JPH066336B2 - Bending correction method for plastic pipe - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for straightening a curling behavior of a long thermoplastic plastic pipe wound in a coil shape.

[Conventional technology]

For example, polyethylene pipes are used for gas piping. The long pipe is stored and transported in the form of a coil wound in order to facilitate the handling of the load, and is straightened and used at the piping site. In this case, if the pipe is simply unwound, a considerable amount of curl remains, so it is necessary to correct the curl.

[Problems to be solved by the invention]

Conventionally, the coiled tube is rolled out manually and the curl is manually corrected. In this case, it is necessary to largely bend back in the direction opposite to the winding direction, a large tensile stress acts on the outside of the pipe, and a large compressive stress acts on the inside of the pipe.
May cause plastic deformation such as flat pipes and wrinkles.

This invention, without adversely affecting the quality of the pipe,
It is an object of the present invention to provide a bending correction method capable of correcting the bending efficiently.

[Means and Actions for Solving Problems] Using a caliber roll by a bend straightening machine composed of rolls arranged so as to be able to reverse bend the bend of a coiled long thermoplastic pipe Then, a strong bend is first corrected, and then a weak bend is sequentially corrected to correct the bend.

Thereby, the bend is efficiently corrected without adversely affecting the pipe.

〔Example〕

An example of an apparatus for carrying out the method of the present invention will be described with reference to the drawings. In the figure, reference numeral 1 is a hot-air circulation type heating tank for heating a coiled pipe 2. The coiled pipe 2 is supported by a drum 3, and the pipe P is guided by a guide roll 4 and fed out. ing. Reference numeral 5 is a hot-air circulation type heat-retaining tank, in which a three-roll type straightening machine is provided in multiple stages. In this example, the rolls 61 to 67 are arranged in a zigzag pattern in the vertical direction so that the swing width of the rolls gradually decreases, and the pipe is first subjected to repeated bending that is strong and then gradually weakens. The front and rear rolls 61 and 67 are fixed-position drive rolls, and the intermediate rolls 62 to 66 are idle rolls, which are provided so that their positions can be adjusted in the vertical direction so that the bending radius can be adjusted. Reference numeral 8 is a water cooling type cooling tank for cooling the straightened pipe, and guide rolls 9 are provided at the front and rear. Reference numeral 10 is a feeding machine in which driving endless belts are arranged to face each other.

Various tests were conducted using the above apparatus.

Materials used Coiled pipe made of medium density polyethylene Melting point = 120 ° C, glass transition point = -120 ° C Pipe size outer diameter = 34.0mm Wall thickness = 3.7mm Pipe length 10m Coil outer diameter 1.4m Test 1 Roll at 20 ° C pipe temperature Shape is 300mm in width and 150 in diameter
It was carried out using a cylindrical roll of mm.

A first reverse bend radius, in the range from 1/2 of the coiled radius twice, then the second sequential large bending radius, the third reverse bending was performed the results, the curvature after straightening 0.85m 0.15 ^{- It was 1} , and the target curvature of 0.02 m ^-1 was not obtained. When the bending radius is 0.5R, the straightened pipe becomes flat, and the pipe flatness (pipe minimum diameter / pipe maximum diameter) is 0.89.
Became.

Conclusion: When using a cylindrical roll, the pipe becomes flat and not suitable for practical use.

Test 2 In the same way, at a pipe temperature of 20 ℃, roll shape 300mm
It was carried out using a V-groove roll having a diameter of 150 mm and an angle of 120 °.

Curvature after correction is 0.09 to 0.75 m ^-1 , and the first
When the reverse bending radius was 0.5 R, the straightened pipe became flat and the pipe flatness was 0.94.

Conclusion: Even when the V-groove roll is used, pipe flattening occurs and it is not practical.

Test 3 In the same manner, the roll shape was measured at a pipe temperature of 20 ° C and the caliber diameter was 1
It was carried out using a caliber roll having a diameter of 7.0 mm and a diameter of 150 mm.

Curvature after correction is from 0.018 to 0.084m ^-1 , and the first
When the reverse bending radius is 0.5R, the flatness of the pipe after straightening is
It was practically a perfect circle at 0.995.

Conclusion: When the caliber roll is used, by setting the first reverse bending radius to 0.5R at 20 ° C., it is possible to correct the target curvature with a flatness that does not hinder practical use.

Test 4 Using the caliber roll of Test 3, set the pipe temperature to 100 ℃.
Was carried out as.

The corrected curvature was 0.016 to 0.018 m ^-1 , and in all cases the flatness was 0.996, which was a practically perfect circle.

Conclusion: By using a caliber roll at 100 ° C, it is possible to correct the target curvature of curvature with a flatness that does not hinder practical use in all cases of the first bending radius of 0.5 to 2R.

Test 5 Material polypropylene; glass transition point -10 ° C, melting point 180 ° C Pipe outer diameter 34.0mm Wall thickness 3.7mm Length 10m Coil outer diameter 1.4m Using the caliber roll of Test 3, pipe temperature is 10 ° C and the first reverse The bending radius was 0.5 to 2R.

Curvature after correction goes from 0.019 to 0.090m ^-1 , and vice versa.
When the reverse bending radius is 0.5R, the flatness of the pipe after straightening is
It was practically a perfect circle at 0.995.

Conclusion: When using the caliber roll, by setting the first reverse bending radius to 0.5R at 10 ° C (glass transition point + 20 ° C), it is possible to correct the target curvature with a flatness that does not hinder practical use. it can.

Test 6 Material Polypropylene; Glass transition point -10 ° C Melting point 180 ° C Pipe outer diameter 34.0mm Wall thickness 3.7mm Length 10m Coil outer diameter 1.4m Using the caliber roll of Test 3, pipe temperature is -10 ° C.
As a result, the pipe cracked under all the conditions of the first reverse bending radius of 0.5 to 2R.

Conclusion: The pipe is cracked at the glass transition point, which is not practical.

Glass transition temperature -120 ° C, melting point 120 ° C as described above
For medium density polyethylene pipes, caliber rolls are used, and the first bend radius is 0.5R at a temperature of 20 ° C, and the target bend straightening is within a range of 0.5-2R at 100 ° C. It was confirmed that it could be done.

Further, for polypropylene pipes having a glass transition temperature of -10 ° C and a melting point of 180 ° C, a caliber roll is used and the temperature is 10 ° C.
The first bending radius is 0.5R at ℃ (glass transition temperature + 20 ℃)
As a result, it was confirmed that the target bending correction can be performed.

〔The invention's effect〕

The bending correction method of the present invention is as described above, and the bending can be corrected without adversely affecting the quality of the pipe.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an apparatus for carrying out the method of the present invention. 61 to 67 ... Bending straightening roll.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Omori 2-17, 22, Higashiyama, Konan-ku, Yokohama-shi, Kanagawa (56) References 59-32404 (JP, U) 52-66144 (JP) , U)

Claims (1)

[Claims] 1. A strong straightening straightening is first performed by using a caliber roll by a bending straightening machine consisting of rolls arranged so as to be able to reverse bend the bending of a long thermoplastic pipe wound in a coil shape. A method for straightening a bend in a plastic pipe, characterized in that the straightening is then performed, and then a weak bend is sequentially corrected.