Spacers for vertically moored platform riser bundles

• US 3,993,273 A
• Filed: 07/28/1975
• Issued: 11/23/1976
• Est. Priority Date: 07/28/1975
• Status: Expired due to Term

• Current Assignee: Amoco Corporation (BP PLC)
• Original Assignee: Standard Oil Company (BP PLC)
• Inventors: Dade, John Thomas
• Primary Examiner(s): Foss, J. Franklin
• Application Number:
  US05/599,907
• Time in Patent Office: 484 Days
• Field of Search: 248/68, 114/.5 D, 61/46.5, 61/46.6, 166/.5, 166/.6
• US Class Current: 405/195.1
• CPC Class Codes: B63B 2021/505 Methods for installation or mooring of floating offshore platforms on site
• CPC Class Codes: B63B 21/502 by means of tension legs

Abstract

This invention relates to a structure floating on a body of water and particularly a structure for drilling or producing wells from below the water. Buoyant members support at least a part of the structure above the surface of the water. The structure is connected to anchors or weights in the floor of the body of the water by a series of parallel leg members, usually four in number, forming a rectangular spacing. Each leg member is composed of a plurality of elongated members, such as large-diameter pipe, usually called risers. These risers are parallel. Vertically spaced spacers are provided along the riser of each leg to maintain the risers a fixed distance apart and to change the natural or resonant frequency of the individual riser pipes to be greater than the flutter frequency caused by the motion of the water past the riser. Novel spacers are provided and described which can be set in place without use of divers.

Claims

1. A spacer for use with a bundle of a plurality of riser pipes used between a vessel floating on a body of water and the bottom thereof which comprises:

a. a frame means having a plurality of vertical passages therethrough, there being a passage for each said riser pipe;

b. first means remotely operable for centering each said riser pipe after it is extended through its vertical passage; and

c. second means for securing each said riser to said frame means.

2. A spacer as defined in claim 1, in which each said vertical passage is circular in cross section, and wherein said first means includes a plurality of arms directed toward the center of said vertical passage, the arms being limited to extend into the passageway a distance equal to one-half the difference in diameter between said riser pipe and said vertical passage.

3. A spacer as defined in claim 1, wherein said second means includes two blocks, each connected to a hydraulic arm, the inner end of said block having a cross section shaped as a semicircle to engage said riser pipe.

4. A spacer as defined in claim 3, in which said semicircle portion is provided with an inflatable bag and including means to inflate said bag.

5. A spacer as defined in claim 3 including means to lock said blocks in their innermost position.

6. A spacer as defined in claim 5 including means to release said blocks from their locked position.