial bearing 18 and rotor 14, it is to be appreciated that limit ring 16 may be positioned axially outward from radial bearing 18 (i.e., radial bearing 18 positioned between limit ring 16 and rotor 14) without varying from the scope of the disclosed concept.
Unlike the previous example embodiments, in the example embodiment of
Embodiments of the disclosed concept may readily be provided in a “kit” form for retrofitting pre-existing canned motor pumps. For example, a kit 50 or 52 including all or some of the components shown in
From the foregoing examples it is to be appreciated that embodiments of the disclosed concept provide arrangements that prevent rotor/stator contact in the event of a bearing failure in a canned motor pump. As such arrangements serve as a passive safety feature, embodiments of the disclosed concept can be readily integrated with existing safety systems in new pumps and/or existing applications. Although described in conjunction with canned motor pumps, it is to be appreciated that arrangements in accordance with the disclosed concept may also be applied to other applications in which one or more journal bearings are employed and in which a failure of such bearing(s) could lead to catastrophic destruction of components of the particular application.
Although the disclosed concept has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the disclosed concept is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the disclosed concept contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.
In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” or “including” does not exclude the presence of elements or steps other than those listed in a claim. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination.
