Method and apparatus for removal of submerged offshore objects

A cannister for use in removing support structures including metal piles embedded within a seabed comprising:

• said cannister having a body of predetermined internal volume for holding liquified gas, said body being formed from a top, sides and a bottom sized to fit within one of said piles,
• said cannister being composed of material capable of withstanding low temperatures without embrittlement,
• said sides having nozzle means to discharge liquid contained in said cannister,
• inlet means positioned on said body to permit the pressurizing gas to be admitted to said internal volume,
• support means on said body for raising and lowering said cannister within at least one of said piles, and
• the construction and arrangement being such as to permit said cannister containing liquified gas to be forced out of the nozzle means by the pressurizing gas to contact said pile for chilling the pile to or below its embrittlement temperature resulting in fragmentation of the pile.

Apparatus for use in removing support structures including metal piles embedded within a seabed comprising:

• a cannister having a body of predetermined internal volume for holding liquified gas, said body being formed from a top, sides and a bottom sized to be lowered into one of said piles,
• said cannister being composed of material capable of withstanding low temperatures without embrittlement,
• said sides having nozzle means to discharge liquid contained in said cannister,
• inlet means positioned on said body to permit a pressurizing gas to be admitted to said internal volume to discharge said liquified gas,
• support means on said body for raising and lowering said cannister within at least one of said piles,
• cable means secured to said support means to raise and lower said cannister through said pile,
• conduit means secured to said inlet means and of sufficient length to extend above the water surface, and
• the construction and arrangement being such as to permit said cannister to be lowered within a pile for liquified gas to be forced out of the nozzle means of said cannister by the pressurizing gas in order to contact said pile for chilling the pile to or below its embrittlement temperature allowing subsequent fragmentation of the pile and removal thereafter.

A method of removal of large metal objects embedded in or substantially immobile on a seabed comprising:

• dislodging at least a portion of the environment in contact with at least a portion of said object,
• injecting a liquified gas into said environment as dislodged in a sufficient amount to embrittle said object portion,
• contacting said object portion within said dislodged portion with said liquified gas for a sufficient time to cryogenically embrittle said object portion,
• fragmenting said object portion due to said embrittlement by application of force, and raising and removing the remaining nonfragmented object.

An underwater fragmentation tool for use in a sea upon a submerged object having an embrittled area, comprising:

• at least two anvils each having both a contact face for striking said object in said embrittled area and a propulsion face for receiving a propelling force to move each anvil in the direction of said embrittled area;
• direction controlling means operative upon said anvils for directing and controlling the movement of said anvils toward the embrittled area;
• propulsion means cooperating with said direction controlling means for applying a propelling force to said propulsion face of said anvils;
• and
• timing means for controlling the movement of said anvils, said timing means including a reduced diameter frangible rod connecting opposed anvils
• whereby, upon said fragmentation tool being positioned toward said embrittled area and said propulsion means being activated, the frangible rod retains the anvils within the tool for a predetermined time until a sufficient propulsion force is applied to the propulsion face of each anvil to rupture the frangible rod and move the contact face of each anvil into striking engagement with the embrittled area of said submerged object to cause fragmentation.

A method for fragmenting and thereafter removing a submerged structure embedded in or on a sea bottom, comprising:

• contacting a portion of said structure with an embrittling agent for sufficient time to create an embrittled area on said structure,
• positioning at least one anvil adjacent said embrittled area for striking said embrittled area,
• propelling said at least one anvil with high propulsion force to strike said embrittled area,
• directing the path of said at least one propelled anvil toward said embrittled area, and
• impacting said embrittled are with said at least one anvil to fragment said embrittled area and permit removal of said structure.

An underwater fragmentation tool for use in a sea upon a submerged object having an embrittled area, comprising:

• at least one anvil having both a contact face for striking said object in said embrittled area and a propulsion face for receiving a propelling force to move said anvil in the direction of said embrittled area;
• and
• direction controlling means operative upon said at least one anvil for directing and controlling said anvil movement toward the embrittled area;
• propulsion means cooperating with said direction controlling means for applying a propelling force to said propulsion face of said at least one anvil;
• and
• timing means secured to said tool and positioned for controlling the application of said propelling force to said propulsion face of said at least one anvil, said timing means being defined by a frangible disc interposed between said propulsion means and said at least one anvil whereby when such gaseous pressure reaches a predetermined level said frangible disc ruptures to expose the propulsion face of said at least one anvil to said propelling force applied by said gaseous pressure.