Plastic and nonmetallic article shaping or treating: processes – Furnace lining formation or repair
Patent
1979-08-20
1984-04-10
Pavelko, Thomas P.
Plastic and nonmetallic article shaping or treating: processes
Furnace lining formation or repair
F27D 116
Patent
active
044420501
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to improvements in the method of applying monolithic refractory material by spraying. The method is adaptable for the construction and repair of industrial and metallurgical furnaces, and like refractory equipments.
BACKGROUND OF THE INVENTION
Conventionally, the method of spraying refractory material has been used only for lining the inside of small constructions such as chimneys and ducts. However, recently, the method has been used for the installation of industrial furnaces, in which the whole of the lining is formed by spraying monolithic refractory material.
The spraying of the material is generally conducted at room temperature, but in the course of recent repairing of industrial and metallurgical furnaces the tendency has been to spray refractory material while the furnace is still hot, as it is considered unfavorable and a loss of time to stop and cool the furnace for repairing merely a partly worn portion.
Spraying of monolithic refractory material has two kinds of processes, i.e. a dry process and a wet process. In the dry process, the powdered material is transmitted from the container to the nozzle by compressed air in a dry state through a hose, then mixed with water and sprayed. In the wet process, the powdered material is mixed with water in the container and sent to the nozzle in a muddy state, and sprayed by the compressed air.
In either process, however, the refractory material is sprayed through the nozzle which is spaced apart from an opposed work surface, and the material is forced to adhere to the surface by collision. As a result, some of the material may rebound or be carried away by the air stream, and such causes loss of the material. The loss becomes particularly large when material is applied to a vertical wall or a ceiling, and sometimes amounts to about 10% of the material used. Further, once the material is hydrated, it cannot be reused, so that, this kind of loss is considered to be a limitation to the development of the spray method.
The conventional spray method also has the following disadvantages.
(a) Rebounding material scatters around as dust, and injures the work environment.
(b) As the material is sprayed on the work surface layer by layer to form a lining, the lining easily peels off when it exceeds a certain thickness.
This limit of the thickness is about 100-120 mm. As a matter of fact, use of the spray method is restricted to merely repair of locally worn portions, because of this thickness limit.
SUMMARY OF THE INVENTION
In accordance with the method of the present invention, the work surface to be lined is surrounded with a screening member such as wire nettings, having openings which permit the air to escape but which openings are small enough to prevent the escape of the refractory material when it is sprayed. The screening member is disposed a distance away from the work surface to form a space therebetween, and the distance approximately corresponds to the required thickness of the lining to be formed. The refractory material is sprayed in the space through a nozzle disposed within the space and generally parallel, i.e., in a parallel or slightly inclined relationship, with the work surface.
While air in the sprayed mass escape through the openings of the screening member, refractory material may be seized therein and piled up in the space to form a lining. Particles of sprayed material coagulate with each other and adhere to the work surface while the stickiness of the material is still retained.
According to the method of the present invention, not only the material loss as mentioned above may be minimized, but the work environment may be substantially improved because of the decrease of scattering of material. Further, it enables increase of the thickness of the lining, because the peeling of the lining is prevented as will be mentioned below in the detailed descriptions.
BRIEF DESCRIPTION OF THE DRAWING
The drawing is a perspective view of a portion of a refractory construction, illustrating the p
REFERENCES:
patent: 3672649 (1972-06-01), Allen
patent: 4039175 (1977-08-01), Beckers
Adams Bruce L.
Burns Robert E.
Lobato Emmanuel J.
Nippon Crucible Co., Ltd.
Pavelko Thomas P.
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