Sea sled with jet pump for underwater trenching and slurry removal

A device for making trenches in the bottom of the sea and for removing slurry formed during making such trenches comprising:

• support means adapted to be drawn by a vessel and move on the sea bottom;
• a plurality of outlet nozzles on said support means for high pressure water to be supplied through same by means of a hose from the vessel for the production of the trench by swilling;
• a plurality of suction tubes, each having associated therewith a jet pump operated also from the same high pressure water supply used for displacing slurry made up of trenching spoil mixed with water;
• each such jet pump comprising two nozzles which are arranged substantially coaxially in tandem with means for adjustable spacing between the nozzles to provide a free intermediate space which is in communication with the surrounding seawater in trenching operation, each said suction tube having a bent portion with the front nozzle of said tandem nozzles being introduced at the bent portion of the suction tube from the side thereof and into the same substantially coaxially.

An entrenching and pipeburying system comprising:

• a surface floating vessel, a sea sled for excavating a trench below a pipeline laid along the sea bottom and for removing the slurry formed by the excavation;
• means carried by said vessel for raising and lowering the sea sled respectively from and to the sea bottom;
• means carried by said sled for excavating the trench and including a plurality of jet nozzles directed to flow high pressure fluid below the pipeline to fluidize the sea bottom and form a slurry;
• means carried by said sled for removing the slurry including a plurality of suction conduits each having an inlet disposed below said sled and a discharge portion;
• a plurality of jet pumps carried by said sea sled, each jet pump including a pump nozzle having an inlet external to each suction conduit and exposed to the ambient fluid with said pump nozzle having an outlet within said conduit for delivery of fluid to said suction conduit intermediate said inlet and discharge portions thereof and a second nozzle carried by said sled external to said conduit and spaced a predetermined distance from said inlet of said first-mentioned pump nozzle to provide a free space;
• means carried by said surface vessel for supplying low volume high pressure fluid to each said second-mentioned nozzle of each said jet pump and to said jet nozzles, each said second-mentioned nozzle being disposed to flow the supply fluid towards said first-mentioned pump nozzle inlet and across the space therebetween to entrain ambient fluid and deliver the entrained fluid and at least a portion of the supply fluid through the first-mentioned pump nozzle into said conduit.

An entrenching and pipeburying system comprising:

• a surface floating vessel;
• a sea sled for excavating a trench below a pipeline laid along the sea bottom and for removing the slurry formed by the excavation;
• means carried by said vessel for raising and lowering the sea sled respectively from and to the sea bottom;
• means carried by said sled for excavating the trench and including a plurality of jet nozzles directed to flow high pressure fluid below the pipeline to fluidize the sea bottom and form a slurry;
• means carried by said sled for removing the slurry including a plurality of suction conduits each having an inlet disposed below said sled and a discharge portion;
• each suction conduit having associated therewith a jet pump operated also from the same high pressure water supply used for displacing slurry;
• each such jet pump comprising two nozzles which are arranged substantially coaxially in tandem with means for spacing the nozzles apart to provide an intermediate free space which is in communication with the surrounding seawater in trenching operation, each said suction conduit having a bent portion with the front nozzle of said tandem nozzles being introduced at a bent portion of the suction conduit from the side thereof and into the same substantially coaxially;
• means carried by said surface vessel for supplying low volume high pressure fluid to each said second-mentioned nozzle of each said jet pump, each said second-mentioned nozzle being disposed to flow the supply fluid towards the inlet of said front nozzle and across the space therebetween the entrain ambient fluid and deliver the entrained fluid and at least a portion of the supply fluid through said front nozzle into said conduit.

Apparatus for use in making a trench in a sea bottom and for removing spoil formed during making such a trench, said apparatus comprising in combination;

• a surface floating vessel;
• a tow for excavating a trench for a pipeline laid along the sea bottom and for removing the spoil formed by the excavation, said tow having a base structure adapted to slide on the sea bottom;
• means carried by said vessel for raising and lowering the tow, respectively, from and to the sea bottom;
• means carried by said tow for excavating the trench and including outlet nozzles with means for receiving from the vessel a high pressure supply of water and for emitting said high pressure water supply through said nozzles for production of a trench by jetting;
• means for removing the spoil and carried by said tow, said spoil removing means being in duplicate and being so supported by the tow as to be in substantially side by side relationship relative to the direction of slide of the tow, each spoil removing means comprising a suction tube having a bent portion merging with an eductor tube section, a jet pump associated with said suction tube and comprising first and second nozzles which are arranged substantially coaxially in tandem, at least part of the jet pump being exposed to ambient water during a trenching operation, the first nozzle projecting through a side of said second suction tube into the bent portion and extending in the direction of the outlet of the educator tube section, and means associated with the second nozzle for receiving said high pressure water supply from the vessel;
• and
• guide means carried by said base structure for maintaining said tow in alignment with the pipeline as the trench is excavated and adapted to straddle the pipeline;
• a frame for supporting said trenching means, said spoil removal means and said guide means;
• and means for adjusting the elevation of said frame relative to said base structure thereby to adjust the elevation of said outlet nozzles, said suction tube inlets and said guide means relative to said base structure;
• each of said suction tube inlets having an aperture opening in a lateral inward direction relative to the longitudinal sides of the tow, with said apertures lying in substantial lateral register one with the other.

Apparatus for use in making a trench in a sea bottom and for removing spoil formed during making such a trench, said apparatus comprising:

• at least one suction tube having a bent portion merging with an eductor tube section;
• a jet pump associated with said suction tube and comprising first and second nozzles which are arranged substantially coaxially in tandem, such that there is a free intermediate space between adjacent portions of said first and second nozzles which is intended to be exposed to ambient water during a trenching operation, the first nozzle projecting through a side of said suction tube into the bent portion and extending in the direction of the outlet of the eductor tube section;
• and
• means associated with the second nozzle for receiving a high pressure supply of water to cause said water supply to flow through said nozzles to entrain ambient water and to cause spoil produced during the trenching operation to flow through the suction tube to be entrained with said water supply and ambient water and discharged through the eductor tube section.