Railways – Tubular way – Internal service device
Reexamination Certificate
2002-02-13
2004-01-06
Morano, S. Joseph (Department: 3617)
Railways
Tubular way
Internal service device
Reexamination Certificate
active
06672222
ABSTRACT:
FIELD OF THE INVENTION
The invention comprises robotic equipment for carrying out operations in pipelines which can be applied to the activities of the production and transport of petroleum and its derivatives. More specifically, it relates to a vehicle capable of introducing tools, equipment or materials within pipelines, especially when long and installed under conditions of difficult access, for the purposes of removing obstructions, making inspections, repairs and other work. Although designed for use in the work of the production of petroleum and derivatives, the invention can be applied to any other industrial areas which make use of pipelines, or other confined spaces which may need work to be done within them, such as for example systems for the distribution of water, gas, basic drainage, hospital systems, air ducts, etc., energy generating plants, refineries, plants involving classified industrial processes (nuclear plants, etc.), plants for miscellaneous industrial processes, etc.
BASIS OF THE INVENTION
With the development of new technologies, the offshore production of petroleum is becoming viable at increasingly greater depths. This scenario involves the need to install an extensive system of pipelines at considerable depths. Together with other technological challenges which are being overcome, mainly those relating to the increasingly exacting specifications for equipment because of the high pressures, it is common for problems of various kinds which have not always been foreseen in advance to occur. Of these, mention may be made, for example, of problems brought about by low temperatures, which are normally associated with the properties of the fluid transported.
In the case of the problems arising as a result of low temperatures, there has been observed a tendency for reduction in the fluidity of oil, the formation of hydrates, the deposition of paraffin and, frequently, the occurrence of severe restrictions in flow or even blockages in pipelines. Clogging, which can also be caused by the deposition of sand or other materials, sometimes occurs at long distances from the nearest access points. In this way it is difficult or even impossible using the technology currently available to bring tools, equipment or other materials up to them. In work within pipelines, whether submarine or not, a prior survey of the conditions of the system is to be recommended, including at least:
survey of the layout of the pipelines to detect any differences between design and construction,
determination of the type of protection present in the pipeline (mechanical, chemical, cathodic, etc.),
investigation of the historical record of operational problems (occurrences), age of the installation, length and conditions of use, etc.,
an examination of routine inspection reports, among other technical documents.
One of the most important factors which has to be considered is the dimensional factor. Nominal diameter, bends, connections, branches, ovalization, dents, imperfections in the pipeline wall, etc., will interfere directly with the choice and performance of the system used to carry out work. Recently, much has been invested in the development of multidimensional pigs and techniques based on collapsing the pipelines, with a view to dealing with the dimensional aspects mentioned above which very often literally consist of accidents along the route. Some of these aspects, like bends and branches, may be known from the design and/or field surveys. It is common for pipelines to have sharp bends, and these significantly restrict the means available for work. At the present time the API standards accept a minimum radius of curvature of three times the nominal diameter for a particular gauge. Where the interruption in flow is total, the so-called hydraulic “wedge” is needed, which makes it impossible to use the main tool available for clearing long pipelines, which is a pig. Use of the latter equipment presupposes the existence of flow and a pressure difference within the pipeline. If a submarine pipeline breaks, the fluid tends to flow out into the external environment until a situation of pressure equilibrium is obtained. In this situation the pipeline has high operational instability as its main characteristic. Any attempt at action which involves a change in pressure will disrupt this precarious equilibrium and cause more spillage. The need to empty the pipeline, so that the causes of the accident can be investigated more closely and better known, must without fail go through a set of safety measures. At the present time, for fluid to be withdrawn from within the pipeline, it is necessary to use pumping, and this makes drainage unavoidable. As a protective measure temporary pipes are fitted and tested for leaks.
In both the situation where flow is totally obstructed and in the situation where pipelines are broken it is desirable that equipment should be developed which is capable of carrying some equipment inside the pipeline to the site of the problem without the need for a pressure difference. In the case of a broken pipeline, for example, the possibility of reaching the region of the failure from within the pipe with something which has yet to be developed which would make it possible to seal it and make use of the pumping pressure acting in a favourable direction, outwards from the interior, making the sealing means adhere even more, would constitute an innovative method for dealing with this type of problem. This accessory is already under development as one of the items which might carry out emergency repairs. This invention is designed to overcome problems such as those mentioned above, among others. It may act as a tool carrier, travelling within a pipeline, within specific diameter ranges, and having bends within the normal limits. It may also be used for surveying the profile of the internal surface of a pipeline, acting as a gauge. To sum up, the invention may be used for inspections and various types of work at points which are inaccessible for the means available at this time. Its movement within pipelines, in both directions, is based on the control of friction and on the use of non-reversing wheels mounted on towers capable of rotating about their vertical axis under remote control.
STATE OF THE ART
At the present time, equipment known as a pig is used for the work of removing encrustations in pipelines for the transport of petroleum. This comprises an object of round or oval shape, generally manufactured from some polymer, which moves along a length of the pipeline. While travelling, the pig scrapes off encrustations from the internal surface of the pipeline which partly obstruct it. The launcher is installed at the start point and the so-called pig-catcher is installed at the other end.
However, in order to move, the pig requires a pressure difference between the two ends of the length of the pipeline and the presence of a flow of fluid. When there is total obstruction of the pipeline there is no pressure difference, the fluid does not circulate, and a form of hydraulic plug is formed, and as a consequence pigs cannot be used. When there is a total blockage of flow a possible alternative to a pig is a flexitube. This is a flexible tube which has some strength and is provided with means for being passed inside the pipeline, which is used for various types of work. However, the scope of this equipment is limited. If the blockage point is at a distance, it may not even be possible to reach it. Although having considerable strength, the flexitube has limited capacity for application of the force which it requires in order to be pushed into the pipeline without suffering bending or excessive deformation. Mainly because of friction, there is a tendency for the flexitube to form a helicoid supported against the internal surface of the pipeline. As the flexitube moves forward, friction increases considerably, and more and more force is needed to push it into the pipeline. Formation of the helicoid and a consequent spring effect is thus accentuated. Beyond a certain point this
Nixon & Vanderhye PC
Olson Lars A.
Petroleo Brasileiro S.A.
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