JPH0642694A - Method of peeling off cover from adhesive type polyethylene covered steel pipe - Google Patents

Abstract

PURPOSE:To peel off a polyethylene cover from a steel pipe with no resin remaining on the outer surface of the steel pipe. CONSTITUTION:A heater is made close contact with the inner surface of a steel pipe 1 which is bonded at its outer surface with a polyethylene cover by means of an epoxy resin adhesive so as to heat the steel pipe 2 in order to raise the temperature of the outer surface thereof up to a temperature of about 85 to 115 deg.C, thereby the polyethylene cover is peeled off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stripping a steel pipe having a polyethylene coating adhered thereto.

[0002]

2. Description of the Related Art Conventionally, there is known a steel pipe in which a polyethylene coating is adhered to the outer surface of the steel pipe with an adhesive agent of epoxy resin to form an anticorrosion layer. Then, for the piping of the polyethylene-coated steel pipe, cutting and welding work of the steel pipe is performed with various pipe lengths in design.

To cut or weld the steel pipe, the polyethylene coating is peeled off from the outer surface of the steel pipe at the portion to be cut or welded. Further, the peeling of the polyethylene coating from the steel pipe is performed as follows. That is, after heating the steel pipe and the polyethylene coating with a gas burner from the inside and outside of the portion where the polyethylene coating of the steel pipe is to be peeled off, two circumferential notches are formed at intervals in the heated polyethylene coating, and Make a cut in the direction of the tube axis between the cuts.

Then, the heated polyethylene coating is peeled off from the portion where a cut is made in the pipe axial direction.

[0005]

The means for heating the steel pipe from the outer surface with a gas burner is such that the polyethylene coating burns due to heating to generate smoke and the working environment is poor. Since it was in a narrow pipe, the working environment was also bad.

When the polyethylene coating was peeled off, the resin remained on the outer surface of the steel pipe. Therefore, after the polyethylene coating was peeled off, the resin remaining on the outer surface of the steel pipe had to be removed by a disc sander or the like, and dust was generated, the working environment deteriorated, and it took time.

The present invention has been made in view of the above matters, and when the polyethylene coating is peeled off, the resin is not left on the outer surface of the steel pipe so that the polyethylene coating can be peeled off in a short time in a good working environment. This is a technical issue.

[0008]

According to the present invention, a heater 10 containing a heating wire 13 is mounted in close contact with the inner surface of a steel pipe 1 to which a polyethylene coating 2 is adhered with an epoxy resin adhesive on the outer surface. The heater 10 heats the steel pipe 1 so that the outer surface of the steel pipe 1 is in the range of approximately 85 ° C. to approximately 115 ° C., and the polyethylene coating 2 is peeled from the outer surface of the steel pipe 1. The coating peeling method was used.

[0009]

According to the present invention, the heater 10 having the heating wire 13 therein is closely attached to the inner surface of the steel pipe 1 to which the polyethylene coating 2 is adhered by the epoxy resin adhesive on the outer surface. The outer surface of the steel pipe 1 is approximately 85 ° C.
It heats so that it may become in the range of about 115 degreeC.

Then, it was found that the adhesive of the epoxy resin did not dissolve, but the adhesive strength was significantly reduced.
The adhesive force of the adhesive is stronger with respect to the polyethylene coating 2 than with the outer surface of the steel pipe 1.

Therefore, when a cut or the like is made in the polyethylene coating 2 heated as described above and pulled from the end, the epoxy resin adhesive is peeled off from the outer surface of the steel pipe 1 while being adhered to the polyethylene coating 2. , Does not remain attached to the outer surface of the steel pipe 1.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. 1 to 4 are views for explaining one embodiment of the present invention.

In the steel pipe 1 of this embodiment, a polyethylene coating 2 is adhered and fixed to the outer surface of the steel pipe 1 having a diameter of 600 mm by an epoxy resin adhesive. The heater 10 mounted on the inner surface of the steel pipe 1 has a thickness of 0.5 mm and a width of 235 m.
A heating plate 11 made of stainless steel and having a length of 1870 mm and a length of 0.8 mm is provided on the upper surface of the heating plate 11.
The two silicon rubber sheets 12 having a width of 225 mm and a length of 1840 mm are stacked and adhered to each other, and the heating wire 13 is provided between the two silicon rubber sheets 12.

A lead wire 14 is connected to the heating wire 13 of the heater 10, the connecting portion of the lead wire 14 is covered with a connecting portion fixing cover 15, and the upper surface of the silicone rubber sheet 12 is covered. Is provided with a temperature sensor 17, and the lead wire 14 is connected to the lead wire fixing cover 1
It is fixed to the upper surface of the silicone rubber sheet 12 by 5.

In this embodiment, the heater 10 is formed by bending an annular shape on the inner surface of the portion of the steel pipe 1 where the polyethylene coating 2 is to be peeled off.
The heating plate 11 of the heater 10 is brought into contact with the inner surface of the steel pipe 1 so as to be in close contact therewith.

Then, both ends of the heater 10 were fixed to the inner surface of the steel pipe 1 by pressure contact with the electromagnets 22. The heater 10 may be fixed by mounting a turnbuckle between the ends of the heating plate 11 of the heater 10.

Next, the heater 10 was energized to heat the steel pipe 1. Then, in this example, in order to more accurately know the temperature of the polyethylene coating 2, a temperature marker (not shown) was attached to the surface of the polyethylene coating 2 to be heated.

When the temperature marker reaches 60 ° C., two circumferential cuts 3 are made in the heated polyethylene coating 2 (FIG. 1) and two circumferential cuts 3 are made.
A slit 4 was made in the tube axial direction (Fig. 2). And
The end of the polyethylene coating 2 at the portion where the cut 4 in the tube axial direction was made was peeled off by about 50 mm.

Further, the temperature of the outer surface of the steel pipe 1 at the portion where the polyethylene coating 2 is peeled off is measured, and when the temperature of the outer surface of the steel pipe 1 reaches 95 ° C., as shown in FIGS. The polyethylene coating 2 was sandwiched between the rollers 26, and the peeling roller 26 was rotated to peel off the polyethylene coating 2.

The time required to peel off the polyethylene coating 2 by the peeling roller 26 is less than 5 minutes, and neither the epoxy resin nor the polyethylene coating 2 remains on the outer surface of the steel pipe 1 from which the polyethylene coating 2 has been peeled off. It peeled off cleanly.

In the comparative example in which the temperature of the outer surface of the steel pipe 1 was 120 ° C., the steel pipe 1 from which the polyethylene coating 2 was peeled off
The epoxy resin remained on the outer surface of the. Furthermore, in the comparative example in which the temperature of the outer surface of the steel pipe 1 was 125 ° C., a large amount of epoxy resin remained on the outer surface of the steel pipe 1 from which the polyethylene coating 2 was peeled off.

[0022]

INDUSTRIAL APPLICABILITY The present invention has a polyethylene coating 2 on the outer surface.
Is closely attached to the inner surface of the steel pipe 1 adhered with an epoxy resin adhesive, and the heater 10 having the heating wire 13 therein is attached to the inner surface of the steel pipe 1. This is a method in which the polyethylene coating 2 is peeled from the outer surface of the steel pipe 1 by heating so as to be in the range of about 115 ° C.

When the temperature is within the above range, the epoxy resin adhesive is not dissolved, but the adhesive strength is significantly reduced. The adhesive force of the adhesive is stronger with respect to the polyethylene coating 2 than with the outer surface of the steel pipe 1.

Therefore, the heated polyethylene coating 2
When a notch is made and the end is pulled, the epoxy resin is peeled off together with the polyethylene coating 2 and the steel pipe 1
Therefore, the work of removing the polyethylene coating 2 can be carried out hygienically in a short time without remaining on the outer surface.

[Brief description of drawings]

FIG. 1 is a side view showing a state where a coating is peeled off according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a state where the coating is peeled off according to an embodiment of the present invention.

FIG. 3 is a plan view of a heater used in an embodiment of the present invention.

FIG. 4 is a cross-sectional view taken along the line AA of the heater shown in FIG.

[Explanation of symbols]

 1 Steel pipe 2 Polyethylene coating 10 Heater 13 Heating wire

Claims (1)

[Claims] 1. A heating wire 1 is provided on an inner surface of a steel pipe 1 having a polyethylene coating 2 adhered to the outer surface by an epoxy resin adhesive.
A heater 10 containing 3 is closely attached and the heater 10 is mounted on the steel pipe 1 so that the outer surface of the steel pipe 1 is approximately 85 ° C to approximately 1 ° C.
A coating stripping method for an adhesive-type polyethylene-coated steel pipe in which the polyethylene coating 2 is stripped from the outer surface of the steel pipe 1 by heating so as to be in the range of 15 ° C.