Subsea clearing apparatus

Abstract

A subsea clearance apparatus ( 1 ) includes a chassis ( 2 ), fore and aft skids ( 3, 4 ) spaced along a principal axis (P) of the apparatus ( 1 ), and a pair of flanks ( 22 a, 22 b ) with a plurality of tines ( 5 ) depending from the flanks ( 22 a, 22 b ). The tines ( 5 ) are spaced transversely with respect to the principal axis (P) and pitched toward the fore of the apparatus ( 1 ). In use, the chassis ( 2 ) is spaced from the seabed (S) by the skids ( 3, 4 ) as the apparatus ( 1 ) is propelled therealong such that the tines ( 5 ) engage and deflect away from the principle axis (P) obstructions which are larger than a predetermined size and which protrude by a predetermined amount from the seabed (S).

What is claimed is: 
     
         1 . A subsea clearance apparatus comprising a chassis, fore and aft supports spaced along a principal axis of the apparatus and one or more engaging elements depending from the chassis and arranged transversely with respect to the principal axis, wherein the chassis is spaced, in use, from the seabed by the supports as the apparatus is propelled therealong such that the engaging elements engage and deflect away from the principle axis obstructions which are larger than a predetermined size and/or which protrude by a predetermined amount from the seabed. 
     
     
         2 . A subsea clearance apparatus according to  claim 1 , wherein the engaging elements comprise a plurality of tines which are spaced transversely with respect to the principal axis. 
     
     
         3 . A subsea clearance apparatus according to  claim 2 , wherein the chassis comprises a pair of flanks and the tines depend from the flanks. 
     
     
         4 . A subsea clearance apparatus according to  claim 3 , wherein the tines are angled or pitched toward the fore of the apparatus. 
     
     
         5 . A subsea clearance apparatus according to  claim 4 , wherein the tines are configured such that they are spaced, in use, from the seabed. 
     
     
         6 . A subsea clearance apparatus according to  claim 5 , wherein the space between the tines and the seabed is adjustable. 
     
     
         7 . A subsea clearance apparatus according to  claim 6 , wherein the space is adjustable by adjusting the angle or pitch of the tines. 
     
     
         8 . A subsea clearance apparatus according to  claim 6 , wherein the space is adjustable by adjusting the height of the fore and/or aft support. 
     
     
         9 . A subsea clearance apparatus according to  claim 3  comprising a cross-brace interconnecting the flanks. 
     
     
         10 . A subsea clearance apparatus according to  claim 9 , wherein each flank comprises one or more modular segments for adjusting the swept width of the apparatus. 
     
     
         11 . A subsea clearance apparatus according to  claim 3 , wherein the fore and aft supports each comprise a pair of skids on either side of the principal axis of the apparatus, the chassis comprising a pair of longitudinal members each having one of the fore skids mounted thereto and each aft skid being mounted to one of the flanks. 
     
     
         12 . A subsea clearance apparatus according to  claim 11 , wherein each of the aft supports comprises a keel plate. 
     
     
         13 . A subsea clearance apparatus according to  claim 11 , wherein each of the pair of fore supports is rotatable about a steering axis for steering the apparatus. 
     
     
         14 . A subsea clearance apparatus according to  claim 11 , wherein each of the pair of fore supports is tiltable about an axis parallel, in use, with the seabed. 
     
     
         15 . A subsea clearance tool according to  claim 1 , wherein the chassis comprises a hollow, floodable portion. 
     
     
         16 . A subsea clearance tool according to  claim 1  comprising a cradle configured to receive a remotely operated vehicle. 
     
     
         17 . A method for clearing a seabed, the method comprising lowering a subsea clearance apparatus from a vessel to a seabed, propelling the apparatus along the seabed such that one or more engaging elements engage and deflect away from a principal propelling axis obstructions which are larger than a predetermined size and/or protrude by a predetermined extent from the seabed. 
     
     
         18 . A method according to  claim 17 , wherein the engaging elements comprise tines and the method comprises maintaining the tines in a spaced relation relative to the seabed as the apparatus is propelled therealong. 
     
     
         19 . A method according to  claim 18  comprising adjusting the space between the tines and the seabed before, during or after the apparatus is propelled therealong. 
     
     
         20 . A method according to  claim 19  wherein the space between the tines and seabed is adjusted by adjusting the angle or pitch of the tines and/or the height of a chassis from which the tines depend. 
     
     
         21 . A method according to  claim 17 , wherein the apparatus is steered while being propelled along the seabed by rotating one or more fore supports of the apparatus about respective steering axes. 
     
     
         22 . A method according to  claim 17  comprising at least partially flooding the apparatus before, during or after the apparatus is deployed to the seabed. 
     
     
         23 . A method according to  claim 17  comprising locating a remotely operated vehicle within a cradle of the apparatus before, during or after the apparatus is lowered to the seabed. 
     
     
         24 . A method according to  claim 23 , wherein the remotely operated vehicle controls one or more actuators of the apparatus and/or relays data to a remote computer. 
     
     
         25 . A method according to  claim 17 , wherein the apparatus is lowered using a crane.