Completing the Cable and Junction Box Installation at Axial Base

Saturday, July 19, 2014
Big Red Jellyfish
ROPOS Latching Into ROCLS

ROPOS uses a T-handle to latch into the top of the ROCLS cable drum. Photo Credit: NSF-OOI/UW/CSSF; Dive R1716; V14.

Cable Connected to Junction Box LV03A

The 1 km extension cable from the Primary Node PN3A at the base of Axial Seamount is connected to the low voltage node LV013A, which will feed the two moorings at this site. Photo credit: NSF-OOI/UW/CSSF; Dive R1717; V14.

In the wee morning hours, ROCLS unexpectedly became stuck in soft sediment when it was unlatched from ROPOS at the end of the 1-km cable lay that had been completed earlier. Surprisingly, there was a bit of a slope at this site, and this, plus the soft sediment, caused ROCLS to sink down and get stuck. Because of the angle of ROCLS, it was not possible to relatch into the underbelly of ROPOS. However, the ROV team had planned for situations like this when they designed this novel cable laying system. They installed a winch with a T-shaped latch on the end of a kevlar line (similar to what you would see on the back of a jeep) underneath ROPOS that could latch into the top of ROCLS, pulling it upward and upright when winched. In the attempt to latch into ROCLS with the T-handle, the kevlar line was caught in between the ROV and ROCLS, severing the kevlar line. ROPOS tried to free ROCLS from the sediment using the manipulators, but this was not possible. The decision was made to surface and put a new line onto the winch. ROPOS ascended and in record turnaround time, descended again to the seafloor.

Upon reaching the seafloor, the same latching maneuver was performed swiftly and successfully. ROPOS hovered over ROCLS, rapidly latched into the top, and winched it free out of the sediment. With ROCLS free, they were able to set it down again and free the flange box that held the cable termination and wet-mate connector to be attached to the preinstalled junction box - LV03C. ROPOS surveyed the cable to confirm it is well laid. In addition, a two-hour visual survey was conducted to determine that the area ~ 15 m away from the flange box was flat (a great place for final installation of the junction box), and to visually inspect the seafloor area where the 12,000-lb anchors for the moorings will be installed on a future leg.

At the end of the dive, ROPOS successfully connected the wet-mate connector to the junction box, relatched into the empty ROCLS drum, and surfaced at a little after 9 pm. Large swells, ~ 10-ft high, had developed, so the night was finished by conducting an EM302 survey, followed by a transit to the the International District at the summit of Axial Seamount. We hope to dive at first light, taking junction box MJ03C down to the seafloor.