GOST R 55142-2012

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  ГОСТ Р 55142-2012

GOST R 55142−2012 Testing of welded joints of plates and pipes made of thermoplastics. Test methods

GOST P 55142−2012

NATIONAL STANDARD OF THE RUSSIAN FEDERATION

TESTING OF WELDED JOINTS OF PLATES AND PIPES MADE OF THERMOPLASTICS

Test methods

Testing of welded joints of thermoplastic sheets and pipes. Test methods

OKS 25.160.40

Date of introduction 2014−01−01

Preface

1 DEVELOPED by the Federal state Autonomous institution «Scientific-educational center «welding and control» at MGTU im.N. Uh. Bauman (FGAU NUCS computer.N. Uh. Bauman), the National Agency for control of welding (NAKS), OOO «Group POLYPLASTIC"

2 SUBMITTED by the Technical Committee for standardization TC 364 «welding and allied processes"

3 APPROVED AND put INTO EFFECT by the Federal Agency for technical regulation and Metrology, dated 22 November 2012 N 1008-St

4 In this standard are implemented the main provisions of the standards of the German Union for welding and related technologies* (ice 2203−1, 2, 3, 4, 5, 6 «Testing of welded joints of plates and pipes made of thermoplastics. Test methods — Requirements» (DVS 2203−1,2,3,4,5,6 «von an Tafeln und Rohren aus thermoplastischen Kunststoffen  — Anforderungen»)
________________
* Access to international and foreign documents referred to here and hereinafter, can be obtained by clicking on the link to the site shop.cntd.ru. — Note the manufacturer’s database.

5 INTRODUCED FOR THE FIRST TIME


Application rules of this standard are established in GOST R 1.0−2012 (section 8). Information about the changes to this standard is published in the annual (as of January 1 of the current year) reference index «National standards» and the official text changes and amendments — in monthly information index «National standards». In case of revision (replacement) or cancellation of this standard a notification will be published in the upcoming issue of the monthly information index «National standards». Relevant information, notification and lyrics are also posted in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet (www.gost.ru)

Introduction

The development of a national standard was carried out in order to create a modern national regulatory framework in the field of welding of polymeric materials. Its introduction will allow to increase the competitiveness of domestic equipment, compatibility and interchangeability of products, processes and services, to increase the level of harmonization of the domestic regulatory framework with international and regional standards.

1 Scope

This standard establishes General principles for the assessment of quality of weld joints of plastic sheets and pipes.

Guidelines for testing of welded joints of the required processor of semi-finished products and billets of thermoplastic and consumer products. The welding procedure must comply with international, national regulations or industry guidance documents.

The standard covers materials and components, welding procedures, equipment and evaluation of the quality of welded joints. It can be used in conjunction with the relevant national regulations and standards.

The dimensions of the welded workpieces and the test specimens are given in the relevant parts. If the dimensions of the welded materials and test specimens beyond the scope of this standard, the requirements for welded joints should be determined by special studies.

2 Normative references

This standard uses the regulatory references to the following standards:

GOST 166 (ISO 3599−76) Calipers. Specifications

GOST 4648 Plastic. Testing method on the statistical curve

GOST 11262 Plastic. Test method tensile

GOST 12423 Plastic. Conditions conditioning and testing of specimens (samples)

GOST 14782 nondestructive testing. Welded connections. Ultrasonic methods

GOST 18197 (ISO 899−1:2003) Plastics. Method of definition of creep in tension

GOST 18599 pressure Pipes made of polyethylene. Specifications

GOST 24157 Pipe of plastics. A method of determining the resistance at constant internal pressure

GOST 26277 Plastic. General requirements for the production of samples, method of machining

GOST R 50838 (ISO 4437:2007) polyethylene Pipes for gas pipelines. Specifications

GOST R 51613 pressure Pipes of unplasticized polyvinyl chloride. Specifications

GOST R 52134 pressure Pipes from thermoplastic materials and connection parts for water supply and heating. General specifications

GOST R 52779−2007 (ISO 8085−2:2001, ISO 8085−3:2001) Details the coupling of polyethylene for gas pipelines. General specifications

GOST R 54792 Defects in welded joints of thermoplastics. Description and evaluation

Note — When using this standard appropriate to test the effect of reference standards in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet or published in the annual information index «National standards» published as on January 1 of the current year, and the editions of the monthly information index «National standards» for the current year. If you replaced the reference standard, which was given an undated reference, then it is recommended to use the current version of this standard, taking into account all enabled in this version modifications. If replaced with a reference standard, which is given a dated reference, it is recommended to use the version of this standard referred to above by year of approval (acceptance). If after approval of this standard in the reference standard, which is given a dated reference, a change affecting a provision to which reference, the provision is recommended to be applied without taking into account this change. If the reference standard is cancelled without replacement, the position in which reference is made to him, recommended to be used in part not affecting this link.

3 General requirements

3.1 Scope

The choice of test methods is made according to production technology and operating conditions. It is necessary to pay attention to the fact that the test results depend on the conditions of manufacture of test specimens and the test conditions. The test results shall confirm compliance with the estimated properties of welded joints the actual loads encountered in operation.

3.2 Materials and properties

This standard covers the materials listed in table 1 used in the manufacture of pipes, fittings and sheets.


Table 1 — Materials and reduce

Plastics have specific properties from the point of view of technical application and processing. In the application of semi-finished thermoplastics, primarily for load-bearing elements should take into account the specific properties of plastics, especially with simultaneous mechanical, thermal loading and effects of chemical factors.

Properties of workpieces (pipes, sheets, profiles, fittings) with the appropriate test methods specified in GOST R 50838, GOST 18599, 51613 GOST R, GOST R 52134, GOST R 52779, [1], etc. Technical parameters of blanks and given in the relevant international standards.

3.3 Test

For evaluation of weld quality using different methods. When choosing a method consider the requirements for welded joints or intended results and available opportunities.

In practice it is assumed that, for testing of welded joints obtained by using filler materials, it is necessary to test the weldability of base and filler materials.

Blanks, used for welding of connections shall conform to the requirements of GOST 11262 and [2].

Testing should be guided by the requirements of GOST 11262, [1], [3]. Determination of defects is carried out in accordance with the requirements of GOST R 54792 [1].

Requirements to welded joints is set out in the relevant sections of this standard. The required values are the minimum values.

3.3.1 nondestructive Testing of the sample

Non-destructive testing methods of samples, such as control dimensions, visual inspection, leak test, verification through ultrasound, and fluoroscopy, as described in the relevant normative documents (GOST R 52134, GOST 14782, [1], [3], [4] etc.) and can be used accordingly.

To check the welded joints obtained by welding heated tool butt, it is recommended that non-destructive visual measurement control, and large-sized units of pipes and fittings, and piping leak test internal pressure according to current industry standards.

3.3.2 the destructive Test sample

Scope of test methods, test procedure, evaluation of the results is given in appropriate sections of this standard. Test methods are given in table 2.


Table 2 — test Methods

4 Testing of welded joints in axial tension

Test on axial tension can be used to assess the quality of welded joints of thermoplastic materials in combination with other tests. Samples of welded joints shall be tested at the same speed, stretching, and samples of the parent material.

Nature of fracture at fracture gives information about the ability of welded joints to plastic deformation and, thus, the quality of welding.

The results of short-term tensile tests do not apply to long-term properties of welded structure.

4.1 equipment and fixtures

The test is carried out on the machine (figure 1), which, when the tensile specimen must be capable of measuring loads with an accuracy of less than 1% of the measured value, a constant speed of sliding of the clamps to the extent required by this standard (table 4). The machine must be equipped with means for recording the applied force and a device for detecting failure of the sample.

Figure 1 — Scheme of tests on a tensile testing machine

1 — clamp; 2 — the test fixture; 3 — sample

Figure 1 — Scheme of tests on a tensile testing machine

4.2 the Selection and number of test specimens, type and form

The tensile test is conducted on the basis of GOST 11262.

Tested samples welded and reference samples of the same product without a welded joint.

Test specimens shall not be subjected to any thermal or mechanical stress.

In the manufacture of the axis of the specimen shall be parallel to the axis of the pipe. The weld seam should be located in the middle of the sample with an accuracy of ±1 mm. Samples-the blades must have a smooth flat surface, no blisters, chips, cracks, cavities and other visible defects. The scheme of manufacturing of samples of the blades is shown in figure 2.

Figure 2 — Scheme of cutting specimens from the weld joint to test the axial tension

1 — a branch pipe with a welded joint; 2 — the location of the samples

Figure 2 — Scheme of cutting specimens from the weld joint to test the axial tension

For the manufacture of the test sample cut out from the weld joint strip in the longitudinal direction, of which the mechanical treatment according to GOST 26277 produce the samples corresponding to the sizes:

a) type 1 corresponds to samples of type 2 according to GOST 11262 — for pipes with wall thickness of 10 mm (type 1);

b) type 2 — meets table 3 and figure 3 — for pipes with wall thickness of 25 mm;

C) type 3 corresponds to table 3 and figure 4 for pipes with wall thickness of 25 mm.


Table 3 — Dimensions of test specimens

Figure 3 — test sample, type 2

Figure 3 — test sample, type 2

Figure 4 — test sample, type 3

Figure 4 — test sample, type 3

Should be collected at least six samples of welded joints and six reference samples from the original product. If possible, the samples should be selected accordingly, the size of the welded products. For pipes with diameter 63 mm number of samples can be reduced to four.

Each sample for testing should be marked to establish its original position within the control welded joints.

Not allowed to apply a sample marking for scratching, punching, embossing or other method of damaging the test material. Apply marking liquid should also not have a detrimental impact on the test sample.

Before the test, you should visually assess the appearance of test specimens, especially the execution of the weld and record the test Protocol. Formed when welding burrs are allowed to remove.

Note — For more information about the quality of the weld is allowed to weaken the sample in place of the weld by drilling a hole with a diameter of, e.g. 3 mm but not exceeding 1/3 of the width of the specimen. This is a special test is recommended when the test is not achieved in the gap region of the weld. For the evaluation tests should be conducted with holes on the matching reference samples of products from which was obtained welded joint.

4.3 preparation for the test

4.3.1 test Speed

The rate of stretching of samples for selected materials are given in table 4.

If necessary, the speed of the tension for other materials are selected during the preliminary test so that the yield strength of the reference nesvarenie sample was achieved for 1 min, and then choose the closest standard speed according to GOST 11262.


Table 4 — Speed testing for certain plastics

If you use a different speed, there must be a correlation between the data obtained in applied and installed speeds. In case of disagreement is used the set speed.

4.4 testing

Before the test, each test sample conditionerit not less than 4 h according to GOST 12423 at a temperature of (23±2)°C and relative humidity of (50±5)% in the normative-technical documentation on the material otherwise.

The test is carried out not earlier than 24 hours after the welding. Each test sample should be marked so that its original position in the product under test can be determined.

Measure the width and minimum wall thickness at the Central part of the specimen between the test marks to the nearest 0.01 mm. calculate the minimum cross-sectional area.

Set the sample in the test machine (see figure 1) so that the axis of the sample coincided with the direction of application of tensile load. Tighten the clamps evenly so as to prevent slippage of the sample during the test.

Set the speed of testing for a specific value and bring the car in motion.

Record the curve of the stress/elongation until rupture of the sample and note on the curve the load at yield and the estimated length at break or directly write the load value at the moment of reaching the yield limit and the estimated length of the specimen at break.

The samples slipped from the clamps during the test, was destroyed in one of the heads or deformed so that it has led to a change in its width, is replaced by another in the same amount and test again.

Determine the type of failure — brittle or plastic.

Brittle fracture in the fracture zone are not detected by the deformation yield strength, visible without magnifying instruments. Plastic destruction — outside the zone of destruction is a deformation of the flow, visible without magnifying instruments.

4.5 data Processing

The test result is considered positive if:

— there is no destruction of the weld;

— the destruction has occurred on the part or welded pipe;

— type of fracture on the weld — plastic.

For a negative test result accept brittle fracture on the weld.

4.6 test Report

The test report must indicate:

— the form, the form of delivery and the designation of the product;

— the date and method of manufacturing the test specimens;

— appearance of test specimens before testing;

— bead appearance;

— scratches or grooves, if any;

the position of test specimens in a workpiece;

— form of test specimens;

— the thickness of test specimens, mm;

— the width of test specimens, mm;

— number of test specimens;

climatic conditions in which to test if they differ from the above norms;

visual assessment of the character of the fracture;

— the date of testing, location of test, name conducting the test.

For samples with hole weakening a separate Protocol

5 testing of the welded joints on a long stretch

To evaluate the quality of welded joints in conjunction with other test results provides a valuable test for a long stretch in the creep regime. Especially important endurance test for connections that carry the load for a long time. Extensive experience of such tests has been accumulated for polyolefins, PE and PP (polyethylene and polypropylene). For PVC and PVDF are also available such experimental data.

Conclusion about the quality of the welded joint can be given on the value of the coefficient of long-term strength of the weld and fracture properties. The results can be used to calculate parameters of welded structures under static load.

As comparative tests, it is allowed to apply the method specified in Annex G

5.1 fittings and fixtures

Creep testing in tension is carried out according to GOST 18197. This requires a stand where the samples are subjected to static load at constant temperature.

Stand schematically presented in figure 5. The stand must provide a constant application of force to the sample and a stable temperature of the sample. Depending on the test environment, as a rule, the necessary circulation of the coolant in the tub. For registration of the duration of the test samples and, if necessary, to register the elongation of the samples should provide a suitable device.

Figure 5 — test Bench for testing creep tensile

Figure 5 — test Bench for testing creep tensile

5.2 Selection and number of control samples, type and form

The shape and dimensions of samples are given in table 3 and GOST 11262.

Testing of welded joints carried out with or without a Burr at the weld. The connection must be in the middle of the test sample.

Before the test, you should evaluate the appearance of the test sample. On the surface of the samples shall be free of scratches. If necessary, the surface of the samples being finalized in the longitudinal direction. When testing the thermal impact on the sample is not allowed. Comparing the basic material and welded joint, it is necessary to test six specimens, oriented in the same direction.

5.3 testing

Before the test, each test sample conditionerit not less than 4 h according to GOST 12423 at a temperature of (23±2)°C and relative humidity of (50±5)% in the normative-technical documentation on the material otherwise.

5.4 test Conditions

The test conditions depend on the material and operating conditions of the product. Creep testing in tension is carried out in a water bath at elevated temperatures and relevant environments, accelerating the destruction. Use mediums that do not cause swelling and does not change the material chemically.

Applied environments test on a long stretch is a solution of surface-active substances (surfactants) in distilled water. As surfactants can be used OP-7 or OP-10 as a 2% solution. This surfactant has accumulated a large amount of experimental data that allows to compare results and establish requirements. In addition, you should consider the possibility of using other surfactants, including Russian production.

Load testing is selected so that the fracture pattern of the specimen was brittle. The force is calculated from the minimum cross section of the sample. Test conditions when using the above test environment are shown in table 5. When these conditions are achieved the shortest time of testing.


Table 5 — Recommended voltage and temperature test in which the observed brittle fracture of the samples in a two percent aqueous solution of a surfactant (OP-7 or OP-10)

5.5 Mode

Creep testing in tension was carried out at different temperatures and different loads depending on the material. Test time and voltage must be selected for each material as described in 5.6.

The specimens are loaded at constant temperatures ±1°C and with the same effort ±1%, and constant environmental conditions. A constant concentration of the surfactant [e.g., OP-7 or OP-10 (2±0,5)%] should be guaranteed. At loading, the sample should not be twisting and bending moments. Upon reaching the desired temperature, the samples are placed into the tub for testing. They need to load quickly and without jolts. The necessary tension force must be constant for the entire duration of the test (creep regime). The duration of action of the load begins when efforts and achievements are recorded using instruments.

Load value is selected so that the nature of the fracture was brittle: that is, the deformation should be minimal and at least 30% of the area of destruction should appear smooth (figure 6). If this is not achieved, it is recommended to choose lower values of load. The destruction in the area of the clamps of the test sample estimate.

Figure 6 — View of fractured surfaces of HDPE welded by extrusion welding

a — area of the failure surface that has undergone brittle fracture (not less than 30%);

b — area of the failure surface that has undergone plastic destruction

Figure 6 — View of fractured surfaces of HDPE welded by extrusion welding

To determine the slope of the time curve of destruction in the double logarithmic coordinate, conduct tests at least at two values of the load. For each voltage experience a minimum of six welded and reference samples. The value of time to failure is calculated as the geometric mean.

5.6 processing of the results

For the determination of the strength of the weld with long-term tension in the creep regime is required to obtain the dependence of time to failure of welded samples and a reference voltage, and especially important is the slope of the straight lines. The regression curves must be calculated from the geometric averages of the durability of t for individual samples.

.

Using graphs similar to figure 7, the ratio of long-term strength of the weld in tension shall be calculated as the ratio of stress in the welded connections to the voltage in the reference specimens without weld at the same time destruction.

.

Constructing regression curves for base material and welded joints, it is possible to determine the ratio of long-term strength of the weld in tension under all load levels.

Figure 8 shows an alternative method of defining . In this case, you have a regression curve for welded joints and one mean value of failure times for the reference model. The resulting factor can be used only with the reference voltage in the reference sample.

Figure 7 — Scheme of determining the ratio of the strength of the weld f (s) with long-term tests of creep in tension

In a reference sample;

S — the sample under test;

Figure 7 — Scheme of determining the ratio of the strength of the weld with long-term testing creep tensile

Along with the above techniques allowed to apply the simplified testing method to confirm the required strength factor weld with prolonged stretching. The last method uses the regression curves and is used to reduce test time and number of test specimens. The calculation is limited to the testing of basic material (reference sample) at one voltage level (figure 9), and is calculated by multiplying the per capita ratio of long-term strength of weld in tension .

Figure 8 — Scheme of determining the ratio of the strength of the weld f (s) with long-term tests of creep in tension with a test voltage of the reference model

S — the sample under test;

and

In a reference sample;

Figure 8 — Scheme of determining the ratio of the strength of the weld with long-term tests on creep in tension with a test voltage of the reference model

Figure 9 — Simplified method of confirming the desired ratio of the weld when tested in creep under tension

S — the sample under test;

In the reference sample

Figure 9 — Simplified method of confirming the desired ratio of the weld when tested in creep under tension

For example:

— the test voltage for main material (the reference sample) to 4 N/mm;

— the test voltage for the weld samples, for example, if ratio =0.8, and is calculated by the formula

H/mm=3,2 H/mm.

Welded samples should have less durability than the main material. In this test it is impossible to judge the dependence of the strength of the connection from the load. Applicability in practice by the simplified method is confirmed by conformity of the minimum resistance of the basic material to the established norms (table 6).


Table 6 — Minimum resistance of the basic material with prolonged stretching. Test environment: two percent aqueous solution of surfactant (OP-7 or OP-10)

5.7 test Report

The report should indicate:

— the form, the form of delivery and the designation of the product;

— the date and method of manufacturing the test sample;

— appearance of the specimen before testing, a visual assessment of welding;

— position the test sample in the product;

— shape test sample;

— the thickness of test specimen, mm (average);

the width of the test specimen, mm (average);

— number of test specimens;

— pre-processing the test sample (e.g., with a welded bead or without);

— test temperature;

— test environment;

— test force or stress;

— duration of the test to failure;

— the ratio of long-term strength of the weld in tension , indicating the voltage values of the reference sample;

— change of length after the break, if it was measured;

— appearance of the sample after the test, visual assessment of the nature of the destruction;

— the date of the test.

6 Technological bend test

6.1 Scope

Technological bend test in conjunction with other samples characterizes the quality of the weld in the joints of the sheets. In accordance with this standard can also be tested welded joints other products, for instance pipes and profiled parts.

At the achieved bend angles reveals the deformability of welded joints. Together with the assessment of the type of fracture and assesses the quality of a welded joint. The ability of a material to deformation, the applied welding method, geometry of the sample will affect the achieved bending angle and the type of fracture and must be taken into account in the assessment of the quality of the weld. The results achieved in the process of bending test, but only conditionally applicable to the fatigue behavior of the welded structure.

The bend test can be used to find the optimal welding parameters. In order to best differentiation is allowed, if necessary, to change test conditions, such as temperature or speed test.

6.2 Methodology and scheme of loading

Technological bending test shall be conducted in accordance with GOST 4648. Welds subjected to bending test not earlier than 8 h after completion of welding. Heat treatment of test specimens is not allowed.

Figure 10 shows the experimental setup.

Figure 10 — Scheme of loading

S — sample thickness; the bending angle; and — the thickness of the plug end has the shape of a semicircle; is the distance between the axes of the rollers

Figure 10 — Scheme of loading

Table 7 presents the parameters of the experimental setup and the samples. The specified thickness of the samples and a predetermined value for width refer to the nominal size of the workpieces.


Table 7 — Dimensions of the experimental setup and samples

For samples with thickness more than 30 mm recommended sample handling with one hand (pipe — outer side) to a thickness of 30 mm. When handling pipe, including chamfering, account should be taken of the maximum thickness at the edges of the samples.

With this method of testing the bending punch set on the treated side of the sample. For samples with thickness more than 30 mm, which should be tested without processing, is determined by the estimated span according to the formula

,

where D=50 mm a=25 mm S=thickness of the sample.

The punch and the rolls needs to be wider than the sample. The punch set in the middle of the weld. To reduce the displacement of the samples at the time of the test, the grooved bending punch or sandpaper, placed in the place of focus punch.

When testing weld samples welded joints are evenly distributed around the perimeter of the pipe. Samples are cut as shown in figure 11, in the radial direction, or they must have parallel sides.

Figure 11 — Methods of cutting samples from the pipe

Figure 11 — Methods of cutting samples from the pipe

In the latter case, the width of the sample represents the average value between the largest and smallest width.

In the contact area of the punch, the Burr needs to be removed. On the reverse side of the sample in the grat is retained. At the longitudinal edges of the sides exposed to tensile stresses, should be withdrawn 1 mm chamfer at 45°. The chamfer is removed also in the seam area.

6.3 Preparation for testing

6.3.1 hardware Requirements

The moment of contact of the sample surface with a punch needs to be fixed. The destruction or the formation of cracks in the sample, the measurement must be stopped manually or automatically. The result should be reported and recorded.

6.3.2 angle Measurement

The accuracy of measurements and readings shall be ±1°. Therefore, it is necessary that the equipment had electronic or mechanical meter with sufficient accuracy of the countdown.

The point of contact of the sample with rollers of the supports during the test, constantly shifting. It is necessary to take into account using a correction factor or a specially calibrated measuring scale.

6.3.3 Measurement of displacement

Measurement accuracy and sensor of movement of the punch shall be not less than 0.1 mm.

6.4 testing

Before the test, each test sample conditionerit not less than 4 h according to GOST 12423 at a temperature of (23±2)°C and relative humidity of (50±5)% in the normative-technical documentation on the material otherwise.

The test shall be performed on at least six samples. For pipes subjected to tension inside.

The strain rate is presented in table 8.


Table 8 — Rate of deformation for some polymer materials

6.4.1 analysis of the results

Technological bend test gives values of the design variables for the design of structures made of thermoplastics. However the bend test allows the specialist to assess the quality of welded joints according to their deformation properties.

The technological bending test can be estimated in two ways: by the bending angle or the displacement of the punch, which are the independent variables.

6.4.1.1 determination of the bending angle

The bend angle is determined as the difference between the bend angle at failure (or cracking) and an initial angle connection pieces. Angle measurement is performed on both sides of the sample outside of the rollers. The bending angle is determined by summing these two quantities, with a possible deviation of the angle to the horizontal prior to the test must be established and taken into account (figure 12).

The bursting of the samples without fracture and cracking is regarded as a «nondestructive», and when determining the average value of the accepted angle of 160°.

Figure 12 — Schematic representation of the process of determining the bending angle and the movement of the punch

The position of the samples before test

The bending angle , the displacement of the punch

The bending angle , the displacement of the punch

The position of the samples at the end of the test

Figure 12 — Schematic representation of the process of determining the bending angle and the movement of the punch

6.4.1.2 determination of the movement of the punch

The path, which passes the punch from the position of its installation on the sample before the formation of cracks or fracture. The bursting of the samples without fracture and cracking is regarded as a «nondestructive», and when determining the average values is accepted according to the movement of the table 9.


Table 9 — Taken in the calculations (when determining average values) the amount of movement of the punch f in the cases where fracture and cracking does not occur, and the bending angle is taken 160°

6.4.1.3 Evaluation of test results

For the final assessment takes into account the results of testing each sample individually. The values of parameters f and for each sample must be equal to or greater than the minimum values given in Appendix b, which is a sign of positive test results. If one or two samples do not meet the standards, the test is repeated on two additional samples of the same compound. Additional samples shall meet the requirements, otherwise the test results are recognized as negative.

Paragraph 6.4.1.4. Use of average values when optimizing the welding procedure

In such cases, as studies to optimize the welding technology, it is recommended to use the arithmetic means of the parameters f and calculated without taking into account the results of testing additional samples.

6.4.2 failure Criteria

The samples can be destroyed by a sudden rupture or formation of continuously growing cracks.

When cracking has occurred or the appearance of cracks detected visually with the naked eye, are determined by the measured values of f and . The start of the crack has a depth of about 0.5 mm. To detect cracks in the critical area should be well illuminated and observed, for example, with the use of mirrors.

6.5 test Report

The test report must contain the following information:

— the material delivery type, purpose of the product;

date and method of welding connection;

the orientation of the test sample in the product;

profile of the test sample (radial or parallel cut);

— nominal thickness of test specimen, mm;

— the width of the test specimen, mm;

— the number of test specimens;

— the temperature conditions in the room during testing;

— deformation rate, mm/min;

— the bending angle and displacement of the punch;

— the view of destruction, the development of cracks (if required);

— the date of the test.

7 determination of the resistance to separation saddle taps with embedded heaters

7.1 Scope

Saddle branch, welded polyethylene pipe is subjected to the pull test of the pipe under tension and determine the fracture properties according to GOST R 52779. The required values are the minimum values.

7.2 fittings and fixtures

For the test it is possible to use testing machines, compression type IP 6010−100−1 with the highest maximum load of 100 kN at speeds of sliding clamps (25±2) mm/min Testing machine shall be equipped with a tooling made according to the drawings approved in the prescribed manner, and ensuring the application of the load on one of the two schemes (figure 13).

Figure 13 — scheme of test saddle plastic taps at the gap

a — tensile; b — compression

Figure 13 — scheme of test saddle plastic taps at the gap

7.3 the Selection and number of test specimens, type and form

The specimen is a welded joint saddle of branch conduits heaters with plastic pipe a length equal to its length. Welding of the samples is carried out according to the manufacturer’s instructions.

Inside plastic pipe test sample to be transmitted, you must enter a metal core with an outer diameter corresponding to the internal diameter of testing pipes (table 10).


Table 10 — dimensions of the core diameter

7.4 preparing for the test

Before the test, each test sample conditionerit not less than 4 h according to GOST 12423 at a temperature of (23±2)°C and relative humidity of (50±5)% in the normative-technical documentation on the material otherwise.

The test is performed no earlier than 24 hours after the welding.

7.5 testing

The test sample is fixed in the clamping device (see figure 13), set in a testing machine and loaded at a speed of (25±2) mm/min until complete separation from the polyethylene pipe or deformation of the parts of the joint and lowering the test load to zero. Then determine the type of fracture: brittle or plastic.

7.6 processing of the results

The test result is considered positive if:

— there is no destruction of the weld;

— the type of plastic destruction across the surface of the gap, allowed local areas of brittle fracture.

For a negative test result accept brittle fracture across the surface of separation.

8 determination of the resistance to impact saddle of the T-shaped taps when welding with embedded heaters

8.1 Scope

The method consists in application of the impact load falling from a constant height, the saddle cover of the T-shaped drainage conduits heaters, welded to the pipe. Test for leaks, appreciate the destruction and the tightness according to GOST R 52779.

8.2 fittings and fixtures

Koper vertical guides which allow the striker to fall vertically and freely with speed at the moment of impact on allocation not less than 95% of the set value. Striker (cylindrical shape) with a spherical tip with a diameter of 50 mm, weight of the striker — (2500±20) g.

The sample holder, which is a rigidly fixed steel core capable of holding the test sample in the position shown in figure 14, to prevent rotation of the sample during the test.

Figure 14 — Sample of the test compound

1 — steel core; 2 — tube; 3 — cover removal; ; ; R — target

Figure 14 — Sample of the test compound

8.3 Selection and number of test specimens, type and form

The specimen is a welded joint saddle of branch conduits heaters with plastic pipe the length of the free ends of the L, approximately equal to the nominal diameter of the pipe . Welding of the samples is carried out according to the manufacturer’s instructions.

8.4 preparing for the test

The impact test carried out not less than 24 hours after the welding test sample.

Before the impact test samples conditionyou at a temperature of (0±2)°C for at least 4 h in air or not less than 2 h in liquid medium.

8.5 testing

Set the specimen onto the steel core of the appropriate size, as shown in figure 14. The test is carried out for not more than 30 s after removing the test specimen from the conditioned environment. If this time is exceeded, the test sample is subjected to repeated aged for at least 5 minutes, if he was outside the conditioned environment no more than 3 min.

Strike the striker on the lid with a height of (2000±10) mm along the axis parallel to the axis of the pipe, which is welded to the saddle branch. The point of impact should be located at the cylindrical part of the cap in the middle.

Turn the sample to strike at the opposite side of the cover.

After the first strike the specimen unfold to 180° so that the next blow to strike from the opposite side. After applying two strokes of the specimen is visually inspected for any obvious damage without the use of magnifying devices.

After the impact test samples were subjected to the leakproofness test at air pressure of 0.25·10MPa (25 mbar) and temperature (23±2)°C. the Equipment used for testing for leaks, shall comply with the GOST 24157.

Installation for leak testing consists of a source pressure, valve, pressure gauge, baths.

The test specimen is connected to a pressure source, immersed in a bath of water, serves test pressure air from the pressure source through a check valve, blocking it at the moment of reaching the test pressure and allowed to stand for at least 15 minutes.

The tightness is determined by pressure drop or by gas bubbles emerging from the test sample.

8.6 the Processing of the results

For a positive test result accept the absence of cracks and fracture during impact test and the preservation of integrity after the impact test.

For a negative test result accept cracks and damage during the impact test and the leakage in the leak test.

9 determination of the resistance to separation when flattening parts with the belled end welding with embedded heaters

9.1 Scope

The sample in the form of a sector of the socket details pre-welded to the pipe and cut along the axis, is subjected to test for the flattening between the plates. Determine the type of fracture and the percentage of the break (brittle fracture).

9.2 fittings and fixtures

Testing machine, equipped with plates, providing a constant compression rate (100±10) mm/min in agreement with the customer allowed the testing of joints of pipes with diameter up to 63 mm inclusive to carry out locksmith vise a smooth deformation of the specimen.

9.3 Selection and number of test specimens, type and form

The specimen represents a sector cut along the axis of the welded connection detail with two lengths of pipe, the shape and size of which must conform to table 11 and figure 15. The test is the two samples.


Table 11 — the Shape and size of samples

Figure 15 — Preparation of test specimens

Figure 15 — Preparation of test specimens

9.4 preparation for the test

Before testing, the samples conditionyou at least 2 h in standard atmosphere (23±2)°C according to GOST 12423, the test was conducted no earlier than 24 hours after the end of the weld connection, including the time of conditioning.

9.5 testing

The test specimen is set between the plates, as shown in figure 16, and realize the convergence of the plates at a speed of (100±10) mm/min until then, until the distance between them will not be reduced to twice the thickness of pipe wall due to its complete flattening.

Figure 16 — Location of the samples between the plates of the testing machine

1 — pipe; 2 — part; 3 — plate

Figure 16 — Location of the samples between the plates of the testing machine

When the load is removed the specimen is visually examined, determining the type of failure — brittle or plastic (see 2) — and the place of destruction, for example through the pipe, a part, between the turns or along the interface. In the presence of a separation is measured by Vernier caliper according to GOST 166расстояние between the first and last turns of the laying of the heater in the welding area, which is taken for the length of the seam and the length of the brittle fracture of the weld at. For convenience of measurements an additional sample cut with any cutting tool in longitudinal and transverse directions.

Resistance to separation when flattening , %, is calculated by the formula

,

where u is the length of the fragile detachment of the weld, mm;

 — weld length — distance between the first and last turns of the laying of the heater, mm.

9.6 processing of the results

The test result is considered positive if:

— there is no destruction of the weld;

— type of fracture — plastic over the entire surface;

— the length of the fragile margin is 33.3 per cent.

Annex a (informative). Test requirements for shear and delamination for welding with embedded heaters

Appendix A
(reference)

A. 1 Scope

This Annex sets out the requirements to share the impeccable surfaces of the weld, identified in tests on shear and delamination of pipe joints and fittings. Connections must be carried out a t & C welding with embedded heaters.

In combination with other tests these requirements may be applied as evaluation criteria of welded joints. Evaluation of welded joints in accordance with these technical requirements can only be performed by specially trained expert (specialist in the field of welding plastics).

These technical rules apply to the following materials: HDPE (PE 63, PE 80, PE 100).

The requirements of this Annex must comply with the standards for welding, alterations, and is consistent with the technical rules manufacturers.

A. 2 Requirements

A. 2.1 the Connections made by welding with embedded heaters (ZN)

In the evaluation of quality takes into account the following:

the assessment is based on the failure surface and the pipe and fitting;

— to assess the weld joint has the value of the area located between the first and last heating coils;

— in the saddle nodes can be evaluated only samples taken from the welding zone;

— defects in the plane of the weld (such as pores, foreign inclusions, displacement of the helix) must be described and evaluated in accordance with GOST R 54792, [1] and other similar Russian regulatory documents. In the case of welded joints with a diameter greater than 250 mm a large number of defects (pores and air pockets) may occur for physical reasons.

Requirements for joints made by welding with embedded heaters below.

For any sample, the proportion of perfect weld should not be less than 75% of the total length of the welding zone L. Impeccable length of a zone is calculated as the difference between the L and the total length of all defects (, ) in figure A. 1.

A. 2.2 Joints made by welding heated tool (S) in trumpet

In the evaluation of quality takes into account the following:

— appreciate the connections that are made by welding heated tool (S) socket in accordance with GOST R 54792;

the assessment is based on the failure surface and the pipe and fitting;

as the depth of introduction of the adopted length In drawing A. 2;

— defects (such as pores and foreign inclusions) shall be described and evaluated in accordance with GOST R 54792.

For any sample, the proportion of perfect weld should not be less than 90% of the total length of the welding zone In. Impeccable length of a zone is calculated as the difference between the In and the total length of all defects (, ) in figure A. 2.

Figure A. 1 is the length of the connection zone L and examples of defects for samples of compounds, the coupling is made by welding with embedded heaters (ZN)

Figure A. 1 is the length of the connection zone L and examples of defects for samples of compounds, the coupling is made by welding with embedded heaters (ZN)

Table A. 1 — Examples of destruction of samples of compounds, the coupling is made by welding with embedded heaters (ZN)

Figure A. 2 — Estimated length and examples of defects (a (1) and a (2)) in the case of samples which are made by welding heated tool (S) in trumpet

Figure A. 2 — Estimated length In and examples of defects (and ) in the case of samples which are made by welding heated tool (S) in trumpet

Table A. 2 — Examples of types of destruction of samples of joints made by welding heated tool

Annex B (reference). The torsion shear and radial peeling of joints made by welding with embedded heaters and heated tool into the socket

Appendix B
(reference)

B. 1 Scope

In combination with other tests of shear characterize the quality of welded joints made by welding with embedded heaters (ZN) and heated with tool (D) into the socket. Evaluation of fracture properties allows to draw conclusions regarding technology performance and weld quality. Test shear torsion manually, shear torsion, mechanized and radial delamination can also be used in place of welding.

The assessment should consider the characteristics of materials and their properties that affect welding quality and nature of fracture. PE (PE 63, 80 and 100) are typically used when welding with embedded heaters (ZN). Possible combinations of materials, such as PE pipes With fittings made of PE 100.

The results obtained from shear tests cannot be transferred to long properties of welded joints.

B. 2 Selection and number of test specimens, type and form

Sample preparation significantly affects the test results. To the test sample surface should remove all defects such as cracks and scratches. Trimmed surfaces must be parallel (figure B. 1).

Figure B. 1 — Specimens with parallel surfaces

b — specimen width; s — thickness of pipe wall; d is the tube diameter

The sample made socket fusion welding with embedded heaters

The sample made of the heated tool into the socket

Figure B. 1 — Specimens with parallel surfaces

Samples should be made no earlier than 12 hours after welding. In order to approximate the evaluation samples can be produced and tested immediately after welding. In this case, it is necessary to ensure cooling of the sample to the ambient temperature.

Figures B. 2 and B. 3 show how to take samples of joints made by welding with embedded heaters and heated tool into the socket. Samples should be cut evenly around the circumference. The size and number of samples indicated in table B. 1. In the case of saddle connections samples can be selected in accordance with figure B. 3.

Figure B. 2 — Positions (a to d) sampling connection made socket welding with embedded heaters (does not apply to sidelock)

Figure B. 2 — Positions (a to d) sampling connection made socket welding with embedded heaters (does not apply to sidelock)

Table B. 1 — Dimensions and the minimum number of samples of joints made socket fusion welding with embedded heaters

Figure B. 3 — samples (a to d) in the case of sidelock for testing shear with twisting: manually, mechanized method and radial delamination

Figure B. 3 — samples (a to d) in the case of sidelock for testing shear with twisting: manually, mechanized method and radial delamination

B. 3 test Methods

Samples can be made and tested at room temperature. In order to approximate the evaluation samples can be produced and tested at ambient temperature. In the evaluation process compounds it should be considered and documented.

B. 3.1 Shear-torsion

Shear torsion can be performed manually, and mechanization.

B. 3.1.1 Shear-torsion manually

For testing the specimen is clamped in the bench vise so that the surface of the weld was located outside, parallel to the jaws. The individual segments are located above the clips using a suitable tool without sharp edges rotate at least 90° in the plane of the connection (figure B. 4). The rotation speed should be uniform and very low (approximately 5−10 s 90°). This is done to reduce the influence of torsion speed on the fracture pattern. The surface of the clamps should be lightly machined (not more than 2°) with the goal of deployment of torsional moment in the plane of the connection.

Figure B. 4 — shift of the torsion manually

Figure B. 4 — shift of the torsion manually

Figure B. 5 — the Principle of installation for the mechanization of shear testing torsion

Figure B. 5 — the Principle of installation for the mechanization of shear testing torsion

B. 3.1.2 Shear and torsion, mechanical

Test shear torsion can be mechanized (figure B. 5). The test can be implemented by rotating the clamping angle of at least 90° at the rate of about 1° per second.

The clip must be designed so that samples were attached safely and securely. The center of rotation should coincide with the center of the heated surface for welding. If the length of the heated surface is greater than the length of the clips, samples can be tested in a truncated form. The distance between the clamps can be adjusted to different diameters. When testing, consider the differences between compounds and heated surfaces.

B. 3.2 Radial delamination (RPT)

For testing the specimen is clamped in the bench vise so that the surface of the weld was located outside the area of the clamps (figure B. 6). The individual segments are located above the clips using a suitable tool without sharp edges (e.g., tongs, pliers or pliers) peeled in the radial direction with a constant as possible velocity (about 2 to 90°). If necessary, the tool is used several times.

Figure B. 6 — Test on the radial delamination (RPT) for joints made by welding with embedded heaters (ZN) and heated tool (S) in trumpet

Figure B. 6 — Test on the radial delamination (RPT) for joints made by welding with embedded heaters (ZN) and heated tool (S) in trumpet

The surface of the clamps should be lightly machined (not more than 2°) for the purpose of deployment of torsional moment in the plane of the connection.

B. 4 Assessment

In the inspection process the appearance of failure surface should be assessed connection. In principle one should distinguish between the fragile (smooth) and plastic (strain) fracture surface (figures B. 7 and B. 8).

Figure B. 7 — Sample of PE with a plastic fracture surface

Figure B. 7 — Sample of PE with a plastic fracture surface

Figure B. 8 — Sample of PE with a smooth fracture surface

Figure B. 8 — Sample of PE with a smooth fracture surface

You should determine the percentage of the failure modes (excluding the zone spirals). Requirements are set in Annex A to this standard.

Defects (e.g., bubbles, shrinkage, foreign inclusions and displacement of the helices) are estimated in accordance with GOST R 54792 [1]. Typical failure surface of various materials is given in Appendix A to this standard.

B. 5 the test Report

The test report must include the following information:

type, form of delivery and identification of components;

— information about the date of weld, location of sample, organization by welding, welder, welding process and welding parameters (extract from the welding journal);

— the number and position of samples;

— sample sizes (wall thickness, length and width of the surface of the weld);

temperature and humidity during testing;

— evaluation of failure surface (determination of the percent of the failure modes without regard to the zone heating coils) and finally, the quality in accordance with Annex A to this standard;

— date of test, name and signature of tester.

B. 6 Example of test report

Annex b (informative). Technological bending test. The bending angle, the displacement of the punch

The App
(reference)

B. 1 Scope

This app is used in conjunction with part 6 of this standard. Evaluation of the welding quality can be determined by measuring the angle of bending or movement of the punch.

B. 2 Requirements

The minimum angle of deflection for HDPE, PP, PVC and PVDF depending on the thickness of material specified in figures B. 1-B. 6, and the minimum movement of the punch — in figures V. 7-V. 12.

Figure B. 1 — Minimum bending angle for HDPE (PE 63, PE 80, PE 100), depending on the thickness for different welding methods [upper curve — for welding heated tool butt (NO), lower rod for gas welding and extrusion welding (NG, e)]

Figure B. 1 — Minimum bending angle for HDPE (PE 63, PE 80, PE 100), depending on the thickness for different welding methods [upper curve — for welding heated tool butt (NO), lower rod for gas welding and extrusion welding (NG, e)]

Figure B. 2 — Minimum bending angle for PP-b, PP-R and PE conductive, depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for gas welding and extrusion welding)

Figure B. 2 — Minimum bending angle for PP-b, PP-R and PE conductive, depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for gas welding and extrusion welding)

Figure B. 3 — Minimum bending angle for PP-R (type 3) depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for gas welding and extrusion welding)

Figure B. 3 — Minimum bending angle for PP-R (type 3) depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for gas welding and extrusion welding)

Figure B. 4 — Minimum bend angle for PVDF depending on the thickness for different welding methods (the lower curve for welding heated tool butt top for welding rod heated by gas)

Figure B. 4 — Minimum bend angle for PVDF depending on the thickness for different welding methods (the lower curve for welding heated tool butt top for welding rod heated by gas)

Figure B. 5 — the Minimum bending angle for PVC depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure B. 5 — the Minimum bending angle for PVC depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure B. 6 — Minimum bend angle for WPVH depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure B. 6 — Minimum bend angle for WPVH depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure V. 7 — Minimal movement of the punch for HDPE depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure V. 7 — Minimal movement of the punch for HDPE depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure V. 8 — Minimum movement of the punch for PP-b, PP-R and PE conductive, depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and …

Figure V. 8 — Minimum movement of the punch for PP-b, PP-R and PE conductive, depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure V. 9 — a Minimum movement of the punch for PP-R (type 3) depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure V. 9 — a Minimum movement of the punch for PP-R (type 3) depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure B. 10 — Minimum displacement of the punch for PVDF depending on the thickness for different welding methods (the lower curve for welding heated tool butt top for welding rod heated by gas)

Figure B. 10 — Minimum displacement of the punch for PVDF depending on the thickness for different welding methods (the lower curve for welding heated tool butt top for welding rod heated by gas)

Figure V. 11 — Minimum displacement of the punch for PVC depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure V. 11 — Minimum displacement of the punch for PVC depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure V. 12 — a Minimum movement of the punch for WPVH depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Figure V. 12 — a Minimum movement of the punch for WPVH depending on the thickness for different welding methods (upper curve — for welding heated tool butt, and the lower rod for welding of heated gas and extrusion welding)

Appendix d (reference). Creep testing in tension. Determination of the resistance to slow growth of cracks in specimens with four-sided incision

Appendix D
(reference)

G. 1 Scope

This method is used to determine the resistance to slow growth cracking of the workpieces. Test results can be used as a comparative.

G. 2 Number and selection of samples

Statistical evaluation of the results requires testing at least 6 samples. However, the trend can be identified by testing a smaller number of samples due to the small scatter of test results.

G. 3 Form and preparation of samples

The shape and dimensions of samples are presented in figure G. 1.

Figure G. 1 — test Samples

 — sample thickness; b is sample width; with depth of cut — (17±2)% ; I — sample with a square cross-section; II — sample with non-square cross section (e.g. wall pipe). Preferably, if a =b

Figure G. 1 — test Samples

Typical samples have a nominal thickness of 10 mm and a total length of 100 mm.

Samples must be incised on all four sides in one plane. The depth of the notches must be the same on all four sides and range from 15% to 19% of the nominal thickness. Cuts made with a razor blade or other similar tool. Specimens incised at a temperature of (23±1)°C after conditioning for at least 24 h.

To obtain reproducible results after making 20 samples instrument for incision should be checked, for example, with a microscope.

G. 4 Test

The samples are installed in the jaws of the testing equipment so that approximately 50% of the length of the sample was located between the clamps, and snips found himself in the middle between the clamps. Samples immersed in the test environment.

Samples of 10 mm thickness shall be conditioned for 2 h±30 min before loading.

Test load () is calculated by the formula

,

where  — load, N;

And the incised cross — sectional area of the specimen, mm;

 — tensile stress, MPa.

G. 5 Assessment

The minimum proportion of brittle fracture should be 30% of the cross section of notched specimens. Otherwise, you need to lower the voltage.

For evaluation of calculated geometric means of the times of the destruction of the individual samples. This data is used for comparison.

G. 6 test Report

The report is the same 5.7 of this standard, except for ratio of long-term strength of the weld.

Bibliography