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JJF 1126-2004 English PDF (JJF1126-2004)

JJF 1126-2004 English PDF (JJF1126-2004)

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JJF 1126-2004: Calibration Specification for Ultrasonic Thickness Instruments

This Specification is applicable to the calibration of ultrasonic thickness instruments of which the resolution is 0.1mm and 0.01mm.
JJF 1126-2004
NATIONAL METROLOGICAL VERIFICATION REGULATIONS
OF THE PEOPLE REPUBLIC OF CHINA
JJF 1126-2004
Calibration Specification for Ultrasonic Thickness
Instruments
ISSUED ON: SEPTEMBER 21, 2004
IMPLEMENTED ON: MARCH 21, 2005
Issued by: General Administration of Quality Supervision, Inspection
and Quarantine of the People's Republic of China
Table of Contents
1 Scope ... 5
2 Normative references ... 5
3 Overview ... 5
4 Metrological characteristics ... 7
5 Calibration conditions ... 8
6 Calibration items and calibration methods ... 9
7 Calibration result expression ... 11
8 Recalibration time interval ... 11
Annex A Calibration certificate content ... 12
Annex B Technical requirements for standard thickness block ... 13
Annex C Technical requirements for standard round tubes ... 14
Annex D Uncertainty analysis on calibration results of indication error of ultrasonic thickness instruments ... 15
Annex E Sound velocity and sound velocity ratio of various materials ... 19 Calibration Specification for Ultrasonic Thickness
Instruments
1 Scope
This Specification is applicable to the calibration of ultrasonic thickness instruments of which the resolution is 0.1mm and 0.01mm.
2 Normative references
This Specification referred to the following referenced documents.
JJF 1001-1998, General Terms in Metrology and Their Definitions
JJF 1059-1999, Evaluation and Expression of Uncertainty in Measurement
GB/T 12064.1-1999, Nondestructive testing terms - Ultrasonic testing
GB/T 11344-1989, Measuring thickness by ultrasonic pulse-echo contact
method
When using this Specification, it shall use the currently valid versions of the above references.
3 Overview
The ultrasonic thickness instruments are mainly used to measure the wall thickness of hulls, oil and gas pipelines, high-pressure vessels, boilers as well as the thickness of large area sheet. The material to be tested can be metal materials such as steel, or non-metal materials such as plastic and nylon. The principle is that the instrument emits ultrasonic waves through the probe and reflects back to the test head after reaching the bottom surface of the test piece. Use a counter to accurately measure the time that ultrasonic waves travel through the material and calculate it as follows. Display the measured thickness value on the display.
6 Calibration items and calibration methods
Before calibration, it is necessary to confirm that there are no defects in appearance and electromechanical functions that affect the calibration
metrological characteristics.
6.1 Repeatability
After the instrument is turned on, operate the sound speed adjustment key or the sound speed dial to adjust the sound speed to 5900m/s. Return to the state of the instrument measuring thickness. Apply the coupling agent to the center of the 5.5mm standard thickness block. Use the probe to continuously measure this thickness block 5 times. Take the difference between the maximum and minimum values as the repeatability of the instrument. It can also directly use the random calibration thickness block of the instrument to conduct this calibration.
6.2 Indication error
Conduct calibration according to the procedures specified by the instrument. Measure the standard thickness blocks in Annex B one by one in the measuring range of the instrument. Continuously measure each block 3 times. Take the average value as the indication value of the instrument in the thickness block. When the same ultrasonic thickness instrument has two resolutions: 0.1mm and 0.01mm, it shall respectively conduct the calibration of two indication errors. The indicator error ??H is calculated according to the following formula: Where,
- Average indication value of the instrument;
H - Nominal value of standard thickness block.
6.3 Indication error of curved wall thickness measurement
Conduct calibration according to the procedures specified by the instrument (do not recalibrate if the probe is not replaced). According to the provisions of Table 2, measure the wall thickness of a standard round tube corresponding to its resolution (see Annex C for technical requirements). When measuring, place the sound insulation layer 1 of the probe parallel to or perpendicular to the prime line of the standard round tube 2 (as shown in Figure 2). Swing the probe slightly and observe the indication value. Take the minimum stable indication Annex A
Calibration certificate content
1. Title: Calibration certificate;
2. Laboratory name and address;
3. Site for calibration;
4. Certificate or report number, page number and total number of pages; 5. Name and address of the submission authority;
6. Name of the instrument to be calibrated;
7. Manufacturer, model specifications, and number of the instrument to be calibrated;
8. Name of the metrology standard used for calibration and its expiration date; 9. Name and number of this Specification and description on any deviation, addition or deletion to this Specification;
10. Ambient temperature during calibration;
11. Calibration results of calibration items;
12. Measurement uncertainty of calibration results of indication error; 13. Signature of calibrator, signature of verifier, signature of approver; 14. Issue date of calibration certificate;
15. Recommendation for recalibration time interval;
16. No partial reproduction of the calibration certificate without written approval from the calibration laboratory.

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