Testing High-Pressure Air Bags
by: Vetter Air Bags
As the high-pressure air bag is an important component of the emergency services' equipment arsenal and have helped save many lives, the need for adequately maintaining and regularly testing this equipment is imperative for making sure that they still will be able to save lives in their next mission. This is the reason for our trade-in program.
The service life expectancy of high-pressure air bags is from 10-20 years, depending on various factors that are completely under the control of the user. The chief component of all high pressure air bags is elastic rubber, which is a "living" material, subject to aging processes. The actual speed of the processes depends on factors such as the frequency and uses of the product, storage conditions, exposure to light, heat and humidity, and the influence of oxygen and energetic rays. Therefore regular testing is imperative to safeguard the user(s) and all who may be affected by the bag's use and ability to perform as intended. Safety should always be the highest priority.
German Law: Manufacturer's Standard
In many countries, there are no laws governing any facet of high-pressure air bag technology. Engineering, quality, manufacturing, and testing are all left to the discretion of the various manufacturers. Vetter uses the only standard in effect worldwide - German Law. The Germans have developed a testing standard that governs all facets of high-pressure air bag technology. Know as the "Pressure Vessels Regulation", the regulation sets standards and schedules requirements for pressure vessel testing, which include first-time, acceptance and ongoing tests.
The Vetter production facility is inspected by the German TUV (a third-party testing) organization. Each air bag is examined for the first time after its production before leaving the manufacturing plant. High-pressure bags are approved and released for sale after pressure and type approval tests have been completed by an authorized works inspector. The pressure test is conducted with water at a pressure of 232 psi (16bar) for steelcord reinforced bags and 174 psi (12 bar) for Kevlar reinforced bags.
High-pressure bags should be pressure tested every five years by a safety expert unless damage previously had been discovered during the annual or "post-operations" visual and functional tests - in which case, the pressure test should be done immediately after identifying the damage.
The bag must be tested "free" (i.e., not confined by a load or other bracing) with water at a pressure of 150psi (10.4bar) - i.e., 1.3 times the maximum working pressure fo the air bag, for three to five minutes. The failure pressure of the bag can be increased by as much as 40 percent if the bag is confined. The obvious reason for hydrostatic testing is safety. Water lessens the effects should the air bag burst during testing.
The purposes of the test are to determine if the bags are capable of resisting 1.3 times their maximum working pressure and identify any deformation that could endanger safety. While there is no guarantee how long a bag will perform, using the over-pressure test instead of inflating the bag at partial or full pressure increases the chance for successful performance. By testing at partial pressure only to identify leaks, an unsound pressure vessel would be discovered after the fact instead of before the failure occurs. Any leak, no matter how minor, constitutes a compromised pressure vessel and therefore test failure.
Be aware that it is possible - even though unlikely - that the high-pressure air bag could burst during the functional test. For this reason, this test should be conducted in the open air, not indoors, at a safe distance from persons, objects and buildings. Also, the operator should wear personal protective equipment in the form of safety glasses, hearing protection, and gloves.
The over-pressure test is practically a burst/no burst test - that is, when an air bag fails the test it usually bursts. Therefore, the technician performing this test also must wear protective equipment. When an air bag fails this test it must be taken out of service and destroyed.
Contact your local Vetter or distributor for more information.
Vetter Airbags is based in Zuloich, Germany. For US Distributors contact Pete Fiset at Safety Solutions International, Phone: 888-283-8837.
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