Brushing – scrubbing – and general cleaning – Implements – Pipe – tube – or conduit cleaner
Reexamination Certificate
1999-06-10
2001-10-30
Chin, Randall E. (Department: 1744)
Brushing, scrubbing, and general cleaning
Implements
Pipe, tube, or conduit cleaner
Reexamination Certificate
active
06308363
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 rate of fluid flow 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 the temperature of the petroleum which is flowing through the pipeline and which emerges at the well head at relatively high temperatures, and 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 for use in removing the material adhering to the inner walls of a pipeline, said device being moved inside the pipeline, in use, by means of the actual flow of the fluid flowing through the pipeline, characterized in that the device is of modular construction and comprises:
a plurality of groups of flexible radial scraping bars which are spaced apart and offset angularly so that the said bars are able to scrape substantially the entire inner surface of the said pipeline;
a flexible shaft onto which the said plurality of groups of flexible radial scraping bars is assembled; and
at least one flexible sealing module fitted on said flexible shaft of the modular multisize bidirectional scraping device.
That surface of each flexible sealing module which, in use, comes into direct contact with the inner walls of the pipeline may be coated with a layer of elastomeric material with high abrasion resistance, as a way of lengthening the service life of the sealing module.
It is also possible to open up channels in the outer surface of each flexible sealing module so that, when compressed, the flexible sealing module is better able to adapt its shape to the inner walls of a pipeline.
It is additionally possible to insert a longitudinal movement limiter inside each flexible sealing module in order to ensure it maintains a constant length, even when the modular multisize bidirectional scraping device is moving through a region of the inside of a pipeline where there is, for example, a reduction in diameter.
It is also possible to fit a plurality of further flexible radial scraping bars inside each flexible sealing module, to enhance the scraping effect.
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.
REFERENCES:
patent: 1516880 (1924-11-01), Bowman
patent: 2281918 (1942-05-01), Constant
patent: 5600863 (1997-02-01), Curran
patent: 6014789 (2000-01-01), Knapp
patent: 2448608 (1976-04-01), None
patent: 2801378 (1979-07-01), None
patent: 3818246 (1989-12-01), None
patent: 859032 (1961-01-01), None
patent: 981 649 (1965-01-01), None
patent: 1423132 (1976-01-01), None
Ferreira Lino Antonio Carlos
Nunes Enio Costa
Pereira Fernando Borja
Chin Randall E.
Nixon & Vanderhye PC
Petroleo Brasileiro S.A. - Petrobras
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