Abstract:
A self-monitoring adjustment system is provided for evaluating and effecting adjustment of the leakage restricting mechanism between the rotating and non-rotating elements of a rotodynamic pump to restrict leakage and to establish desired gap dimensions between the rotating and non-rotating elements of the pump. The adjustment system is structured to be self-monitoring for determination of when an adjustment of the leakage restricting mechanism is warranted by the conditions of the pump, and is structured with adjusting mechanisms that are self-adjusting responsive to the monitored conditions of the pump, though manual adjustment is also enabled.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to rotodynamic pumps, and specifically relates to means for controlling and automating the adjustment devices for restricting fluid recirculation and reducing wear between rotating and non-rotating fluid processing elements of rotodynamic pumps, especially those pumps that are suitable for handling slurries and those pumps that are, or can be, configured with adjustable wear components designed as leakage restricting devices. 
         [0003]    2. Description of Related Art 
         [0004]    Rotodynamic pumps, such as centrifugal pumps, are commonly known and used for pumping fluids in many types of industries and for many applications. Such pumps generally comprise an impeller (rotating element) housed within a pump casing (non-rotating element) having a fluid inlet and fluid outlet, or discharge. The impeller is typically driven by a motor external to the casing. The impeller is positioned within the casing so that fluid entering the inlet of the casing is delivered to the center, or eye, of the impeller. Rotation of the impeller acts on the fluid primarily by the dynamic action of the impeller vanes which, combined with centrifugal force, move the fluid to the peripheral regions of the casing for discharge from the outlet. 
         [0005]    The dynamic action of the vanes, combined with centrifugal forces resulting from impeller rotation, produces pressure gradients within the pump. An area of lower pressure is created nearer the eye of the impeller and an area of higher pressure results at the outer diameter of the impeller and in the volute portion of the casing. An area of pressure change, from higher to lower pressure exists in the radially extending gap located between the rotating and non-rotating components. The pressure differential within the pump leads to fluid recirculation through the radial gap, between areas of high and low pressure. Such fluid recirculation, typically characterized as leakage, results in a consequential loss of pump performance and a dramatic increase in wear when there is a presence of solid particles in the fluid. 
         [0006]    Therefore, pumps are structured with various leakage restricting devices, both on the drive side of the impeller to prevent or restrict external leakage, and on the inlet or suction side of the impeller to prevent or restrict internal recirculating leakage. Pump leakage-restricting or sealing mechanisms have been developed where a side liner, or wear plate, is placed in axial juxtaposition to the impeller of the pump. The side liners, usually corresponding to a suction side and a drive side of the pump, are positioned to abut the pump casing and, in some configurations, may be bolted to the pump casing. In other configurations, the side liners are mounted near the pump casing so that the axial position of the side liners relative to the impeller is adjustable. 
         [0007]    The side liners may be metal, ceramic or elastomer material, or a combination of materials, and provide a simplified construction for repair or maintenance of the pump. Constructing the side liners with an elastomer seal to allow adjustability of a complete suction side or drive side has proven beneficial to extend the wear life of the liners. Additionally, a side liner provides a beneficial extension of the service life of the suction side seal face in heavy duty slurry applications versus adjusting only a seal wear ring. (Hill U.S. Pat. No. 5,941,536). 
         [0008]    Radially-extending gaps, or tapered gaps that are substantially radially-extending, between the rotating and non-rotating members are much less prone to entrapment of solids and are commonly employed in slurry pumps. Nevertheless, leakage restricting arrangements are widely used in the radial gap between the rotating and non-rotating elements, whether on the drive side or suction side, to further restrict leakage and solids entrapment. For example, US Published Application No. 2004/0136825 to Addie, et al. discloses a fixed projection on either the pump casing or on the impeller to provide a leakage restricting arrangement between the impeller and the pump casing. These restriction configurations may suffer from declining performance in service if an adjustment means is not present to compensate for wear. Seal rings, or wear rings, which generally extend between the rotating and non-rotating elements are also used as leakage restricting devices. 
         [0009]    Methods of adjusting seal rings and side liners are known and employed in rotodynamic pumps. For example, U.S. Pat. No. 4,527,948 to Addie, et al., describes a means of manually adjusting a seal to contact the impeller. U.S. Pat. No. 5,971,704 to Blattmann is similar to the &#39;948 patent in that it discloses the use of threaded pusher bolts to manually adjust a small seal ring toward the impeller to a set clearance. These sealing arrangements force a wear ring towards the surface of the impeller. Such adjustment systems rely on manual adjustments of the mechanism. Following the manual adjustment of the seal, a period of time exists where there is a forcible contact between the rotating and non-rotating elements, but as the elements wear, a clearance between the two components develops. Uncontrolled or unmonitored clearances between the components allow leakage, which accelerates wear. Additionally, the clearance between the rotating and non-rotating elements will become progressively larger until a further adjustment is made. 
         [0010]    U.S. Pat. No. 6,739,829 to Addie discloses an adjustable, floating ring element positioned between the impeller and the pump casing, which is also configured with means for receiving and distributing cooling and flushing fluid into the gap between the impeller and pump casing. The leakage restricting ring relies on water to flush the leakage restricting mechanism and provide the force to maintain its proximity to the impeller. The required flush system must be able to provide a consistent supply of clean liquid to the seal mechanism at a pressure which is not high enough to cause damage to the seal, but is sufficiently high enough to overcome internal pressures in the pump. The sufficiency of the pressure required in the flush system is dependent upon the application and the pump. 
         [0011]    U.S. Pat. No. 6,599,086 to Soja describes an adjustable wear plate for a rotodynamic pump. The disclosed wear plate also uses a manual adjustment mechanism to position a complete side liner. 
         [0012]    Prior adjustment mechanisms for sealing arrangements and side liners have heretofore been specifically directed to providing a manual means of adjustment. As a result, such arrangements may still be vulnerable to over adjustment and/or lack of sufficient adjustment, which may lead to undesirable fluid recirculation, or leakage, and wear between rotating and stationary elements of the pump. Moreover, flush water is not always available or practical for a given application. Further, the relative position of the sealing elements or leakage restricting mechanisms may not be accurately controlled by manual adjustment means due to variables of the application. 
         [0013]    Thus, it would be advantageous in the art to provide a means for effecting automatic adjustment of the leakage restricting mechanism associated with the radial gap between rotating and non-rotating elements of the pump to control leakage and wear, thereby improving the life of the elements and performance of the pump. It would also be advantageous to provide a monitoring mechanism whereby the adjustment can be made automatically responsive to a detected need to effect an adjustment to the preferred gap between the rotating and non-rotating elements. It would also be advantageous to provide in a rotodynamic pump a sensor device that indicates one or more conditions within the pump so that manual adjustment can be effected. 
       BRIEF SUMMARY OF THE INVENTION 
       [0014]    In accordance with the present invention, an automatic adjustment system is provided for effecting adjustment of the leakage restricting mechanism between the rotating and non-rotating elements of the pump to restrict leakage and to establish desired gap dimensions between the rotating and non-rotating elements of a pump. The automatic adjustment system is structured to be self-monitoring for determination of when an adjustment of the leakage restricting mechanism is warranted by the conditions of the pump, and is structured with adjusting mechanisms that may be self-adjusting responsive to the monitored conditions of the pump. The automatic adjustment system is described herein with respect to use in a centrifugal pump of the slurry type primarily to reduce wear, but may be adapted for use in any rotodynamic pump with a resulting increase in pump performance. 
         [0015]    In a further embodiment of the invention, a sensor or monitoring device is provided in, or in proximity to, the pump so that one or more conditions of the pump can be monitored by the device, and an indicator or other alerting device will advise of the condition so that a manual adjustment can be made of the adjusting mechanisms of the pump to provide a preferred gap between the rotating and non-rotating elements. While this embodiment does not provide automatic means for adjusting the non-rotating element, it is nonetheless within the purview of the invention to provide detection and or monitoring devices for allowing manual adjustment. 
         [0016]    As used herein, “rotating element” refers to the impeller or a similar structure, such as a rotor, that is driven and typically housed within a casing of the pump. As used herein, “non-rotating element” refers to any stationary structure or structures that are positioned adjacent the rotating element and which, in juxtaposition with the rotating element, produce a gap therebetween through which fluid recirculation, or leakage, typically occurs due to pressure differentials. The non-rotating element may, most typically, be a leakage restricting mechanism, a side liner or a portion of the pump casing. 
         [0017]    The automatic adjustment system of the present invention is generally comprised of at least one sensor or detection mechanism, at least one adjustment device and a control system in communication with both the sensor or detection mechanism and the adjustment device for effecting appropriate adjustment of the leakage restricting mechanism to provide more effective resistance to fluid recirculation and wear. 
         [0018]    The sensor or detection mechanism, of which there is at least one, is positioned in proximity to an element of the pump to monitor one or more conditions that would indicate a necessity for making an adjustment of the gap existing between the rotating and non-rotating elements. The sensor or detection device may be positioned within the pump or outside of the pump. 
         [0019]    The sensor or detecting mechanism may be any suitable device that is capable of determining the contact between the rotating and non-rotating elements and/or that is capable of determining one or more conditions that indicate the need to effect an adjustment of the gap between the rotating and non-rotating elements. Such conditions may include, but are not limited to, the measurable dimension of distance existing between the rotating and non-rotating elements, the existence of pressure or pressure differentials at or near the gap, the amount of force needed to rotate the rotating element, or the amount of force required to actuate the adjustment. 
         [0020]    Examples of sensor or detecting mechanisms (the terms being used interchangeably herein) are a proximity sensor to determine the dimensions of the gap between the rotating and non-rotating elements, a vibration sensor capable of detecting an amount of change in vibration levels which indicates contact between the rotating and non-rotating elements, a force sensor capable of determining that a certain change in the amount of force is required to make the adjustment between rotating and non-rotating elements and a torque sensor capable of detecting an amount of change in the torque of the rotating element which indicates a condition of contact between the rotating and non-rotating elements. Another suitable sensor or detecting mechanism would be one that detects an increase in the amps being drawn by the drive motor for the rotating element, which indicates contact between the rotating and non-rotating elements. 
         [0021]    The adjustment device of the invention, of which there is at least one and most typically a plurality of adjustment devices, is any structure that is capable of effecting a movement of the non-rotating element relative to the rotating element in a manner that adjusts the gap existing therebetween and through which fluid recirculation, or leakage, occurs. An exemplary type of adjustment device is one which comprises a member, such as a threaded rod, having a first end that is in contact with the movable non-rotating element and a second end which is structured with an actuation mechanism. Operation of the actuation mechanism causes the threaded rod to move against the non-rotating element to effect movement of the non-rotating element in the direction of the rotating element. Any type or configuration of an adjustment device can be employed in the invention which is capable of carrying out the required movement of the non-rotating element responsive to a signaled activation of the adjustment device. 
         [0022]    The actuation mechanism of the adjustment device may be any manner or type of device that causes movement of the adjustment device against the non-rotating element. For example, the actuation mechanism may be hydraulic, pneumatic or some other mechanical instrumentality. 
         [0023]    The actuation mechanism of the adjustment device is further structured to communicate with a control system that signals the actuation mechanism to operate responsive to detected conditions in or of the pump. In this regard, existing adjustment devices on existing pumps can be retrofitted with an actuation device, and sensor mechanisms can be positioned with respect to the pump, and to the control system, to equip existing pumps in the field with the automatic adjustment system of the present invention. 
         [0024]    The control system, as noted, is in communication with both the sensor device or devices and with the actuation mechanism of each adjustment device. The control system is of a type that can receive data from the detection or sensor device, process that data, and signal the actuation mechanism of each adjustment device to operate in response to the detection of a condition within the pump. Thus, the control system may have a central database for enabling these steps. 
         [0025]    Further, the database of the control system may be enabled with appropriate software and hardware for determining appropriate intervals at which adjustments should be made to provide predictive adjustments consistent with the conditions or operation of a given pump. The control system may even have storage capacity which enables the determination of actual or potential pre-operation conditions that enable an initial setting of the distance between the rotating and non-rotating elements. Such data would serve as a baseline from which the relative position of the rotating and non-rotating elements may be established, followed by appropriate adjustments determined by monitoring of the pump conditions by the sensor devices. 
         [0026]    The control system may also be programmed with optimum clearance or gap dimension data such that if contact is detected between the rotating and non-rotating elements, the actuation mechanism can be signaled to effect a reverse movement, or “backing off,” of the non-rotating element relative to the rotating element. 
         [0027]    The control system may also have the capacity to store previous adjustment data and time to determine a wear rate of the components. The calculated wear rate may then be used to determine a predicted wear rate and initiate an adjustment sequence to maintain a continuous or nearly continuous relative position between the rotating and non-rotating components without contact. Periodically, a contact sequence may be initiated which would allow for updating of the wear rate. Alternatively a signature from a position sensor or sensors may be determined which correlates to the relative position of the adjustable elements. This signature will then be used to determine and predict the above mentioned wear rate. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0028]    In the drawings, which currently illustrate the best mode for carrying out the invention: 
           [0029]      FIG. 1  is a side view in elevation of a centrifugal pump schematically showing the fundamental external components of the present invention; 
           [0030]      FIG. 2  is an isometric view of a centrifugal pump showing the inlet side of the pump and illustrating the placement of the actuating mechanism portion of a plurality of adjustment devices and various sensors; 
           [0031]      FIG. 3  is an enlarged view in cross section of the wet end of a slurry pump illustrating the internal elements of the present invention; 
           [0032]      FIG. 4  is a partial view in cross section of a pump showing the positioning of the vibration sensor; 
           [0033]      FIG. 5  is a partial view in cross section of a pump showing an alternative embodiment of the invention for use with an adjustable wear ring; 
           [0034]      FIG. 6  is a flow diagram schematically illustrating the sequence for actuation of the adjustment devices of the invention; and 
           [0035]      FIG. 7  is a flow diagram schematically illustrating the means for determining predictive adjustments in a pump. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    In the drawings, where the same or similar elements are indicated by the same reference numerals,  FIG. 1  illustrates an automatic adjustment system  10  encompassed by the present invention installed in a rotodynamic pump  12 . The rotodynamic pump  12  generally comprises a pump casing  14  having a fluid inlet  16  and a fluid outlet  18  for discharge. The pump  12  further includes a drive mechanism  20  for driving the rotating elements of the pump, and the drive mechanism  20  is positioned through a bearing assembly  22  to which the pump casing  14  is secured in known manner. 
         [0037]    The automatic adjustment system  10  of the present invention is generally comprised of at least one sensor or detection mechanism  30  (of which a plurality of various sensor or detection mechanisms are shown for illustrative purposes), at least one adjustment device  32  and a control system  34 . The present invention may preferably comprise a plurality of adjustment devices  32  which, as shown more clearly in  FIG. 2 , may, for example, be positioned to encircle the fluid inlet  16  of the pump  12 . Each of the adjustment devices  32  is illustrated as being wired to the control system  34 , as will be explained further below. 
         [0038]    Referring to  FIG. 3 , which illustrates the internal aspects of the pump  12 , it can be seen that in conventional manner, an impeller  36  is positioned within the pump casing  14  of the pump  12  and is connected to the drive mechanism  20  for rotation within the pump casing  14 . The impeller  36  may be of any type or construction, but is shown here as having at least one vane  38  positioned between a front shroud  40  and a back shroud  42 , corresponding to the suction side and drive side of the pump, respectively. The impeller  36  may, as here, have expelling vanes  44  positioned on the front shroud  40  and expelling vanes  46  positioned on the back shroud  42 . Expelling vanes may not always be present, and the type or configuration of the impeller may vary widely with the application and type of pump. 
         [0039]    The pump casing  14  of the pump  12  may vary widely in its structure and configuration. By way of example only, the illustrated pump  12  has a pump casing  14  that is comprised of a drive side casing  50  and separate front or suction side casing  52  which is secured to the drive side casing  50  by bolts  54 . The suction side casing  52  is configured with a separate suction cover  56  which is secured to the suction side casing  52  by bolts  58 . In the particular configuration shown, the pump casing  14  is further comprised of separate liner pieces, including a drive side casing liner  60  and a suction side casing liner  62  which are both designed as wear components. It is possible for the pump  12  to have a multiple piece drive side casing (e.g., a drive side cover (not shown) similar to the suction side casing  52  and cover  56 ). 
         [0040]    In the pump configuration shown, the drive side casing liner  60  is positioned within the drive side casing  50  and is bolted into place. The suction side casing liner  62  is positioned within the suction side casing  52  and is bolted into place. A separate, non-rotating suction side liner  64  is positioned within the suction side casing liner  62  and is located adjacent the suction side of the impeller  36 . Positioned adjacent the suction side liner  64  is a reinforcement plate  66 . By virtue of its formation, the suction side liner  64  and reinforcement plate  66  may be collectively referred to as a suction side liner assembly, as described more fully in U.S. Pat. No. 5,591,536, the disclosure of which is incorporated herein by reference. Similar to the suction side, the pump  12  may be configured with a drive side liner  68  positioned adjacent the drive side of the impeller  36 , and a reinforcement plate  70  may be positioned against the drive side liner  68  to form a drive side liner assembly. 
         [0041]    An exemplary structure and positioning of the adjustment devices of the present invention will be described herein with respect to the suction side of the pump  12 , which is inherently where the automatic adjustment system would be positioned. However, the automatic adjustment system of the invention may further comprise adjustment devices positioned on the drive side of the pump in connection with the drive side liner assembly in the same manner as described for the suction side of the pump. 
         [0042]    It can be seen from  FIG. 3  that the position of the suction side liner  64  adjacent the suction side of the impeller  36  forms a gap  72  through which fluid can recirculate, or leak, under various and previously described conditions. It is desirable to restrict such leakage by maintaining an appropriately close tolerance between the suction side liner  64  and the impeller  36 . Thus, the suction side assembly is configured to be axially moveable in a direction toward the impeller to maintain an appropriate axial dimension of the gap  72  to restrict leakage and wear. 
         [0043]    For that purpose, the present invention comprises adjustment devices  32  having one end  76  that is secured to the reinforcement plate  66  of the suction side liner assembly. The adjustment device  32  has a second end  78  which comprises an actuation mechanism  80 . 
         [0044]    The actuation mechanism  80  is, as shown in  FIGS. 1 ,  2  and  3 , in electrical communication with the control system  34  of the invention, such as by a wire  82  as shown here. The actuation mechanism  80  may be in wireless communication, however, with the control system  34 . The adjustment device  32 , as shown more clearly in  FIG. 3 , may comprise a rod  86  secured to the reinforcement plate  66 , the rod  86  being movable in response to the activation of the actuation mechanism  80 . The actuation mechanism  80  may be any suitable structure or device, such as a servo device, and may be electromechanically, hydraulically or pneumatically operated, or any combination of such means. That is, the powered actuation mechanism  80  may be any device which converts electrical or fluid power to a desired mechanical motion to effect movement of the adjustment device  32 . 
         [0045]    The actuation mechanism  80  of each adjustment device  32  is in communication with a central processing unit (CPU), shown schematically in  FIG. 1  at  90 , of the control system  34 , which is capable of sending a signal to the adjustment devices  32  responsive to received information from at least one sensor mechanism  30 . Thus, the CPU  90  is also in communication, wired or wireless, with the sensor mechanism  30  to collect data for processing. The control system  34  also includes data storage and processing capability, as suggested at  92  in  FIG. 1  for calculating and storing information concerning optimal gap dimensions, adjustment intervals and monitoring protocols for wear in the leakage restricting mechanism, e.g., the suction side liner  64 . 
         [0046]    In an alternative embodiment of the invention, the sensor mechanisms  30  are in communication with the control system  34 , such as the CPU  90 , either by wired or wireless means, and send data to the control system  34 . The control system  34  is structured with an alarm  88  or equivalent device that provides an indication of a condition of the pump which requires an adjustment to be made between the rotating and non-rotating elements of the pump. Responsive to the notice provided by the alarm  88 , manual adjustment can be effected as described. 
         [0047]    The sensor or detection mechanism  30  of the present invention may be any suitable device that can monitor and detect conditions in the pump, from which a determination can be made for activating adjustment of the suction side liner assembly, and/or signaling an adjustment sequence has eliminated the gap, either automatically or manually.  FIGS. 1 and 2  illustrate in a single figure a variety of such sensor mechanisms  30 . A first type of sensor mechanism  30  may be a linear displacement sensor  94  which is positioned through the pump casing and in proximity to the impeller  36  to detect linear, or axial, movement of the impeller  36  and suction side liner  64  relative to each other. The linear displacement sensor  94  can, therefore, detect whether the gap  72  between those elements is sufficiently large to warrant adjustment of the suction side liner  64 , or that the gap is eliminated thus concluding the adjustment. 
         [0048]    Another type of sensor mechanism  30  shown in  FIGS. 1 ,  2  and  4  is a vibration sensor  96  which detects vibration levels of the pump or a pump component. Contact between the impeller  36  and the suction side liner  64  changes these vibration levels, thereby enabling the determination of whether those two elements are contacting each other. Depending on the design of the leakage restricting device, this information may initiate an adjustment sequence or may indicate than an adjustment sequence initiated by another factor has eliminated the gap. It can be seen from  FIG. 4  that the vibration sensor  96  is positioned in close proximity to the reinforcement plate  66 . 
         [0049]    A third type of sensor mechanism  30  is shown in  FIG. 1  as a torque sensor  98 , which is positioned on the drive mechanism  20 . The torque sensor  98  is capable of determining a change in the torque required to rotate the impeller  36 , which in turn is indicative of whether contact is being made between the impeller  36  and the suction side liner  64  such that an adjustment is appropriate or that an adjustment sequence has eliminated the gap. Torque sensors  100  may also be positioned on or near the adjustment devices  32 , as schematically represented in  FIG. 1 . 
         [0050]    A fourth type of sensor mechanism  30  is schematically represented in  FIG. 1  as an amp meter  102  or detector associated with the drive motor  104  of the pump. Detection of an increase in the amps required in the motor  104  can indicate contact between the rotating and non-rotating elements of the pump. 
         [0051]    Any one or a combination of these, and any other suitable sensor mechanism or device, may be used to monitor and determine conditions of or within the pump that warrant adjustment of the non-rotating element (i.e., suction side liner) relative to the rotating element (i.e., the impeller) or indicate that an adjustment sequence has eliminated the gap. 
         [0052]    The sensor or detection mechanism of the present invention, when employed in a mode for providing automatic adjustment of the adjustment device  32 , is in electrical, mechanical or electromechanical communication with the control system  34 . This may be accomplished, for example, by providing a wire  106  between the sensor mechanism  30  (e.g., vibration sensor  96 ) and the control system  34 . 
         [0053]      FIG. 5  illustrates an alternative embodiment of the present invention where the non-rotating element is a leakage restricting ring or wear ring  108  that is positioned between a non-rotating, non-adjustable side liner  110  and the impeller  36  near the eye of the impeller  36 . An adjustment device  32  is position through the pump casing  54  and is in contact with the wear ring  108 . The actuation mechanism  80  of the adjustment device  32  is positioned externally to the pump  12  and is in communication with the control system (not shown). A sensor mechanism  30 , such as for example, a vibration sensor  96 , is shown in proximity to the adjustment device  32  and is positioned as previously described for detecting a condition, such as increased vibration of the rotating and/or non-rotating elements of the pump. Although a vibration sensor  96  is shown, any other sensor mechanism  30  may be employed as described previously, including a strain gauge. 
         [0054]      FIG. 6  comprises a schematic flow chart which describes generally how data collected from the sensor mechanisms and the adjustment devices can be processed and stored to provide automatic adjustment and monitoring in the system, as previously described.  FIG. 7  is a schematic flow chart of how predictive adjustments, such as may be based on calculated wear rates, may be determined to effect continuous or periodic self-adjustment of the adjustment devices. In the schematic flow charts of both  FIGS. 6 and 7 , the values X and Y denote selected time periods, where X may typically be greater than Y, and the values or time periods may be based on the particular application to which the pump is placed. 
         [0055]    The self-monitoring and adjustment system of the present invention may be installed in or adapted for use in any type of rotodynamic pump, and the system of the invention may be retrofit into existing pumps. Thus, the elements and configurations of the self-monitoring and adjustment system described herein may vary depending on the type of pump and the application. Hence, reference herein to specific details of the invention is by way of example only and is not intended to limit the scope of the invention in any manner.