As experts in the industry, we take leak testing education very seriously. Sharing our 60 years of expertise with customers is one aspect of Uson we feel is one of the most import parts of what we do. Although much of modern leak testing was literally born out of rocket science, it’s not "rocket science" as they say. The industry has come a long way since automated leak testing was established. Nevertheless, it still sounds so simple – just fill something with air or gas and monitor the pressure change or detect the escaping gas with some sort of mechanism. While it may sound simple, and certainly the evolution of sophisticated and powerful automated leak testing equipment has simplified the process for the end user, there are critical mistakes that can compromise your entire process. We've identified 4 automated leak testing mistakes you could be making and how to fix them.
#1 - Using unfiltered air.
Unless the air that is used to pressurize the part is clean and dry, it is not a question of IF your leak tester will be damaged. It is a question of WHEN. Some people might be surprised how dirty the air in factories can be before we even begin to notice a smell, taste or other physical reaction. I remember visiting a wheel bearing plant where literally everything touched was covered in a film of oil. I’ve seen leak testers literally dripping with oil when they arrived at our service department. One instrument maker mounted PCBs vertically so that oil mist dripped off and did not pool on the boards. Metal particles in the air or other trash can also destroy sensitive transducers and precision valves. Factoring in the need for clean, dry air at the front-end of your planning will save you thousands in repair and replacement costs in the long run.
#2 - Selecting the wrong tester for the job.
Not all leak testers are equal. I’m not referring to differences between brands or models. Leak testers can look identical on the outside but inside is an entirely different matter. If you have multiple testers of the same model in your inventory, but unless you know the build specifications of the tester, or what type of leak test they were configured to perform and on what part, you can't assume they will be an appropriate tester for the job. This does not necessarily mean they can't be modified to be the right tester for the job. Often they can be reprogrammed to perform similar tests within the boundaries of the transducer, regulator and valve(s). Venturing outside the boundaries is a different matter. One customer had well over a hundred testers that they would periodically send back to be serviced and recalibrated according to a PM schedule they had created. While those testers were away they pulled testers out of a reserve pool and used them in place of the testers that had been sent in. The problem was nobody was taking account of the fact that the reserve pool testers sometimes did not have the correct configuration. When that happens it’s entirely possible to test products and get results which “pass” but which could have been failures. I think you can see where we are going with this. If you don't keep local records of tester specifications, as simple phone call to the manufacturer with the serial number of the tester(s) in question will allow you to assess if it is the best choice for the job.
#3 - Choosing the wrong leak test technique.
The fundamental starting point of any leak testing process is choosing a test technique. To do this you must consider the part volume, the desirable reject criteria, the intended function of the part or assembly, the physical properties of the part materials and the desired throughput. You might choose from simple pressure decay, differential pressure measurement, mass flow, laminar flow, helium or hydrogen trace gas detection or a combination. Sometimes it may be necessary to compromise, say, throughput for sensitivity. Large volume parts take longer to test. This is an easy problem to fix – you could, for example, add more testers. But what if you decide to fly in the face of physics? This decision could prove detrimental and result in putting out defective products. And worse, you probably won’t know until after they're in service and the customer complaints start rolling-in. If you are unsure which test method is the best choice for your application, reach out to experts for help.
#4 - Take care of the surroundings.
Things can go horribly wrong, possibly in a very career limiting kind of way, if you don't pay attention to the testing environment. For example, you've decided to do a final assembly test using a helium trace gas sniffer. What happens when you get a gross leaking product and a lot of helium escapes? You end up with temporarily high background levels of helium which will confuse the leak tester. So, consider at the station design phase how the escaped helium can be relocated or recovered.
Another often overlooked environmental factor that can negatively impact your leak testing process is changes in ambient temperature. Many automotive component plants are located in countries which have extreme temperature fluctuations – hot during the day and cool at night. The plants are often not environmentally controlled. I remember a colleague showing me a picture of a temperature gauge showing zero centigrade next to the machine he was trying to troubleshoot. I will abstain from stating the obvious here.
We've identified these 4 mistakes as being of the most common, but we want to know what you think! Do you agree? Let us know!
Our team of experts have extensive experience in medical device, automotive, EV battery, packaging and industrial leak testing applications. We've helped thousands of manufacturers with complex leak testing challenges, and we can help you too! Contact us today!