Air Under Water (AUW)
Also known as the “Bubble Test” / Dye Penetrant Leak Test
AUW, also referred to as the “bubble test”, may be okay for medium and large leaks, but is poor for SPC and correlation to other leak test methods is almost impossible. AUW can be used to detect point of medium sized leaks, not to quantify the leak rate. Do not use this method at low pressure (e.g: 15 psig) and tight leak requirements.
The mechanisms of air transport into water and bubble formation as well as other sources of air bubbles (leaks from fixtures, bubbles from air trapped on surfaces, etc.) are biased and prevent reliable leak detections.
Using water to detect leaks is operator and labor intensive as well as set up dependent. Furthermore, the cost of drying the part after air under water test is an ongoing operation cost and product quality risk. AUW test equipment must maintain clear water, including water cleaning systems and expensive lighting systems. Therefore, a well built AUW test system costs as much as ATC’s micro-flow based test systems.
ATC’s Micro-Flow technology has replaced many AUW systems. The IGLS micro-flow sensor is part of an objective instrument, operator independent freeing the operator to perform other tasks during leak testing, and will provide a more accurate and faster measurement (for the same capability) than AUW. Additionally, with the IGLS there is no need to place the test parts under water nor the need to dry those parts after testing. Consult ATC if you are looking to upgrade or replace your AUW leak test system.