Trenching device

Abstract

A trenching device ( 1 ) for forming a trench ( 2 ) in a seabed ( 3 ) to receive an elongate object, such as a pipeline, said trenching device ( 1 ) comprising a base frame ( 6 ), and a trenching wheel ( 7 ) which is connected to the base frame ( 6 ) and rotatable about a trenching wheel axis ( 8 ) to form the trench ( 2 ), wherein the trenching device ( 1 ) is configured to push the trenching wheel ( 7 ) into the seabed ( 3 ) when the trenching wheel ( 7 ) is positioned on the seabed ( 3 ).

1 .- 66 . (canceled) 
     
     
         67 . A trenching device for forming a trench in a seabed to receive an elongate object, such as a pipeline, said trenching device comprising:
 a base frame; and   a trenching wheel which is connected to the base frame and rotatable about a trenching wheel axis to form the trench, wherein the trenching device is configured to push the trenching wheel into the seabed when the trenching wheel is positioned on the seabed.   
     
     
         68 . The trenching device according to  claim 67 , wherein the trenching device comprises a ballast to push the trenching wheel into the seabed when the trenching wheel is positioned on the seabed. 
     
     
         69 . The trenching device according to  claim 67 , wherein the ballast is formed, or partly formed, by a ballast system. 
     
     
         70 . The trenching device according to  claim 69 , wherein the ballast system is configured to adjust the magnitude of the force working on the base frame. 
     
     
         71 . The trenching device according to  claim 69 , wherein the ballast system is configured to adjust the position of the force working on the base frame. 
     
     
         72 . The trenching device according to  claim 69 , wherein the ballast system comprises a ballast tank configured to hold a fluid, a pump system to pump water in the ballast tank, and the pump system is configured to pump gas in the ballast tank. 
     
     
         73 . The trenching device according to  claim 72 , wherein the ballast tank comprises multiple ballast compartments, the pump system is configured to pump water in multiple ballast compartments independently from each other, and the pump system is configured to pump gas in multiple ballast compartments independently from each other. 
     
     
         74 . The trenching device according to  claim 68 , wherein the trenching device comprises a front side and a rear side, the trenching device is configured to be moved in the direction from the rear side to the front side, the resultant force of the ballast acting on the base frame is located at a distance e beyond the trenching wheel axis when seen in the direction from the rear side to the front side. 
     
     
         75 . The trenching device according to  claim 67 , wherein the trenching device comprises a propulsion system formed by at least one propulsion unit which is connected to the base frame to move the trenching device along the seabed, and the base frame comprises a first frame part and a second frame part which are connected to each other via a pivot connection, the trenching wheel is connected to the first frame part, and at least one propulsion unit is connected to the second frame part. 
     
     
         76 . The trenching device according to  claim 75 , wherein at least one propulsion unit comprises an assisting wheel connected to the base frame and rotatable about an assisting wheel axis, and a further wheel drive to rotate the assisting wheel around the assisting wheel axis in order to move the trenching device along the seabed. 
     
     
         77 . The trenching device according to  claim 76 , wherein the assisting wheel in the direction of the assisting wheel axis comprises a thickness t 3  and the thickness t 3  remains constant in the direction from the assisting wheel axis to the outer circumference of the assisting wheel, and the thickness t 3  is larger than t 2  and smaller than t 1  or the thickness t 3  is larger than t 2  and smaller than t 2 +0.5(t 1 −t 2 ). 
     
     
         78 . The trenching device according to  claim 75 , wherein the second frame part is pivotable about a frame pivot axis relative to the first frame part, and the frame pivot axis extends perpendicular, or substantially perpendicular, to the trenching wheel axis. 
     
     
         79 . The trenching device according to  claim 75 , wherein the trenching device comprises a steering system configured to pivot the second frame part relative to the first frame part. 
     
     
         80 . A method of forming a trench in a seabed to receive an elongate object, such as a pipeline, with a trenching device comprising a base frame, a trenching wheel which is connected to the base frame and rotatable about a trenching wheel axis to form the trench, wherein the trenching device is configured to push the trenching wheel into the seabed when the trenching wheel is positioned on the seabed, and said method comprises:
 positioning the trenching wheel on the seabed;   pushing the trenching wheel into the seabed; and   moving the trenching device along the seabed to form the trench.   
     
     
         81 . The method according to  claim 80 , wherein the trenching device comprises a ballast, and the method comprises pushing the trenching wheel into the seabed by the weight of the ballast. 
     
     
         82 . The method according to  claim 80 , wherein the ballast is formed, or partly formed, by a ballast system configured to adjust the magnitude of the force of the ballast working on the base frame, and the method comprises adjusting the magnitude of the force of the ballast working on the base frame to push the trenching wheel into the seabed. 
     
     
         83 . The method according to  claim 82 , wherein the ballast system is configured to adjust the position of the force of the ballast working on the base frame, and the method comprises adjusting the position of the force of the ballast working on the base frame to push to trenching wheel into the seabed. 
     
     
         84 . The method according to  claim 82 , wherein the ballast system comprises a ballast tank configured to hold a fluid, and the method comprises filling the ballast tank with water to increase the magnitude of the force of the ballast working on the base frame, and the method comprises filling the ballast tank with air to decrease the magnitude of the force of the ballast working on the base frame and/or to create buoyancy such that the trenching device is neutrally buoyant or floats up in the water. 
     
     
         85 . The method according to  claim 80 , wherein the trenching device comprises a propulsion system formed by at least one propulsion unit connected to the base frame, and the method comprises moving the trenching device along the seabed with the propulsion system. 
     
     
         86 . The method according to  claim 85 , wherein the base frame comprises a first frame part and a second frame part which are connected to each other via a pivot connection, the trenching wheel is connected to the first frame part, at least one propulsion unit is connected to the second frame part, the trenching device comprises a steering system configured to pivot the second frame part relative to the first frame part, and the method comprises pivoting the second frame part relative to the first frame part to adjust the direction in which the trenching device is moved along the seabed.