Process for coating the internal surface of hydrothermosanitary

Details Process for coating the internal surface of hydrothermosanitary Process for coating the internal surface of hydrothermosanitary

1995-03-13

1997-09-02

Bell, Janyce

Coating processes

Interior of hollow article coating

Rotating the article

427235, 427238, 427239, 427348, 4273855, 4273881, B05D 722

Patent

active

056629648

DESCRIPTION:

BRIEF SUMMARY
The present invention deals with a process for coating the internal surface of hydrothermosanitary pipes, particularly made of aluminium, with resinous products, also of the atoxic type or "for foods", and with the related pipes obtained with such process.
In hydrothermosanitary plants, pipes play a role that cannot be neglected. Currently, pipes made of iron (zinc-coated pipes), of copper or resinous materials, etc. are used. Aluminium pipes, even though they cost much less, are not used, because they can be easily corroded from the chemical and electro-chemical (stray currents) points of view.
All metallic pipes can then be coated by limestone, depending on water hardness and temperature. Problems deriving from limestone, chemical corrosions and stray currents are solved for metallic pipes, but above all for aluminium pipes, by adopting the protection of the internal surface thereof, protection that can be achieved by the process claimed by the present invention.
After having carried out the pipe seal test (in coils or in rods), through pressurized air, in order to ascertain the absence of defects (due to pores or cracks), a resinous liquid is injected inside the pipe (generally kept at ambient temperature), said liquid having to wet all the internal surface thereof. In order to enable the whole internal pipe surface to be coated by the resinous liquid flowing inside it, the pipe (generally in coils) is placed and kept slowly oscillating or slowly rotating for all the length of the present operation and of the further operations.
Afterwards, air is blown into the pipe, and the liquid is made turbolent (facilitating wetting of possible areas that had not been coated by it) and the excess liquid is removed.
Then, a gauged head, equipped with adequate gaskets (shaped as a socket, like those used for pistons, or shaped as an O-ring, etc.), is inserted and, urged by compressed air, crosses the whole pipe "shaving" the internal surface (improving adherence of the resinous liquid on the internal pipe surfaces) and adjusting the resinous liquid thickness and finally exhausting the excess (of liquid) that should result from it.
Finally, the pipe (arranged in coils or in rods), still subjected to oscillation or rotation, is inserted into an oven and is subjected to hot air blow-in, to facilitate and speed up scavenging of (solvent) gases, that are removed from the resinous liquid fill that covers the internal pipe surface.
When the protective resinous fill has been strengthened, the operation comes to an end. A pipe is obtained with a smooth and continuos internal surface, having resistance properties to wear, chemical and electro-chemical corrosions and having atoxicity and anti-adherence properties to limestone that pertain to the adopted resinous product. Fixing of the fill to the pipe material is such that no disjunctions whatsoever occur, neither due to thermal stresses, nor due to mechanical stresses. The pipe therefore can, during installation, be shaped, bent, squashed without any problem and, during operation, can be subjected to normal thermal variations to which the plant is subjected.
The process with the related described sequences, that have been adopted for the pipe (generally made of aluminium) wound in coils, is also adopted for the rod-configured pipe by carrying out the adequate modifications required.
If the pipes in rods are horizontally arranged, the end rods are connected with tubular fittings (such as to create a seal to the blown-in air and the passing continuity for the shaving head), so that they are all arranged in series, and then the procedure adopted for pipes in coils is adopted.
That is, the resinous liquid is then injected.
Afterwards, pressurized air is blown-in and the liquid is made turbolent while the eccess one is removed.
The shaving head is inserted and this, urged by compressed air, crosses the whole pipe.
This operation improves liquid adherence to the internal surface, while the resinous liquid thickness is adjusted in adherence and the possible excess is exhausted. Ever

REFERENCES:
patent: 2707934 (1955-05-01), Curtis
patent: 4262627 (1981-04-01), Roeder et al.
patent: 4327132 (1982-04-01), Shinno
patent: 4454173 (1984-06-01), Koga
patent: 4454174 (1984-06-01), Koga
patent: 5326400 (1994-07-01), Sagawa
patent: 5499659 (1996-03-01), Naf

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