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WO2006065043A1 - Coating method for cast iron pipe fitting joint and the coated castiron pipe joint by polyethyene - Google Patents

Coating method for cast iron pipe fitting joint and the coated castiron pipe joint by polyethyene Download PDF

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Publication number
WO2006065043A1
WO2006065043A1 PCT/KR2005/004241 KR2005004241W WO2006065043A1 WO 2006065043 A1 WO2006065043 A1 WO 2006065043A1 KR 2005004241 W KR2005004241 W KR 2005004241W WO 2006065043 A1 WO2006065043 A1 WO 2006065043A1
Authority
WO
WIPO (PCT)
Prior art keywords
pipe joint
cast
iron pipe
polyethylene resin
coating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/KR2005/004241
Other languages
French (fr)
Inventor
Jin-Man Park
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
KOREA WATER PIPE TECHNOLOGY Co Ltd
Original Assignee
KOREA WATER PIPE TECHNOLOGY Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by KOREA WATER PIPE TECHNOLOGY Co Ltd filed Critical KOREA WATER PIPE TECHNOLOGY Co Ltd
Publication of WO2006065043A1 publication Critical patent/WO2006065043A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
    • B05D3/0218—Pretreatment, e.g. heating the substrate
    • B05D3/0236—Pretreatment, e.g. heating the substrate with ovens
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/002—Processes for applying liquids or other fluent materials the substrate being rotated
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/18—Processes for applying liquids or other fluent materials performed by dipping
    • B05D1/22—Processes for applying liquids or other fluent materials performed by dipping using fluidised-bed technique
    • B05D1/24—Applying particulate materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
    • F16L58/02—Protection of pipes or pipe fittings against corrosion or incrustation by means of internal or external coatings
    • F16L58/04—Coatings characterised by the materials used
    • F16L58/10—Coatings characterised by the materials used by rubber or plastics
    • F16L58/1009—Coatings characterised by the materials used by rubber or plastics the coating being placed inside the pipe
    • F16L58/1045—Coatings characterised by the materials used by rubber or plastics the coating being placed inside the pipe the coating being an extruded or a fused layer
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L9/00—Rigid pipes
    • F16L9/14—Compound tubes, i.e. made of materials not wholly covered by any one of the preceding groups
    • F16L9/147—Compound tubes, i.e. made of materials not wholly covered by any one of the preceding groups comprising only layers of metal and plastics with or without reinforcement
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2254/00—Tubes

Definitions

  • the present invention relates to a pipe joint connecting pipes to form a pipeline such as a water supply pipeline and a sewerage pipeline, and more particularly to a cast-iron pipe joint coated with a polyethylene resin and a method for coating a synthetic resin on the inner and outer surfaces of a cast-iron pipe joint.
  • cast-iron pipelines are used in water supplies and sewerages. Pipe joints of various shapes are used to connect pipes, thereby forming such a pipeline.
  • L bends are used at a position where a pipeline is curved in L- shapes
  • T branches and Y branches are used at positions where pipelines have T-shapes and Y-shapes.
  • an increaser is used to connect pipes of different diameters, thereby forming a pipeline. In such a way, a large number of joints are used to form a pipeline, together with linear pipes.
  • Conventional cast-iron pipes and pipe joints are coated with coal tar by submerging the pipes and pipe joints in a coal tar tub, or are coated with paint (epoxy paint), to prevent generation of rust.
  • the coal tar is a by-product finally obtained after crude oil is refined, and is used generally to pave roads.
  • the coal tar is solid at a normal room temperature, but is melted into liquid phase if heated.
  • the coal tar is viscous, and so is easily adhered to form a film. Once adhered to something, the coal tar will not be separated before heated again. Further, the coal tar prevents generation of rust, which is generated as a metal such as iron is oxidized, by blocking air and water.
  • the coal tar is cheap and easily coated on a metal such as iron to form a coating film, but is removed by water over time. Therefore, the coal tar coating is not a perfect coating method.
  • coal tar is a final by-product of crude oil, it is harmful to human body. Further, since the coal tar coated on cast-iron pipes is gradually dissolved in water, people may drink the coal tar and thus the coal tar coating is not suitable for water supply pipelines. Furthermore, the coal tar and the epoxy paint is dissolved in water over time, and thus the dissolved harmful materials may be accumulated in creatures, thereby acting as an environment hormone deteriorating normal functions of endocrine systems of creatures.
  • cast-iron pipes in which linings of polyethylene are formed on the inner surfaces of the water supply and sewerage pipes, or an epoxy resin or a polyethylene resin is coated on the inner and outer surfaces thereof, have been developed and supplied.
  • the cast-iron pipes in which polyethylene linings are formed by inserting polyethylene pipe onto the inner surfaces thereof, or polyethylene coating layers are formed by adhering polyethylene resins, are durable to abrasion, chemicals, impacts, and the cold whether and increase mechanical strengths thereof with respect to exterior loads such as impacts.
  • the present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a cast-iron pipe joint which form a pipeline by connecting pipes, and in which the inner and outer surfaces thereof are coated with a polyethylene resin. Especially, the cast-iron pipe joint forms a perfect pipeline together with cast-iron pipes, the inner surface which is coated.
  • the pipeline employing the pipe joint according to the present invention can be applied to any pipeline such as a water supply pipeline and a sewerage pipeline. Especially, if the cast-iron pipe joint is applied to the sewerage pipeline, a cast-iron pipe joint which is not eroded by strong acid wastes contained in the sewage.
  • the cast-iron pipe joint which forms a pipeline such as a water supply pipeline and a sewerage pipeline by connecting pipes
  • a polyethylene resin the cast-iron pipe joint is not harmful to a human body and does not generate environmentally harmful materials (environmental hormones) such as coal tar and epoxy paint. Further, the coating process can be simply and cheaply performed. Furthermore, the coated polyethylene resin has so strong an adhering force that it cannot be easily abraded.
  • the polyethylene resin powder is adhered to the cast-iron pipe joint so as to have a uniform thickness, and the polyethylene resin in a coating tank is not solidified, the polyethylene resin can be saved.
  • the surfaces of the pipe joint are so contracted that the adhering force of the polyethylene resin is strong. Furthermore, the surfaces of the pipe joint are glossed and uniform.
  • FIG. 1 is a block diagram for describing a manufacturing process according to the present invention
  • FIG. 2 is a schematic cross-sectional view for showing a coating tank employed in the present invention
  • FIG. 3 is a schematic cross-sectional view for showing a heating furnace employed in the present invention.
  • FIG. 4 is a schematic cross-sectional view for showing another heating furnace employed in the present invention.
  • a method, according to the present invention, for coating a synthetic resin on the inner and outer surface of a cast-iron pipe joint 11 of L bends, T branches, Y branches, double Y branches, unequal single 90 0 Y branches, sanitary T branches, unequal sanitary T branches, a P-trap, an increaser, or the like, which is used in forming a pipeline by connecting pipes, with a synthetic resin comprises: a preprocessing process (A) for removing dusts, abrasives, and other foreign substances, which are attached to the surfaces of the pipe joint; a heating process (B) for heating the preprocessed pipe joint; a coating process (c) for melting a coating agent and attaching the coating agent on the heated pipe joint to form coating films; and a cooling process (D) for hardening and cooling the coating films attached to the pipe joint.
  • the heating process (B) comprises the steps of: introducing the cast-iron pipe joint
  • heating furnace 13 having a gas burner 14 including a plurality of heating nozzles on the inner side thereof; and heating the heating furnace 13 so that the temperature in the heating furnace 13 is within 330 to 350 degrees Celsius and the temperature of the introduced cast-iron pipe joint is within 300 to 320 degrees Celsius.
  • the coating process (C) comprises the steps of: introducing the cast-iron pipe joint
  • the polyethylene coating films which are adhered to the inner and outer surface of the heated cast-iron pipe joint 11, is hardened to finish the process.
  • the pipe joint 11 is rapidly cooled by submerging it in the water of a normal room temperature. If the cast-iron pipe joint of about 300 degrees Celsius is submerged in the water, the polyethylene films are rapidly cooled and are strongly adhered to the inner and outer surfaces of the cast-iron pipe joint 11, so that the inner and outer surfaces of the cast- iron pipe joint 11 are glossed.
  • the process is performed to clean the cast-iron pipe joint 11, which is to be coated, and thus to obtain coating surfaces of good quality.
  • rust generated on the surfaces of the cast-iron pipe joint 11 and casting sands left after the casting process are removed.
  • This process includes correction of the inner diameters of end portions of the pipe joint into which pipes are inserted.
  • the shot blast method in which sands of high pressure are jetted to the cast-iron pipe joint 11, can be used to remove rust, dusts, and other substances, which are attached to the surfaces of the cast-iron pipe joint 11, thereby cleaning the inner and outer surfaces of the cast-iron pipe joint 11.
  • the heating process (B) is performed to heat the cast-iron pipe joint 11, and to melt the polyethylene resin powder and then adhere the polyethylene resin powder to the power joint 11.
  • the cast-iron pipe joint 11 is introduced into the heating furnace 14, to which the gas burner 14 is mounted, so as to be heated.
  • the temperature in the heating furnace 13 is set to within 330 to 350 degrees Celsius, and the cast-iron pipe joint 11 is heated to the temperature of 300 to 320 degrees Celsius.
  • a means for conveying the cast-iron pipe joint is provided inside the heating furnace 13.
  • the cast-iron pipe joint 11, which is to be heated may be transferred in the heating furnace 13 through a belt conveyer, or a conveying ring 12 may be formed on the outer surface of the cast-iron pipe joint 11 and be hung on a hook.
  • the coating process (O) O
  • the cast-iron pipe joint 11 heated in the heating furnace 13 to the temperature of 300 to 320 degrees Celsius is introduced in the polyethylene resin powder 16 in order that the polyethylene resin powder can be adhered to the cast-iron pipe joint 11.
  • the blower 23 blows air from the lower side of the coating tank 21, in which the polyethylene resin powder 16 is filled, to the polyethylene resin powder 16 on the filtering net 22, in order to float the polyethylene resin powder 16 and lower the density of the polyethylene resin powder 16.
  • the cast-iron pipe joint 11 is introduced into the coating tank 21, and then is rotated so that the polyethylene resin powder 16 is uniformly adhered to the inner and outer surfaces of the cast-iron pipe joint.
  • the polyethylene resin powder 16 is uniformly adhered onto the rotated cast-iron pipe joint 11 by the centrifugal force, and the density of the polyethylene resin powder, which is floated by the air, lowers.
  • the thickness of the coated polyethylene resin film is preferably 0.5 to 1 mm, and can be arbitrarily regulated by controlling the time period for which the cast-iron pipe joint 11 is submerged in the coating tank 21.
  • the coating thickness of the cast-iron pipe joint 11 is determined according to the size and the heating temperature of the cast-iron pipe joint 11 and the fineness of the polyethylene resin, uniform coating thickness can be obtained by regulating the coating time period and the heating temperature.
  • the heated cast-iron pipe joint 11 is cooled by submerging the cast-iron pipe joint 11, which is withdrawn from the coating tank 21, in a tub containing water of a normal room temperature, the polyethylene coating films, which are attached to the inner and outer surfaces of the cast-iron pipe joint 11, is contracted so that the coating film can be strongly adhered to the surfaces of the pipe joint 11, and the surfaces of the pipe joint 11 are glossed.
  • the cast-iron pipe joint 11 is transferred using a nipper, for uniform transfer, in order to perform each process.
  • a conveying ring 12 can be attached to the surface of the cast-iron pipe joint 11 by welding, and can be hung on a hook to transfer the cast-iron pipe joint 11.
  • the conveying ring 12 can be formed when the cast-iron pipe joint 11 is manufactured. Therefore, the cast-iron pipe joint 11, which is coated according to the present invention, has the glossed polyethylene coating films on the inner and outer surfaces thereof. Further, the polyethylene coating films have a strong adhering force, and thus are not separated from the cast-iron pipe joint 11 by heat or impact. Furthermore, the cast-iron pipe joint prevents generation of rust, and is so strong against acid or alkali that scales and foreign substances cannot attach to the surfaces thereof and the shape thereof is not changed, even if it is used for a long period of time, thereby improving the durability thereof.
  • a fluoric resin is mixed with a polyethylene resin in the coating tank, a polyethylene coating film containing the fluoric resin can be simply obtained.
  • the pipe joint is glossed, is prevented from being rusted. Further, scales and foreign substances can be prevented from attaching to the inner surface of the pipe joint even after a long time use.

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Protection Of Pipes Against Damage, Friction, And Corrosion (AREA)

Abstract

Disclosed is a pipe joint for connecting pipes in order to form a pipeline such as a water supply pipeline and a sewerage pipeline, and more particularly to a cast-iron pipe joint in which the inner and outer surfaces thereof are coated with a polyethylene resin. The present invention relates to a cast-iron pipe joint such as L bends, T branches, Y branches, an increaser connecting pipes of different diameters, for connecting pipes in order to form a pipeline. The inner and outer surfaces of the cast-iron pipe joint are coated with a polyethylene resin through a preprocessing process, a heating process, a coating process, and a cooling process. In the coating process, air is blown through a filtering net from the lower side of a coating tank containing polyethylene resin powder, in order to float the polyethylene resin powder. The heated cast-iron pipe joint is introduced into the coating tank, and is rotated so that the polyethylene resin is adhered to the pipe joint. Thereafter, the pipe joint is cooled in cooling water to contract the coating film and gloss the surfaces of the pipe joint.

Description

[TITLE OF INVENTION]
COATING METHOD FOR CAST IRON PIPE FITTING JOINT AND THE COATED CASTIRON PIPE JOINT BY POLYETHYENE
[Technical Field]
The present invention relates to a pipe joint connecting pipes to form a pipeline such as a water supply pipeline and a sewerage pipeline, and more particularly to a cast-iron pipe joint coated with a polyethylene resin and a method for coating a synthetic resin on the inner and outer surfaces of a cast-iron pipe joint.
[Background Art]
In general, cast-iron pipelines are used in water supplies and sewerages. Pipe joints of various shapes are used to connect pipes, thereby forming such a pipeline.
In other words, L bends are used at a position where a pipeline is curved in L- shapes, and T branches and Y branches are used at positions where pipelines have T-shapes and Y-shapes. Further, an increaser is used to connect pipes of different diameters, thereby forming a pipeline. In such a way, a large number of joints are used to form a pipeline, together with linear pipes.
Conventional cast-iron pipes and pipe joints are coated with coal tar by submerging the pipes and pipe joints in a coal tar tub, or are coated with paint (epoxy paint), to prevent generation of rust.
The coal tar is a by-product finally obtained after crude oil is refined, and is used generally to pave roads. The coal tar is solid at a normal room temperature, but is melted into liquid phase if heated. The coal tar is viscous, and so is easily adhered to form a film. Once adhered to something, the coal tar will not be separated before heated again. Further, the coal tar prevents generation of rust, which is generated as a metal such as iron is oxidized, by blocking air and water. The coal tar is cheap and easily coated on a metal such as iron to form a coating film, but is removed by water over time. Therefore, the coal tar coating is not a perfect coating method.
Further, since the coal tar is a final by-product of crude oil, it is harmful to human body. Further, since the coal tar coated on cast-iron pipes is gradually dissolved in water, people may drink the coal tar and thus the coal tar coating is not suitable for water supply pipelines. Furthermore, the coal tar and the epoxy paint is dissolved in water over time, and thus the dissolved harmful materials may be accumulated in creatures, thereby acting as an environment hormone deteriorating normal functions of endocrine systems of creatures.
Considering that the epoxy paint and the coal tar used to prevent generation of rust are harmful to human bodies and are dissolved and removed after a predetermined period of time, with rust being generated on the inner surfaces of pipes, and scales are adhered to pipes, cast-iron pipes, in which linings of polyethylene are formed on the inner surfaces of the water supply and sewerage pipes, or an epoxy resin or a polyethylene resin is coated on the inner and outer surfaces thereof, have been developed and supplied. The cast-iron pipes, in which polyethylene linings are formed by inserting polyethylene pipe onto the inner surfaces thereof, or polyethylene coating layers are formed by adhering polyethylene resins, are durable to abrasion, chemicals, impacts, and the cold whether and increase mechanical strengths thereof with respect to exterior loads such as impacts.
[Disclosure of the Invention]
Therefore, the present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a cast-iron pipe joint which form a pipeline by connecting pipes, and in which the inner and outer surfaces thereof are coated with a polyethylene resin. Especially, the cast-iron pipe joint forms a perfect pipeline together with cast-iron pipes, the inner surface which is coated.
The pipeline employing the pipe joint according to the present invention can be applied to any pipeline such as a water supply pipeline and a sewerage pipeline. Especially, if the cast-iron pipe joint is applied to the sewerage pipeline, a cast-iron pipe joint which is not eroded by strong acid wastes contained in the sewage.
According to the present invention in which the inner and outer surfaces of a cast- iron pipe joint, which forms a pipeline such as a water supply pipeline and a sewerage pipeline by connecting pipes, are coated with a polyethylene resin, the cast-iron pipe joint is not harmful to a human body and does not generate environmentally harmful materials (environmental hormones) such as coal tar and epoxy paint. Further, the coating process can be simply and cheaply performed. Furthermore, the coated polyethylene resin has so strong an adhering force that it cannot be easily abraded.
Especially, since air is blown into polyethylene resin powder to float the polyethylene resin powder, and while the heated cast-iron pipe joint is rotating, the polyethylene resin powder is adhered to the cast-iron pipe joint so as to have a uniform thickness, and the polyethylene resin in a coating tank is not solidified, the polyethylene resin can be saved.
Further, when the polyethylene resin adhered to the inner and outer surfaces of the heated cast-iron pipe joint is rapidly cooled by cooling water, the surfaces of the pipe joint are so contracted that the adhering force of the polyethylene resin is strong. Furthermore, the surfaces of the pipe joint are glossed and uniform.
[Brief Description of the Drawings]
The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:
FIG. 1 is a block diagram for describing a manufacturing process according to the present invention;
FIG. 2 is a schematic cross-sectional view for showing a coating tank employed in the present invention; FIG. 3 is a schematic cross-sectional view for showing a heating furnace employed in the present invention; and
FIG. 4 is a schematic cross-sectional view for showing another heating furnace employed in the present invention.
[Best Mode for Carrying Out the Invention]
Reference will now be made in detail to the preferred embodiments of the present invention.
A method, according to the present invention, for coating a synthetic resin on the inner and outer surface of a cast-iron pipe joint 11 of L bends, T branches, Y branches, double Y branches, unequal single 900Y branches, sanitary T branches, unequal sanitary T branches, a P-trap, an increaser, or the like, which is used in forming a pipeline by connecting pipes, with a synthetic resin, comprises: a preprocessing process (A) for removing dusts, abrasives, and other foreign substances, which are attached to the surfaces of the pipe joint; a heating process (B) for heating the preprocessed pipe joint; a coating process (c) for melting a coating agent and attaching the coating agent on the heated pipe joint to form coating films; and a cooling process (D) for hardening and cooling the coating films attached to the pipe joint.
The heating process (B) comprises the steps of: introducing the cast-iron pipe joint
11 into a heating furnace 13 having a gas burner 14 including a plurality of heating nozzles on the inner side thereof; and heating the heating furnace 13 so that the temperature in the heating furnace 13 is within 330 to 350 degrees Celsius and the temperature of the introduced cast-iron pipe joint is within 300 to 320 degrees Celsius.
The coating process (C) comprises the steps of: introducing the cast-iron pipe joint
11 into a coating tank 21, in which polyethylene resin powder 16 is filled, in order to adhere the polyethylene resin powder 16 to the cast-iron pipe joint 11; distributing the polyethylene resin powder on a filtering net 22 in the coating tank 21, through which air can be passed but the polyethylene resin powder cannot be passed; blowing air to the polyethylene resin powder 16 from the lower side of the filtering net 22 using a blower 23 to float the polyethylene resin powder 16 using the blown air; and coating the inner and outer surface of the cast-iron pipe joint 11 with the floated polyethylene resin powder 16 while the cast-iron pipe joint 11 is rotating, so that the thickness of the coating films is 0.5 to 1 mm.
In the cooling process (D), the polyethylene coating films, which are adhered to the inner and outer surface of the heated cast-iron pipe joint 11, is hardened to finish the process. The pipe joint 11 is rapidly cooled by submerging it in the water of a normal room temperature. If the cast-iron pipe joint of about 300 degrees Celsius is submerged in the water, the polyethylene films are rapidly cooled and are strongly adhered to the inner and outer surfaces of the cast-iron pipe joint 11, so that the inner and outer surfaces of the cast- iron pipe joint 11 are glossed.
Hereinafter, the processes according to the present invention will be described in detail. The preprocessing process (A)
The process is performed to clean the cast-iron pipe joint 11, which is to be coated, and thus to obtain coating surfaces of good quality. In this process, rust generated on the surfaces of the cast-iron pipe joint 11 and casting sands left after the casting process are removed. This process includes correction of the inner diameters of end portions of the pipe joint into which pipes are inserted.
Further the shot blast method, in which sands of high pressure are jetted to the cast-iron pipe joint 11, can be used to remove rust, dusts, and other substances, which are attached to the surfaces of the cast-iron pipe joint 11, thereby cleaning the inner and outer surfaces of the cast-iron pipe joint 11. The heating process (B)
The heating process (B) is performed to heat the cast-iron pipe joint 11, and to melt the polyethylene resin powder and then adhere the polyethylene resin powder to the power joint 11. The cast-iron pipe joint 11 is introduced into the heating furnace 14, to which the gas burner 14 is mounted, so as to be heated. The temperature in the heating furnace 13 is set to within 330 to 350 degrees Celsius, and the cast-iron pipe joint 11 is heated to the temperature of 300 to 320 degrees Celsius.
It is preferable that a means for conveying the cast-iron pipe joint is provided inside the heating furnace 13. For example, the cast-iron pipe joint 11, which is to be heated, may be transferred in the heating furnace 13 through a belt conveyer, or a conveying ring 12 may be formed on the outer surface of the cast-iron pipe joint 11 and be hung on a hook. The coating process (O
The cast-iron pipe joint 11 heated in the heating furnace 13 to the temperature of 300 to 320 degrees Celsius is introduced in the polyethylene resin powder 16 in order that the polyethylene resin powder can be adhered to the cast-iron pipe joint 11. The blower 23 blows air from the lower side of the coating tank 21, in which the polyethylene resin powder 16 is filled, to the polyethylene resin powder 16 on the filtering net 22, in order to float the polyethylene resin powder 16 and lower the density of the polyethylene resin powder 16. Then, the cast-iron pipe joint 11 is introduced into the coating tank 21, and then is rotated so that the polyethylene resin powder 16 is uniformly adhered to the inner and outer surfaces of the cast-iron pipe joint. The polyethylene resin powder 16 is uniformly adhered onto the rotated cast-iron pipe joint 11 by the centrifugal force, and the density of the polyethylene resin powder, which is floated by the air, lowers.
The thickness of the coated polyethylene resin film is preferably 0.5 to 1 mm, and can be arbitrarily regulated by controlling the time period for which the cast-iron pipe joint 11 is submerged in the coating tank 21.
Although the coating thickness of the cast-iron pipe joint 11 is determined according to the size and the heating temperature of the cast-iron pipe joint 11 and the fineness of the polyethylene resin, uniform coating thickness can be obtained by regulating the coating time period and the heating temperature. The cooling process (D)
If the heated cast-iron pipe joint 11 is cooled by submerging the cast-iron pipe joint 11, which is withdrawn from the coating tank 21, in a tub containing water of a normal room temperature, the polyethylene coating films, which are attached to the inner and outer surfaces of the cast-iron pipe joint 11, is contracted so that the coating film can be strongly adhered to the surfaces of the pipe joint 11, and the surfaces of the pipe joint 11 are glossed.
Therefore, a polyethylene resin is coated on the surfaces of the cast-iron pipe joint through the above-mentioned processes.
In addition, In coating the cast-iron pipe joint 11 through the preprocessing process (A), the heating process (B), the coating process (C), and the cooling process (D), the cast-iron pipe joint 11 is transferred using a nipper, for uniform transfer, in order to perform each process. Further, a conveying ring 12 can be attached to the surface of the cast-iron pipe joint 11 by welding, and can be hung on a hook to transfer the cast-iron pipe joint 11.
The conveying ring 12 can be formed when the cast-iron pipe joint 11 is manufactured. Therefore, the cast-iron pipe joint 11, which is coated according to the present invention, has the glossed polyethylene coating films on the inner and outer surfaces thereof. Further, the polyethylene coating films have a strong adhering force, and thus are not separated from the cast-iron pipe joint 11 by heat or impact. Furthermore, the cast-iron pipe joint prevents generation of rust, and is so strong against acid or alkali that scales and foreign substances cannot attach to the surfaces thereof and the shape thereof is not changed, even if it is used for a long period of time, thereby improving the durability thereof.
In addition, if a fluoric resin is mixed with a polyethylene resin in the coating tank, a polyethylene coating film containing the fluoric resin can be simply obtained.
[Industrial Applicability]
If the inner and outer surfaces of a pipe joint used to connect pipes are coated with a polyethylene resin according to the present invention, the pipe joint is glossed, is prevented from being rusted. Further, scales and foreign substances can be prevented from attaching to the inner surface of the pipe joint even after a long time use.

Claims

[Claims]
1. A method for coating a synthetic resin on the inner and outer surface of a cast- iron pipe joint (11) which is one of L bends, T branches, Y branches, double Y branches, unequal single 900Y branches, sanitary T branches, unequal sanitary T branches, a P-trap, and an increaser, which are used in forming a pipeline by connecting pipes, with a synthetic resin, the method comprising: a preprocessing process (A) for removing dusts, abrasives, and other foreign substances, which are attached to the surfaces of the pipe joint; a heating process (B) for heating the preprocessed pipe joint; a coating process (c) for melting a coating agent and attaching the coating agent on the heated pipe joint to form coating films; and a cooling process (D) for hardening and cooling the coating films attached to the pipe joint, wherein the heating process (B) comprises the steps of: introducing the cast-iron pipe joint (11) into a heating furnace (13) having a gas burner (14) including a plurality of heating nozzles on the inner side thereof; and heating the heating furnace (13) so that the temperature in the heating furnace (13) is within 330 to 350 degrees Celsius and the temperature of the introduced cast-iron pipe joint is within 300 to 320 degrees Celsius, and wherein the coating process (C) comprises the steps of: introducing the cast-iron pipe joint (11) into a coating tank (21), in which polyethylene resin powder (16) is filled, in order to adhere the polyethylene resin powder (16) to the cast-iron pipe joint (11); distributing the polyethylene resin powder on a filtering net (22) in the coating tank (21), through which air can be passed but the polyethylene resin powder cannot be passed; blowing air to the polyethylene resin powder (16) from the lower side of the filtering net (22) using a blower (23) to float the polyethylene resin powder (16) using the blown air; and coating the inner and outer surface of the cast-iron pipe joint (11) with the floated polyethylene resin powder (16) while the cast-iron pipe joint (11) is rotating.
2. A method according to claim 1, wherein a conveying ring (12) is provided on the outer surface of the cast-iron pipe joint (11).
3. A cast-iron pipe joint, wherein a polyethylene resin is coated on the inner and outer surfaces thereof, by heating the cast- iron pipe joint (11) so as to form a pipeline by connecting pipes, by submerging the cast-iron pipe joint (11) into a coating tank, in which polyethylene resin powder is filled, in order that a polyethylene resin film having the thickness of 0.5 to 1 mm is coated on the inner and outer surface of the cast-iron pipe joint (11).
4. A cast-iron pipe joint according to claim 1, wherein a carrying ring (12) is provided on the outer surface of the cast-iron pipe joint (11).
PCT/KR2005/004241 2004-12-14 2005-12-12 Coating method for cast iron pipe fitting joint and the coated castiron pipe joint by polyethyene Ceased WO2006065043A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR10-2004-0105299 2004-12-14
KR1020040105299 2004-12-14

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WO2006065043A1 true WO2006065043A1 (en) 2006-06-22

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PCT/KR2005/004241 Ceased WO2006065043A1 (en) 2004-12-14 2005-12-12 Coating method for cast iron pipe fitting joint and the coated castiron pipe joint by polyethyene

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CN (1) CN1905956A (en)
WO (1) WO2006065043A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8038829B2 (en) 2006-02-22 2011-10-18 Shawcor Ltd. Coating method for pipe having weld bead

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104019294A (en) * 2014-05-29 2014-09-03 东营长城管业有限公司 Hot-dipping-plastic steel-plastic curve composite pipe production technology

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62234580A (en) * 1986-04-02 1987-10-14 Kubota Ltd How to paint the inner surface of metal pipes
KR100243904B1 (en) * 1997-11-10 2000-02-01 강의식 The resin coating method and installation of corrugated steel pipe
KR20030021536A (en) * 2001-09-06 2003-03-15 삼성전자주식회사 Management information synchronization method in a network communication system
KR100375772B1 (en) * 2000-02-10 2003-03-28 에니 파이프(주) The internal coating method of a iron and The iron pipe which is internal-coated by this method
KR20030039635A (en) * 2001-11-14 2003-05-22 주식회사 현대특수강 3-Layers Coating Method and Apparatus for Steel Pipe and Fittings by Powder Fusion

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62234580A (en) * 1986-04-02 1987-10-14 Kubota Ltd How to paint the inner surface of metal pipes
KR100243904B1 (en) * 1997-11-10 2000-02-01 강의식 The resin coating method and installation of corrugated steel pipe
KR100375772B1 (en) * 2000-02-10 2003-03-28 에니 파이프(주) The internal coating method of a iron and The iron pipe which is internal-coated by this method
KR20030021536A (en) * 2001-09-06 2003-03-15 삼성전자주식회사 Management information synchronization method in a network communication system
KR20030039635A (en) * 2001-11-14 2003-05-22 주식회사 현대특수강 3-Layers Coating Method and Apparatus for Steel Pipe and Fittings by Powder Fusion

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8038829B2 (en) 2006-02-22 2011-10-18 Shawcor Ltd. Coating method for pipe having weld bead

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