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Патент USA US3021874

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Feb. 20, 1962
Filed May 2, 1958
2 Sheets-Sheet 1
Far/v /e J. you/79
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Feb. 20, 1962
Filed May 2, 1958
2 Sheets-Sheet 2
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Far/v /e J’. Vela/79’
U?it?d States Patent 0 _"ice,
V _. Patented Feb. 20, 1962
Another object is to provide a pipeline which is buoy
ant and which will be maintained between a predeter
mined high‘ and low 'level by‘ a novel anchoring system.
Farrile S. Young, Houston, Tex., assignor to Gulf-Inter
Another object is“ to provide av pipeline for marine
state Oil Company, Houston,- Tex., av corporation of 5 service
which is easy to locate and raise after it is in
I service,‘ should the occasion arise.’
Filed May 2, 1958, Ser. No. 732,497
4 Ciaims.
a " "
This invention relates to pipelines and 'more particu
larly to pipelines crossing very deep bodies‘ of water. 10
Another object is to provide a pipeline for marine
service‘ in which a thinner wall pipe can be used for a
particular service as compared to a pipe designed for
laying on bottom.
Pipelines have been laidin shallow water. These lines
In accordance with this invention the pipeline is
are usually weighted and rest on bottom. Frequently i’ ’ , designed with buoyancy. It is anchored in place with a
they are buried in the soil below the body of water. This‘
plurality of anchors which are upstream of the pipe a
conventional practice cannot be followed. in deep water
considerable distance and connected to. the pipe by
such‘ as the Yucatan Straits, Mediterranean, etc. because 15 cable. The normal current‘will, cause'the pipe to sink
of the many problems encountered in deep water. vFor
to a predetermined ‘level. A second anchoring system
instance, the crushing pressure of water‘at great depth
is provided which limits" the level to which the pipeline‘
ishigh. This pressure'varies with the contour of the
may rise in the event current ,?ow reduces or ceases
bottom and would require the‘ line to bede'signedzfor the
greatest depth expected. In-the Yucatan Straits this 20 'Flexible’connections are provided at spaced points to
would be in the order of 6,700 ft. At this depth there. - permit the pipeline to conform to the force conditions
is approximately 3,000 psi. crushing pressure which
to whichgit is subjected. ’
' would require 7A inch wall thickness when using grade
'Che'ck valves positioned at spacedpoints permit the
B 12-inch pipe with‘ a nominal safety factor of 1.25.
testing of sections of the line as it is being laid and
Very high stresses wouldbe caused in suspending long 25 prevent ?ooding of the entire line in the event of a leak
lengths 'of such pipe o'? of a laying'barge to the'bottom_.
after the line has been put in service‘.
Bending forces many times the yield strength‘of the pipe" " -' jlifeferring now'to the drawings wherein there is shown
would be developed. The high bending forces could'
an illustrative embodiment of this invention and wherein
only’be eliminated by utilizing a ?eet of crane barges.
Keeping these barges effective-in the surface'currents
such as the six mile per hour current in the. Yucatan
Straits would be a very difficult assignment. 'Addi-‘
tionally, large bending forces would be‘ developed due.
to the pipe conforming to the unknown roughness of the."
like reference numerals indicate like parts:
‘FIGURE. 1- isv a ‘cross-sectional view illustrating a
pipeline suspended at an‘ intermediate level and crossing
7‘ a deep body of water;
'FIGURE 2 vis a sectional view taken at right angles
to FIGURE -1 and showing three ‘different positions of‘ '
bottom. In manyvv cases sharp ‘cliffs are present in deep 35 the pipelineunder three different current conditions; and
FIGURE 3v is a- perspectiveview of the‘ pipeline and
water which are hard to ‘detect and'avoid. ' Long spans
anchoring system.
of pipe,‘ over ‘the sharp depressions could cause su?icie'nt
forces to kink the pipe, with possible rupturing occurring."
The pipeline indicated generally at 10 ,(is made up of’
Another'factor to consider in'deep‘water is high oscil-'
a plurality of-"sections'; someof which are shown at '11,?
lating forces near ‘the bottom. These forces place high 40 12, 13 and 14. Each section‘of the pipeline is fabricated ‘1
strains on the ‘pipe especially when rigi'dzpipe spans
in the conventionalmanner by welding together short
sections‘ of the bottom and is anchored at each' end by
silt. ‘In the event of sudden rough water vgreat di?i
lengths of pipe.
‘At periodic intervals .the ‘sections of the pipeline 10
culty would be experienced inreleasing and later reclaim—
are connected together by ?exible connectors 15. These
ing a pipeline. ‘Picking a pipe o? of the bottom of 45 connectors permit thesections of pipe to bend relative: 6,700 ft. of water without ‘kinking it would be an expen
to each other ‘and move with the-variable currents which
sive time-consuming job, if even‘possible.
' ‘
are keeps
the stressThe
in- the provided
pipe at“
It is an object of this invention to provide a pipeline
for crossing deep bodies of water.
,i ' >
safe levels. Tht-?exiblev connections permit the laying
Another object provide a pipeline which is below’ 50 or‘ taking up of the pipe without over-bending and stress- ' .
the level of the surface but which‘ is above bottom where
ing the metallic rigid pipe sections and permit the han—' uncontrollable .scouring,_spans, sharp bends and‘, high, * dling ‘of ‘long lengths at great depths. The number of
?exible connectors 15 employed will preferably be‘ kept
oscillating'forces can occur.
to a minimum, but’ as many as necessary to give a line
Another object is to provide a pipeline for deep water
which is maintained at a uniform controlled depth that’ 55 the desired ?exibility maybe emp10yed_ . .:. ,.
The‘pipeline‘ 10' ' compartmented byla plurality of
will ?t the crushing strength of the pipe wall. 7
Another object is to provide a pipeline having ?exible - check valves-‘16 which control ?ow through the'pipeline
and ‘are preferably spaced along its entire length. These
connections at spaced points to allow the pipeline‘ to_
move with the variable currents which are encountered
check valvespermit ?ow‘from the source of vthe ?uid 1'
and keep the stress level of thepipe at a relatively low, 60 to' be pumped to'its destination or tevrmina1.-'--v The check valves are preferably positioned every half mile or so a
Another-'object is to providea
pipeline suspended at
an intermediate level in a body of water in which the
stress level of the pipe due to the means for anchoring‘
the pipe in position is at-a relatively low value.‘
Another object is to provide a pipelineyfor suspending
to permit ‘pressure testing of half-mile sections of- pipe
and to provide compartments of'app'roximately one-half
mile length to prevent ?ooding‘of the entire pipeline'if
a break occurs. When in service the gas pressure in the
at an intermediate level in a body of water which is‘
line- will be much greater than the hydrostatic pressure
;exerted by the water‘ surrounding the line. Thus if'a
compartmented to prevent the line from sinking to bot—
break occurs, the downstream check valve will be imme
diately closed by the high pressure in the line downstream
Another object is to provide a‘ marine pipeline in 70 of the valve.- The terminal ‘outlet from the line would
of course be closed'rupon a break occurring to trap this
which each section ‘may be pressured and tested before
high pressure within the line and prevent ?ooding of the
it is lowered into ?nal position.’ I .'
tom should a break occur.
extend between the respective anchors '18 and 19 and
line downstream of the break. The line would be closed
o? at its upstream endto permit gas pressurew'ithin the
upstream section of the line to bleed down.
‘a common point 21 at which they are 'joined together. " A
single cable 22 extends from this point of joinder to the
As soon
pipeline :10.
as this pressure is reduced below the hydrostatic pressure
of the surrounding water, the upstream yalye adjacent
In order that the lines 20 ‘be as short as possible, the
point 21 is selected at maximum distance from the pipe
line :110. ;For_ :instance with ‘the cable 17 ‘extending. at
an angle :of 27 degrees, the point 21 could ‘be approxi
buoyancy of the remainderof the pipe would prevent .the
entire pipeline from sinking.’ Of course the .buoyant'pipe
mately 2,200 ft. from the pipeline and cable '20 would
line would tend to support the section which had ?lled 10 have a length?of'lapproximately 4,000 ‘ft; A ‘further ad
vantage of this system is that a single line to the pipe
with water until the leaky section could .be repaired.
a break would close. Thus, only the section ofpipe be
tween .two adjacent check valves would flood, .and the’
The pipeline is anchored in position with a system of
cannot set up opposing stresses. Where two cables :are
I attached to the pipe at .or close to each other, opposing
anchors which maintain the pipeline between ,a ,prede.
termined high and low level beneath the surface of ,the
In straits and narrow seas for which this pipe
stresses are possible. ’
The dead weight of cables 17, 20 and 22 will'be con
line is eminently suited, arather constant currentis usually
present. In designing the pipeline, this current .is taken
into consideration. The buoyancy of the pipeline and
the angle which the primary anchoring cable 17 makes
' siderable and if supported by the pipe would cause 'it to
as low as possible so as .to have minimum horizontal
heats 24 attached to cables .22 immediately adjacent the
pipeline 1.0.
assume'a con?guration resembling a succession of arcs.
This isundesirable, as stresses in the ,pipe should ‘,bemain
tained at a minimum. Therefore, it is preferred to ‘pro
with the v‘bottom are designed .to “maintain the pipeline 20 vide the cables with asystern ,of ?oats which will support
at a predetermined depth. Because the currents generally
the .dead weight of v"the cables. Such a system of j?oats
decrease with depth, it is desirable to have the pipe
maybe provided by ?oats 23 attached to points _21 and
forces which result in smaller anchors. It is also .de
sirable to have the pipe as high as possible to reduce the v25
necessary crushing strength of the pipe andpermit use‘
\Laying procedure would preferably be ,to start from
the terminal end and build toward the'source so that
of a thinner wall pipe. Thin wall pipe is ‘less expensive
each section -of pipe could be tested by compression on
the lay barge. ,In performing these tests the several
to minimize the length of the primary anchor lines. Thus,
check values .16 would provide test compartments as
a compromise depth must be selected. ,For instance, 30 they would close against new away from the terminal
in ‘the YucatanStraits which are some 6,500 ft. in .depth,
end of the pipe. '
a compromise pipe depth of 51,500 ft. ,may be selected.
,As each section .of pipe is laid, a pair of .lay barges
Current at this depth .is normally 1.12 miles per hour.
would drop each pair of anchors 18 and 19 at points
The tangent ‘of .the angle which the primiiiiy anchoring
spaced apart ‘by the approximate distances which these
line would assume is the buoyancy forces .of the ,pipe 35 anchors should assume with each other. However, it
line divided by the current forces .on the pipeline. Given
will be apparent that forces to ‘which the pipeline will
this angle and the height of .the pipeline, the length of
be subjected .and other factors, such as bottom condi
the primary anchoring line may be calculated with :sim
tions, dif?culty in positioning the vessels, etc., will re
ple trigonometry. For instance if we assume .a pipeline
sult in dragging of some of the anchors until all of the
having approximately 14 lbs. per ft. of buoyancy sub 40 primary anchors :18 .are c?ective :to hold the pipeline in
merged ,at 1,500 ft. in the Yucatan Straights, the tangent
position. 01? course as the anchors >18 drag, they will
of 1-14 diyided by current forces (which with ‘12 inch
move closer to anchors 19, and these anchors ‘will assist
in ‘holding the pipeline 10 in pos'iton. This condition is
pipe would result in 27.5 lbs. per it.) would be 27 ‘de
grees. 'By simple trigonometry the length of the primary
shown by :one of the anchoring systems of ,FIGURE ,3.
This is of particular advantage in the event of unusual
anchor line would be approximately 11,000 it.
conditions which might tend to drag one‘ or more of
A plurality of ‘primary anchor lines are vindicated at
anchors l8.
17 and extend between the ~pipeline .10 and a plurality of
anchors 1E8 positioned upstream from the pipeline. It
.Afterthe line has been laid, it should assume the-Posi
will be understood that the lines 17 and anchors 1.8 will
tion shown at A of FIGURE 2. ‘However, if the normal
hold the pipeline ‘10 submerged at approximately 1,500 ft. _ currents reduce, the line will ascend from the position .A
due :to't-heforceof the 1.12mile perhour current. If the
and upon a substantially no current condition existing,
the pipeline will move to position C. Upon the normal
current increases above ,this value, the pipeline would do
scend. Upon decrease in current, the pipeline will as
currents increasing, the pipeline will descend toward
cend. Preferably the system should be designed with
position B. Position B represents the depth to which
the maximum current conditions ‘in mind so :that the 55 the pipe will descend with maximum current conditions.
wall thickness of the pipe selected !will be .suthcient to
It ‘is of course apparent from FIGURE 2 that the pri
withstand the crushing pressure at the design depth for
mary anchoring cable 17 is controlling the ‘position of
maximum current.
the pipeline at positions A and .B, and that the sec
and gives higher buoyancy. ‘The high buoyancy is used
‘It :will be noted that ‘the length of'the anchor .line 17
is substantially greater than the depth of the water and,
ondary anchoring cable .20 is controlling the position of
60 thepipcline at Position (1‘.
therefore, under conditions ‘of no current ?ow .or sub
stantially no current ?ow, the pipeline could rise to the
surface where it would be .a menace to navigation.
The depths given ‘in FIGURE 2 are suggested for a
bodyof water 6.5.00ft. deep.
From the above it will be seen that the-objects of this
invention have been attained. There has been provided
establish an upper limit for the pipeline, .a secondary
anchoring system is provided. This system includes the 65 a system .of suspending pipe at an intermediate level in
deep water, and the pipe has been protected against com—
anchors 19 to which the secondary anchoring cables 20
at attached. These cables 20,:li-mit the upward rise of the
plete submergence even :in the case of leaks. As com
pipe to some preselected value, such as 3.00 ft. below
pared to .the pipe resting on bottom, a much thinner wall.
pipe-may he ‘used. It .will beappreciatedthat while in
the surface, ,as' bestshown in FIGURE 2. For this pur- , '
pose the effective length of the cable between the pipe 70 use, the pipe will always be under at least the pressure
line and anchors 19 should be approximately 300 ft.
exerted by 30.0 .ft. of water and, therefore, .a greater
less than the depth of the water.
In order to economize von cables, the cables are prefer
ably high-yield, tapered, galvanized cables so as to re
internal pressure can be tolerated ‘with a ‘given size ‘pipe
than would be possible at ‘the surface.
The pipeline illustrated .is designed to carry gas and,
duce both their weight and .ccst. Cables 17 and 20 75 therefore, the gas-?lled pipe provides the necessary
If the line is to transmit liquid, auxiliary
means would have to be provided to render the pipeline
negatively buoyant.
secondary cables to prevent this weight from being im
posed on the pipeline.
3. The pipeline of claim 1 wherein a plurality of
check valves are positioned at spaced intervals in said
The foregoing disclosure and description of the in
pipeline to permit testing of sections of pipe vas they
vention is illustrative and explanatory thereof and various
are ‘assembled ‘and to compartmentize the line in the
changes in the size, shape and materials, as well as in
event of a leak to prevent ?ooding of the entire pipeline.
the details of the illustrated construction, may be made
4. A pipeline suspended under water comprising, a
Within the scope of the appended claims Without depart
ing from the spirit of the invention.
plurality of sections of metallic pipe, a plurality of ?ex
What is claimed is:
10 ible connectors connecting the pipe sections into a con
tinuous pipeline, said pipeline being buoyant when con
1. A pipeline suspended under water comprising, a
taining gas, and means for ‘anchoring the pipeline in
plurality of sections of metallic pipe, a plurality of ?ex
position and maintaining the pipeline below a predeter
mined depth While permitting the pipeline to descend
tinuous pipeline, said pipeline being puoyant when con
taining gas, primary ‘anchoring means provided by a plu 15 between said depth and a second predetermined depth
upon an increase in speed of water currents including
rality of primary cables secured to the pipeline at spaced
primary and secondary cables and anchors, said primary
points and to -a plurality of primary anchors resting on
and secondary cables provided by separate cables com
bottom upstream of the pipeline, said primary cables
mencing at the respective anchors and extending to points
being of greater length than the Water depth, the length
of the primary cables and the degree of buoyancy of 20 of juncture and by common cables extending from the
points of juncture to the pipeline.
the pipeline being selected relative to the maximum cur
ible connectors connecting the pipe sections into a con
rent conditions expected to provide ‘a predetermined depth
beyond which the pipeline will not descend, and sec
ondary anchoring means provided by a plurality of sec
ondary cables secured to the pipe at spaced points and to 25
secondary anchors resting on bottom, said secondary
cables being of lesser length than the depth of the water
to limit ascending of the pipeline toxa predetermined
depth as the force of the current reduces.
2. The pipeline of claim 1 wherein means ‘are pro 30
vided for supporting the dead weight of both primary and
References Cited in the ?le of this patent
Schinke ______________ __ Nov. 29, 1892
Diescher _____________ __ Apr. 24, 1934
Great Britain _________ __ Aug. 21, 1866
Denmark ____________ __ Nov. 21, 1955
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