Method for converting a floatable barge into a semi-submersible vessel

• US 3,894,503 A
• Filed: 04/06/1973
• Issued: 07/15/1975
• Est. Priority Date: 04/06/1973
• Status: Expired due to Term

• Current Assignee: Alan C. Mcclure
• Original Assignee: Alan C. Mcclure
• Inventors: McClure, Alan C.
• Primary Examiner(s): Blix, Trygve M.
• Assistant Examiner(s): Frankfort, Charles E.
• Application Number:
  US05/348,594
• Time in Patent Office: 830 Days
• Field of Search: 114/.5D,43.5,77R,77A,65R 61/46.5,72.1,72.3 212/3
• US Class Current: 114/265
• CPC Class Codes: B63B 1/107 Semi-submersibles; Small waterline area multiple hull vessels and the like, e.g. SWATH
• CPC Class Codes: B63B 35/04 Cable-laying vessels
• CPC Class Codes: B63B 35/4413 Floating drilling platforms, e.g. carrying water-oil separating devices

Abstract

Methods and apparatus are provided for converting a floatable barge into a semi-submersible vessel. An independently floatable cradle unit is provided which has at least two submersible hulls, a plurality of support columns, transverse braces, and a buoyancy mechanism for selectively ballasting and de-ballasting the submersible hulls. The cradle unit is sunk or at least partially submerged and a barge is floated thereabove, whereupon the cradle is raised to lift the barge from the water. The barge is rigidly connected to the upper portions of the support columns. An inclined lay ramp and/or derrick may be mounted on the cradle to convert the barge into a semi-submersible lay or derrick vessel.

Claims

1. A method of converting a floatable barge having a working deck into a semi-submersible vessel comprising the steps of:

providing an independently floatable cradle unit having spaced horizontally elongate submersible hull members defining port and starboard submersible hull members, a plurality of columns extending vertically upwardly from each of said hull members to define port and starboard columns, transverse bracing means interconnecting said port columns with said starboard columns, said bracing means comprising lower transverse bracing, upper transverse bracing, and intermediate diagonal bracing, and buoyancy means for selectively ballasting and de-ballasting said submersible hull members;

actuating said buoyancy means to cause said cradle unit to partially sink within a body of water while maintaining said cradle unit positively buoyant, such that said submersible hull members are completely submerged, said upper transverse bracing defines a horizontally disposed support surface means disposed below the surface of the body of water between the port and starboard submersible hull members, and the upper ends of at least some of the columns of said submersible hull members extend above the water surface to define a barge receiving zone therebetween;

floating said barge on the body of water into said barge receiving zone between said port and starboard columns to orient the underside of said barge over said support surface means, while maintaining said cradle unit positively buoyant;

actuating said buoyancy means for de-ballasting said hull members and increasing the postive buoyancy thereof to;

raise said cradle unit in a manner bringing said support surface means into supporting contact with the underside of said barge, with said barge being located entirely between said port and starboard columns, and lift said barge from the surface of the body of water, so that said barge is carried above the water solely by buoyant forces acting on said support surface with said submersible hull members being floatingly disposed in said body of water; and

prior to the termination of said method, rigidly welding a plurality of extension frames between the upper portions of at least some of said port and starboard columns and the port and starboard sides of said barge, respectively, with portions of said extension frames being substantially flush with said working deck of said barge to define an extension of opposite sides of said working deck.

2. A method according to claim 1 wherein said step of providing said buoyancy means includes the steps of providing a plurality of ballast chambers and ballast pumping means in each hull, and communicating the ballast pumping means of each hull by conduit means extending through one of said brace beams.

3. A method according to claim 1 wherein the step of floating said barge includes the step of floating a barge having a rotary crane mounted on a working deck thereof with the rotary crane axis extending generally through the centerline of said barge.

4. A method according to claim 1 and further including the step of mounting a pivotal crane at least partially on the upper surface of one of said extension frames.

5. A method according to claim 1 wherein the step of floating said barge includes the step of floating said barge such that the centerline thereof is offset within said barge receiving zone;

and said step of rigidly welding includes the steps of welding a frame extension between the barge and the support columns at one side of said cradle unit and arranging an upper horizontal surface of said frame extension to extend along a substantial portion of the length of the barge generally flush with a working deck portion of said barge.

6. A method of converting a floatable barGe having a working deck into a semi-submersible lay vessel suitable for laying an elongate flexible means into a body of water, said method comprising the steps of:

providing an independently floatable cradle unit having spaced horizontally elongate submersible hull members defining port and starboard submersible hull members, a plurality of columns extending vertically upwardly from each of said hull members to define port and starboard columns, transverse bracing means interconnecting said port columns with said starboard columns, said bracing means including upper and lower transverse bracing and intermediate diagonal bracing, and an inclined lay ramp section supported by ramp-supporting portions of the columns of one of said submersible hull members, the ramp-supporting portions being arranged at levels of rearwardly diminishing height in accordance with the inclination of said ramp, and buoyancy means for selectively ballasting and de-ballasting said submersible hull members;

actuating said buoyancy means to cause said cradle unit to partially sink within a body of water while maintaining said cradle unit positively buoyant, such that said submersible hull members and said transverse bracing are completely submerged, said upper transverse bracing defines a horizontally disposed support surface means disposed below the surface of the body of water between the port and starboard submersible hull members, and the upper ends of at least some of the columns of said submersible hull members extend above the water surface to define a barge receiving zone therebetween;

floating said barge on the body of water into said barge receiving zone between said zone-defining port and starboard columns to orient the underside of said barge over said support surface means, while maintaining said cradle unit positively buoyant;

actuating said buoyancy means for de-ballasting said hull members and increasing the positive buoyancy thereof to;

raise said cradle unit in a manner bringing said support surface means into supporting contact with the underside of said barge, with said barge being located entirely between said port and starboard columns, and lift said barge from the surface of the body of water, so that said barge is carried above the water solely by buoyant forces acting on said support surface means with said submersible hull members being floatingly disposed in said body of water; and

at least prior to the termination of said method;

rigidly welding upper portions of said ramp-supporting columns to one side of said barge so as to establish a lay ramp that extends from an upper location substantially flush with said working deck to a lower position disposed below the underside of said barge for guiding elongate flexible means from said barge, and rigidly welding a plurality of extension frames between the upper portions of at least some of the columns located opposite said ramp supporting columns and the other side of said barge, with portions of said extension frames being substantially flush with said working deck of said barge to define an extension of said working deck.

7. A method according to claim 6 including the step of attaching a stinger mechanism to said cradle unit at the aft-most column supporting said ramp.