Portable Dynamic Positioning System (PDPS)

The Thrustmaster Portable Dynamic Positioning System (PDPS) adds temporary DP capability to a vessel or barge for short-term offshore work such as pipe lay, cable lay, diving and salvage. It can be removed afterwards and reused on another vessel. No permanent vessel modifications are needed. The system is installed dockside, and mobilization and sea trials usually take less than a week.

System components

• Modular, deck-mounted hydraulic outboard azimuthing thrusters, usually fitted on temporary sponson decks welded to the hull
• A containerized diesel-hydraulic power unit (HPU) for each thruster, in a modified ISO 20 ft container. Each HPU has a radiator-cooled engine, hydraulic power pack, reservoir, oil cooler, fuel day tank and local control console
• A central DP computer console (compact joystick system) for manual and automatic control of position and heading
• Optional sensors: gyrocompass, differential GPS and wind sensor, duplicated for DPS-1. A DPS-2 configuration gives dual redundancy for diving or critical positioning

Technical data

• Standard thruster sizes: 250, 500, 750 and 1,000 hp
• System sizes: 500 to 8,000 installed hp
• Hydraulic motor drives the propeller directly inside a high-thrust nozzle. There are no moving parts in the stem, so stem length can be adapted to the vessel's depth
• Steers 360° continuously
• Power transmission efficiency of 80–82% at full load, and higher at part load
• Thrust is controlled through the hydrostatic pump's swashplate, commanded by the DP computer

Performance example

On one project the required watch circle was 5 m in Sea State 4 (6.2 ft significant wave height, 19 kn wind). The system held a 1–2 m watch circle for five hours, including a simulated failure of two thrusters.