Why Helium Leak Test and TDLAS are complementary technologies

Complementary Leak Detection Technologies: Helium Leak Test and TDLAS

1. Introduction

Leak detection is crucial across various industries, including pharmaceuticals, automotive, and aerospace, to ensure the safety, quality, and efficacy of products. Leaks can lead to contamination, safety risks, and degradation. Two primary methods for leak detection are the Helium Leak Test, known for its precision and sensitivity, and Tunable Diode Laser Absorption Spectroscopy (TDLAS) with CO2 as a tracer gas. Although these technologies operate differently, they complement each other by addressing various leak detection challenges.

2. Helium Leak Test

The Helium Leak Test uses mass spectrometry to detect helium molecules, utilizing helium's inertness and low natural abundance to enhance detection sensitivity. This method includes:

• Vacuum Method: Involves placing the item in a vacuum chamber to detect helium that has penetrated through leaks.
• Sniffing Method: Uses a handheld detector to identify leaks by sniffing helium around the item.

Advantages:

• High Sensitivity: Capable of detecting very small leaks with precision.
• Immediate Results: Provides quick identification and assessment of defects.
• Low Helium Consumption: In pharmaceutical testing, the helium required is minimal due to small container sizes, mitigating cost concerns.

Limitations:

·????? Complex and Time-Consuming Setup in vacuum mode: Requires specialized equipment and procedures. Containers must be fitted into sealing holders and be subjected to helium exposure. This process involves either pre-filling containers with helium or modifying them to allow helium entry which in any case is destructive:

If not prefilled containers need to be drilled or cut to introduce helium, which destroys them.

Recommended Use Cases:

• Defining Defect Size: Ideal for precise quantification of defects, especially in critical applications as i.e. understanding the inherent package integrity
• Instant Results: Suitable for scenarios needing immediate leak detection.

3. TDLAS with CO2 as Tracer Gas

TDLAS utilizes a tunable laser to scan the absorption spectrum of CO2, allowing for precise measurement of gas concentrations. CO2 is selected for its non-toxic nature, low cost, and distinctive absorption properties. TDLAS, though relatively new in pharmaceutical leak detection, is gaining traction due to its robustness and sensitivity.

Advantages:

• Non-invasive and Non-destructive: Detects leaks without altering or damaging the container, preserving product integrity.
• Cost-effective for Large Batches: Despite the higher initial equipment cost, TDLAS is efficient for large sample sizes. Containers are exposed to CO2 for a predetermined period, with individual measurements taking only seconds, making the process both time-efficient and cost-effective.
• Versatility: Can be adapted to various container sizes and shapes, suitable for diverse production environments.

Limitations:

• Waiting Time for CO2 Diffusion: Requires a waiting period for CO2 to diffuse into defects, which can delay detection. This can be mitigated by using CO2 at increased levels after overpressure exposure.
• Sensitivity Limitations: While effective, TDLAS may not match the sensitivity of helium methods for extremely fine leaks. However, its sensitivity is generally sufficient for most pharmaceutical applications, especially with pressure and vacuum cycles
• Not Necessarily Quantitative: Defects can be found but not easily quantified. Here, the Helium Leak Test has a clear advantage.

Our use Cases:

• Testing Large Sample Sizes: Ideal for high-throughput testing where many containers need to be screened quickly and non-destructively. Automated systems streamline this process.
• Sensitive and Automated Testing: Suitable for applications requiring sensitive detection without damaging samples.

4. Case Study: Comparative Use of Helium Leak Test and TDLAS with CO2

To illustrate the practical application of both technologies, we present a comparative case study:

Case Study Overview:

• Helium Leak Test: We tested individual 2R pharmaceutical vials, each with a defects created by a capillary of known diameter and length. Vials were placed on a vacuum adapter, and helium was sprayed directly at the defect to enable a leak detection similar to the sniffing method. This process required less complex handling and was less time-consuming, particularly useful for testing multiple vials. Nevertheless, it is much slower than TDLAS. A small number of containers was tested quantitatively, with a dedicate holder, as described above
• TDLAS with CO2: A batch of 20 containers, each with a similar capillary defect, was exposed to CO2 in a pressure chamber for a short period. Following exposure, the containers were measured using TDLAS. The process allowed for rapid measurement of each container, with results available in seconds.

Findings:

• The Helium Leak Test provided detailed information on the defect, with gas flow rates validating our calculated values for the capillary.
• TDLAS with CO2 showed that all containers with known defects had very similar CO2ingress levels. The differences in ingressed CO2 were minimal, in one example ranging from 3.96% to 4.19% across the 20 containers, demonstrating the method's high consistency and accuracy.

Comparability of both technologies:

Dr. Christian Proff from Hoffmann-La Roche has recently posted information about the comparability of both technologies. He noted that under controlled conditions, both technologies can deliver comparable results. However, since CO2 concentration and leak rate are not directly proportional, additional information (such as CO2 pressure and container dimensions) is required for an accurate comparison. Please check out his post if you are interested in more detailed information and it you want to find his recent publication.

5. Conclusion

Both Helium Leak Testing and TDLAS with CO2 offer unique advantages tailored to different needs. The Helium Leak Test provides high sensitivity and immediate results, making it ideal for precise defect quantification. TDLAS with CO2offers a non-invasive, efficient solution for large-scale testing with cost-effective and rapid measurement capabilities. By leveraging the strengths of each technology, industries can optimize their leak detection processes, ensuring high standards of safety and quality.

Note: This text is not intended to provide a comprehensive overview of the technologies but to highlight some of the capabilities of the two technologies we offer at be integral GmbH. For instance, the text does not include the capabilities of both technologies for providing information in cold storage CCIT at -80°C and below. The decision to exclude these aspects was made to keep the article concise and focused on our latest customer project. We created different defects for our customer and quality-controlled them using both tests, driven also by our curiosity as helium leak testing is a recent addition to our lab. Furthermore, this article does not make any comment on Oxygen TDLAS, another important technology we offer in our lab. I.e. for lyo containers there is typically no alternative available.

If you seek more detailed insights or have questions about cold storage CCIT, please do not hesitate to ask.

A special thanks goes to Pfeiffer Vacuum to offer a generous trial of their Helium leak testing device (see my previous post)