Patent Description:
Power tongs are used on drilling rigs to rotate and thereby connect together ("make-up") or disconnect ("break-out") threaded connections between adjacent tubular segments in a tubular string. The tongs typically grip a first tubular segment and rotate it relative to a second tubular segment to either make-up or break-out the connection therebetween. <FIG> is a perspective view of an example of such a power tong <NUM>. The power tong <NUM> includes a drive motor that may be hydraulically-powered (although a variety of other power-sources could be used) and a gripping assembly coupled to the motor <NUM> for gripping and rotating a tubular segment received within a bay <NUM>. A generally "c-shaped" gear housing <NUM> supports a pivoting door <NUM>. The door <NUM> may be closed to secure the bay <NUM> or swung open (as indicated in <FIG>) to provide access to the bay <NUM>. The bay <NUM> is generally surrounded by the housing <NUM>. The center of the bay <NUM> is between a pair of generally opposed, pivotable gripping jaws <NUM>, each having a generally arcuate gripping surface facing radially inward toward the center of the bay <NUM>.

Manufacturer specifications typically call for high torque to properly make-up connections, e.g., on the order of thousands, up to tens of thousands of ft-lbs of torque. The components of a power tong thus are capable of producing and sustaining such high torque loads to rotate tubular segments to full make-up torque. As such, safely and effectively handling tubular members within an oilfield environment is a priority.

The process of making up and running a tubular (e.g., casing or production tubing) string into a wellbore directly impacts the time required to drill and case a well and consequently the cost of completing the casing/tubing running operation. However, the desire for efficiency in the process may be balanced with maintaining safe operating conditions, because tubular running presents several potential hazards. For example, the process of casing running involves operation of several pieces of equipment in concert to perform the steps of the process in a particular sequence. If the sequence is altered, which is a risk given the repetitive nature of the process, damage to equipment and/or injuries to rig personnel may occur.

As a brief overview, the casing running process may begin by bringing an add-on joint of casing from a horizontal orientation on pipe racks next to the rig floor to a vertical orientation above well center. The process may then include joining threads of the add-on casing joint to the top-most casing joint of the casing string that extends into the well (e.g., meshing helical threads of the joints together by rotating one joint relative to the other). The add-on joint, now forming part of the casing string, is then lowered into the wellbore, and then temporarily gripped and supported at the rig floor. The process then repeats, potentially several hundred times, depending on the length of the casing string.

Each piece of equipment is typically operated by a separate person. Moreover, the steps are carried out in parallel, over a period of time that can range from four to <NUM> or more hours, depending on the length of the casing string and wellbore conditions. With so many repetitive activities taking place, and each relying on the close coordination of several individuals, there are opportunities for human error that can result in serious personal injury.

Further, issues with connecting together the joints arise, such as cross-threading. Typical casing and production tubing threaded connections are tapered, meaning the male threaded connection resembles a shallow tapered cone and the female threaded connection is also conical in shape to match the male threaded connection. Alignment of the male connection on the end of an add-on joint of tubular with the mating female connection takes place with a full length of add-on casing hanging vertically in the derrick. Any bend in the add-on joint of casing or lateral misalignment between the add-on joint and the female threaded connection at the top of the string can result in cross-threading of the male threaded connection relative to the female connection. Cross-threading is identified when the tong operator attempts to rotate the add-on joint, as a cross-threaded joint resists rotation immediately. By contrast, a properly threaded joint rotates several revolutions with ease until the conical male threaded connection approaches full make-up into the female threaded connection.

Once a cross-threaded connection is identified, the remedy is to back the add-on joint out in order to reposition the joint into proper alignment with the female threaded connection. Backing-out takes place by reversing the direction of operation of the power tong. Initially this involves rotating the gripping elements of the power tong to establish a grip between the power tong jaws and the add-on tubular in the opposite (back-out) direction. Once the grip is established in the back out direction, the power tong rotates the add-on joint in a break-out direction (e.g., counterclockwise) to free the male connection of the add-on joint from the female connection at the top of the string.

As shown in <FIG>, reversing the power tong <NUM> from a make-up direction to a break-out direction of operation involves repositioning of the power tong <NUM> and an associated snub line <NUM>. The snub line <NUM> secures the tong <NUM> against rotation in at least one direction, e.g., counterclockwise, which prevents movement of the tong <NUM> during make-up operations. When the tong <NUM> is reversed, e.g., to break-out a cross-threaded connection, care must be taken to avoid injury to an operator <NUM> caused by the tong <NUM> quickly reversing rotation, since the snub line <NUM> may not prevent rotation of the tong <NUM> toward the operator <NUM>. If the reversal and repositioning of the tong <NUM> is done with haste and the power tong <NUM> is not properly secured against rotation when attempting to back-out the add-on joint, the power tong <NUM> can rotate towards the operator <NUM>, and may strike the operator <NUM>, potentially severely injuring the operator <NUM>.

<CIT>) discloses a power tong assembly including a power tong and an interlock system operably coupled to the power tong.

<CIT>) discloses a power tong assembly including a power tong and a speed limiting system operably coupled to the power tong.

<CIT>) discloses a power tong for well pipe, in which a jaw carrying ring is rotatable in opposite directions by a rotatable jaw actuating cam ring.

<CIT>) discloses an automated electric tong system and methods usable for making-up and breaking out threaded connections between tubular members.

Embodiments of the present disclosure may provide a control system for a tong for a drilling rig. The control system includes a tong motor control valve that is selectively actuatable to cause rotation of the tong in a first direction or in a second direction, a run/pull mode selector configured to actuate between a first configuration for running tubulars into a well and a second configuration for pulling tubulars from the well, a rotation speed selector configured to actuate between a high-speed setting configured to cause the tong to be driven to rotate at a first speed, and a low-speed setting configured to cause the tong to be driven to rotate at a second speed, the first speed being greater than the second speed, and a rotation change control device configured to selectively prevent or permit actuation of the tong motor control valve based on whether the run/pull mode is in the first configuration or the second configuration and whether the rotation speed selector is in the high-speed setting or the low-speed setting.

Embodiments of the disclosure a method for controlling a tong including receiving a signal representing that a run/pull mode selector is in a first configuration associated with running tubulars into a well, and receiving a signal representing that a rotation speed selector is in a high-speed setting. The tong is configured to rotate at a first speed when the rotation speed selector is in the high-speed setting. The method also includes automatically permitting actuation of a tong motor control valve to cause the tong to rotate in a make-up direction, and automatically preventing actuation of the tong motor control valve to cause the tong to rotate in a break-out direction that is opposite to the make-up direction, until receiving a signal representing that the rotation speed selector has been actuated to a low-speed setting. The tong is configured to operate at a second speed that is less than the first speed when the rotation speed selector is in the low-speed setting.

Embodiments of the disclosure may also provide a tong including gripping jaws configured to grip a tubular, a motor configured to rotate the jaws and thereby rotate the tubular in either a make-up direction or a break-out direction, and a control system in communication with the motor. The control system includes a tong motor control valve that is selectively actuatable to cause rotation of the tong in a first direction or in a second direction, a run/pull mode selector configured to actuate between a first configuration for running tubulars into a well and a second configuration for pulling tubulars from the well, a rotation speed selector configured to actuate between a high-speed setting configured to cause the motor to drive the tong to rotate at a first speed, and a low-speed setting configured to cause the motor to drive the tong to rotate at a second speed, the first speed being greater than the second speed, and a rotation change control device configured to selectively prevent or permit actuation of the tong motor control valve based on whether the run/pull mode is in the first configuration or the second configuration and whether the rotation speed selector is in the high-speed setting or the low-speed setting.

The foregoing summary is intended merely to introduce a subset of the features more fully described of the following detailed description. Accordingly, this summary should not be considered limiting.

The accompanying drawing, which is incorporated in and constitutes a part of this specification, illustrates an embodiment of the present teachings and together with the description, serves to explain the principles of the present teachings. In the figures:.

Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawing. In the drawings, like reference numerals have been used throughout to designate identical elements, where convenient. The following description is merely a representative example of such teachings.

<FIG> illustrates a functional block diagram of a control system <NUM> for a tong for a drilling rig, according to an embodiment. The tong may be the tong <NUM> discussed above or any other tong used to rotate one tubular relative to another and thereby connect and/or disconnect the tubulars on a drilling rig. The control system <NUM> may be configured to control either or both of rotation and speed of the tong <NUM> in a manner that automatically prevents uncontrolled movement of the tong housing, which, as mentioned above, presents a hazard to rig personnel and/or equipment if not prevented.

The system <NUM> may include a run/pull mode selector <NUM>, a rotation speed selector <NUM>, a directional control valve <NUM> ("directional" refers to the type of valve, not necessarily rotation direction), a rotation change control device <NUM>, a low-speed indicator device <NUM>, a tong motor control valve <NUM>, and a piston position sensing device <NUM>. These components <NUM>-<NUM> may be configured to control the rotation direction and speed of the tong <NUM>.

In particular, the run/pull mode selector <NUM> may be a switch that is configured to be set in a run or pull mode (referred to herein as "configurations") by a user/operator. The rotation speed selector <NUM> may likewise be a switch and may be configured to receive a high or low-speed setting from a user. The low-speed indicator device <NUM> may be configured to detect when the tong <NUM> is operating in the low-speed setting (e.g., when the rotation speed selector <NUM> is in the low-speed setting, and the tong has implemented the low-speed setting). The directional control valve <NUM> may be configured to control a speed range setting of the rotation of the tong <NUM>, e.g., by interfacing with a gear shift cylinder that controls selection of a gear in a gear box (e.g. high gear and low gear), and thereby implement, if allowed, the speed setting of the rotation speed selector <NUM>.

The tong motor control valve <NUM> may be a lever, joystick, slide, knob, etc. that is actuatable to cause the tong to rotate in a first or "make-up" direction and a second or "break-out" direction. For example, moving the tong motor control valve <NUM> in one direction may cause the tong <NUM> to rotate in the first direction, and moving the tong motor control valve <NUM> in the opposite direction may cause the tong <NUM> to rotate in the second direction. Further, the speed of rotation may be proportional to the degree of movement of the tong motor control valve <NUM> within two ranges, one high speed range, and one low speed range, corresponding to the high and low speed settings received using the speed selector <NUM> and the corresponding high and low gears engagements in the gear box.

The rotation change control device <NUM> may selectively permit or block actuation of the tong motor control valve <NUM> in response to signals provided thereto which are determined in part by control logic. The control logic receives inputs from the selectors <NUM>, <NUM>, along with inputs provided by system condition sensors, e.g., the low-speed indicator device <NUM> and the piston position sensing device <NUM>, both of which interface with the directional control valve <NUM>. The directional control valve <NUM> interfaces with a gear shift cylinder that selectively alters engagement of the gears within the tong <NUM> between high and low speed arrangements.

Accordingly, the system <NUM> may provide an interlock which selectively permits or blocks the tong motor control valve <NUM> causing rotation of the tong <NUM> in one or both rotational directions. For example, actuation of the tong motor control valve <NUM> may be blocked or permitted based at least partially on the configuration of the mode selector <NUM>, the setting of the speed selector <NUM>, and the determination by the low-speed indicator device <NUM>. For example, as will be described in greater detail below, the components <NUM>, <NUM>, <NUM>, and <NUM> may cooperate, e.g., as part of an electrical, pneumatic, or hydraulic circuit, to position blocking devices, e.g., pistons that selectively engage or disengage from a spool of the rotation change control device <NUM>. When engaged, the pistons may block movement of the spool, and when disengaged, the pistons may permit movement of the spool. In turn, actuation of the tong motor control valve <NUM> may be permitted or blocked by permitting or allowing movement of the spool via the pistons.

In an embodiment, the piston position sensing device <NUM> may communicate with the blocking device (pistons) discussed above. The piston position sensing device <NUM> may recognize when the pistons are engaged or disengaged, and contribute to the control of the rotation change control device <NUM> in response, e.g., preventing shifting of the gears from low to high via the gear shift cylinder and the directional control valve <NUM>, as will be described below.

In some embodiments, a user may attempt to cause the tong motor control valve <NUM> to change the direction in which the tong <NUM> rotates. For example, during running operations, the run/pull mode selector <NUM> may be in the run mode when cross-threading is detected. Thus, reversing the direction of rotation to break-out a cross-threaded operation may be desired, e.g., without changing the configuration of the mode selector <NUM> to the pull (as running operations may support backing out cross-threaded connections, for example). The system <NUM> may be configured to permit such rotation reversal, while allowing the tong run/pull mode selector <NUM> to remain in the run mode, but in a safe manner that prevents hazards, such as the tong <NUM> impacting the operator, as described above.

Thus, among other things, the system <NUM> may be configured to automatically prevent rotation of the tong <NUM> in the break-out direction when the tong <NUM> is configured in "run" mode and is in the high-speed setting, only allowing such rotation after actuating the rotation speed selector <NUM> to the low-speed setting, and, e.g., confirming such actuation has been implemented using the low-speed indicator device <NUM>. In some embodiments, the tong <NUM> may likewise be prevented from reversing rotation while in the high-speed setting when in the pull mode. In some embodiments, the piston position sensing device <NUM> may prevent the tong <NUM> from actuating back to the high-speed setting, even upon the rotation speed selector <NUM> being actuated to the high-speed setting, at least until the tong <NUM> has been shifted into a neutral position, in which the tong <NUM> is not driven to rotate. In some embodiments, blocking the speed from changing may only be active when the tong <NUM> is in run mode, as other safety devices may be employed in the pull mode (e.g., the snub line).

With continuing reference to <FIG>, <FIG> illustrates a flowchart of a method <NUM> for controlling a tong (e.g., the tong <NUM>), according to an embodiment. The method <NUM> may be implemented at least in part using the system <NUM>. The method <NUM> may begin by configuring the run/pull mode selector <NUM>, as at <NUM>. As noted above, the run/pull mode selector <NUM> may have a first configuration ("run mode") and a second configuration ("pull mode"). Configuring the run/pull mode selector <NUM> at <NUM> may include moving a switch from a neutral position, for example, or selecting a button, or leaving a switch in a present state, etc..

The method <NUM> may further include selecting a speed setting for the rotation speed selector <NUM>, as at <NUM>. The rotation speed selector <NUM> may have at least two settings, e.g., a low-speed setting and a high-speed setting (in this context, "high" means faster than low-speed, and "low" means slower than high-speed-the two terms are relative to one another and do not generally connote a specific speed). Selecting the setting may include turning a knob, flipping a switch, pushing a button, or keeping a switch in its current position. The high speed may be associated with a high gear, and the low speed may be associated with a low gear, as noted above.

These inputs may configure a circuit that provides input signals to the rotation change control device <NUM>, which in turn allows or blocks movement of the tong motor control valve <NUM>. Based on the configuration of the run/pull mode selector <NUM>, the method <NUM> may include determining the rotation direction configuration, generally referring to the type of operation in which the tong <NUM> is being used ("run" refers to deploying or "running" tubulars into a well, and "pull" refers to extracting or "pulling" tubulars from the well), as at <NUM>. Considering first the run mode, the method <NUM> may determine the rotation speed selector <NUM> setting, as at <NUM>. When the rotation speed selector <NUM> is in the high-speed setting, the method <NUM> may proceed to <NUM>, where the rotation change control device <NUM> may permit the tong motor control valve <NUM> to cause the tong <NUM> to rotate in the make-up direction at the high-speed as at <NUM>, but may prevent the tong motor control valve <NUM> from causing rotation in the break-out direction (opposite to the make-up direction), as at <NUM> while the tong is in high gear. As such, a change in rotation direction without an accompanying change in speed selection may be prevented by preventing actuation of the tong motor control valve <NUM>.

Referring again to block <NUM>, when the rotation speed selector <NUM> is set to low-speed, the method <NUM> may proceed to the rotation change control device <NUM> permitting the tong motor control valve <NUM> to actuate and cause the tong <NUM> to rotate in either the make-up direction, as at <NUM>, or the break-out direction, as at <NUM>. Accordingly, it is seen that the tong motor control valve <NUM> is allowed to change the rotation direction of the tong <NUM> from make-up to break-out when the speed selector <NUM> is in the low-speed setting. Thus, when the speed selector <NUM> is in the high-speed setting, in order to change rotation direction, the speed selector <NUM> may first have to be actuated to the low-speed setting (and, e.g., confirmed by the low-speed indicator device <NUM>). The method <NUM> may be continuous, e.g., implemented using valves in a pneumatic circuit, and thus when the speed selector <NUM> changes setting from the high to low-speed, the method <NUM> may respond by taking the low-speed branch from block <NUM>, and then allowing rotation direction change.

Similarly, referring again to block <NUM>, when the run/pull mode selector <NUM> is in the pull mode, the method <NUM> may proceed to block <NUM>, in which the rotation change control device <NUM> may react to the rotation speed selector <NUM> setting and selectively preventing or permitting actuation of the tong motor control valve <NUM>. When the rotation speed selector <NUM> is in the high-speed setting, the method <NUM> may proceed to the rotation change control device <NUM> permitting the tong motor control valve <NUM> to cause the tong <NUM> to rotate in the break-out direction, as at <NUM>, but preventing the tong <NUM> from rotating in the make-up direction, as at <NUM>. Referring again to block <NUM>, when the rotation speed selector <NUM> is in the low-speed setting, the method <NUM> may proceed to the rotation change control device <NUM> permitting the tong motor control valve <NUM> to cause rotation in the break-out direction, as at <NUM>, and permitting the tong motor control valve <NUM> to cause rotation in the make-up direction, as at <NUM>. Thus, reversing direction, in this embodiment, in either the run or pull mode, is permitted only when the speed selector <NUM> is in the low-speed setting.

<FIG> illustrates a flowchart of a method <NUM> for controlling speed selection of the tong <NUM>, according to an embodiment. The method <NUM> may be implemented at least in part by the piston position sensing device <NUM> (<FIG>), which may be, for example, a part of the pneumatic or electrical circuit that controls or otherwise implements the rotation change control device <NUM>. In some embodiments, at least part of either or both of the rotation change control device <NUM> and/or the piston position sensing device <NUM> may be implemented using relays in an electrical circuit.

The method <NUM> may begin by determining that the rotation speed selector <NUM> is in the low-speed setting, as at <NUM>. This may be accomplished by receiving an analog or digital electric signal, a pneumatic signal, a hydraulic signal, etc. The piston position sensing device <NUM> may be configured to prevent the speed selector <NUM> from being actuated from low to high-speed, e.g., without the tong <NUM> being set to neutral. The neutral setting for the tong <NUM> may be state of the tong <NUM> in which the tong is not hydraulically or otherwise being driven to rotate. Accordingly, the piston position sensing device <NUM>, once recognizing that the speed selector <NUM> is in the low-speed setting at <NUM>, may wait for a signal indicating that the tong is in neutral. If the neutral setting signal is not received, the method <NUM> may block actuation of the rotation speed selector <NUM> from the low-speed setting to the high-speed setting, as at <NUM>. Once the signal that the tong is in neutral is received, the piston position sensing device <NUM> may permit actuation of the speed selector <NUM> to the high-speed setting, as at <NUM>.

<FIG> illustrates a schematic view of a pneumatic circuit that implements the control system <NUM>, according to an embodiment. It is emphasized that this pneumatic circuit is merely an example of one way to implement the control system <NUM>, and one of ordinary skill in the art will recognize that mechanical, electrical, hydraulic, and/or at least partially computer-based systems may be implemented without departing from the scope of the present disclosure.

Referring to the specific, illustrated embodiment shown in <FIG>, there is shown a speed selector valve 501A, which is actuated by the speed selector <NUM> (<FIG>), and a run/pull mode selector valve 501B, which is actuated by the run/pull mode selector <NUM>. The two positions available to each valve 501A, 501B may correspond to the high and low-speed settings for the rotation speed selector <NUM> and the first and second configurations of the run/pull mode selector <NUM>, respectively. In their illustrated states, the valve 501A reflects the high-speed setting, and the valve 501B reflects the run configuration. As such, the system <NUM> is configured to permit rotation in the make-up direction.

The system <NUM> also includes the directional control valve <NUM>, which, in this embodiment, is a pilot-actuated directional control valve <NUM> and a gear shift cylinder <NUM>. The position of the rotation speed selector <NUM> (e.g., valve 501A) may determine to which "end" (representing pilot ports) of the pilot-actuated directional control valve <NUM> pressure is supplied, thereby controlling the position of the pilot-actuated directional control valve <NUM>. Further, the low-speed indicator device <NUM> is shown as including a two-position directional control valve <NUM>. The low-speed indicator device <NUM> may additionally include a mechanical linkage that is configured to change the position of the valve <NUM>, as will be described in greater detail below.

In the configuration illustrated, pressure is received from a source <NUM>, through the valve 501A, a line <NUM>, the piston position sensing device <NUM> (which will be described in greater detail below), via a line <NUM>, a shuttle valve <NUM>, and to the "bottom" (as illustrated in the schematic) of the directional control valve <NUM>. Pressure is also routed directly from the source <NUM> to the directional control valve <NUM>, which the directional control valve <NUM> routes to the bottom of the gear shift cylinder <NUM>, driving a piston <NUM> therein upward, resulting in a retraction of the gear shift cylinder, and thereby a selection of, for example, a high gear in the tong speed controller <NUM>.

The valves 501A, 501B may communicate with a first piston <NUM> and a second piston <NUM>, which may be configured to selectively allow or block linear motion of a spool <NUM>. The pistons <NUM>, <NUM> and the spool <NUM> may at least partially form the rotation change control device <NUM>, which may be coupled to the tong motor control valve <NUM>. The pistons <NUM>, <NUM> may default (e.g., be biased to) to a lowered position, in which the pistons <NUM> each block movement of the spool <NUM> in at least one direction. In an embodiment, when a pressure signal is present in line <NUM>, the first piston <NUM> may be raised, allowing movement of the spool <NUM> to the right, allowing the tong motor control valve <NUM> to rotate the tong <NUM> in the make-up direction. When a pressure signal is present in line <NUM>, the second piston <NUM> may be raised, allowing movement of the spool <NUM> to the left, and causing the tong <NUM> to rotate in the break-out direction. When both pistons <NUM>, <NUM> are raised, the spool <NUM> may be freely movable, and thereby cause rotation on the tong <NUM> in either direction, without additional modulation of the valves 501A, 501B or the selectors <NUM>, <NUM> associated therewith. This satisfies blocks <NUM> and <NUM> in <FIG>.

For example, with the selectors <NUM>, <NUM> (and thus valves 501A, 501B) in their illustrated positions, pressure is routed through the valve 501A to the valve 501B, and then through a shuttle valve <NUM> to the first piston <NUM>. This may raise the first piston <NUM>, thereby allowing the spool <NUM> to move in at least one linear direction, e.g., right, as shown, from the illustrated neutral position. Allowing the spool <NUM> to move may allow for actuation of the tong motor control valve <NUM>, in this case, to cause the tong <NUM> to rotate in the make-up direction. In this configuration, pressure is not routed to the second piston <NUM>, and thus actuation of the spool <NUM> to the right is blocked by the second piston <NUM>. This prevents actuation of the tong motor control valve <NUM> in the break-out direction. Accordingly, blocks <NUM> and <NUM> of <FIG> are satisfied.

When the rotation speed selector <NUM> is actuated to the low-speed setting, the valve 501A associated therewith changes position. As such, pressure is routed from the source <NUM>, through the valve 501A, to the top of the pilot-actuated directional control valve <NUM>, causing the pilot-actuated directional control valve <NUM> to actuate from its illustrated state and instead route pressure to the top of the gear shift cylinder <NUM>. This drives the piston <NUM> downward, resulting in a low gear selection by the tong speed controller <NUM>.

This selection actuates the valve <NUM> of the low-speed indicator device <NUM>, e.g., via the mechanical linkage. The valve <NUM> may then route pressure through a shuttle valve <NUM> to the second piston <NUM>, which raises the second piston <NUM>. The raised second piston <NUM> may allow the spool <NUM> to translate to the left (as illustrated). Further, pressure may be routed from valve 501A to the first piston <NUM> via the shuttle valve <NUM>, which causes the first piston <NUM> to lift away from the spool <NUM>. As such, the spool <NUM> is able to actuate freely. Accordingly, with the run/pull mode selector <NUM> in the run mode, and the speed selector <NUM> in the low-speed setting, the tong motor control valve <NUM> may be movable to cause rotation in either direction, thereby satisfying blocks <NUM> and <NUM> from <FIG>.

The pneumatic circuit illustrated as this example of the system <NUM> will similarly conform to the logic depicted in <FIG> if the valve 501B changes position, from the illustrated position, which corresponds to the run mode, to a position corresponding to the pull mode.

Accordingly, when a user attempts to actuate the speed selector <NUM> directly to high-speed, without first bringing the tong <NUM> to neutral (e.g., allowing both of the pistons <NUM>, <NUM> to lower) the system <NUM> may not implement the gear shift. As shown in <FIG>, the valve 501A is shifted to the high-speed setting, which directs pressure to the piston position sensing device <NUM>, where it is blocked from reaching the shuttle valve <NUM> (or the directional control valve <NUM> beyond). Further, the shuttle valve <NUM> blocks pressure routed through the low-speed indicator device <NUM> from reaching the shuttle valve <NUM> or the pilot-actuated directional control valve <NUM>. As such, until the piston position sensing device <NUM> is opened, which occurs when the second piston <NUM> is lowered, the actuation into the high-speed setting is prevented.

In the illustrated embodiment, when the valve 501B is in the opposite configuration to what is shown, i.e., in the pull mode, pressure is routed to a line <NUM>. The line <NUM> may bypass the piston position sensing device <NUM> and provide pressure to the bottom of the pilot-actuated directional control valve <NUM>, allowing the shifting of the valve <NUM> to the high-speed position, even if the piston position sensing device <NUM> is closed. As such, in this embodiment, when the system <NUM> is in the pull mode, the system <NUM> may permit actuation of the speed selector <NUM> from low to high, without first returning the tong <NUM> to neutral and allowing the pistons <NUM>, <NUM> to fall. This may be permitted because other safety devices, such as snub lines, as described above, may prevent injury to an operator shifting to high in the pull mode. However, in other embodiments, the line <NUM> may instead route through the piston position sensing device <NUM> or a valve controlled by the position of the first piston <NUM>, so as to further ensure safety of rig personnel by preventing direct speed shifting from low to high in the pull mode.

<FIG> illustrates a side, cross-sectional view of the tong motor control valve <NUM> and the rotation change control device <NUM>, according to an embodiment. The tong motor control valve <NUM> may be selectively actuatable (e.g., manually, by operation of a user) to cause the tong <NUM> to rotate in either the first or second direction, and such selective actuation may be blocked or permitted via the rotation change control device <NUM>.

As shown, the valve <NUM> may include a first housing <NUM> through which a spool <NUM> is received. A lever arm <NUM>, which may be manipulated by a user, couples to the spool <NUM>, and movement of the arm <NUM> left or right causes translation of the spool <NUM> within the first housing <NUM>. The first housing <NUM> also includes an input port and two output ports <NUM>, <NUM>. Accordingly, the spool <NUM> may be translated from left-to-right to selectively allow communication between the input port and the output ports <NUM>, <NUM>, which are connected to respective ports of the tong motor. For example, when slid to the left, the spool <NUM> may permit communication through the first housing <NUM> between the input port and the output port <NUM> and through the motor port to which it is connected, while permitting fluid flow through the output port <NUM> to a return line. This results in the tong <NUM> rotating in the break-out direction. When slid to the right, the spool <NUM> may permit communication through the first housing <NUM> between the input port and the output port <NUM>, while directing fluid flow from the output port <NUM> through a return line. This results in the tong <NUM> rotating in the make-up direction.

The illustrated embodiment of the rotation change control device <NUM> may include a housing <NUM> (referred as a "second" housing for contrast with the first housing <NUM>), which may be coupled to the first housing <NUM>. The second housing <NUM> may receive the spool <NUM> therein (the spool <NUM> may be referred to as a "first" spool, and the spool <NUM> may be referred to as a "second" spool, but this naming convention is merely to precisely identify the two spools, not to imply that one requires the other). The second spool <NUM> may be configured to move with the first spool <NUM>. Further, if the second spool <NUM> is blocked from movement in one or both lateral directions, the first spool <NUM> may likewise be blocked. Blocking the first spool <NUM> may, in turn, block actuation of the tong motor control valve <NUM>.

As was also shown in <FIG>, the pistons <NUM>, <NUM> may be configured to engage the spool <NUM>. The second spool <NUM> may include a central shoulder <NUM>, which may engage the pistons <NUM>, <NUM> and block movement of the spool <NUM> therepast, unless the pistons <NUM>, <NUM> are lifted away from the first spool <NUM>. Moreover, the pistons <NUM>, <NUM> may be biased toward the second spool <NUM>, e.g., via a spring, such that the default position of the pistons <NUM>, <NUM> is down, engaging the second spool <NUM>.

Further, the second housing <NUM> may include first and second signal ports <NUM>, <NUM>. The first port <NUM> may communicate with the line <NUM> (<FIG>), and the second port <NUM> may communicate with the line <NUM> (<FIG>). Thus, as described above, when a pressure signal is present at the line <NUM> and the first port <NUM>, the pressure raises the first piston <NUM>, thereby allowing actuation of the second spool <NUM> to the left, and likewise allowing movement of the first spool <NUM> to the left, which causes the tong to rotate in the break-out direction. Likewise, when a pressure signal is present at the line <NUM> and the second port <NUM>, the pressure raises the second piston <NUM>, allowing movement of the second spool <NUM> and the first spool <NUM> to the right, which allows the tong motor control valve <NUM> to cause the tong <NUM> to rotate in the make-up direction.

The illustrated embodiment of <FIG> also includes the piston position sensing device <NUM>, which is formed as a third housing <NUM> coupled to the second housing <NUM>. The third housing <NUM> may form an input port <NUM> that communicates with the line <NUM> (<FIG>), and an output port <NUM> that communicates with the line <NUM> (<FIG>). When the piston <NUM> is raised, an extension <NUM> of the piston <NUM> blocks communication between the input port <NUM> and the output port <NUM>. When the piston <NUM> is lowered, communication therebetween is permitted. Thus, since the piston <NUM> is raised when the speed selector <NUM> is in the low-speed setting, actuation of the speed selector <NUM> from the low-speed setting to the high-speed setting is only permitted when pressure is relieved in the system, e.g., the piston <NUM> is lowered.

<FIG> illustrates a side view of a portion of the control system <NUM>, according to an embodiment. In this view, the speed selector <NUM>, the gear shift cylinder <NUM>, and the low-speed indicator device <NUM> are visible. As discussed above, actuation of the speed selector <NUM> may toggle between the high and low-speed setting, which, if permitted, determines the position of the valve 501A. Also visible in <FIG> is an example of the run/pull mode selector <NUM>, which may be a rotary switch movable between a run mode (e.g., first configuration) and a pull mode (e.g., second configuration), as indicated.

A linkage connects together the gear shift cylinder <NUM> and a tong gear change mechanism. The tong gear change mechanism may include a shift shaft <NUM>, movement of which may shift gears in the tong gear change mechanism. The linkage may include one or more rods, brackets, braces, etc. For purposes of illustration, the present embodiment includes a guide shaft <NUM> and an indicator shaft <NUM>, which are coupled together. Further, the input shaft <NUM> is also coupled to the gear shift cylinder shaft, so as to be movable vertically therewith. The output shaft <NUM> is also coupled to the shift shaft <NUM> via a toggle mechanism <NUM>. Accordingly, movement of the gear shift cylinder output shaft downwards (e.g., to a low-gear position) in response to the selector <NUM> being moved to the low-speed setting may cause the guide shaft <NUM> to move downwards. This downwards movement is also transmitted to the indicator shaft <NUM>, which in turn the shift shaft <NUM> to move upwards. When the selector <NUM> is actuated to the high-speed setting, the gear shift cylinder <NUM> moves upward, and the shafts <NUM>, <NUM> move the shift shaft <NUM> downwards, thereby shifting to the high gear setting.

In addition, the indicator shaft <NUM> may contact an actuator <NUM> of the low-speed indicator device <NUM> when the gear shift cylinder <NUM> is in the low-speed position (i.e., moved downward from the position illustrated). When contacted, the actuator <NUM> may shift the valve <NUM> from its default position (illustrated in <FIG>), to the opposite position, which may confirm that the tong <NUM> is being operated in the low-speed setting.

<FIG> illustrates a flowchart of a method <NUM> for controlling a tong, e.g., the tong rotation and/or speed, according to an embodiment. The method <NUM> may include receiving a signal representing that a run/pull mode selector is in a first configuration, as at <NUM>. The tong may be configured to rotate primarily in a first, make-up direction when the run/pull mode selector is in the first configuration, but may, under certain conditions, be permitted to rotate in a second, break-out direction, e.g., to address cross-threading.

The method <NUM> may also include receiving a signal representing that a rotation speed selector is in a high-speed setting, as at <NUM>. The tong is configured to rotate at a first speed when the rotation speed selector is in the high-speed setting. The method <NUM> may also include automatically (e.g., without intervention by a human operator) preventing rotation of the tong in the second direction until receiving a signal representing that the rotation speed selector has been actuated to the low-speed setting, as at <NUM>. In an embodiment, the method <NUM> may also include receiving a signal representing that the rotation speed selector is in (e.g., has been actuated to) a low-speed setting, as at <NUM>. In response, the method <NUM> may proceed to automatically permitting rotation of the tong in the second direction, as at <NUM>. Permitting actuation at <NUM> may include actuating a low-speed indicator device in response to the rotation speed selector being in the low-speed setting. In an embodiment, actuating the low-speed indicator device is performed using a mechanical linkage between a gear shift valve and the low-speed indicator device.

The method <NUM> may also include preventing actuation of the rotation speed selector to the high-speed setting, while the tong is operating in the low-speed setting (e.g., in response to receiving the signal that the rotation speed selector is in the low-speed setting), as at <NUM>. The method <NUM> may also include permitting actuation of the rotation speed selector to the high-speed setting in response to receiving a signal representing that the tong is in a neutral setting.

In one specific embodiment, the method <NUM> may further include blocking the execution of the rotation speed selectors output commands in response to receiving signals from the interlock system that the tong is operating in either the make up or break out direction. Accordingly, preventing rotation in the second direction may include blocking the spool from moving in at least one direction using a second piston in a lowered position. The method <NUM>, may include moving at least one of the first or second pistons to permit movement of the rotation change control device in response to signals from the interlock system that the tong motor control valve is in the neutral condition.

Claim 1:
A control system (<NUM>) for a tong (<NUM>) for a drilling rig, the control system comprising:
a tong motor control valve (<NUM>) that is selectively actuatable to cause rotation of the tong in a first direction or in a second direction;
a run/pull mode selector (<NUM>) configured to actuate between a first configuration for running tubulars into a well and a second configuration for pulling tubulars from the well;
a rotation speed selector (<NUM>) configured to actuate between a high-speed setting configured to cause the tong to be driven to rotate at a first speed, and a low-speed setting configured to cause the tong to be driven to rotate at a second speed, the first speed being greater than the second speed; and characterised by:
a rotation change control device (<NUM>) configured to selectively prevent or permit actuation of the tong motor control valve based on whether the run/pull mode selector is in the first configuration or the second configuration and whether the rotation speed selector is in the high-speed setting or the low-speed setting.