Pipes and tubular conduits – Repairing
Patent
1999-02-04
2000-02-29
Brinson, Patrick
Pipes and tubular conduits
Repairing
138 99, 138145, C10G 3506
Patent
active
060297107
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a process for repairing plastic coating of metal pipes which allows one to obtain said repair using only a flame as the heat source for heating the area to be repaired.
Plastic coated metal pipes, usually made of steel, are widely employed for pipelines used for the transport, even at great distances, of fluid materials such as oil, natural gas, or water.
Said pipelines must be able to withstand the most varied environmental conditions, and, in certain cases, the high temperatures that are maintained, for example, in the proximity of pumping stations, or which may be typical of certain liquids extracted from the subsoil.
Therefore, so as not to create weak points along the pipeline, it is necessary that the damaged or removed parts of the plastic coating (for instance at the welding points of the pipes) be repaired in such a way as to obtain mechanical properties as homogeneous as possible with the original coating.
As an answer to such needs, materials and methodologies aimed at reaching said objective with satisfactory results are known in the art.
However, when the size of the damaged part is considerable (for example when the coating has been removed in order to weld the pipes), it is necessary to use complicated repairing techniques which require long periods of time and sophisticated and costly equipment, such as induction ovens. Italian patent application n. MI 96/A 001737 describes a repairing process particularly quick and effective, which limits the use of sophisticated and costly heating equipment, such as induction ovens, to the heating phase that precedes the application of the primer, and allows one to carry out the other heating phases with an inert gas shielded flame (where the gas is nitrogen for example), thus reducing or eliminating the contact between the air and the heated area.
BRIEF SUMMARY OF THE INVENTION
It has now been perfected a repairing process that allows the use of a flame alone as the heat source for the area being repaired. Moreover, according to the process of the present invention, the flame used can be an open flame, i.e., without any shielding aimed at reducing or eliminating the contact between the air and the heated area.
Therefore, the process of the present invention is considerably more simplified with respect to the processes previously used in the art, since it allows to eliminate the use of induction ovens and shielded flame, requiring only the use of open-flame equipment, such as a common gas torch.
Therefore, object of the present invention is a process for repairing plastic coatings of metal pipes (in particular polyolefin, preferably polypropylene and/or polyethylene coating) comprising the following operating phases: perimeter surrounding the exposed metal part to be coated, said shield comprising one or more components having two spacing elements that are protruding and opposite to each other and located on the periphery of the inside surface of the shield, where one of said elements is put in contact with the coating, and the other with the exposed metal part to be coated, leaving the edges of the coating on the inside of the space that is formed between the shield and the pipe; metal part previously heated with a flame; from 170.degree. C. to 250.degree. C., preferably from 190 to 230.degree. C.; mixture of epoxy primer with an adhesive polyolefin material; material and a superimposed layer of a coating made of polyolefin material; material is applied during phase 4), the application of a layer of adhesive polyolefin material in phase 6) can be omitted.
Obviously, when the application of a layer of adhesive in phase 6) is omitted, the coating layer is directly applied on the mixture of epoxy primer and polyolefin adhesive material applied in phase 4).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The term "exposed metal part" means that said metal part is not yet coated with a coating (as opposed to adhesive) layer of polyolefin material. Thanks to the application of the protective s
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Marzola Roberto
Rigosi Gian Luigi
Brinson Patrick
Montell North America Inc.
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