You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a continuation of U.S. patent application Ser. No. 10/174,416, filed on Jun. 18, 2002, now U.S. Pat. No. 7,124,828, which is a continuation of U.S. patent application Ser. No. 09/530,197, filed on Apr. 25, 2000, now U.S. Pat. No. 6,422,311, which is the § 371 National Stage of International Application No. PCT/GB98/03198, filed on Oct. 27, 1998, which claims benefit of German application No. 19747468, filed on Oct. 28, 1997, which applications and patent are herein incorporated by reference in their entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to an apparatus for retaining two strings of tubulars, and is particularly but not exclusively for use as a spider in the platform of an oil rig and also for use in an elevator of an oil rig. The invention also relates to a device for retaining a string of tubulars the device comprising at least one body part having a curved tapered surface upon which inserts are located for engagement with the string of tubulars. 
   2. Description of the Related Art 
   In the formation and operation of oil or gas wells it is desirable to lower a string of tubulars into the well. For this purpose, a retaining device is used in a platform of the rig, known as a spider, and a corresponding retaining device in an elevator of the rig. The string of tubulars is initially retained from falling down the well by the spider. Additional stands of tubulars are moved from a rack to a position above the spider. The stand of tubulars is connected to the string. The device in the elevator is placed around the top of the lengthened string of tubulars. The spider is then released from engagement with the string, and the device in the elevator now takes the full weight of the lengthened string of tubulars. The elevator moves downwardly towards the spider, lowering the lengthened string of tubulars. The spider engages the lengthened string of tubulars and the elevator is subsequently released from engagement therewith. This process is reversed for pulling a string of tubulars out of a well. 
   It is often desired to lower two substantially parallel strings of tubulars simultaneously, such as a delivery pipe and an injection pipe used in the forced extraction of oil or gas from a well or used in trial wells. 
   A problem associated with prior art devices is that their construction is large, expensive and can only be used for retaining two strings of tubular. 
   SUMMARY OF THE INVENTION 
   Accordingly there is provided an apparatus for retaining two strings of tubulars characterized in that said apparatus comprises body parts of a device for retaining a single string of tubulars and a converting member. 
   Other features and aspects of the present invention are set out in claims  2  to  9 . 
   There is also provided a device for retaining a string of tubulars, said device comprising at least one body part having a curved tapered surface upon which inserts are located for engagement with said string of tubulars characterized in that said curved tapered surface comprises a recess for the passage of cables. 

   
     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 top plan view of a prior art device for retaining a single string of tubulars; 
       FIG. 2  is a top plan view of an apparatus for retaining two strings of tubulars, the apparatus being in accordance with a first aspect of the invention; 
       FIG. 3  is a cross sectional view of the apparatus of  FIG. 2  taken along the line III-III; 
       FIG. 4  is a top plan view of part of the apparatus of  FIG. 2 ; 
       FIG. 5  is a cross sectional view of the part of the apparatus of  FIG. 4  taken along the line V-V; 
       FIG. 6  is a cross sectional view of the part of the apparatus of  FIG. 4  taken along the line VI-VI; 
       FIG. 7  is a top plan view of an apparatus for retaining a single string of tubulars, the apparatus being in accordance with a second aspect of the invention; 
       FIG. 8  is a top plan view of an alternative apparatus for retaining two strings of tubulars, the apparatus being in accordance with the first and second aspects of the invention; and 
       FIG. 9  is a cross sectional view of the apparatus of  FIG. 8  taken along the line IX-IX. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1  there is shown a prior art device for retaining a single string of tubulars. The device comprises two body parts  1  and  2 . The body parts  1  and  2  are generally triangular in shape and are hinged in relation to one another by means of inter engaging rows of eyelets  3  and  4  and a hinge pin  5  at one corner thereof. Each row of eyelets  3  and  4  is integral with the respective body part  1  and  2 . The body parts  1  and  2  also have inter engaging rows of eyelets  6  and  7  on the opposite corners thereof. The body parts  1  and  2  may be locked together by use of a locking pin  8  insertable through the rows of eyelets  6  and  7 . 
   The body parts  1  and  2  are provided with semicircular tapered surfaces  9  and  10  which taper downwardly from a first diameter  11  to a second smaller diameter  12 . In use, corresponding tapered inserts (not shown) are provided on the tapered surface for gripping the tubular which runs therethrough. The weight of the tubular string will be transferred from the tapered inserts to the tapered surfaces  9  and  10 . 
   A gap  13  is provided between the body parts  1  and  2 . Body part  1  also comprises an opening  14  which runs from the top to the bottom of the body part  1  and lies parallel to the tapered surface  9 . The opening  14  is provided for receiving an actuating piston and cylinder (not shown) which, in use, moves the tapered inserts along the tapered surfaces  9  and  10  for engaging or disengaging the inserts with a tubular. The actuating piston and cylinder may be hydraulic or pneumatic. 
   In use, two such devices are used. One device is mounted in an elevator and the other is mounted in the floor of an oil rig. A string of tubulars, such as casing, is first retained in the device mounted in the floor of the oil rig. A section of casing may then be added or taken away from the string of casing thereabove. This may be achieved by using tubular handling equipment to move the section of casing to a position above the string of casing, and a tong to facilitate connection or disconnection of the section of casing to or from the string of casing. The device mounted in the elevator may now be used to retain the section of casing extending above the device in the floor of the oil rig. The device in the floor of the oil rig may now be disengaged from the string of tubulars. The elevator is then operated to lower or raise the entire string of casing. The device in the rig floor is then used to retain the string of casing once again. 
   Referring to  FIGS. 2 to 6  there is shown an apparatus for retaining two strings of tubulars, the apparatus being in accordance with the invention. The apparatus is generally identified by the reference numeral  100 . 
   The apparatus  100  comprises body part  101  which is generally similar to body part  1  of  FIG. 1 , body part  102  which a mirror image of the body part  1  of  FIG. 1  and a converting member  103 . 
   The converting member  107  is generally rectangular in shape with rows of eyelets  104 ,  105 ,  106 ,  107  at each corner thereof. The converting member is provided with two semicircular tapered surfaces  108 ,  109  which taper downwardly from a first diameter  110  to a smaller diameter  111 . The semicircular tapered surfaces  108 ,  109  oppose each other and merge as the diameter increases from the smaller diameter to the first diameter as shown in  FIG. 6 . In use, corresponding tapered inserts (not shown) are provided on the tapered surfaces  108 ,  109  for gripping a tubular. 
   The converting member  103  is arranged between the body parts  101  and  102  and are hinged thereto. A row of eyelets  112  is integral with one corner of the body part  101  and inter engages with the row of eyelets  104  of the converting member  103  and a hinge pin  113  is located therethrough. A row of eyelets  114  is integral with a first corner of the body part  102  and inter engages with the row of eyelets  105  of the converting member  103  and a hinge pin  115  is located therethrough. A row of eyelets  116  is integral with an opposing corner of body part  101  and inter engages with a row of eyelets  106  of the converting member  103  and a locking pin  117  may be inserted therethrough to lock the body part  101  to the converting member  103 . A row of eyelets  118  is integral with an opposing corner of body part  102  and inter engages with the row of eyelets  107  of the converting member  103  and a locking pin  119  may be inserted therethrough to lock the body part  102  to the converting member  103 . 
   Each of the body parts  101  and  102  are provided with corresponding tapered surfaces  120  and  121  and with openings  122  and  123  for receiving actuating pistons and cylinders as described with reference to the device of  FIG. 1 . 
   In use, two such apparatuses are used, one as a spider in the platform of an oil rig and the other in the elevator of the oil rig. The method of operation is much the same as that described with reference to the device of  FIG. 1 , except that two actuating pistons and cylinders are used to move the tapered inserts along the tapered surfaces  108 ,  109 ,  120  and  121  for engaging or disengaging the inserts with a tubular. 
   Referring now to  FIG. 7  there is shown a device, generally identified by reference numeral  200 . 
   The device  200  is generally similar to the device shown in  FIG. 1  with the additional feature of a recess  201  in the tapered surface  202  of the body part  203 . The recess  201  is sized to accommodate a loom of cables running substantially parallel to the string of tubulars. This enables the cable strings to pass through the device for retaining a string of tubulars, for example, through a spider. 
     FIGS. 8 and 9  show an apparatus generally identified by reference numeral  300 . 
   The device  300  is generally similar to the apparatus  100  of  FIG. 2  with the additional feature of a recess  301  and  302  in each of the tapered surface  303  and  304  of the converting member  305 . The recesses  301  and  302  are sized to accommodate a loom of cables running substantially parallel to the two strings of tubulars. This enables the cable strings to pass through the device for retaining a string of tubulars, for example, through a spider. 
   It is envisaged that the apparatuses could be used for coiled tubing, as well as tool strings, strings of drill pipe, casing and liners. 
   While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Summary:
An apparatus for retaining two strings of tubulars characterized in that said apparatus comprises body parts of a device for retaining a single string of tubulars and a converting member. A device for retaining a string of tubulars, said device comprising at least one body part having a curved tapered surface upon which inserts are located for engagement with said string of tubulars characterized in that said curved tapered surface comprises a recess for the passage of cables.