AVS 59th Annual International Symposium and Exhibition
    Vacuum Technology Monday Sessions
       Session VT-MoA

Invited Paper VT-MoA1
First International Comparison of Standard Leak Calibrations of Metrological Institutes

Monday, October 29, 2012, 2:00 pm, Room 14

Session: Gas Flow, Leaks, Permeation and Mass Analysis
Presenter: K. Jousten, PTB, Germany
Authors: K. Jousten, PTB, Germany
K. Arai, NMIJ, Japan
U. Becker, PTB, Germany
O. Bodnar, PTB, Germany
F. Boineau, LNE, France
J.A. Fedchak, NIST
V. Gorobey, VNIIM, Russian Federation
W. Jian, SPRING, Singapore
D. Mari, INRIM, Italy
P. Mohan, NPL/I, India
J. Šetina, IMT, Slovenia
B. Toman, NIST
M. Vicar, CMI, Czech Republic
YH. Yan, NIM, China
Correspondent: Click to Email
The measurement of leak rates has become an important test in industry for function tests, quality and safety management, and for environmental protection. Leak tests are performed not only for vacuum chambers, but also for various containers like electrical high power switches, pace makers, refrigerating systems, isolation vacuum, rims, and tanks. The leak tests are performed by leak detectors which mainly use helium as test gas. Traceability to the SI units is given by calibrated standard leaks that emit a well known flow rate of typically helium gas. Many National Metrological Institutes (NMIs) provide such traceability in their vacuum sections.The NMIs that signed the mutual recognition arrangement committed themselves to prove equivalence of their calibration measurement capabilities. The test of equivalence is a comparison where a transfer standard is calibrated at the participants' facilities and the results compared. The difference between the laboratory result and a reference value or a bias of a laboratory must not exceed the uncertainty of this difference or the bias.To test equivalence of standard leak calibrations NMIs from 11 countries performed a comparison with two helium permeation leaks as transfer standards. The leak rates were 4E-11 mol/s for standard leak L1 (1E-4 Pa L/s at 23°C) and 8E-14 mol/s (2E-7 Pa L/s at 23°C) for L2 respectively. For the latter, only 6 NMIs had measurement capabilities. Since leak rates from permeation leaks decrease with time, special evaluation procedures had to be applied to calculate a reference value and to compare the results of the NMIs. Also a statistical method was applied to evaluate a possible bias of a laboratory. Most of the 11 laboratories proved equivalent in the case of transfer standard L1 and all for L2. These results will be published and serve as basis for mutual recognition of calibration results.