Page 53 - Wire Rope News & Sling Technology
P. 53

said mast 3 is fixed, a base section 22, on which the entire
         drilling rig weighs, and a drilling head 5, which, in use, is
         adapted to slide along said mast 3 supported by at least two
         hoisting wire ropes 24. Said hoisting wire ropes are prefer-
         ably made of steel and their number is proportional to the
         maximum pull of the drilling rig, more preferably their num-
         ber is a multiple of two, and at least a draw-works or hoist
         4 being provided.
           Said mast 3 preferably is of the telescopic type and com-
         prises a main load carrying member 31, which is adapted
         to extend said telescopic mast. A plurality of pulleys 26, on
         which said hoisting wire ropes 24 slide, are rigidly fixed to
         the end of said carrying member 31. The number of said pul-
         leys 26 is at least equal to the number of hoisting wire ropes
         24. Said mast comprises a fixed portion 30, which is adapted
         to be fixed on drill floor 21 by means of front shoes 212 and
         back shoes 213, thorough suitable hinges, and a mobile por-
         tion 32, which is adapted to slide inside said fixed portion 30
         and is moved by said main load carrying member 31.
           The main load carrying member  31 is adapted  to bring
         said mast 3 from the closed operating configuration to the
         extended operating configuration and vice versa. Member 31   Figure 4: Embodiment with two drums on which two hoisting wire
                                                              ropes are wound.
         is connected to mobile portion 32, for example a telescopic
         one, and is adapted to transfer the compression load to said   are preferably managed by and an automatic central control
         base section 22, hence not to the structure of mast 3, which   unit, not shown, which is adapted to automatically control
         comprises,  in particular, said mobile portion  32 and said   drilling rig 1 according to the present invention. The use of
         fixed portion 30. This structural configuration allows users   the gear drive permits a reduction of energy losses, thus in-
         to maximize the symmetrical distribution of forces along the   creasing the efficiency of the drilling rig.
         axis of mast 3, thus reducing the bending effects of the struc-  Furthermore, while said hoisting wire ropes 24 are being
         ture and, in particular, of mast 3 and of member 31.  released by hoist 4, part of the electric energy generated by
           For the purposes of the present invention, the expression   the rotation of the hoist itself can be recovered by means of
         “mast in the extended operating configuration” means that   said motors 47. This energy can be stored or used by other
         the mast is erect on drill floor 21 in its maximum longitu-  electronic devices comprised in drilling rig 1. Thanks to the
         dinal extension. For the purposes of the present invention,   electric control, it is possible to directly control electric mo-
         the expression “mast in the closed operating configuration”   tors 47, which, in turn, directly actuate the drive train of
         means that the mast is not in its maximum longitudinal ex-  hoist  4,  thus  directly  turning  the  electric  energy  into  me-
         tension, preferably it is in its minimum longitudinal exten-  chanical energy. In particular, drums 43, which are coupled
         sion. The movement of drilling head 5, when said mast  3   to shaft 41, are moved by means of gear drive 45. The hoist 4
         is  in  the  extended  operating  configuration,  takes  place  by   comprises, furthermore, brakes 49, which preferably are ser-
         means of said hoisting wire ropes 24, which are pulled and   vice brakes or safety brakes. Each pair of drums 43, which is
         released by said at least one hoist 4.               associated with the same number of hoisting wire ropes 24,
           At least one hoist 4 comprises at least two drums 43, pref-  is controlled by a single electric motor 47, which transmits
         erably a plurality of drums 43, for example one drum 43 for   the motion to shaft 41 by means of said gear drive 45.
         each hoisting wire rope 24, and a single shaft 41, with a drive   In  the  embodiment  of  figure  3,  hoist  4  according  to  the
         train 45, preferably a gear drive. In a preferred embodiment,   present invention comprises four drums 43, which are as-
         said hoist  4 is controlled electrically. In the embodiments   sociated with four hoisting wire ropes 24, one for each drum.
         shown in figures 3 and 4, said hoist 4 is moved by means of   Said hoist 4 is controlled by two electric motors 47, which
         at least one electric motor 47, which is controlled by means   are arranged at the ends of single shaft 41, which is shared
         of a suitable control unit 471. The control units 471, in turn,   by all drums 43. In the embodiment  of figure 4 there are
                                                              provided two hoisting wire ropes 24 and the same number
                                                              of drums 43. This embodiment comprises one single electric
                                                              motor 47 and gear drive 45 is arranged in the middle be-
                                                              tween the two drums 43. Gear drive 45 is directed at single
                                                              shaft 41, which is shared by both drums 43.
                                                               Hoist 4 according to the present invention, besides high-
                                                              power  motors  47  for  the  movements,  can  comprise  one  or
                                                              more auxiliary low-power motors, which are associated with
                                                              the same number of reduction gears with a high reduction
                                                              ratio, which are useful in the drilling step, where it requires
                                                              a very low release speed, but a high pull of the rope. This
                                                              solution allows the drilling rig to be used in three different
                                                              modes: with a constant load, with a constant pull speed, and
                                                              with a constant fluid pressure, in which the rotation speed of
                                                              the drum and, hence, the downward speed of the drill string
                                                              “W” is such as to keep the pressure of the fluid used to rotate
         Figure 3: Embodiment with four drums on which four hoisting wire
         ropes are wound.                                                                      continued on next page
                                                                Wire Rope News & Sling Technology   June 2017  53
   48   49   50   51   52   53   54   55   56   57   58