Large volume parts have a reputation for being challenging to leak test. Large volume parts include those from 15L to hundreds of litres. These parts are common in off-highway transportation, eMobility/EV, renewable energy sources, and more. Many factors contribute to challenges in leak testing these parts, including their size (large internal volume), handling issues, and stringent testing requirements, such as IP67 standards.
One of the challenges when it comes to leak testing large parts is managing and maximizing fill time during the leak test. Fill time issues can affect your repeatability test to test and raise the minimum observable leak rates, limiting the specification ranges possible with your test. Read on to learn how CTS solves the typical challenges with fill time to provide a repeatable, reliable leak test.
Why leak test fill time matters
Fill time refers to the time it takes to fill the internal volume of a part with air during a leak test. Fill time can become a problem with large volume parts because it can take too long to fill, extending overall cycle time past the needs of production. There can also be instrument design-related challenges, restrictions in fill/exhaust valves (including port sizes and seal designs), and more, which can provide restrictions and challenges in bringing a part up to pressure quickly and at a stable pressure—ultimately making it difficult to deliver a reliable, repeatable test.
Using a PID pressure controller to optimize fill time during large volume leak testing
CTS’ new Sentinel 128 LV model is built with capabilities that solve fill time issues when large part leak testing, using a PID pressure controller.
The Sentinel I28 LV instrument integrates a few key enhancements to meet the quick fill pressurization needs of testing large volume parts. In addition to offering enhanced air flow capacity and a proportional regulator to help reach target pressure precisely, the instrument is equipped with a PID controller (PID feedback loop) rather than a manual regulator.
A key benefit to using the PID feedback loop /controller is that it can be tuned (PID loop tuning) and filling pressure can be ‘programmed’ for different parts for better accuracy and repeatability.
To do this, the instrument stores different part designs and fill characteristics based on each individual part characteristic so you can program the instrument to react to a certain part size and/or part design and change that as you change over your test parameters from one test design to the next. This also allows for much higher repeatability from test to test.
How PID loop tuning delivers fast, stable fill pressurization during your leak test
PID loop tuning considers part stability and possible leak characteristics of the part keeping the flow path open to bring the part up to test pressure.
CTS offers three control parameters to allow different types of parts to be brought up to pressure quickly and in repeatable, controlled way: Proportional, Integral, Derivative.
- Proportional: Affecting the gain of the controller; the larger the error from the setpoint, the larger the proportional effect.
- Integral: Affects the acceleration toward the target pressure. This uses the magnitude and duration of the error to determine acceleration.
- Derivative: Controls the setting time and stability of the system, which is not often used due to other methods of filtration like low pass filters.
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Using Pressure Decay to Leak Test Large Volume Part Designs
Struggling with large part leak testing? Contact CTS!
While there are a variety of factors that come into play when designing a large part leak test and you need to carefully balance these contributing factors to ensure a repeatable test. For over 40 years, CTS has been helping across the globe overcome the challenges of large part leak testing—and we can help you too!
Our application engineers take the time to understand your part and applications to come up with the right technical solution and technology for your application. Using our industry-leading leak test technology, we can refine your test to reduce any affecting variables to deliver a reliable, repeatable, cost-effective test. Contact us today to get started!
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