Abstract:
In one aspect, an apparatus for aligning tubulars is provided, comprising at least one guide, a tong, and a backup unit, wherein the guide is arranged on or between the tong and the backup unit, and wherein the guide is, in use, movable towards and away from the tubular with respect to the backup unit. In another aspect, an apparatus for aligning tubulars is provided, comprising a tong, a backup unit, at least one torsion post arranged therebetween, and at least one guide, the guide mounted on the torsion post. In another aspect, a method for aligning tubulars using the apparatus of the invention is provided, comprising moving the guide towards and away from the tubular with respect to the backup unit.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to an apparatus and a method for aligning tubulars. 
   2. Description of the Related Art 
   During the construction, maintenance and repair of oil and gas wells it is necessary to connect a large number of tubulars, for example lengths of drill pipe or casing. Conventionally the upper end of a tubular is provided with a threaded socket or box whilst the lower end is provided with a threaded pin which is slightly tapered. 
   In practice it is very easy for the pin of one tubular to be incorrectly inserted into the socket of another tubular with the result that the threads on one or both the pin and the socket can readily be damaged. 
   Considerable skill is required to correctly align tubulars and historically this task has been undertaken by a highly experienced rig-hand called a “stabber”. 
   In order to facilitate correct alignment a device known as a “stabbing guide” is frequently used. One such stabbing guide comprises a plastic body member which can be mounted on the socket of a pipe held in slips. The plastic body member has a central passageway the upper part of which defines a funnel which leads into a lower passageway which is concentric with the socket. In use, as the upper tubular is lowered, its pin enters the funnel of the stabbing guide and then travels down the lower passageway into the socket. The stabbing guide (which comprises two semi-circular pieces hinged together around the socket) is then removed and the tubulars are screwed together and tightened to the required torque either by a power tong or a tong assembly comprising a power tong and a backup tong. 
   It has been observed that an accuracy in alignment of approximately 1 mm is required to inhibit problems associated with thread misalignment. 
   PCT Publication Number WO 98/32948, owned by the applicants for the present application, discloses an apparatus for aligning tubulars which apparatus comprises a guide mounted on one of a power tong and a backup tong. 
   It has been observed that the prior art apparatus, although reasonably accurate, is not suitable for multiple uses where accuracy is paramount and with little physical input from rig hands. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention provides an apparatus for aligning tubulars which apparatus comprises at least one guide, a tong and a backup unit wherein said at least one guide is arranged on or between said tong and said backup unit, characterized in that said at least one guide is, in use, movable towards and away from a box of a tubular with respect to said backup unit. The at least one guide may be shaped to act like a funnel in guiding a pin into a box. The guide is moveable in a substantially radial direction towards and away from the centre of the backup unit. 
   Preferably, the apparatus further comprises a piston and cylinder, wherein the at least one guide is moveable towards and away from a box of a tubular through the operation of said piston and cylinder. The piston and cylinder may be activated by pneumatic or preferably, hydraulic fluid. 
   Advantageously, the apparatus further comprises an axle wherein the at least one guide is moveable thereabout. 
   Preferably, the apparatus further comprises a guide holder. Advantageously, the apparatus comprises two guides which are attachable to the guide holder. 
   Preferably, the apparatus further comprises a spring which biases said at least one guide to an open position. 
   Advantageously, the apparatus further comprises at least one torque post wherein said at least one guide is attachable thereto. 
   Preferably, the apparatus further comprises a bracket wherein said at least one guide is moveable with respect to said bracket. 
   Advantageously, said at least one guide is made from an elastomeric material. 
   The invention also provides an apparatus for aligning tubulars which apparatus comprises a tong, a backup unit, at least one torsion post arranged therebetween, the apparatus further comprising at least one guide, characterised in that said at least one guide is mounted on said at least one torsion post. 
   The invention also provides a method for aligning tubulars using the apparatus of the invention, comprising the step of moving said at least one guide towards and away from a box of a tubular with respect to said backup unit. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention reference will now be made, by way of example, to the accompanying drawings, in which: 
       FIG. 1  is a perspective schematic view of a first embodiment of an apparatus of the present invention in a first stage of operation, with parts cut away; 
       FIG. 2  is an enlarged perspective schematic view of the apparatus of  FIG. 1  in a second stage of operation; 
       FIG. 3  is an exploded perspective view of part of the apparatus of  FIG. 1 ; 
       FIG. 4  is a side plan view of the apparatus of  FIG. 1 , in the second stage of operation; 
       FIG. 5  is a front plan view of the apparatus of  FIG. 1 , in the second stage of operation, with parts cut away arid parts shown in cross-section; 
       FIG. 6  is a top plan view of the apparatus of  FIG. 1 , in the second stage of operation, with parts cut away; 
       FIG. 7  is a perspective schematic view of a second embodiment of an apparatus of the present invention, in a first stage of operation, with parts cut away; 
       FIG. 8  is a perspective view of the apparatus of  FIG. 1  in a second stage of operation, with parts cut away; 
       FIG. 9  is a side plan view of the apparatus of  FIG. 7 ; 
       FIG. 10  is a front plan view of the apparatus of  FIG. 7 ; and 
       FIG. 11  is a top plan view of the apparatus of  FIG. 7 . 
       FIG. 12  is a perspective view of another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 1 to 7 , there is shown an apparatus generally identified by reference numeral  1 . 
   The apparatus  1  comprises a power tong  2  and a backup tong  3 . Torsion posts  4  and  5  are arranged between the power tong  2  and the backup tong  3  on opposing sides thereof. 
   A guide unit  6  is provided on each of the torsion posts  4  and  5 . Referring to  FIG. 3 , each guide unit  6  comprises a clamp  7 , a spring  8 , a piston and cylinder unit  9 , a guide shoe holder  10  and a guide shoe  11 . The guide units  6  may be mirror images of each other. 
   The clamp  7  comprises two semi-cylindrical parts  12  and  13  which are bolted together via lugs  14 ,  15 , arid  16  and  17 . Semi-cylindrical sleeves  18  and  19  lie between the semi-cylindrical parts and the torsion post  4 ,  5  on which the clamp  7  is mounted. The semi-cylindrical part  13  is provided with upper and lower substantially horizontal lugs  20  and  21 . The lugs  20  and  21  are substantially triangular and are provided with stub axles  22  and (not shown) at the apexes. 
   The spring  8  comprises a reel  23  fixed to the upper lug  20  and a spring wire  24  wrapped around the reel  23 . The spring wire  24  has two ends extending from the reel  23  substantially at a tangent thereto. One of the ends is retained in a clamping element  25  which is fixed to the upper lug  20 , and the other end contacts, and is biased against a pin  26  arranged on one side of the piston and cylinder unit  9 . 
   The piston and cylinder unit  9  comprises a cylinder  27  which has a square neck portion  28  at a front end thereof. Holes  29  are provided in the top centre and bottom centre of the square neck portion  28  for receiving the axle stubs ( 22  and not shown). The piston and cylinder unit  9  is moveable about stub axles  22  and (not shown) against spring  8 . The square neck portion  28  is also provided with posts  30  and (not shown) on opposing sides thereof which are fixed thereto. A block  31  is provided with holes  32  and (not shown) for slideably receiving the posts  30  and (not shown). The block  31  is attached to one end of a piston rod  33  ( FIG. 5 ). A piston  34  is attached to the opposing end of the piston rod  33 . The piston  34  is slideably arranged in the cylinder  27 . 
   The block  31  is connected to a guide shoe holder  10  by bolts  35  and  36 . The guide shoe holder  10  comprises a curved face  37  which is provided with reinforcing ribs  38  and  39  which are arranged substantially horizontally and spaced apart vertically. The reinforcing ribs  38  and  39  are provided with holes  40  for receiving bolts  35  arid  36 . The ends of the guide shoe holder  10  are provided with lugs  41  which facilitate holding of the guide shoe  11 . 
   The guide shoe  11  may be formed from an elastomeric material. The guide shoe  11  has a top section  42  which has an inwardly sloping angled portion  43  and a lower lip  44 . A bottom section  45  is substantially flat. The top section  42  is arranged above the guide shoe holder  10 . 
   Prior to use, a guide unit  6  is attached to each torsion posts  4  and  5  by clamps  7 . The semi-cylindrical sleeves  18  and  19  inhibit rotation of the clamps  7  about the torsion posts  4  and  5 . 
   In use, a tubular  46  such as casing or drill pipe which forms part of a string, is held in a spider in a floor of an oil or gas rig (not shown). Jaws  50  and  48  of the backup unit  3  are opened and placed around the top of the tubular  46 . The top of the tubular  46  is gripped by closing the jaws  50  and  48  of the backup unit  3 . The tubular  46  is gripped at a point such that the lip  44  of guide shoe  11  will be above a box  47  of the tubular  46 . 
   Springs  8  bias the rear of the guide shoe holder  10  outwardly towards the mouth of the backup unit  3  and hence open. As the backup unit  3  is moved towards the tubular  46 , the box  47  contacts the rear of the lower section  45  of the guide shoes  11 . The guide shoes  11  move about the box  47  around stub axles ( 22  and not shown). Once the backup unit  3  has firmly gripped the tubular  46 , piston and cylinders  9  are actuated by either hydraulic or pneumatic fluid, engaging and firmly pressing the lower section  45  of the guide shoe  11  against the box  47 . 
   A section or stand of tubulars  51  is lowered through jaws  49  and (not shown) of the power tong  2 . A pin on the lower end of the section or stand of tubulars is lowered into the box  47 , being guided by the top section  42  of the guide shoe  11 . The tubular may now be rotated by a top drive to screw the pin into the box to a low torque. 
   The jaws  49  and (not shown) of the power tong  2  are closed and the power tong is activated to torque the connection. 
   Referring now to  FIGS. 7 to 11  there is shown a second embodiment of the apparatus of the present invention generally identified by reference numeral  101 . 
   The apparatus  101  comprises a power tong  102  and a backup tong  103 . Torsion posts  104  and  105  are arranged between the power tong  102  and the backup tong  103  on opposing sides thereof. 
   Three guide units  106 ,  107  and  108  are arranged about and fixed to the backup tong  103 . The first guide unit  106  is fixed to a left jaw  109  of the backup tong  103 , the second guide unit  107  is fixed to a rear portion  110  of the backup tong  103  and the third guide unit  108  is fixed to a right jaw III of the backup tong  103 . 
   Referring to  FIG. 10 , each guide unit  106 ,  107  and  108  comprises a bracket  112 , a piston and cylinder unit  113 , a guide shoe holder  114  and two guide shoes  115 . 
   The bracket  112  comprises a base plate  116 , a vertical plate  117  arranged at the inner most point of the base plate  116 , and two spaced apart strengthening plates  118  arranged therebetween. 
   The piston and cylinder unit  113  is located in a hole  119  through the top of the vertical plate  117 . A cylinder  120  is provided with a flange  121  which is attached to the vertical plate  112 . A piston  122  extends from the cylinder  120 . The guide shoe holder  114  is fixed to a free extend of the piston  122 . 
   The guide shoe holder  114  comprises a central block  123  to which upper and lower horizontal bars  124  and  125  are fixed, as can best be seen in  FIG. 7 . Each guide shoe  115  is mounted on a block  126  which is movably disposed on a stub axle  127 , as can best be seen in  FIG. 8 . 
   The guide shoe  115  is similar to that of the first embodiment, in that the guide shoe  115  may be formed from an elastomeric material. The guide shoe  115  has a top section  128  which has an inwardly sloping angled portion  129  and a lower lip  130 . A bottom section  131  is substantially flat. The top section is arranged above the guide shoe holder  114 . 
   In use, a tubular (not shown) such as casing or drill pipe which forms part of a string, is held in a spider in a floor of an oil or gas rig. Jaws  109  and  111  of the backup tong  103  are opened and placed around the top of the tubular. The top of the tubular is gripped by closing the jaws  109  and  111  of the backup tong  103 . The tubular is gripped at a point such that the lip  130  of guide shoe  115  will be above a box of the tubular. 
   The piston and cylinders  113  are actuated by hydraulic or pneumatic fluid to engage the guide shoes  115  with the box and firmly pressing the lower section  131  of the guide shoe  115  against the box. 
   A section or stand of tubulars is lowered through jaws  132  and  133  of the power tong  102 . A pin on the lower end of the section or stand of tubulars is lowered into the box, being guided by the top section of the guide shoe  115 . The tubular may now be rotated by a top drive to screw the pin into the box to a low torque. 
   The jaws  132  and  133  of the power tong  102  are closed and the power tong is activated to torque the connection.