US3411306A - Apparatus for laying submerged pipe - Google Patents

Description

Nov. 19, 1968 R. c. MosBY y 3,411,306

APPARATUS FOR LAYING SUBMERGED PIPE Filed July 7, 1965 5 Sheets-Sheet 2 1 INVENTOR. Ha/.Ld/ C'.` Mosby ATTORNEY @M2M/m R. C. MOSBY APPARATUS FOR LAYING SUBMERGED PIPE 5 Sheets-Sheet 3 Filed July '2, 1965 ATTR/VEY Nov. I 19,1 1968 R. c. MosBY APPARATUS FOR LAYING SUBMERGBD PIPE Sheets-Sheet 4 Filed July 7, 1965 vmm.

INVENTOR.

, ATTORNEY Nov'. 19, 1968 R. c. MosaY APPARATUS FOR LAYING SUBMERGED PIPE 5 Sheets-Sheet 5 Filed July 7, 1965 R. www %y..\ ma .1|\\ WM# w w .C my x ma mw w 1 V m. NMWN QMKVQS United States Patent O 3,411,306 APPARATUS FOR LAYING SUBMERGED PIPE Russell C. Mosby, Houston, Tex., assignor to Zapata Oif- Shore Company, Houston, Tex., a corporation of Delaware Filed July 7, 1965, Ser. No. 470,048 4 Claims. (Cl. 61'72.3)

ABSTRACTl OF THE DISCLOSURE A semisubmersible pipe laying bange has a longitudinally inclined ramp discharging at the lower front corner thereof and a sealed portion in which the pipe can be joined and coated below the water level.

This invention relates to apparatus for laying submerged pipe, particularly relatively large pipe of limited flexibility, in relatively deep waters which may be subjected to heavy wind, wave, and/-or storm action.

'Ihe usual procedure heretofore used in laying submerged pipe in deep water has been to feed the made-up pipe string from the end of the laying barge onto a ramp or other support means and thence to the underlying Water bottom at such an angle that the pipe is not excessively bent or otherwise s-trained in its suspended length between the barge and the water bottom or due to change of direction of the pipe as it is laid on the bottom. These methods have become more and 4more impractical .as the diameter and, therefore, the stiffness of the pipe being laid increases and also as the pertinent water depth increases. Furthermore, pipe support structures which project outwardly from the laying barge are diflicult to disconnect from the pipe when it is necessary to evacuate the scene because of an impending storm.

Accordingly, an object of the present invention is to provide novel apparatus for laying pipe such, for instance, as that used in gathering fluids from oifshore oil and gas wells.

Another object is to provide improved means for laying very large apipe under water for instance, pipe as large as 30 or 36 inches in diameter.

Another object is to provide means for laying submerged pipe wherein the angle of delivering of the pipe-laying structure does not become excessive even though the depth of the water in which the pipe is being laid varies considerably.

Still another object is to provide pipe-laying apparatusAwhic'h can be safely left at the scene in case it iS necessary for the pipe-laying personnel to -be quickly removed from the scene.

Still another object is to provide novel pipe-laying apparatus which is wholly self-contained, which can be floated to its work area, even through relatively shallow waters, land which can remain operative in relatively deep and troubled waters.

According to the present invention, there is provided a rigid, skeletonized |hull structure .made up of elongated, hollow members forming top and bottom hull portions and connecting vertical, longitudinal, and -other bracing elements where necessary. Extending diagonally through the structure is yan inclined, rigidly mounted pipe conveyor ramp on the upper portion of which pipe sections stored on the apparatus are connected to the pipe string on the ramy for periodical emission from the bottom end of the ramp. The angle of the ramp is designed with respect to the water depth in which the apparatus is intended to operate and the submerged height of the apparatus so that the pipe is delivered from the apparatus at an angle which does not unduly strain the pipe being laid. Furthermore, ballast carried in the hollow framing members can be 3,411,306 Patented Nov. 19, 1968 ICC adjusted so as to maintain the bottom of the apparatus at substantially a uniform -height above the water bottom which, accordingly, safely limits the free, unsupported length' of the pipe. Finally, in case of an impending storm, it ispossible simply to sink the apparatus :and carry the crew away in a workboat. When the storm has passed, the ballast pumps are operated to evacuate suicient of the ballast from the hollow framing members to raise the apparatus again to the desired height above the water bottom, whereupon pipe-laying operations can be promptly resumed.

In the accompanying drawings which illustrate the invention,

FIG. l is a perspective view of lan exemplary embodiment of the invention;

FIG. 2 is a ver-tical longitudinal central section through the apparatus;

FIG. 3 is -a plan view of the apparatus;

FIGS. 4 and 5 are transverse sections taken on the corresponding section lines of FIG. 3;

FIG. `6 is a horizontal section taken substantially on lines 6--6 of FIG. 2 and showing the bottom hull structure;

FIG. 7 is a section taken substantially on line 7-7 of FIG. 2 and showing the work, storage, and machinery areas; and

FIG. 8 is a diagram illustrating the manner of use of the apparatus.

The apparatus shown in the figures is intended for laying very large gas and/or oil gathering pipes in olfshore waters up to 240 feet or more in depth. The apparatus includes rigid framing forming a hull structure including a generally-horizontal bottom portion A, a top portion B, 1an inclined pipe conveyor ramp generally designated C, and deck stnicture D. Bottom hull structure A is formed of diverging, elongated, holow members 9 and 10 at the -rear end of the apparatus which merge with parallel front end members 11 and 12. The top hull structure consists of substantially smaller tubular members 13 and 14 continued forwardly by top sill members 15 and 16 upon which is supported the forward deck structure D. Larger, hollow, vertical columns 17, 18, 19, and 20 and intervening smaller posts 21 connect the top and bottom hull structures and transverse bracing members are provided at 22. Certain of the braces 22 are disposed to underlie and support ramp C. The bottom hull is additionally provided with diagonol bracing members 23 and the front end of the structure is provided with additional diagonal and vertical braces 24 and 25.

The inclined pipe conveyor ramp 26, 27 has suitable rollers or other elements, symbolized at 28 in FIG. 4, for facilitating sliding of the pipe string therealon-g. The ramp extends through a tubular housing 32 of large diameter which extends diagonally from the lower rear end of the rigid, buoyant framing structure to the upper, forward end there-of, the extreme upper portion 27 of the ramp being mounted above deck structure D upon an upstanding, triangular support 29. The lower delivery end 33 of housing 32 is provided with sealing means 34, as in FIG. 2, substantially at the lower end of the tubular housing. However, this sealing means may be provided at any point along the tubular housing and, in FIG. 8, is shown as at 34a substantially intermediately along the housing. The purpose of the seal is to exclude water from the portions of the ramp thereabove so that these portions can be used in making up and coating the pipe sections. A string of make-up pipe 35 rests on ramp 26 preparatory to emission from the lower end thereof through seal 34.

FIG. 7 shows the lower deck structure containing portions 36, 37, and 38 constituting work and pipe storage areas and portion 39 for accommodating the living quarters of the crew. A ballast pump 40 and operating engine 41 .are shown mounted on deck portion 38, and it will` be understood that suitable piping Will be provided for pumping water ballast both into and out of hollow framing members 9, 10, 17, 18, 19, and 20 for adjusting the draft of the apparatus, as will be explained. Also mounted on the deck structure a-re rotating cranes 4Z (FIG. 3) and other pipe-handling equipment for transferring pipe sections from the storage areas to the pipe make-up regions at the upper end 27 of the ramp. As will be well-understood, suitable space and equipment will be provided along the ramp for connecting the pipe sections serially to the pipe st-ring on the ramp and suitably coating and otherwise treating the pipe.

In use, the apparatus, with the ballast tanks evacuated to provide a sufficiently shallow draft, will be towed to the scene of operations. While the proportions and size of the apparatus will depend uopn the depth of water in which it is intended to be used and the characteristics of the pipe it is to lay, exemplary di-mensions are on the order of 600 foot length and 200 foot overall height. This apparatus will operate in water of approximately 24U-foot depth and with the ballast tanks filled will submerge until its bottom is approximately 40 feet from the water bottom and with the upper 40 feet of the structure projecting above the surface of the water as stabilizing freeboard. With the living and work quarters occupying the rear 20() feet of the vessel, the forward 400 feet would be, in effect, ramp support structure, though rigid with the remainder of the vessel. With the vessel so dimensioned, the ramp would be inclined at approximately 26 degrees from horizontal.

Wit-h reference to diagrammatic FIG. 8, there is shown a buoyant, skeletonized structure having an overall length of 600 feet and height of about 200 feet. This would provide for a ramp angle if approximately 26 degrees and a length of unsupported pipe between the end of the barge F and the water bottom at E f somewhat more than 200 feet. The sharpness of the curve at point E is affected both by the height of the pipe feed opening 33 at the bottom of the semi-submersible structure above the water bottom and the length of the structure. A smaller angle of ramp inclination may be necessary where very large and relatively stiff pipe is being laid.

In order to maintain only a safe length of the pipe unsupported as the water depth varies, it may be necessary to vary the draft `of the structure by adjusting the water ballast in the ballast tanks. Thus, the vessel may be utilized in a rather wide range of water depths. Also, where the pipe is to be laid in shallower water, the height and length of the vessel may be reduced.

It is desirable, of course, to make up as large a pipe string on the ramp as possible before moving the laying structure forwardly so as to discharge the pipe from the rear end thereof. The position of seal or water lock 34 or 34a will be adjusted to provide for the proper pipe makeup and pipe-treating area and this area, of course, may extend substantially below the surface of the water. Finally, in case the crew must leave the vessel, it is only necessary to fill the ballast tanks so as to drop the vessel to the bottom in which position it will ride out any storm without disconnection of the pipe string therefrom. When the crew returns, the ballast tanks are evacuated sufficiently to again elevate the vessel to the desired operating position. However, due to -t'he skeletonized lconstruction and the low center -of gravity, the vessel will be exceptionally stable, even in very rough water, so t-hat work may continue even when other types of vessels would have to leave the scene.

The invention may be modified in various respects as will occur to those skilled in the art, .and the exclusive use of all modifications as come within the scope :of the appended claims is contemplated.

I claim:

1. Apparatus for laying submerged pipe comprising an elongated, buoyant hull structure having a lower, normally submerged pipe delivery opening `at one end, fa pipe conveyor ramp rigidly mounted on said hull structure in a fixed, central position thereof and extending from said opening upwardly at an angle lengthwise of said structure, pipe line make-up and coating Imeans on the upper part of said ramp, `an enclosure for a part of said ramp, sealing Imeans in said enclosure for excluding water from at least said upper part of said ramA means for adjusting the water ballast in said hull structure to control the draft thereof, and means for transferring pipe sections to said ramp upper part for connection to a pipe string on said ramp.

2. Pipe-laying apparatus as described in claim 1 further including storage and working quarters on the upper par-t of said hull structure.

3. Apparatus for laying submerged pipe comprising a rigid framework of at least partially hollow members forming an elongated, skeletonized, buoyant hull structure, a pipe conveyor ramp rigidly mounted on said hull structure in a fixed, central position thereof and extending from one submerged end of said structure at the `bottom longitudinally and upwardly at an angle therethrough to an adjacent upper freeboard part of the structure, deck means on the upper part of said hull structure, storage` and working quarters on said deck means, means for transferring pipe sections to t-he upper part of said ramp for connection to a pipe string thereon, and means for adjusting the ballast in said hollow members to control the draft of said structure and, thereby, the length and curvature of pipe between the lower end of said ramp .and the underlying water bottom.

4. Apparatus for laying submerged pipe, as described in claim 3, further including enclosure -rneans for at least a portion of said ramp, and means sealing said enclosure means against entry of water into said portion whereby said portion may be utilized for makeup and coating of pipe on said ramp.

References Cited UNITED STATES PATENTS 1,152,326 8/1915 Lewis 61-72.4 2,910,835 11/1959 Timothy 61 72.3 3,082,608 3/1963 Danieli 6l-46.5 3,104,531 9/1963 McCammon 61-46.5 3,136,133 6/1964 Perret 61-723 3,214,921 1l/1965 Goepfert et al. 61-72.3 3,241,324 3/1966 Storm et al. 61-46.5 3,266,256 8/1966 Postlewaite et al. 6l-72.3 3,273,346 9/1966 Delaurelle et al 61-72.3 3,280,571 10/1966 Hauber et al. 61-72.1

FOREIGN PATENTS 885,276 12/1961 Great Britain. 947,196- 1/ 1964 Great Britain.

EARL I.A WITMER, Primary Examiner.

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