Iso Dtr 16943 Ndt Final Kil

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© ISO 2010 – All rights reserved

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ISO/TC 138/SC 5

Date: 2013-5-6

ISO/DTR16943

ISO/TC 138/SC 5/WG 17

Secretariat: NEN

Thermoplastic p ipes for the conveyance of flu ids – Inspection ofpolyethylene electrofusion jo ints using phase array ultrasonic method

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ISO/DTR 16943

ii © ISO 2010 – All rights reserved

Copyright notice

This ISO document is a working draft or committee draft and is copyright-protected by ISO. While thereproduction of working drafts or committee drafts in any form for use by participants in the ISO standardsdevelopment process is permitted without prior permission from ISO, neither this document nor any extractfrom it may be reproduced, stored or transmitted in any form for any other purpose without prior writtenpermission from ISO.

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ISO/DTR 16943

© ISO 2010 – All rights reserved iii

Contents Page

Foreword ............................................................................................................................................................ iv

Introduct ion ......................................................................................................................................................... v

1 Scope ...................................................................................................................................................... 1

2 Normative references ............................................................................................................................ 1

3 Terms and definit ions ........................................................................................................................... 2

4 General ................................................................................................................................................... 5

4.1 Purpose .................................................................................................................................................. 5

4.2 Use .......................................................................................................................................................... 5

5 Apparatus ............................................................................................................................................... 5

5.1 Ult rasonic imaging system ................................................................................................................... 5

5.2 Transducer ............................................................................................................................................. 5

5.3 Data display ........................................................................................................................................... 5

5.4 Couplant ................................................................................................................................................. 5

6 General Examination Requi rements .................................................................................................... 6

6.1 System Calibration ................................................................................................................................ 6

6.2 Sensit iv ity Sett ing ................................................................................................................................. 6

6.3 Examination Time .................................................................................................................................. 6

6.4. Examination Volume ............................................................................................................................. 7

7 Procedure ............................................................................................................................................... 7

7.1 System Setup ......................................................................................................................................... 7

7.2 Surface of specimen .............................................................................................................................. 7

7.3 Examination ........................................................................................................................................... 7

7.4 Measur ing of indication ........................................................................................................................ 8

8 Quality Assurance Provisions ............................................................................................................. 8

8.1 Personnel Quali fication ........................................................................................................................ 8

8.2 System Performance ............................................................................................................................. 8

9 Repor t ..................................................................................................................................................... 8

Annex A Examples of inspection images (Informative) ............................................................................... 10

Annex Example of a cal ibration block ....................................................................................................... 10



ISO/DTR 16943

iv © ISO 2010 – All rights reserved

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies(ISO member bodies). The work of preparing International Standards is normally carried out through ISOtechnical committees. Each member body interested in a subject for which a technical committee has beenestablished has the right to be represented on that committee. International organizations, governmental andnon-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with theInternational Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standardsadopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patentrights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO was prepared by Technical Committee ISO/TC 138, General properties of plastics pipes, fittings andvalves of plastics materials and their accessories, Subcommittee SC 5, Test methods and basic specifications.



ISO/DTR 16943

© ISO 2010 – All rights reserved v

Introduction

Non destructive testing methods of electrofusion (EF) joints of polyethylene pipes are required for fusion jointsafety and for the long term reliability of a pipe system. Electrofusion joints may encounter defects due todifferent reasons such as ovality between pipes and couplings, improper fusion processes or procedures.

The test procedures specified in this document are intended to describe the ultrasonic phased array method

of polyethylene electrofusion joints.



DRAFT TECHNICAL REPORT ISO/DTR16943

© ISO 2010 – All rights reserved 1

Thermoplastic p ipes for the conveyance of flu ids – Inspection ofpolyethylene electrofusion jo ints using phase array ultrasonic method

1 Scope

1.1 This document describes phased array ultrasonic testing of polyethylene electrofusion (EF) joints used forthe conveyance of fluids.

1.2 This document recommends a technique whereby the presence of voids, cracks, discontinuities, foreignparticles, etc., in the electrofusion joints can be detected.

Warning : Use of this method does not guarantee the electrofusion integrity and the user is liable for anyproblems that may occur during operation of the non-destructively tested joint

2 Normative references

The following referenced standards are indispensable for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of the referenceddocument(including any amendments) applies.

ISO 5577, Non-destructive testing - Ultrasonic inspection - Vocabulary

ISO 497, Guide to the choice of series of preferred numbers and of series containing more rounded values of

preferred numbers.

ISO 8085-2, Polyethylene fittings for use with polyethylene pipes for the supply of gaseous fuels – Metricseries – Specifications – Part 2: Spigot fittings for butt fusion, for socket fusion using heated tools and for usewith electrofusion fittings

ISO 8085-3, Polyethylene fittings for use with polyethylene pipes for the supply of gaseous fuels – Metricseries – Specifications – Part 3: Electrofusion fittings

EN 13100-3: 2004, Non destructive testing of welded joints in thermoplastics semi-finished products – Part 3:Ultrasonic testing

EN 1555-3 : 2010, Plastics piping systems for the supply of gaseous fuels. Polyethylene (PE). Fittings

EN 12201-3 : Plastics piping systems for water supply, and for drainage and sewerage under pressure –Polyethylene (PE)-Part 3 : Fittings

ASTM F1055, Standard Specification for Electrofusion Type Polyethylene Fittings for Outside DiameterControlled Polyethylene Pipe and Tubing

ISO 13954 : Plastics pipes and fittings - Peel decohesion test for polyethylene (PE) electrofusion assembliesof nominal outside diameter greater than or equal to 90mm

ISO 13955 : Plastics pipes and fittings – Crushing decohesion test for polyethylene (PE) electrofusionassemblies

ISO 13956 : Plastics pipes and fittings – Decohesion test of polyethylene (PE) saddle fusion joints –Evaluationof ductility of fusion joint interface by tear test



ISO/DTR 16943

2 © ISO 2010 – All rights reserved

EN 473, Non-destructive testing – Qualification and certification of NDT personnel – General principles

EN 583-2, Non-destructive testing – Ultrasonic examination – Part 2: Sensitivity and range setting

EN 583-4, Non-destructive testing – Ultrasonic examination – Part 4: Examination for discontinuities

perpendicular to the surface

EN 12668-1, Non-destructive testing – Characterization and verification of ultrasonic examination equipment –Part 1 : Instruments, Part 2 : Probes, Part 3 : Combined equipment

EN 12668-2, Non-destructive testing – Characterization and verification of ultrasonic examination equipment –Part 2 : Probes

EN 12668-3, Non-destructive testing – Characterization and verification of ultrasonic examination equipment – Part 3 : Combined equipment

3 Terms and definitions

For this document, the following terms and definitions apply.

3.1test frequencyeffective ultrasonic wave frequency used to test the object, usually measured at the receiving point

3.2ultrasonic waveany acoustic wave having a frequency higher than the audible range of the human ear, generally taken as

higher than 20 kHz

3.3pulseultrasonic signal of short duration

3.4phased array probeprobe consisting of several elementary transducers capable of working independently with different ampli-tudes and/ or phases resulting in various beam angles and focal distances

3.5probe

search unit electro-acoustic device, usually incorporating one or more transducers intended for transmissionand/or reception of the ultrasonic waves

3.6transduceractive element of the probe causing the conversion of electrical energy into sound energy and vice versa

3.7amplitude linearitymeasure of the proportionality of the amplitude of the signal input to the receiver and the amplitude of thesignal appearing on the display of the ultrasonic test instrument or on an auxiliary display

3.8

dynamic rangerange of signal amplitudes that can be handled by the ultrasonic test equipment without overloading orexcessive distortion and without being too small for detection



ISO/DTR 16943


3.9flaw (defect) detection sensitivi tycharacteristic of ultrasonic test equipment defined by the smallest detectable reflector

3.10

gain controldB control gain adjustment instrument control, normally calibrated in decibels with which a signal may beadjusted to a convenient amplitude

3.11resolutioncharacteristic of the ultrasonic test equipment defined by the minimum distance between two reflectors pro-viding two dissociable indications

NOTE Distinction is made between the axial resolution following the direction of propagation and thelateral resolution following a direction perpendicular to it.

3.12

ultrasonic test equipmentequipment consisting of ultrasonic test instrument, probes, cables and all devices connected to the instrumentduring testing

3.13ultrasonic test instrumentinstrument used together with the probe or probes, which transmits, receives, processes and displaysultrasonic signals for non-destructive testing purposes

3.14calibration blockstandard test block piece of material of specified composition, surface finish, heat treatment and geometricform, by means of which ultrasonic test equipment can be assessed and calibrated

3.15reference samplesample of similar composition to component/material under test containing well-defined reflectors, used toadjust the amplitude and/or time scale of the ultrasonic test equipment in order to compare detecteddiscontinuity indications with those arising from the known reflectors

3.16side drilled hole (SDH)circular cylinder reflector which is created parallel to the test surface

3.17automatic scanning

mechanical displacement of the probe over the test surface

3.18scanningsystematic relative displacement between the sound beam and the test object

3.19transmission techniquetesting technique in which the quality of a material is assessed by the intensity of the ultrasonic energyincident on a detecting probe after it has been transmitted through that material

NOTE This may be performed using continuous waves or pulses.

3.20back wallsurface opposite the test surface in the pulse-echo normal probe technique



ISO/DTR 16943


3.21beam indexpoint on the test surface on which the axis of an ultrasonic beam is incident

3.22

scanning directiondirection of movement of a probe over the test surface

3.23test surfacesurface over which the probe travel

3.24test objectobject to be tested; object under test or examination

3.25couplant

coupling medium interposed between the probe and the test object to enable the passage of ultrasonic energybetween them, such as water, glycerine, etc.

3.26transfer correctioncorrection of the gain setting of the ultrasonic test equipment when transferring the probe from a calibration orreference block to the test object (including losses due to coupling, reflection and attenuation)

3.27flaw depthshortest distance from the reflector to a test (reference) surface

3.28

sound path lengthpath length of a sound wave within a test object

3.29reference sample methodmethod for assessment of a discontinuity by comparing echoes from the discontinuity with echoes from knownreflectors in a reference sample

3.30 A-scan disp lay A-scan presentation display of the ultrasonic signal in which the X-axis represents the time and the Y-axis theamplitude

3.31B-scan displayB-scan presentation a cross-sectional display of a test object formed by plotting the beam path lengths forechoes with preset range of amplitude, in relation to the position of beam axis as the probe is scanned in onedirection only

NOTE It is generally used to show the depth and length of a reflector.

3.32focal pointfocus point showing the maximum sound pressure at the greatest distance from the source of sound



ISO/DTR 16943


4 General

4.1 Purpose The purpose of this document is to describe the ultrasonic method for inspecting polyethylene electrofusion joints. The requirements specified by this document cover the equipment, preparation, performance of theexamination and reporting. Methods to be used for the ultrasonic assessment of indications and acceptancecriteria shall be specified.

4.2 Use Although not all requirements of this document can be applied universally to all inspections, situations andmaterials, it does provide basis for establishing contractual criteria between the users and may be used as ageneral guide for preparing detailed specifications for a particular application. This document also provides thereference decision criteria for the electrofusion joint quality control.

5 Apparatus

5.1 Ultrasonic imaging system

The ultrasonic imaging system should have the capability of electronic scanning of the focal point, whichmeans that the position of focal points can be controlled in real time. Lateral scanning of focal point byconsecutive activation of array elements and depth scanning of focal points by controlling the dynamicaperture size should be possible. As a result of the electronic scanning of the focal point, real time images canbe obtained.

The resolution of results by ultrasonic imaging system or ultrasonic B-scan should distinguish each winding ofthe heating wire in the electrofusion fitting.

5.2 Transducer Any types of transducer including array type, focused type, and divided types can be used if it satisfies the

requirement of 6. (General examination requirements) with connected ultrasonic imaging system.

An ultrasonic transducer converts the electrical energy to ultrasound and back to electrical energy. The centrefrequency of the transducer should be chosen according to the coupler thickness. But the relation of fittingthickness and frequency can be changed if necessary. In general higher frequencies provide better resolutionand lower frequencies provide better penetration.

5.3 Data displayUltrasound cross sectional images of the elelctrofusion joints can be displayed in real time. The horizontalscale indicates the distance of scanning and the vertical scale indicates the depth of the image area from theface of the transducer. The reflected ultrasound indicates acoustic impedance discontinuities of whichintensity represented by brightness or colour bar.

5.4 Couplant A couplant is required between the face of the transducer and the examination surface to permit transmittanceof ultrasound from the transducer unit into the material under examination. The same couplant used forcalibration shall be used for the examination. During the performance of a contact ultrasonic examination, thecouplant layer between transducer face and examination material must be maintained adequate thickness.



ISO/DTR 16943


6 General Examination Requirements

6.1 System Calibration The ultrasonic transducer, electrical instrumentation and display monitor should be capable of the repetition oftest results by system calibration. Prior to examination or every 4 hours, calibration of the system inaccordance with following sensitivity setting is required.

6.2 Sensiti vity Setting

The sensitivity setting should be carried out using same make and size of electrofusion fitting as that to betested. Put the transducer on the outer surface of the electrofusion fitting. (see Figures 1 and 2)

Figure 1 - Calibration method

Figure 2 - Sensitiv ity setting – sample image obtained from the electrofusion f itting

6.3 Examination Time

The examination should conducted after the end of cooling time specified for the fitting.



ISO/DTR 16943


6.4. Examination Volume

The examination volume should cover the heat affected zone above and the plane of the heating wires andthe same distance below. If the position of the heat affected zone is unknown, half of the thickness of theelectrofusion fitting above and below the plane of the heating wires should be used.

The examination volume in the axial direction is the nominal length of fusion which is expected fusion lengthindicated by the aligned heating wires.

7 Procedure

7.1 System Setup

Set up the ultrasonic imaging system and select the correct transducer that is recommended in accordancewith the full thickness of the coupler and allows inspection of the fusion interface. Although Table 1 shows therecommended frequencies for each thickness range, the optimal frequency can be shifted up or down

depending on the attenuation of the material of the production item.

Recommended Frequency (MHz) Thickness(mm)

3.5 Over 30

5.0 10~50

7.5 Up to 30

Table 1 — Type of t ransducers

Place the transducer with the appropriate coupling medium on the reference sample.

Adjust the sensitivity according to the clause 6,2 then the ultrasonic image system is calibrated. If it is difficultto get clear image of heating wires, it may be necessary to change the frequency used.

7.2 Surface of specimen

Prepare the inspection surface so that it is free from contamination, such as dirt, dust, ice, etc. Visually inspect

the inspection surface and note the position of any surface damage.

7.3 Examination

Before startiing the inspection, insure that the proper coupling is achieved and this is maintained throughoutthe scan.

Record zero datum (starting position) and move the transducer continually around the circumference of the joint to inspect the entire circumference and width of the joint. Record and mark on the fitting any areas thatcould not be inspected.

The recordable indications are those caused by voids, cracks, bad fusion interfaces, dislocations of heatingwires, within the examination volume.



ISO/DTR 16943


The indication at the edge of the fusion zone should not be considered as recordable indications if theindication does not penetrate beyond the second wire position from the each edge of the fusion zone.

Record the results of the ultrasonic inspection and evaluate the quality of the fusion joint according to theevaluation of discontinuities.

7.4 Measuring of indication

When an indication is detected during examination, the indication should be measured in millimetres.

When an indication starts from the ultrasonic shadow area blocked by a heating wire or any other reflector, theindication measurement should start from the beginning of the wire shadow area.

When an indication is located underneath of consecutive ultrasonic shadow areas blocked by consecutiveheating wires, it should be assumed that the indication is connected through the shadow areas and the

indication measurement should include the shadow areas.

8 Quality Assurance Provisions

8.1 Personnel Qualification If the evaluation is performed manually it is essential that evaluation be performed by properly trained andqualified testing personnel. The user must be trained in ultrasonic examination (relevant standards) and haverecognized qualifications. The personnel shall be aware of testing problems associated with polyethylenematerials especially those associated with electrofusion joints.

8.2 System Performance The ultrasonic transducer, electrical instrumentation and display monitor should be capable to get imageresolution to identify each heating wire individually.

9 Report

9.1 Report should include all specific test requirements, procedural details and results for a particular

examination in written agreements, procedure and reports.

9.2 Ultrasonic inspections performed in accordance with this practice should be detailed in a writtenprocedure report sufficient in detail. The inspection report shall include the following information

a) reference to this technical report

b) test report number

b) inspector name

c) inspection date

d) model number of ultrasonic test instrument

e) model, serial number and frequency of transducer(s)

f) equipment settings such as gain, rejection level, dynamic range, frame average, etc



ISO/DTR 16943


g) client drawing or part number of EF coupler

h) electrofused joint identification or manufacturer’s serial number if necessary

i) image or sketch showing the position of the recordable indications and any areas that could not be

inspected

j) if any unacceptable indications are detected, images of these indications.

One should keep overall data from inspection of examination volume for any future analysis just for the caseof possible future dispute.



ISO/DTR 16943


Annex AExamples of inspection images

( Informative)

A.1 EF joint with no defect indications

Ultrasonic image shows clear heating wires indications along the fusion interface.

A.2 Flaw indicat ion in EF joint

The white line, which is located underneath of wire indications, indicates bad fusion interface.



ISO/DTR 16943


A.3 Dislocation of heating wires

Ultrasonic image shows the dislocation of heating wires due to overheating.

A.4 Voids in EF joint

If indication is locate just above or almost at the wires, it is a void.



ISO/DTR 16943


A.5 Foreign materials in EF joint

A.6 Insert ing defect in EF joint



ISO/DTR 16943


Annex BExample of a calibration block

B.1 Calibration block In order to set up the scanning sensitivity, a calibration block is required. The calibration block should be madeof the same or acoustically equivalent material being inspected. The shape and dimension of a calibrationblock are below and it should have 5 side drilled holes in accordance with depth.(see Table B. 1 and FigureB.1) If any special examination is required, it should be performed by using the particular calibration block.

Table B. 1. The size of the side drilled holes in accordance with depth of a calibration block

Depthfrom

surfaceDistances

between holesDiameter of

hole

Distance of each holesin accordance with

depth

Number of holes inaccordance with

depth

5mm 2.0±0.15mm 1.0±0.15mm 8.0mm 5

10mm 2.0±0.15mm 1.0±0.15mm 8.0mm 5

15mm 2.3±0.15mm 1.0±0.15mm 8.0mm 5

20mm 3.5±0.20mm 1.0±0.15mm 8.0mm 5

25mm 4.0±0.25mm 1.0±0.15mm 8.0mm 5

30mm 5.0±0.30mm 1.0±0.15mm 8.0mm 5

35mm 5.0±0.30mm 1.0±0.15mm 8.0mm 5

40mm 6.0±0.40mm 1.0±0.15mm 8.0mm 5

45mm 6.0±0.40mm 1.0±0.15mm 8.0mm 5

50mm 6.0±0.40mm 1.0±0.15mm 8.0mm 5



ISO/DTR 16943

Figure B. 1 - Calibration block

General comments

(a) Holes shall be drilled and reamed, and essentially parallel to inspection surface.

(b) Length, height, width, space between hole layers and distances between hole layers and edges, areminimum values.

Choose the side drilled holes whose depth (hole to surface) is close to the thickness of coupler to beinspected. Then put the transducer on the block surface and adjust gain to get the image which has theresolution and sensitivity to identify each side drilled holes.

Where there is a difference in acoustic attenuation between the CALIBRATION block and the production item,an attenuation correction is required to compensate for the difference. The attenuation correction isaccomplished by noting the difference between signals received from the back surfaces of the calibrationblock and production material having equal thickness and correction for this difference.

Where there is a difference in speed of ultrasound between the calibration block and the production item, thecompensation of length measurement error should be corrected by measuring the horizontal and verticallength of two points in the calibration block and the production item.

Iso Dtr 16943 Ndt Final Kil

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