ISO/TS 16943:2023

TECHNICAL ISO/TS
SPECIFICATION 16943
Second edition
2023-11
Thermoplastic pipes for the
conveyance of fluids — Inspection
of polyethylene electrofusion socket
joints using phased array ultrasonic
testing
Tubes en matières thermoplastiques pour le transport des fluides —
Contrôle des assemblages par emboîtures électrosoudables en
polyéthylène au moyen de la technique par ultrasons multi-éléments
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General . 3
5 Information required prior to testing . 3
5.1 Items to be defined for the procedure development . . 3
5.2 Specific information required by the operator before testing . 4
5.3 Written test procedure . 4
6 Personnel qualifications . .4
7 Equipment . 4
7.1 General . 4
7.2 Ultrasonic instrument and display . 4
7.3 Ultrasonic probes . 5
7.4 Scanning mechanisms . 5
7.5 Couplant . 5
8 Range and sensitivity settings . 5
8.1 Settings . . . 5
8.1.1 General . 5
8.1.2 Range setting — test volume . 5
8.1.3 Sensitivity setting . 7
8.2 Reference sample. 7
8.2.1 General . 7
8.2.2 Reference block . . 8
8.2.3 Electrofusion socket fitting . 8
8.3 Checking of the settings . 8
9 Equipment checks . 8
10 Test procedure .8
10.1 Procedure qualification . 8
10.2 Scan increment . 10
10.3 Geometry of the fusion joint tested . 10
10.4 Preparation of scanning surfaces . 10
10.5 Temperature of fusion joint tested . 10
10.6 Testing . 10
10.7 Data storage . 11
11 Evaluation and analysis of test data.11
11.1 General . 11
11.2 Assessing the quality of the test data . 11
11.3 Identification of relevant indications . 11
11.4 Classification of relevant indications . 11
11.5 Determination of location and size of indications .12
11.6 Assessment of indications .12
12 Test report .12
Annex A (informative) Examples of phased array images .14
Annex B (informative) Example of a reference block .17
Annex C (informative) Example procedures for producing imperfections in electrofusion
[17]
socket joints .19
iii
Annex D (informative) Relationship between heating time and MFZ thickness and
detection using phased array ultrasonic testing .23
Bibliography .25
iv
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 ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves
for the transport of fluids, Subcommittee SC 5, General properties of pipes, fittings and valves of plastic
materials and their accessories — Test methods and basic specifications.
This second edition cancels and replaces the first edition (ISO/TS 16943:2019), which has been
technically revised.
The main changes are as follows:
— the definitions of cold fusion and lack of fusion have been clarified;
— procedure qualification has been revised.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
TECHNICAL SPECIFICATION ISO/TS 16943:2023(E)
Thermoplastic pipes for the conveyance of fluids —
Inspection of polyethylene electrofusion socket joints
using phased array ultrasonic testing
1 Scope
This document describes phased array ultrasonic testing (PAUT) of polyethylene electrofusion (EF)
socket joints used for the conveyance of fluids.
This document provides a test whereby the presence of imperfections such as voids, wire dislocation,
misalignment, pipe under-penetration, particulate contamination and lack of fusion in electrofusion
socket joints can be detected.
The technique is only applicable to polyethylene electrofusion socket fittings without a barrier to
ultrasonic waves.
This document also provides requirements for procedure qualification and guidance for personnel
qualifications, which are essential for the application of this test technique.
This document covers the test equipment, the preparation and performance of the test, the assessment
of indications and the reporting for polyethylene EF joints.
Acceptance criteria are not covered in this document.
NOTE 1 At the time of publication, experience only exists in the use of PAUT for polyethylene (PE80 and
[1][2][3][4][5][6][7]
PE100) electrofusion socket joint sizes between 90 mm and 710 mm (SDR 11 and 17).
NOTE 2 Interlaboratory testing has shown that PAUT is a viable method for enhancing the integrity assessment
[8][15][16]
of electrofusion joints.
NOTE 3 This document does not apply to the detection of unscraped pipe. Such detection can be achieved by
simple visual testing, provided mechanical scraping tools are employed.
NOTE 4 PAUT techniques for cold fusion detection are known to be available. However further research
verification and experience are needed to transfer the technique into an ISO International Standard. This
document does not provide any information regarding the detection of cold fusions.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 5577, Non-destructive testing — Ultrasonic testing — Vocabulary
ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel
ISO 13954, Plastics pipes and fittings — Peel decohesion test for polyethylene (PE) electrofusion assemblies
of nominal outside diameter greater than or equal to 90 mm
ISO 13955, Plastics pipes and fittings — Crushing decohesion test for polyethylene (PE) electrofusion
assemblies
ISO 23243, Non-destructive testing — Ultrasonic testing with arrays — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5577, ISO 23243 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
cold fusion
incomplete intermolecular diffusion of polymer chains for proper molecular entanglement at the joint
interface due to reasons other than contamination
Note 1 to entry: Cold fusion results in insufficient joint integrity including significant reduction of joint ductility.
3.2
inclusion
foreign material trapped in the fusion joint
3.3
lack of fusion
absence of intermolecular diffusion of polymer chains for molecular entanglement at the interface
Note 1 to entry: A lack of fusion flaw results in complete separation at the flaw location.
3.4
pipe under-penetration
incomplete penetration of the pipe into the electrofusion socket
3.5
melt fusion zone
MFZ
zone containing the fusion interface and having boundaries on either side of the interface which reflect
the limits of crystalline melting during the electrofusion socket jointing process
Note 1 to entry: The MFZ is shown in Figure 1.
3.6
misalignment
angular offset between the axis of the electrofusion socket fitting and the axis of the pipe
3.7
particulate contamination
fine particles (e.g. airborne dust) or coarse particles (e.g. sand and grit) that are present at the fusion
interface
3.8
void
empty space (or air pocket) in an electrofusion socket joint
3.9
wire dislocation
displacement of heating wires from their original position in the fitting
3.10
phased array image
one-, two-, or three-dimensional display, constructed from the phased array data
3.11
phased array setup
probe arrangement defined by probe characteristics (e.g. frequency, probe element size, beam angle,
wave mode), probe position and the number of probes
3.12
probe position
axial and radial position of the probe with respect to the heating wire coil in the electrofusion socket
joint
3.13
scan increment
distance between successive data collection points in the direction of scanning
3.14
false call
reporting an imperfection when none exists
3.15
electrofusion socket fitting
part containing one or more integral heating elements that are capable of converting electrical energy
to heat to make a joint between pipes
3.16
electrofusion socket joint
fused combination of one or more pipe components using an electrofusion socket fitting
3.17
fusion zone
one side of an electrofusion socket joint
Note 1 to entry: There are two fusion zones in a straight joint.
4 General
This document covers the equipment, preparation and performance of the test for polyethylene
electrofusion socket joints. It also covers the reporting.
This document can be used to draft a detailed procedure for phased array ultrasonic testing of
polyethylene electrofusion socket joints.
5 Information required prior to testing
5.1 Items to be defined for the procedure development
Information on the following items shall be provided:
a) purpose and extent of testing;
b) manufacturing or operation stage of electrofusion socket joints at which the testing is to be carried
out;
c) reference sample;
d) requirements for getting access to the electrofusion socket joints, the surface condition of the pipe
and the temperature range;
e) personnel qualifications;
f) reporting requirements.
5.2 Specific information required by the operator before testing
Before any testing of an electrofusion socket joint begins, the operator shall have access to all the
information as specified in 5.1 together with the following additional information:
a) written test procedure, qualified in accordance with Clause 10;
b) all relevant pipe and fitting dimensions.
5.3 Written test procedure
For all testing, a written test procedure is required. This test procedure shall include the information
specified in 5.1 and the following:
a) documented testing strategy or scan plan;
NOTE The testing strategy gives information on the probe placement, movement and component
coverage that provides a standardized and repeatable methodology for fusion joint testing. The scan plan
gives information on the volume tested for each electrofusion socket joint.
b) equipment requirements and settings (including but not limited to frequency, sampling rate, pitch
between elements and elements size);
c) evaluation of indications;
d) environmental and safety issues.
6 Personnel qualifications
Personnel performing testing in accordance with this document shall be qualified to an appropriate
level in accordance with ISO 9712 or an equivalent standard in the relevant industrial sector.
In addition to a general knowledge of ultrasonic testing, the operators shall be familiar with and have
practical experience in the use of phased array systems.
Specific theoretical and practical training and examination of personnel shall be performed on
representative polyethylene electrofusion socket joints containing natural or artificial reflectors
similar to those expected in the field.
These training and examination results shall be documented.
7 Equipment
7.1 General
The complete equipment (i.e. ultrasonic instrument, probe, cables and display monitor) shall be capable
of the repetition of test results.
For selecting the system components (hardware and software), ISO 13588 and ISO/TS 16829 provide
useful information.
Equipment used for phased array testing is described in ISO 18563-1, ISO 18563- and ISO 18563-3.
7.2 Ultrasonic instrument and display
The instrument shall be capable of selecting an appropriate portion of the time base within which
A-scans are digitized. It is recommended that the sampling rate of the A-scan should be at least six
times the nominal probe frequency. The instrument and display shall achieve a resolution capable of
identifying each heating wire individually.
7.3 Ultrasonic probes
Only longitudinal waves are feasible for polyethylene.
Any type of phased array probe can be used if it satisfies the requirements of Clause 8 with the phased
array instrument.
The most suitable ultrasonic probe frequency shall be selected in accordance with the thickness of the
electrofusion socket fitting. Table 1 shows recommended frequencies for each thickness range of the
electrofusion socket fitting.
The optimal frequency can be shifted up or down depending on the attenuation and thickness of the EF
socket fitting tested.
Table 1 — Selection of probe frequency
Recommended frequency Fitting wall thickness, t
MHz mm
3,5 30 ≤ t ≤ 50
5,0 10 ≤ t ≤ 50
7,5 10 ≤ t ≤ 30
NOTE In general, higher frequencies provide better resolution and lower frequencies provide better
penetration.
7.4 Scanning mechanisms
To achieve consistency of the images (collected data), guiding mechanisms and scan encoder(s) shall be
used.
NOTE Space and accessibility conditions can require special encoded scanners to facilitate the inspection.
7.5 Couplant
In order to generate proper images, a couplant shall be used which provides a constant transmission of
ultrasound between the probe and the fusion joint tested.
The same couplant used for calibration shall be used for the testing. Any couplant used should to be
cleaned off after testing.
8 Range and sensitivity settings
8.1 Settings
8.1.1 General
The setting of range and sensitivity shall be carried out prior to each testing period in accordance with
this document. Any change of the phased array setup (e.g. probe position and steering parameters)
will require a new setting. The set-up shall be optimized on the reference reflectors to give a minimum
signal-to-noise ratio of 6 dB.
8.1.2 Range setting — test volume
The range in the depth direction shall cover at least the melt fusion zone above the plane of the heating
wires and the same distance below.
If the position of the melt fusion zone is unknown, at least half of the thickness of the electrofusion
socket fitting above and below the plane of the heating wires shall be used (see Figure 2).
When feasible, the range monitored may be extended from the probe-fitting interface and include the
inside surface of the pipe.
The range in the axial direction shall cover the nominal length of the fusion zone, which is the expected
fusion length indicated by the aligned heating wires.
The range in the circumferential direction shall include the full circumference.
Areas not tested due to obstacles (e.g. fusion indicators and connectors) shall be reported.
NOTE Annex D provides information regarding the measurement of MFZ thickness using PAUT.
Key
1 electrofusion socket fitting
2 MFZ boundary
3 heating wire
4 pipe
SOURCE: Reference [13], reproduced with the permission of the authors
Figure 1 — Photograph of melt fusion zone (MFZ)
Key
1 electrofusion socket fitting
2 MFZ boundary
3 heating wire
4 test area
5 pipe
t thickness
Figure 2 — Test area with known MFZ (top) and unknown MFZ (bottom)
8.1.3 Sensitivity setting
After selection of the scanning technique, the following steps shall be taken using the same focusing,
coupling and wedge or delay-line conditions for calibrating reference sensitivity as used for
electrofusion socket joint testing.
a) Equalize the response for each delay law on a side-drilled hole (SDH) at the depth of interest.
Ensure that the difference between each delay law shall not deviate by more than ±3 dB from the
average amplitude response.
b) Set the response from the SDH to an amplitude between 40 % and 80 % of screen height. This shall
be considered the reference sensitivity.
c) Evaluate the scan surface interface ring time to ensure sufficient resolution exists to discern the
MFZ.
d) Evaluate the resolution of adjacent turns of wire in the fitting to ensure that there is more than a
12 dB drop between the peak amplitudes from adjacent turns of wire.
8.2 Reference sample
8.2.1 General
A reference sample shall be used to determine the adequacy of the setting (e.g. coverage, sensitivity).
The temperature of the reference sample shall be the same as the temperature ±5
...