Trench cutter

A trenching device according to any preceding claim, wherein the one or more fluid pressurising means comprises a first fluid pressurising means and a second fluid pressurising means, and wherein:

• the first fluid flow path extends between the first fluid pressurising means and the one or more primary jetting outlets;
• and
• the second fluid flow path extends between the second fluid pressurising means and the one or more secondary jetting outlet.

A trenching device according to any preceding claim, comprising at least one valve located in the second fluid flow path wherein, when the trenching device is operated in the primary jetting configuration, the at least one valve prevents fluid flow along the second fluid flow path.

A trenching device according to any preceding claim, comprising at least one valve located in the first fluid flow path and wherein, when the trenching device is operated in the secondary jetting configuration, the at least one valve prevents fluid flow along the first fluid flow path.

A trenching device according to any preceding claim, wherein the trench forming jetting tool extends from the main body at a first position on the main body, and the jetting arm is connected to the main body at a second position which is separate to the first position.

A trenching device according to any preceding claim, wherein the jetting arm is movable between a stowed configuration and an operational configuration, wherein, for operation in the secondary jetting configuration the jetting arm is in the operational configuration.

A trenching device according to any preceding claim, wherein the jetting arm is an articulating arm.

A trenching device according to any preceding claim, wherein the jetting arm comprises a plurality of arm sections connected together by rotatable joints, wherein an end of one of the arm sections is mounted to the main body and wherein the jetting arm comprises an actuator associated with each rotatable joint, each actuator being configured to be actuated to rotate at least one of the arm sections attached to the respective rotatable joint about the respective rotatable joint.

A trenching device according to any preceding claim, wherein the jetting arm is rotatably mounted to the main body, and wherein the trenching device comprises an actuator connected between the jetting arm and the main body, the actuator being configured to be actuated to move the jetting arm relative to the main body.

A trenching device according to any preceding claim, wherein the first pressure is between and 16 bar, and the second pressure is between 12 and 120 bar.

A method of forming an underwater or subsea trench, the method comprising:

• providing a trenching device on a floor in which the trench is to be formed;
• operating the trenching device in a primary jetting configuration in which material is cut or fluidised adjacent to a trench-forming jetting tool which extends from a main body of the trenching device and into the floor to form the trench, wherein cutting or fluidising material adjacent the trench-forming jetting tool is by ejecting fluid, at a first pressure, from one or more primary jetting outlets arranged along a length of the trench-forming jetting tool;
• operating the trenching device in a secondary jetting configuration wherein material is cut or fluidised adjacent to one or more secondary jetting outlet of a jetting arm of the trenching device, an end of the jetting arm being connected to the main body of the trenching device, wherein cutting or fluidising material adjacent the one or more secondary jetting outlet is by ejecting fluid, at a second pressure which is greater than the first pressure, from the one or more secondary jetting outlet.