what is a power tong operator free sample

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In oilfield exploration and production operations, various oilfield tubular members are used to perform important tasks, including, but not limited to, drilling the wellbore and casing a drilled wellbore. For example, a long assembly of drill pipes, known in the industry as a drill string, may be used to rotate a drill bit at a distal end to create the wellbore. Furthermore, after a wellbore has been created, a casing string may be disposed downhole into the wellbore and cemented in place to stabilize, reinforce, or isolate (among other functions) portions of the wellbore. As such, strings of drill pipe and casing may be connected together, such as end-to-end by threaded connections, in which a male “pin” end of a first tubular member is used to threadably engage a corresponding female “box” end of a second tubular member. Alternatively, a tubular string may be made-up of a series of male-male ended tubular joints coupled together by female-female couplers. The process by which the threaded connections are assembled is called “making-up” a threaded connection, and the process by which the connections are disassembled is referred to “breaking-out” the threaded connection. As would be understood by one having ordinary skill, individual pieces (or “joints”) of oilfield tubular members may come in a variety of weights, diameters, configurations, and lengths.

Power tongs are machines that may be used to make-up and break-out threaded connections between adjacent tubular segments by gripping and rotating a first tubular segment relative to a second tubular segment to either make-up or break-out the threaded connection between the two tubular segments. FIG. 1 is a perspective view of an example of an externally gripping power tong 100. The power tong 100 includes a drive motor 110 that may be hydraulically, electrically, and/or pneumatically-powered, and a gripping assembly mechanically coupled to the motor 110 for gripping and rotating a tubular segment received within a bay 106. A generally “C”-shaped gear housing 112 supports a pair of pivoting doors 114. The doors 114 may be closed to secure the bay 106 or swung open (as indicated in FIG. 1) to provide access to the bay 106. The bay 106 is generally surrounded by the gear housing 112. The center of the bay 106 is between a pair of generally opposed pivotable gripping jaws 120, each having a generally arcuate gripping surface disposed radially inwardly toward the center of the bay 119.

Makeup requirements for tubular connections require high torque, such as in the order of thousands, and up to tens of thousands, of ft-lb torque. The components of a power tong must be capable of producing and sustaining the torques required to rotate tubular segments. As such, safely and effectively handling tubular members within an oilfield environment remains a priority to increase the efficiency and effectiveness of such tubular handling equipment.

FIGS. 2A-2C show multiple views of a power tong assembly used to grip and rotate a tubular segment in accordance with one or more embodiments of the present disclosure;

FIGS. 5A and 5B show multiple schematic views of a simplified hydraulic circuit for a power tong assembly in accordance with one or more embodiments of the present disclosure.

The following discussion is directed to various embodiments of the invention. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.

Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not structure or function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . . ” Also, the term “couple” or “couples” is intended to mean either an indirect or direct coupling, and the “connect” or “connects” is intended to mean either an indirect or direct connection, unless otherwise denoted. In addition, the terms “axial” and “axially” generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the central axis. The use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components.

In accordance with various aspects disclosed herein, the present disclosure relates to a power tong assembly that may be used to make-up, break-out, and/or torque two or more tubular members, such as within an oilfield exploration and production operation environment discussed above. The power tong assembly includes a power tong is configured to grip and rotate a tubular segment in a first direction, such as to make-up a threaded connection with the tubular segment, and in a second direction, such as to break-out the threaded connection with the tubular segment. The power tong assembly further includes an interlock system operably coupled to the power tong, in which the interlock system may be configured to selectively allow the power tong to rotate the tubular segment in one of the first direction and the second direction while preventing the power tong to rotate the tubular segment in the other of the first direction and the second direction. The interlock system may, additionally or alternatively, be configured to selectively allow the power tong to rotate or not rotate in response to conditions that are sensed by the interlock system.

For example, the power tong may be operated in two directions, such as a make-up direction (e.g., operated in a make-up setting) and a break-out direction (e.g., operated in a break-out setting), in which the make-up setting enables the power tong to rotate a tubular segment in the first direction to make-up a threaded connection with the tubular segment, and the break-out setting enables the power tong to rotate the tubular segment in the second direction to break-out the threaded connection with the tubular segment. Further, the interlock system includes a make-up setting that allows the power tong to rotate the tubular segment in the first direction to make-up the threaded connection with the tubular segment and a break-out setting that allows the power tong to rotate the tubular segment in the second direction to break-out the threaded connection with the tubular segment. As such, the interlock system is configured to prevent the power tong to operate in the make-up setting when the interlock system is in the break-out setting, and further is configured to prevent the power tong to operate in the break-out setting when the interlock system is in the make-up setting.

In one or more embodiments, the power tong may include a high-speed setting to rotate the tubular segment in the first direction and the second direction in a high gear and a low-speed setting to rotate the tubular segment in the first direction and the second direction in a low gear. Accordingly, in one embodiment, the interlock system is configured to allow the power tong to operate in the make-up setting and the high-speed setting only when the interlock system is in the make-up setting, and is configured to allow the power tong to operate in the break-out setting and the high-speed setting only when the interlock system is in the break-out setting. The interlock system may further include a selector mechanism, such as a plug assembly or a three-way valve, which enables the interlock system to move between the make-up setting and the break-out setting. Further, the interlock system may include a power tong gear position sensor. The power tong gear position sensor may be used to sense and determine if the power tong is configured to operate in high gear (e.g., a high-speed setting) or operate in low gear (e.g., a low-speed setting). Accordingly, as discussed more below, the interlock system may use the selector mechanism and/or the power tong gear position sensor to sense the setting or mode of operation of the power tong, in which the interlock system may be configured to selectively allow the power tong to rotate or not rotate in response to conditions that are sensed by the selector mechanism and/or the power tong gear position sensor of the interlock system. Furthermore, the interlock system may be operably coupled to a bi-directional hydraulic motor of the power tong such that the interlock system disables the hydraulic motor to prevent the power tong to rotate the tubular segment in the other of the first direction and the second direction.

In one or more embodiments, the interlock system may include a selector mechanism, in which the selector mechanism may be used as a tong operator interface to switch and move the interlock system between the make-up setting and the break-out setting. In such an embodiment, if the selector mechanism is in the make-up setting (e.g., a make-up position) and the power tong is actuated in the make-up direction, the interlock system may permit the power tong to operate. In particular, the interlock system may permit the power tong to operate in the make-up direction in high-speed (e.g., the high-speed setting) and low-speed (e.g., the low-speed setting) if the selector mechanism of the interlock system is in the make-up position. Further, in such an embodiment, the interlock system may prevent or block the power tong to operate in the break-out direction in high-speed and only permit the power tong to operate in the break-out direction in low-speed if the selector mechanism of the interlock system is in the make-up position.

Further, if the selector mechanism is in the break-out setting (e.g., a break-out position) and the power tong is actuated in the break-out direction, the interlock system may permit the power tong to operate. In particular, the interlock system may permit the power tong to operate in the break-out direction in high-speed and low-speed if the selector mechanism of the interlock system is in the break-out position. Further, in such an embodiment, the interlock system may prevent or block the power tong to operate in the make-up direction in high-speed and only permit the power tong to operate in the make-up direction in low-speed if the selector mechanism of the interlock system is in the break-out position.

Referring now to FIGS. 2A, 2B, and 2C, multiple views of a power tong assembly 200 used to grip and rotate a tubular segment 202 in accordance with one or more embodiments of the present disclosure are shown. In particular, FIG. 2A shows a perspective view of the power tong assembly 200 when in use to make-up and/or break-out a threaded connection between a first upper tubular segment 202A and a second lower tubular segment 202B, FIG. 2B shows an above schematic view of the power tong assembly 200 when in use to make-up a threaded connection with the tubular segment 202, and FIG. 2C shows another above schematic view of the power tong assembly 200 when in use to break-out a threaded connection with the tubular segment 202.

In one or more embodiments, when making-up and breaking-out threaded connections between tubular segments, a mechanism or component is used to hold reaction torque on one tubular segment while the power tong is used to rotate the other tubular segment. One or more power tong assemblies may include with integral backup wrenches, in which the backup wrench may hold reaction torque on a tubular segment while the power tong makes-up and breaks-out threaded connections by rotating an adjacent tubular segment. In an embodiment in which a power tong assembly does not include an integral backup wrench, such as shown in FIG. 2A, reaction torque may be held on the lower tubular segment 202B using a drilling rotary 204 and/or other tubular gripping mechanism (e.g., a manual tong, a spider, a collar load support), while the power tong assembly 200 is used to rotate and apply torque to the upper tubular segment 202A.

As shown in FIGS. 2A-2C, a tong operator 206 may be in close proximity to the power tong assembly 200, such as particularly when making-up and breaking-out connections. For example, a power tong 208 of the power tong assembly 200 includes a make-up setting and a break-out setting, with the power tong 208 switchable between the make-up and break-out settings. In the make-up setting, the power tong 208 is used to rotate the upper tubular segment 202A in the first direction to make-up a threaded connection between the upper tubular segment 202A and the lower tubular segment 202B, and in the break-out setting, the power tong 208 is used to rotate the upper tubular segment 202A in the second direction to break-out the threaded connection between the upper tubular segment 202A and the lower tubular segment 202B. Furthermore, the power tong 208 may include a high-speed setting and a low-speed setting, with the power tong 208 switchable between the high-speed and low-speed settings. In the high-speed setting, the power tong 208 is used to rotate the upper tubular segment 202A in the first direction or in the second direction in a high gear. In the low-speed setting, the power tong 208 is used to rotate the upper tubular segment 202A in the first direction or in the second direction in a low gear. Accordingly, the tong operator 206 may operate and switch the power tong 206 between each of these different settings.

FIG. 2B shows an example of the power tong 208 when in the make-up setting, in which the power tong 208 is used in this embodiment to rotate the tubular segment 202A in a first direction (e.g., clockwise direction) when making-up threaded connections with the tubular segment 202A. As the power tong 208 rotates the tubular segment 202A in the clockwise direction, the power tong 208 will have the tendency to move and rotate from a reactive torque 210A in the counter-clockwise direction. In one or more embodiments, to prevent movement and rotation of the power tong 208, a snub line 212A may be attached to the power tong 208 in a direction opposite to the reactive torque 210A to prevent movement of the power tong 208 in response to the reactive torque 210A. As such, the snub line 212A may be used in the orientation shown to prevent rotation of the power tong 208 when making-up threaded connections with the tubular segment 202A.

Similarly, FIG. 2C shows an example of the power tong 208 when in the break-out setting, in which the power tong 208 is used in this embodiment to rotate the tubular segment 202A in a second direction (e.g., counter-clockwise direction) when breaking-out threaded connections with the tubular segment 202A. As the power tong 208 rotates the tubular segment 202A in the counter-clockwise direction, the power tong 208 will have the tendency to move and rotate from a reactive torque 210B in the clockwise direction as well. In one or more embodiments, to prevent movement and rotation of the power tong 208, a snub line 212B may be attached to the power tong 208 in a direction opposite to the reactive torque 210A. As such, the snub line 212B may be used to prevent rotation of the power tong 208 when breaking-out threaded connections with the tubular segment 202A.

As shown in FIGS. 2B and 2C, the direction of the attachment of the snub line 212 to the power tong 208 depends on if the power tong 208 is in the make-up setting or the break-out setting. However, as the power tong 208 may not include an integral backup wrench, and is shown to only include the rotary 204 to hold reaction torque, the power tong 208 may present a risk to the tong operator 206. In particular, in the embodiment shown in FIG. 2B, if the tong operator 206 switches the power tong 208 to operate in the break-out setting instead of the make-up setting, the snub line 212A will be ineffective in preventing rotation of the power tong 208. This will allow the power tong 208 to rotate and spin around the tubular segment 202A in the clockwise direction and strike the tong operator 206. This inefficiency is even further magnified if the tong operator 206 is operating the power tong 208 in the high-speed setting, as opposed to the low-speed setting. Similarly, in the embodiment shown in FIG. 2C, if the tong operator 206 switches the power tong 208 to operate in the make-up setting instead of the break-out setting, the snub line 212B will be ineffective in preventing rotation of the power tong 208. This will allow the power tong 208 to rotate and spin around the tubular segment 202A in the counter-clockwise direction and strike the tong operator 206.

Though not shown, the tong operator 206 often operates the power tong 208 from scaffolding or within confined spaces, in which the power tong 208 may then knock the tong operator 206 from the scaffolding and/or smash the tong operator 206 against the structure of a drilling rig, both of which are life-threatening injuries to the tong operator 206. Accordingly, the present disclosure relates to a power tong assembly, in which the power tong assembly includes a power tong and includes an interlock system operably coupled to the power tong, in which the interlock system is configured to selectively allow the power tong to rotate the tubular segment in one of the first direction and the second direction while preventing the power tong to rotate the tubular segment in the other of the first direction and the second direction.

As discussed above, the power tong 208 includes a make-up setting and a break-out setting, which may be operated through one or more handles or levers included with the power tong 208. The make-up setting enables the power tong 208 to rotate the tubular segment 202A in the first direction to make-up a threaded connection with the tubular segment 202A, and the break-out setting enables the power tong 208 to rotate the tubular segment 202A in the second direction to break-out the threaded connection with the tubular segment 202A.

Accordingly, an interlock system in accordance with the present disclosure that is operably coupled to the power tong 208 also includes a make-up setting and a break-out setting, in which the interlock system may be operated using a selector mechanism included within the interlock system. The make-up setting of the interlock system allows the power tong 208 to rotate the tubular segment 202A in the first direction, such as in both the high-speed setting and the low-speed setting, to make-up the threaded connection with the tubular segment 202A, and the break-out setting of the interlock system allows the power tong 208 to rotate the tubular segment 202A in the second direction, such as in both the high-speed setting and the low-speed setting, to break-out the threaded connection with the tubular segment 202A. FIG. 3A shows a flow chart of operation of a power tong assembly in accordance with the present disclosure. As shown, the interlock system may be set in either an interlock system make-up setting 302A or an interlock system break-out setting 302B. When in the interlock system make-up setting 302A, the power tong is enabled/allowed to operate in a power tong make-up setting 304A and is disabled/prevented to operate in a power tong break-out setting 304B. When in the interlock system break-out setting 302B, the power tong is disabled/prevented to operate in a power tong make-up setting 304C and is enabled/allowed to operate in a power tong break-out setting 304D.

As such, with reference to FIGS. 2A-2C, the interlock system is configured to prevent the power tong 208 to operate in the make-up setting when the interlock system is in the break-out setting, and further is configured to prevent the power tong 208 to operate in the break-out setting when the interlock system is in the make-up setting. Such a configuration may provide an additional safety feature to the power tong assembly 200, thereby helping prevent the tong operator 206 from unintentionally making-up and/or breaking-out of threaded connections that may lead to accidents within a drilling environment.

Further, as also discussed above, the power tong 208 may include a high-speed setting and a low-speed setting, which may be operated through one or more handles or levers included with the power tong 208. The high-speed setting enables the power tong 208 to rotate the tubular segment 202A in the first direction and/or the second direction in a high gear, and the low-speed setting enables the power tong 208 to rotate the tubular segment 202A in the first direction and/or the second direction in a low gear.

Accordingly, an interlock system in accordance with the present disclosure may be configured to allow the power tong 208 to operate in the make-up setting and the high-speed setting only when the interlock system is in the make-up setting, and may further be configured to allow the power tong 208 to operate in the break-out setting and the high-speed setting only when the interlock system is in the break-out setting.

FIG. 3B shows a flow chart of operation of a power tong assembly with an interlock system in a make-up setting in accordance with the present disclosure. The interlock system may be set in an interlock system make-up setting 306A, and the power tong may be set in either a power tong high-speed setting 308A or a power tong low-speed setting 308B. When in the interlock system make-up setting 306A and the power tong high-speed setting 308A, the power tong is enabled/allowed to operate in a power tong make-up setting 310A and is disabled/prevented to operate in a power tong break-out setting 310B. When in the interlock system make-up setting 306A and the power tong low-speed setting 308B, the power tong is enabled/allowed to operate in a power tong make-up setting 310C and is also enabled/allowed to operate in a power tong break-out setting 310D.

Further, FIG. 3C shows a flow chart of operation of a power tong assembly with an interlock system in a break-out setting in accordance with the present disclosure. The interlock system may be set in an interlock system break-out setting 306B, and the power tong may be set in either a power tong high-speed setting 308C or a power tong low-speed setting 308D. When in the interlock system break-out setting 306B and the power tong high-speed setting 308C, the power tong is disabled/prevented to operate in a power tong make-up setting 310E and is enabled/allowed to operate in a power tong break-out setting 310F. When in the interlock system break-out setting 306B and the power tong low-speed setting 308D, the power tong is enabled/allowed to operate in a power tong make-up setting 310G and is also enabled/allowed to operate in a power tong break-out setting 310H.

FIG. 3D shows a flow chart of operation of a power tong assembly in accordance with the present disclosure. In one or more embodiments, the interlock system may include a selector mechanism 312, in which the selector mechanism 312 may be used as a tong operator interface to switch and move the interlock system between operating the power tong in a make-up direction 314 or a break-out direction 316. Further, the interlock system may include a power tong gear position sensor 318. The power tong gear position sensor 318 may be used to sense and determine if the power tong is configured to operate in high gear (e.g., a high-speed setting) or operate in low gear (e.g., a low-speed setting). If the selector mechanism 312 is in the make-up setting (e.g., a make-up position) and the power tong gear sensor 318 detects that the power tong is in high gear, the interlock system may permit the power tong to operate in the make-up direction in high gear 320A and prevent or block the power tong to operate in the break-out direction in high gear 320B. If the selector mechanism 312 is in the make-up setting and the power tong gear sensor 318 detects that the power tong is in low gear, the interlock system may permit the power tong to operate in the make-up direction in low gear 320C and permit the power tong to operate in the break-out direction in high gear 320D.

Further, If the selector mechanism 312 is in the break-out setting (e.g., a break-out position) and the power tong gear sensor 318 detects that the power tong is in high gear, the interlock system may prevent or block the power tong to operate in the make-up direction in high gear 320E and permit the power tong to operate in the break-out direction in high gear 320F. If the selector mechanism 312 is in the break-out setting and the power tong gear sensor 318 detects that the power tong is in low gear, the interlock system may permit the power tong to operate in the make-up direction in low gear 320G and permit the power tong to operate in the break-out direction in high gear 320H.

An interlock system in accordance with the present disclosure may have one or more different types of configurations. For example, as shown and discussed below, the interlock system may be hydraulically controlled, in which the interlock system may include one or more hydraulic components and/or actuators and may be used to selectively control hydraulic fluid flow through the power tong. In particular, the interlock system may be used to selectively provide and control a supply of hydraulic fluid to a hydraulic motor of the power tong. However, in another embodiment, the interlock system may additionally or alternatively be magnetically controlled, electrically controlled, mechanically controlled, and/or pneumatically controlled. Accordingly, the present disclosure contemplates other methods and configurations for an interlock system than only those discussed herein, and therefore the present disclosure should not be so limited.

Referring now to FIGS. 4A-4G, multiple views of a power tong assembly 400 in accordance with one or more embodiments of the present disclosure are shown. The power tong assembly 400 includes a power tong 402 used for gripping and rotating tubular segments, particularly for making-up and breaking-out threaded connections, and also includes an interlock system 410. The interlock system 410 is operably coupled to the power tong 402 to selectively allow the power tong to rotate the tubular segment in one of the make-up and the break-out direction while also preventing the power tong 402 from rotating the tubular segment in the other of the make-up and the break-out direction. Accordingly, in this embodiment, the interlock system 410, or at least portions or components thereof, are positioned upon and operably coupled to a motor 404 of the power tong 402. The motor 404 may be a bi-directional hydraulic motor, in which the interlock system 410 may be used to disable the motor 404, such as by limiting hydraulic fluid supply to the motor 404, to prevent the power tong 402 from rotating the tubular segment in an undesired direction or at an undesired speed.

Along with the motor 404, the power tong 402 may include one or more handles 406 to set the power tong 402 in the make-up setting or the break-out setting. For example, in FIG. 4A, one of the handles 406 may be moved to set the power tong 402 in either the make-up setting or the break-out setting, while the other of the handles 406 may be moved to operate a lift cylinder operably coupled to the power tong 402 to selectively raise and lower the power tong 402. The power tong 402 may further include a handle 408 (e.g., speed shifting shaft) to set the power tong 402 in the high-speed setting or the low-speed setting. For example, in FIG. 4A, the handle 408 may be moved in one direction to set the power tong 402 in the high-speed setting or may be moved in another direction to set the power tong 402 in the low-speed setting.

As the interlock system 410 may include multiple portions or components, the interlock system 410 is shown in this embodiment as including a manifold 412, which may be formed as one or more housings, and a speed detection mechanism 414 (e.g., power tong gear position sensor 318). FIG. 4B shows a detailed view of the manifold 412, and FIG. 4C shows a detailed view of the speed detection mechanism 414. The manifold 412 may be positioned on the motor 404 of the power tong 402 and may have hydraulic fluid pumped through the manifold 412. As such, the manifold 412 may include hydraulic logic elements to selectively divert hydraulic fluid flow therethrough, such as including one or more valves, plugs, and/or switches to selectively divert the flow through the manifold 412. In particular, in this embodiment, the manifold 412 may include therewith or therein a selector mechanism 416, a check valve, an orifice or a needle valve, and an unloader valve.

The selector mechanism 416 may be included within the interlock system 410, and may be used as a tong operator interface to switch and move the interlock system 410 between the make-up setting and the break-out setting. Examples of the selector mechanism 416 are shown in FIGS. 4D-4F. In FIGS. 4D and 4E, the selector mechanism 416 is shown as a plug assembly 418 that includes one or more plugs. The plugs of the plug assembly 418 may be rearranged and positioned within the manifold 412 to set the interlock system 410 in a make-up setting (e.g., high-speed make-up setting), as shown in FIG. 4D, or to set the interlock system 410 in a break-out setting (e.g., high-speed break-out setting), as shown in FIG. 4E. Alternatively, the selector mechanism 416 is shown as a three-way valve 420 in FIG. 4F, such as a three-way ball valve, in which the three-way valve 420 may be set and moved between the make-up setting and the break-out setting.

The speed detection mechanism 414 may be operably coupled to the handle 408 that shifts the power tong 402 between the high-speed setting and the low-speed setting. Accordingly, the speed detection mechanism 414 may be positioned adjacent the handle 408, such as positioned on the bottom of the power tong 402. In this embodiment, the speed detection mechanism 414 may include a cam-operated valve 422. FIG. 4G shows a cross-sectional view of the cam-operated valve 422. As such, the cam-operated valve 422 is activated and moved between an open position and a closed position based on movement of a camming rod 424. The camming rod 424 may be coupled to the handle 408, and therefore the camming rod 424 may move with the handle 408 when shifting the power tong 402 between the high-speed setting and the low-speed setting. Accordingly, the cam-operated valve 422 may detect the speed of the power tong 402, such as if the power tong 402 is in the high-speed setting or the low-speed setting, based upon the position and movement of the camming rod 424.

Referring now to FIGS. 5A and 5B, multiple schematic views of a simplified hydraulic circuit 500 for a power tong assembly in accordance with one or more embodiments of the present disclosure are shown. As shown in this embodiment, the hydraulic circuit 500 includes a hydraulic motor 502 (e.g., bi-directional hydraulic motor), such as the motor 404 shown in FIG. 4A, and a directional control valve 504 (e.g., four-way, three-position directional control valve) that controls fluid flow to the hydraulic motor 502. The directional control valve 504 may include or be operably coupled to the handles 406 of the power tong 402. As such, the directional control valve 504 may be used to control the direction of rotation of the hydraulic motor 502, and therefore may be used to move the power tong 402 between the make-up setting and the break-out setting. Hydraulic fluid may be provided along a pressure flow path 550 and flow through a motor inlet flow path 552 into the directional control valve 504. The directional control valve 504 may then be used to selectively flow the hydraulic fluid into either the A-side or the B-side of the hydraulic motor 502, depending on the desired rotation of the power tong 402. Hydraulic fluid may then return from the hydraulic motor 502 back into the directional control valve 504, in which hydraulic fluid may then be provided to a return flow path 556 through a motor outlet flow path 554.

The hydraulic circuit 500 may further include a bypass flow path 558, in which the bypass flow path 558 may be used to directly route hydraulic fluid from the pressure flow path 550 to the motor outlet flow path 554 and/or directly to the return flow path 556. The bypass flow path 558 may include a directional control valve 560 (e.g., two-way, two-position directional control valve) fluidly coupled thereto, in which the directional control valve 560 may include a pilot-operated valve and/or a cartridge valve. As shown in FIGS. 5A and 5B, the directional control valve 560 may be pilot-operated into the closed position, in which the directional control valve 560 may be opened when pilot pressure to the directional control valve 560 is relieved along a case drain flow path 562. When the control valve 560 opens, hydraulic fluid flows along the bypass flow path 558 instead of the motor inlet flow path 552, thereby disabling and preventing the hydraulic motor 502 from operation.

The directional control valve 560, as shown in the embodiment in FIGS. 5A and 5B, may be opened from operation of either a directional control valve 564 or a directional control valve 566 fluidly coupled in parallel to the directional control valve 560 along the case drain flow path 562. The directional control valve 564 (e.g., two-way, two-position directional control valve) may include an interlock valve that is movable between the open and closed position based upon an open or closed position of a door of the power tong 402. If the door of the power tong 402 is opened, the directional control valve 564 may relieve pilot pressure to the directional control valve 560 along the case drain flow path 562, thereby opening the directional control valve 560 and preventing operation of the hydraulic motor 502.

Further, the directional control valve 566 (e.g., two-way, two-position directional control valve), which may include an unloader valve as shown in FIGS. 5A and 5B, may be movable between the open and closed position based upon a pilot pressure received along a pilot flow path 568. If pilot pressure is received along the pilot flow path 568 to the directional control valve 566, the directional control valve 566 will open, thereby relieving pilot pressure to the directional control valve 560 along the case drain flow path 562, opening the directional control valve 560, and preventing operation of the hydraulic motor 502. Otherwise, if enough pilot pressure is not received along the pilot flow path 568 to open the directional control valve 566, pilot pressure will be maintained to keep the directional control valve 560 closed and the hydraulic motor 502 operational.

Referring still to FIGS. 5A and 5B, the hydraulic circuit 500 includes a direction detection portion or a selector mechanism 570, such as the selector mechanism 416 of the interlock system 410 shown in FIGS. 4A-4G, that may be used to selectively fluidly couple an A-side motor flow path 572A or a B-side motor flow path 572B to a pilot flow path 574. As discussed above, the selector mechanism 570 may be used to switch and move the interlock system 410 between the make-up setting and the break-out setting. The direction detection portion or selector mechanism 570 shown in FIG. 5A is a schematic symbol for the plug assembly 418 shown in FIGS. 4D and 4E, and the direction detection portion or selector mechanism 570 shown in FIG. 5B is a schematic symbol for the three-way valve 420 shown in FIG. 4F.

The hydraulic circuit 500 may further include a directional control valve 576 (e.g., three-way, two-position directional control valve), which may be the cam-operated valve 422 of the speed detection mechanism 414 shown in FIGS. 4A, 4C, and 4G. The directional control valve 576 may be movable between the open and closed position based upon if the power tong 402 is in the high-speed setting and the low-speed setting. As such, in this embodiment, the directional control valve 576 may be in the open position when the power tong 402 is in the high-speed setting, thereby fluidly coupling the pilot flow path 574 to the pilot flow path 568. Further, as shown in FIGS. 5A and 5B, the directional control valve 576 may be in the closed position when the power tong 402 is in the low-speed setting, thereby preventing fluid from flowing from the pilot flow path 574 to the pilot flow path 568. Furthermore, the hydraulic circuit 500 may include a check valve 578 and an orifice or a needle valve 580. The check valve 578 and the needle valve 580 may be in parallel with each other, as shown, and may be fluidly coupled to the pilot flow path 574 or the pilot flow path 568.

In operation, the selector mechanism 570 may be used to either allow fluid flow through the A-side motor flow path 572A or the B-side motor flow path 572B and into the pilot flow path 574. When the A-side motor flow path 572A is open with fluid allowed to flow therethrough, the A-side of the hydraulic motor 502 is not operational. For example, hydraulic fluid may be provided along the motor inlet flow path 552, into the directional control valve 504, and towards the A-side of the hydraulic motor 502. As the A-side motor flow path 572A is open, hydraulic fluid will flow into the A-side motor flow path 572A and continue along the pilot flow path 574. If the directional control valve 576 is present and open (e.g., the power tong 402 is in the high-speed setting), hydraulic fluid may flow from the pilot flow path 574 to the pilot flow path 568 to provide pilot pressure to the directional control valve 566. When pilot pressure is received along the pilot flow path 568 to the directional control valve 566, the directional control valve 566 will open, thereby relieving pilot pressure to the directional control valve 560 along the case drain flow path 562, opening the directional control valve 560, and preventing operation of the hydraulic motor 502.

Similarly, when the B-side motor flow path 572B is open with fluid allowed to flow therethrough, the B-side of the hydraulic motor 502 is not operational. For example, hydraulic fluid may be provided along the motor inlet flow path 552, into the directional control valve 504, and towards the B-side of the hydraulic motor 502. As the B-side motor flow path 572B is open, hydraulic fluid will flow along the B-side motor flow path 572B and continue along the pilot flow path 574. The hydraulic fluid may then flow from the pilot flow path 574 to the pilot flow path 568 to provide pilot pressure to the directional control valve 566.

In an embodiment in which hydraulic fluid received through the A-side of the hydraulic motor 502 causes the power tong 402 to make-up threaded connections with a tubular segment, the right side of the directional control valve 504 may be used as the make-up setting for the power tong 402, and the opening the B-side motor flow path 572B may be used as the make-up setting for the selector mechanism 570 (e.g., selector mechanism 416). In such an embodiment, the hydraulic motor 570 may, thus, be disabled when the directional control valve 504 is switched to the left side for the break-out setting of the power tong 402, thereby disabling and preventing the hydraulic motor 570, and the power tong 402, from operating in the break-out setting when the interlock system 410 is in the make-up setting.

Similarly, in an embodiment in which hydraulic fluid received through the B-side of the hydraulic motor 502 causes the power tong 402 to break-out threaded connections with a tubular segment, the left side of the directional control valve 504 may be used as the break-out setting for the power tong 402, and the opening the A-side motor flow path 572A may be used as the break-out setting for the selector mechanism 570 (e.g., selector mechanism 416). In such an embodiment, the hydraulic motor 570 may, thus, be disabled when the directional control valve 504 is switched to the right side for the make-up setting of the power tong 402, thereby disabling and preventing the hydraulic motor 570, and the power tong 402, from operating in the make-up setting when the interlock system 410 is in the break-out setting.

As shown and discussed above, the interlock system 410 may include a manifold 412, in which the manifold 412 may include hydraulic logic elements to selectively divert hydraulic fluid flow therethrough. Accordingly, as shown in FIGS. 5A and 5B, the manifold 412 may include the selector mechanism 570, the directional control valve 566, the check valve 578, and the orifice or needle valve 580. The check valve 578 and the orifice or needle valve 580 may be used to maintain pressure on the directional control valve 566 through the pilot flow path 574, the directional control valve 576, and the pilot flow path 568. The check valve 574 enables hydraulic fluid to pass across and enter into the pilot flow path 568 and open the directional control valve 566 (e.g., enter a pilot cavity of the unloader valve). The orifice or needle valve 580 may enable the pressure from the hydraulic fluid to then be maintained within the pilot flow path 568 and upon the directional control valve 566 (e.g., maintain pressure within the pilot cavity of the unloader valve) by slowing and regulating the flow of hydraulic fluid away from the pilot flow path 568.

Further, as discussed above, the directional control valve 566 (e.g., unloader valve) may be used as a disabling portion within the interlock system to disable and prevent rotation of the power tong based a speed detection portion (e.g., a directional control valve 576 and/or a cam-operated valve 422) and the direction detection portion (e.g., selector mechanism 570). For example, when pilot pressure is received along the pilot flow path 568 to the directional control valve 566, the directional control valve 566 will open, thereby relieving pilot pressure to the directional control valve 560 along the case drain flow path 562. This enables the directional control valve 560 to open, in which hydraulic fluid then flows along the bypass flow path 558 instead of the motor inlet flow path 552, thereby disabling and preventing the hydraulic motor 502 from operation.

Accordingly, a power tong assembly including a power tong and an interlock system in accordance with the present disclosure may include one or more advantages, such as by decreasing the likelihood of an accident when operating a power tong. In particular, the interlock system is configured to selectively allow the power tong to rotate the tubular segment in one of the first direction and the second direction while preventing the power tong to rotate the tubular segment in the other of the first direction and the second direction. As such, the interlock system may be used to prevent the power tong from operating in a direction unintended by a tong operator, thereby preventing damage to the power tong, to the tubular segments handled by the power tong, and the tong operator.

Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.

This is a continuation of application Ser. No. 13/367,305, filed Feb. 6, 2012, now U.S. Pat. No. 8,863,621, which is a continuation-in-part of application Ser. No. 12/379,090, filed Feb. 12, 2009, now U.S. Pat. No. 8,109,179, which claims the benefit of U.S. Provisional Application No. 61/071,170, filed Apr. 16, 2008 and U.S. Provisional Application No. 61/064,032, filed Feb. 12, 2008.

This invention relates to the field of devices for rotating tubular members so as to make up or break out threaded joints between tubulars including casing, drill pipe, drill collars and tubing (herein referred to collectively as pipe or tubulars), and in particular to a power tong for the improved handling and efficient automation of such activity.

In applicant"s experience, on conventional rotary rigs, helpers, otherwise known as roughnecks, handle the lower end of the pipe when they are tripping it in or out of the hole. As used herein, the terms pipe and tubular are used interchangeably. The roughnecks also use large wrenches commonly referred to as tongs to screw or unscrew, that is make up or break out pipe. Applicant is aware that there are some other tongs that are so called power tongs, torque wrenches, or iron roughnecks which replace the conventional tongs. The use of prior art conventional tongs is illustrated in FIG. 1a. Other tongs are described in the following prior art descriptions.

In the prior art applicant is aware of U.S. Pat. No. 6,082,225 which issued Feb. 17, 1997 to Richardson for a Power Tong Wrench. Richardson describes a power tong wrench having an open slot to accommodate a range of pipe diameters capable of making and breaking pipe threads and spinning in or out the threads and in which hydraulic power is supplied with a pump disposed within a rotary assembly. The pump is powered through a non-mechanical coupling, taught to be a motor disposed outside the rotary assembly.

In the present invention the rotary hydraulic and electrical systems are powered at all times and in all rotary positions via a serpentine such as a serpentine belt drive, unlike in the Richardson patent in which they are powered only in the home position. In the present invention the pipe can thus be gripped and ungripped repeatedly in any rotary position with no dependence on stored energy and the tong according to the present invention may be more compact because of reduced hydraulic accumulator requirements for energy storage wherein hydraulic accumulators are used for energy storage only to enhance gripping speed.

Applicant is also aware of U.S. Pat. No. 5,167,173 which issued Dec. 1, 1992 to Pietras for a Tong. Pietras describes that tongs are used in the drilling industry for gripping and rotating pipes, Pietras stating that generally pipes are gripped between one or more passive jaws and one or more active jaws which are urged against the pipe. He states that normally the radial position of the jaws is fixed and consequently these jaws and/or their jaw holders must be changed to accommodate pipes of different diameters.

Applicant is also aware of U.S. Pat. No. 6,776,070 which issued Aug. 17, 2004 to Mason et al. for an Iron Roughneck. Mason et al. describes an iron roughneck as including a pair of upper jaws carrying pipe gripping dies for gripping tool joints where the jaws have recesses formed on each side of the pipe gripping dies to receive spinning rollers. By positioning the spinning rollers in the upper jaws at the same level as the pipe gripping dies the spinning rollers are able to engage the pipe closer to the lower jaws and thus can act on the tool joint rather than on the pipe stem. Mason et al. describe that in running a string of drill pipe or other pipe into or out of a well, a combination torque wrench and spinning wrench are often used, referred to as “iron roughnecks”. These devices combine torque and spinning wrenches as for example described in U.S. Pat. Nos. 4,023,449, 4,348,920, and 4,765,401, to Boyadjieff.

In the prior art iron roughnecks, spinning wrenches and torque wrenches are commonly mounted together on a single carriage but are, nevertheless, separate machines with the exception of the Iron Roughnecks of Mason which combines the spinner wrench rollers and torque jaws in a common holder, although they nevertheless, still work independently of each other. When breaking-out, or loosening, connections between two joints of drill pipe, the upper jaw of the torque wrench is used to clamp onto the end portion of an upper joint of pipe, and the lower jaw of the torque wrench clamps onto the end portion of the lower joint of pipe.

Drill pipe manufacturers add threaded components, called “tool joints”, to each end of a joint of drill pipe. They add the threaded tool joints because the metal wall of drill pipe is not thick enough for threads to be cut into them. The tool joints are welded over the end portions of the drill pipe and give the pipe a characteristic bulge at each end. One tool joint, having female, or inside threads, is called a “box”. The tool joint on the other end has male, or outside threads, and is called the “pin”. Disconnection of the pin from the box requires both a high-torque and low angular displacement ‘break’ action to disengage the contact shoulders and a low-torque high-angular displacement ‘spin’ action to screw out the threads. Connection of the pin and box require the reverse sequence. In the make/break action torque is high (10,000-100,000 ft-lb), having a small (30-60 degrees) angular displacement. In the spin action torque is low (1,000-3,000 ft-lb), having a large (3-5 revolutions) angular displacement.

After clamping onto the tool joints, the upper and lower jaws are turned relative to each other to break the connection between the upper and lower tool joints. The upper jaw is then released while the lower jaw (also referred to as a back-up jaw) remains clamped onto the lower tool joint. A spinning wrench, which is commonly separate from the torque wrench and mounted higher up on the carriage, engages the stem of the upper joint of drill pipe and spins the upper joint of drill pipe until it is disconnected from the lower joint. When making up (connecting) two joints of pipe the lower jaw grips the lower tool joint, the upper pipe is brought into position, the spinning wrench (or in some cases a top drive) engages the upper joint and spins it in. The torque wrench upper jaws clamp the pipe and tightens the connection.

Applicant is further aware of United States Published patent application entitled Power Tong, which was published Apr. 5, 2007 under Publication No. US 2007/0074606 for the application of Halse. Halse discloses a power tong which includes a drive ring and at least one clamping device with the clamping devices arranged to grip a pipe string. A driving mechanism is provided for rotation of the clamping device about the longitudinal axis of the pipe string. The clamping device communicates with a fluid supply via a swivel ring that encircles the drive ring of the driving mechanism. Thus Halse provides for three hundred sixty degree continuous rotation combining a spinner with a torque tong. The Halse power tong does not include a radial opening, the tong having a swivel coupling surrounding the tong for transferring pressurized fluid from an external source to the tong when the tong rotates about the axis of the pipe. Halse states that having a radial opening in a power tong complicates the design of the power tong and weakens the structure surrounding the pipe considerably, stating that as a result, the structure must be up-rated in order to accommodate the relatively large forces being transferred between the power tong and the pipe string. Halse further opines that a relatively complicated mechanical device is required to close the radial opening when the power tong is in use, and in many cases also to transfer forces between the sides of the opening. The Halse tong is not desirable for drilling operations because there is no throat opening to allow the tong to be positioned around the pipe at the operator"s discretion. The pipe must always pass through the tong.

The power tong according to the present invention continuously rotates tubulars for spinning and torquing threaded connections. Continuous rotation is achieved through a rotating jaw (also referred to as a rotor) that has grippers that grip the tubular. Hydraulic and electrical power necessary for actuating the grippers is generated on board the rotor since the continuous rotation does not allow for either hydraulic or electrical external connections. A serpentine member such as a serpentine drive belt system turns the motors of an on-board hydraulic power unit and electric generators which may be AC or DC generators, to supply the grippers with the necessary hydraulic and electrical power.

The present invention includes a rotor rotably mounted in or on a rigid structural framework or stator frame. A main drive drives the rotor. The rotor may be supported and held in position by the use of opposed helical pinions/gears which support the rotor vertically and guide bushings which locate it laterally and support it vertically when the torque is low. The grippers, which may be actuated by hydraulic gripper cylinders, maybe held in position by links and guide bushings that can withstand the torque parameters of the tong. The gripper cylinders may be moved in a range of travel by an eccentric. This provides for a tong that can accommodate a large range of pipe diameters (3.5 inch drillpipe to 9-⅝ inch casing or larger). A centralizing linkage ensures that the pipe is gripped concentricly with the tong axis of rotation. The tong does not require a mechanical device to close the radial opening. The on-board power source and rotary control system allow the present invention to have fully independently activated and controlled rotary gripping of the tubular. It is capable of high torque for making and breaking and high speed for spinning, all within one mechanism. One embodiment of the present invention also overcomes the limitation of the spinning wrench engaging the stem area of the drillpipe which over time will cause fatigue in the stem area as the spinning and torquing according to the present invention is accomplished with the same jaw that engages the pipe on the tool joint. The throat of the jaws according to the present invention has an opening of sufficient diameter to accept a tubular. The throat cooperates with the opening to allow the power tong to be selectively positioned around the pipe at the operators" discretion.

FIG. 16 is, in cross sectional view along the axis of rotation of the tubular, the mated tool joints of FIG. 15, with the tool joints un-threaded from one another.

FIGS. 18 and 19 are in diagrammatic plan view, a further exemplary embodiment of the nested transmission of the tong, showing the use, by way of example, of two stator sprockets, at least one of which is driven, having a serpentine member therearound and reaved over a pair of rotor sprockets on the throated rotor, the pair of rotor sprockets having a synchronizer therearound, the rotor sprockets driving a coupling mechanism coupling the power transfer from the serpentine member to gripper actuators on the rotor which articulate grippers at the rotor axis of rotation.

FIG. 19ais a partially cut-away section view along line 19 a-19 ain FIG. 19 showing one rotor (satellite) sprocket driving, by way of example, a pump and/or generator part of the power or energy transfer coupling between the serpentine member and the gripper actuators.

As seen in FIGS. 1 and 2, the power tong 6 may include three main sections mounted on a common axis A; namely a main drive section, a rotor, and a back-up jaw. Each of the sections contains actuators, as better described below. The main drive section 10 which provides at least part of a rigid stationary framework or stator frame is located above the rotor 22. The backup jaw 48, located below rotor 22, may also provide part of the stator frame. The rotor 22 rotates relative to the main drive and back-up jaw. Both the rotor and backup jaw clamp their respective sections of pipe. The rotor 22 is rotated by the main drive section 10 independently of the main drive section and backup jaw in the sense that the rotor 22 is self-contained, having on-board hydraulic and electric power generators to power on-board radial clamps or grippers (collectively herein referred to as grippers), and an on-board serpentine secondary power transmission, all configured to allow the insertion and removal of a pipe through a jaw opening from or into the center of the jaw, so that the pipe, when in the center of the jaw may be clamped, torqued, and spun about axis A of rotation of the rotor 22 while the other, oppositely disposed section of pipe is held clamped in the center of the back-up jaw 48.

Main drive section 10 includes primary drives 12, each of which includes rotary drive motors 16, which may for example be hydraulic or electric motors, gear reduction devices 16 a, and belt drives 16 bas better seen in FIG. 2. Motors 16 cooperate with drive pinions 56 to rotate rotor 22 about axis A relative to main drive section 10 and back-up jaw section 24.

As shown in FIGS. 1, 2 and 3 rotor 22 is housed within drive section 10, although this is not intended to be limiting as the rotor may be mounted so as not to be housed within the drive section and still work. The rotor 22 is cylindrical in shape and has an opening slot, which although illustrated as linear may be linear or non-linear, having a throat 38 for passing of a tubular along the slot thereby allowing the tong axis of rotation A to be selectively positioned concentric with pipe 8, provided the rotor 22 is rotated such that its throat 38 is aligned with the front openings 28 and 29 of the main drive section and back-up jaw, respectively. Center 40 of the yoke formed by the jaw and slot corresponds with axis A. The rotary jaw 22 has three gripper cylinders 44 a, 44 b, and 44 carranged radially, with approximately equal angular spacing around axis A, mounted between the two parallel horizontal planes containing rotor gears 30 aand 30 b. The number of gripper actuators, such as gripper cylinders 44 a-44 c, and associated grips or grippers may be more or less in number, so long as a tubular joint may be gripped or clamped at center opening 40.

A serpentine member such as serpentine drive belt 20 is driven by two serpentine drive motors 18, which may for example be hydraulic or electric motors. The serpentine member is mounted around so as to engage stator sprockets mounted on the stator frame. For example the stator sprockets may include drive sprockets 26 awhich are driven by serpentine drive belt 20 to collectively provide a secondary drive powering the grippers on the rotor 22. Drive sprockets 26 arotate serpentine drive belt 20 about idler sprockets 26 mounted to drive section 10. And the serpentine drive belt 20 also engages about rotor sprockets 32 a-32 fmounted on the rotor 22 as better described below. The rotor sprockets 32 aand 32 bmay be two generator drive sprockets. The rotor sprockets 32 cand 32 dmay be two pump drive sprockets. Rotor sprockets 32 eand 32 fmay be two idler sprockets. In the illustrated embodiment, which is not intended to be limiting as other embodiments discussed below would also work, the generator drive sprockets, that is, rotor sprockets 32 aand 32 b, transmit rotary power to generators 34. The pump drive sprockets, that is, rotor sprockets 32 cand 32 d, transmit rotary power to hydraulic pumps 36 by the action of serpentine drive belt 20 engaging the upper groove of rotor sprockets 32 a, 32 b, 32 cand 32 d. A synchronization belt, 28 a, connects the lower portions of the rotor sprockets 32 a-32 f. Thus as the rotor 22 rotates on axis of rotation A, even though serpentine drive belt 20 cannot extend across the throat 38 because such a blockage would restrict selective positioning of the pipe 8 along the slot into the tong, serpentine drive belt 20 wraps in a C-shape around the rotor sprockets 32 a-32 f. Serpentine drive belt 20, driven by drive sprockets 26 a, runs on pulleys 26, and on idler sprockets 26 band 26 cmounted to, so as depend downwardly from, main drive section 10. The extent of the C-shape of serpentine drive belt 20 provides for continual contact between serpentine drive belt 20 and, in this embodiment which is not intended to be limiting, a minimum of three of the rotor sprockets 32 a-32 fas the rotor rotates relative to the main drive section 10. The synchronization belt 28 amounted on the rotor maintains rotation of the individual rotor sprockets as they pass through the serpentine gap 29 seen in FIG. 4, that is, the opening between sprockets 26 band 26 c. Synchronization belt 28 asynchronizes the speed and phase of the rotation of each of the rotor sprockets 32 a-32 fto allow each of them in turn to re-engage the serpentine drive belt 20 after they are rotated across the serpentine gap 29 by the action of the rotor rotating relative to the main drive.

As an example, when rotor 22 rotates in direction B, rotor sprocket 32 cwill reach the serpentine gap 29 and as that sprocket crosses gap 29 it is disengaged from serpentine drive belt 20, during which time rotor sprocket 32 cand its corresponding pump continues to operate as it is driven by synchronization belt 28 arather than the serpentine belt 20. When rotation of rotor 22 continues such that rotor sprocket 32 cpasses further counter-clockwise, for example beyond idler sprocket 26 cduring unscrewing of pipe 8, then rotor sprocket 32 cwill re-engage with serpentine drive belt 20. The process repeats in succession as each of the six rotor sprockets 32 a-32 fpasses across gap 29 between idler sprockets 26 band 26 c.

Idler sprocket 26 cis spring-mounted by means of resiliently biased tensioner arm 26 dto maintain minimum tension in the serpentine drive belt 20 regardless of the rotational position of the rotor 22. This is advantageous as there is a small variation in the length of the path of the serpentine drive belt 20 as the rotor 22 rotates about axis A.

The serpentine drive belt 20 maybe a toothed synchronous drive belt in order to minimize belt tension requirements. The use of a drive belt having teeth (not shown) allows for small sprocket diameters and avoids dependence on friction which could be compromised by fluid contaminants. The serpentine belt may be double-toothed (that is, have teeth on both sides) or may be single-toothed with the teeth facing inward on the inside portion of the C-shaped loop and facing outward on the outer side portion of the C-shaped loop, where the serpentine drive motors 18 and corresponding drive sprockets 26 aare positioned outside the C-shaped loop.

During operation of tong 6 the secondary drive (drive motors 18) and serpentine drive belt 20 run continuously to deliver power to the on-board pumps and generators by means of the rotor sprockets 32 a-32 d. Rotation of the rotor 22 by the operation of the primary drive acting on the pinions 56 and rotor gears 30 aand 30 bdoes not substantially affect the powering of the on-board accessories (pumps and generators) because drive belt 20 is run at substantially an order of magnitude greater speed than the speed of rotation of rotor 22. The rotation of the