Patent EA-003879-B1 (EA)
Title: Method and device for subsea dredging
Inventor: JACOBSEN TOM
IPC: E02F3/88
Filed: 2001-04-04
Abstract: 1. Method for moving subsea rocks and sediments, also at significant depths, e.g. in connection with removal of protective rocks around subsea installations, where maintenance is to be conducted, supplying the required power through one or more cables from the surface, utilizing a rigid or at least partly flexible tubing that preferably is remotely controlled by means of a manipulator adapted to the purpose, producing a pressure gradient through said tubing by connecting an ejector nozzle to said tubing and feeding water from a water pump to said nozzle, characterized in arranging the tubing, the ejector and the pump on a per se known chassis designed to move on the sea bottom and arranging said ejector nozzle externally in relation to said tubing. 2. Method as claimed in claim 1, characterized in providing the chassis with belts or wheels and move it along the sea bottom with power to the belts and/ or the wheels respectively. 3. Method as claimed in claim 1, characterized in that the at least partly flexible tubing is controlled by means of an hydraulically controlled multi-link arm. 4. Method ac claimed in claim 1, characterized in providing the chassis with belts or wheels that are able to turn freely in several directions and using an ROV as the manipulator and that the ROV is utilized for moving the chassis as well as for controlling the tubing. 5. Method ac claimed in claim 1, characterized in furnishing the chassis with "water cushions" that are fed with water from one or several water pumps enabling the chassis to float above the sea bottom using an ROV as the manipulator, and that the ROV is utilized for moving the chassis as well as for controlling the tubing. 6. Device for moving subsea rocks and sediments, also at significant depths, e.g. in connection with removal of protective rocks around subsea installations, where maintenance is to be conducted, comprising cable(s) (3) from the surface for supplying the required power, a rigid or at least partly flexible tubing (5) that preferably is remotely controlled by means of a manipulator (9, 9'), a water pump (12) connected to an ejector nozzle (11) that is attached to the tubing (5) so as to enable a pressure gradient to be set up through said tubing (5), characterized in that the tubing (5), the ejector nozzle (11) and the water pump (12) are arranged on a per se known chassis (F) adapted to be transported along the (sea) bottom and that the ejector nozzle (11) is arranged externally in relation to said tubing (5). 7. Device as claimed in claim 6, characterized in that the manipulator (9, 9') is an hydraulically controlled mufti-link arm (9). 8. Device as claimed in claim 6 or 7, characterized in that the chassis (F) is supported by belts (2) or by wheels (2') and is arranged to be transported along the sea bottom by power to the belts (2) and/ or the wheels (2') respectively. 9. Device as claimed in claim 6, characterized in that the manipulator (9, 9') is an ROV (9') that is controlled principally independently of the device (1) as such. 10. Device as claimed in claim 9, characterized in that the chassis (F) is supported by freely turning belts (2) or wheels (2') that possibly may be turned in any direction, and is arranged to be transported along the bottom with the aid of a pull force exerted by the ROV (9') through the tubing (5). 11. Device as claimed in claim 9, characterized in that the chassis (F) is provided with "water cushions" (2") facing the sea bottom fed with water from the pump (12) or by specially adapted pumps (not shown), so that the chassis (F) may partly float above the bottom (S) and is arranged to be transported along the bottom with the aid of a pull force exerted by the ROV (9') through the tubing (5). 12. Device as claimed in claim 6, characterized in that the tubing (5) at its inlet end (6) is telescopically extendable. 13. Device as claimed in claim 6, characterized in that the inlet end (6) of the tubing (5) comprises means (21) for penetration and pressurized water flushing (22) designed to disintegrate compact or hardened sediments in order to improve the suction capacity of the device. 14. Device as claimed in claim 6, characterized in that close by the inlet mouth piece (10) there is arranged a nozzle (not shown) for backwards flushing of rocks etc. that might get stuck in the mouth piece. 15. Device as claimed in claim 6, characterized in that the inlet mouth piece (10) is rounded and that the cross-section of the tubing (5) is constant, and that any bend of the tubing (5) has sufficiently large radius to ensure that rocks can not get stuck therein and that the outlet end (7) is shaped as a diffusor (to minimize the friction loss through the tubing).