E-marine’s plough can bury telecommunication cables, power cables and oilfield umbilicals either as they are laid, or in a post lay burial mode.
For simultaneous lay and burial, the plough is deployed and recovered with the lay cable passing through the plough and with the tow cable and umbilical connected.
Launching and recovery of the plough is generally described as follows:
At approximately half of the depth of the water distance, the ship stops before the planned start location. The plough is then launched. As it goes down, the ship moved slowly ahead. By the time the ship is on the planned location, the plough is also on the seabed. The ship is then asked to stop to give time for the plough to check all systems. Ploughing commenced. Ship is then asked to move ahead. Thus starting the operations.
Based on the plough position (which is a computed KP based on layback), the plough stop at planned end location. The ship is then asked to back slowly towards the plow location maintaining the tension on the cable. Plough is then lifted off the seabed and secured on the ship’s deck.
The plough moves the soil in such a way that it is easy to pull leaving the cable buried beneath a level of the seabed. A trapezoidal prism of soil is cut in an inclined, freely rotating disc cutter, a sharp knife and a horizontal point. The wedge of soil so defined is then gently lifted upwards from below by an inclined ramp. As the wedge is lifted up, it is also pushed outwards and rises up the sloping surface cut by the disc. The cable is then inserted down the ground on the slot so formed. The wedge of soil is then allowed to fall back down on top of the cable thus burying it.
In some occasions, cable joint boxes, transition boxes as well as repeaters go through the plough. The plough is provided with a system for passing cable joints as well as repeaters up to 380 mm in diameter.
When a joint box pass through the bellmouth of the plow, it is detected by a proximity switch pushing open the cable feelers against a sprung mounting which holds the depresser down. The joint box then runs along the cable trough and into the chute passing through the share end and will be buried the same manner as the cable.
The plough is remotely controlled from a control cabin on the Cable Lay Vessel. This cabin houses a sophisticated control and monitoring system. The control cabin and the plough are linked via a small umbilical, which utilizes optical fibers to allow very long transmission lengths.
Keypads and joysticks operate all the plough functions, and the surveillance information transmitted from the plough is displayed on graphics screens and recorded on video, chart recorder and logger in the cabin. Additionally, a cable management system is installed in the cabin providing the same chart guidance monitor for the plough operators.
An additional survey system provides the relative position of the plough. Together with all these systems, the operator can constantly monitor and control the whole ploughing operation.