Plastic and nonmetallic article shaping or treating: processes – Removal of liquid component or carrier through porous mold... – By direct application of vacuum or pneumatic pressure
Patent
1992-07-20
1994-06-21
Aftergut, Karen
Plastic and nonmetallic article shaping or treating: processes
Removal of liquid component or carrier through porous mold...
By direct application of vacuum or pneumatic pressure
249 91, 249113, 249137, 249139, 264259, 264278, 264279, 264313, 425 63, 425 64, 425 85, 425125, 4251261, 425197, 425447, B28B 116, B28B 126, B28B 2106, B28B 2108
Patent
active
053226569
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of coating the outer surface of an elongated body, such as a rod or tube, with a layer of concrete.
BACKGROUND OF THE INVENTION
Submarine pipelines, for example for transporting petroleum or gas from offshore production fields may be made from steel pipe sections which are welded together on a special vessel, and the pipeline may be placed in position at the bottom of the sea as the pipe sections are being welded together. In order to secure that the pipeline remains in the desired position at the bottom at the sea, the pipe sections may be given a negative buoyancy by providing the outer peripheral surface of each pipe section with a layer of concrete. The pipe sections are preferably provided with the concrete coating before they are welded together on the vessel, and the opposite free end portions of the pipe section are exposed to facilitate the welding operation. The concrete layer should not only fulfill the usual conditions regarding strength and durability, but it could also be necessary to add heavy aggregates, such as iron ore in order to obtain a required high specific weight of the concrete.
Two different methods for providing pipe or tube sections with an outer layer of concrete are known, namely impingement and compression coating. Both of these methods in which the horizontally arranged tube is rotated and moved past a stationary coating machine, involves waste of concrete mixture and insufficient compression of the concrete. The insufficient compression of the concrete necessitates a relatively high content of heavy aggregates to obtain the necessary specific weight. Danish patent specification No. 155.460 discloses a method in which a horizontally extending tube is rotated slowly while concrete is applied to the full length of the tube, and the concrete is being shaped and vibrated by means of a mould surface provided with vibrators. This method has apparently not been used in practice. Danish patent application No. 644/84 discloses a sliding mould which may be used for applying ground-moist concrete to a steel pipe, which is positioned vertically.
SUMMARY OF THE INVENTION
The present invention provides a method of the above type which has been improved in various respects.
The present invention provides a method of coating the outer surface of an elongated body, such as a rod or tube, with a layer of concrete, said method comprising, arranging the elongated body in upright position, arranging an annular mould around the outer surface of the elongated body so as to define an annular space therebetween, feeding a concrete mixture to an upper funnel-like part of the mould, rotating the funnel-like part in relation to the remaining part of the mould so as to distribute the concrete mixture peripherally in said annular space, and moving the annular mould upwardly along the elongated body so as to form said layer of concrete on the outer surface thereof. Because of the rotating funnel-like part it is possible to obtain an even distribution of the concrete peripherally along the annular moulding space, even when the moisture content of the concrete is relatively low.
The invention also provides an apparatus for coating the outer surface of an elongated body, such as a rod or tube, with a layer of concrete, said apparatus comprising a frame structure, means for retaining the elongated body in an upright position within the frame structure, an annular mould for surrounding the upright elongated body so as to define an annular space between the elongated body and the annular mould, said mould comprising an upper funnel-like part which is rotatable about the axis of the annular mould relative to the remaining part of the mould, means for feeding a concrete mixture to said funnel-like mould part, means for rotating the funnel-like part in relation to the remaining part of the mould so as to distribute the concrete mixture peripherally in said annular space, and means for moving the annular mould axially along the upright elongate
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Aftergut Karen
Vibrodens A/S
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