power tong mark 5 supplier

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- DIES FOR PIPE AND TUBING TONGS Filed April 18. 1960 4 Sheets-Sheet 1 CROSS CUT DEPTH TOOTH DEPTH i n N a 3 Q 4 L- I 2 M 4 it m E 8 I o PEI-I 21 m m; E 1 Q :0;

u.| l 5* I 5 i" l M 4 l 4 INVENTORS 0.5. MARQUIS 8 J.H. PROVINCE N n v: -n o l o m 2 I I J BY z ,w% r I 7 ATTORNEYS March 1964 D. E. MARQUIS ETAL 3 3 DIES FOR PIPE AND TUBING TONGS Filed April 18. 1960 4 Sheets-Sheet 2 x (PENETRATION CROSS SECTION) INVENTORS D. E. MARQUIS J.H. PROVINCE A 7" TORNEKY March 10, 1964 D. E. MARQUIS E" I"AL 3,

DIES FOR PIPE AND TUBING TONGS 4 Sheets-Sheet 4 Filed April 18. 1960 INVENTORS D.E. MARQUIS J.H. PROVINCE A T TORNEVS United States Patent 3,124,023 DIES FOR PIPE AND TUBING TONGS Duane E. Marquis and John H. Province, Bartlesville,

0kla., assignors to Phillips Petroleum Company, a corporation of Deiaware Filed Apr. 18, 1960, Ser. No. 22,842 19 tllaims. (Cl. 81186) This invention relates to a die for pipe and tubing tongs. In one aspect this invention relates to an improved die which, when employed in pipe and tubing tongs, causes less damage to the pipe or tubing being made up or broken out with the aid of said tongs. In another aspect this invention relates to an improved die for pipe and tubing tongs which die provides maximum contacting surface of essentially the same curvature as the outer circumference of the pipe or tubing to which said die is applied.

The development of new high strength tubing has helped solve many of the problems encountered in the completion of high pressure oil and/ or gas wells. Said new tubings are fabricated from new alloy steels and have a yield strength in the range of API P-105 grade tubing, i.e., 105,000 p.s.i. minimum yield. In said new steels the increase in yield strength is accompanied by a decrease in ductility.

Thus, while said new tubing has solved many of the problems formerly encountered, the use of said new tubing has created problems in the handling of the tubing itself. Handling techniques and equipment employed with old type tubing have proven highly unsatisfactory for the new type tubings. Well operators have thus been faced with the problem of reducing handling damage which has caused many unnecessary failures. As mentioned above, the increase in yield strength of said new steels is accompanied by a decrease in ductility. The stress in a ductile steel is able to redistribute itself around discontinuities and damaged areas, but in a non-ductile brittle material less stress redistribution occurs, resulting in a concentration of stress in the vicinity of any damage. These characteristics of the new alloys require more care in the handling of the less ductile tubing. For example, in the operation of high pressure wells employing said new tubings, brittle failure at the die mark has been encountered in a number of instances; tubing failures have occurred during the normal operation of wells where the rupture passed directly through the die marks; and stress corrosion failures have occurred in the region of the die marks.

Thus, it has been found that much of the handling damage is caused by the dies in the tongs employed in making up and breaking out joints of tubing. As a result of extensive field, laboratory, and experimental tests we have invented a new die for pipe and tubing tongs, which die reduces damage to said pipe or tubing to the minimum, but yet provides efiicient safe handling in making up and breaking out strings of pipe or tubing.

An object of this invention is to provide an improved die for pipe and tubing tongs. Another object of this invention is to provide an improved die for pipe and tubing tongs which provides maximum tooth contacting areas and minimum tooth penetration, thereby resulting in the elimination or mitigation of tong die damage. Another object of this invention is to provide an improved die which is less subject to clogging. Still another object of this invention is to provide an improved die which is easier to clean. Another object is to provide an improved power tong adapted to be employed with said die. Other aspects, objects and advantages of the invention will be apparent to those skilled in the art in view of this disclosure.

Thus, according to the invention there is provided a die for pipe and tubing tongs, said die comprising: a bar-like body having a concave working face provided with a plurality of buttressed teeth thereon; said teeth having a substantially triangular cross section and being arranged in from 5 to 9 spaced apart parallel rows per inch of said concave working face; each of said teeth having an apex length or contacting surface within the range of to 4 inch; said teeth being spaced apart in said rows a distance within the range of from A to inch; and said apexes of said teeth providing an arcuate contacting surface having a curvature essentially the same as the outer circum ference of the pipe or tubing with which said die is to be employed.

We have found said combination of factors or elements to be essential in reducing die damage to the minimum. The concave working face provides the curved foundation necessary for realization of maximum advantage from the other elements of the combination. The buttress type teeth of substantially triangular cross section provide maximum tooth strength which is highly desirable when employing maximum applied torque. Said buttress type teeth also provide a better initial bite which is particularly desirable when working with dirty or scaly tubing. The specified spacing of the rows of teeth, the specified tooth apex or contacting length, and the specified spacing of said teeth in said rows all cooperate to provide an interrupted marking pattern. Said interrupted marking pattern is essential in order to avoid a continuous or elongated marking pattern which causes a concentration of immediate damage and sets up a concentration of stress forces which lead to future failures. The arcuate contacting surface of essentially the same curvature as the curvature of the outer circumference of the pipe or tubing with which the die is to be employed spreads the applied forces over the maximum area and insures that each tooth will bear its share of said applied forces and reduces individual tooth penetration to the minimum.

Each of said elements is critical to the combination, within the above specified limits, in that each cooperates with the others to provide a unitary end result, i.e., a die, which when employed in a pipe or tubing tong and applied to a pipe or tubing, will cause minimum damage to said pipe or tubing.

As used herein and in the claims, unless otherwise specified, the expression arcuate contacting surface having a curvature essentially the same as the outer circumference of the pipe or tubing with which said die is to be employed refers to the curved surface presented by the apexes or contacting surfaces of the die teeth. Said contacting surface is of course an interrupted surface. The curvature of said surface can be further defined in terms of radius of curvature. For example, consider a nominal two inch tubing having an outside diameter of 2.375 inches plus or minus 0.031 inch, the usual tolerance to which such tubing is manufactured. The radius of curvature of the outer wall of said tubing is 2.375/ 2 or 1.1875 inches, which would be the radius of curvature R (see FIGURE of the arcuate contacting surface provided by the tooth apexes or contacting surfaces of a die fabricated in accordance with the invention and intended to be employed with a tubing or pipe having an outside diameter of 2.375 inches.

FIGURE 4 is a diagrammatic view, partly in cross section, illustrating a conventional tubing power tong which has been modified to employ the dies of the invention.

FIGURE 5 is an enlargement of the gripping mechanism of the power tongs of FIGURE 4 and illustrates the relationship between the teeth of the die of the invention and the circumference of a pipe or tubing.

Referring now to said drawings the invention will be more fully explained. In said drawings like reference numerals are employed to designate like elements. FIG- URES 1, 2 and 3 illustrate one presently preferred specific embodiment of a die in accordance with the invention and which is particularly adapted to be employed with a nominal 2 inch tubing having an actual outside diameter of about 2.375 inches Said die comprises a bar-like body 20 having concave working face 21 provided with a plurality of buttressed teeth 22 superimposed thereon. Said teeth have a substantially triangular cross section, and in the particular embodiment illustrated are arranged in 11 parallel rows spaced apart about inch. Each of said teeth has an apex or contacting surface 23 (sometimes referred to as tooth length) of about inch. Said teeth are spaced apart in said rows a distance of about /8 inch at their apexes to provide about 17.5 inches of total lineal contacting surface. Thus, said 11 rows of teeth provide a contacting surface consisting of 187 points of contact. Said contacting surface provided by said teeth apexes or contacting surfaces is an arcuate contacting surface having a curvature essentially the same as the outer circumference of the pipe and tubing with which said die is intended to be employed, in this specific embodiment a 2% inches O.D. tubing. In FIGURE 1 the vertical numbers 1 to 11 designate row numbers.

In the specific embodiment illustrated the back face 24 of the die is slightly convex and the side faces 26 are tapered. The amount of curvature on said convex back is not critical so long as it is not large enough to cause instability. In the die illustrated said curvature is about equal to the curvature of a circle having a radius of 12 inches. If desired, said back face 24 can be fiat. Said tapered sides are tapered at an angle of about 15 degrees. Said tapered sides are advantageous in holding the dies of the invention in the grooves provided in the bushing and jaw of the tongs. Said convex back is provided to enable or provide a slight rocking motion within said grooves when the dies are first brought into contact with the pipe or tubing and thus aid in fitting or placing the die to the tubing or pipe with which it is to be employed. Opening 25 is provided for convenience in stringing the dies for temporary storage as when a string or wire is passed through a set of dies to keep them separate from other similar dies. The specific embodiment of the die of the invention illustrated in FIGURES 1, 2 and 3 has an overall length of 3 /8 inches and a width at the base of 2 inches.

Referring now to FIGURE 4, there is illustrated a conventional power tong which has been modified to accommodate the dies of the invention. Said power tong is of the general type illustrated in US. Patent 2,618,467 issued to C. A. Lundeen on November 8, 1952. Said power tong comprises a bushing 27 and a jaw 28 which are part of an inner ring assembly 29 which is actuated by an outer ring assembly 31. Said bushing 27 is provided with two adjacent tapered grooves 34 and 36 which contain dies A and B fabricated in accordance with the invention. Said dies are held in place in said bushing and said jaw by means of cotter pins 35 at the top and bottom (not shown). The sides of said tapered grooves 34 and 36 are tapered at approximately the same angle as the side faces of said dies A and B but said grooves are slightly wider than said dies A and B so as to provide room for said dies A and B to rock on their convex back faces in said grooves when said jaw 28, containing die J, is brought into contact with a tubing (not shown). Said bushing 27 is stationary in said inner ring assembly 29 while said jaw 28 is hinged at the point 32 so that as said outer ring assembly 31 rotates in the direction indicated by the arrow with respect to said inner ring assembly, the roller 33 will roll along the cam surface of said jaw 28 and cause die I to be moved into contact with a tubing or pipe (not shown). Power tongs of the general type here illustrated are well known to those skilled in the art and no further explanation of their operation is believed necessary. Further details concerning the operation of power tongs of this general type can be found in said Patent 2,618,468.

FIGURE 5 illustrates more clearly the relationship between the dies A, B, and I, fabricated in accordance with the invention, and a tubing which has been placed in the power tongs and jaw 28 closed. It will be noted that the contacting surface provided by the teeth of each of said dies A, B and J covers an area of the tubing equivalent to about 70 degrees of the circumference of said tubing, or a total area of 210 degrees for three of said dies. In the practice of the invention it is preferred that each die cover an area of the tubing which it contacts equivalent to at least about 60 degrees of the circumference of said tubing. This feature of the invention, i.e., the apexes of the teeth of said dies providing an arcuate contacting surface having a curvature essentially the same as the outer circumference of the pipe or tubing with which said dies are employed, provides an important advantage of the invention.

Referring to said Patent 2,618,468 it will be noted that each of the dies 93, 94, and 95 has a maximum contact surface of only about 20 degrees on the surface of the pipe or tubing. Said dies 93, 94 and 05 in FIGURES 5 and 6 of said Patent 2,618,468 are conventional flat face dies provided with four teeth running the entire length of the die. Due to the flat faces of said standard die and the curvature of the tubing, only one of said teeth and perhaps a trace of a second tooth makes contact with the tubing. Since each die is approximately 3% inches long, this results in a total of only about 17 lineal inches of contact, all concentrated in three or more continuous die marks. This concentration of the die marks is highly undesirable, particularly with the new type tubings, due to the stress patterns developed.

The invention is of course not limited to the die having the specific dimensions or the specific tooth marking patterns discussed above in connection with the drawings. For example, in another embodiment of the invention, illustrated in FIGURES 7 and 8, the die is essentially the same as that discussed above except that said second embodiment die is provided with only 9 rows of teeth having 153 points of contact providing 14.34 lineal inches of contact on each die, or a total of 459 points of contact amounting to a total of 43.03 lineal inches of contact when three dies are employed in combination. The teeth in this embodiment of the invention have an apex angle of about 68 degrees. This last mentioned embodiment of the die of the invention allows for wider spacing (about inch) between the rows of teeth which improves the self-cleaning features of the dies of the invention. Said last disclosed embodiment of the invention is thus preferred when working with dirty or scaly tubing.

The improved die of the invention is most advantageously employed in connection with the smaller sizes of high pressure tubing, such as nominal 2, 2 /2 and 3 inch tubings, having outside diameters of 2.375, 2.875 and 3.5 inches respectively, fabricated from the new alloys discussed above and which are therefore most subject to handling damage. However, said dies can also be employed with great advantage when making up larger sizes of pipe and tubing, e.g., up to and including nominal 7 inch pipe or tubing, and larger.

Stated another way, the improved dies of the invention can be fabricated with the buttress type teeth arranged in from 5 to 9 spaced apart parallel rows per inch of concave working face. Each of said buttress type teeth would have an apex angle within the range of about 45 to 90 degrees, preferably within the range of 65 to 75 degrees. The apex angle of the teeth will vary with the other dimensions, e.g., number of rows of teeth. Each of said teethwould have an apex length or contacting surface 23 within the range of about to inch. Each of said teeth would have a longitudinal depth within the range of 0.01 to 0.1 inch and a cross cut depth within the range of 0.03 to 0.07 inch. Said teeth would be spaced apart in said rows a distance within the range of about to about 4 inch. The apexes of said teeth, as in the previously described emlbodiments, would provide an arcuate contacting surface having a curvature essentially the same as the outer circumference of the pipe or tubing with whcih the die is to be employed.

The candidate dies were installed in a conventional power tong similar to that illustrated in FIGURE 4 herein and that illustrated in said Patent 2,618,468. The bushing and jaw of said power tongs were modified where necessary to accommodate the candidate dies.

teeth per row, die length 3% inches, die width 1% inches, tooth apex length 0.104 inch, total lineal contact 1.35 inch per row. Buttress type teeth, 7 rows of teeth (the 4340 2,500 0.005 0.0364 0.0608 0.0972 0.1622

same as No. 1 otherwise). See above 9 chrome 4,200 0.0371 0. 0160 0. 052 0. 0689 0.100 See above. 9chrome 4,200 0.0586 0.0216 0.0472 0.0088 0.1274 Same as No. 1 except die had 4 rows of teeth 4340 4, 400 0. 0364 0.0148 0.0162 0.031 0. 0074 and a width of 1 inch. Same as No. 2 except die had 4 rows of teeth 4340 4, 400 0.0614 0. 0649 0. 0628 0. 1277 0. 1801 and a width of 1 inch. Symmetrical type teeth, 12 rows of teeth, 4340 2, 500 0.0461 0.036 0.024 0.060 0.1061

The data given in the above Table I show that the total penetration cross section (X for dies 1, 3, and 5 having symmetrical type teeth were much less than for dies 2 and 4 having buttress type teeth. These data show that a die having symmetrical type teeth develops less penetration cross section for the same applied torque than does a die having buttress type teeth. Thus, from the standpoint of penetration cross section, a die having symmetrical type teeth would be preferred.

Table 11 Average Tooth Penetrationmils Die No. Tooth Type Bushing Dies J aw Die, Die I Die A Die B 1 Symmetrical 9. 2 6. 4 4. 3 2 Buttress. 13 S. 0 12. 3 3 Symmetrical. 9 5. 5 6 4 Buttress l5. 2 24 15. 5 5 Symmetrical 3.5 3 2.5

EXAMPLE II On the basis of observations during the tests described in the above Example I three dies having symmetrical type teeth and meeting the above determined total penetration cross section requirement of 0.0886 sq. in. for dies having symmetrical type teeth were fabricated. It was desired to reduce the average tooth penetration to 3 mils (0.003 inch) if possible. In order to fit into the power tongs being employed the overall dimensions of each die were set at a length of 3% inches and a width of 2 inches. A tooth contact length of inch with inch space between the teeth in the row was chosen. For a die 3% inches in length this will permit 30 teeth per row or a total contact area of 0.936 inches per row of teeth.

Since the total penetration cross section of 0.0886 sq. in. for dies with symmetrical type teeth is to be met, and since the above distribution analysis showed the jaw die I does /2 the work when the dies have symmetrical type teeth, then Three dies were fabricated with 16 rows of 30 teeth each with the rows being spaced about inch apart. Said teeth were superimposed on a concave working face with the apexcs of the teeth providing an arcuate con- 9 tacting surface having a curvature essentially the same as the outer circumference of a 2.875 inch O.D. tubing.

Said dies were then heat treated to impart a Rockwell C hardness of 61-63 to the teeth surfaces. When tested in a power tong on 2.875 inch O.D. tubings made of 4340 steel and tubings made of 9 chrome steel having Rockwell C hardnesses in the range of 25 to 32, and employing from 2500 to 5000 ft. lbs. of applied torque, the dies slipped and the die teeth acted much in the manner of a cutting tool.

EXAMPLE III On the basis of observations during the tests described in the above Example I three dies having buttressed type teeth and meeting the above determined total penetration cross section requirement of 0.1595 sq. in. for dies having buttress type teeth were fabricated. The average tooth penetration was set at 3 mils (0.003 inch), die length at 3% inches, and die width at 2 inches for the same reasons as in Example II. A tooth contact length of inch with 4 inch space between the teeth in the row was chosen. For a die 3% inches in length this will permit 17 teeth per row or a total Contact area of 0.1591 inches per row.

Since the total penetration cross section of 0.1595 sq. inch. for buttress type teeth is to be met, and since the above distribution analysis showed that all three dies A, B, and J do about equal work when the dies have buttress type teeth, then (115935 =53.2 lineal inches Total contact= all 3 dies) Number of contact rows= Number of contact rows per die= g =lll Three dies were fabricated with 11 rows of 17 teeth each with the rows being spaced about inch apart. Said teeth were superimposed on a concave working face with the apexes of the teeth providing an arcuate contacting surface having a curvature essentially the same as the outer circumference of a 2.375 inch 0. D. tubing.

Said dies were then heat treated to impart a Rock well C. hardness of 60-61 to the teeth surfaces. When tested in a power tong on 2.375 inch O.D. tubings made of 4340 steel and tubings made of 9 chrome steel having Rockwell C hardnesses ranging from 25 to 32, and employing from 2500 to 5000 ft. lbs. of applied torque, the action of the dies was satisfactory in every respect.

The die described immediately above is the die illustrated in FIGURES 1, 2 and 3. In numerous subsequent tests of this die on various types of tubings and employing from 2000 to 3000 ft. lbs. of applied torque on makeup, the tooth penetration has averaged from 2 to 4 mils; when employing from 2000 to 5000 ft. lbs. of applied torque on break-out, the tooth penetration has averaged from 4 to 6 mils. Considering the severity of use, the die life has been entirely acceptable.

1. A die for pipe and tubing tongs, said die compris ing: a bar-like body having a concave working face provided with a plurality of buttressed teeth thereon; said teeth having a substantially triangular cross section and being arranged in from 5 to 9 spaced apart parallel rows per inch of said concave working face; each of said teeth having an apex length within the range of from to inch; said teeth being spaced apart in said rows a distance within the range of from to 4 inch; and said apexes of said teeth providing an arcuate contacting surface having a curvature essentially the same as the outer circumference of the pipe or tubing with which said die is to be employed.

2. A die for pipe and tubing tongs, said die comprising: a bar-like body having a concave working face provided with a plurality of buttressed teeth thereon; said teeth being arranged in from 5 to 9 spaced apart parallel rows per inch of said concave working face; each of said teeth having an apex angle within the range of 45 to degrees, an apex length within the range of to inch, a longitudinal depth Within the range of 0.01 to 0.1 inch, and a cross cut depth within the range of 0.03 to 0.07 inch, with one of said dimensions for said longitudinal depth and said cross-cut depth being less than the other said demension; said teeth being spaced apart in said rows a distance within the range of to A1. inch; and said apexes of said teeth providing an arcuate contacting surface having a curvature essentially the same as the outer circumference of the pipe or tubing with which said die is to be employed.

5. A die for pipe and tubing tongs, said die comprising: a bar-like body having a concave working face provided with a plurality of buttressed teeth thereon; said teeth being arranged in from 8 to 12 parallel rows spaced from 0.12 to 0.18 inch apart; each tooth having an apex length within the range of from to inch; said teeth being spaced apart in said rows a distance within the range of from to 4 inch to provide from 12 to 20 inches total lineal contacting surface and said apexes of said teeth providing an arcuate contacting surface having a curvature essentially the same as the outer circumference of the pipe or tubing with which said die is to be employed.

6. A die according to claim 5 wherein: said teeth are arranged in 11 parallel rows spaced about inches apart; each tooth has an apex length of about V inch; said teeth are spaced apart in said rows a distance of about /s inch to provide about 17.5 inches total lineal contacting surface; and said apexes of said teeth provide 1 1 an arcuate contacting surface having a curvature essentially the same as the outer circumference of a 2% inch O.D. tubing.

7. A die according to claim 6 wherein each of said teeth has an apex angle within the range of from 65 to 75 degrees, and the number of teeth in each of said rows is 17.

8. A die according to claim 5 wherein: said teeth are arranged in 9 parallel rows spaced about inch apart; each tooth has an apex length of about inch; said teeth are spaced apart in said rows a distance of about A; inch to provide about 14.35 inches total lineal contacting surface; and said apexes of said teeth provide an arcuate contacting surface having a curvature essentially the same as the outer circumference of a 2% inch O.D. tubing.

9. A die according to claim 8 wherein each of said teeth has an apex angle within the range of from 65 to 75 degrees, and the number of teeth in each of said rows is 17.

10. A die according to claim 5 wherein said teeth are arranged in from 9 to 11 parallel rows spaced from about 12 to about inches apart; each tooth has an apex length of about inch; and said teeth are spaced apart in said rows a distance of about /s inch to provide from about 14.35 to about 17.5 inches total lineal contacting surface.

References Cited in the file of this patent UNITED STATES PATENTS 795,486 Cornell July 25, 1905 1,518,755 Purvis Dec. 9, 1924 1,532,469 Black Apr. 7, 1925 1,547,543 Welty July 28, 1925 1,554,677 Johnson et al Sept. 22, 1925 1,844,616 Whiton Feb. 9, 1932 1,908,421 Heggem May 9, 1933 1,919,468 Jones July 25, 1933 2,098,369 Baash Nov. 9, 1937 2,214,241 Baxendale Sept. 10, 1940 2,520,448 Abegg Aug. 29, 1950 2,609,720 Barnard Sept. 9, 1952 2,697,957 Yoder Dec. 28, 1954

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).

Stops 124 hold jaws 120 and prevent sideways insert movement. The stops 124 may be welded to the jaw or otherwise secured. Removable bolts may be used instead of the stops 124. The stops 126 perform the same functions. A right angled member 127 (FIG. 3C) maintains a roller 135 rotatably in place in holes 123, 125. Holes 129 either receive a projection of an insert to maintain the insert in place or a pin extends through the hole 129 into the insert to accomplish this.

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).

An insert 420 has dovetail keys 421 received and held in corresponding slots 422 of the holder 414. The insert 420 is shown as a single unitary insert but a plurality of individual inserts (either abutting or spaced apart) may be used secured to the jaw body 415.

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.

A bleed valve 620 functions to selectively release pressure from the pre-load cylinders following make-up or break-out. A pump 630 pumps hydraulic fluid from the reservoir 608 to a line 631, in a line 632 to the accumulator 610, in a line 633 to the directional control valve 602, and in lines 634 and 635 to (and from) the pre-load cylinders 508 and 510. A check valve 638 in a line 637 from the reservoir 608 prevents fluid from flowing back into the reservoir. A check valve 639 in the line 631 insures that the pump 630 pumps fluid only from the reservoir and prevents fluid from the cylinder 508, 510 and/or from the accumulator 610 from flowing back to the pump 630 and to the reservoir 608.

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. 5B, the system 500 is being pre-loaded for gripping a tubular 650. Fluid is applied into the pre-load cylinder 508 to overcome a spring force of a spring 551 and allow a piston 552 to move the movable jaw 506 away from the fixed jaw 505. The directional control valve 602 is set to permit fluid to be pumped in the line 634 to the pre-load cylinder 508.

Simultaneously fluid is flowing out in line 635 from the pre-load cylinder 510, allowing its spring 553 to urge its corresponding piston 554 inward into the pre-load cylinder 510 thereby pulling the end of the movable jaw toward the fixed jaw 504 and increase the loading of the jaw 506 on the tubular 650.

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.

The jaw assembly 1001 comprises a jaw holder 1002 which is provided with an arcuate recess 1003 which accommodates an arcuate pad 1004 of resilient elastomeric material. A block 1005 of steel is molded into each end of the arcuate pad 1004 as shown. Three thin shims 1006 of metal each having a thickness of about 0.5 mm are positioned on the inner surface of the arcuate pad 1004 and support an insert or gripping arrangement 1007 which comprises a carrier plate 1008 and a friction layer 1009. The carrier plate 1008 has side flanges 1010 and 1011 which clip over the blocks 1005 as shown. The top and bottom of the carrier plate 1008 are tack welded to end plates 1012 and 1013 which are bolted to the jaw holder 1002 by socket screws 1014. The friction layer 1009 comprises a sheet of zircon paper which is bonded to the carrier plate 1008. The carrier plate 1008 is made of sheet steel and is approximately 1.5 mm thick. As such it is quite flexible.

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).

Various modifications to the embodiment described are envisaged, for example the friction layer 1009 could comprise silica paper, carborundum paper, tungsten carbide paper, or diamond paper, the term "paper" as used herein including cloth. If desired the friction layer 1009 may comprise a layer of flexible material, for example metal, having a surface formed with ridges and valleys similar to the surface of a metal file. Such an arrangement is shown in FIG. 15 where the friction layer has been identified by reference numeral 1009". In this embodiment the friction layer could be bonded to the carrier plate. However, it is conceivable that the carrier plate could be dispensed with since the friction layer 1009" is capable of redistributing circumferential forces itself. If desired the blocks 1005 are disposed with, particularly if the arcuate pad 1004 is made from a relatively firm resilient elastomeric material. The shims 1006 may be dispensed with although they help prevent the resilient elastomeric material of the arcuate pad 1004 being extruded under pressure.

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.

At this time the upper length of casing 2128 is lowered into the proximity of the guide 2117. As shown in FIG. 25 the lower end of the upper length of casing 2128 is provided with a pin 2129 which is tapered.

As the upper length of casing 2128 is further lowered the pin 2129 enters the guide 2117 and is centered thereby. It then passes downwardly until it enters the socket 2125 as shown in FIG. 26.

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.

Each jaw unit 3102 comprises a jaw holder 3105 on which is mounted a jaw 3106 the radially inner surface of which is provided with a plurality of gripping elements 3107 which together define a gripping surface which is substantially arcuate.

The jaw holders 3105 are provided with an arcuate track 3108 and the jaw 3106 is slidably mounted on the arcuate track 3108 so that the jaws 3106 can slide along the arcuate track 3108 relative to the jaw holder 3105.

Thus, when the jaw holders 3105 are in the position shown in FIGS. 31 to 37 the jaws 3106 can slide along an arcuate path having a center of curvature at a point 3109 which is radially inwardly of the gripping surface of the gripping elements 3107 but to one side of the center 3110 of the rotary 3100.

The tubular 3111 is then moved towards the opening 3112. As it moves it engages the jaws 3106 and displaces them in the direction of the arrows 3115 so that they occupy the position shown in FIG. 36 which is identical to FIGS. 31, 32 and 37.

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 slo