Brushing – scrubbing – and general cleaning – Implements – Pipe – tube – or conduit cleaner
Reexamination Certificate
1999-05-18
2001-08-21
Warden, Sr., Robert J. (Department: 1744)
Brushing, scrubbing, and general cleaning
Implements
Pipe, tube, or conduit cleaner
C015S104160, C015S104200, C015S104063
Reexamination Certificate
active
06276017
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for scraping the inner walls of a pipeline. More particularly, the present invention relates to a device for removing material adhering to the inner walls of a pipeline conveying a flow of petroleum.
PRIOR ART
During operation of a fluid-flow system using pipelines, material originating from the flow may adhere to the inner walls of the pipeline, which causes the area of the cross section of the pipeline to be reduced and this adversely affects the flow of fluid and, consequently, reduces the flow rate of the fluid passing through the pipeline.
The rate of deposition of material on the inner walls of a pipeline will depend on a number of factors: for example the composition of the fluid, the volume flow rate, the temperature of the fluid, the geometry of the pipeline, etc. In the case of pipelines used for the flow of the petroleum production of offshore production wells, in which the petroleum has for example a high paraffin content, situations arise in which the rate of deposition is very high.
When the production wells are located in deep waters, around 1000 m or more, the thermal differential between (i) the temperature of the petroleum which is flowing through the pipeline and which emerges at the well head at relatively high temperatures, and (ii) the temperature of the seawater, which is generally fairly low, accelerates the process of deposition of organic material on the inner walls of the pipeline. This may be exacerbated by the fact that the pipeline usually crosses relatively long distances along the seabed, up to a point where either it is connected to a manifold or it rises in order to be connected to a surface collection point.
To maintain the flow capacity of the pipeline in accordance with its original characteristics, use is regularly made of a scraping device which is passed through inside the pipeline and driven along by the actual flow. As this scraper passes through the inside of the pipeline, it removes the layers of organic material adhering to the inner walls of the pipeline, thereby maintaining the pipeline in good condition for the petroleum production to flow through.
When the internal diameter of the pipelines through which a scraping device passes is constant, there will normally be no problems concerning scraper performance when a complete scraping cycle is carried out. However, when operation involves flow systems which comprise pipelines of different diameters, which is a very common occurrence in offshore petroleum flow systems, the need arises for use to be made of scraping devices which are capable of passing through all the pipelines without a loss in scraping efficiency.
In such situations, use is made of a multisize scraping device capable of passing through sections of pipeline with different internal diameters. Scraping devices are available which are capable of passing through different sections of pipeline in which the largest diameter is approximately double the smallest diameter, and in such situations there is a significant loss of scraping efficiency.
However, situations may arise in which the scraping device becomes stuck in a certain section of pipeline, for example owing to the excessive accumulation of material. In such a situation, the most immediate possibility of recovering the scraping device consists of reversing the flow of fluid so that the scraping device is then conveyed, by the flow of fluid, in the opposite direction from its original direction of movement so that it is possible for it to be recovered at the point from where it was originally launched.
The multisize scraping devices known in the prior art do not have the characteristic of being bidirectional. There are reports of situations in which the prior art scraping devices do succeed in operating as if they were bidirectional, but results are unreliable. There is therefore a need for a multisize scraping device which is genuinely bidirectional.
As will be seen in the following description, the present invention relates to a multisize scraping device which has the characteristic of being bidirectional.
SUMMARY OF THE INVENTION
The present invention relates to a multisize bidirectional scraping device which comprises a flexible shaft of flexible elastomeric material; a plurality of groups of flexible radial scraping bars of flexible elastomeric material, spaced along the flexible shaft and offset angularly; and a flexible covering which covers the entire assembly formed by the flexible shaft and by the plurality of groups of flexible, radial scraping bars, with the exception of the outer ends of the radial scraping bars.
Use may be made, at the ends of the flexible shaft, of a guide disc of flexible elastomeric material, the function of which is basically to improve the centering of the multisize bidirectional scraping device when it passes through a transition from the largest diameter to the smallest diameter of a pipeline.
The outer surface of the flexible covering may also be coated with a layer of elastomeric material with high abrasion resistance, as a way in which to lengthen the service life of the coating.
The flexible radial scraping bars may be stiffened by means of the use, inside them, of metallic materials which have a “shape-memory” characteristic, in order to enhance the scraping effect of the scraping bars.
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Ferreira Lino Antonio Carlos
Mosqueira Gomes Marcelino Guedes Ferreira
Pereira Fernando Borja
Nixon & Vanderhye PC
Petroleo Brasileiro S.A. - Petrobras
Snider Theresa T.
Warden, Sr. Robert J.
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