Sea Technology

AUG 2017

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Page 13 of 76 August 2017 / st 13 establishes the operating depth of the coring system. With slight modifica- tion, the ROCS operational depth can be increased if required. Operation of the drill requires sev- eral additional system components, including a rotary rpm sensor, wa- ter pump, flushing water flow sensor, compensation system and hydraulic valve pack pressure sensors. A water pump that connects to the drill head is used to clear debris from the cut- ting surface of the bit during the drill- ing process. The flushing water pump should be capable of 22 L/min. with a pressure of 4 bar. The minimum sensor suite to drill includes video input from two viewing angles, a speed sensor for the drill head motor and a linear posi- tion sensor to indicate the position of the cross head assembly; however, a full sensor suite is advised. The ROCS drill is provided with a valve pack from Sub-Atlantic, allowing spare valves. The ROCS drill system interface in- cludes the mechanical attachment, the hydraulic power input, electrical pow- er and communication. These connec- tions use industry standard equipment to facilitate mounting/operating on any suitable work-class ROV or similar subsea asset with comparable capa- bilities. The mechanical interface uses an external frame that can be specific to the ROV. The bolt-on frame allows mounting to the host ROV without welding or modification of the ROV frame. The hydraulic system requires a direct low-pressure return path to tank. Electrically, a 24-VDC supply of up to 8 A is needed for full valve bank functionality. Telemetry is handled over a single dedicated serial channel (RS232) that interfaces the subsea sys- tem with a surface controller. Personnel Requirements In addition to the ROV-specific crew members providing critical sup- port for coring operations, the ROCS can be installed, maintained and op- erated by a crew of two: a driller and assistant driller. An additional techni- cian skilled in mechanical/electrical support is recommended. The drilling console should be installed in the ROV control center to facilitate communi- cations between the ROCS and ROV crews. For system installation and deck maintenance, personnel with electrical and mechanical skills typical for ROV operations can easily meet the needs of the system. Operations Procedure The drill is operated utilizing a con- trol console consisting of the ROCS surface controller, the driller control desktop console, assistant driller key- board/mouse and two monitors. The ROCS GUI consists of the driller con- sole window displaying the complete sensor feedback and controls neces- sary for drilling operation. The assistant driller monitors the serial terminal win- dow and the valve control window. The serial terminal window provides infor- mation on telemetry link and stability of communications. The valve control window provides detailed feedback from the valve pack displaying which valves are active and their associated PWM settings. The valve settings can also be adjusted from the valve control window. Drill Results An area of basalt at 2,700-m depth on the Mohn's Treasure was selected to test the hard rock drilling capabili- ties of the drill. After a total duration of about 2.5 hours, the drill was re- covered to deck with a hard rock core sample. In this case, 84 percent core recovery was achieved. The drill tool was able to penetrate 805 mm into the seabed. As no mineralized hard rock was identified for coring near the area of interest, the ROCS was also refitted to take push core samples. Two succes- sive push core operations successfully retrieved seabed material. During the first dive, 67 percent core recovery was achieved, and 39 percent during the second dive. Conclusion The MarMine cruise demonstrated the suitability of the ROCS design to convert ROVs of opportunity into ma- rine minerals exploration assets. Al- though this was the first mobilization of the ROCS, the mounting, integration and testing of the installation was com- pleted in three days. No modifications to the ROV were required. Hydraulic pressure and return lines were con- nected with standard fittings, and two electrical connections were made (24 VDC/valve pack control and a serial link for telemetry). The combination of large-diameter core, high rpm and low bit weight demonstrated that the ROCS was well suited for core sampling of rock (80 percent recovery) and even push core sampling of soft sediment. USA 1.508.291.0057 Clearly Superior Imaging SONAR SYSTEMS SUB-BOTTOM PROFILERS BATHYMETRY SYSTEMS SIDE SCAN SONARS

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