KR101738012B1 - Inspection method for cold fusion on fusion joint of polyethylene pipes - Google Patents

Abstract

Disclosed is a cold fusion inspection method of a fused portion of a polyethylene pipe. According to the present invention, the cold fusion inspection method of the fused portion of the polyethylene pipe comprises: (a) a step of connecting each pipe by applying power in accordance with a condition set according to a specification of a pipe; (b) a step of obtaining a reference distance value by measuring a distance between a heat plate or a heat line and a boundary line; (c) a step of connecting the pipes by applying power in accordance with the condition set according to the specification of the pipe; (d) a step of measuring a distance between a hot plate or the heat line and the boundary line to obtain a measured distance value; and (e) a step of comparing the measured distance value obtained in step (d) with a reference distance value obtained in step (b), and if the measured distance value is smaller than the reference distance value, determining an existence of a cold fusion defect of the fused portion formed in step (c). According to the present invention, the present invention is able to provide an effect of nondestructively inspecting whether or not cold fusion, which is a rheological defect, has occurred in the fused portion.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a cold fusion method for a polyethylene pipe fused portion,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a cold fusion testing method for a polyethylene pipe fused portion, and more particularly, to a cold fusion testing method for a polyethylene pipe fused portion, which can accurately examine whether a cold fusion, which is a rheological defect, ≪ / RTI >

The mankind, which relied on coal and oil, has been able to live a better life with the use of clean energy gas, and the gas industry has developed rapidly in line with the expectations of mankind. Because of its various advantages such as cleanliness and ease of use, gas has been widely used for home and industrial use, contributing to the quality improvement of the people's life and the development of the national industry.

However, as the use of natural gas increases, the number of pipelines for gas supply increases, and gas accidents also increase. Due to the increase in gas accidents, there has been a growing interest in the safety of gas pipelines. Until the 1980s, PLP (polyethylene-coated steel pipe), in which polyethylene was coated on a steel pipe, was mainly used for the underground piping of the city gas piping. However, steel pipes and polyethylene-coated steel pipes suffered from corrosion problems together with difficulties in construction, resulting in many problems such as safety and maintenance.

In order to solve these problems, the use of polyethylene pipes with various conditions such as durability, economy, bonding, corrosion resistance, impact resistance and chemical resistance has increased rapidly, and since 1995, polyethylene pipes have been mainly used as low pressure pipes in Korea. The stability of construction depends on the pipe fusion performance rather than the material properties of the pipe itself. An important factor directly affecting the fusion performance is the performance of the fusion equipment used for fusion and compliance with the fusion procedure.

Unlike the butt welding (BUTT welder) which welds the polyethylene pipe and the pipe together, the electric welding uses a connection socket joint pipe in which a hot wire is installed. That is, after the joint pipe is inserted into the joint portion, heat is supplied to the heat wire inside the joint pipe to fuse the inside of the joint pipe and the outer surface of the polyethylene pipe.

Hereinafter, a method of connecting a polyethylene pipe using fusion splicing method using a connection socket will be described with reference to FIG. 1 in the accompanying drawings.

As shown in Fig. 1 (A), after pipes 2 and 3 to be connected to both sides of the socket 1 in which the hot wire 1-1 is embedded are inserted, as shown in Fig. 1 (B) When electric power is applied to the hot wire 1-1, heat is generated in the hot wire 1-1 and the socket 1 and the pipes 2 and 3 are connected to each other as shown in FIG. 1C and FIG. And is melted and integrated by fusion heat.

In this way, when two pipes are fused and connected using the connection socket, fusing defects may occur in the fused portion. For example, defects such as defective fusion, pore generation, defects due to soil or foreign matter may occur, and rheological defects may occur without a shape such as cold fusion.

Cold fusion, which is a rheological defect, refers to incomplete fusion, which occurs when a polyethylene resin is melted insufficiently when it is melted. Such a cold fusion defect is a phenomenon in which the melting heat is not sufficiently transferred due to the problem of the polyethylene material itself or the external environment (temperature), resulting in a poor melting state. In the tensile fracture test, the fracture surface is smooth and white, These defects cause shortening of the lifetime of the connection (pipe).

That is, as shown in FIG. 2, the heat of fusion generated in the hot wire 1-1 is transmitted to the hot wire 1-1 gradually from the hot wire 1-1 as the temperature is increased according to the application time of the power. However, due to a variety of impediments such as defects of the polyethylene itself, external temperature conditions, power application time, etc., the heat of fusion of the hot wire 1-1 is transmitted below the reference value, A fusion failure occurs.

However, there have been various methods for inspecting the defects of the pipe welded portion, but there has been no way to inspect defects such as the cold fusion described above.

For example, Korean Patent Laid-Open Publication No. 10-1998-72372 (published on November 11, 1998) discloses a method of confirming fusion bonding when a polyethylene pipe connection portion is fusion-bonded. According to this method, when a colored paint layer is painted on the end of the hot wire of the polyethylene pipe connecting portion where the hot wire is located on the flange portion, a colored melt flows between the pipe connecting portion and the polyethylene pipe, When the fusion is completed, the melt is protruded into the groove to visually confirm the fusion, and whether or not there exists a rheological defect such as cold fusion is present in the inside of the flange portion I did not know.

On the other hand, Korean Patent Registration No. 10-438373 (Published on July 23, 2004) discloses an ultrasonic inspection apparatus for an electric fused portion of a portable polyethylene pipe. According to this apparatus, by using an array ultrasonic wave, an electrical fusion portion of a polyethylene pipe can be imaged in real time, and the fusion state and existence of a foreign substance can be directly confirmed using the image, so that fusion defects having a shape such as a foreign substance can be easily Defects such as cold fusion which can be inspected but which is rheological defect can not be inspected.

As described above, in the inspection method disclosed in the prior art, it is impossible to inspect whether the cold fusion, which is a rheological defect that may occur in the fused portion of the polyethylene pipe, occurs. Therefore, a means for non-destructively inspecting the cold fusion has been urgently required.

. Korean Patent Laid-Open No. 10-1998-72372 (published on November 11, 1998) . Korean Patent No. 10-438373 (Notification Date: Jul. 2003)

It is an object of the present invention to provide a means for non-destructively inspecting whether a cold fusion, which is a rheological defect that may occur in a fusion portion of a polyethylene pipe, occurs.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to at least partially solve the problems in the conventional arts. It can be understood.

According to the present invention, the above object can be accomplished by a method of manufacturing a pipe according to the present invention, comprising the steps of: a) connecting piping for obtaining a reference distance value by butt welding using a hot plate or fusing using a connection socket with a built- Connecting the respective pipes by applying power to the pipes; b) Phased array ultrasonic inspection of the fused portion of the pipe connected in accordance with the step a), melting the fused portion by the fusing heat generated from the hot plate or hot line, and then determining the boundary between the cooled portion and the portion where the fusing heat is not transmitted Obtaining a reference distance value by measuring a distance between the heat plate or the heat line and the boundary line; c) Fitting the pipes of the same size as the pipe used in step a) by butt welding using a hot plate or fusing them using connection socket with built-in hot wire, And connecting the pipes with each other; d) Phased array ultrasonic inspection of the fused portion of the pipe connected in accordance with the step c) is performed to melt the fused portion by the fusing heat generated from the hot plate or hot line, and then determine the boundary between the cooled portion and the portion where the fused heat is not transmitted Measuring a distance between the heat plate or the heat line and the boundary line to obtain a measured distance value; And e) comparing a reference distance value corresponding to a pipe having the same standard as that of the pipe used in the step c) among the reference distance values obtained in the step b) and the measured distance value obtained in the step d) And judging the cold fusion defect or the overfusion defect of the fused portion formed in the step c) when the measured distance value is smaller or larger than the reference distance value, by the cold fusion method of the polyethylene pipe fused portion .

Further comprising storing the reference distance values obtained by performing the steps a) and b) in accordance with the specification of each pipe in the storage unit according to the specifications of the pipe,

The method according to any one of claims 1 to 5, wherein step (e) comprises the steps of: obtaining a measured distance value obtained in step d) and a specification for the pipe, Comparing the measured distance value with the measured distance value; And comparing the reference distance value with the measured distance value. If the measured distance value is smaller than the reference distance value, the fused portion is determined as a cold fusion defect. If the measured distance value is larger than the reference distance value, And outputting the determination result.

According to the present invention, a fused portion of a polyethylene pipe is flawed by a phased array ultrasonic flaw detector, and the fused portion is melted by a fusing heat generated from a hot plate or hot wire, and the boundary between the cooled portion and the portion where fusing heat is not transmitted is grasped, It is possible to nondestructively check whether or not a cold fusion which is a rheological defect has occurred in the fused portion by comparing the measured distance value obtained by measuring the distance between the perimeter and the reference distance value It is possible to provide an effect.

That is, it is possible to measure the distance at which the fusion heat from the hot plate or hot wire is measured by the phased array ultrasonic wave at the fused portion of the pipe, and compare the measured distance value with the reference distance value at the normal fusion, It is possible to provide an effect.

1 is a schematic cross-sectional view for explaining a piping connection process according to the prior art.
2 is a schematic view for explaining a cold fusion defect in a polyethylene pipe fused portion;
3 is a flowchart for explaining a cold fusion method of a polyethylene pipe fused portion according to the present invention.
4 is a schematic cross-sectional view for explaining a cold fusion test method of the polyethylene pipe fused portion shown in FIG.
FIG. 5 is a photograph showing a result of a fusing part being flawed by a cold fusion fusing method of the polyethylene pipe fusing part shown in FIG.
FIG. 6 is a schematic block diagram showing a system for performing the cold fusion inspection method of the polyethylene pipe fused portion shown in FIG. 3; FIG.
FIGS. 7 to 11 are photographs showing phonetic array ultrasonic measurement results for explaining the cold fusion method of the polyethylene pipe fused portion shown in FIG.
12 is a flowchart for explaining another embodiment of the cold fusion method of the polyethylene pipe fused portion according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, the well-known functions or constructions are not described in order to simplify the gist of the present invention.

3 is a flowchart for explaining a cold fusion method of a polyethylene pipe fused portion according to the present invention and FIG. 4 is a schematic cross-sectional view for explaining a cold fusion method of a polyethylene pipe fused portion shown in FIG. 3 .

3 and 4, in the cold fusion testing method of the polyethylene pipe fused portion, after fusing the respective pipes 50 by the standard, the fused portion 64 is flawed by the phased array ultrasonic device 10, After obtaining the reference distance values for the pipes 50, the fused portion 64 of the pipe 50 actually fused at the site is scanned by the phased array ultrasonic device 10 to obtain the measured distance value, If the measured distance value is equal to or greater than the reference distance value, it is determined to be normal fusion. If the measured distance value is greater than or less than the reference distance value, it is determined to be defective fusion, 64) can be inspected non-destructively.

This will be described more specifically.

Although a variety of methods are known in the prior art for connecting the pipes 50 by fusing them in advance, in the present embodiment, it is possible to connect both pipes 50 by using the connection socket 60 in which the hot wire 62 is embedded I explain it as a standard. The fusing device using the connection socket 60 is configured to apply a current of a predetermined voltage to the hot wire 62 for a set time, and can set the time for power application time and set the voltage of the applied current. The connecting socket (60) has a connecting portion electrically connected to the fusing device.

The phased array ultrasound apparatus 10 performs the array ultrasonic inspection on the fused portion 64 of the piping 50 to obtain the ultrasonic wave And to acquire and acquire the boundary line BL between the cooled portion and the portion where the fusion heat is not transferred, by the image heat and the numerical value.

a) step (S1)

The pipes 50 for obtaining the reference distance value are fused by using the connection socket 60 in which the heating wire 62 is embedded. At this time, power is applied to the connection socket 60 based on the conditions set according to the specifications of the pipes 50, and the pipes 50 are connected. That is, after the pipes 50 are classified according to the specifications, the pipe 50 for each standard is fused and connected by a fusing device using the connection socket 60.

For example, in the case of a pipe 50 having a density of 0.939 g / cm 3, an outer diameter of 225 mm, a thickness of 20.5 mm, and a length of 250 mm, an RMS voltage of 39.8 V is applied for 600 seconds.

When power is applied to the heat line 62, the heat of fusion formed by the heat line 62 gradually diffuses over time as shown in FIG. 4 to melt the connection socket 60 and the pipe 50 Thereby forming a fused portion 64. That is, the boundary region between the part of the pipe 50 and the connection socket 60 and the peripheral region thereof are melted by fusion heat of the heat ray 62 and fused together. At this time, a boundary line BL is formed at the boundary between the region where the heat of fusion generated from the heat line 62 reaches and the region where the heat of melting has not reached. The distance between the boundary line BL and the heat line 62 has a constant value (distance value) in the case of the fused portion 64 normally fused.

This step is to obtain the reference distance values for the sizes of the pipes 50, respectively, and use them as comparison data. That is, when the measurement distance values of the respective pipes 50 to be installed in the field are obtained by acquiring the reference distance values of the respective pipes 50 according to the standard and storing the data, So that it can be compared with a reference distance value corresponding to the piping 50 of the standard.

b) In step S2,

The fused portion 64 of the pipe 50 connected in accordance with the step a) described above is flawed by the phased array ultrasonic device 10 and melted by the fusing heat generated from the hot line 62, (BL) of the portion where the heat is not transmitted. Then, the distance L1 between the heat line 62 and the boundary line BL is measured to obtain the reference distance value. That is, the phased array ultrasound apparatus 10 is melted by the heat of fusion of the heat line 62, but the polyethylene resin is melted by the heat of fusion of the heat line 62 even though it can not sense the tissue change of the cooled fused portion 64 Since the boundary line BL between the cooled part and the part where no fusion heat is transmitted can be sensed and outputted to the screen, the reference distance value of the fused portion 64 of each pipe 50 according to the standard is obtained will be. Each of the reference distance values obtained by the above process can be stored in a separate system connected to the phased array ultrasonic apparatus 10 or the phased array ultrasonic apparatus 10.

c) Step S3:

The piping 50 of the same size as that of the piping 50 used in the step a) is fused to the piping 50 using the connection socket 60 in which the piping 50 is installed at the construction site, And power is applied according to the set conditions to connect the pipes 50. That is, after inserting the ends of the pipes 60 into both sides of the connection socket 60, power is supplied to the heat line 62 through connection ports provided on both sides of the connection socket 60.

For example, in the case of a pipe 50 having a density of 0.939 g / cm 3, an outer diameter of 225 mm, a thickness of 20.5 mm, and a length of 250 mm, an RMS voltage of 39.8 V is applied for 600 seconds.

The application time of power applied to the hot wire 62 of the connection socket 60 is set differently according to the specification of each pipe 50 and applied.

d) In step S4,

Phase array ultrasonic inspection is performed on the fused portion 64 of the piping 50 connected to the phased array ultrasonic device 10 according to the step c) to melt by the fusing heat generated from the hot line 62, And the distance L 2 between the heat line 62 and the boundary line BL is measured to obtain the measured distance value.

e) step S5,

If the measured distance value obtained in step d) is compared with the reference distance value obtained in step b), the fused portion 64 formed in the step c) is judged as a cold fusion defect .

For example, as shown in Fig. 5 (a), the fused portions 64 of the piping 50 (control group - pipe heated under normal heating conditions) for obtaining the reference distance value with the phased array ultrasonic apparatus 10 The distance L1 between the heat line 62 and the boundary line BL is 5.9 mm and the fused portion 64 of the pipe 50 connected at the construction site is flawed by the phased array ultrasonic device 10 As a result, if the distance L2 between the heat line 62 and the boundary line BL is 2.5 mm as shown in FIG. 5 (b), the measurement distance value 2.5 mm is smaller than the reference distance value 5.9 mm, The fused portion 64 of the piping 50 connected at the site is determined as a cold fusion defect.

If the measured distance value is larger than the reference distance value, it is judged to be an overfusion defect. That is, when the measurement distance value is larger than the reference distance value, the fusion heat is excessively generated from the heat line 62, causing the fusion portion 64 to melt excessively. Thus, when the measured distance value is larger than the reference distance value, it is determined to be an overfusion defect.

The cold fusion testing method of the polyethylene pipe fused portion is a method of measuring the standard distance values obtained by performing the steps a) and b) according to the specification of each pipe 50, ). ≪ / RTI > That is, the control unit 20 stores the reference distance values measured by the phased array ultrasonic apparatus 10 in the storage unit 40.

6, after the measurement distance value obtained in step d) and the standard for the pipe 50 are inputted, the process of step d) Comparing the reference distance value and the measured distance value with respect to the pipe 50 stored in the storage unit 40 that conforms to the standard; comparing the measured distance value with the reference distance value; and if the measured distance value is smaller than the reference distance value It is determined that the fused portion 64 is a cold fusion defect and the reference distance value is compared with the measured distance value as shown in Fig. 12. If the measured distance value is larger than the reference distance value, it is determined that the fused defect is an overfusion defect, The method comprising the steps of: That is, when the reference distance value of the piping 50 for each standard obtained through the step b) is input through the phased array ultrasonic apparatus 10 or other input device, the control unit 20 stores the reference distance value in the storage unit 40, And if the measured distance value of the piping 50 in the construction site obtained through the step d) is input through the phased array ultrasonic device 10 or other input device, The reference distance value for the standard pipe 50 is called from the storage unit 40 and is compared with the measured distance value and the result is displayed on the display unit 30 or outputted.

The fused portion 64 of the polyethylene pipe 50 is scanned by the phased array ultrasonic device 10 to determine the distance L2 between the heat line 62 and the boundary line BL and compared with the reference distance value The cold fusion defect of the fused portion 64 can be determined so that the cold fusion defect inspection of the fused portion 64 of the polyethylene pipe 50 can be easily, quickly, and accurately confirmed in a non-destructive manner.

[Experimental Example]

Pipes 50 having a polyethylene density of 0.939 g / cm 3, an outer diameter of 225 mm, a thickness of 20.5 mm and a length of 250 mm are connected to a connection socket 60 having a heating wire 62, respectively, Voltage) of 39.8 V was applied for 780 sec, 600 sec, 420 sec, 250 sec, and 120 sec, respectively.

The experimental results are shown in Figs. 7 to 11.

Referring to FIG. 7, the effective value voltage 39.9 V is applied for 780 seconds to fuse, and the distance L1 between the heat line 62 and the boundary line BL is 7.2 mm.

Referring to FIG. 8, the effective value voltage 39.9 V is applied for 600 seconds to fuse, and the distance L1 between the heat line 62 and the boundary line BL is 5.9 mm.

Referring to FIG. 9, the effective value voltage 39.9 V is applied by fusing for 420 seconds, and the distance L1 between the heat line 62 and the boundary line BL is 3.7 mm.

10, an effective value voltage of 39.9 V is applied for 240 sec and fused, and the distance L1 between the heat line 62 and the boundary line BL is 1.8 mm.

11, an effective value voltage of 39.9 V is applied for 120 seconds to fuse, and the distance L1 between the heat line 62 and the boundary line BL is 1.7 mm.

As described above, it has been found that the measured distance value is lowered according to the time of applying power to the hot line 62. The lowering of the measured distance value means that the heat of the hot line 62 has not reached a sufficient distance, This can be judged as a defective fusion defect due to cold fusion.

As a result of breaking test of welded pipes according to each embodiment, it was found that as the heating time, that is, the time of applying power to the heat line 62, the fusion failure rate due to the cold fusion phenomenon is lowered I could.

Based on the experimental result, when the power is applied to the hot wire 62 at a predetermined normal heating time (time for applying the set power to the hot wire for a predetermined time) according to the specifications of the pipes 50, the heating time is 600 sec Sec or 600 sec or more, it was found that the cold fusion defect was not caused in the fused portion 64, and it was found that it could cause an overfusion defect when applied for 780 seconds. Therefore, it is possible to easily judge whether or not the fused portion 64 of the piping 50 to be welded and welded on the basis of the reference measurement value is connected, in particular, a rheological defect (cold fusion) do.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is obvious to those who have. Accordingly, it should be understood that such modifications or alterations should not be understood individually from the technical spirit and viewpoint of the present invention, and that modified embodiments fall within the scope of the claims of the present invention.

10: phased array ultrasonic device 20:
30: Display section 40: Storage section
50: piping 60: connection socket
62: heat line 64: fused portion
BL: boundary line L1, L2: distance

Claims (3)

a) The pipes for obtaining the reference distance value are fused by butt welding using a hot plate or fused using a connection socket with a built-in hot wire, and power is applied according to the conditions set in accordance with the specification of the pipe, Connecting;
b) Phased array ultrasonic inspection of the fused portion of the pipe connected in accordance with the step a), melting the fused portion by the fusing heat generated from the hot plate or hot line, and then determining the boundary between the cooled portion and the portion where the fusing heat is not transmitted Measuring a distance between the hot plate or the heat line and the boundary line to obtain reference distance values, respectively;
c) In the construction site, pipes of the same size as the pipes used in step a) are welded together by butt welding using a hot plate, or they are fused using connection sockets with hot wire. Connecting the pipes by applying power to the pipes;
d) Phased array ultrasonic inspection of the fused portion of the pipe connected in accordance with the step c) is performed, and the fused portion of the pipe is melted by the fusing heat generated from the hot plate or heat line, and the boundary between the cooled portion and the fused heat is not grasped Measuring a distance between the heat plate or the heat line and the boundary line to obtain a measured distance value; And
e) comparing a reference distance value corresponding to a pipe having the same standard as that of the pipe used in the step c) among the reference distance values obtained in the step b) with the measurement distance value obtained in the step d) Determining a cold fusion defect of the fused portion formed in the step (c) if the distance value is smaller than the reference distance value,
The steps a) and b) may further include storing the reference distance values obtained in accordance with the specification of each pipe in the storage unit according to the specification of the pipe,
The step e)
Wherein the measurement distance value obtained in step d) and the standard for the pipe are input, and then the reference distance value and the measurement distance value for the pipe stored in the storage unit, which coincides with the specification of the pipe input in step d) ; And
Comparing the reference distance value with the measured distance value to determine that the fused portion is a cold fusion defect if the measured distance value is smaller than the reference distance value, and outputting a determination result.
(Method for Cold Fusion Inspection of Polyethylene Pipe Fuselage). delete The method according to claim 1,
The step e)
And when the measured distance value is larger than the reference distance value, it is determined that the overfusion defect is present.
(Method for Cold Fusion Inspection of Polyethylene Pipe Fuselage).

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