GB/T 40336-2021
Non-destructive testing—Leak testing—Calibration of reference leaks for gases (English Version)
- Standard No.
- GB/T 40336-2021
- Language
- Chinese, Available in English version
- Release Date
- 2021
- Published By
- General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China
- Latest
- GB/T 40336-2021
- Scope
- This document specifies two types of calibration methods for adjusting the leak used by the leak detector to determine the leak rate, one is calibration by comparison with a reference leak, and the other is calibration by direct measurement of a known volume or calculation of gas pressure. This document applies to the calibration of leaks with leak rates within the range shown in Figure 1. a) Comparative Calibration b) Volume Calibration Normal Range; Possible Range. Explanation of index number: X —— leak rate, unit is Pascal cubic meter per second (Pa·m3/s); A —— method A; B —— method B; AS —— method AS; BS — - Method BS; C - Method C; D - Method D; E - Method E; F - Method F; G - Method G. Figure 1 Calibration range
- Introduction
Analysis of the core content of the standard
GB/T40336-2021 is an important standard in the field of non-destructive testing in my country. It modifies and adopts the ISO20486:2017 international standard and stipulates two types of calibration methods for gas reference leaks:
- Comparison calibration method (Method A/AS/B/BS): Determine the leak rate by comparing with a known reference leak
- Volume calibration method (Method C/D/E/F/G): Calculate the leak rate by measuring the change in gas volume/pressure
The applicable leak rate range of the standard covers 10-10~8 Pa·m3/s. Please see the corresponding diagram for the calibration range shown in Figure 1.
Leak Classification and Technical Characteristics
Leak Type Structural Characteristics Typical Leak Rate Range Temperature Coefficient Stability Permeation Leak With Tracer Gas Chamber 10-10~10-4 Pa·m3/s ≈3.5%/K Best Capillary Leak Possible gas chamber >10-7 Pa·m3/s ≈0.3%/K Easy to clog Hole-type leak No gas chamber Industrial grade Variable Poor
Comparison of key calibration methods
Method code Technical principle Applicable leak rate range Source of uncertainty A/AS Single reference leak comparison Leaks of the same order of magnitude Leak detector linearity B/BS Dual reference leak interpolation Intermediate leak Reference leak uncertainty C Capillary volume method 10-5~0.2 Pa·m3/s Indicator segment movement measurement F Constant volume pressure change 10-7~10-3 Pa·m3/s Gas desorption effect
Implementation points and suggestions
Temperature control requirements
The standard emphasizes a 12-hour temperature adaptation period (±1K fluctuation). For permeability leaks (3.5%/K temperature coefficient), a 1°C change in ambient temperature will introduce a 3.5% system error.
Calibration process optimization
- Leak detector preheating ≥ 2 hours
- Vacuum leak purification ≥ 30 minutes
- Each leak measurement is repeated ≥ 3 times
- Positive pressure leak uses a special adapter (Figure 3 structure)
Uncertainty management
Formula (2) reveals the key parameters of temperature correction:
Qu = Qref×(Ru/Rref)×[(1+αrefΔTref)/(1+αuΔTu)]
When αu is unknown, 3.5%/K is used for quartz penetration type and 0.3%/K is used for channel type.
Standard Evolution and Innovation
Compared with ISO20486:2017, the main adjustments of GB/T40336-2021 include:
- Delete duplicate term definitions (refer to GB/T12604.7)
- Add my country's unique technical annotations (Chapter 4 Notes)
- Optimize the formula numbering system
- Supplement 7.2.4/7.3.4 introductory words
The standard is under the jurisdiction of the National Nondestructive Testing Standards Committee (SAC/TC56) and jointly drafted by CGN Testing and other institutions.
GB/T 40336-2021 Referenced Document
- GB/T 12604.7 Non-destructive testing—Terminology—Leak testing
GB/T 40336-2021 history
- 2021 GB/T 40336-2021 Non-destructive testing—Leak testing—Calibration of reference leaks for gases