Page 66 - Wire Rope News & Sling Technology - August 2019
P. 66

         continued from previous page
         2m, 3m, 4m, 5m, or even more.
           With a distance between the load cables of less than 1m,
         or possibly only a few meters, it can be appreciated that, as
         the extent of the parallel winch operation is greater with in-
         creasing depth operation, the potential for cabling increases,
         where the load cables could move relative to one another, in
         particular, come closer to one another and even result in ro-
         tational entanglement. While this may seen more expectant
         for a two-cable subsea lifting system, the problem can occur
         also with multi-cable subsea lifting systems using more than
         two cables, especially where the lifting system may be di-
         vided into subsets or pairs of cables, each subset comprising
         closely spaced cables. Thus, the present invention extends to
         aiming to relatively maintain a defined divide or distance or
         space between any two load cables in a multi-cable subsea
         lifting  system.  Indeed, the  present  invention  also  extends
         to aiming to simultaneously relatively maintain the defined
         divide, distance or space between more than two cables, gen-
         erally running in parallel operation, by extension of the sub-
         sea anti-cabling device imparting a rotational force to one
         or more of the load cables in response to and to counter the
         torque experienced by the load cable.
           Figure 11 shows the load cables 4a, 4b extending to a sub-
         sea attachment point. Figure  11 also shows  a measuring
         device in the form of a tension/torsion load cell 14 able to
         provide tension and torsion information to a monitor or con-
         trol (not shown) to identify the on-going tension and torsion
         of each load cable 4a, 4b to an operator. The system further   Figure 13: Front view of the anti-cabling device.
         comprises a subsea anti-cabling device 20 and a torque mea-
         suring device 22 associated with each load cable 4a, 4b.  tachment point and comprises two or more load-cable ter-
           Referring to figures 12 to 14, a first embodiment of a sub-  minations 26 for connection with a respective load cable 4a,
         sea anti-cabling device  20 for use in the lifting system in   4b. The load-cable terminations 26 may be in any suitable
         accordance  with  the  invention  is  shown.  The  anti-cabling   form for connecting the load cables 4a, 4b to the anti-cabling
         device 20 is connected to the load cables 4a, 4b at the at-  device 20. For example, the load-cable terminations 26 may
                                                              comprise a wedge socket, socket-resin connection or spelter
                                                              socket. In the embodiment shown, the load-cable termina-
                                                              tions 26 are in the form of a spelter socket.
                                                               In the embodiment shown, the anti-cabling device 20 com-
                                                              prises a symmetrical arrangement for each load cable 4a, 4b
                                                              deployed in parallel. The anti-cabling device 20 comprises a
                                                              motor 24 connected to a respective load-cable 4a, 4b. The mo-
                                                              tor 24 may be any suitable motor capable of imparting a rota-
                                                              tional force to the respective load cable 4a, 4b. In the embodi-
                                                              ment shown, the motor 24 is in the form of a stepper motor.
                                                               Each stepper motor 24 is battery operated and the lifting
                                                              system comprises one or more batteries 32 for powering the
                                                              stepper motors 24. In the embodiment shown, each stepper
                                                              motor 24 is powered by its own battery 32 which is housed
                                                              within the anti-cabling device. While the motors 24 are shown
                                                              as being battery operated, it would be understood that the
                                                              motors may instead be electrically operated or operated by a
                                                              different power source. Each motor 24 is directly connected to
                                                              the load-cable termination 26, and hence the respective load
                                                              cable 4a, 4b, via a shaft 28. It would be understood that each
                                                              or one of the motors 24 may be indirectly connected to a re-
                                                              spective load cable 4a, 4b by suitable means.
                                                               The torque measuring device 22 is in the form of a torque
                                                              sensor which comprises a rotating disc encoder. The torque
                                                              sensor 22 is mounted on the shaft 28 and a thrust bear-
                                                              ing 42 is positioned between the torque sensor 22 and the
                                                              load-cable termination  26. The system further comprises
                                                              a controller 30 in communication with each motor 24 and
                                                              torque sensor 22. The controller 30 is configured to actuate
         Figure 12: Side view of a first embodiment of a subsea anti-cabling   each motor 24 to impart a rotational force to its respective
         device for use in the lifting system.                load cable  4a,  4b in response to measurements obtained

         66     Wire Rope News & Sling Technology   August 2019
   61   62   63   64   65   66   67   68   69   70   71