When a product or component is built to contain a liquid or gas, quality control needs to ensure the integrity of the part. Whether you’re looking at disposable plastic bottles or industrial heat pumps, leak testing procedures are a vital step in production.
This is especially true in the automotive industry, where a component’s integrity can be a matter of life and death for the end-user. And, the growing prominence of electric vehicles is creating new leak testing challenges for the industry. For manufacturers who need to match high efficiency with 100% inspection, automated leak inspection tests provide powerful solutions.
What is a Leak Test?
A leak test is more or less exactly what it sounds like. If a product flaw allows fluid to escape, the test allows manufacturers to catch and dispose of that product. Flaws may occur as easy-to-catch gross leaks or less obvious micro-leaks. In the past, leaks were discovered by pressurizing sealed components and submerging them. However, this is a highly limited technique as it is imprecise, time-consuming, subjective, and contaminates the component. Modern units use a combination of pressure chambers and vacuums, creating precision measurements that identify leaks and leak rates even on the micro-level.
Due to the vast variety of components that require leak testing, and the different needs associated with each part, there are a variety of leak tests available. Each test is optimized to different leak rates, and takes different amounts of time to perform, making method selection a key factor when leak testing parts.
The product is filled with a tracer gas, such as helium or hydrogen. A probe is then run around the outside of the product, checking for leaks. Probes may be handheld or robot-operated for automated testing. One benefit of this test is that it determines presence and location simultaneously.
This is essentially the opposite of a sniffing test. A vacuum is hooked up to the component, with a detector to monitor tracer gas. Gas is then sprayed across the surface of the product. If there is a leak, tracer gas will penetrate the product, setting off the detector.
This two-stage process facilitates testing for products that can not be connected directly to a leak detector. A product is placed in a pressurized container of tracer gas for a set amount of time. The product is then moved to a vacuum chamber with a detector. If gas penetrated the product in stage one, it will be detected in stage two.
In this test, the product is filled with tracer gas and placed in an accumulation chamber. Any gas that escapes through cracks is evenly distributed throughout the chamber by fans. A leak detector is then used to measure the leakage rate out of the product. This is important for products that must conform to strict leakage regulations, such as automotive AC systems and fuel tanks.
Rather than using a tracer gas, this test relies on measuring the leak rate of a component pressurized to a target measurement. The pressure is then cut off, and the drop in pressure over time is used to calculate if the product falls within an acceptable range.
Vacuum decay tests function as the opposite of a dresser decay test. Here, a component is placed in a vacuum chamber. Any leak out of the product will reduce the vacuum, and the change over time can be measured in detail. This makes the process ideal for detecting very small leaks.
Automated Leak Testing Machines
When deciding on how to implement leak testing into a production line, several factors must be taken into consideration. The test speed, sensitivity, and part volume will dictate the best method for implementing leak testing. This may occur either automatically with in-line testing, or manually, with machines assisting operators. For in-line leak inspection tests, pressure decay or vacuum decay systems are generally used in one of two orientations:
Linear Leak Testers
These test stations deliver a fully in-line process, integrating seamlessly into a conveyor system. Able to implement single- or multi-head testing as the need demands, linear leak testers offer high speed, high efficiency, and easy integration. However, these systems necessitate a trade-off between ease and specificity.
Rotary Leak Testers
Rotary leak testers are used for systems that require greater test time. These systems include a turntable which creates an additional loop in the production line. Test heads can move with the components on the turntable, allowing for more detailed measurements to take place. If a component does not meet specifications, it can be ejected at the end of the cycle. These machines offer an excellent combination of speed, precision, and 100% testing.
Leak Testing in the Automotive Industry
The internal functions of a car cover a wide range of intricate parts and processes, nearly all of which require some level of leak testing. This includes everything from the drivetrain and chassis to the cooling and safety systems. Some components, such as airbag cartridges, are subject to higher test sensitivities due to their life-saving function. Other components, like the engine block, are not subject to such high sensitivity.
Due to the consistently high demand for cars, manufacturers need a fast, reliable, and cost effective way to test parts before they get to the customer. Automation provides the tools to achieve 100% inspection without sacrificing efficiency. Additionally, automating measurement on a comparatively low-sensitivity process like coolant leak testers allows for process control. That way, if production begins to trend into dangerous territory, manufacturing changes can be made before catastrophic failures occur.
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