ROV Drill System Description

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ROV drill system
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Schematic drawing of the ROV Drill System tool-sled layout showing the major components of the multiple barrel drilling system. This system houses a 1-m long drill with 4 barrels. (Courtesy of MBARI)


    The ROV Drill System was developed by the Monterey Bay Aquarium Research Institute (MBARI) and utilizes a multiple barrel coring system (MCS) that is based on an AW 34 Christensen Mining Products core barrel which has a core size of 33.5 mm with a hole size of 50.8 mm (2.0 in).  The drill has a four-barrel coring system, which uses a hydraulic cylinder to advance or retract the single drive motor shaft (see Figure).  The drive shaft uses a quick-connect device (QCD) to switch between the multiple barrels.  The four barrels are arranged in an indexable fashion that is rotated by another hydraulic motor linked to a 4-point Geneva gear assembly.  The advancing motor shaft compresses an internal spring in the QCD to allow the motor shaft to lock onto the core barrel.  Once a solid latch is confirmed the front gate to the drill system is opened and the drill barrel can be advanced for drilling.  The front gate also has an explosive cutter that can shear the core barrel if the drill bit becomes stuck in the hole thus releasing the vehicle.  A similar type of explosive cutter has already been used in 2003 when the MBARI drill was used on Jason2 for work at hydrothermal vents and basalt outcrops at the Main Endeavour Field.  This cutter was used for the D. Kelley funded work at Main Endeavour vent field in Fall 2005 and we have factored necessary spares for the cutter into the proposed transition of the drill system for use with Jason2.  In the future, because the cutter is only rated to 4000 m, we will explore extending the depth of the cutter to match the 6500 m depth rating of Jason2.

Each core barrel consists of an inner and outer core barrel where the inner barrel remains stationary along with the core and the outer barrel rotates.  The inner barrel is split to facilitate core removal.  The type of drill bits used depends on the rock to be cored.  For hard rock like basalt, a drill bit with a surface set diamonds is used, for softer sulfides or consolidated sediments a coarser toothed bit is used.  MBARI has  transferred its complete inventory of drill bits and reamer bits to us as part of the acquisition package.  At present, there are 18 drill bits in the inventory.  To facilitate drilling, a water circulation system uses a hydraulic motor to pump water between the inner and outer core barrels to exit through the waterways of the drill bit.  Water circulation helps in clearing the tailings from drilling and generally helps to speed up the drilling process. 

The command and control system used for the drill system is based on RS-232 and -485 telemetry, and has been provided by MBARI to WHOI.  The transfer included all source codes and software and has been installed on two laptop computers that are part of the ROV Drill System.  This control system has been previously used on Jason2 with excellent success (Fall 2003) and integration of it with Jason2’s telemetry and control, as well as its hydraulic system, worked very well.  We do not plan to alter this aspect of the system at present, however, experience gained during the Fall 2005 field work, and additional discussions with MBARI and NDSF engineers will help guide future improvements.



 

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Last updated March 12, 2008
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