GB/T 11344-2021 English PDF (GBT11344-2021)

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GB/T 11344-2021: Non-destructive testing - Ultrasonic thickness measurement
GB/T 11344-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 19.100
CCS J 04
Replacing GB/T 11344-2008
Non-destructive Testing - Ultrasonic Thickness
Measurement
(ISO 16809:2017, NEQ)
ISSUED ON: MAY 21, 2021
IMPLEMENTED ON: DECEMBER 1, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative References ... 5
3 Terms and Definitions... 5
4 Method Summary ... 5
5 General Requirements ... 8
6 Measurement Preparation ... 10
7 Instrument Settings ... 14
8 Testing Reports and Records ... 17
Appendix A (informative) Ultrasonic Sound Velocity of Common Engineering
Application Materials ... 19
Appendix B (informative) Ultrasonic Thickness Measurement of Corrosion of
Vessels and Pipelines ... 22
Appendix C (informative) Selection of Measurement Method ... 29
Appendix D (informative) Factors Affecting Measurement Accuracy ... 33
Appendix E (informative) Instrument Settings under Special Testing Conditions
... 44
Bibliography ... 46
Non-destructive Testing - Ultrasonic Thickness
Measurement
1 Scope
This Standard specifies the ultrasonic thickness measurement through the ultrasonic
pulse-echo contact method.
This Standard is applicable to the ultrasonic thickness measurement of metal and non-
metal materials.
2 Normative References
The contents of the following documents constitute the indispensable clauses of this
document through the normative references. In terms of references with a specified
date, only versions with a specified date are applicable to this document. In terms of
references without a specified date, the latest version (including all the modifications)
is applicable to this document.
GB/T 9445 Non-destructive Testing - Qualification and Certification of NDT Personnel
(GB/T 9445-2015, ISO 9712:2012, IDT)
GB/T 12604.1 Non-destructive Testing - Terminology - Ultrasonic Testing (GB/T
12604.1-2020, ISO 5577:2017, MOD)
GB/T 20737 Non-destructive Testing - General Terms and Definitions (GB/T 20737-
2006, ISO/TS 18173:2005, IDT)
GB/T 36439 Non-destructive Testing - Certification and Qualification of Aerospace
Non-destructive Testing Personnel
3 Terms and Definitions
The terms and definitions defined in GB/T 12604.1 and GB/T 20737 are applicable to
this document.
4 Method Summary
4.1 By measuring the time for the ultrasonic signals transmitted by the probe to pass
through the measured material for one, two or multiple times, the thickness of the
measured material is determined. The thickness is calculated by dividing the product
of the already-known sound velocity and the pulse echo time by the number of pass-
5.1.4 The ultrasonic flaw detector with A-scan display measures thickness by reading
the distance between the initial pulse and the first back wall echo after the calibration
of the zero point and sound velocity, or through the A-scan display of the distance
between multiple back wall reflection echoes on the baseline during the calibration.
5.1.5 The ultrasonic thickness gauges shall be calibrated in accordance with the
currently effective methods every year and satisfy the requirements for use.
5.2 Probes
5.2.1 Ultrasonic thickness measurement shall adopt dual-element or single-element
longitudinal-wave probes.
5.2.2 The other specific requirements for the probes are shown in 6.3.
5.3 Coupling Agent
5.3.1 Ultrasonic thickness measurement satisfies the acoustic coupling between the
probe and the material by applying fluid or gel. The coupling agent shall have good
sound permeability and have no adverse effects on the tested materials, equipment
and operating personnel.
5.3.2 The selected coupling agent shall be suitable for the irregularities of the surface
condition and shape of the tested product, so as to ensure sufficient coupling.
5.3.3 The requirements for the coupling agents used under special measurement
conditions are shown in 6.4.
5.4 Calibration Blocks
The sound velocity and thickness of the calibration blocks shall be already-known, and
identical or similar to the material of the tested product. The calibration blocks can be
in a set or a step. The thickness of the blocks should cover the thickness range of the
tested product. A thickness value of the blocks shall not be less than the maximum
thickness of the measurement range, and the other thickness value of the block shall
not be greater than the minimum thickness of the measurement range.
The production of steel step blocks for thickness measurement may take GB/T 39432
as a reference. The production of other materials of blocks for thickness measurement
may also take this document as a reference.
5.5 Testing Personnel
5.5.1 The personnel performing ultrasonic thickness measurement in accordance with
this document shall be subjected to personnel qualification or certificate in accordance
with GB/T 9445, GB/T 36439 or the system agreed by all parties to the contract, obtain
the qualification certificate for the ultrasonic testing personnel, and receive on-the-job
training and authorization by the employer or agent.
5.5.2 The testing personnel shall understand the characteristics of the tested product
and material.
6 Measurement Preparation
6.1 Surface Condition
6.1.1 The surface of the tested product shall be clean and flat, and free of loose surface
or non-sticky coatings. The measurement contact area shall be not less than 2 times
the diameter of the probe. Poor contact may cause the loss of acoustic energy and
changes in signal and sound beam propagation paths.
6.1.2 If there is a coating on the measurement surface, then, the coating shall be well-
combined with the material. The existence of close-fitting coatings (such as: paint and
enamel, etc.) is allowed. Only a few thickness gauges can measure the thickness of
the coating. When measuring the thickness of a coated product, the thickness of the
coating and the sound velocity shall be already-known, otherwise, Method 3 (multiple-
echo method) shall be adopted for the measurement.
6.1.3 Generally, the surface of corroded and abrasive products is relatively rough and
a little corroded, or there may be other defects (see Appendix B). The corroded surface
shall be polished to remove rust spots. During polishing, the thickness shall not be
reduced to below the acceptable minimum value.
6.2 Selection of Methods
6.2.1 General requirements
6.2.1.1 Ultrasonic thickness measurement is usually applied to the following two fields:
---measurement during manufacture;
---in-service measurement of residual wall thickness.
6.2.1.2 In accordance with the material, geometrical shape and thickness of the tested
product, as well as the requirements for measurement accuracy, appropriate
instruments and measurement methods shall be selected. See Appendix C and
Appendix D.
6.2.1.3 The accuracy of thickness measurement depends on the accuracy of acoustic
time measurement. Adopt different modes for the time measurement (zero-crossing
measurement, leading-edge measurement and peak-value measurement). The
accuracy of Method 3 (multiple-echo method) is higher than that of Method 1 and
Method 2. When the measurement is conducted on the basis of different frequencies,
the measurement accuracy of high-frequency probe is higher than that of low-
frequency probe.
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