CN101101276A - Polyolefin pipe electrofusion welding joint cold welding defect supersonic detection method - Google Patents

Abstract

The invention relates to a detection method of welded quality of polyolefin piping electric-fusion welded joint. The intention is that the detection method should have the characteristics of high detected precision, visualize and visible, easy and convenience. The plan of technology is that: the ultrasonic detection method of the cold welding bug of the polyolefin piping electric-fusion welded joint, it realizes according to the following methods: the detection of normal weld tubular product and the one section of junction seal part by ultrasonic testing method, getting the distance L of typical line and wire in the ultrasonic reflected signal image; doing ultrasonic detection for the needed electrocast joint also, getting the distance L'of typical line and wire in the ultrasonic reflected signal image; judging the needed electrocast joint if exist the cool welding bugs according to the L and L' in the above two images. Taking the L and L'to the formula: H=L'/L, and judging the needed electrocast joint if exist the cool welding bugs. The L and L' of typical line and wire in the ultrasonic reflected signal image can get by software.

Description

The supersonic detection method of polyolefin pipe electrofusion welding joint cold welding defect

Technical field

The present invention relates to a kind of detection method of pressure pipeline, specifically is the detection method of polyolefin pipe electric fusion joint welding quality.

Background technology

Polyolefin pipe is widely used in the conveying of danger medium such as combustion gas, and the connection between the tubing is the important step that influences its structural intergrity and creep rupture strength.Wherein the electric smelting welding becomes the main method that polyolefin pipe connects because constructing operation is simple, and field apparatus is light, and speed of welding is fast.Its ultimate principle is that the heating element of high value is imbedded internal surface of sleeve pipe in advance, be enclosed within after the joint of two pipeline pipes, to the heating element heating of switching on, the inside surface of sleeve and the outside surface of pipeline (or pipe fitting) are melted respectively, become as a whole behind the cooling curing, thereby reach the welding purpose.Because might there be various defectives in the polyolefin pipe joint, and most polyolefin pipe accident all causes by the joint defective, makes joint become the weak link of polyolefin pipe system.For example, although pipe joint be welded with concrete operating provision (for example every kind of welding machine all has the weld interval of regulation to the pipe joint of various different materials and diameter), but because a variety of causes usually causes the deficiency of weld interval or bonding power, so that the cold welding defective of welding joint occurs, and existing detection means nearly all can't effectively detect this defective.Because when cold welding takes place, fusing and counterdiffusion have mutually taken place in the polyolefine material of sleeve lining and outer pipe wall, but because the input heat is not enough, the contact bed molecule does not spread fully and tangles, the interpenetrative degree of depth is not enough between the molecule, so strength of joint can not reach the expection requirement of strength.For improving the security of polyolefin pipe, except that improving the joint quality, perfect joint defective man-rate method should be arranged also by correct welding technology and the welding machine selected, prevent to be with the excessive defect pipeline to put into operation.

At present, the detection method of polyolefin pipe electrofusion welding joint has destructive test, visual detection and Ultrasonic Detection etc.The destructive detection is a kind of detection method of adding up sampling observation character, can not detect at a certain specific joint; And visual detection be owing to can not observe directly the situation of joint inside, so its reliability can not be guaranteed.Though Ultrasonic Detection can directly obtain the status information of material internal, can there be the defective of macro-size to differentiate to some, as pore, be mingled with and tinsel dislocation etc., can't detect the situation of joint cold welding.

Summary of the invention

The objective of the invention is to overcome the deficiency of above-mentioned background technology, propose a kind of detection method of electrofusion welding joint cold welding degree, this method should have accuracy of detection height, visual in image, characteristics simply and easily.

Technical scheme provided by the invention is: the supersonic detection method of polyolefin pipe electrofusion welding joint cold welding defect, realize by the following method:

One, utilizes supersonic detection method to the detecting of a certain cross section of the tubing of normal welding and joint welding portion, obtain the ultrasonic reflection signal image, record characteristic curve and distance L wiry in this ultrasonic reflection signal image;

Two, electric fusion joint to be measured is carried out Ultrasonic Detection equally, obtains the ultrasonic reflection signal image in a certain care cross section, record characteristic curve in this ultrasonic reflection signal image and distance L wiry ';

Three, judge according to the distance of the characteristic curve in above-mentioned two images distance wiry whether this electric fusion joint to be measured exists the cold welding defective.

With described L and L '

The substitution formula: $H=\frac{L^{\′}}{L}$

In the formula: H represents with number percent, characterizes the cold welding degree of sample to be tested, thereby judges whether this welding joint exists the cold welding defective.

Characteristic curve in the described ultrasonic reflection signal image and distance L wiry ' or the L available software record.

Detection method provided by the invention can be by the ultrasonic figure of comparative sample electric smelting sleeve and electric smelting sleeve inner to be measured, determine the welding quality situation of electric smelting sleeve to be measured intuitively and whether have the cold welding defective, not only accuracy of detection is higher, visual in image, can detect any specific joint, and detection mode is simple and convenient, is highly suitable for using in the engineering.

Description of drawings

Fig. 1 electric fusion joint welding process synoptic diagram.

Fig. 2 is the Ultrasonic Detection mode synoptic diagram of electric fusion joint.

Fig. 3 is the ultrasonic imaging contrast synoptic diagram of same time welding of PE material and power.

Fig. 4 is characteristic curve and a distance versus synoptic diagram wiry under PE material different time, the power.

Fig. 5 is characteristic curve and a distance versus synoptic diagram wiry under the PPR material electric fusion joint different time.

Embodiment

Polyolefin electric fusion joint welding ultimate principle is that the tinsel C (heating wire) with high value imbeds internal surface of sleeve pipe in advance, makes the heat up fusing and merging each other of polyolefin around the tinsel by the electrothermal wire heating, can form welding joint after the cooling.In welding process, raise rapidly near polyolefine material temperature wiry, in the time of near temperature is increased to polyolefinic fusing point, the crystalline region begins fusing, and formation fusion zone, along with the prolongation of weld interval, the fusion zone constantly enlarges, and fusion zone and solid-state handing-over line A are according to certain rules to sleeve outer wall displacement (shown in Figure 1).

Show by theoretical research: this handing-over line A and distance wiry are closely related with parameters such as heat time heating time, power input, environment temperatures; To the polyolefin electric fusion joint of same material specification, under certain welding condition (weld interval, power input, welding initial temperature), the distance between this handing-over line and tinsel is certain certain value.Therefore can adopt distance between this handing-over line and tinsel to characterize the order of severity of cold welding indirectly.

The inventor adopts existing ultrasonic imaging technique that electric fusion joint is carried out Ultrasonic Detection and (detects synoptic diagram and see Fig. 2 by a large amount of experimental studies; D is an electric fusion joint among the figure, and E is a ultrasonic probe, and G is a tubing, and C is a heating wire), detect the ultrasonic reflection signal line of certain distance position, tinsel top, be used as the characteristic curve t that differentiates the cold welding degree among the present invention.

Carry out Ultrasonic Detection by a large amount of different size electric fusion joints and record a video in real time, and the experiment of the temperature field test of different depth position, confirm that the characteristic curve t that Ultrasonic Detection is found is exactly the handing-over line A in electric fusion joint fusion zone and solid-state district.It forms reason mainly is in polyolefin electric fusion joint welding process, be present in gas in the material, water etc. under the effect of sweating heat to external diffusion, and arrive solid-state district by the fusion zone, collect in the intersection in fusion zone and solid-state district at last, form a small air gap line, thereby form the ultrasonic reflections signal.In addition, the minute differences of the acoustic feature in acoustic feature and solid-state district also helped the formation of this characteristic curve after solidified the fusion zone.This characteristic curve and distance wiry have good corresponding relation with weld interval and power.A large amount of evidence: this characteristic curve and wiry under same weld interval and the power apart from basically identical.Fig. 3 is the ultrasonic imaging figure (totally 9 figure) of three groups of same times and power welding electric fusion joint.As seen from the figure, characteristic curve and distance wiry are basic identical under same weld interval and the power, recording this by software is 0.1mm apart from maximum deviation, it can be said that bright: judge that with this characteristic curve and distance wiry the cold welding degree has reliable repeatability.

Show by test: this characteristic curve and distance wiry be along with welding heat (weld interval, bonding power) changes, and dull one-to-one relationship is arranged.Therefore, judging the cold welding degree with this characteristic curve and distance wiry, is feasible technically.With PE80 material DN90 electric fusion joint is example, and characteristic curve and distance versus wiry are seen Fig. 4 (totally 14 figure) under different welding heats (weld interval T, the bonding power P) situation.By detectable characteristic curve of software and distance wiry, to test at the electric fusion joint of PE80 material DN63, DN90, three kinds of specifications of DN110, characteristic curve that records and distance wiry see Table 1.As can be seen from Table 1: 1) characteristic curve and distance wiry increase along with the increase of weld interval, bonding power; 2) if weld interval or bonding power more than or equal to 50% of normal value, characteristic curve is relevant with the welding heat (product of weld interval and bonding power) of input with distance wiry, adopt different weld interval and bonding power, if the product of weld interval and bonding power is identical, then characteristic curve and distance wiry are also basic identical.3) characteristic curve and distance wiry and electric smelting weld interval and power have approximate linear, if weld interval or bonding power are more than or equal to 50% of normal value, characteristic curve and distance wiry have approximate linear with the welding heat (product of weld interval and bonding power) of input; The video recording of overall process Ultrasonic Detection after this characteristic curve forms, outwards advanced with the increase of approximate even velocity with weld interval as can be seen when this welded from electric fusion joint; In addition, analyze from the electric fusion joint thermodynamical model, when fusion area handing-over line and distance wiry less than sleeve diameter, when the sleeve outer surface temperature variation is little when welding, do not degrade during welding, under the tinsel misalignment, can be similar to establishment from the yet provable above-mentioned linearity of numerical analysis result.Therefore, the cold welding degree can be similar to following formula and represent:

$H=\frac{L^{\′}}{L}---\left(1\right)$

In the formula: H-cold welding degree (represent normal welding heat input, represent) with number percent

Characteristic curve and distance wiry (mm) during L '-cold welding

Characteristic curve and distance wiry (mm) when L-normally welds

Therefore, a kind of supersonic detection method of polyolefin pipe electrofusion welding joint, can realize by the following method:

One, utilize supersonic detection method to normal welding (standard weld interval and bonding power, usually determine by welding procedure test) tubing and the detecting of a certain cross section of joint welding portion, obtain the ultrasonic reflection signal image and (appear at a characteristic curve reflected signal of tinsel top in the image, can carry out dynamic focusing to instrument, make the clear demonstration of characteristic curve energy), record the characteristic curve of (electric fusion joint zone line) in this ultrasonic reflection signal image and distance L wiry (for reducing error, serving as to measure basic point) with software (ultrasonic detection equipment institute configuration software) with the center of characteristic curve image and tinsel image;

Two, electric fusion joint to be measured is carried out Ultrasonic Detection equally, obtains the ultrasonic reflection signal image in a certain care cross section, with software record the characteristic curve of (electric fusion joint zone line) in this ultrasonic reflection signal image and distance L wiry ';

Three, judge according to the distance of the characteristic curve in above-mentioned two images distance wiry whether this electric fusion joint to be measured exists the cold welding defective.L＞L ' generally speaking, this can be used as a kind of method for qualitative analysis.

Further, when adopting quantitative test, can just described L and L '

The substitution formula: $H=\frac{L^{\′}}{L}$

In the formula: H-cold welding degree, represent (the input heat during the normal welding of representative) with number percent, characterize the cold welding degree of sample to be tested, thereby judge whether this welding joint exists the cold welding defective.

A large amount of cold welding samples are carried out demonstration test, see Table 2 by the cold welding degree of 1 illness that has not attacked the vital organs of the human body of formula and the comparing result of the actual welding heat of importing, as known from Table 2, in welding heat 50% o'clock more than or equal to normal sweating heat value, the cold welding degree that is characterized by formula (1) and the deviation range of actual numerical value are-4.1%～4.2%, and precision can satisfy the requirement that engineering is used.

According to the mechanical property test of a large amount of cold welding samples (stretch, peel off, high temperature static pressure, normal temperature static pressure test).When the calorie value of input was smaller or equal to 70% normal value when cold welding test welding, the mechanical property of sample can not all satisfy the requirement of electric fusion joint product standard; When the calorie value of input was greater than 75% normal value when cold welding test welding, the mechanical property of sample can satisfy the requirement of electric fusion joint product standard; Considering with the characteristic curve to be the cold welding degree H and the actual deviation that has less than 5% of parameter characterization, therefore in practice, is benchmark with H value 80%, when H more than or equal to 80% the time, decidable is qualified; When H less than 80% the time, there is the cold welding defective in sample.

Conclusion of the present invention is not only applicable to the PE80 material, also is applicable to the electric fusion joint of polyolefins pipelines such as PE100, PPR, PP; Reason is that the performance of polyolefins material is similar to the PE80 material.The PPR material DN63 electric fusion joint of producing with material pipeline Science and Technology Co., Ltd. in the Zhejiang is that example: Fig. 5 be the Ultrasonic Detection figure that 100%T and 70%T obtain when welding, the characteristic curve and the distance wiry that record normal welding (100%T) electric fusion joint with supersonic testing method are 2.3mm, and its characteristic curve of electric fusion joint and the distance wiry of 70%T welding are 1.6mm; H=1.6/2.3=69.6% compares with actual value as can be known, and its error is 0.4%.

The present invention can realize the differentiation of cold welding defective in the polyolefin electric smelting welding joint, is highly suitable for using in the engineering.

Embodiment 1: with PE80 material DN90 electric fusion joint is example, and the characteristic curve and the distance wiry that record normal welding electric fusion joint with supersonic testing method are 3.2mm; And be 2.6mm with characteristic curve and the distance wiry that supersonic testing method records electric fusion joint to be measured; H=2.6/3.2=81.3% as can be known, decidable is qualified.

Embodiment 2: with PE80 material DN110 electric fusion joint is example, and the characteristic curve and the distance wiry that record normal welding electric fusion joint with supersonic testing method are 3.7mm; And be 2.2mm with characteristic curve and the distance wiry that supersonic testing method records electric fusion joint to be measured; H=2.2/3.7=56.8% as can be known, decidable is defective.

Embodiment 3: with PE80 material DN63 electric fusion joint is example, and the characteristic curve and the distance wiry that record normal welding electric fusion joint with supersonic testing method are 2.4mm; And be 2.0mm with characteristic curve and the distance wiry that supersonic testing method records electric fusion joint to be measured; H=2.0/2.4=83.3% as can be known, decidable is qualified.

Embodiment 4: the PPR material DN63 electric fusion joint with material production in the Zhejiang is an example, and the characteristic curve and the distance wiry that record normal welding electric fusion joint with supersonic testing method are 2.3mm; And be 1.6mm with characteristic curve and the distance wiry that supersonic testing method records electric fusion joint to be measured; H=1.6/2.3=69.6% as can be known, decidable is defective.

The relation of input time and power when table 1 characteristic curve and distance wiry and electric smelting welding

Specification	Characteristic curve and distance wiry	Time	Characteristic curve and distance wiry	Power
					PE80 DN63	1.0mm	40％T	0.9mm	40％P
1.3mm	50％T	1.2mm	50％P
				1.5mm		60％T	1.5mm	60％P
2.0mm	80％T	2.0mm	80％P
				2.4mm		100％T	2.4mm	100％P
PE80 DN90	1.2mm	40％T	1.1mm						40％P
				1.6mm	50％T	1.5mm	50％P
	1.9mm	60％T	1.8mm					60％P
				2.6mm	80％T	2.6mm	80％P
	3.2mm	100％T	3.2mm					100％P
				PE80 DN110	1.3mm	50％T	1.2mm		50％P
1.8mm	50％T	1.7mm	50％P
					2.2mm	60％T	2.1mm	60％P
3.0mm	80％T	3.0mm	80％P
					3.7mm	100％T	3.7mm	100％P

The comparing result of the welding heat of table 2 cold welding degree and actual input

PE80 DN63	Cold welding degree (%)	41.7	37.5	54.2	50	62.5	62.5	83.3	83.3
										Welding heat (%)	40	40	50	50	60	60	80	80
	Error (%)	1.7	-2.5	4.2	0	2.5	2.5	3.3	3.3
										PE80 DN90	Cold welding degree (%)	37.5	34.4	50	46.9	59.4	56.3	81.3	81.3
Welding heat (%)	40	40	50	50	60	60	80	80
									Error (%)		-2.5	-5.6	0	-3.1	-0.6	-3.7	1.3	1.3
PE80 DN110	Cold welding degree (%)	35.1	32.4	48.6	45.9	59.5	56.8	81.1											81.1
									Welding heat (%)	40	40	50	50	60	60	80	80
	Error (%)	-4.9	-7.6	-1.4	-4.1	-0.5	-3.2	1.1										1.1

Claims (3)

1, the supersonic detection method of polyolefin pipe electrofusion welding joint cold welding defect, realize by the following method:

One, utilizes supersonic detection method to the detecting of a certain cross section of the tubing of normal welding and joint welding portion, obtain the ultrasonic reflection signal image, record characteristic curve and distance L wiry in this ultrasonic reflection signal image;

Two, electric fusion joint to be measured is carried out Ultrasonic Detection equally, obtains the ultrasonic reflection signal image in a certain care cross section, record characteristic curve in this ultrasonic reflection signal image and distance L wiry ';

Three, judge according to the distance of the characteristic curve in above-mentioned two images distance wiry whether this electric fusion joint to be measured exists the cold welding defective.

2, the supersonic detection method of polyolefin pipe electrofusion welding joint cold welding defect according to claim 1 is characterized in that described L and L '

The substitution formula: $H=\frac{L^{\′}}{L}$

In the formula: H represents with number percent, characterizes the cold welding degree of sample to be tested, thereby judges whether this welding joint exists the cold welding defective.

3, the supersonic detection method of polyolefin pipe electrofusion welding joint cold welding defect according to claim 1 and 2, it is characterized in that characteristic curve in the described ultrasonic reflection signal image and distance L wiry ' or the L available software record.

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