power tong operator free sample

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This invention is directed to apparatus and methods for aligning wellbore tubulars; and to power tongs used in making and breaking joints of tubular members such as wellbore casing and tubing; to parts thereof; including, but not limited to gripping elements, and methods of their use.

During the drilling of oil and gas wells and the production of materials therefrom, various operations require the connection and disconnection of successive lengths of threaded tubulars such as pipe, casing, or tubing. Tools known as tongs are used to "make" and "break" such connections. Certain known power tongs have a body, a rotary rotatably mounted in said body and at least one active jaw which, on rotation of the rotary is cammed against a pipe in the rotary and grips it for rotation with the rotary. In known arrangements the camming action is generated by a cam member which is bolted to the rotary and is shaped so that the active jaw is cammed against the pipe on rotation of the rotary relative to the active jaw in one sense and will be released on rotation of the rotary relative to the active jaw in the opposite sense.

With known tongs high torques are applied to tubulars due to combinations of factors such as thread sealing requirements, the presence of corrosion, the existence of distortion, and pipe size and weight. Both in the "make" direction of rotation when a shoulder is suddenly encountered, and in the "break" direction at initial engagement of the tong and disengagement of the threads high shock forces may arise; e.g., with a power-driven tong, in excess of 50,000 foot-pounds of torque may be exerted, while relatively small die elements on jaws of the tong engage the pipe with extremely high force loadings. Slippage occurs and pipe surfaces become marred, marked, indented, or otherwise damaged.

Dies for gripping jaws have been provided with multiple serrations, or penetration features, to provide the interference contact at the joint surface. Grip element penetration into the joint surface is limited and controlled. The distribution and balance of grip element energizing forces are critical factors in the design, development and evaluation of such tong mechanisms. Linkages, levers, wedges, and cams are used to balance force components. Grip elements, or dies, are accurately disposed within carrier bodies, or jaws, which span a circumferential segment of the joint surface.

Uneven die loading can cause excessive indentation, marring or damage to a tubular surface. Drag or braking devices are used in certain tongs to effect proper biting of the dies relative to the pipe. The head or other member supporting the dies is frictionally restrained to insure that the dies do not simply rotate with the rotary as the rotary is driven.

Other tongs use an endless belt, chain or flexible material loop for gripping a tubular. Such tongs are disclosed in U.S. Pat. Nos. 3,799,010; 3,906,820; 3,892,140; 4,079,640; 4,099,479; and 4,212,212. There are a variety of problems associated with certain of these tongs:

Jaw/die tongs and the belt/chain tongs are used with relatively hard and rigid metal tubulars such as casing and tubing. If these tongs are used with thick tubulars or tubulars made from relatively "softer" metals or from premium metals such as high alloy steels or low carbon steels or tubulars made from non-metal materials such as fiber glass, they often literally chew up the tubular. The use of strap wrenches is inadequate since the torque applied with such wrenches cannot be precisely controlled.

Certain tubulars are treated with a rust or corrosion resistant material or coating. If the coating is indented, gouged, or broken, its protective purpose is defeated. Producing enough force in a tong to join such tubulars while not injuring a protective coating presents a dilemma.

The present invention, in certain embodiments, discloses a power tong for joining tubulars so that marking of, indentation of, and surface injury to tubulars are reduced or eliminated. In one aspect a power tong is provided and a method of its use for handling tubulars coated with a corrosion-resistant material which should not be broken or penetrated. In one embodiment such a tong has one or more gripping jaws with gripping elements made of aluminum alloys, zinc, zinc alloys, aluminum, brass, bronze, cermet, plastic, fiberglass, metal alloys, or a combination thereof which present a smooth face (straight or curved) to a tubular without any teeth, pointed projections, or toothed dies. In one aspect the gripping elements are releasably connected directly to jaws. In another aspect the gripping elements are releasably connected to a jacket or holder which itself is releasably connected to a jaw.

In one aspect the cylinder(s) are powered by a small air-driven hydraulic pump with an hydraulic fluid reservoir mounted on a plate on the movable or fixed jaw. Air is supplied to activate a motor of the pump and the pump then provides hydraulic fluid to move a piston of the hydraulic cylinder(s). The motion of the cylinder moves the movable jaw on its roller to travel to a pre-load position on the cam. The cylinder applies pressure until the hydraulic pressure is released. A hydraulic fluid accumulator and a valve may be used to maintain hydraulic pressure at all times so that the cylinder(s) continuously maintain the desired load on the jaw until the air supply to the pump is removed.

In another aspect the cylinders are connected to a rotary of the tong or to any other member that rotates with the rotary rather than to a fixed jaw. Such a pre-load system may, according to this invention, be used with any tong including a tong that does use toothed dies.

In one embodiment the present invention discloses a gripping arrangement for a tong with a sheet of grit which is preferably bonded to a carrier plate. In another embodiment the gripping arrangement comprises a layer of flexible material having a smooth flat surface or a surface with ridges and valleys, for example in the fashion of the surface of a file. The flexible material, in one aspect, is metal, for example sheet aluminum, zinc, brass, bronze, zinc alloy, aluminum alloy, stainless steel, or steel having a thickness of about 1.5 mm. The layer of flexible material may be used in conjunction with a carrier plate or on its own. In a further embodiment the gripping arrangement may comprise a layer of perforate material one of both surfaces of which are preferably coated with grit to facilitate adhesion. The layer will typically be formed from metal having a thickness of about 1.5 mm. The layer may be used in conjunction with a carrier plate or used on its own. In yet another embodiment the gripping arrangement may comprise a layer of expanded mesh, e.g. metal mesh, which has been flattened. One or both surfaces of the expanded mesh may be coated with grit and the layer may be used in conjunction with a carrier plate or used on its own. The grit may comprise, for example, diamond dust, particles of silicon, zircon, tungsten carbide and mixtures thereof. The gripping arrangement may comprise end plates which are attached to the carrier plate. Preferably, the carrier plate is provided with side flanges for insertion into a jaw holder. The present invention also provides a jaw assembly fitted with a gripping arrangement in accordance with the present invention. Preferably, the jaw assembly includes a jaw holder having an arcuate recess which accommodates an arcuate pad of resilient elastomeric material which supports said gripping arrangement. Advantageously, at least one shim is provided which is disposed between said arcuate pad of resilient elastomeric material and said gripping arrangement. The shim will be flexible and generally from 0.5 mm to 1.0 mm thick and made from sheet metal. The present invention also provides a tong fitted with at least two such jaw.

In one embodiment the present invention discloses an apparatus for aligning tubulars and includes a guide on one of a power tong and a backup tong. In one embodiment the apparatus has a socket centralizer mounted on said one of said power tong and said backup tong. In one aspect, said one of said power tong and said backup tong is said power tong. In another embodiment, the apparatus includes a power tong and a backup tong, and the guide is mounted on the power tong and apparatus is provided to maintain the power tong and the backup tong in a certain juxtaposition during a stabbing operation. Preferably, said apparatus includes locating rods on one of the power tong and the backup tong and blocks shaped to receive at least the ends of the locating rods on the other of the power tong and the backup tong. Advantageously, the backup tong is provided with at least two prismatic jaw assemblies to locate the backup tong in fixed juxtaposition with respect to a tubular being gripped.

The present invention, in one aspect, provides a jaw unit for use in a tong, which jaw unit comprises a jaw holder and a jaw movable with respect to said jaw holder, characterized in that said jaw is slidably mounted on said jaw holder. Preferably, said jaw is slidable with respect to said jaw holder about an arcuate path. Advantageously, said jaw has a gripping surface which is substantially arcuate for gripping the surface of a tubular and the center of curvature of such arcuate path lies between the center of curvature of said grip ping surface and said arcuate path. The gripping surface may be a continuous surface or defined by several spaced apart gripping elements. Preferably, the center of curvature of said arcuate path lies between the center of curvature of said grip ping surface and said gripping surface. Advantageously, the center of curvature of said arcuate path is substantially midway between the center of curvature of said gripping surface and said gripping surface. Preferably, one of said jaw and said jaw holder is provided with an arcuate track which defines said arcuate path, and the other of said jaw and said jaw holder is slidably mounted in said arcuate track.

The present invention also provides a jaw assembly comprising two jaw units in accordance with the present invention. Preferably, said jaw units are mounted for pivotal movement about a common pivot shaft. Advantageously, said jaw assembly includes means which bias said jaw units apart. The present invention also provides a rotary fitted with a jaw unit in accordance with the present invention, a rotary fitted with a jaw assembly in accordance with the present invention, and a tong fitted with a rotary in accordance with the present invention.

One of the features of existing tongs is that their rotaries are difficult to furnish. Thus, routine maintenance usually involves dismantling the whole rotary, checking the parts and reassembling the whole. While this is a straightforward procedure in the clean conditions of a workshop it can be problematic when carried out in a muddy field, in sand or in snow. The present invention aims to help solve this problem and provides a rotary which comprises a top section, a bottom section, and a peripheral wall therebetween, characterized in that at least one of said top section and said bottom section is provided with an elongate slot which, when said rotary is in use, accommodates a pivot shaft on which a jaw assembly can be pivotally mounted.

Jaw holders and jaws for tongs are traditionally machined from a solid piece. This is a comparatively expensive procedure. The present invention proposes to make such parts from a stack of individually cut laminations.

Such methods and devices including a power tong with at least one jaw with at least one tubular gripping element having a smooth gripping surface (flat or curved) and, in one aspect, such an element which is flexible;

FIG. 2A is a perspective view of a tubular connection system according to the present invention. FIGS. 2B and 2C are perspective views of a casing tong of the system of FIG. 2A.

FIG. 5A shows schematically an initial position of elements of a tong system according to the present invention. FIG. 5B shows pre-loading on a pipe of the jaws of the system of FIG. 5A. FIG. 5C shows a tubular gripped with the system of FIG. 5A.

FIGS. 1A-1C show a typical prior art power tong that uses fixed jaws and a movable jaw to grip pipe for tubular disconnecting and connecting operations. An outer case houses a powered rotary to which the jaws are mounted. A cam surface of the rotary moves a movable (ACTIVE or MASTER) jaw into (and away from) gripping contact with a tubular, e.g. pipe. Each jaw has toothed gripping inserts to facilitate engagement with the surface of the tubular (see FIG. 1B). FIG. 1C shows the tong in an "OPEN" position in which the tubular is not gripped.

The tong shown in FIG. 1A is a Weatherford Model 14.5-50 High Torque Tong. The brochure "New ! Weatherford Model 14.5-50 High Torque Tong," (1991) and the manual entitled "Model 14.5-50 Hydraulic Power Tong Installation, Operation and Maintenance" (1993) are submitted herewith and incorporated herein fully by reference for all purposes. It is to be understood that the teachings of the present invention are applicable to any tong and any tong system that has one or more gripping elements or jaws and that the Model 14.5-50 tong is shown here for illustrative purposes and not by way of limitation of the scope of the present invention.

As shown in FIG. 2A a system 10 according to the present invention includes a power tong 100 according to the present invention which is like the tong of FIG. 1A but which also includes a unique jaw system 110 with inserts 150 on fixed jaws 120 and insert 152 on movable jaw 122 and at least one jaw pre-load assembly like that shown in FIG. 5A. The system 10 includes a free floating backup tong 12.

As shown in FIGS. 2B and 2C, rods 112 are connected to the movable jaw 122. The inserts 150 are on fixed jaws 120 and the insert 152 is on a movable jaw 122 (corresponding to the fixed jaws and active jaw, respectively, of the tong of FIG. 1A).

FIGS. 4A-4G illustrate an alternative jaw mounting system in which holders are interposed between jaw bodies and inserts. The holders protect the jaws from damage if the inserts wear down and a variety of different types and/or sizes of inserts may be used with and interchanged on a single holder. In one aspect it is within the scope of this invention to use these holders to mount conventional toothed dies to a tong jaw and to use them for easy substitution of new and/or different dies.

FIG. 4A shows a jaw system 400 for a tong (like the tong of FIG. 2A) which has two fixed jaws 402 and a movable (movable toward and away from a tubular to be gripped 403) jaw 404. Each jaw 402 has a jaw body 405 with a holder 406 secured thereto. In one aspect dovetail keys 407 secured to the holder or releasably mounted thereto fit in corresponding slots 408 of the jaw bodies 405 to releasably mount the holder 406 to the body. In one aspect dovetail keys 409 releasably mount the holders 406 to jaw bodies 405. The dovetail keys 409 are releasably held in corresponding recesses 411 in the holders 406. One or more dovetail keys 409 may be used (two shown for each holder 406).

FIG. 5A shows a tong system 500 with a tong having a movable rotary 502, fixed jaws 504, 505, and a movable jaw 506 (remainder of tong, not shown, like the tong of FIG. 2A; like the tong of FIG. 1A, but with the added features discussed here). Pins 520 pin the fixed jaws to the rotary. Inserts 522 on the fixed jaws 504, 505 are like the inserts described herein for other fixed jaws. Insert 524 on the movable jaw 506 is like other inserts described herein for movable jaws. A pre-load cylinder 508 to assist in make-up is pivotably connected at one end to the fixed jaw 505 and at the other end to the movable jaw 506. A pre-load cylinder 510 to assist in break-out is pivotably connected at one end to the fixed jaw 504 and at the other end to the movable jaw 506. It is within the scope of this invention for the ends of cylinders connected to the fixed jaws to instead be secured to the rotary or to a support ring or other member that rotates with the rotary. It is within the scope of this invention to employ one cylinder interchangeable between the positions of the cylinders 508 and 510 (FIG. 5A) or one cylinder connectible to the fixed jaw 506 at one end for break-out and at the other end of the fixed jaw 506 for make-up with the other cylinder end secured to the rotary. Rollers 530 rotatably mounted on the movable jaw 506 co-act with cam surfaces 532 on the rotary 502 to move the jaw 506 to operative and inoperative positions.

Air in a line 640 selectively applied with a control system 650 (e.g. mounted on the rig floor, on the tong or remote controlled) selectively actuates the pump 630 to pump fluid through the valve 602 to the pre-load cylinders. The directional control valve 602 is either manually operated or operated by remote control. Correct fluid pressure is monitored with a gauge 651.

As shown in FIG. 5C the tubular 650 has been gripped due to the action of the pre-load cylinder 510 with a suitable pre-load force (e.g., but not limited to, about 500, 1000, 5000, 10000 or 50000 pounds of force). This force is sufficient that when the rotary 502 of the tong is rotated the jaws do not slip on the tubular 650; but the pre-load force is sufficiently low that the jaws do not mark or damage the tubular 650.

FIG. 8 shows schematically a top view of a power tong according to the present invention. A power tong T has an hydraulic motor M with control/monitor apparatus C on a tong case S. A movable jaw J is moved and rotated by a rotary R which is moved by interconnection, via appropriate gearing, by the motor M. Fixed jaws F and G are secured to the rotary R. A first pre-load cylinder D connects the movable jaw J to the fixed jaw G for applying a pre-load to the movable jaw for make-up operations. A second pre-load cylinder L connects the movable jaw J to the fixed jaw F for applying a pre-load to the movable jaw for break-out operations. An insert I (any insert disclosed herein) is secured to the movable jaw J and inserts K (any insert disclosed herein) are secured to the fixed jaws F and G.

FIG. 9 shows a tong jaw 450 according to the present invention with an insert 454 (any insert disclosed herein) and rods 452 secured thereto, e.g. by welding. The rods 452 provide a member to which either a cylinder body or a piston of a pre-load piston cylinder apparatus is connectible. Instead of the rods 452 as shown which extend from above the jaw 450 to a point below it, only rod sections may be used secured to one or both sides of the jaw to provide a securement member for an end of a pre-load apparatus.

According to the present invention a variety of apparatuses and devices may be employed to pre-load a tong jaw having one or more smooth faced gripping insert elements thereon. In one aspect a manually activated pre-load cylinder is used which has fluid or material manually introduced therein to apply a pre-load or manually removed therefrom to release a pre-load. In another aspect a pre-load cylinder is pivotably secured at one end to a rotary or part thereof and the other end is releasably connectible to either end of a movable jaw so that a pre-load may be applied, selectively, to either end of the movable jaw for make-up or break-out operations as desired. In one aspect such a pre-load cylinder has a rod with an end member receivable in and movable in a slot in the movable jaw or there are recesses at either end of the jaw for holding the end member of the rod so that a pre-load can be applied. A secondary small cylinder may be used to selectively move the pre-load cylinder in the jaw slot or it can be moved manually. In another embodiment the tong"s movable jaw has one or more upwardly projecting lugs engageable by a forked piston rod end of a pre-load piston/cylinder that is attached to the rotary. The rotary is rotated so that the jaw is cammed into the pipe to be rotated in a pre-load position and then the forked rod is removed for further tong operations.

In use, two or more jaw assemblies are placed in a tong and are disposed around a length of casing. The jaw assemblies 1001, 1001" are then advanced radially inwardly in the direction of arrows "A" (FIG. 12) until they engage and firmly grip the casing. Because of the flexible construction of the gripping arrangement 1007, the shims 1006 and the arcuate pad 1004, the friction layer 1009 substantially conforms to the circumference of the casing and grips the casing with a substantially uniform gripping action. Once the casing has been firmly gripped the jaws are rotated by the tong in the usual manner. It will be noted that circumferential forces applied to the friction layer are transmitted through the carrier plate 1008 so that any local loads caused, for example by an irregularity in the surface of the casing are redistributed by the carrier plate 1008 and transmitted to the jaw holder 1002 via the side flange 1011 and the arcuate pad 1004 (see FIG. 18).

Referring to FIGS. 19A and 19B of the drawings there is shown a conventional tong assembly which is generally identified by the reference numeral 2001.

The power tong 2002 comprises a pair of gates 2004, 2005 which are held together in the position shown by latch 2006. When the latch 2006 is released the gates 2004, 2005 can be swung open by admitting hydraulic fluid to piston and cylinder assemblies 2007 and 2008. The power tong 2002 also contains a rotary 2009 which is provided with four jaw assemblies 2010. The rotary 2009 can be rotated by a hydraulic motor 2011.

The backup tong 2003 is provided with two gates 2012, 2013 which are held together by latch 2014 but which, when latch 2014 is released can be swung to an open position.

Once the pin is correctly located the stabbing guide is removed. The gates 2004, 2005 of the power tong 2002 and the gates 2012, 2013 of the backup tong 3 are then opened and the tong assembly 2001 moved towards the casing until the lower length of casing lies within the backup tong 2003 and the upper length of casing lies within the power tong 2002. The gates 2004, 2005, 2012, 2013 are then closed and latched. Jaw assemblies in the backup tong are then advanced to engage the lower length of casing while jaw assemblies in the power tong 2002 are advanced to grip the upper length of casing. The hydraulic motor 2011 is then actuated to turn the rotary 2009 and rotate the upper length of casing relative to the lower length of casing. The tong assembly 2001 is supported by a pneumatic lifting cylinder 2015 which enables the power tong 2002 to move towards the backup tong 2003 as the pin enters the socket. Reaction forces are transmitted by columns 2016 disposed to either side of the tong assembly 2001 and by a series of levers in a known manner. It should be noted that the power tong 2002 is free to move in a plane parallel to the backup tong 2003 within certain limits.

The apparatus 2100 comprises a tong assembly 2101 which is generally similar to the tong assembly 2001 shown in FIGS. 19A and 19B and parts of the tong assembly 2101 similar to the tong assembly 2001 have been identified by similar reference numerals in the "2100" series.

Turning first to the guide 2117 it will be seen from FIG. 21B that this comprises four identical components 2118 which are bolted to the top of the power tong 2102. As best shown in FIG. 21C each component is tapered so as to guide the pin of an upper casing to the center of the opening of the power tong 2102.

Referring now to FIG. 22, the backup tong 2103 is provided with three prismatic jaw assemblies 2119a, 2119b, and 2119c which, when actuated, hold a lower length of casing 2120 in a fixed position relative to the backup tong 2103.

As shown in FIG. 23 the backup tong 2103 is provided with three upwardly extending locating rods 2121 which are each provided with a conical tip 2122. Similar, the underside of the power tong 2102 is provided with three blocks 2123 each of which is provided with a recess 2124 shaped to receive the conical tip 2122 of a respective locating rod 2121.

In use, the lower length of casing 2120 is first secured by slips on the rig floor in the usual manner. The gates 2112 and 2113 of the backup tong 2103 are then opened and the tong assembly 2101 moved into position with the backup tong 2103 circumjacent the lower length of casing 2120 and immediately below the socket 2125 thereof.

The gates 2112 and 2113 are then closed by hydraulic piston and cylinder assemblies 2126 and 2127 and the latch 2114 closed. The prismatic jaw assembly 2119a is fixed while prismatic jaw assemblies 2119b and 2119c are automatically advanced by a predetermined distance when the latch 2114 is closed. This grips the lower length of casing firmly and also ensures that the backup tong 2003 is in a fixed position relative to the lower length of casing 2120. The position thus far attained is shown in FIG. 23.

At this time pneumatic lifting cylinder 2115 is extended which lowers the backup tong 2003. The conical tips 2122 of the locating rods 2121 enter the recesses 2124 of the blocks 2123 and thus locate the power tong 2002 with respect to the backup tong 2003. This in turn locates the guide 2117 with respect to the lower length of casing 2120 so that the center of the guide 2117 is coaxial with the axis of the lower length of casing 2120. This position is shown in FIG. 24.

The power tong 2102 is then raised so that the blocks 2123 are well clear of the locating rods 2121. At this point the jaw assemblies in the power tong 2102 are applied to the upper length of casing 2128 and the hydraulic motor 2111 actuated to rotate the rotary and screw the pin 2129 into the socket 2125. During the procedure the power tong 2102 moves towards the backup tong 2103. However, even when the joint is tightened to the required torque the blocks 2123 still lie a short distance above the conical tips 2122 of the locating rods 2121.

At this stage the jaw assemblies of both the power tong 2102 and the backup tong 2103 are relaxed, the gates 2104, 2105, 2112 and 2113 opened and the tong assembly 2101 retracted in preparation for the casing being lowered. It will be noted that one component 2118 of the guide 2117 is mounted on each of the gates 2104, 2105 and accordingly the guide 2117 opens and closes with the gates 2104, 2105.

For certain applications a backup tong is not required, for example where the power tong can conveniently be restrained by a chain attached to the drilling tower.

The apparatus 2200 comprises a power tong 2202 which is generally similar to the power tong 2002. The basic construction of the power tong 2202 is similar to the power tong 2002 and parts having similar functions have been identified by the same reference numeral in the "2200" series.

The main differences are that the apparatus 2200 does not include a backup tong and that it is provided with a guide 2217 and a socket centralizer 2230.

In use, the lower length of casing 2220 is first secured by slips (not shown) with the socket 2225 facing upwardly close to the slips. The power tong 2202 is then lowered onto the socket 2225 so that the socket 2225 enters the socket centralizer 2230 and aligns the socket centralizer 2230, the socket 2225 and the guide 2217. The upper length of casing 2228 is then lowered so that its pin 2229 enters the guide 2217, is center there by and enters the socket 2225. At this point power tong 2202 is raised. Its jaw assemblies are then advanced to grip the upper length of casing 2228 which is then rotated to screw the pin 2229 into the socket 2225. Once the joint is tightened to the required torque the gates 2204, 2205 are opened and the power tong 2202 withdrawn.

The embodiment shown in FIG. 29 is generally similar to that shown in FIG. 28 except that the apparatus 2300 also includes a backup tong 2303. Since the upper length of casing 2328 and the lower length of casing 2320 are being aligned by the guide 2317 and the socket centralizer 2330 no special arrangements need be made for aligning the power tong 2302 and the backup tong 2303.

The procedure for connecting the upper length of casing 2328 to the lower length of casing 2320 is as follows. First, the lower length of casing 2320 is secured in slip (not shown). The gates 2312, 2313 of the backup tong are then opened and the apparatus 2300 maneuvered so that the lower length of casing 2320 is disposed within the backup tong 2303. The power tong 2302 is then lowered until the socket 2325 on the lower length of casing 2320 is received within the socket centralizer 2330. The upper length of casing 2328 is then lowered until the pin 2329 passes through guide 2317 and enters the socket 2328. Only at this stage are gates 2312, 2313 closed and the jaw assemblies of the backup tong 2303 activated to grip the lower length of casing 2320. The power tong 2302 is then raised and its jaw assemblies activated to grip the upper length of casing 2328 which is then rotated to cause the pin 2329 to enter the socket 2325 and the joint to be tightened to the desired torque. The jaw assemblies are then relaxed and the gates 2304, 2305, 2312, 2313 of the power tong 2302 and the backup tong 2303 opened prior to retracting the apparatus 2300.

Various modifications to the embodiments described are envisaged, for example, if desired, the guide and the socket centralizer could be mounted on the backup tong 2303 rather than the power tong 2302. Alternatively, the guide could be mounted on the backup tong without a socket centralizer. Such an arrangement is shown in FIG. 30.

The embodiment shown in FIG. 30 is generally similar to that shown in FIG. 19a and 19b and parts of the tong assembly 2401 similar to the tong assembly 2001 have been identified by similar reference numerals in the "2400" series. One difference is that the top of the backup tong 2403 is provided with a guide 2417.

In use, the lower length of casing 2420 is first secured by stops 2431 on the rig floor in the usual manner. The gates 2412 and 2413 of the backup tong 2403 are then opened. Since two of the four components 2418 of the guide 2417 are mounted on the gates 2412 and 2413 the guide 2417 opens with the gates 2412 and 2413 so that the lower length of casing 2420 can enter the backup tong 2403 when the carriage 2432 which supports the apparatus 2400 is advanced towards the casing 2420 on rails 2433. When the lower length of casing 2420 is fully within the backup tong 2403 the gates 2412 and 2413 are closed. The components 2418 of the guide 2417 have a stepped interior (not visible in FIG. 30) so that the lower part of each component 2418 touches the socket on the top of the lower length of casing 2420 whilst the upper part of the interior of each component 2418 tapers inwardly to form a funnel. Once the lower length of casing 2420 has been gripped the upper length of casing 2428 is lowered through the power tong 2402 towards the lower length of casing 2420. The guide 2417 guides the pin on the bottom of the upper length of casing 2428 into the socket. The power tong 2402 is disposed a small distance above the guide 2417. Once the pin of the upper length of casing 2428 has entered the socket on the lower length of casing the jaws of the power tong 2402 are applied to the upper length of casing 2428 which is rotated until the joint reaches the desired torque.

Referring now to FIG. 38, the rotary 3100 is shown fitted in a tong 3116. As shown in FIG. 39 and 40, the rotary 3100 is formed as a one piece casting which comprises a top section 3117, a bottom section 3118, and a peripheral wall 3119 on which is formed a toothed track 3120. Both the top section 3117 and the bottom section 3118 are provided with an elongate slot 3121, 3122 respectively. Each elongate slot 3121, 3122 has its center of curvature on the center of rotation of the rotary 3100.

As can be seen in FIG. 38 and FIGS. 31 to 37, the sides of the rotary 3100 are provided with cams 3128, 3129, 3130 and 3131 which are screwed to the rotary 3100. The rotary 3100 is located in the tong 3116 by nine guide rolls 3132, five of which are visible in FIG. 38. The guide rolls 3132 each have an upper and a lower roller which bears against the peripheral wall 3119 of the rotary 3100 above and below the toothed track 3120 respectively.

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.

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 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.

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 fl