Leak Testing- An Automotive Perspective.
The continuous innovation in the automotive industry has ramped up in recent years. Demands for fuel efficiency and hybrid designs have sent automotive design engineers back to the drawing boards for components that had been somewhat static in years’ past. Protecting powertrain and all body electronics from exposures has renewed attention to the best leak testing products to be had—and whether a particular leak tester that had long been used in a production line is optimal for today’s designs.
The laws of physics that determine the best match leak test methods have not changed. What has changed is the technology available—both the leak testers and the automation for full or semi-automated assembly and leak test machinery—that make one or another leak tester the best match technology.
Some in the automotive industry, as in others, are loathe to trade up to faster and more accurate leak testing technology because of the time-worn adage—“If it ain’t broke don’t fix it.” However, the calculation of return-on-investments for newer leak detectors is a relatively straightforward proposition. In fact, reputable manufacturers of leak testing systems also, or should, consider keeping you apprised of technology options as part of the cradle-to-grave support that is your due.
First things first—be prepared to discuss your application with a leak testing specialist in detail. Figure 1 shows how different classes of leak testers match up to these requirements.
This is the minimum of what you need to be prepared to discuss with your leak testing technology specialist:
- Physical parameters
- What is the internal volume of the part to be tested? At which test pressure(s)? At what leak or flow rate specifications? What is the part made of? How much give or flexibility is in the product material?
- Details of how the part or device functions
- What type environment will the part or device be used in? Is it a device that is operated in a controlled environment, a pressurized room, or operated by a patient in a home or other uncontrolled situation?
- Leak Testing Environment
- Cleanliness does impact the way in which a leak tester enclosure needs to be chosen. Will testing be done in a clean room environment for electronic parts assembly or an assembly plant where NEMA enclosures are required?
- Stage of Manufacturing
- When in the assembly process will the test take place? Is it directly after a glue weld or molding process such that the part to be tested where temperature compensation will need to be figured in?
- Production targets
- What is the expected throughput of your manufacturing operation? In turn, this will help determine the optimal test cycle targets per component at your desired production rate—and the options for numbers of testing stations, test channels and/or test sensors.
- Range of NDT tests required
- Many automotive components need a combination of related NDT tests—from flow, to leak, to burst, to occlusion, crack pressures, sealed component tests and more. Similarly, many components have numerous sub-assemblies that need to be tested.
Secondly, always give priority to consulting with your leak testing specialist in one or another manner that affords detailed visual inspection and in some cases dissection of the device. At USON we take it as a given that in the many patent-pending automotive designs that we are asked to create test systems for cannot leave a manufacturer’s premises. Videoconferencing now makes that moot. It is always recommended for that well referenced “picture is worth a thousand words” return. Eyeball to eyeball discussions never hurt either. What these type of video consultations do is enable precise recommendations for seals or other fixturing in automated machinery that matches the geometry, flex and other physical characteristics that bear on testing efficiencies.
Third, make sure that your discussions include detailed analyses of whether parts of components can be leak tested simultaneously or whether the sequence of tests required makes asynchronous multi-channel leak testing a better match. This is not simply a matter of looking at lower costs, though that is one inevitable byproduct when you drill into this level of detail. It is also a matter of test accuracies afforded by sensors that are tuned to different pressures and also the cycle time for tests with particular sensors. Multi-channel and multi-sensor leak testers are the types where the most recent innovations have occurred.
As an example, consider today’s transmission case. In these types of castings the high pressure ports, low pressure ports, and main case operate at different pressures and different allowable leak rates. If you use a leak tester with multiple sensors scaled to operate at maximum efficiency at these distinct pressures you create a more efficient system, which allows for concurrent testing of non-adjacent cavities as well as monitoring adjacent passages for common wall leakage. As the transmission case moves along the build process into assembly, electrical connections are made and seals installed. At that stage, the multiple sensors on your leak tester will allow you to isolate connector and seal leaks by monitoring specific locations while the main assembly is tested.
Word to the wise—upfront cost of any leak detector is not the same as your real testing costs. Cycle times factor in and in turn this goes back to the sensitivity and pressures to which the sensors being used are tuned. Testing costs per channel and testing costs per sensor are factors that create significant forks in the purchasing decision trees.
Fourth, there is wide variety amongst leak testers in terms of their I/O sophistication and the number of test steps that can be programmed. If flexibility is important there are leak testers that have been designed with that requirement as core. Similarly, some leak detection equipment has numerous data communication options. These types of factors are always important but are essential to blueprint in detail when you enlist your leak detector manufacturer to provide a total turnkey leak test solution.
Last, but certainly not least, is consideration of the configurability of your leak tester. Today’s technology improvements allow you to pick leak testers with totally customizable pneumatics, test methods, data communications and storage. It may sound hyperbolic, but if you do the math just considering a tester capable of more than a dozen type NDT tests in any order you realize quickly that you are talking about nearly half a billion permutations of how such a flexible leak tester can be put to use. That means you are really getting best match technology not just for the application at hand today but for the widgets your team has not yet even put on the drawing board.
Perhaps the biggest mistake we see is someone taking an antiquated leak tester that was built with one pressure and sensor range in mind for an earlier generation automotive component or product and using it for a new application. Yes, it will work in some fashion but certainly not optimally. Usually the regulators and flow sensor ranges are just off and the tester more or less limps to the finish line during every test cycle.
Is your leak tester out of date? It usually only takes 48 hours to get a no-cost detailed applications analysis to answer that question in great detail. Leak test technology may have changed but good old-fashioned customer service has not.