Monitor for and method of deploying anchor lines for off shore platforms

• US 4,755,947 A
• Filed: 03/03/1986
• Issued: 07/05/1988
• Est. Priority Date: 03/03/1986
• Status: Expired due to Fees

• Current Assignee: Parmac Incorporated
• Original Assignee: Parmac Incorporated
• Inventors: Hougland, Fredrick G., Braschler, Steve A.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/835,728
• Time in Patent Office: 855 Days
• Field of Search: 364/424, 364/432, 364/449, 364/550, 364/138, 364/139, 405/154, 405/158, 405/160, 405/165, 405/166, 405/168, 405/177
• US Class Current: 701/116
• CPC Class Codes: B63B 2021/505 Methods for installation or mooring of floating offshore platforms on site
• CPC Class Codes: G05D 1/0208 dynamic anchoring

Abstract

A method and apparatus, utilizing a computer are utilized to control the placement of an anchor, and its associated anchor line for proper payout, deployment and ultimate placement of the anchor, depending upon the contour of the sea bottom and to maintain a desired catenary curvature that prevents the anchor line from dragging the sea bottom and further prevents undue strain upon the anchor chain beyond its safe tension force.

Claims

1. A method for controlling the placement of an anchor and its anchor line to a known anchor drop point from a vessel to be anchored that is situated in a body of water such as the ocean and utilizing an anchor handling support vessel with the aid of a digital computer mathematically programmed to at least calculate at different intervals, distances between said vessel and said anchor handling support vessel (XT) and bollard pull (H) acting on said workboat, comprising:

providing said computer with data that includes location of said anchor drop point from said vessel, the depth and contours of the ocean bottom from said vessel to said anchor drop point the weight per foot of said anchor line, and the total length of said anchor line to be payed out,

constantly monitoring at said different intervals the distance between said vessel and said anchor handling support vessel and the length of said anchor line payed out by said anchor handling support vessel,

providing said computer with said monitored information as to said distance between said vessel and said support vessel and the length of said anchor line payed out,

repetitively calculating in said computer, at desired intervals, the catenary curvature of said anchor line at each of said intervals, and

separately controlling the speed of payout of said anchor line to maintain a catenary curvature thereof that prevents undue strain upon said anchor line beyond its breaking strength and excessive bollard pull upon said support vessel.

2. A method for controlling the placement of an anchor and its anchor line to a known anchor drop point from a vessel to be anchored that is situated in a body of water such as the ocean and utilizing an anchor handling support vessel with the aid of a digital computer mathematically programmed to at least calculate at different intervals, distances between said vessel and said anchor handling support vessel (XT) and bollard pull (H) acting on said workboat, comprising:

providing said computer with data that includes location of said anchor drop point from said vessel, the depth and contours of the ocean bottom from said vessel to said anchor drop point, the weight per foot of said anchor line and the total length of said anchor line to be payed out,

constantly monitoring at said different intervals the tension upon and the length of said anchor line payed out by said anchor handling support vessel,

providing said computer with said monitored information as to said tension and length of said anchor line payed out,

repetitively calculating in said computer, at desired intervals, the catenary curvature of said anchor line at each of said intervals, and

separately controlling the speed of payout of said anchor line to maintain a catenary curvature thereof that prevents undue strain upon said anchor line beyond its breaking strength and excessive bollard pull upon said support vessel.

3. The method of claim 2 wherein said vessel is a floating vessel.

4. The method of claim 2 wherein said vessel is a semi-submersible drilling platform.

5. The method of claim 2 wherein the said data includes the total length of said anchor line on board said vessel to be anchored.

6. The method of claim 2 including the step of creating a visual display of said catenary curvature of said anchor line that has been payed out relative to said depth of the ocean bottom and the location of said support vessel.

7. The method of claim 6 wherein said visual display is on a cathode ray tube.

8. The method of claim 6 wherein said visual display is a printed display.

9. The method of claim 6 including the step of telemetering or transmitting said visual display to said anchor handling support vessel.

10. An apparatus for controlling the placement of an anchor and its anchor line to a known anchor drop point from a vessel to be anchored that is situated in a body of water such as the ocean and utilizing an anchor handling support vessel with the aid of a digital computer mathematically programmed to at least calculate at different intervals, distances between said vessel and said anchor handling support vessel (XT) and bollard pull (H) acting on said workboat, comprising:

said computer having a data base means programmed to receive data that includes location of said anchor drop point from said vessel, the depth and contour of the ocean bottom from said vessel to said anchor drop point, the weight per foot of said anchor line, and the total length of said anchor line

electrical signal means to monitor at said different intervals of time the distance between said vessel and said anchor handling support vessel and the length of said anchor line,

means to provide said computer with said monitored information as to said distance between said vessel and said anchor handling support vessel and the length of said anchor line,

means to repetitively calculate in said computer, at said desired intervals, the catenary curvature of said anchor line at each of said intervals, and

brake means to control the speed of payout of said anchor line to maintain a catenary curvature thereof that prevents undue strain upon said anchor line beyond its breaking strength and excessive bollard pull upon said support vessel.

11. An apparatus for controlling the placement of an anchor and its anchor line to a known anchor drop point from a vessel to be anchored that is situated in a body of water such as the ocean and utilizing an anchor handling support vessel with the aid of a digital computer mathematically programmed to at least calculate at different intervals, distances between said vessel and said anchor handling support vessel (XT) and bollard pull (H) acting on said workboat, comprising:

said computer having data means that includes location of said anchor drop point from said vessel, the depth of the ocean bottom from said vessel to said anchor drop point, the weight per foot of said anchor line, and the total length of said anchor line,

electrical signal means to monitor at said different intervals of time the tension upon the length of said anchor line,

means to provide said computer with said monitored information as to said tension and length of said anchor line,

means to repetitively calculate in said computer, at said desired intervals, the catenary curvature of said anchor line at each of said intervals, and

brake means to control the speed of payout of said anchor line to maintain a catenary curvature thereof that prevents undue strain upon said anchor line beyond its breaking strength and excessive bollard pull upon said support vessel.

12. Apparatus of claim 11 wherein said vessel is a floating vessel.

13. Apparatus of claim 11 wherein said vessel is a semi-submersible drilling platform.

14. Apparatus of claim 11 wherein said data includes the total length of said anchor line on board said vessel to be anchored.

15. Apparatus of claim 11 including visual display means of said catenary curvature of said anchor line that has been payed out relative to said depth of the ocean bottom and the location of said support vessel.

16. Apparatus of claim 15 wherein said visual display is a cathode ray tube.

17. Apparatus of claim 15 wherein said visual display is a printed display.

18. Apparatus of claim 15 including means to telemeter or transmit said visual display to said anchor handling support vessel.