Pipes and tubular conduits – With closures and plugs – Test plugs
Reexamination Certificate
2001-09-27
2004-06-22
Hook, James (Department: 3752)
Pipes and tubular conduits
With closures and plugs
Test plugs
C138S093000, C138S098000
Reexamination Certificate
active
06752175
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is an auxiliary device for pipeline repairs for sealing a damaged position in the pipeline-wall of a circular-tubular-shaped pipeline against fluid which flows through the pipeline and comprising at least one sealing module with at least two radially expandable sealing collars positioned with a distance in-between, and connected through one base element. In the expanded state, the collars are pressed against the internal pipeline wall in a friction-contacting and pressure-tight manner whereby the base element consists of at least one bypass lead-pipe which is capable of containing the flow-through of the fluid in a direction axial to the pipeline and whose circumferential radius is smaller than the internal radius of the pipeline wall and smaller than the external radius of the expanded sealing collars in such a way that a working space sealed in a pressure-tight manner between the inner side of the pipeline wall and the outside area of the base element can be formed between the expanded sealing collars.
An auxiliary device for pipeline repairs of the type described in the introduction above, is know through “News from PSI” of the company PSI Plugging Specialists International A/S, Stavanger, Norway. This device may, for instance, be inserted into the affected pipeline section in an upstream location ahead of the damaged position and seal the pipeline across its entire cross-section.
By inflating the sealing collars with compressed air, the pressure of the sealing collars, in their external circumference, is brought to bear on the internal wall of the pipeline thus sealing the damaged position. Together with a further auxiliary device for pipeline repairs placed downstream to the damaged position, the damaged position can be isolated in such a way that only the pipeline section lying in-between the two devices can be drained from the outside, which in turn, enables the repair or replacement of the damaged pipeline wall.
However it is still of disadvantage that the pipeline cannot be used for conveyance throughout the repair works. Moreover, a safe sealing is only possible for lines that have been depressurized between two pumping stations, as unintended displacement may be triggered off in case of high pressure. Especially in the case of a conveyance of compressible media like natural gas in the pipeline, a considerable volume must be pressed into the line after the repair work, in order to restore the operating pressure of 40 to 100 bar (4 to 10 MPa) in the repaired section.
A type-conforming device in which an open, hollow-cylindrical body is installed into the longitudinal direction of the pipeline is known through the German Patent No. DE 43 15 927. The device serves the special purpose of sealing and repairing damaged underground pipelines. For the device, an arrestable pig fitted with hose lines and similar connections is equally applied in a similar manner pursuant to International Patent Publication No. WO 89/08217 in such a way that only a pull through the pipeline is enabled. A procedure with the aid of the flowing medium is not provided for. Therefore, in the course of counter-holding, the “pigs” are not washed away with the fluid-stream. The distance covered is limited by the length of the supply lines. At the end of work, the pigs must be pulled out of the pipeline and are therefore applicable only in pressureless lines.
A pipeline servicing device fitted with measurement sensors with which the pipeline wall can be inspected for damaged positions is known from the British Patent No. GB 2326 209. The pipeline servicing device comprises a by-pass lead pipe capable of conducting a fluid flow-through in the axial direction of the pipeline with its circumferential radius is smaller than the internal radius of the pipeline wall. The by-pass lead pipe is fitted with means for the regulation of the fluid-flow resistance of the auxiliary device for pipeline repairs in such a way that the auxiliary device can be displaced in the pipeline by the flowing fluid, and path control with which the flow-resistance can be reduced upon arrival at the damaged position is enabled in such a way that the pipeline servicing device is slowed at a pre-determined position. It is however impossible to perform repair works with the pipeline servicing device at the detected damage position as long as fluid is still flowing through the pipeline.
The principal object of the present invention, therefore, is to provide an auxiliary device for pipeline repairs with which the repair or replacement of a damaged position in a pipeline wall is possible, or the installation of a branch conduit can be realized, while the pipeline or “conveyance”, operation is maintained and no loss of natural gas, petroleum oil or other transported media is incurred.
SUMMARY OF THE INVENTION
This object, as well as ther objects which will become apparent from the discussion that follows, are achieved, according to the present invention, by providing a working space between the interior of a pipeline and the outer circumference of the base element when the auxiliary device for repairing a pipeline is pushed into a pipeline. The working space can be sealed in the axial direction of the pipeline and in a jointing manner by means of the expanding sealing collars. The auxiliary device is provided with a conveyance or transport module that is articulated to the sealing module. This device can then be transported through the fluid flow by means of the transport module.
The major difference with respect to the state of the art, in accordance with the last-mentioned references, is that, when the auxiliary device is run to a specific position of the pipeline, it stays there and offers the opportunities of repairing the damaged position of a pipeline as well as enabling the construction of a branch conduit. Therefore, there is no outward physical connection, rather only one wireless connection.
A major advantage of the present auxiliary device for pipeline repairs is that, by this means, an opening can be isolated in the pipeline wall through a working space, while the fluid which still continues to flow through the line. In other words, in the region between the sealing collars, the pipeline wall bears no load through internal pressure. For instance, the working space can also be rendered inert by having it filled up with nitrogen in such a way that it is safe to also work on the pipeline walls of natural gas pipelines while they are still in conveyance operation.
The pipeline wall can be filed through to the inside of the pipe and re-welded for the purpose of repairs. There too, boring can be performed for the creation of a branch conduit of the line. The conveyance operation can be maintained in the process; by-passing the repair position through other pipeline networks may become unnecessary.
Through the minimum of one by-pass lead-pipe, a large part of the flow-volume usually conveyed by the pipeline can be channeled through. Therefore, in the case of the present auxiliary device for pipeline repairs, according to the invention, the conveyance pressure may only be reduced as far as is required for keeping the clamping force of the sealing module on the pipeline wall constantly higher than the flow-resistance, which is based on the cross-section contraction exerted by one of the auxiliary devices for pipeline repairs in the stream-conducting pipeline.
Since according to the law of HAGEN-POISEUILLE, the flow-volume in a circular pipe increases with the fourth power of the pipe radius at a given pressure difference, it is of advantage for the cross section area of the by-pass lead-pipe to make up 60% to 90% of the cross section area of the pipeline. With this value, the throughput losses experienced in the course of a repair operation with the present auxiliary device for pipeline repairs are so minimal that an economic conveyance operation in the pipeline is maintained during repairs. As long as the auxiliary device for pipeline repairs generates only a minimum cross-section contraction
Willschuetz Hans-Georg
Willschuetz Klaus-Dieter
Hook James
Milde & Hoffberg LLP
Willschuetz Klaus-Dieter
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