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Airbag Seams
How internal seat airbags work
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| Side airbag deployed |
Seat airbags are designed to deploy upon side impact only. In an accident, sensor at the base of the “B” pillar detects the impact and sends a signal via the SRS control module to the seat airbag.
Airbags are usually internally tethered for guidance and reinforced to prevent them from ripping under the extreme pressures involved in their deployment. At the heart of every airbag is a hybrid gas generator. This is a canister filled with a high-pressure gas and a flammable substance.
When an electrical signal reaches the canister, it fires the charge, which, in turn, releases the high-pressure gas. Rapid release of the gas inflates the airbag. When the airbag is deployed, it breaks out of its holder and bursts through the seat seam. This allows the airbag to inflate fully. All this happens within 70/1000 of a second!
If a seat seam has been altered outside of the manufacturer’s specifications, the airbag could deploy too early, or too late, or, possibly in the wrong position, and it won’t be effective. This means that any work done on seat upholstery must be done by someone who not only understands how airbags work, but also has an in-depth knowledge of the car seat upholstery trade. At Retro, we have more than 40 years of experience in car upholstery and our airbag seam sewing process is approved by Land Transport New Zealand.
How airbag seams are sewn
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| Computerised production airbag sewing machine |
We have found, through extensive testing, that every vehicle model needs to have a different thread combination to be within a set tolerance that complies with factory specifications.
All our airbag seams are sewn using data from comparative tests (see testing below) that provide the tensile strength of the original factory seam. This information is used to select the correct thread combination. The data is recorded on a tag that is sewn into the airbag seam. Each seam has a unique serial number that can be traced, if necessary, to reveal all the information about the seam.
Airbag seam testing procedures
Comparative testing
As the major New Zealand car upholstery market leader, Retro Vehicle Enhancements has built up an extensive collection of most models’ static test results, which allows us to replace airbag seams in accordance with manufacturer specifications.
Every model we have worked on since May 2000 has had its original seat airbag seams tested, and a comparable test has been done on the new seam.
We also film the airbag deployment using an ultra-high speed ballistics camera (imported from the U.S.A.) with which we can confirm our comparative test results. The camera allows us to show the airbag deploying within the time frame stipulated for factory-tested seats. These results are available on disc. Contact us for more information.
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| Airbag high speed footage | |||
All our tests that the results of static comparative tests done on our seams measure up to those achieved in factory testing of original seams. The Land Transport Safety Authority (LTSA) has witnessed our test procedures and sent us a letter recognising our procedures.
As we strive to maintain our high standards of safety and quality, we continue to investigate and implement the latest overseas technology and equipment as soon as it becomes available.
Airbag seam testing machine
We process every vehicle model side impact airbag (SIAB) through our seam data analyser, which is certified and audited by an LTNZ-recognised procedure.
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| Airbag seam testing machine |
How airbag seams are certified
The criteria for the certification of airbag seams include:
- Original factory covers must be tested and a comparison made between the thread combinations of the original and the new seams.
- The new seams have been stitched according to tested samples.
- The seat covers have been fitted by a trained installer, using the same method as the original fitment.
Under the guidance of Land Transport New Zealand, our procurers are audited by an independent transport consultancy. Copies of the test results are available at our dealership.
Certificates of compliance are issued for certification purposes only.