Remotely Operated Hoisted Platform (ROHP)

Remotely Operated Hoisted Platform (ROHP) 

This Remote Operated Hoisted Platform (ROHP) was custom-built by Seatools for the Dutch North Sea Directorate, with the purpose of facilitating inspection, sampling and survey tasks in the North Sea, Waddenzee and approaches to Dutch ports.

The ROHP can be operated either directly below a vessel by hanging off a steel armoured umbilical, or in ‘free-flying’ mode, during which, a flexible tether allows the vehicle to move in a 200 meter radius around the vessel.

Equipped with eight thrusters, the ROHP is capable of automatic roll, pitch, heading and depth/altitude control functions. A total installed power of 100 kW gives the ROHP a maximum operating speed of four knots, allowing for rapid surveys of large areas. Apart from the hydraulics and thrusters, Seatools also designed and built the integrated control system that allows the operator to effortlessly manoeuvre the ROHP from a container-based control-cabin mounted on the deck  An umbilical winch and heave compensation cylinder are also attached to the control cabin. The semi-active heave compensation allows the ROHP to work very close to the bottom – an essential feature when conducting visual inspections in the North Sea’s murky waters.

As can be expected for this type of operation, the ROHP is equipped with a large number of data sources, including video, sidescan sonar and magnetometer. Data transmission and vehicle remote control is accomplished via optical fibres.

In addition to inspection and survey sensors the ROHP is equipped with several intervention tools, such as a jet pump for clearing silt and sand from objects, a seven axis manipulator for handling materials and a hook with a payload of 250 kg, facilitating object removal from the seabed.  For ecological inspection tasks, both water and bottom samplers are available.