PRA-1

The ADCP or Current Profiler instrument was to be delivered as part of n ‘Environmental Monitoring System’, a unique deployment system delivered as part of the overall assembly. In addition a water temperature sensor was mounted on the same instrument hoist and together with the ADCP deployed to a fixed depth the water level of the sea. The complete system allow remote, (from topside), deployment, retrieval and regular maintenance of the unit using a guide-wire and winch arrangement.

Function

Two different instruments are deployed below the surface of the water to monitor environmental changes - a temperature sensor and an ADCP (or a Current Profiler) Both instruments are mounted on a giljotin type instrument support platform, which is deployed running on a pair of guide wires. The guide wires runs continuous in a loop over a two pairs of wire sheaves, one pair at a fixed position at the sub sea location, and the other pair at a location on deck of the rig. The later sheave arrangement is electrically powered, allowing the guillotine to be hoisted up and down while being terminated at the wire start and end. The instrument cabling is clamped to the guide wire(s).

Construction

The electrically powered topside support arrangement is proposed located on the first deck (EL. 15000), as far out on the platform deck as possible, pointing away from platform support structure.
An electric motor is mounted as part of the support structure, and allows the sensor package to be installed to the predefined logging position, and retrieved to surface if and when needed.
At a predefined installation depth a second support structure is permanently mounted. The structure consists of two (2) wire-sheaves and a pair of guide-posts. Hence the wire is guiding the instruments when being deployed (/retrieved), and the guideposts ensures optimal positioning while logging the environmental data.