Airbag inflators
DESCRIPTION OF TECHNICAL CHALLENGE
Airbag inflators need to be functional for usually more than ten years. Therefore, every airbag
inflator needs to be thoroughly tested during production. Reliability and high throughput are key
airbag-inflator testing requirements. One defective airbag inflator can cost millions of dollars as
a result of personal injury or a fatality.
Cold gas inflators are filled with a mixture of argon and a significant ratio of helium, and mosthold their charge for the anticipated lifetime. Pyrotechnical inflators must be protected against
the intake of moisture. They contain only a small percentage of helium. Only vacuum leaktesting with helium can fulfill these requirements. Any other method is not sensitive or fastenough. The size of the chamber should be adapted to the inflator. Leaky airbag generators
are usually not repaired; therefore leak location after detecting a leak is not common.

Example calculation of leak rate threshold:Net volume

50 cm³Filling pressure

400 - 700 bar (7,000 … 10,000 psi)

Acceptable loss

5%

Lifetime

15 years

Results in a leak rate of2.65 x10-6 mbar l/s.

When filled with 3% helium:

7.95 x10-8 mbar l/s

Safety factor of 3:

2.65 x10-8 mbar l/s.
-6-7-8Practically, big inflators are tested to 10 mbar l/s, smaller ones in the 10 … 10 mbarl/s
range. Due to the high throughput of airbag production lines, airbag gas generators usuallyneed to be tested within seconds. Achieving the short cycle times of the airbag industry posesa challenge to the leak testing process. The uptime of the leak testing station is another criticalmeasure for airbag manufacturers. Additionally, measurement certainty is mandatory as theairbag is a life safety device of any car.

LEAK TESTING OF COMPONENTS
AIRBAG INFLATORSTHE INFICON SOLUTION
After purging the chamber with nitrogen, theinflator to be tested is positioned in thechamber. The chamber is closed and thepurging with nitrogen is stopped. Thechamber is then pumped down to ~ 0.2 mbar
and a valve is opened to connect the leakdetector to the chamber and to measure theleak rate. The leak detector is disconnectedfrom the chamber afterwards and thechamber is vented and purged with nitrogen
again. The inflator is removed from thechamber.
The use of the INFICON LDS3000 or Modul1000 Helium Leak Detector ensures the highreliability and repeatability of the testing results needed by the airbag industry. Both leakdetectors allow for fast testing cycles and require minimal maintenance to ensure high uptimeof the leak testing stations.

BENEFITS•••••Time and cost savings due to fast and very repeatable process
High reliability of testing due to quantifiable results
Cost savings due to low maintenance system (24,000 hours of operation or more without
adjustment or recalibration)
High throughput due to long intervals between calibrations (sometimes even exceeding
one year)
Quick calibration process

Autoliv began using INFICON leak-detection equipment to test airbag igniters at its
Tremonton, Utah facilities in 2006. The program was so successful that Autoliv later
expanded its use of INFICON test equipment to quality check complete stored-gas andpyrotechnic inflators at its plant in Brigham City. Based on mass spectrometer
technology, the LDS3000 equipment at Autoliv operates in a demanding, high-speed
process that generates more than three million tests per year.

For more information on automotive testing applications, please visit
www.inficonautomotive.com

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re a c hus @ i nf i co n. c o m

Due to our continuing program of product improvements, specifications are subject to change without notice.
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