eckel power tong dies manufacturer

Tong dies have come a long way since tongs became commonplace in the oilfields. Eckel has been at the forefront of this developing technology with the development of larger wrap-around type dies for many of its tong models. We offer coarse tooth design and fine tooth design depending on the application.

Rig Dies (Typically 1" and 1-1/4" wide) are available in coarse tooth die are typically used for casing and drill pipe where tool joint O.D. sizes vary from joint to joint. Also, Drill Pipe is also a harder steel and rig dies provide a more aggressive and better grip. Rig dies are available with the following surface areas:

Coated Contour True Grit® Dies: Used on chrome and fiberglass tubulars where reduced die penetration and die marking is greatly desired. For more information refer to the

A two-speed Hydra-Shift® motor coupled with a two-speed gear train provides (4) torque levels and (4) RPM speeds. Easily shift the hydraulic motor in low speed to high speed without stopping the tong or tublar rotation, saving rig time.

Used on corrosion resistant alloys (CRA) and fiberglass tubulars where reduced markings on the tubular is desired. Eckel"s Coated True Grit® Dies utilize Tungsten Carbide grit which provides many more points of contact on the surface of the tubular than our Pyramid Fine Tooth dies.

A patented door locking system (US Patent 6,279,426) for Eckel tongs that allows for latchless locking of the tong door. The tong door swings easily open and closed and locks when torque

is applied to the tong. When safety is important this locking mechanism combined with our safety door interlock provides unparalleled safety while speeding up the turn around time between connections. The Radial Door Lock is patented protected in the following countries: Canada, Germany, Norway, United Kingdom, and the United States.

The WD Tri-Grip® Backup is a high performance no compromise backup that is suitable for make-up and break-out of the most demanding connections. The WD Tri-Grip®Backup features a three head design that encompasses the tubular that applies an evenly distributed gripping force. The WD Tri-Grip®is a high performance backup with no compromises that is available for specific applications that provdies exceptional gripping capabilities with either Eckel True Grit® dies or Pyramid Fine Tooth dies.

The field proven Tri-Grip® Backup features a three head design that encompasses the tubular that applies an evenly distributed gripping force. The Tri-Grip®Backup provides exceptional gripping capabilities with either Eckel True Grit® dies or Pyramid Fine Tooth dies. The hydraulic backup is suspended at an adjustable level below the power tong by means of three hanger legs and allowing the backup to remain stationary while the power tong moves vertically to compensate for thread travel of the connection.

Eckel offers several models of torque control systems that are used to monitor the torque turn values when making up tubular connections (Tubing, Casing, & Drill Pipe). Any flaws in the make-up process will be readily shown in a graph.

Manufacturer of oil field and gas well equipment. Tubing, casing, drill pipe and riser hydraulic power tongs are available. Standard or custom diesel and electric driven hydraulic power units are also offered. Tong options include torque control system, door interlock, wrap-around dies, integrated hydraulic backups, case handles, tong straps, motor port relief valve and finger guard protection are provided. Suitable for oil or gas drilling, well completion and servicing applications. Secondary services include assembly, engineering, welding, cutting, heat treating, machining, testing and inspection. Serves oil and gas industries. CE certified. Made in the USA.

Established in 1958, Eckel is globally recognized as the leading manufacturer of hydraulic power tongs and hydraulic power units for the world’s oil and gas industries. We offer a full line of hydraulically operated drill pipe tongs, casing tongs, tubing tongs, hydraulic backups, hydraulic power units, and tong positioning equipment. Eckel delivers a comprehensive range of tongs from 2-1/16 through 36 in. for the most demanding onshore and offshore environments. Eckel Tri-Grip® backup is an industry standard for reliable make-up and break-out of tubular connections. Eckel’s cutting-edge designs, quality, and rugged durability have won us a world-wide reputation of a first-class product that insures years of trouble free service.

Eckel high-performance tongs operate in some of the toughest operating environments around the world performing drill pipe, casing and work-over activities on onshore and offshore locations. Eckel is highly involved in drilling, well servicing, and work-over operations.

We offer a full range of high quality casing and tubing, drill pipe tongs for use in all types of oil and gas drilling, well completion and well servicing activities. Our tongs have been engineered for the high operational torques today’s that premium connections require. Eckel tongs continue to advance the technology of tool service and setting industry standards.

Sliding heads with wrap-around dies are considered the best choice for thinner wall tubulars where point loading is a concern. The wrap-around dies are symmetrically spaced at all times insuring an equally distributed load on the tubular. A larger gripping surface allows more teeth to come in contact with the tubular.

Our proprietary TRUE GRIT™ dies have set NEW industry standards in handling Corrosion Resistant Allows (CRA) tubular goods. TRUE GRIT™ dies are used on chrome tubulars where reduced die penetration and die marking is desired. TRUE GRIT ™ dies are long lasting 3 times longer than competing technologies and perform better than any steel tooth die when running (SUPER or HYPER) Chrome. Tubular penetration of the TRUE GRIT™ dies is less than half of API allowable surface defect area.

Our renowned free floating Tri-Grip® hydraulic backup provides unparalleled backup performance and is one of the industry’s closest tong mounting backups that minimize pipe bending. The backup utilizes three biting surfaces to insure a secure grip on the tubular to prevent tubular rotation.

Our remotely operated tongs provides a mean to control the tong for make-up and break-out operations. The tong is based upon the standard tong and backup configuration with the exception of hydraulic cylinders on the unit for remote control of the operations of the tong and backup. The functions include the tong door, backing pin, mechanical gear shift, power tong rotation, motor speed and backup gripping. Totally hydraulic with no electrical or electronic devices.

Eckel’s standard diesel or electric power packages at 65 GPM and 2,500 psi (246 LPM / 172 bar) are widely recognized for dependability and long, trouble-free service. Eckel will customize hydraulic power systems in the shortest possible time to meet “nonstandard” requirements for space, fluid flow, auxiliary power, and portability. Diesel driven units are optionally supplied with automatic shutdown systems to prevent engine run away when explosive gases are present. Additional shut downs include engine oil temperature, oil pressure, and fan belt breakage. All controls are either air, mechanical or electrical.

Eckel Manufacturing is committed to maintaining its position as an industry leader of the manufacturing of precision engineered specialty oil field equipment. It is our policy to provide our products at the highest quality that meets our customer’s requirements and demands.

Eckel 7 5/8 HDS-30 Tong When application demand a wide range of sizes, this tong handles pipe sizes 2 3/8 inches all the way to 7 5/8. Built around the 7 5/8 Standard, the 7 5/8 HD provides a thicker rotary gear for more added strength, an additional idler gear, a larger pinion gear, and stronger bearings for load bearing capacity and durability. 7 5/8 HDS CHROMEBOSS: the 7 5/8 HD comes standard with pivot style heads; however, upon ordering can be supplied with slide-heads which is designated as 7 5/8 HDS. the 7 5/8 HDS is part of our CHROMEBOSS series of tongs that is suitable for running corrosion-resistant alloy (CRA) tubulars. Two slide heads in the tong provide a consistent radial load on the tubular, reduced tubular deformation, and when combined with our pyramid fine tooth or True-GritTM wrap-around dies provides excellent gripping capabilities on corrosion-resistant alloy (CRA).

Eclel Established in 1958, Eckel is globally recognized as the leading manufacturer of hydraulic power tongs and hydraulic power units for the world"s oil and gas industries. We offer a full line of hydraulically operated drill pipe tongs, casing tongs, tubing tongs, hydraulic backups, hydraulic power units, and tong positioning equipment. Eckel delivers a comprehensive range of tongs from 2-1/16 through 36 in. for the most demanding onshore and offshore environments, offer a full range of high quality casing and tubing, drill pipe tongs for use in all types of oil and gas drilling, well completion and well servicing activities.

The present invention relates to power tongs commonly used in drilling operations for threadably connecting and disconnecting tubular members. More particularly, the present invention relates to the hydraulic system for operating such a power tong in one of several speed/torque ranges, and to an open throat power tong with improved means for locking and unlocking the open throat tong door.

Power tongs may generally be classified as open throat or closed throat tongs. Closed throat tongs are described in U.S. Pat. Nos. 3,371,562, 3,483,774, 3,550,485, and 3,589,742. Since the rigid tong encompasses the pipe, the closed throat tong resists spreading and is generally capable of achieving high make up and break out torques. The disadvantage of a closed throat tongs, however, is that the tong body cannot be laterally put on or taken off a pipe. Open throat tongs, as shown in U.S. Pat. Nos. 3,021,739, 3,180,186, 3,196,717, and 4,084,453 enable the tong to move laterally with respect to the joint of pipe, and generally include a door latching mechanism for connecting the tong body in the open throat area. A variation of a closed throat tong is shown in U.S. Pat. No. 4,334,444, wherein both the tong body and the rotatable cam ring have pivotable portions for opening to laterally position the tong on the pipe, and both pivotable portions can be locked to approximate closed throat tong rigidity.

It is generally desirable that a power tong be operable at different speed/torque ranges and in both forward (make up) and reverse (break out) directions. Various systems have been devised for enabling a power tong to be operable at high speed/low torque while routinely threading together the joints of pipe, and low speed/high torque while making up the final desired pipe threading torque. U.S. Pat. No. 4,346,629 discloses a commonly used technique for manually shifting gearing of a tong to achieve either low speed or high speed output U.S. Pat. No. 3,635,105 discloses a tong with first and second motors for operating the ring gear, with a clutch driven part either idling along with the first motor or being driven by the second motor. U.S. Pat. No. 4,333,365 discloses a hydraulic system for operating a drive motor at different speed/torque ranges depending upon the activation of a pressure-intensifying or boosting means for selectively increasing the hydraulic fluid pressure to the motor. Finally, Canadian Patent No. 1,088,918 discloses a power tong employing a two-speed hydraulic motor.

The systems described in the above patents may allow both forward and reverse operation of a tong at different speed/torque ranges, but tong operators generally disfavor systems which require operation of a large number of controls. Thus, an operationally simplistic two speed tong may be preferred by an operator over a tong having a complicated drive system allowing for tong operation of various speeds by controlling numerous levers and gauges. Also, drive systems which utilize a mechanical gear shifting apparatus generally require slowdown of the tong prior to shifting, which increases the time required to make up pipe joints. Finally, many of the drive systems described in the above patents are mechanically and/or hydraulically complicated and expensive, and the advantages of a sophisticated tong hydraulic system generally cannot offset the disadvantages encountered if that tong experiences frequent breakdown in the field.

Most open throat tongs employ a door which preferably is both closed and latched (or locked in) before operating the tongs at high torque. Tongs may employ a door actuation mechanism to hydraulically close the tong door, as shown in U.S. Pat. No. 4,084,453. The problems encountered when a tong door is operated at high torque and the door is not properly latched are described in U.S. Pat. No. 4,170,907, which patent also describes a door interlock system for preventing a tong from operating if the door is not fully shut and secure. U.S. Pat. No. 4,334,444 also discloses a door interlock system, and further illustrates a hydraulic cylinder and latch for insuring complete closure of the door.

Tong operators nevertheless frequently do not utilize the door locking mechanism provided on a tong, because the locking of a tong door is another operation in a series of operations which must be rapidly and efficiently performed to make-up or break apart pipe. Also, it is common knowledge among tong operators that an open throat tong will not experience excessive spreading under low torque required in many operations. The door is thus often not closed for low torque operations provided the operators are cautious of the safety hazards associated with operating the tong when the door is open. Certain tongs may be provided a powered door closer, but powered door closing devices may also be a safety hazard to the operator standing in the area adjacent the door. If door interlock systems as described above are employed, operators may bypass the systems to allow more efficient tong operation. Also, the more sophisticated the system in the power tong, the higher the risk that the tong may breakdown in the field, and the more likely that the operator will develop techniques to avoid or bypass the system.

A further disadvantage of prior art tongs is that such tongs generally grip the pipe for rotation over a relatively limited contact area. As shown in U.S. Pat. No. 4,334,444, for instance, many tongs employ two pivotably movable or sliding heads with two elongate dies for each head. U.S. Pat. No. 4,346,629 discloses the usage of somewhat larger area dies in the heads, although these dies may not effectively grip the pipe for rotation without crushing or damaging the pipe.

A power tong is provided employing improved hydraulic circuitry for operating a three-speed tandem fluid motor to achieve forward and reverse hydraulic operation in any of three selected speed/torque ranges. A valve block employing two 4 way/3 position valves is utilized, so that one of three selected tong speeds and either forward or reverse tong operation may be controlled by operating only two valve handles associated with the valve block.

The open throat tong includes drive means for automatically locking closed the pivotable tong door to prevent spreading of the tong. A hydraulic tong latch motor adjacent the tong latch is powered for automatically locking the door when the tong is operated, and automatically unlocking the door when the tong is not being operated. The door may be either manually or automatically opened and closed, but when closed may be automatically locked by the hydraulic latch motor.

The open throat tong according to the present invention may also include a plurality of pivotably movable or slidable heads with an increased composite angle of die engagement with the pipe. Two dies preferably grip the pipe over a composite angle of at least 230° to minimize the likelihood of galling or crushing the pipe.

It is therefore a feature of the invention to provide a tong with a reliable drive means capable of operating in one of at least three selected speeds/torque ranges.

It is a further feature of the present invention to provide a power tong with improved drive means which may be easily and quickly shifted from one speed to another speed by operating a minimum number of controls.

It is still another feature of the present invention to provide an open throat tong with a door latching mechanism for automatically locking the door when the tong is operated.

It is a further feature of the present invention to provide a tong with dies on a plurality of die carriers for effectively gripping the pipe over a large composite angle without crushing or damaging the pipe.

FIG. 1 depicts a power tong 10 for making up and breaking apart threaded tubular members, such as drill pipe, casing, or tubing. The tong 10 is of the open throat type, with a ring member 12 and a cage plate assembly 14 both including open throat portions so that the tong may be laterally moved on and off a string of pipe. The basic operation drive gearing of the tong are described in U.S. Pat. No. 4,084,453, which is hereby incorporated by reference. For the present, it should be understood that the drive means of the tong acts to rotate the ring 12 relative to the cage plate 14, causing a pair of dies 16 to come into gripping engagement with the pipe, and that thereafter the partial ring 12 and cage plate 14 may be driven in unison to rotate or thread an upper pipe relative to a lower pipe.

The drive means according to the present invention comprises a vane-type tandem hydraulic fluid motor. Although manufactured as a single unit, the tandem motor structurally and functionally may be understood as both a medium speed hydraulic motor 18 and a high speed hydraulic motor 20 mechanically connected by a common drive shaft so that both motors locate in unison. Motors 18 and 20 may be powered by a skid-mounted hydraulic unit (not depicted) which supplies pressurized hydraulic fluid to the tong through conduit 28. Fluid is returned via line 29 to a tank (not shown) associated with the hydraulic unit.

The open throat tong 10 is shown with door 40 in the partially open position. Door 40 is pivotally connected to the rigid body of the tong at 42, and when properly locked, the door acts to prevent "spreading" of the tong in the area of the open throat under high make up or break out torques. Many tong operators prefer that the door be manually opened and closed, since the operator is generally in the vicinity of the tong door when being placed on or taken off a pipe, and since a powered door closure may be a safety hazard. Also, allowing for manual closure of the door allows an operator to operate the tong at low torque when the door is open, and thus the operator need only close the door when high torque is required. If a power door closure is desired, however, hydraulic cylinder 44 may be provided between the tong body and the door. Suitable cylinder-type door closure devices are more fully described in U.S. Pat. Nos. 4,084,453 and 4,334,444, which are hereby incorporated by reference.

The automatic door lock device of the present invention comprises pin 46 rotatably mounted to the tong body in a position for latching the door in the closed position. Pin 46 may be connected to an adjacent hydraulic motor 48 by gears 50 and 52, so that motor 48 acts to latch or lock the door in the closed position and unlatch the door so that the door subsequently may be opened to move the tong laterally on or off the pipe. The output torque from motor 48 achieves a mechanical advantage through gears 50 and 52, since gear 52 has approximately twice the diameter of gear 50.

Referring to FIG. 2, a simplified hydraulic circuit is shown according to the present invention, with components similiar to those previously mentioned hereinafter noted by the same reference number. A hydraulic unit or pressurized source 60 may provide hydraulic fluid to the tong through line 64, and the maximum hydraulic fluid pressure in line 64 would normally be within the range of from 1800 psi to 3000 psi. Restrictions in the valve block 22 keep a back-pressure, e.g. 280 psi, in line 64 even when the valve block is in a "free wheeling" or center condition. Valve block 22 may be a single unit with a single input line and a single output line to the valve block, but functionally is composed of valve spools 70 and 72 in parallel, with flowline 66 providing fluid pressure to valve spool 70, and flowline 68 similarly providing fluid pressure to valve spool 72. Drain lines 67 and 69 from the valve block feed to common drain line 75 which flows to tank 76.

As previously indicated, the high speed motor 20 and the medium speed motor 18 are mechanically connected in tandem so that both motors rotate simultaneously. The motors may thus be provided with a common drive shaft 19 which rotates the cartridges of both motors simultaneously. Suitable tong gearing is shown in U.S. Pat. No. 4,084,453, and is shown representatively in FIG. 2 as gear 74 which directly drives the ring member 12. Suitable vane-type tandem fluid motors are manufactured by Abex/Denison and are described in their service literature bulletin SFM-M4DC(Rev.A), which bulletin is hereby incorporated by reference. For the tong shown in FIG. 1, C cartridge code 043 for the high speed motor 20 and D cartridge code 102 for the medium speed motor 18 may be used. Suitable valve blocks 22 according to the present invention are manufactured by Commercial Sheering, Inc. and are described in the brochure entitled "A20/A35 Directional Control Valves" hereby incorporated by reference into the present case. The apparatus as shown in FIG. 1, a suitable valve block is sold under the designation A20CA128MA53MA 53Z16.

FIG. 3 depicts a side view, partially in cross-section, of a door 40 and a suitable valve latch mechanism according to the present invention. The door 40 comprises upper and lower door plates 114 and 116 spaced respectively above and below tong body plates 102 and 104. The door pivots about pin 42 rotatably mounted to the tong body plates. Upper bushing 106 is secured by nut 108 threaded to the pin 42, and lower bushing 110 is similarly secured by nut 112. Suitable spacers 107 may be provided between the nuts and the plates 114 and 116.

FIG. 3 illustrates that block 128 mounted to the door may be spaced between tong plates 102 and 104 and aligned for receiving pin 46. Pin 46 is rotatably mounted to the tong body at the opposite side of the tong throat from pin 42. Bushing 120 is provided between the upper tong plate 102 and the pin 46. Nut 122 may be threaded to pin 46 and is secured for rotation with the pin 46 by a removable rivet 121, so that pin 46 may be manually rotated by a wrench applied to nut 122. Relatively thin bushing 124 is provided between the lower tong plate 104 and pin gear 52, which is keyed to the pin and secured by a snap ring 126. Hydraulic motor 48 is mounted between the tong plates and adjacent the pin 46, and includes a shaft extending downward through the lower tong plate 104 with gear 50 affixed thereto. Hydraulic motor 48 thus rotates gear 50, which meshes with gear 52 to obtain rotation of the shaft 46.

FIG. 4 depicts a cross-sectional view of the tong door and latch mechanism shown in FIG. 3. The top plate 114 and the composite bottom plates 116, 118 may have the same general configuration as the bottom plates 116, 118 shown in FIG. 4. Alternatively, since the bottom plate 118 may be provided below the gears 50 and 52, and the bottom plate 118 could extend outwardly to serve as a guard under the gears 50 and 52.

The relationship of the closed door to the open throat of the tong and the bottom tong plate 104 is also shown in FIG. 4. The door includes a curved vertical plate 132 spaced between horizontal plates 114 and 116, with block 128 welded to the plate 132. Pin 46 includes recessed surfaces 138 and 140, and it should be understood that the pin would be rotated 90° from that position depicted in FIG. 3 so that the slot portion 130 of block 128 may receive the pin. Thereafter, the pin may be rotated to the position as shown in FIG. 4, so that the curved outer surfaces of the pin engage the inner surfaces of the slot 130. When the pin is in the position shown in FIG. 4, the door is latched or locked in place. The distance between pin 42 and pin 46 is thus fixed by the rigid door, so that substantial "spreading" of the open throat of the tong cannot occur. Although not necessary, the slot 130 of the door may include stop 142, which is discussed subsequently.

Referring particularly to FIGS. 1 and 2, the operation of the tong will now be described. By moving one or both of the handles 34 and 36 from their center position, fluid will flow to one or both motors 18 and 20, thus rotating the tandem motor in one of three selected speeds/torque ranges and in either the forward or reverse directions. The tandem motor drives a gear train (representatively shown as gear 74), which drives partial ring 12. Each valve assembly 70 and 72 is spring biased in the neutral position, so that fluid to the valves will be dumped back to the return if both valves are in the center position. Thus, the operator need only control one or both of the handles 34 and 36 to achieve the desired speed and directional rotation for the partial ring 12.

Referring particularly to FIGS. 2 and 4, the operation of the door latch mechanism of the invention will now be described. The door 40 normally should be closed prior to operating the tong, and may be moved in the closed position since pin 46 would normally be rotated for receiving the slot 130 in block 128. Prior to closure, the handles 34 and 36 would normally be in their center free wheeling position, since the gear 12 is not rotating. At this time, some nominal back pressure, e.g., 280 psi, may be in line 78. Relief valve 94, which may be set at 300 psi, would be closed so that no fluid pressure was applied to motor 48.

After rotating the pin 90°, the motor 48 may be stalled by engagement of gear finger 125 secured to gear 52 with stop 127. Alternatively, the door could be provided with stop 142, so that the pin 46 would engage the stop 142 after rotating 90° to stall out the motor 48. Motor 48 need only be a low horsepower hydraulic motor capable of generating several foot pounds of torque. A suitable motor 48 is sold by Barnes Pumps under Model 1300098, referenced on page 83B of Catalog 365-U, entitled "Fluid Power Designer"s Manual" by Womack Machine Company. Alternatively, a pivotable hydraulic cylinder, a pneumatic motor, or other drive means could be used to rotate the latch pin. It is a feature of the invention, however, that a drive means and hydraulic circuit be provided in the tong for automatically locking the closed door to prevent tong spreading, by merely operating the controls necessary to obtain the desired rotation of ring 12.

Thus, the door 40 is automatically locked and unlocked without requiring action by the tong operator aside from normally operating the hydraulic handles 34 and 36. If the door were not closed prior to operating the tong, the same hydraulic sequence of events would occur so that pin 46 would be rotated, although the block 128 would not be in a position to lock the door closed.

FIG. 5 depicts a simplified top view of a portion of the tong shown in FIG. 1 with the upper cage plate removed for clarity. According to the present invention, the tong may be provided with either pivotable heads 158 which rotate about pivot pin 160, or with sliding heads as depicted in U.S. Pat. No. 3,390,323. Partial ring 12 includes neutral cam surfaces 152, forward cam surfaces 154, and reverse cam surfaces 156. Suitable camming surfaces are more particularly described in U.S. Pat. No. 4,084,453. For the present, it should be understood that a roller 162 is connected with each head and engages the camming surfaces when the ring 12 rotates relative to the cage plate, causing the dies 16 to come into gripping engagement with the pipe.

The dies which engage the pipe preferably function to grip the pipe under high torque without crushing or damaging the pipe. Poor gripping engagement of the dies with the pipe may cause the dies to excessively score and damage the pipe, since the dies may rotate relative to a poorly gripped pipe. On the other hand, excessive biting force transferred to the pipe by the dies may crush or collapse the pipe, especially if the force is applied in concentrated locations or a substantial non-radial force is applied to the pipe.

According to the present invention, the open throat tong is provided with a plurality of dies 16 which come into arcuate gripping engagement with the pipe over a composite angle greater than that provided in the prior art to more uniformly grip the pipe. The depth of each of the dies 16 will generally be determined by the spacing between the cage plates, and generally is in the range of 21/2 to 6 inches. Each of the dies 16 preferably engages the pipe through an angle 166 of at least 115° and preferably at least 120°, so that a composite gripped angle between 240° and 250° is possible. If a 245° composite gripped angle is obtained from the dies, the spacing 168 between the back of the dies will generally be quite short, e.g., 3/4" or less. As shown in FIG. 5, each of the dies 16 includes dovetail portion 164, so that each die may be easily secured into its respective head.

When operating the tong as shown in FIG. 1, the selected speed/torque ranges for the tong will generally depend on the maximum diameter of the pipe the tong is designed to handle. Preferably, however, a ratio of at least 2:1 is obtained between the high speed and the medium speed operation of the tong. For a tong as shown in FIG. 1 capable of handling a maximum 41/2" diameter pipe, the high speed motor preferably will rotate the gear 12 and therefore the pipe in the range of 80-120 rpm. The pipe may rotate at medium speed in the range of between 40-50 rpm, and may rotate in the range of between 30-40 rpm at the low speed range. Assuming 2000 psi pressure is applied to the tandem motor as described herein from a 40 gpm gear-type pump, the above described tong may effectively stall under high speed at approximately 1000 pounds, under medium speed at approximately 3000 pounds, and under low speed at approximately 5000 pounds. Thus, it may be seen that in the low speed, the composite motor allows the torque to be substantially increased compared to either the high speed torque or the medium speed torque so that the desired high gripping torque for making up and breaking apart the pipe joint may be easily achieved. It should be understood that the terms high speed, medium speed, low speed, low torque, medium torque, and high torque with respect to the main drive motors are each relative terms. As such, a medium speed/medium torque motor is defined as any motor having a lower speed and a higher torque than a high speed/low torque motor, and a low speed/high torque motor is defined as any motor having a lower speed and a higher torque than a medium speed/medium torque motor.

Numerous modifications from the illustrative embodiments disclosed herein may be made without departing from the spirit or scope of the invention. For example, the tandem drive motor described herein may be pneumatically powered instead of being hydraulically powered. Also, more than two fluid motors could be coupled together to form a multiple section fluid motor with a common drive shaft to achieve more than three possible motor speeds, although additional operator handles would then also be required. Further, the automatic door latch mechanism disclosed herein could be employed on any open throat tong having a hinged door. These and other modifications of the invention will be apparent to those skilled in the art and are intended to be within the scope of the present invention.