CA1063530A - Pipeline with reinforcing means - Google Patents
Pipeline with reinforcing meansInfo
- Publication number
- CA1063530A CA1063530A CA255,232A CA255232A CA1063530A CA 1063530 A CA1063530 A CA 1063530A CA 255232 A CA255232 A CA 255232A CA 1063530 A CA1063530 A CA 1063530A
- Authority
- CA
- Canada
- Prior art keywords
- pipeline
- crack
- spring
- reinforcing means
- pipewall
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L57/00—Protection of pipes or objects of similar shape against external or internal damage or wear
- F16L57/02—Protection of pipes or objects of similar shape against external or internal damage or wear against cracking or buckling
Abstract
Abstract of the Disclosure Crack arresters for pipelines comprising a structure of ductile material of high tensile strength applied directly to the pipewall. The structure has the form of a spring, applied around the pipewall under prestress. The spring may have the shape of a helix or the shape of a spiral.
Description
~063530 The invention relates to a pipeline ~hich - at intervals along the pipeline - is provided with reinforcing means around the pipe-wall.
A pipeline o~ this type has already been proposed in United States patent application ~o. 3,768,269, in which the reinforcing means may comprise, for example, a cylindrical collar or a flat ring around the pipewall.
Such rigid collars and rings are intended to prevent propa-gation over a long distance of a lack of roundness - in the *orm of a buckle - developing locally in the pipeline. The ring or collar will resist such a change in shape of the pipewall and thus limit the damage to a shortlength of pipe. Buckles tend to develop in particular during laying of an empty pipeline on the seafloor.
The present invention indicates means of combating another possible form of trouble in pipelines. In particular pipelines with a large diameter in which a high internal pressure is pre-vailing, such as gas lines which are operated at pressures above 100 bar, have been found to burst open over a great distance when a local crack develops. The crack is then propagated linearly along the pipeline at great speed. The reinforcing means proposed in the said United States patent application often prove not to be effective in arresting such a crack. In pipelines on land such a crack may still come to a halt at the location of a section valve or a booster station, so that the damage is restricted to a part of the pipeline. Obviously, it is attractive to have crack arresters which limit the damage still further. For pipelines which have been laid, for example, on the seafloor, however, there is a tendency to restrict or even completely to eliminate the booster stations for the fluid to be transported and intermediate valves. It will be clear that in the latter case it is very attractive indeed to have effective crack arresters. An effective crack arrester has to meet the following requirements as far as possible:
a. When a crack arrives at a crack arrester a maximum amount j 35 of fracture energy should be absorbed by the crack arrester;
b. ~he stress occurring in the pipeline in front of the crack should be reduced as far as possible;
".: . , : : : . -c. Opening up of the crack should ~e prevented as far as possible; and d. The propagating crack should be deviated from its straight path by the crack arrester as far as possible.
Upon application of the single cylindrical collar or ring according to the said United States patent application it has been ~ound that in particular requirements b and d are not met: the crack propagates linearly under the reinforcing means and, owing to the abrupt transition in the pipeline to another wall thickness, stresses develop at the crack front which are larger than the stresses in a pipeline not having such reinforcing means.
In order to meet the above-mentioned requirements, it is known, for example from Canadian patent specification No. 678.571 and US patent specification No. 3,349,807, to use a reinforcing means or crack arrester having a shape which is to a certain extent non-uniform. More in particular US patent specification No. 3,349,807 discloses a reinforcing means or crack arrester which has the form of a wire, which is wound around a pipewall and is subsequently ; tightened onto said pipewall so as to load the wire to the required tension,whereafter the ends of the wire are interconnected.
It is an object of the invention to provide reinforcing means or crack arresters which can be mounted more easily on the pipeline ~ and is moreover more reliable than the above-mentioned known crack ; arrester. To this end, the invention relates to a pipeline which at intervals along the pipeline is provided with reinforcing means around the pipewall, wherein at least one of the reinforcing means comprises an elongated element of a ductile material of high tensile strength, which element is formed by a spring having in its released position an inner diameter which is smaller than the outer diameter of the pipeline.
For applying the spring around the pipewall the inner diameter of the spring is widened by tensioning the spring and slipping it over the pipeline, whereafter the spring is released with the effect that the spring clamps the pipeline firmly. The remaining tension in the spring causes the spring to fix itself to the pipeline. This means that the spring used as a crack arrester according to the invention is more reliable than a wire used as a crack arrester,
A pipeline o~ this type has already been proposed in United States patent application ~o. 3,768,269, in which the reinforcing means may comprise, for example, a cylindrical collar or a flat ring around the pipewall.
Such rigid collars and rings are intended to prevent propa-gation over a long distance of a lack of roundness - in the *orm of a buckle - developing locally in the pipeline. The ring or collar will resist such a change in shape of the pipewall and thus limit the damage to a shortlength of pipe. Buckles tend to develop in particular during laying of an empty pipeline on the seafloor.
The present invention indicates means of combating another possible form of trouble in pipelines. In particular pipelines with a large diameter in which a high internal pressure is pre-vailing, such as gas lines which are operated at pressures above 100 bar, have been found to burst open over a great distance when a local crack develops. The crack is then propagated linearly along the pipeline at great speed. The reinforcing means proposed in the said United States patent application often prove not to be effective in arresting such a crack. In pipelines on land such a crack may still come to a halt at the location of a section valve or a booster station, so that the damage is restricted to a part of the pipeline. Obviously, it is attractive to have crack arresters which limit the damage still further. For pipelines which have been laid, for example, on the seafloor, however, there is a tendency to restrict or even completely to eliminate the booster stations for the fluid to be transported and intermediate valves. It will be clear that in the latter case it is very attractive indeed to have effective crack arresters. An effective crack arrester has to meet the following requirements as far as possible:
a. When a crack arrives at a crack arrester a maximum amount j 35 of fracture energy should be absorbed by the crack arrester;
b. ~he stress occurring in the pipeline in front of the crack should be reduced as far as possible;
".: . , : : : . -c. Opening up of the crack should ~e prevented as far as possible; and d. The propagating crack should be deviated from its straight path by the crack arrester as far as possible.
Upon application of the single cylindrical collar or ring according to the said United States patent application it has been ~ound that in particular requirements b and d are not met: the crack propagates linearly under the reinforcing means and, owing to the abrupt transition in the pipeline to another wall thickness, stresses develop at the crack front which are larger than the stresses in a pipeline not having such reinforcing means.
In order to meet the above-mentioned requirements, it is known, for example from Canadian patent specification No. 678.571 and US patent specification No. 3,349,807, to use a reinforcing means or crack arrester having a shape which is to a certain extent non-uniform. More in particular US patent specification No. 3,349,807 discloses a reinforcing means or crack arrester which has the form of a wire, which is wound around a pipewall and is subsequently ; tightened onto said pipewall so as to load the wire to the required tension,whereafter the ends of the wire are interconnected.
It is an object of the invention to provide reinforcing means or crack arresters which can be mounted more easily on the pipeline ~ and is moreover more reliable than the above-mentioned known crack ; arrester. To this end, the invention relates to a pipeline which at intervals along the pipeline is provided with reinforcing means around the pipewall, wherein at least one of the reinforcing means comprises an elongated element of a ductile material of high tensile strength, which element is formed by a spring having in its released position an inner diameter which is smaller than the outer diameter of the pipeline.
For applying the spring around the pipewall the inner diameter of the spring is widened by tensioning the spring and slipping it over the pipeline, whereafter the spring is released with the effect that the spring clamps the pipeline firmly. The remaining tension in the spring causes the spring to fix itself to the pipeline. This means that the spring used as a crack arrester according to the invention is more reliable than a wire used as a crack arrester,
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: :
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wherein the interconn~cted ends ~or~ a weak link, ~hich mi~ht break.
Another advantage of e~ployi`ng spri`ngs, as ~ent~oned in the above, is that thin-walled materials of h~gh energy-absor~ing power can be used.
Accord~ng to a first embodiment of the invention, the rein-forcing means is a spring having the shape of a helix, whose turns do not touch each other when the spring is mounted on the pipeline.
Such a sprîng may have a relatively large material diameter and a large pitch, which may vary in the longitudinal direction. It has been found that such a spring is highly capable of causing a propa-gating crack to deviate from its straight path and of very gradually absorbing an increasing amount of energy as a crack arrives. On assembly the spring may be twisted or compressed against the spring force and may then easily be slipped over the pipeline. When the spring is then released it will grip the pipeline firmly.
According to a second embodiment of the invention, the rein-forcing means is a spring having the shape of a spiral. Upon as-sembly, the springs of spiral shape may be slipped over the pipe-line in a partially unwound form and then be released.
Both types of springs may be further reinforced or anchored by welding or clasping in position.
The invention may advantageously be applied, for example, to gas lines on the seafloor. In such gas lines, whose diameter may be, for example, 0.5 to 2.0 meters, and which may have a length of, for example, 100 km or more, usually a high pressure is applied.
Pressures of 150 bar and more may occur and, even at depths down to 200 m below sea level, are in no way balanced by the external pressure exerted on the pipeline by the water column present. These pipelines are usually provided with a concrete jacket to protect them and to make them heavier. Such a concrete jacket, however, even when reinforced, has been found ineffective in arresting a propagating crack. Cracks in such pipelines may develop, not only during laying, but, for example, also by soil slides or by ship's anchors and the like.
The dimensions and the locatîon of the crack arresters proposed will naturally have to be chosen ~rom case to case. Usually the total length of a reinforcing means according to the invention will
. . . . .
.. , : . . . . : , :'. ', . ' ' , . " . . ' ,, ~, . :
: :
~. :
,: .
~ :
wherein the interconn~cted ends ~or~ a weak link, ~hich mi~ht break.
Another advantage of e~ployi`ng spri`ngs, as ~ent~oned in the above, is that thin-walled materials of h~gh energy-absor~ing power can be used.
Accord~ng to a first embodiment of the invention, the rein-forcing means is a spring having the shape of a helix, whose turns do not touch each other when the spring is mounted on the pipeline.
Such a sprîng may have a relatively large material diameter and a large pitch, which may vary in the longitudinal direction. It has been found that such a spring is highly capable of causing a propa-gating crack to deviate from its straight path and of very gradually absorbing an increasing amount of energy as a crack arrives. On assembly the spring may be twisted or compressed against the spring force and may then easily be slipped over the pipeline. When the spring is then released it will grip the pipeline firmly.
According to a second embodiment of the invention, the rein-forcing means is a spring having the shape of a spiral. Upon as-sembly, the springs of spiral shape may be slipped over the pipe-line in a partially unwound form and then be released.
Both types of springs may be further reinforced or anchored by welding or clasping in position.
The invention may advantageously be applied, for example, to gas lines on the seafloor. In such gas lines, whose diameter may be, for example, 0.5 to 2.0 meters, and which may have a length of, for example, 100 km or more, usually a high pressure is applied.
Pressures of 150 bar and more may occur and, even at depths down to 200 m below sea level, are in no way balanced by the external pressure exerted on the pipeline by the water column present. These pipelines are usually provided with a concrete jacket to protect them and to make them heavier. Such a concrete jacket, however, even when reinforced, has been found ineffective in arresting a propagating crack. Cracks in such pipelines may develop, not only during laying, but, for example, also by soil slides or by ship's anchors and the like.
The dimensions and the locatîon of the crack arresters proposed will naturally have to be chosen ~rom case to case. Usually the total length of a reinforcing means according to the invention will
-3-- . ', , `:: ' , ' :: --` 1063530 not be greater than ten timeS the pipeline diameter and, for example, be approximately twice that diameter.
The smallest diameter of the reinforcing means, once they have been installed, is obviously equal to the outer diameter of the pipeline. The total thickness of the reinforcing means will be a fraction of the pipeline diameter, so that the largest diameter of the reinforcing means will usually not exceed 1.5 times the pipe-line diameter.
The mutual distance between the crack arresters according to i 10 the invention will depend on their efficient operation and also on the smallest length of pipeline that can be replaced when a crack has developed. Usually the distance between two neighbouring crack arresters will be more than ten times the pipeline diameter and for example be equal to 200 times that diameter.
Although other ductile materials of high tensile strength are also eligible, the pipewall and the reinforcing means according to the invention preferably consist of steel.
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~,, .,,,, - . . . - , , ,: . ~, . , : : ~ . .
. , : : , . -: : :
The smallest diameter of the reinforcing means, once they have been installed, is obviously equal to the outer diameter of the pipeline. The total thickness of the reinforcing means will be a fraction of the pipeline diameter, so that the largest diameter of the reinforcing means will usually not exceed 1.5 times the pipe-line diameter.
The mutual distance between the crack arresters according to i 10 the invention will depend on their efficient operation and also on the smallest length of pipeline that can be replaced when a crack has developed. Usually the distance between two neighbouring crack arresters will be more than ten times the pipeline diameter and for example be equal to 200 times that diameter.
Although other ductile materials of high tensile strength are also eligible, the pipewall and the reinforcing means according to the invention preferably consist of steel.
b~
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~,, .,,,, - . . . - , , ,: . ~, . , : : ~ . .
. , : : , . -: : :
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A pipeline which at intervals along the pipeline is provided with reinforcing means around the pipewall, wherein at least one of the reinforcing means comprises an elongated element of a ductile material of high tensile strength, which element is formed by a spring having in its released position an inner diameter which is smaller than the outer diameter of the pipeline.
2. Pipeline according to claim 1 wherein the spring has the shape of a helix, whose turns do not touch each other when mounted on the pipeline.
3. Pipeline according to claim 1 wherein the spring has the shape of a spiral.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7507290A NL7507290A (en) | 1975-06-19 | 1975-06-19 | Pipeline reinforcing elements - for preventing crack propagation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1063530A true CA1063530A (en) | 1979-10-02 |
Family
ID=19823981
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA255,232A Expired CA1063530A (en) | 1975-06-19 | 1976-06-18 | Pipeline with reinforcing means |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1063530A (en) |
| NL (1) | NL7507290A (en) |
-
1975
- 1975-06-19 NL NL7507290A patent/NL7507290A/en not_active Application Discontinuation
-
1976
- 1976-06-18 CA CA255,232A patent/CA1063530A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| NL7507290A (en) | 1975-10-31 |
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