The Clean Air Act (CAA) of 1970, which sought to establish air quality goals and impose pollution control technology requirements on new and existing stationary sources and on motor vehicles, drove the need for leak testing on air conditioning systems used in automobiles, among other components. Leaky air conditioning lines and systems were not permitted, and companies faced penalties if they did not manufacture clean, leak-free air conditioning systems. While at face value this does not seem like a large undertaking, the simple task of ensuring a leak-free air conditioning system impacts several other components in the assembly - each part needs to be verified for leaks while maintaining cost effectiveness and production levels.
Greater fuel economy brought with it more complex hose technology with many more parts - all needing to maintain leak integrity. What was once a simple aluminum hose with connectors on either side has morphed into multiple braised point aluminum hoses and even with hoses within hoses. Previously used leak tests used are no longer adequate for newer and more complex parts.
As the complexity of parts increase so does the costs to produce them.& In many cases the stacked costs of subcomponents to the finished product create scrap changes for suppliers. Previously, suppliers would leak test an entire assembly after it was produced.; If a leak was detected the part would be reworked or in some cases scrapped. But with an increasing number of costly subcomponents used in these assemblies, rework is costly and scrapped parts are unacceptable. Thus, there is a greater need to verify the leak integrity of the subcomponents before the full assembly is complete.
Some automotive parts cannot be tested in a more commonly used leak test method because of limitations of the part either because of material restrictions or physical restrictions.
Helium is commonly used for leak testing but is ill-suited with the presence of rubberized materials and some plastics. Higher pressure is an effective method to detect leaks faster but will not work with products that have components that are designed to only withstand a few pounds of pressure. These are becoming more common with examples like the cap-less fuel lines now present in automobiles.
Another factor driving the need for leak testing is the ever-present need to reduce costs in the production of parts used in the cars. Parts and even parts of the chassis that were once made from single sheets of metal are now multiple injection modeled pieces of plastic coming together to form a single part. Leak testing is driven by the need to ensure that rain or other moisture does not enter the vehicle through the many connection points of the multiple parts. In this case, leak testing is necessitated by customer pressure rather than regulatory pressure.
There has also been an increase in the number of companies entering the leak detection space and the amount of misinformation provided to customers. There are customer horror stories of metal vacuum chambers leaking over time because welds are failing from cheaper, new to the market leak detection providers. Even a leading supplier of leak detection equipment has provided the following misinformation to their users, “applications (where) older methods are not sufficient, such as bubble test, pressure decay and differential pressure methods. These methods sometimes give a false sense of security.
It should be noted that this vendor does not produce equipment used for pressure decay nor differentiation pressure testing and both tests continue to be used with great success in the automotive industry, as well as other industries. Moreover, in many cases these are the only types of test that can be used because of the limitations described above.
In other cases, leak test vendors provide systems only to find out that their testing is not adequately detecting the leaks because of the methods used by their supplier. IHX (Internal Heat Exchange) tubing is a very good example of this problem.& It has been the experience of VIC that some suppliers pass bad parts as good because the testing methods and equipment they use have a design flaw. VIC has a patent pending on IHX leak testing.
Contact VIC for an IHX Test Audit of your Leak Test vendors’ equipment to find out if you are among those suppliers that are passing bad parts because of faulty test methods.
Test methods most commonly used in the automotive industry and in other industrial applications are as follows:
Pressure Decay: A pressure vessel is filled with air until it reaches its target pressure. Then the air source is cut to isolate the pressure. The decay (loss) of pressure over a specified period is measured; any loss in pressure indicates a leak.
Pressure Differential: This method also involves measuring the drop in pressure inside the part over time as a result of escaping material. However, in a differential pressure test, the change in pressure is measured inside the part compared to the pressure inside a control volume charged to the same pressure as the part.
Tracer Gas Ambient Pressure with Sniffer Probe: A part is charged (air is evacuated, and tracer gas is added) and an operator uses a hand-held leak tester to detect if Helium can be detected signaling a leak.
Tracer Gas Accumulation at Ambient Pressure with Clam Shell: Almost the same as a Tracer Gas Ambient Pressure with Sniffer Probe, with the difference being that the leak testing is performed at specific locations (test points) usually at weld points along a pipe/hose and a small enclosure wraps around these test points. A sniffer probe is inserted into the enclosure when closed. The enclosure opens and closes along one hinge making it resemble a clam shell, hence the name.
Tracer Gas Accumulation with Hard Vacuum: The test part is loaded into a test machine. Tracer gas escaping the test part is allowed to accumulate in an enclosure that surrounds the part at atmospheric pressure. The accumulated tracer gas is then mixed and sampled by a mass spectrometer.
The automotive industry is under constant pressure to improve quality and fuel consumption, which requires leak-tight components. Keep your brand eco-friendly with leak-tight and safe components using VIC leak detection solutions.
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Leaks discovered after a component is in a vehicle hurt your bottom line as well as your brand. Reduce warranty costs and recalls due to quality issues related to leakage.