Deep ocean sampling and observation

Paul Boughton
Berkshire, UK-based remote handling specialists, Hydro-Lek Ltd, has partnered with National Oceanography Centre in Southampton to develop HyBIS, the deep ocean sampling/observation system. HyBIS was deployed last month by a British scientific expedition to discover and film for the first time the world's deepest undersea volcanic vents located 5000m (3. 1 miles) down in the Cayman Trough in the Caribbean.

HyBIS, a mnemonic for Hydraulic Benthic Interactive Sampler, enables seabed sampling at extreme depths and conditions together with video instrumentation observation. Highly robust, flexible and inexpensive, HyBIS is designed to operate in conjunction with existing deck handling and cable systems used on extended towed sonar arrays, thereby eliminating the need for additional and costly ROV deck handling equipment. It also enables sonar surveys to be followed up with localised observation and sampling during the same voyage.

HyBIS measures 1.5m x 1.4m x 1.8m high and comprises two subsea modules : an upper module which houses hydraulic and electric power modules with thrusters, release mechanism, video and lighting, and fibre-optic telemetry for instruments and sensors; and a lower module which houses a detachable sampling grab, automatic closing covers and hydraulic drive cylinders.

Hydro-Lek has used corrosion resistant materials throughout the manufacture of HyBIS and it is designed to withstand the high pressures and harsh environment found at depth. Indeed, the pressure 3 miles deep at the bottom of the Trough is 500 times the normal atmospheric pressure - this is equivalent to the weight of a large family car pushing down on every square inch of the seabed. Electrically-driven thrusters enable the vehicle to be manoeuvred above the seabed under its own power.

In operation, the HyBIS acts as an ROV which is controlled at depth via the umbilical winch. All other functions are self-generated using the on-board electrical services.

The system is operated from maximum 7Kw 220-240V single phase power source at the surface via the umbilical cable. All 3 phase power and control voltages for lighting and instrumentation are contained in 6000 metre rated pods. The control of HyBIS from the surface is via a hand held control box. This contains the command telemetry for remote operation of all hydraulic and electrical functions including remote switching for power to lights, cameras, and other demands for ancillary equipment. This is transmitted th rough an RS 232 link via the optical fibre to the subsea instrumentation pod. This then controls a range of driver and relay boards to control all subsea systems. The system comprises two 3 phase power packs and two 4-way valve packs which provide power for all hydraulic functions.

The HyBIS has two reversible thrusters, one fitted each side of the vehicle which allows manoeuvrability about the umbilical. Each thruster can produce 40 kg of thrust from the 1.5 Kw motors. This allows HyBIS to manoeuvre around a radius of one hundred metres from the surface ship and survey the sea floor at a speed of 0.5kts.

The sampling module on the lower section of the HyBIS comprises a 900 x 800 mm clam-shell grab capable of picking up to 0.3 cu metres of soft sediment, shingle and loose material which can be hydraulically ejected remotely in an emergency. The HyBIS is also fitted with one camera and two lights working horizontally for steering and observation, and one camera fitted vertically for observation during descent and monitoring of grab contents during ascent.

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