Patent Publication Number: US-2013247687-A1

Title: System and method for setting roller skew

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This is a continuation of U.S. patent application Ser. No. 12/254,447, filed on Oct. 20, 2008, and entitled “SYSTEM AND METHOD FOR SETTING ROLLER SKEW”, the disclosure of which is incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The present disclosure relates to the operation of rotary bodies, such as rotary kilns. In particular, the present disclosure relates a system and method for identifying the neutral roller skew position, and for setting the skew for rollers used to support rotary bodies. 
     Cylindrical rotary bodies, such as rotary kilns, are used in carrying out a large number of economically important processes. Such bodies typically includes a cylindrical shell portion that is supported by annular tyres spaced along the length of the tube. Each tyre is carried on a pair of opposed rollers, which in turn may be mounted upon a concrete pier or pad. The shell portion is rotated about its longitudinal axis, and is supported for such rotation by contact of the rollers with the tyres surrounding the shell portion. The rollers are correspondingly supported upon the piers or pads with the use of bearing assemblies. 
     Over extended periods of operation, the rollers may fall out of alignment, thereby causing their rotational axes to move out of parallel with respect to each other and not parallel or otherwise in optimum position with respect to the rotational axis of the shell. This is typically referred to as roller skew. The cost of replacing the tyres and/or rollers is relatively high. Thus, an important consideration in the operation of such rotary equipment is the maintenance of proper alignment between the surface of a roller and the supporting tyre to prevent uneven wearing of the respective surfaces and overloading the bearing assemblies. If the two are kept in proper alignment, a long life can be expected from the tyre and the rollers and the bearing assemblies. 
     Alignment relationships are complicated by the fact that such rotary equipment is typically constructed with the shell portion on a slight slope relative to horizontal to facilitate the flow of material therethrough. Thus, the shell exerts an axial force due to gravity, thereby causing an axial thrust load to exist on the rollers and their associated bearing assemblies whenever they are required to counteract gravity to keep the shell running on the rollers. In order to maintain proper alignment between the shell portion and the rollers, it has previously been necessary to periodically check the alignment by visual inspection or by sophisticated alignment measurements, to determine roller axial position as best possible. However, such measurements typically do not provide sufficient accuracies, must be made relatively often, are difficult to evaluate, very subjective, and in many instances are not dependably carried out by the operator. 
     SUMMARY 
     An aspect of the present disclosure is directed to a method for reducing roller skew for a plurality of rollers configured to support a rotary body. The method includes rotating the rotary body in a first rotational direction, and ascertaining a first thrust load property applied to a first roller of the plurality of rollers from the rotary body while the rotary body rotates in the first rotational direction. The method also includes rotating the rotary body in a second rotational direction that is opposite of the first rotational direction, and ascertaining a second thrust load property applied to the first roller from the rotary body while the rotary body rotates in the second rotational direction. The method further includes adjusting an orientation of a bearing assembly for the first roller to reduce a difference between the first thrust load property and the second thrust load property. 
     Another aspect of the disclosure is directed to a method for reducing roller skew for a plurality of rollers configured to support a rotary body, where the method includes ascertaining a first thrust load property applied to a first roller of the plurality of rollers from the rotary body while the rotary body rotates in a first rotational direction. The method also includes ascertaining a second thrust load property applied to the first roller from the rotary body while the rotary body rotates in a second rotational direction that is opposite of the first rotational direction. The method further includes determining a difference between the first thrust load property and the second thrust load property, and comparing the determined difference to a threshold. 
     A further aspect of the disclosure is directed to a method for reducing roller skew for a plurality of rollers configured to support a rotary body, where the method includes rotating the rotary body in a first rotational direction, and ascertaining first thrust load properties applied to the plurality of rollers from the rotary body while the rotary body rotates in the first rotational direction. The method also includes rotating the rotary body in a second rotational direction that is opposite of the first rotational direction, and ascertaining second thrust load properties applied to the plurality of rollers from the rotary body while the rotary body rotates in the second rotational direction. The method further includes adjusting orientations of bearing assemblies for the plurality of rollers to reduce differences between the first thrust load properties and the second thrust load properties. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side schematic illustration of a monitoring system of the present disclosure in use with a rotary kiln. 
         FIG. 2  is a partial front perspective view of a roller mechanism of the kiln in use with a rotary drum of the rotary kiln. 
         FIG. 3  is an expanded side perspective view of the roller mechanism in use with the rotary drum, where the rotary drum is rotating in a first rotational direction. 
         FIG. 4  is an expanded side perspective view of the roller mechanism in use with the rotary drum, where the rotary drum is rotating in a second rotational direction that is opposite of the first rotational direction. 
         FIG. 5  is a flow diagram of a method for reducing roller skew for a roller configured to support a rotary body. 
         FIGS. 6A-6C  are graphical illustrations of tilt angles versus time, which illustrate the application of the method for reducing roller skew. 
         FIG. 7  is a side schematic illustration of an alternative monitoring system of the present disclosure in use with a rotary kiln, where the alternative monitoring system is configured to adjust orientations of bearing assemblies in an automated manner. 
         FIG. 8  is a side schematic illustration of a second alternative monitoring system of the present disclosure in use with a rotary kiln having one or more thrust roller mechanisms 
     
    
    
     While the above-identified figures set forth one or more embodiments of the present invention, other embodiments are also contemplated, as noted in the disclosure. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention. 
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  illustrate monitoring system  10  in use with kiln  12 , where monitoring system  10  is configured to monitor thrust load properties of kiln  12  for identifying roller skew. As shown in  FIG. 1 , monitoring system  10  includes computer system  14  and communication lines  16 , where computer system  14  monitors thrust load properties detected by a plurality of sensors (not shown in  FIG. 1 ) secured to kiln  12 , via communication lines  16 . Communication lines  16  are physical and/or wireless signal lines that interconnect computer system  14  and the plurality of sensors. For example, communication lines  16  may include physical signal lines that interconnect computer system  14  and the plurality of sensors. Alternatively, communication lines  16  may be wireless transmitters and receivers between computer system  14  and each of the plurality of sensors. 
     Kiln  12  includes rotary drum  18 , piers  20 , roller mechanisms  22 , and drive mechanism  24 . Rotary drum  18  is a rotary body that includes shell  26  and tyres  28 , where shell  26  is a cylindrical shell that extends along longitudinal axis  30 . Tyres  28  are rings extending around shell  26  to provide bearing surfaces  32  that are substantially coaxial to longitudinal axis  30 . Piers  20  are a plurality of successive foundations, which allow rotary drum  18  to be mounted at an angle from horizontal. This allows material that is fed into the uphill end of shell  26  to flow downhill under the force of gravity while shell  26  rotates. In alternative embodiments, piers  20  may provide different angled orientations for shell  26 , including a horizontal orientation. Roller mechanisms  22  are roller/bearing assembly mechanisms that are supported by piers  20 , and engage bearing surfaces  32  of tyres  28 , thereby rotatably supporting rotary drum  18 . Examples of suitable arrangements for kiln  12  are disclosed in Gebhart, U.S. Patent Application Publication No. 2007/0266798. Furthermore, one or more of tyres  28  may engage with thrust rollers (not shown) bearing against the downstream or upstream sides of tyres  28 . The thrust rollers are beneficial for preventing rotary drum  18  from slipping off of roller mechanisms  22  during operation. 
     In the embodiment shown in  FIG. 1 , drive mechanism  24  includes gear train  34  and motor  36 , where gear train  34  includes one or more gear and shaft assemblies that interconnect motor  36  with one or more roller mechanisms  22 . This allows rotary drum  18  to rotate under power applied from motor  36 . Motor  36  may be secured to a mounting structure (not shown), and may include a variety of different motors, such as variable-frequency electric motors, hydraulic motors, electric motors containing reversing switches, motors containing reversible leads, and combinations thereof. In an alternative embodiment, girth gear  38  may extend around shell  26  and engage with gear train  34 , thereby allowing motor  34  to rotate rotary drum  18  without directly engaging a roller mechanism  22 . In an additional alternative embodiment, a girth gear may be absent and rotary drum  18  may be driven through the supporting rollers by way of the rollers themselves having motors mounted to their shafts. 
     In either embodiment, the motor used to rotate rotary drum  18  (e.g., motor  36 ) is desirably configured to rotate rotary drum  18  in opposing rotational directions (i.e., clockwise and counter-clockwise directions about longitudinal axis  30 ). This allows monitoring system  10  to monitor kiln  12  while rotary drum  18  rotates in each of the opposing rotational directions. As discussed below, monitoring system  10  is suitable for monitoring ascertainable properties relating to thrust loads (referred to as “thrust load properties”) that rotary drum  18  applies to roller mechanisms  22  during operation. For example, the thrust load properties that monitoring system  10  monitors may include the amount that each bearing assembly of roller mechanism  22  “tilts” due to the applied thrust loads. The orientations of the bearing assemblies may be adjusted based on the thrust load properties that are ascertained while rotating rotary drum  18  in each rotational direction. This reduces or substantially eliminates roller skew, which increases operational efficiencies and preserves the operational life of kiln  12 . Furthermore, rotary drum  18  may be operated without the use of oil, which is otherwise typically disposed between bearing surfaces  32  and roller mechanisms  22 . This creates an observable trait, where the bearing surfaces become smooth and polished to provide aesthetically pleasant, shiny bearing surfaces. 
     The following discussion of the operation of monitoring system  10  and kiln  12  focuses on the embodiment in which monitoring system  10  monitors the amount that each bearing assembly of roller mechanism  22  tilts due to the applied thrust loads. However, monitoring system  10  is also suitable for monitoring a variety of different thrust load properties in a similar manner. For example, monitoring system  10  may include strain gauges configured to monitor the flexing of one or more components of roller mechanism  22  (e.g., rollers and/or bearing assemblies) due to the applied thrust loads from rotary drum  18 . In another alternative embodiment, monitoring system  10  may include accelerometers configured to monitor the movement of one or more stationary components of roller mechanism  22  due to the applied thrust loads from rotary drum  18 . Furthermore, a combination of different thrust load properties (e.g., tilt, flexing, and movement) may be monitored and ascertained. 
     As shown in  FIG. 2 , each roller mechanism  22  includes rollers  40  and  42 , which respectively include bearing surfaces  44  and  46 . Bearing surfaces  44  and  46  are the surfaces that engage with bearing surface  32  of tyre  28  for supporting rotary drum  18 . Roller mechanism  22  also includes shaft extension  48  and bearing assemblies  50   a  and  50   b,  where shaft extension  48  axially connects roller  40  to bearing assemblies  50   a  and  50   b.  Bearing assemblies  50   a  and  50   b  are upstream and downstream bearing assemblies for roller  40 , respectively, where “upstream” and “downstream” orientations are relative to the direction of material flow through rotary drum  18 . Similarly, roller mechanism  22  includes shaft extension  52  and bearing assemblies  54   a  and  54   b,  where shaft extension  52  axially connects roller  42  to bearing assemblies  54   a  and  54   b,  and where bearing assemblies  54   a  and  54   b  are respectively upstream and downstream bearing assemblies for roller  42 . Bearing assemblies  50   a,    50   b,    54   a,  and  54   b  may constitute a variety of different bearing assemblies, such as sleeve bearings, antifriction bearings, journal bearings, spherical roller bearings, and combinations thereof. 
     Bearing assemblies  50   a,    50   b,    54   a,  and  54   b  are secured to base  55 , which is correspondingly secured to pier  20 . While bearing assemblies  50   a,    50   b,    54   a,  and  54   b  are fixed to base  55 , they are capable of skew adjustments by means of adjusting screws, such as adjusting screw  56   a  for bearing assembly  50   a,  adjusting screw  56   b  for bearing assembly  50   b,  adjusting screw  57   a  for bearing assembly  54   a,  and adjusting screw  57   b  (not shown) for bearing assembly  54   b.  The adjusting screws allow for skew adjustments of the axis of each of rollers  40  and  42  with respect to the axis of tyre  28  (i.e., longitudinal axis  30 ), which correspondingly allows a user to manually reduce the roller skew for rollers  40  and  42 . 
     As further shown, sensors  58   a  and  60   a  are respectively secured to bearing assemblies  50   a  and  54   a.  Corresponding sensor  58   b  (shown in  FIG. 3 ) and sensor  60   b  (shown with hidden lines) are respectively secured to bearing assemblies  50   b  and  54   b.  In the embodiment shown, sensors  58   a,    58   b,    60   a,  and  60   b  are tilt meters configured to detect the amount that bearing assemblies  50   a,    50   b,    54   a,  and  54   b  tilt due to the thrust loads that are applied from rotary drum  18 . Sensors  58   a,    58   b,    60   a,  and  60   b  are also configured to transmit signals relating to the detected tilt amounts to computer system  14  via communication lines  16 , as discussed above. Suitable tilt meters for use with monitoring system  10  include those capable of measure tilts over range of about −40 arc-minutes to about +40 arc-minutes, with tilt-detection sensitivities as small as about one arc-second (about 0.0028 degrees). Examples of suitable tilt meters include electrolytic tilt sensors and inclinometers commercially available from Spectron Glass and Electronics Incorporated, Hauppauge, N.Y.. 
     As discussed above, in alternative embodiments, sensors  58   a,    58   b,    60   a,  and  60   b  may be configured to detect different “thrust load properties” (e.g., flexing and movement). In these embodiments sensors  58   a,    58   b,    60   a,  and  60   b  are also configured to transmit signals relating to the detected thrust load properties to computer system  14  via communication lines  16 , as discussed above. In alternative embodiments, as discussed below, the sensors (e.g., sensors  58   a,    58   b,    60   a,  and  60   b ) may be secured to one or more thrust rollers (not shown) for detecting the magnitude of pressures applied to the one or more thrust rollers. 
       FIGS. 3 and 4  illustrate the thrust loads applied to bearing assemblies  50   a,    50   b ,  54   a,  and  54   b  while rotary drum  18  rotates in the opposing rotational directions. As discussed above, monitoring system  10  is suitable for monitoring the amount that bearing assemblies  50   a ,  50   b,    54   a,  and  54   b  tilt due to the thrust loads applied from rotary drum  18  while rotating in opposing rotational directions. The orientations of bearing assemblies  50   a,    50   b,    54   a,  and  54   b  may then be adjusted with the use of adjustment screws  56   a,    56   b,    57   a,  and  57   b  to reduce or substantially eliminate roller skew by aligning the rotational axes of rollers  40  and  42  parallel to the rotational axis of rotary drum  18  (i.e., longitudinal axis  30 ) (i.e., optimize roller skew). 
     When the axes of rollers  40  and  42  are not parallel to the axis of rotary drum  18 , thrust loads are induced on one or more of bearing assemblies  50   a,    50   b,    54   a,  and  54   b.  The induced thrust load(s) can lead to severe surface wear of the faces in rolling contact and can create enough axial force to cause bearing failure. Knowing the presence of thrust load is an important part of setting bearing assemblies  50   a,    50   b,    54   a,  and  54   b  for proper alignment, and also for preventing bearing failure over the long term. 
     As shown in  FIG. 3 , rotary drum  18  is rotated (via motor  36 ) in a first rotational direction (represented by arrows  62 ). Any skew between the axes of rollers  40  and  42  and rotary rum  18  creates thrust loads on one or more of bearing assemblies  50   a,    50   b,    54   a,  and  54   b,  which in turn causes the respective bearing assemblies for the given rollers to tilt. For example, as shown in  FIG. 3 , the rotation of rotary drum  18  in the first rotational direction applies thrust loads in a first axial direction (represented by arrow  64 ) on bearing assemblies  50   a,    50   b,    54   a,  and  54   b.  The applied thrust loads in the first axial direction cause bearing assemblies  50   a,    50   b,    54   a , and  54   b  to tilt in a first tilt direction (represented by arrow  66 ). The magnitude of the tilt in the first tilt direction may be a function of a variety of parameters, such as style of bearings, stiffness of the bearing housings, stability of base  55 , stability of priers  20 , stability of the ground conditions, speed of rotation, and the weight of rotary drum  18 . As discussed above, the induced thrust loads can lead to severe surface wear of the faces in rolling contact and can create enough axial force to cause bearing failure. 
     Sensors  58   a,    58   b,    60   a,  and  60   b  respectively detect the amounts that bearing assemblies  50   a,    50   b,    54   a,  and  54   b  tilt due to the thrust loads applied in the first axial direction along arrow  64 . The detected signals relating to the tilt amounts are then transmitted to computer system  14  via communication lines  16 , which allows computer system  14  to continuously monitor and log the thrust loads applied to bearing assemblies  50   a,    50   b,    54   a,  and  54   b  while rotary drum  18  rotates in the first rotational direction. After a suitable duration of monitoring to ascertain the tilt amounts for one or more bearing assemblies of rotary kiln  12  (e.g., bearing assemblies  50   a,    50   b,    54   a,  and  54   b ), motor  36  may reverse the rotation of rotary drum  18  to allow monitoring system  10  to ascertain the tilt amounts while rotary drum  18  rotates in the opposing rotational direction. 
     As shown in  FIG. 4 , motor  36  rotates rotary drum  18  in a second rotational direction (represented by arrows  68 ), which is the opposing rotational direction to the first rotational direction discussed above. The skew between the axes of rollers  40  and  42  and rotary drum  18  create thrust loads on bearing assemblies  50   a,    50   b,    54   a,  and  54   b  in a second axial direction (represented by arrow  70 ), which is substantially opposite of the first axial direction. The applied thrust load in the second axial direction causes bearing assemblies  50   a,    50   b,    54   a , and  54   b  to tilt in a second tilt direction (represented by arrow  72 ). The magnitude of the tilt in the second tilt direction may also be a function of a variety of parameters, such as those discussed above for the first tilt direction. 
     Sensors  58   a,    58   b,    60   a,  and  60   b  respectively detect the amounts that assemblies  50   a,    50   b,    54   a,  and  54   b  tilt due to the thrust loads applied in the second axial direction along arrow  70 . The detected tilt amounts are then transmitted to computer system  14  via communication lines  16 , thereby allowing computer system  14  to continuously monitor and log the thrust loads applied to bearing assemblies  50   a,    50   b,    54   a,  and  54   b  while rotary drum  18  rotates in the second rotational direction. Based on the monitored tilt amounts, the alignments of one or more of the bearing assemblies of kiln  12  (e.g., bearing assemblies  50   a,    50   b,    54   a,  and  54   b ) may then be adjusted (represented by arrows  73  in  FIG. 4 ) to reduce or substantially eliminate roller skew for each roller of roller mechanisms  22  (e.g., rollers  40  and  42 ) (i.e., optimize roller skew). 
       FIG. 5  is a flow diagram of method  74 , which is an exemplary method for reducing roller skew for a roller configured to support a rotary body (e.g., rollers  40  and  42  of kiln  12 ). As shown, method  74  includes steps  76 - 94 , and initially involves mounting sensors to one or more components that are subjected to the thrust loads applied by the rotation of the rotary body (step  76 ). For example, sensors  58   a,    58   b,    60   a,  and  60   b  may be secured to one or more locations of bearing assemblies  50   a,    50   b,    54   a,  and  54   b,  thereby allowing sensors  58   a,    58   b ,  60   a,  and  60   b  to monitor the amount that each of bearing assemblies  50   a,    50   b,    54   a,  and  54   b  tilt due to the applied thrust loads from rotary drum  18 . 
     For systems that do not incorporate motors that allow the rotary body to rotate in opposing rotational directions, the motor for the rotary body may be configured to rotate the rotary body in the opposing rotations (step  78 ). For example, the leads on an electrical motor of the rotary body (e.g., motor  36 ) may be inverted to allow the opposing rotation. Alternatively, auxiliary drive motors may be engaged with the rotary body to provide for the opposing rotations. For example, a variable-frequency drive or a hydraulic motor may be connected to the rotary body. 
     The rotary body may then be rotated in a first rotational direction (step  80 ), and a monitoring system may ascertain first thrust load properties based on the thrust loads that the rotary body applies to one or more of the bearing assemblies in a first axial direction (step  82 ). For example, rotary drum  18  may be rotated in the direction of arrows  62 , which applies thrust loads on bearing assemblies  50   a,    50   b,    54   a,  and  54   b  in the direction of arrow  64 . Correspondingly, monitoring system  10  may monitor and log the tilt amounts for one or more of bearing assemblies  50   a,    50   b,    54   a,  and  54   b  due to the applied thrust loads. The rotary body is desirably allowed to rotate for a suitable duration (e.g.,  5 - 10  minutes) to allow rolling surfaces to settle in and thrust force to accumulate wherein the bearing and base assembly act much like a spring slowly storing more and more energy before monitoring the desired thrust load properties. In one embodiment, the thrust load properties that are ascertained are averages of multiple measurements (e.g., over 30-second intervals). This embodiment is beneficial to compensate for tyre wobble, which may otherwise interfere with the data analysis. 
     When a sufficient amount of data of the thrust load properties are ascertained, the rotation of the rotary body is reversed such that the rotary body rotates in a second rotational direction that is opposite of the first rotational direction (step  84 ). The rotary body is desirably allowed to rotate for a suitable duration (e.g., 5-10 minutes) to allow rolling surfaces to settle in and associated energy accumulation, and a monitoring system may ascertain second thrust load properties based on the thrust loads that the rotary body applies to one or more of the bearing assemblies in a second axial direction (step  86 ). For example, rotary drum  18  may be rotated in the direction of arrows  68 , thereby applying thrust loads on bearing assemblies  50   a,    50   b,    54   a , and  54   b  in the direction of arrow  70 . Correspondingly, monitoring system  10  may monitor and log the tilt amounts for one or more of bearing assemblies  50   a,    50   b,    54   a,  and  54   b  due to the applied thrust loads and energy stored. 
     Because the second rotational direction is opposite of the first rotational direction, the amplitudes of the ascertained first and second thrust load properties are typically opposite because they are in substantially opposing directions (e.g., the directions of arrows  66  and  72 ). The difference between the amplitudes is then determined (step  88 ), which may be performed manually or in an automated manner with a computer system (e.g., computer system  14 ). Because the amplitudes of the thrust load properties are being compared, the rotation of the rotary body in steps  80  and  84  of method  74  are desirably performed at substantially the same rotational rates to obtain amplitudes that may be evenly compared. 
     The amplitude difference may then be compared to a predetermined threshold to determine whether the thrust load properties in the opposing rotational directions remain substantially unchanged (step  90 ). The threshold that the amplitude difference is compared to may vary depending on the operating conditions and the properties of the thrust loads being monitored. In embodiments in which the tilt of the bearing assemblies are being monitored, suitable thresholds for the amplitude difference include tilt differences of about 0.010 degrees or less, with particularly suitable thresholds including tilt differences of about 0.005 degrees or less. If the roller for the rotary body is oriented in a substantially neutral skew position, where the rotational axis of the roller is substantially parallel to the axis of the tyres and the rotary body, then the amplitude difference between the first and second thrust load properties will be substantially zero. Thus, the amplitude difference will be less than the threshold, and the roller does not require any adjustment (step  94 ). 
     If, pursuant to step  90  of method  74 , the amplitude difference is not less than the threshold, the orientations of one or more of the bearing assemblies may be adjusted to reduce the amplitude difference (step  92 ). For examples, one or more of bearing assemblies  50   a,    50   b ,  54   a,  and  54   b  may be adjusted with the use of adjustment screws  56   a,    56   b,    57   a,  and  57   b  along arrows  73 . One or more of steps  80 - 92  may then be repeated as necessary until the amplitude difference between the first thrust load properties and the second thrust load properties are less than the threshold, pursuant to step  90 . Once the amplitude difference is less than the threshold, the roller is oriented in a substantially neutral skew position, and does not require any further adjustment, as discussed above (step  94 ). Method  74  may then be repeated for each roller mechanism  22  of kiln  12  until each roller is oriented in a substantially neutral skew position such that the rotational axis of each roller is substantially parallel to the rotational axis of the tyres (e.g., along longitudinal axis  30 ). 
       FIGS. 6A-6C  are simplified graphical illustrations of tilt versus time for bearing assembly  50   a,  which illustrate the use of method  74  to reduce roller skew. The plots of the graphical illustrations in  FIGS. 6A-6C  may be displayed on a viewing screen of computer system  14  based on signals received from sensor  58   a  via communication lines  16 . As such, computer system  14  may also display similar plots for each sensor secured to a bearing assembly along kiln  12  (e.g., sensors  58   a,    58   b,    60   a,  and  60   b  for each roller mechanism  22 ). 
     Accordingly, pursuant to steps  80  and  82  of method  74 , rotary drum  18  is initially rotated in the first rotational direction, and sensor  58   a  detects tilt values of about −0.1 degrees, where the negative value of the detected tilt represents the direction of the thrust load applied to bearing assembly  50   a.  In this example, the first rotational direction causes a thrust load to be applied to bearing assembly  50   a  in the direction of arrow  64  (shown in  FIG. 3 ), and the detected tilt of −0.1 degrees is represented by arrow  66  (shown in  FIG. 3 ). These initial tilt values are then plotted on computer system  14  for a sufficient duration to allow rolling surfaces to settle in and associated energy accumulation to ensure that the tilt values remain substantially consistent over time. 
     At transition point  100 , pursuant to steps  84  and  86  of method  74 , the rotational direction of rotary drum  18  is reversed to the second rotational direction, and sensor  58   a  detects tilt values of about +0.1 degrees, where the positive value of the detected tilt also represents the direction of the thrust load applied to bearing assembly  50   a.  In this example, the second rotational direction causes a thrust load to be applied to bearing assembly  50   a  in the direction of arrow  70  (shown in  FIG. 4 ), and the detected tilt of +0.1 degrees is represented by arrow  72  (shown in  FIG. 4 ). These tilt values are then plotted on computer system  14  for a sufficient duration to allow rolling surfaces to settle in and associated energy to accumulate, to ensure that the tilt values remain substantially consistent over time. 
     Pursuant to step  88  of method  74 , the amplitude difference of the tilt values is then determined (e.g., computed or otherwise calculated). The amplitude difference is desirably based on average tilt values while the given tilt values remain consistent over time. As shown in  FIG. 6A , the amplitude difference (referred to as amplitude difference  102 ) is about 0.2 degrees. Pursuant to step  90  of method  74 , amplitude difference  102  is then compared to a threshold, which, in this example is assumed to be 0.01 degrees. Thus, because amplitude difference  102  is greater than the threshold, the orientation of bearing assembly  50   a  may be adjusted with the use of adjustment screw  56   a,  pursuant to step  92  of method  74 . 
     As shown in  FIG. 6B , the adjustment to the orientation of bearing assembly  50   a  reduces the skew of roller  40 . Accordingly, pursuant to steps  80 - 86  of method  74 , when monitoring the tilt values of bearing assembly  50   a  while rotating rotary drum  14  in each of the opposing directions, the amplitudes of the tilt values are reduced. This is due the greater alignment between the rotational axis of roller  40  and the rotational axis of rotary drum  18  (i.e., longitudinal axis  30 ). Accordingly, the amplitude difference of the resulting tilt values (referred to as amplitude difference  104 ), which is determined pursuant to step  88  of method  74 , is also reduced to 0.1 degrees. Pursuant to step  90  of method  74 , amplitude difference  104  is then compared to the threshold of 0.01 degrees. Because amplitude difference  102  is greater than the threshold, the orientation of bearing assembly  50   a  may be further adjusted with the use of adjustment screw  56   a,  pursuant to step  92  of method  74 . 
     As shown in  FIG. 6C , the adjustment to the orientation of bearing assembly  50   a  further reduces the skew of roller  40 . Accordingly, pursuant to steps  80 - 86  of method  74 , when monitoring the tilt values of bearing assembly  50   a  while rotating rotary drum  14  in each of the opposing directions, the amplitudes of the tilt values are further reduced such that the amplitude difference (referred to as amplitude difference  106 ) is less than 0.01 degrees. Thus, pursuant to step  90  of method  74 , because amplitude threshold  106  is less than the threshold, bearing assembly  50   a  is properly aligned to substantially eliminate the skew of roller  40 . Method  74  may then be performed for each bearing assembly of kiln  12  until each bearing assembly is properly oriented. 
     The example shown in  FIGS. 6A-6C  illustrate a simplified example for reducing roller skew by monitoring and adjusting the orientation for a single bearing assembly. In additional embodiments, multiple operations of method  74  may be performed in parallel to adjust multiple bearing assemblies for a single roller, for multiple rollers of a single roller mechanism, and/or for multiple roller mechanisms. Furthermore, the orientations of one or more bearing assemblies may be readjusted to compensate for adjustments made for other bearing assemblies. 
     The comparison of the relative amplitudes of the first and second thrust load properties allows the skew of the rollers (e.g., rollers  40  and  42 ) to be reduced or substantially eliminated without requiring a zero-based calibration. For example, previous thrust load measurement techniques require a zero-thrust load baseline, where the rotary body is required to be lifted off of the rollers. This requires substantial effort and time, particularly for large rotary kilns, which can weight several hundred tons. In comparison, method  74  compares relative amplitudes while rotating the rotary body in opposing rotational directions. In fact, in some situations, the location at which the amplitude difference falls below the threshold may not be at a zero-degree tilt depending on the orientations of the bearing assemblies. However, even in these situations, the rollers may attain substantially neutral skew positions relative to the rotational axis of the rotary body. When the roller skew is substantially eliminated, the alignment of the rollers may be maintained for substantial durations (e.g., longer than several months or years) without requiring realignment. This increases operational efficiencies and extends the operational lives of the rollers and bearing assemblies. 
     Although the discussion herein and illustrations depict a rotary kiln (i.e., kiln  12 ), the present disclosure is also applicable to any rotary body supported on trunnion rollers. Such rotary bodies may include, for example, rotary kilns, rotary coolers, rotary dryers, rotary furnaces, rotating reactors, rotary filters, bean conditioners, rotary ash cylinders, mill shell bearing surfaces, delacquerers, washers, debarking drums, pelletizers, coal breakers, granulators, incinerators, shakeout drums, and combinations thereof. The method can also be applied to any machine rigidly mounted on a foundation consisting of a bearing supported rotating shaft where an axial shaft load needs to be monitored. 
       FIG. 7  illustrates monitoring system  110  in use with kiln  112 , where monitoring system  110  is an alternative to monitoring system  10  (shown in  FIGS. 1-4 ) for monitoring thrust load properties of kiln  112 , and for reducing roller skew in an automated manner. Monitoring system  110  and kiln  112  operate in a similar manner to monitoring system  10  and kiln  12 , where the respective reference labels are increased by “ 100 ”. Thus, computer system  114  monitors thrust load properties that rotary drum  118  applies to roller mechanisms  122  via communication lines  116 . Furthermore, monitoring system  110  also includes communication line  208 , which is a physical and/or wireless signal line that interconnects computer system  114  and motor  136 . This allows computer system  114  to control the rotation of rotary drum  118  in an automated manner. In one embodiment, communication line  116  (or an additional communication line) may also interconnect computer system  114  with control mechanisms (not shown) that are configured to perform an automated function. For example, the control mechanisms may be configured to actuate the adjustment screws (e.g., adjustment screws  156   a,    156   b,    157   a,  and  157   b ). This allows computer system  114  to also adjust the orientations of one or more of bearing assemblies  150   a,    150   b,    154   a,  and  154   b  in an automated manner. Alternatively, the control mechanisms may be configured to initiate an application of a lubricant onto the bearing surfaces for roller mechanisms  122 . This embodiment is beneficial for reducing or eliminating the thrust loads, which provides personnel a suitable time period to respond to the situation, and is particularly beneficial while operating kiln  112  during off-hours (e.g., nights and weekends) when emergency personnel may not be immediately available. 
     Accordingly, computer system  114  may ascertain the thrust load properties applied to the components of roller mechanisms  122  (e.g., bearing assemblies  150   a,    150   b,    154   a , and  154   b ) to monitor roller skew in real time. Thus, computer system  114  may perform method  74  in an automated manner to continuously maintain proper roller alignments relative to the rotational axis of rotary drum  118 . This further increases operational efficiencies, and further extends the operational lives of the rollers and bearing assemblies. 
       FIG. 8  illustrates monitoring system  210  in use with kiln  212 , where monitoring system  210  is an alternative to monitoring system  10  (shown in  FIGS. 1-4 ) and monitoring system  110  (shown in  FIG. 7 ) for monitoring thrust load properties of kiln  212  with thrust rollers. Monitoring system  210  and kiln  212  operate in a similar manner to monitoring system  10  and kiln  12 , where the respective reference labels are increased by “ 200 ”. In the embodiment shown in  FIG. 8 , kiln  212  includes thrust roller mechanism  296  that engage with tyre  228 . In alternative embodiments, kiln  212  may include a plurality of thrust roller mechanisms  296  for engagement with multiple tyres  228 . As shown, thrust roller mechanism  296  includes a pair of thrust rollers bearing against the downstream or upstream sides of tyre  28 . The thrust rollers are beneficial for preventing rotary drum  18  from slipping off of roller mechanisms  22  during operation. 
     In this embodiment, the sensors (e.g., corresponding to sensors  58   a,    58   b,    60   a,  and  60   b ) may be secured to one or more thrust roller mechanisms  296  for detecting the thrust load properties (e.g., the magnitude of pressures) applied to the one or more thrust rollers. Thus, computer system  214  may monitor the thrust load properties that rotary drum  218  applies to the one or more thrust roller mechanisms  296  via communication lines  216  in the same manner as discussed above for monitoring systems  10  and  110 . 
     Although the present system and method for reducing roller skew has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of this disclosure.