Patent Publication Number: US-2021189810-A1

Title: Spinner wear detection

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority under 35 U.S.C. § 119(e) to U.S. Patent Application No. 62/951,948 entitled “SPINNER WEAR DETECTION,” by Christopher MAGNUSON, filed Dec. 20, 2019, which application is assigned to the current assignee hereof and incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates, in general, to the field of drilling and processing of wells. In particular, present embodiments relate to a system and method for operating robotic systems during subterranean operations. More particularly, present embodiments relate to detecting the wear of spinners in an iron roughneck during subterranean operations. 
     BACKGROUND 
     When a rig is tripping a tubular string into a wellbore, an iron roughneck can be used to connect tubulars at their threaded ends and wrench the connection to a desired torque to maintain the connection. The connection may require rotating one tubular relative to the other tubular to thread the ends together (e.g. pin end being threaded into a box end). This “spinning” can be performed by a spinner assembly of the iron roughneck. When the ends have been threaded together (i.e. tubulars connected), wrench assemblies of the iron roughneck can be used to clamp the tubulars and torque the tubulars relative to each other to obtain the desired torque for the tubular connection. 
     When a rig is tripping a tubular string out of a wellbore, an iron roughneck can be used to disconnect tubulars at their threaded ends by applying a desired torque and “breaking” (or releasing) a connection between the tubulars with one of the tubulars being spun out of (e.g. unthreaded from) the other tubular. Spinning the tubular out of the other tubular may require rotating one tubular relative to the other tubular to unthread the ends (e.g. pin end being unthreaded from a box end). Again, this “spinning” can be performed by a spinner assembly of the iron roughneck. When the ends have been unthreaded (i.e. tubulars disconnected), a pipe handler can move the tubular, which is released from the tubular string to a storage location on or off the rig. 
     In both the tripping in or tripping out, the iron roughneck can engage and rotate tubulars to thread or unthread the tubulars. As mentioned above, some iron roughnecks can use the spinner assembly to engage a tubular body of one of the tubulars being connected or disconnected and rotate the tubular at a faster speed than the wrench assemblies. The wrench assemblies (or clamping mechanisms) are included in a wrench assembly and are used to torque and untorque tubular connections. The spinner assembly can have a plurality of spinners, each of which can be cylindrically shaped with a gripping surface on its outer perimeter. The iron roughneck can move the spinners into and out of engagement with the tubular, with engagement of the tubular being provided by an outer gripping surface of each spinner that can grip the body of the tubular and transmit rotational motion of the spinner to the tubular body, thereby spinning the tubular. Over time, these gripping surfaces can become worn thereby causing the spinning assembly to slip on the tubular body and reduce the amount of rotational force that is applied to the tubular body. Continued use of the spinners can degrade the performance of the gripping surfaces to a point that the spinner assembly may fail to perform the task of connecting or disconnecting tubulars. 
     Therefore, spinners can be seen as consumables that are replaced periodically to maintain the performance of the spinner assembly. However, replacement of the spinners is generally performed periodically as described in a maintenance plan. The period of time between replacement of the spinners can usually be set to ensure that the spinners are replaced well before the time they are actually beginning to show symptoms of wear. Therefore, the spinners can be replaced before they have outlived their usefulness, thus increasing costs due to increased replacement cycles and increased down time. 
     Therefore, improvements of robotic rig systems are continually needed, and particularly improvements for spinner assemblies of iron roughnecks used in support of subterranean operations. 
     SUMMARY 
     In accordance with an aspect of the disclosure, a system that can include a spinner assembly comprising an encoder, and a spinner subassembly, the spinner subassembly comprising, a spinner configured to engage a tubular, and a drive gear coupled to the spinner, with the drive gear configured to drive rotation of the spinner, and the encoder configured to count teeth of the drive gear as the drive gear rotates. 
     In accordance with another aspect of the disclosure, a system that can include a spinner subassembly comprising, a plurality of spinners configured to engage and rotate a tubular, a drive gear that is coupled to the plurality of spinners, with the drive gear configured to rotate the plurality of spinners, a proximity sensor configured to detect teeth of the drive gear as the teeth pass through a sensing field of the proximity sensor, and a controller configured to receive first sensor data from the proximity sensor, wherein the first sensor data is representative of an actual number of revolutions of the plurality of spinners when the plurality of spinners engages the tubular. 
     In accordance with another aspect of the disclosure, a method that can include operations for engaging a tubular with a spinner, rotating a drive gear, with the drive gear coupled to the spinner, rotating the spinner in response to rotating the drive gear, rotating the tubular in response to rotating the spinner, and counting, via an encoder, teeth of the drive gear as the teeth pass through a sensing field of a proximity sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of present embodiments will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1A  is a representative simplified front view of a rig being utilized for a subterranean operation, in accordance with certain embodiments; 
         FIG. 1B  is a representative perspective view of an iron roughneck with a spinner assembly on a rig floor, in accordance with certain embodiments; 
         FIG. 1C  is a representative front view of an iron roughneck engaging a tubular string, in accordance with certain embodiments; 
         FIG. 2A  is a representative perspective view of an iron roughneck with a wrench assembly portion removed for clarity, in accordance with certain embodiments; 
         FIG. 2B  is a representative front view of an iron roughneck with a wrench assembly portion removed for clarity, in accordance with certain embodiments; 
         FIG. 3  is a representative partial cross-sectional view of the roughneck along line  3 - 3  as indicated in  FIG. 2B , in accordance with certain embodiments; 
         FIGS. 4A and 4B  are representative partial cross-sectional views of the spinner assembly along line  3 - 3  as indicated in  FIG. 2B , in accordance with certain embodiments; 
         FIG. 5A  is a representative partial cross-sectional view of a joint in a tubular string prior to a connection being made, in accordance with certain embodiments; 
         FIG. 5B  is a representative detailed partial cross-sectional view of an area  5 B in  FIG. 5A , in accordance with certain embodiments; 
         FIGS. 6A and 6B  are a representative table including specifications for example tubulars, in accordance with certain embodiments; 
         FIG. 7  is a representative table including maximum revolution calculations for spinning a tubular in a joint connection of a tubular string, in accordance with certain embodiments; 
         FIG. 8  is a representative top view of gear with a proximity sensor arranged to count gear teeth, in accordance with certain embodiments; 
         FIGS. 9-12  are representative plots of outputs from proximity sensors that are arranged as in  FIG. 8 , in accordance with certain embodiments; 
         FIG. 13  is a representative top view of gear with a proximity sensor arranged to count gear teeth, in accordance with certain embodiments; 
         FIG. 14  is a representative plot of outputs from a pair of proximity sensors that are arranged as in  FIG. 13 , in accordance with certain embodiments; 
         FIG. 15A  is a representative front view of an iron roughneck, in accordance with certain embodiments; and 
         FIG. 15B  is a representative hydraulic control circuit diagram for vertically adjusting of the spinner assembly, according to certain embodiments; and 
         FIG. 16  is a representative partial cross-sectional view of an actuator with an LVDT sensor, in accordance with certain embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Present embodiments provide a robotic system with electrical components that can operate in hazardous zones (such as a rig floor) during subterranean operations. The robotic system can include a robot and a sealed housing that moves with the robot, with electrical equipment and/or components contained within the sealed housing. The aspects of various embodiments are described in more detail below. 
     As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
     The use of “a” or “an” is employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural, or vice versa, unless it is clear that it is meant otherwise. 
     The use of the word “about”, “approximately”, or “substantially” is intended to mean that a value of a parameter is close to a stated value or position. However, minor differences may prevent the values or positions from being exactly as stated. Thus, differences of up to ten percent (10%) for the value are reasonable differences from the ideal goal of exactly as described. A significant difference can be when the difference is greater than ten percent (10%). 
       FIG. 1A  is a representative simplified front view of a rig  10  being utilized for a subterranean operation (e.g. tripping in or out a tubular string to or from a wellbore), in accordance with certain embodiments. The rig  10  can include a platform  12  with a rig floor  16  and a derrick  14  extending up from the rig floor  16 . The derrick  14  can provide support for hoisting the top drive  18  as needed to manipulate tubulars. A catwalk  20  and V-door ramp  22  can be used to transfer horizontally stored tubular segments  50  to the rig floor  16 . A tubular segment  52  can be one of the horizontally stored tubular segments  50  that is being transferred to the rig floor  16  via the catwalk  20 . A pipe handler  30  with articulating arms  32 ,  34  can be used to grab the tubular segment  52  from the catwalk  20  and transfer the tubular segment  52  to the top drive  18 , the fingerboard  40 , the wellbore  15 , etc. However, it is not required that a pipe handler  30  be used on the rig  10 . The top drive  18  can transfer tubulars directly to and directly from the catwalk  20  (e.g. using an elevator coupled to the top drive). As used herein, “tubular” refers to an elongated cylindrical tube and can include any of the tubulars manipulated around the rig  10 , such as tubular segments  50 ,  52 , tubular stands, tubulars  54 , and tubular string  58 , but not limited to the tubulars shown in  FIG. 1A . Therefore, in this disclosure, “tubular” is synonymous with “tubular segment,” “tubular stand,” and “tubular string,” as well as “pipe,” “pipe segment,” “pipe stand,” “pipe string,” “casing,” “casing segment,” or “casing string.” 
     The tubular string  58  can extend into the wellbore  15 , with the wellbore  15  extending through the surface  6  into the subterranean formation  8 . When tripping the tubular string  58  into the wellbore  15 , tubulars  54  are sequentially added to the tubular string  58  to extend the length of the tubular string  58  into the earthen formation  8 .  FIG. 1A  shows a land-based rig. However, it should be understood that the principles of this disclosure are equally applicable to off-shore rigs where “off-shore” refers to a rig with water between the rig floor and the earth surface  6 . 
     When tripping the tubular string  58  out of the wellbore  15 , tubulars  54  are sequentially removed from the tubular string  58  to reduce the length of the tubular string  58  in the wellbore  15 . The pipe handler  30  can be used to remove the tubulars  54  from an iron roughneck  38  or a top drive  18  at a well center  24  (see  FIG. 1B ) and transfer the tubulars  54  to the catwalk  20 , the fingerboard  36 , etc. The iron roughneck  38  can break a threaded connection between a tubular  54  being removed and the tubular string  58 . A spinner assembly  40  can engage a body of the tubular  54  to spin a pin end  57  of the tubular  54  out of a threaded box end  55  of the tubular string  58 , thereby unthreading the tubular  54  from the tubular string  58 . 
     When tripping the tubular string  58  into the wellbore  15 , tubulars  54  are sequentially added to the tubular string  58  to increase the length of the tubular string  58  in the wellbore  15 . The pipe handler  30  can be used to deliver the tubulars  54  to a well center on the rig floor  16  in a vertical orientation and hand the tubulars  54  off to an iron roughneck  38  or a top drive  18 . The iron roughneck  38  can make a threaded connection between the tubular  54  being added and the tubular string  58 . A spinner assembly  40  can engage a body of the tubular  54  to spin a pin end  57  of the tubular  54  into a threaded box end  55  of the tubular string  58 , thereby threading the tubular  54  into the tubular string  58 . The wrench assembly  42  can provide a desired torque to the threaded connection, thereby completing the connection. 
     A rig controller  250  can be used to control the rig  10  operations including controlling various rig equipment, such as the pipe handler  30 , the top drive  18 , the iron roughneck  38 , the fingerboard equipment, imaging systems, various other robots on the rig  10  (e.g. a drill floor robot). The rig controller  250  can control the rig equipment autonomously (e.g. without periodic operator interaction), semi-autonomously (e.g. with limited operator interaction such as initiating a subterranean operation, adjusting parameters during the operation, etc.), or manually (e.g. with the operator interactively controlling the rig equipment via remote control interfaces to perform the subterranean operation). 
     The rig controller  250  can include one or more processors with one or more of the processors distributed about the rig  10 , such as in an operator&#39;s control hut, in the pipe handler  30 , in the iron roughneck  38  (e.g. controller  130 , see  FIG. 1B ), in the fingerboard  36 , in the imaging systems, in various other robots, in the top drive  18 , at various locations on the rig floor  16  or the derrick  14  or the platform  12 , at a remote location off of the rig  10 , at downhole locations, etc. It should be understood that any of these processors can perform control or calculations locally or can communicate to a remotely located processor for performing the control or calculations. These processors can be coupled via a wired or wireless network. 
       FIG. 1B  is a representative perspective view of an iron roughneck  38  with a spinner assembly  40  on a rig floor  16  with a body of the tubular  54  engaged with the spinner assembly  40  and the wrench assembly  42  gripping both the box end  55  of the tubular string  58  and the pin end  57  of the tubular  54 . The iron roughneck  38  can include a robot arm  44  that supports the iron roughneck  38  from the rig floor  16 . The robotic arm  44  can include a support arm  45  that can couple to a frame  48  via a frame arm  46 . The support arm  45  can support and lift the frame  48  of the iron roughneck  38  via the frame arm  46 , which can be rotationally coupled to the support arm  45  via the pivots  47 . The frame  48  can provide structural support for the spinner assembly  40  and the wrench assembly  42 . The robotic arm  44  can move the frame  48  from a retracted position (i.e. away from the well center  24 ) to an extended position (i.e. toward the well center  24 ) and back again as needed to provide support for making or breaking connections in the tubular string  58 . In the extended position of the frame  48 , the spinner assembly  40  and the wrench assembly  42  can engage the tubular  54  and the tubular string  58 . 
     The top drive  18  (not shown) can rotate the tubular string  58  in either clockwise or counter-clockwise directions as shown by arrows  94 . The tubular string  58  is generally rotated in a direction that is opposite the direction used to unthread tubular string  58  connections. When a connection is to be made or broken, a first wrench assembly  41  of the wrench assembly  42  can grip the box end  55  of the tubular string  58 . The first wrench assembly  41  can prevent further rotation of the tubular string  58  by preventing rotation of the box end  55  of the tubular string  58 . 
     If a connection is being made, the spinner assembly  40  can engage the tubular  54  at a body portion, which is the portion of the tubular between the pin end  57  and box end  55  of the tubular  54 . With the pin end  57  of the tubular  54  engaged with the box end  55  of the tubular string  58 , the spinner assembly  40  can rotate the tubular  54  in a direction (arrows  91 ) to thread the pin end  57  of the tubular  54  into the box end  55  of the tubular string  58 , thereby forming a connection of the tubular  54  to the tubular string  58 . When a pre-determined torque of the connection is reached by the spinner assembly  40  rotating the tubular  54  (arrows  91 ), then a second wrench assembly  43  of the wrench assembly  42  can grip the pin end  57  of the tubular  54  and rotate the pin end  57 . By rotating the second wrench assembly  43  relative to the first wrench assembly  41  (arrows  92 ), the wrench assembly  42  can torque the connection to a desired torque, thereby completing the connection of the tubular  54  to the tubular string  58 . The iron roughneck can then be retracted from the well center  24  and the subterranean operation can continue. 
     If a connection is being broken, the spinner assembly  40  can engage the tubular  54  at the body portion. The first wrench assembly  41  can grip the box end  55  of the tubular string  58  and the second wrench assembly  43  can grip the pin end  57  of the tubular  54 . By rotating the pin end  57  of the tubular  54  relative to the box end  55  of the tubular string  58 , the previously torqued connection can be broken loose. After the connection is broken, the spinner assembly  40  can rotate the tubular  54  relative to the tubular string  58  (arrows  91 ), thereby releasing the tubular  54  from the tubular string  58 . The tubular  54  can then be removed from the well center by the top drive  18  or pipe handler  30  (or other means) and the iron roughneck  38  can be retracted from the well center  24  to allow the top drive  18  access to the top end of the tubular string  58  for hoisting another length of the tubular string  58  from the wellbore  15  to remove another tubular  54 . 
     The position of the spinner assembly  40  and wrench assembly  42  relative to the rig floor  16  (and thus the tubular string  58 ) can be controlled by the controller  250  via the robotic arm  44  and the frame arm  46 , which is moveable relative to the frame  48 . The controller  250  or other controllers, via the robotic arm  44 , can manipulate the frame  48  by lifting, lowering, extending, retracting, rotating the arm, etc. The robotic arm  44  can be coupled to the frame  48  via the support arm  45  which can be rotatably coupled to the frame arm  46  via pivots  47 . The frame  48  can move up and down relative to the frame arm  46  to raise and lower the spinner assembly  40  and wrench assembly  42  as needed to position the assemblies  40 ,  42  relative to the tubular string  58 . The frame  48  can also tilt (arrows  100 ) via pivots  47  to longitudinally align a center axis  102  (see  FIG. 2B ) of the assemblies  40 ,  42  relative to the tubular string  58 . 
       FIG. 1C  is a representative front view of an iron roughneck  38  engaging a tubular string  58 . As described above regarding  FIG. 1B , the spinner assembly  40  and the wrench assembly  42  can be structurally supported by the frame  48 . The wrench assembly  42  can include a first wrench assembly  41  (or backup wrench assembly) that can grip an end of the tubular string  58  (e.g. the box end  55 ), thereby preventing rotation of the tubular string  58  (arrows  94 ). The second wrench assembly  43  (or torque wrench assembly) can grip an end of the tubular  54  (e.g. the pin end  57 ) and torque the connection (arrows  92 ) relative to the tubular string  58  as needed to make or break the connection. However, it should be understood that both wrench assemblies  41 ,  43  can rotate to make or break the connection. 
     The spinner assembly  40  can include spinner subassemblies  110 ,  120  that can cooperate with each other to engage and rotate the tubular  54 . The spinner assembly  40  can include a coupling assembly  60  that couples the spinner subassemblies  110 ,  120  together and couples the spinner subassemblies  110 ,  120  to the frame  48 . The coupling assembly  60  can operate to move the spinner subassemblies  110 ,  120  toward or away (arrows  66 ,  68 ) from each other to engage or disengage the spinner subassemblies  110 ,  120  with the tubular  54 . 
       FIG. 2A  is a representative perspective view of an iron roughneck  38  with the wrench assembly  42  portion removed for clarity. The iron roughneck  38  can include the frame  48  that supports the spinner assembly  40  and the wrench assembly  42  (not shown). A base  49  of the frame  48  can be used to support the wrench assembly  42 . 
     The coupling assembly  60  can include guide tubes  76 ,  78 . Bracket assembly  112  can mount the spinner subassembly  110  to the guide tubes  76 ,  78  via a pair of sleeves  72 ,  73 . The sleeve  72  can be coaxially mounted over one end of the guide tube  76 , and the sleeve  73  can be coaxially mounted over one end of the guide tube  78 . Bracket assembly  122  can mount the spinner subassembly  120  to the guide tubes  76 ,  78  via a pair of sleeves  74 ,  75  (sleeve  75  not shown, see  FIG. 3 ). The sleeve  74  can be coaxially mounted over another end of the guide tube  76 , and the sleeve  75  can be coaxially mounted over another end of the guide tube  78 . The sleeves  72 ,  74  and sleeves  73 ,  75  are configured to slide along the respective guide tubes  76 ,  78 . An actuator  70  is configured to cause the bracket assemblies  112 ,  122  to move toward or away from each other. 
     The bracket assembly  112  can be fixedly attached to the spinner subassembly  110 , such that the spinner subassembly  110  moves with the sleeves  72 ,  73  when the sleeves  72 ,  73  are slide along the respective guide tubes  76 ,  78 . The bracket assembly  122  can be fixedly attached to the spinner subassembly  120 , such that the spinner subassembly  120  moves with the sleeves  74 ,  75  when the sleeves  74 ,  75  are slide along the respective guide tubes  76 ,  78 . Therefore, when the sleeves  72 ,  73  are moved toward the sleeves  74 ,  75  along the respective guide tubes  76 ,  78 , then the spinner subassemblies  110 ,  120  are moved toward each other. When the sleeves  72 ,  73  are moved away from the sleeves  74 ,  75  along the respective guide tubes  76 ,  78 , then the spinner subassemblies  110 ,  120  are moved away from each other. The movements of the spinner subassemblies  110 ,  120  are parallel to the movements of the sleeves  72 ,  73 ,  74 ,  75 , and offset from the movements of the sleeves  72 ,  73 ,  74 ,  75 . Therefore, the travel directions for the subassemblies  110 ,  120 , and the travel directions for the sleeves  72 ,  73 ,  74 ,  75  are parallel to each other but spaced away from each other. In other words, movements of the sleeves  72 ,  73 ,  74 ,  75  are not in line with movements of the subassemblies  110 ,  120 . 
     Each spinner subassembly  110 ,  120  can include a motor  114 ,  124 , respectively, and multiple spinners  140 . The motor  114 ,  124  can rotate respective spinners  140 , and when the spinner subassemblies  110 ,  120  are engaged with the tubular  54 , rotation of the spinners  140  can cause the tubular  54  to rotate. 
       FIG. 2B  is a representative front view of an iron roughneck  38  with a wrench assembly portion  42  removed for clarity. The spinner subassemblies  110 ,  120  are positioned on opposite sides of a center axis  102  of the spinner assembly  40 , with the center axis  102  being positioned between the spinner subassemblies  110 ,  120 . 
       FIGS. 3, 4A, 4B  are representative partial cross-sectional views of the roughneck  36  along line  3 - 3  as indicated in  FIG. 2B .  FIG. 3  shows a representative partial cross-sectional view of the iron roughneck  38  that reveals the gears  150 ,  152 ,  154 ,  156  of the spinner subassembly  110  and the gears  160 ,  162 ,  164 ,  166  of the spinner subassembly  120 .  FIG. 3  also shows an actuator  70  coupled to the spinner subassemblies  110 ,  120  via the linkage assembly  60 . The actuator  70  can cause the spinner subassemblies  110 ,  120  to move toward or away from each other.  FIGS. 4A, 4B  are more detailed partial cross-sectional views of the spinner subassemblies  110 ,  120  with the proximity sensors  200 ,  202  positioned to detect teeth passing through the sensing fields  208 ,  209 , respectively. The actuator  70  can include a Linear Variable Differential Transformer (LVDT) sensor. The LVDT sensor can detect and report the position of the piston rod of the actuator  70  relative to the body of the actuator  70 . This can provide real-time horizontal position measurements of the spinner subassemblies  110 ,  120  and can be used to determine the real-time horizontal position of the spinners  140  and determine the diameter D2 of the tubular  54 . The LVDT sensor will be described in more detail below. 
     Referring again to  FIGS. 3, 4A, 4B , regarding the spinner subassembly  110 , the motor  114  can drive the drive gear  150 . The drive gear  150  can be coupled to an intermediate gear  152  that transfers the rotational motion of the drive gear  150  (arrows  170 ) to the gears  154 ,  156  that rotate (arrows  174 ) the spinner drive shafts for the respective spinners  142 ,  144 . The intermediate gear  152  can rotate (arrows  172 ) in an opposite direction than the gear  150  (arrows  170 ) and the gears  154 ,  156  (arrows  174 ). 
     Regarding the spinner subassembly  120 , the motor  124  can drive the drive gear  160 . The drive gear  160  is coupled to an intermediate gear  162  that transfers the rotational motion of the drive gear  160  (arrows  180 ) to the gears  164 ,  166  that rotate (arrows  184 ) the spinner drive shafts for the respective spinners  146 ,  148 . The intermediate gear  162  can rotate (arrows  182 ) in an opposite direction than the gear  160  (arrows  180 ) and the gears  164 ,  166  (arrows  184 ). 
     The following discussion regarding  FIGS. 3, 4A, 4B  refers to the spinner subassembly  110  and an associated encoder, with proximity sensor  200 , sensing field  208 , encoder card  204 , cable  134 , gears  150 ,  152 ,  154 ,  156 , and spinners  142 ,  144 . Even though the following discussion refers to the spinner subassembly  110  and its associated encoder, it is equally applicable to the spinner subassembly  120  and its associated encoder, with proximity sensor  202 , sensing field  209 , encoder card  206 , cable  136 , gears  160 ,  162 ,  164 ,  166 , and spinners  146 ,  148 . It should be understood that the spinner assembly  40  includes the encoders for both spinner subassemblies  110 , and  120 . Therefore, the encoder cards  204 ,  206  are included in the spinner assembly, even if the encoder cards are disposed remotely from the spinner subassemblies  110 ,  120  (e.g. in a J-box that houses the controller  130  for the iron roughneck, or in any other location on the rig, such as locations of any of the processors of the rig controller  250 , or separate from controller locations on the rig  10 ). Therefore, references to the encoder includes the associated proximity sensor and encoder card. 
     The proximity sensor  200  (e.g. an intrinsically safe inductive proximity sensor with an NPN sensing output or a PNP sensing output) can be positioned proximate to the drive gear  150  such that the proximity sensor  200  can detect when a tooth  62  of the gear  150  passes through a sensing field  208 . When the tooth  62  is present in the sensing field  208 , the proximity sensor  200  can switch to an output level (such as a higher voltage) that indicates the presence of the tooth  62 . When the tooth  62  is not present in the sensing field  208  (i.e. a valley  64  between teeth  62  of the gear  150  is in position of the sensing field  208 ), the proximity sensor  200  can switch to an output level (such as a lower voltage) that indicates that a tooth  62  is not present. 
     As the gear  150  rotates and causes alternating teeth  62  and valleys to pass through the sensing field  208  of the proximity sensor  200 , the output of the proximity sensor  200  can become a pulse train with higher level outputs followed by lower level outputs. Therefore, a pulse train output from the proximity sensor  200  indicates that the gear  150  is rotating. Analysis of the pulse train can determine a speed of rotation of the gear  150 . It should be understood that the presence of a tooth  62  in the sensing field  208  can also be represented by a lower level output with the absence of a tooth  62  (or the valley) present in the sensing field  208  being represented by a high level output. The proximity sensor  200  merely needs to cause its output to change from one level to the other level, so an encoder card  204  can interpret a proximity sensor output to count teeth as the teeth  62  of the gear  150  pass through the sensing field  208  of the proximity sensor  200 . It should be understood that it is also envisioned that the waveform from the proximity sensor  200  can be analyzed to determine a duration of the tooth  62  being present or absent in the sensing field  208 , in addition to a count of the number of teeth  62  that pass through the sensing field  208 . 
     The encoder card  204  along with the proximity sensor  200  can provide the encoder function that monitors (e.g. counts) teeth  62  as a gear in the spinner subassembly  110  rotates. The encoder function can include an intrinsically safe inductive proximity sensor  200  and an encoder card  204 . As can be seen, an encoder according to the principles of this disclosure, provides benefits for subterranean operations by directly detecting spinner wear in the spinner assembly  40  without positioning spark prone electronics in the spinner assembly  40 . If the encoder function were implemented by a conventional encoder, not only would spark prone electronics be positioned in close proximity to the gears in the spinner subassembly  110 , but the space required in the spinner subassembly  110  to accommodate the spark prone electronics would be undesirable due to the amount of space needed to isolate the spark prone electronics and maintain an Explosive (EX) Zone 1 certification of the iron roughneck  38 . 
     Standards have been developed to guide the design of equipment to be used in these hazardous areas. Two standards (ATEX and IECEx) are generally synonymous with each other and provide guidelines (or directives) for equipment design. ATEX is an abbreviation for “Atmosphere Explosible”. IECEx stands for the certification by the International Electrotechnical Commission for Explosive Atmospheres. Each standard identifies groupings of multiple EX zones to indicate various levels of hazardous conditions in a target area. 
     One grouping is for areas with hazardous gas, vapor, and/or mist concentrations. 
     EX Zone 0—A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor, or mist is present continuously or for long periods or frequently 
     EX Zone 1—A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor, or mist is likely to occur in normal operation occasionally. 
     EX Zone 2—A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor, or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only. 
     Another grouping is for areas with hazardous powder and/or dust concentrations. 
     EX Zone 20—A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, or for long periods or frequently. 
     EX Zone 21—A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally. 
     EX Zone 22—A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only. 
     The Zone normally associated with the oil and gas industry is the EX Zone 1. Therefore, the explosive atmosphere directives or guidelines for robotic systems used in subterranean operations are for an EX Zone 1 environment. Explosive atmosphere directives or guidelines for other EX Zones can be used also (e.g. EX Zone 21). However, the EX Zone 1 and possibly EX Zone 21 seem to be the most applicable for the oil and gas industry. ATEX is the name commonly given to two European Directives for controlling explosive atmospheres: 1) Directive 99/92/EC (also known as ‘ATEX 137’ or the ‘ATEX Workplace Directive’) on minimum requirements for improving the health and safety protection of workers potentially at risk from explosive atmospheres. 2) Directive 94/9/EC (also known as ‘ATEX 95’ or ‘the ATEX Equipment Directive’) on the approximation of the laws of Member States concerning equipment and protective systems intended for use in potentially explosive atmospheres. 
     Therefore, as used herein “ATEX certified” indicates that the article (such as an elevator or pipe handling robot) meets the requirements of the two stated directives ATEX 137 and ATEX 95 for EX Zone 1 environments. IECEx is a voluntary system which provides an internationally accepted means of proving compliance with IEC standards. IEC standards are used in many national approval schemes and as such, IECEx certification can be used to support national compliance, negating the need in most cases for additional testing. Therefore, as used herein, “IECEx certified” indicates that the article (such as an elevator or pipe handling robotic system) meets the requirements defined in the IEC standards for EX Zone 1 environments. As used herein, “EX Zone 1 certified” or “EX Zone 1 certification” refers to ATEX certification, IECEx certification, Canada and USA, or other countries for EX Zone 1 environments. 
     The novel arrangement of the encoder function of this disclosure minimizes space requirements in the spinner subassembly  110  and eliminates a need for additional structure to maintain an EX Zone 1 certification since the proximity sensor  200  can be intrinsically safe. Even if the wiring to the proximity sensor  200  is cut during operations, the wire will cause no spark. 
     The encoder card  204  can be disposed in a J-box on the iron roughneck  38  that houses the controller  130  with the J-box mounted remotely from the spinner subassembly  110 . The J-box can be integral to the iron roughneck  38  and moveable with the iron roughneck  38 . The J-box can be located in an EX Zone 2 certified area. The encoder card  204  can be coupled to the proximity sensor  200  via the cable  134  which transmits an output of the proximity sensor  200  to the encoder card  204 . The encoder card  204  can process the sensor data from the proximity sensor  200  to determine the number of teeth of a gear that passed by the sensing field  208  of the proximity sensor  200  and send the results to the controller  130 . The encoder card  204  can also produce a pulse train from the sensor data, the pulse train being representative of the number of teeth  62  passing the proximity sensor  200  and a speed of the teeth  62  as they pass the proximity sensor  200 . 
     It should be understood that each of the gears  150 ,  152 ,  154 ,  156  in the spinner subassembly  110  can have a different number of teeth in keeping with the principles of this disclosure. However, in this example, the gears  150 ,  152 ,  154 ,  156  of the spinner subassembly  110  each have 16 teeth. Therefore, if the drive gear  150  rotates (arrows  170 ) a single revolution (i.e. 360 degrees), then each of the other gears  152 ,  154 ,  156  will also rotate (arrows  172 ,  174 ) a single revolution, and thus the spinners  142 ,  144  will rotate (arrows  174 ) a single revolution. If the drive gear is rotated multiple revolutions, or even a fraction of a revolution, or combinations thereof, the spinners  142 ,  144  will be rotated the same amount. When the spinners  142 ,  144  are used to rotate (arrows  91 ) a tubular  54 , the number of revolutions of the tubular  54  can be calculated from knowing the number of revolutions of the spinners  142 ,  144 , an outer diameter D1 of the spinners  142 ,  144 , and an outer diameter D2 of the tubular  54 . When the number of revolutions of the spinners  142 ,  144  is R 142  and the number of revolutions of the tubular  54  is represented by R 54 , then the Equation (1) below can be used to determine R 54 , from the diameters D1, D2, and R 142 : 
         R   54   =D 1/ D 2* R   142   (1)
 
     When the spinners  142 ,  144  rotate (arrows  174 ), the amount of rotation imparted to the tubular  54  (assuming no slippage) is a ratio of the circumference  190  of the spinners  142 ,  144  to the circumference  192  of the tubular  54 . For example, if the circumference  192  is twice as long as the circumference  190 , then if the spinners  142 ,  144  rotate two revolutions, the tubular  54  would rotate one revolution. The circumference  192  of the tubular  54  equals [π*D2] and the circumference  190  of the spinners  142 ,  144  equals [π*D1]. The ratio RT1 of the circumference  190  to the circumference  192  equals [π*D1/π*D2] which equals [D1/D2]. If the revolutions of the spinners  142 ,  144  are known, then the revolutions of the tubular  54  can be calculated by the equation (1) above which can otherwise be stated as Equation (2) below: 
         R   54   =RT 1* R   142   (2)
 
     Conversely, if it is desirable to rotate the tubular  54  a known number of revolutions R 54 , then the number of revolutions R 142  of the spinners  142 ,  144  that are required to produce the desired tubular revolutions R 54  is given as: 
         R   142   =D 2/ D 1* R   54   (3)
 
       or 
         R   142   =RT 2* R   54   (4)
 
     where RT2 is the ratio of the outer diameter D2 to the outer diameter D1. 
     The spinner subassemblies  110 ,  120  can be moved toward or away from each other in the directions indicated by arrows  66 ,  68 . When the subassemblies are moved toward each other the spinners  142 ,  144 ,  146 ,  148  can engage the tubular  54  and induce rotation of the tubular  54  by rotating the drive gears  150 ,  160 , which rotates the spinners  142 ,  144 ,  146 ,  148 , respectively. 
     As stated above, it is not a requirement that the gears in the spinner subassemblies  110 ,  120  have the same number of teeth thereby producing a 1:1 gear ratio. The gears in the spinner subassemblies  110 ,  120  can be configured to produce various gear ratios other than 1:1. Sometimes it is desirable to increase or decrease the torque applied by the spinner subassemblies  110 ,  120  to the tubular  54 , or increase or decrease the rotational speed imparted to the tubular  54  by the spinner subassemblies  110 ,  120 . Generally, the torque applied to the tubular  54  by the spinner subassemblies  110 ,  120  is inversely proportional to the rotational speed imparted to the tubular  54 . Therefore, changing the configuration of the gears (e.g. gears  150 ,  152 ,  154 ,  156  in spinner assembly  110 ) can increase torque while reducing a rotational speed or decrease torque while increasing a rotational speed. The speed can also be independently adjusted by increasing or decreasing a speed of the motor (e.g.  114 ) which drives the drive gear (e.g.  150 ). Changing the speed of the motor driving the drive gear is fairly straight forward but changing the gear ratio of the gears in one or both of the spinner subassemblies  110 ,  120  is not as straight forward. 
     According to certain embodiments, the spinner subassemblies  110 ,  120  of the current disclosure can be modified in the field (e.g. on the rig floor or other locations, such as at the factory) to provide increased or decreased torque to the tubular  54 . To adjust the gear ratio of the gears in a spinner subassembly  110 ,  120 , the cover of the spinner subassembly  110 ,  120  can be removed to reveal the gears inside (e.g.  150 ,  152 ,  154 ,  156 ). This description will focus on the spinner subassembly  110 , but it is equally applicable to the spinner subassembly  120 . 
     With the cover of the spinner subassembly  110  removed (as shown in  FIG. 3 ), the gears  150 ,  152 ,  154 ,  156  can be removed and replaced with gears of various sizes to increase or decrease the torque applied to the tubular  54  when compared to the torque applied to the drive gear  150  via the motor  114 . Therefore, the torque applied to the drive gear  150  can be multiplied by the resulting gear ratio of the gears  150 ,  152 ,  154 ,  156  and applied to the tubular  54  when the spinner assembly  40  is engaged with the tubular  54 . 
     To remove and replace the gears  150 ,  152 ,  154 ,  156 , each gear has a shaft (e.g. drive shaft, idler shaft, etc.) with a keyway that interfaces with a key on the respective gear. The gears  150 ,  152 ,  154 ,  156  can be removed from their respective shafts and replaced with a gear that is a different size. With different sizes, the shafts for the gears  150 ,  154 ,  156  remain in their original positions, but the shaft for the gear  152  can be repositioned to accommodate the changing sizes of the gears  150 ,  154 ,  156 . By changing these gears  150 ,  152 ,  154 ,  156  for the sizes that produce the desired gear ratio, the torque applied to the tubular  54  relative to the torque applied by the drive gear  150  can be changed. This ability to reconfigure the spinner assembly  40  with minimal disassembly allows certain embodiments of the spinner assembly  40  of this disclosure to be used in a wider range of applications. 
     By changing the gear ratios, the spinner assembly  40  can also produce various rotational speeds for spinning the tubular  54 . When lower torque is sufficient to perform the spinner functions, then the gears can be configured to increase the rotational speed of the tubular  54  to reduce threading and unthreading times. 
     Referring to  FIGS. 5A and 5B , when a tubular string  58  is being tripped into the wellbore  15 , a pipe handler  30 , top drive  18 , etc. can lower a tubular  54  to a stump of the tubular string  58  that extends above the rig floor  16 . To make a connection between the tubular  54  and the tubular string  58 , a pin end  57  of the tubular  54  can be inserted into the box end  55  of the tubular string  58 . A portion  86  of the threaded end  56  can be inserted into the box end  55  by a distance L2 before the exterior threads  80  on the threaded end  56  engage the interior threads  82  in the box end  55 . This forms a gap  84 , of distance L1, between the shoulder  88  of the pin end  57  and the top end  87  of the box end  55 . Once the engagement is achieved, the tubular  54  can then be rotated (e.g. via the spinner assembly  40 ) relative to the box end  55  to thread the joint together. When the shoulder  88  of the pin end  57  engages the top end  87  of the box end  55 , the pin end  57  has been spun into the box end  55 . At this point, the wrench assembly  42  can torque the joint to complete the connection. 
     The current disclosure describes using manufacturing specifications of tubulars to determine (e.g. estimate) the length L1 of the gap  84  for various tubular sizes, dimensions, and types. With the length L1 known (e.g. estimated, calculated, determined, etc.), then the number of revolutions needed to spin the pin end of the tubular  54  into the box end of the tubular string  58  can be determined by multiplying the length L1 times the threads per unit length (e.g. inch, mm, cm, m, etc.) of the threaded portion  56  of the pin end  57 . 
       FIG. 6A  shows a representative specification drawing  300  that defines the terms in the datasheet table  302  in  FIG. 6B . By setting the slope of the box end  55  and the pin end  57  equal to each other, and solving for the interface point yields the equation (5) below: 
         L 2=0.625+( Q   C   −D   S )/(2*( C−D   S )/( L   PC −0.625))  (5)
 
     where: 
     L2 is the setdown depth that is the distance the threaded end  56  can be inserted into the box end  55  before the exterior threads  80  on the threaded end  56  engage the interior threads  82  in the box end  55 , 
     0.625 is a distance in inches from the shoulder  88  to the top of the teeth  80  on the pin end  57 , 
     Q C  is the box end  55  counter bore diameter, 
     D S  is the pin end  57  minor bore diameter, 
     C is the pin end  57  pitch diameter at a Gage Point, and 
     L PC  is the length of the threaded portion  56  of the pin end  57 . 
     With the distance L2 calculated from the manufacturer&#39;s specifications a minimum setdown offset, MSO can be calculated by subtracting an allowance factor AF1 of 10 mm (0.394 inches) from L2. 
       MSO= L 2−AF1  (6)
 
     where: 
     MSO is a minimum setdown offset which is a minimum distance the pin end  57  can be inserted into the box end  55 , 
     L2 is a calculated distance using Equation 5 above that is the distance the threaded end  56  can be inserted into the box end  55  before the exterior threads  80  on the threaded end  56  engage the interior threads  82  in the box end  55 , and 
     AF1 is an allowance factor (e.g.) to ensure full insertion of pin end  57 . The allowance factor AF1 can be adjusted as needed. The current examples use AF1 of 10 mm (0.394 inches), but it is not required that the allowance factor AF1 be 10 mm (0.394 inches). 
     With the minimum setdown offset MSO determined, the distance L1 of the threaded portion  84  (or gap  84 ) can be determined. As seen in  FIG. 5B , L PC  is equal to L1+L2. Therefore, solving for L1 yields the equation (7) below: 
         L 1= L   PC   −L 2  (7)
 
     where: 
     L1 is the calculated distance of the gap  84  between the top end  87  of the box end  55  and the shoulder  88  of the pin end  57 , 
     L PC  is the length of the threaded portion  56  of the pin end  57 , and 
     L2 is a calculated distance using Equation 5 above that is the distance the threaded end  56  can be inserted into the box end  55  before the exterior threads  80  on the threaded end  56  engage the interior threads  82  in the box end  55 . 
     With the distance L1 determined, then the number of revolutions R 54  of the pin end  57  that would be necessary to fully thread the pin end  57  into the box end  55  can be determined. The manufacturer&#39;s specifications can be converted from English dimensions to metric dimensions, but the current specifications included in  FIGS. 6B and 7  are a mixture of both. The manufacturer&#39;s specifications in  FIG. 6B  includes the number of threads per inch TH. Therefore, the Equation (8) below can be used to calculate the number of revolutions R 54  of the pin end  57  that are needed to fully thread the pin end  57  into the box end  55  after the spinners  140  spin the tubular  54  the desired number of revolutions R 54 . 
         R   54 =( L 1* TH )  (8)
 
     where: 
     R 54  is the number of revolutions of the pin end  57  of the tubular  54  that would be necessary to fully thread the pin end  57  into the box end  55 , 
     L1 is the calculated distance of the gap  84  between the top end  87  of the box end  55  and the shoulder  88  of the pin end  57 , and 
     TH is the threads per inch supplied by the manufacturer or determined by any other means such as measuring. 
     An additional allowance factor AF2 can be added to the number of revolutions R 54  to produce a maximum number of revolutions R MAX . The maximum number of revolutions R MAX  can be used to determine if the spinners  140  have worn past an acceptable level of wear. Therefore, the allowance factor AF2 can be adjusted as needed to allow more or less wear of the spinners  140  before replacement is initiated. For example, if AF2 is equal to 0.5 revolutions, then R MAX  would be R 54 +0.5 revolutions (see Equation (9) below). This would allow an extra half-turn of the tubular  54  after spinning the tubular  54  the number of revolutions R 54 . 
         R   MAX   =R   54+ AF2  (9)
 
     where: 
     R MAX  is a maximum number of revolutions of the tubular  54  by the spinners  140 , 
     R 54  is the number of revolutions calculated for the tubular  54 , and 
     AF2 is an allowance factor to ensure tubular  54  is completely threaded into the tubular string. 
     The number of revolutions R 54  is calculated to completely thread the pin end  57  into the box end  55 . However, adding the allowance factor AF2 can help ensure that the pin end  57  is completely threaded into the box end  55 . If it takes more revolutions than the maximum number of revolutions R MAX  to spin the pin end  57  of the tubular  54  into the box end  55  of the tubular string  58 , then this can possibly indicate the spinners  140  of the spinner assembly  40  are worn past an acceptable level of wear and the wear status of the spinners indicates replacement is needed. If it takes less revolutions than the maximum number of revolutions R MAX  to spin the pin end  57  of the tubular  54  into the box end  55  of the tubular string  58 , then this can possibly indicate the spinners  140  of the spinner assembly  40  are not worn past an acceptable level of wear and the wear status of the spinners indicates spinners still operating acceptably. 
     Now that it has been shown how to calculate the maximum number of revolutions R MAX , it can be shown how to correlate the maximum number of revolutions R MAX  to the expected number of spinner revolutions R 142  and finally to the expected number of revolutions of the drive gear R 150  needed to produce the maximum number of revolutions R MAX  in the tubular  54 . 
     As stated above in Equation (4), R 142 =RT2*R 54 , with RT2 being a ratio of the outer diameter D2 of the tubular  54  to the outer diameter D1 of the spinner (i.e. D2/D1). Equation (10) below can be used to calculate the revolutions of the drive gear  150  required to rotate the spinner by the number of revolutions R 142    
         R   150   =RT 3* R   142   (10)
 
     where RT3 is a gear ratio between the drive gear  150  and the spinner gear  154 . 
     In the embodiments of the spinner subassembly  110  in  FIGS. 4A and 4B , it can be seen that all gears  150 ,  152 ,  154 ,  156  are the same size and have 16 teeth each. Therefore, a gear ratio RT3 between the drive gear  150  and the spinner gear  154  is “1:1” meaning that the spinner gear  154  will rotate the same number of revolutions as does the drive gear  150 . The spinner  142  will also rotate the same number of revolutions as does the spinner gear  154  since the spinner gear  154  is coupled directly to a drive shaft of the spinner  142 . Therefore, if the number of revolutions R 142  of the spinner  142  is given, then the number of revolutions R 150  of the drive gear  150  is known and equal to the number of revolutions R 142 , and the number of revolutions R 154  of the spinner gear  154  is known and equal to the number of revolutions R 142 . 
     Referring to  FIG. 8 , the proximity sensor  200  is shown disposed proximate a tooth  62  of the drive gear  150 . It has been shown how to calculate the maximum number of revolutions R MAX  from the manufacturing specifications and allowance factors AF1, AF2. However, to make use of the encoder that includes the proximity sensor  200  and the encoder card  204 , the maximum number of revolutions R MAX  needs to be correlated to the number of teeth  62  that have to pass by a sensing field  208  of the proximity sensor  200  to produce the maximum number of revolutions R MAX  in the tubular  54 . 
     In this example, the drive gear  150  has sixteen teeth  62 , so each revolution of the drive gear  150  will cause sixteen teeth  62  to pass through the sensing field  208  of the proximity sensor  200 , which will produce a pulse train of sixteen pulses for each revolution. Continued revolutions of the drive gear will produce additional pulses in the pulse train. The encoder card  204  can count each pulse in the pulse train to determine the total number of teeth N 62  that pass through the sensing field  208  from when a spinning operation of the spinner assembly begins and ends. It should be understood that the controller  130  (or controller  250 ) can command the spinner assembly  40  to engage the tubular  54  with the spinners  140 . 
     When the spinners  140  begin to spin the tubular  54  to make a connection to the tubular string  58 , then the encoder  204  will begin counting teeth  62  to produce the number of teeth N 62 . The controller  130  (or controller  250 ) can detect that the connection is made when the teeth counting stops, which indicates that the shoulder  88  of the pin end has engaged with the top end  87  of the box end  55 . The controller  130  (or controller  250 ) can then command the spinner assembly  40  to stop rotation of the tubular  54  and disengage from the tubular  54 . 
     The final value of the number of teeth N 62  after stopping rotation of the tubular  54  can be the value that is indicative of the total number of revolutions of the tubular  54  (i.e. N 62 /16=total number of actual revolutions AR 150  of the drive gear  150 ). The expected number of revolutions R 150  can be compared to the actual number of revolutions AR 150  to determine if the drive gear rotated more or less revolutions than expected. If it is rotated more than expected, then the spinners  140  may have an unacceptable amount of wear. If it is rotated less than expected, then the spinners  140  may have an acceptable amount of wear. If it is rotated much less than expected, then this can indicate a cross threading of the joint connection has occurred. 
     Referring back to  FIGS. 6B and 7 , an expected number of teeth N 62  will be determined for an example tubular  54  characterized by manufacturer&#39;s data and calculated data from lines  304  of the tables  302 ,  306 . The setdown depth L2 is calculated to be 3.53 inches (89.65 mm) using Equation (5). The minimum setdown offset MSO is calculated to be 3.14 inches (79.65 mm) when assuming an allowance factor AF1 of 10 mm (o.395 inches) and using Equation (6). The distance L1 of the gap  84  is calculated to be 1.36 inches (34.65 mm) using Equation (7) and substituting the minimum setdown offset MSO for the setdown depth L2. The desired number of revolutions R 54  is calculated to be 2.73 revolutions using Equation (8). The maximum number of revolutions R MAX  is calculated to be 3.23 revolutions when assuming an allowance factor AF2 of 0.5 revolutions and using Equation (9). The number of revolutions of the drive gear  150  R 150  is calculated to equal to the number of revolutions of the spinner R 142  based on Equation (10) and the ratio RT3 being “1:1”. 
     Assuming the diameter D1 of the spinner  142  is 5.125 inches, and with the diameter D2 of the tubular  54  being 5 inches (see table  302 ), then the ratio RT2 would be 5 inches/5.125 inches (per Equation (3)) that equals 0.976. Using the calculated value of R MAX  (i.e. 3.23 revolutions) for R 54  in Equation (4), with the ratio RT2 being 0.976, then the number of revolutions of the spinner R 142  (as well as R 150 ) is 3.15 revolutions for this example. With sixteen teeth for each revolution of the drive gear  150 , the total number of teeth that should pass by the pair of proximity sensors  200  is 50 (i.e.  50 . 4  rounded down). The controller  130  (or controller  250 ) can use this value (i.e. 50) to compare to the actual number of teeth  62  AN 62  that pass the pair of proximity sensors  200  when the tubular  54  is actually spun into a connection with the tubular string  58 . If more teeth  62  are counted, then the spinners may be worn past an acceptable level. If the actual number of teeth AN 62  counted is from 50 to 30, then the spinners may not be worn past an acceptable level. If fewer teeth than 30 are counted then a cross threading of the joint connection may have occurred. 
       FIG. 9  is representative of a pulse train that can be produced by the proximity sensors  200 ,  202  and sent to their respective encoder cards  204 ,  206 . It should be understood that line  212  is only representative of a pulse train that can be produced by the proximity sensors  200 ,  202  and that more of fewer pulses  214  and valleys  216  can be included in the line  212 . The pulses  214  are given an arbitrary intensity which is merely shown to represent that the pulses are at a higher level of output from the proximity sensors  200 ,  202  than the valleys  216  and this difference between the pulses  214  and the valleys  216  can be recognized by the encoder cards  204 ,  206 , respectively, to count teeth that pass the sensing field  208 ,  209 . It should be understood that other proximity sensors  200 ,  202  can be used that would basically invert the pulses  214  and valleys  216  such that a lower output level from the sensors would indicate that a tooth  62  is present and a higher level output level from the sensors would indicate a tooth  62  is not present. 
     The spinners  140  can begin to rotate at time T1 and stop rotating at time T2. This can be representative of a spin-in operation using the spinners  140 . Time period T10 represents a duration of the pulse  214  and time period T12 represents a duration of the valley  216 . The time period T14 represents a cycle time from one tooth  62  to the next tooth  62 . Up to the time T1, when the spinners  140  begin to rotate, the proximity sensor  200 ,  202  show to be positioned adjacent a valley  64  of the drive gear  150 ,  160 . 
       FIG. 10  shows representative plots  220 ,  230  of the sensor data output from proximity sensors  200 ,  202 , respectively. The plot  220  includes line  222  that can represent sensor data as a function of time for the proximity sensor  200  of the spinner subassembly  110 . The plot  230  includes line  232  that can represent sensor data as a function of time for the proximity sensor  202  of the spinner subassembly  120 . In this example, both drive gears  150 ,  160  begin rotating at time T1, with each of the proximity sensors  200 ,  202  positioned proximate a valley  64  on the drive gear  150 ,  160 , respectively. 
     The sensor data indicates that the drive gears  150 ,  160  are in sync through time T3, but become slightly out of sync by time T4. Notice the valley  226  and pulse  224  proximate time T4 are narrowed when compared to the valley  236  and the pulse  234  of line  232 . Line  222  indicates by time T4 that a tooth  62  has passed through the sensing field  208  of the proximity sensor  200  earlier than the tooth  62  passed through the sensing field  209  proximity sensor  202 . This can indicate that the spinners  142 ,  144  of the spinner subassembly  110  may have slipped on the tubular  54  that would have, at least temporarily, accelerated the drive gear  150 . From time T4 to T5, the drive gears  150 ,  160  seem to be rotating at the same speed until close to time T5, where the drive gear  150  again temporarily accelerates relative to the drive gear  160 . At time T2, when the spinner assembly  40  is stopped and disengaged from the tubular  54 , the drive gears  150 ,  160  remain out of sync with each other. 
     It should be understood that it is not a requirement that the drive gears  150 , and  160  be in sync at any point in time. It can start at time T2 out of sync and end at time T3 out of sync. However, with them in sync at the beginning of this example, it is easier to understand the variations between the two lines  222 ,  232 , and thus the two drive gears  150 ,  160 , respectively. 
       FIG. 10  indicates that a wear status for the spinners  140  can be determined by comparing the performance of the spinners  140  (i.e.  142 ,  144 ) in the spinner subassembly  110  to the performance of the spinners  140  (i.e.  146 ,  148 ) in the spinner subassembly  120 . If the tooth count N 62  from the encoder card  204  is greater than the tooth count N 62  from the encoder  206  by a pre-determined number, or the tooth count N 62  from the encoder card  204  is less than the tooth count N 62  from the encoder  206  by a pre-determined number, the controller  130  (or rig controller  250 ) can determine which of the encoder cards  204 ,  206  provided a tooth count N 62  that is outside of a value range, then the controller  130  (or rig controller  250 ) can initiate remove and replace operations to replace the spinners in the failing spinner subassembly  110 ,  120 . 
       FIG. 11  are representative plots  240 ,  250  of the sensor data output from proximity sensors  200 ,  202 , respectively. The plot  240  includes line  242  that can represent sensor data as a function of time for the proximity sensor  200  of the spinner subassembly  110 . The plot  250  includes line  252  that can represent sensor data as a function of time for the proximity sensor  202  of the spinner subassembly  120 . In this example, both drive gears  150 ,  160  begin rotating at time T1, with each of the proximity sensors  200 ,  202  positioned proximate a valley  64  on the drive gear  150 ,  160 , respectively. 
     The lines  242 ,  252  indicate that the drive gear  150  (and thus the spinners  142 ,  144 ) of the spinner subassembly  110  are rotating faster than the drive gear  160  (and thus the spinners  146 ,  148 ) of the spinner subassembly  120 . This appears to indicate that the spinners  142 ,  144  are continuing to slip on the tubular  54  during the spin-in operation. The speed the teeth  64  are moving through the sensing fields  208 ,  209  can also be used to calculate the speed the drive gear  150 ,  160  is rotating and thus the speed that the spinners  142 ,  144 ,  146 ,  148 , respectively, are rotating. As can be seen, the cycle time T14 of the line  242  between times T3 and T4 is shorter than the cycle time T14 of the line  252  in that same time period. 
     Referring to  FIG. 12 , the encoder function can be used to determine if a tubular  54  has been completely spun-out of the box end  55  of a tubular string  58 . During tripping a tubular string  58  out of the wellbore  15 , the top tubular  54  in the tubular string  58  is broken loose by a torque wrench  42 , and then the spinner assembly  40  can spin the tubular  54  the rest of the way out of the box end  55  of the tubular string  58 . The encoder function along with the controller  130  or controller  250  can be used to determine a speed of rotation of the drive gears  150 ,  160  of the spinner subassemblies,  110 ,  120 , respectively. 
     The plot  260  includes a line  262  that can represent a pulse train from either of the proximity sensors  200 ,  202 . At time T1, the spinner assembly  40  begins rotating the spinners  140  to unthread the tubular  54  from the box end  55  of the tubular string  58 . The pulses  264  and valleys  266  indicate a steady speed of rotation of the drive gear  150 ,  160 , when at time T3 the speed of rotation of the drive gear  150 ,  160  is increased as seen by a shortened cycle time T14 between times T3 and T2. The increased speed of rotation between times T3 and T2 can indicate that the rotational speed of the tubular  54  has increased due to reduced friction of the threads, and the tubular  54  is completely unthreaded from the box end  55  of the tubular string  58 . 
     Referring to  FIG. 13 , this configuration is very similar to the configuration shown in  FIG. 8 . However, this configuration differs from  FIG. 8  in that the proximity sensor  200  of  FIG. 8  is replaced by a pair of proximity sensors  200   a ,  200   b . The proximity sensor  200   a  has an associated sensing field  208   a , and the proximity sensor  200   b  has an associated sensing field  208   b . Each proximity sensor  200   a ,  200   b  can be coupled to a separate input of the encoder card  204 , where the encoder card  204  can receive a pulse train from each of the proximity sensors  200   a ,  200   b  that represent the presence of a tooth  62  as each tooth  62  passes through the respective sensing fields  208   a ,  208   b . It should be understood that the previous description regarding the proximity sensor  200  is applicable to each of the proximity sensors  200   a ,  200   b , where each can detect the teeth  62  of the drive gear  150  and provide a pulse train to the encoder card  204 . 
     Similarly, the proximity sensor  202  of  FIGS. 3, 4A, 4B  can be replaced by a pair of proximity sensors  202   a ,  202   b . The proximity sensor  202   a  has an associated sensing field  209   a , and the proximity sensor  202   b  has an associated sensing field  209   b . Each proximity sensor  202   a ,  202   b  can be coupled to a separate input of the encoder card  206 , where the encoder card  206  can receive a pulse train from each of the proximity sensors  202   a ,  202   b  that represent a presence of a tooth  62  as each tooth  62  passes through the respective sensing fields  209   a ,  209   b . It should be understood that the previous description regarding the proximity sensor  202  is applicable to each of the proximity sensors  202   a ,  202   b , where each can detect the teeth  62  of the drive gear  150  and provide a pulse train to the encoder card  206 . 
     Referring to  FIG. 14 , a benefit of having a pair of proximity sensors  208   a ,  208   b  instead of a single proximity sensor  208  is that the encoder card  204  (or the controllers  130  or  250 ) can compare the pulse trains from each of the proximity sensors  208   a ,  208   b  and determine which direction the drive gear  150  is rotating.  FIG. 14  shows a plot  270  that includes two lines  272 ,  273 . The line  272  represents a pulse train produced by the proximity sensor  208   a  with pulses  274  and valleys  276 . The line  273  represents a pulse train produced by the proximity sensor  208   b  with pulses  275  and valleys  277 . As can be seen in  FIG. 14 , the sensing fields  208   a ,  208   b  are slightly offset from each other. This can be done by placing one proximity sensor  200   a  above and slightly offset from the proximity sensor  208   b.    
     As the drive gear  150  rotates, a tooth  62  will pass through the sensing fields  208   a ,  208   b . However, the tooth will enter the sensing field of one proximity sensor before it enters the next. For example, if the drive gear  150  is rotating clockwise (arrow  170 ), then the tooth  62  will enter the sensing field  208   a  first before it enters the sensing field  208   b , thereby causing the pulse generated by the proximity sensor  208   a  to be output at a time slightly ahead of when the pulse generated by the proximity sensor  208   b  is output. This can cause a shift  278  between the pulse trains (i.e. lines  272 ,  273 ) of time T16. When the encoder card  204  receives the pulses trains (i.e. lines  272 ,  273 ) it can determine (or other controllers  130  or  250 ) that the tooth  62  enters the sensing field  208   a  of the proximity sensor  200   a  before it enters the sensing field  208   b  of the proximity sensor  200   b , thereby indicating the drive gear is rotating in a clockwise direction. The same analysis can be performed if the drive gear  150  were rotating in a counterclockwise direction, with the teeth entering the sensing field  208   b  before entering the sensing field  208   a.    
     Referring to  FIG. 15A , the iron roughneck  38  can include a compensation system  290  for when the spinner assembly  40  is spinning a tubular in or out of connection with a tubular string  58 . The compensation system  290  can include a vertically orientated actuator  280  and a hydraulic control circuit  310  (see  FIG. 15B ). The actuator  280  can vertically raise or lower the coupling assembly  60  of the spinner assembly  40 , thereby vertically raising or lowering the spinner subassemblies  110 ,  120  relative to the torque wrench assembly  42  (i.e. varying the height L3). This vertical adjustment can be used to position the spinners  140  along the body of the tubular  54  as needed to spin the tubular  54  in or out. The compensation system  290  can provide weight compensation to offset the weight of spinner assembly  40  and the tubular  54  to minimize weight being applied to the joint of the tubular string  58  when the tubular  54  is being spun in or spun out. Also, the compensation system  290  provides for vertical movement of the spinner assembly  40  as the tubular  54  is being spun in or spun out, since the spinning in or out requires vertical displacement of the tubular  54  relative to the tubular string  58 . 
     Referring now to  FIG. 15B , a diagram of a hydraulic circuit  310  is provided that can be used to control the vertical displacement of the spinner assembly  40  via the actuator  280 . “A” and “B” represent the fluid ports of the actuator  280 , “P” represents pressure from a pressure source (e.g. a Hydraulic Power Unit HPU), “T” represents a tank (e.g. for collecting fluid from a return line to the HPU). A slide valve  320  can be used to control actuation of the actuator  280  by sliding the valve to one of a plurality of control positions  322 ,  324 ,  326 ,  328 , with solenoids  316 ,  318  used to actuate the slide valve between the control positions. Injecting fluid into port “A” and releasing fluid from port “B” extends the piston  282 . Injecting fluid into port “B” and releasing fluid from port “A” retracts the piston  282 . The counterbalance valves  330 ,  332  operate to prevent fluid flow until the inlet pressure exceeds a predetermined value and causes the piston in the counterbalance valve to overcome a biasing force acting on the piston. When the piston overcomes the biasing force, the counterbalance valve allows fluid to flow from the pressurized input through the valve to the output. When the input pressure is reduced below the pre-determined value, then the counterbalance valve again prevents flow through the valve. The check valves  340 ,  342  act to allow only one-way fluid communication through the respective lines. 
     In operation, the normal configuration of the slide valve is for the valve to be at the control position  326  which is a “blocking” position. At control position  326 , fluid is prevented from flowing in to or out of the ports “A” and “B”. This locks the actuator piston at its current position. This control position  326  can be used when it is desired to prevent movement of the piston via the slide valve, yet the piston can still move via the counterbalance valves. The control position  322  that is a “float” position, where the ports “A” and “B” are in fluid communication with each other and the piston is allowed to extend or retract without resistance. The control position  324  that can be a “retract” position, where pressure P is applied through the slide valve  320  to the “B” port and the “A” port is in fluid communication with the return line “T”. The control position  328  that can be an “extend” position, where pressure P is applied through the slide valve  320  to the “A” port and the “B” port is in fluid communication with the return line “T”. 
     When the spinner assembly  40  is set to spin in or out a tubular  54 , the slide valve can be moved to the control position  326  when the spinner assembly  40  has been moved to the desired vertical position by the actuator  280 . The spinner assembly  40  can engage the tubular  54  with the spinners  140  and begin spinning the tubular  54 . 
     If the tubular  54  is being spun into the end of the tubular string  58 , then the spinner assembly will be pulled vertically down by the vertical movement of the tubular  54  as it is being threaded into the tubular string  58 . Since the slide valve  320  is at control position  326 , fluid is prevented from flowing through the slide valve. Therefore, the downward vertical movement of the tubular  54 , and thus the spinner assembly  40  that is engaged with the tubular  54 , will begin to build up pressure in the actuator  280  at the “A” port. When this pressure at the “A” port is equal to or exceeds the pre-determined value set by the counterbalance valve  330 , the counterbalance valve  330  will open and allow fluid to flow through the counterbalance valve  330  to the “T” line, thus relieving pressure at port “A”. Also, pressure at port “B” will be reduced and the check valve  342  can allow fluid to flow from the “T” line into the “B” port to prevent negative pressure at port “B”. 
     If the tubular  54  is being spun out of the end of the tubular string  58 , then the spinner assembly will be pulled vertically up by the vertical movement of the tubular  54  as it is being threaded out of the tubular string  58 . Since the slide valve  320  is at control position  326 , fluid is prevented from flowing through the slide valve. Therefore, the upward vertical movement of the tubular  54 , and thus the spinner assembly  40  that is engaged with the tubular  54 , will begin to build up pressure in the actuator  280  at the “B” port. When this pressure at the “B” port is equal to or exceeds the pre-determined value set by the counterbalance valve  332 , the counterbalance valve  332  will open and allow fluid to flow through the counterbalance valve  332  to the “T” line, thus relieving pressure at port “B”. Also, pressure at port “A” will be reduced and the check valve  340  can allow fluid to flow from the “T” line into the “A” port to prevent negative pressure at port “A”. 
     The pre-determined value for the counterbalance valves  330 ,  332  can be set to compensate for the weight of the spinner assembly and the tubular  54 , so the actuator  280  moves when the pre-determined value is exceeded (i.e. additional force caused by the vertical movement of the spinner assembly  40  during spin in or out operation). If the control position  322  is selected for the slide valve  320 , then the piston of the actuator  280  is free to float and provides no counterbalance force to offset the weight of the spinner assembly  40  and the tubular  54 . Therefore, the entire weight of the tubular  54  and the spinner assembly  40  can be acting on the threads of the connection. 
       FIG. 16  is a representative partial cross-sectional view of an actuator  350 , that can be used for actuators of the iron roughneck  38  (e.g. actuator  70 , actuator  280 ), in accordance with certain embodiments. The end  380  can be rigidly attached to a body  352  of the actuator  350 . The opposite end  382  can be rigidly attached to an end of a piston rod  354  that is extendable from the body  352 . The opposite end of the piston rod  354  can include a cylindrical disk  364  that is slidably and sealingly coupled to a bore  362  in the body  352 . The seal  374  can be used to seal the disk  364  to the bore  362 . Fluid inlets  386 ,  388  can be used to drive the cylindrical disk  364  along the bore  362  in the body  352  to extend or retract the piston rod  354  as is well known in the art of pistons. The annular space  372  provides a volume for the inlet  388  to inject fluid into the actuator  350  to retract the piston rod  354 . Injecting fluid into the cavity  370  can extend the piston rod  354 . The seal  376  can slidingly and sealingly engage the piston rod  354  with the body  352 . 
     The actuator  350  can include a Linear Variable Differential Transformer (LVDT) sensor. The LVDT sensor can detect and report a position of the piston rod  354  relative to the body  352 . The LVDT sensor  366  can include a transducer electromagnetic core  368  that is stationary relative to the body  352  and can extend further into the bore  356  of the piston rod  354  as the piston rod  354  retracts from its fully extended position. A coil assembly in the transducer core  368  can detect the position of the piston rod  354  as it variably extends or retracts in the cavity  370  of the body  352 . As the extension of the transducer core  368  varies within the bore  356 , the transducer coil  368  correspondingly detects variations in its magnetic field which can be interpreted to determine the position of the transducer core  368  relative to the piston rod  354 . The transducer coil  368  can receive electrical energy via the connection  360  as well as communicate the sensor signal to the controller (e.g. controller  250 ,  130 ) through the connection  360 . The controller can provide proper signal conditioning for reading and processing the sensor signal. 
     Referring again to  FIG. 15A , using an actuator  350  type actuator for the actuator  280 , a controller (e.g. controller  250 , controller  130 , etc.) can use the relative position of the piston rod  282  relative to the body  284  to determine the vertical position of the spinner assembly  40  as well as the vertical position of the spinners  140 , thereby providing real-time verification of the vertical position of the spinners  140 . Monitoring, in real-time, the vertical position of the spinners  140 , the controller can determine a vertical distance traveled by the spinners  140  when they spin in or out a tubular  54 . The encoders  200 ,  202  ( FIG. 3 ) can provide, in real-time, the number of turns performed when the tubular  54  is spun in or out of the connection to the tubular string  58 . 
     Referring again to  FIG. 3 , using an actuator  350  type actuator for the actuator  70 , a controller (e.g. controller  250 , controller  130 , etc.) can use the relative position of the piston rod of the actuator  70  to determine a horizontal position of each of the spinner subassemblies  110 ,  120  and thereby determine a diameter D2 of the tubular  54 . 
     Therefore, the spinner assembly  40  and controller can be used to “map” a new connection for which parameters of the tubular  54  or have not been provided. As used herein, “map” or “mapping” the connection refers to the spinner assembly  40  and the controller  250 ,  130  being used to determine the thread pitch, number of threads, and diameter D2 of the tubular  54 . If these parameters are known for the tubular  54 , then mapping the connection can be used to verify the parameters of the tubular  54 . 
     Various Embodiments 
     Embodiment 1. A system for conducting subterranean operations, the system comprising: 
     a spinner assembly comprising:
         an encoder; and   a spinner subassembly, the spinner subassembly comprising:
           a spinner configured to engage a tubular; and   a drive gear coupled to the spinner, with the drive gear configured to drive rotation of the spinner, and the encoder configured to count teeth of the drive gear as the drive gear rotates.   
               

     Embodiment 2. The system of embodiment 1, wherein the drive gear is coupled to the spinner by a drive shaft, a belt, or linkage. 
     Embodiment 3. The system of embodiment 1, wherein the encoder comprises an encoder card disposed on the iron roughneck and disposed outside of the spinner assembly, and a proximity sensor coupled to the encoder card, with the proximity sensor disposed proximate the drive gear such that the teeth of the drive gear pass through a sensing field of the proximity sensor when the drive gear rotates. 
     Embodiment 4. The system of embodiment 3, wherein the encoder card counts a total number of teeth that pass through the sensing field during operation of the spinner assembly. 
     Embodiment 5. The system of embodiment 4, wherein the total number of teeth indicate a wear status of the spinner. 
     Embodiment 6. The system of embodiment 5, wherein the wear status indicates an acceptable amount of wear of the spinner. 
     Embodiment 7. The system of embodiment 5, wherein the wear status indicates an unacceptable amount of wear of the spinner. 
     Embodiment 8. The system of embodiment 7, wherein a maintenance operation is initiated based on the wear status. 
     Embodiment 9. The system of embodiment 3, wherein the proximity sensor produces a pulse train when the drive gear rotates, wherein the proximity sensor transmits the pulse train to the encoder card, and wherein the pulse train indicates when the teeth pass through the sensing field. 
     Embodiment 10. The system of embodiment 9, wherein a controller is configured to determine a rotational speed of the drive gear based on the pulse train. 
     Embodiment 11. The system of embodiment 9, wherein the pulse train indicates when the tubular is unthreaded from a tubular string. 
     Embodiment 12. The system of embodiment 1, wherein the spinner assembly comprises a first spinner subassembly and a second spinner subassembly, and wherein the encoder comprises a first encoder and a second encoder. 
     Embodiment 13. The system of embodiment 12, wherein the first spinner subassembly comprises: 
     a first spinner configured to engage the tubular; and 
     a first drive gear coupled to the first spinner and configured to drive rotation of the first spinner, and the first encoder configured to count teeth of the first drive gear as the first drive gear rotates. 
     Embodiment 14. The system of embodiment 13, wherein the first encoder comprises a first encoder card and a first proximity sensor, and wherein a first proximity sensor is disposed proximate the first drive gear such that the teeth of the first drive gear pass through a first sensing field of the first proximity sensor when the first drive gear rotates. 
     Embodiment 15. The system of embodiment 14, wherein the first proximity sensor produces a first pulse train when the first drive gear rotates, wherein the first proximity sensor transmits the first pulse train to the first encoder card, and wherein the first pulse train indicates when the teeth of the first drive gear pass through the first sensing field. 
     Embodiment 16. The system of embodiment 15, wherein a controller is configured to determine a rotational speed of the first drive gear based on duration of pulses and valleys in the first pulse train. 
     Embodiment 17. The system of embodiment 15, wherein the second spinner subassembly comprises: 
     a second spinner configured to engage the tubular; and 
     a second drive gear coupled to the second spinner and configured to drive rotation of the second spinner, and the second encoder configured to count teeth of the second drive gear as the second drive gear rotates. 
     Embodiment 18. The system of embodiment 17, wherein the second encoder comprises a second encoder card and a second proximity sensor, and wherein the second proximity sensor is disposed proximate the second drive gear such that the teeth of the second drive gear pass through a second sensing field of the second proximity sensor when the second drive gear rotates. 
     Embodiment 19. The system of embodiment 18, wherein the second proximity sensor produces a second pulse train when the second drive gear rotates, wherein the second proximity sensor transmits the second pulse train to the second encoder card, and wherein the second pulse train indicates when the teeth of the second drive gear pass through the second sensing field. 
     Embodiment 20. The system of embodiment 19, wherein a controller is configured to determine a rotational speed of the first drive gear based on duration of pulses and valleys in the first pulse train, and wherein the controller is configured to determine a rotational speed of the second drive gear based on duration of pulses and valleys in the second pulse train. 
     Embodiment 21. The system of embodiment 19, wherein a comparison of the first pulse train to the second pulse train indicates a wear status of the first spinner or the second spinner. 
     Embodiment 22. A system for conducting a subterranean operation, the system comprising: 
     a spinner subassembly comprising: 
     a plurality of spinners configured to engage and rotate a tubular; 
     a drive gear that is coupled to the plurality of spinners, with the drive gear configured to rotate the plurality of spinners; 
     a proximity sensor configured to detect teeth of the drive gear as the teeth pass through a sensing field of the proximity sensor; and 
     a controller configured to receive first sensor data from the proximity sensor, wherein the first sensor data is representative of an actual number of revolutions of the plurality of spinners when the plurality of spinners engages the tubular. 
     Embodiment 23. The system of embodiment 22, wherein the actual number of revolutions comprise multiple revolutions, a single revolution, a partial revolution, or combinations thereof. 
     Embodiment 24. The system of embodiment 22, wherein the actual number of revolutions indicates a wear status of the plurality of spinners. 
     Embodiment 25. The system of embodiment 22, wherein the actual number of revolutions of the plurality of spinners is greater than a pre-determined number of revolutions and indicates a wear status of the plurality of spinners is unacceptable. 
     Embodiment 26. The system of embodiment 22, wherein the actual number of revolutions of the plurality of spinners is less than a pre-determined number of revolutions and indicates a wear status of the plurality of spinners is acceptable. 
     Embodiment 27. The system of embodiment 22, wherein the actual number of revolutions of the plurality of spinners is less than a pre-determined number of revolutions and indicates the tubular has been successfully threaded into a tubular string. 
     Embodiment 28. The system of embodiment 22, further comprising a torque sensor configured to measure torque applied to the drive gear, wherein an increase in the torque indicates the tubular is fully threaded to a tubular string. 
     Embodiment 29. A method for conducting a subterranean operation, the method comprising: 
     engaging a tubular with a spinner; 
     rotating a drive gear, with the drive gear coupled to the spinner; 
     rotating the spinner in response to rotating the drive gear; 
     rotating the tubular in response to rotating the spinner; and 
     counting, via an encoder, teeth of the drive gear as the teeth pass through a sensing field of a proximity sensor. 
     Embodiment 30. The method of embodiment 29, further comprising calculating an actual number of the teeth that passes through the sensing field while the spinner engages the tubular. 
     Embodiment 31. The method of embodiment 30, determining a wear status of the spinner based on the actual number of the teeth. 
     Embodiment 32. The method of embodiment 31, wherein determining the wear status further comprises comparing the actual number of the teeth to a pre-determined number of teeth. 
     Embodiment 33. The method of embodiment 32, wherein the determining that the actual number of the teeth is less than the pre-determined number of teeth, thereby indicating that the wear status of the spinner is acceptable. 
     Embodiment 34. The method of embodiment 32, wherein the determining that the actual number of the teeth is less than the pre-determined number of teeth, thereby indicating that the tubular is fully threaded into a tubular string. 
     Embodiment 35. The method of embodiment 32, wherein the determining that the actual number of the teeth is greater than the pre-determined number of teeth, thereby indicating that the wear status of the spinner is unacceptable. 
     Embodiment 36. The method of embodiment 35, further comprising initiating a maintenance in response to indicating the wear status is unacceptable. 
     Embodiment 37. The method of embodiment 32, further comprising determining the pre-determined number of teeth by calculating a gap between a shoulder of a pin end of the tubular and a top end of the tubular string when the pin end of the tubular is setdown in a box end of the tubular string. 
     Embodiment 38. The method of embodiment 37, wherein determining the pre-determined number of teeth further comprises calculating a number of revolutions of the tubular needed to fully thread the tubular into the tubular string. 
     Embodiment 39. The method of embodiment 38, wherein determining the pre-determined number of teeth further comprises calculating a number of revolutions of the spinner based on the number of revolutions of the tubular. 
     Embodiment 40. The method of embodiment 29, wherein the proximity sensor produces a pulse train, and wherein each pulse of the pulse train indicates that one of the teeth of the drive gear passed through the sensing field of the proximity sensor. 
     Embodiment 41. The method of embodiment 40, further comprising determining a rotational speed of the drive gear based on the pulse train. 
     Embodiment 42. The method of embodiment 41, further comprising determining the tubular is fully unthreaded from a tubular string based on a variation in the rotational speed of the drive gear. 
     Embodiment 43. A system for conducting subterranean operations, the system comprising: 
     a spinner assembly comprising:
         a first encoder;   a first spinner subassembly, the first spinner subassembly comprising:
           a first spinner configured to engage a tubular; and   a first drive gear coupled to the first spinner, with the first drive gear configured to drive rotation of the first spinner, and the first encoder configured to count teeth of the first drive gear as the first drive gear rotates;   
           a second encoder;   a second spinner subassembly, the second spinner subassembly comprising:
           a second spinner configured to engage a tubular; and   a second drive gear coupled to the second spinner, with the second drive gear configured to drive rotation of the second spinner, and the second encoder configured to count teeth of the second drive gear as the second drive gear rotates.   
               

     Embodiment 44. The system of embodiment 43, wherein the first encoder produces a first pulse train, wherein each pulse in the first pulse train indicates a tooth of the first drive gear that passed through a sensing field of the first encoder. 
     Embodiment 45. The system of embodiment 44, wherein the first pulse train indicates a wear status of the first spinner. 
     Embodiment 46. The system of embodiment 44, wherein the second encoder produces a second pulse train, wherein each pulse in the second pulse train indicates a tooth of the second drive gear that passed through a sensing field of the second encoder. 
     Embodiment 47. The system of embodiment 46, wherein the second pulse train indicates a wear status of the second spinner. 
     Embodiment 48. The system of embodiment 46, further comprising a controller, wherein the controller is configured to compare the first pulse train to the second pulse train and determine a wear status of the first spinner or the second spinner. 
     Embodiment 49. A method for conducting a subterranean operation, the method comprising: 
     adjusting, via a vertically oriented actuator, a height of a spinner assembly relative to a torque wrench assembly; 
     engaging a tubular with a spinner assembly by actuating a horizontally oriented actuator; 
     measuring a horizontal movement of the spinner assembly via a Linear Variable Differential Transformer (LVDT) sensor; 
     calculating an outer diameter of the tubular based on the measured horizontal movement of the spinner assembly; 
     spinning the tubular into a threaded connection with a tubular string; 
     measuring vertical movement of the spinner assembly as the tubular is spun into the threaded connection; 
     measuring, via an encoder, a number of revolutions of a spinner in the spinner assembly by sensing teeth of a drive gear coupled to the spinner as the teeth pass through a sensing field of the encoder; 
     determining thread pitch of a pen end of the tubular, thread diameter of the threads of the pin end of the tubular, and number of threads of the pin end of the tubular based on the number of revolutions of the spinner, the outer diameter of the tubular, and the vertical movement of the spinner assembly. 
     Embodiment 50. A method of varying torque of a spinner assembly, the method comprising: 
     installing a first drive gear in the spinner assembly; 
     coupling a spinner to the first drive gear via a first slave gear; 
     engaging the spinner with a tubular and applying a first rotational torque to the tubular; 
     removing the first drive gear and the first slave gear; 
     installing a second drive gear in the spinner assembly; 
     coupling the spinner to the second drive gear via a second slave gear; 
     engaging the spinner with the tubular and applying a second rotational torque to the tubular. 
     Furthermore, the illustrative methods described herein may be implemented by a system comprising a rig controller  250 ,  130  that can include a non-transitory computer-readable medium comprising instructions which, when executed by at least one processor of the rig controller  250 ,  130 , causes the processor to perform any of the methods described herein. 
     While the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and tables and have been described in detail herein. However, it should be understood that the embodiments are not intended to be limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the following appended claims. Further, although individual embodiments are discussed herein, the disclosure is intended to cover all combinations of these embodiments.