Large volume parts can be challenging to leak test due to their size, design/materials, handling issues, and often stringent test requirements. In order to meet high production targets and low leak rate measurement requirements, many manufacturers choose tracer gas leak testing techniques for their large part leak testing. However, tracer gas leak testing can come with a higher cost due to higher equipment costs and the ongoing cost of the gas used in the testing process (which can vary depending on the type of tracer gas used).
For manufacturers looking for a more cost-effective large part leak testing solution, particularly for lower production rate programs and lower cost equipment, CTS has a solution—the new Sentinel I28 LV large volume air leak testing model.
Challenges of using traditional air leak testers for large volume leak testing
Historically, some manufacturers may have been hesitant to use air leak testing technologies to test large volume parts due to the potential problems posed by their design and testing requirements, including:
These issues can affect your repeatability and raise the minimum observable leak rates, limiting the specification ranges possible with your test—but CTS solves these problems. Read on to learn how the Sentinel I28 LV (large volume leak tester model) is built with capabilities that solve these challenges, offering a unique, cost-effective air leak testing solution for leak testing large parts.
Challenge: Fill time
Fill time will affect your overall cycle time, so it must be optimized in order to keep cycle time down. Factors that can cause a longer fill time when leak testing include instrument-related design and functional challenges, restrictions in fill/exhaust valves, part design, port sizes and seal designs, and more. All of these factors can pose restrictions and challenges in bringing a part up to a stable pressure quickly.
How we overcome it: The Sentinel I28 LV is built with quick fill pressurization capability to combat the above issues, using an enhanced fill kit for improved air flow capacity, a proportional regulator to reach precise target pressure, a PID controller to better regulate pressure, and PID loop tuning for better accuracy and repeatability.
Challenge: Test pressure control
Test pressure in large volume parts can be inconsistent from part-to-part during the test cycle due to the complications in controlling the pressure, and adiabatic thermal effects that make it harder for large parts to stabilize. These factors greatly impact the repeatability of your test from part to part.
How we overcome it: The Sentinel I28 measurement system for large volume leak testing is built with Target Pressure Correction technology to more accurately measure and control pressure variance during the Fill and Stabilize periods of the test. To achieve this, the leak test instrument collects all the data points measured during the test cycle and uses a linear regression algorithm to calculate loss, offering precision measurements of small pressure changes over a long period of time. By combining target pressure correction into this algorithm, noise commonly measured over long test cycle times is removed for more reliable pressure control.
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Challenge: Low pressure differential
Due to a variety of factors, including part flex present in many large part designs and atmospheric pressure fluctuations, large parts must be tested at low pressures. Unfortunately, these low pressures are highly impacted by atmospheric pressure. Atmosphere pressure brings noise into the system, making it very hard to differentiate a small pressure loss on a large surface compared to the noise brought in from ambient pressure changes and environmental drift.
How we overcome it: CTS has integrated Ambient Pressure Correction into the Sentinel I28 LV instrument to help mitigate the influence of atmosphere while collecting test measurements. Ambient Pressure Correction uses a secondary pressure sensor to measure ambient pressure outside the part while measuring internal part pressure changes. The leak tester automatically brings those two measurements together and includes both in a Correction Factor, resulting in significantly higher repeatability.
Challenge: Large, flexible areas in part designs
Many large volume parts are designed with flexibility, including sheet metal covers, plastic, and other thin wall structures. This creates expansion and contraction that amplify atmospheric pressure effects, making it difficult to get a reliable, repeatable leak test.
How we overcome it: The Sentinel I28 LV combats problems caused by large volume parts by applying a Batch Calibration technique. This approach is different from standard pressure decay calibration, which uses standard two-point calibration. Instead, this process calibrates using a master, known non-leaking part and a known leak rate from a leak standard built into it to identify the DP. This technique eliminates incorrect calibrations, reduces production cycle variances, and improves testing accuracy.
Have questions about large part leak testing?
Whether you are looking for an air leak testing solution or a tracer gas leak testing solution, the experts at CTS will help you design an accurate, repeatable leak test for large volume parts. Our application engineers take the time to understand your part and applications, including leak rates and the variables affecting the part, and then come up with the right technical solution and technology for your application.