Technology

T he novel aspect of the ROV is the design philosophy. Like many ROV systems, it is designed using a modular pack that enables the vehicle to be configured quickly to differing work scopes. The difference between this and other designs is how deep this philosophy goes. Historically the ROV itself has been seen as the lowest adapted to fit on an as needed basis. In principle, common denominator with specialist tooling the approach taken by Total Marine Technology is the same as a component hi-fi system, according to its President Tom Pado, who saw the potential right away when his partner Paul Collie explained to him his new component approach. The amplifier provides a focal point for the other components however; the user defines the options, eg. DVD player, CD player, tuner, tape deck, etc. This limits system obsolescence and enables the operator to build on a firm foundation while maintaining technical relevance in the market place.

In the same way, it is just the control and hydraulic power pack that is recognised as the focal point of the Nomad ROV system. To this, an arrangement of thrusters, manipulators, tracks and clump weight ancillary packs can be added as determined by the job scope.

These packs are interlocked using a system that allows them to be stacked in multiple configurations and can be changed over in twenty minutes or less. Hydraulic power is reticulated via a geometrically fixed hot stab system common to all packs and a single electrical connector.

The basic vehicle has a depth rating of 1500m. It has a length of 2.5m and a width of 1.6m. Its height and weight however, depends on the type of operation it is customised to carry out. In the free-swimming mode, the vehicle is 2m high and the weight is 2200kg. In drill support mode, the height is 2.4m and the weight is 2800kg. The vehicle in crawler mode is 2.5m in height and the weight is 3200kg.

The vehicle is composed of three essential packs, the buoyancy, thruster and power packs. The basic vehicle is equipped with two axial thrusters, one lateral thruster and one vertical thruster. This can produce a thrust of 800 - 1800 kg forward, astern port/starboard and vertical up/down. There is the facility to add or subtract buoyancy as required.

The recording equipment includes up to eight cameras. One is a colour high-resolution zoom; one is a low light and the remainder are high resolution colour. Illumination is provided by lights totaling up to 5000 Watts. The images are recorded on two video recorders and the ROV movement is assisted by a Mesotech/Tritech/Imaginex sonar system.

The vehicle has been designed around a variety of projects including drill support, production, production tooling, construction support, cable laying, jetting, pipeline inspection, salvage, pipelay support, platform inspection and cleaning. In order to carry out these specific tasks, a number of optional packs may be added as appropriate. These include such things as a tooling pack which would incorporate manipulators and grabbers, a clump weight pack for drilling support mode, a track pack for cable survey and cable laying and a jetting pack for cable burial.

The tool pack is essentially an aluminium frame with a camlock connection at each corner and hydraulic quick connect for rapid connection and disconnection. All electrical and hydraulic manifolds are fitted on the pack, which allows for one electrical and one hydraulic connection to the power pack.

The pack incorporates two 8-function manipulators and one 2 function grabber featuring a manually rotating head. There is an option of a further 5-function manipulator. The manipulators are used for tasks such as valve override, flowline connection guide, guide wire installation, cutting and various other tools that are required for subsea work. The grabber is used to grab hold of a structure to allow the vehicle to hold position. It may also be used to handle tooling.

The manipulators are capable of lifting 330 lbs at a 10ft reach. The level of automation inherent in this system also enables the unit to perform safely with one operator (once in the water). To date this system has incurred zero down time.

The clump weight pack is also an aluminium frame with a camlock connection. It also has a single electro-hydraulic connection to the power pack. The pack is fitted with a hydraulic winch that is used to lower and raise the clump weight. Then, the lift umbilical is slacked off from the surface. Ultimately, by operating the clump winch, the vehicle can control its height in reference to the seabed. The winch has a 8000kg line pull and the drum capacity on the winch is 50m. The clump weight is 500kg.

Within its aluminium frame, the track pack is used for cable surveying or cable laying. The tracks allow it to walk on the seabed. The tracks are 0.32m wide and centres are spaced 2m apart. The track moves at a speed of 0.5m/sec. The control van/workshop is 6.1m in length and 2.4m in width. It has a height of 2.75m and a weight of 5000kg.