Cut and Hold Grapnel

Global Marine Systems Limited has a long history of innovations that has placed it in the forefront of the subsea cable maintenance market. One such innovation is the grapnel that Global Marine Systems developed for deep water repairs. The Global Marine Cut and Hold Grapnel combines the capabilities of both a cutting drive and holding drive, enabling the grapnel to cut one side of a cable while simultaneously gripping the other. This approach cuts down substantially on the amount of cable that needs to be cut out, and the length of time it takes to perform a repair.

With a maximum depth of 5,000 fathoms, the Global Marine Systems’ Cut and Hold Grapnel can be used on all lightweight conventional cables and optical fibre systems. The grapnel has a built-in sonic transmitter which provides the surface vessel with an exact sea-bed operational status, allowing the vessel to respond instantly when cable contact has been made. Once the cable has been located and hooked by the grapnel, a hydraulic holder system secures it  prior to cutting.

After cutting, the grapnel held cable end is recovered in a single operation. The remaining cable end can then be recovered, close to the original cut, with the grapnel operating in hold-mode only. This reduces cable wastage and sea bed disturbance, minimising the possibility of cable damage and fibre strain.

In one deployment, Global Marine Systems’ cable ship Pacific Guardian used the Global Marine Systems’ Cut and Hold Grapnel for a complex cable repair, in 4500 meters deep water off the U.S. Continental Shelf. With use of the conventional approach of separate cutting and holding drives, the repair would have resulted in the loss of approximately 9 kilometers worth of cable. Given the cable system’s configuration constraints, and with limited spare cable available, Global Marine Systems knew that this approach would not be an option. The Cut and Hold Grapnel was able to cut and recover the cable to the surface in one attempt for each of the three cable sections it was working on. In addition to saving on cable, use of the Grapnel also avoided the two weeks of operational downtime (and the freighting costs) that would have resulted from provisioning the additional cable required to replace cable lost through traditional cut and hold technology. Even if replacement cable had been readily available, the use of the Global Marine Systems’ Cut and Hold Grapnel would have shaved approximately 24 hours of downtime because its method is much faster.