Seal Quality Inspection with Airborne Ultrasound Technology
Airborne ultrasound is a referenced technology in the new USP <1207> Chapter Guidance as a deterministic test method for seal quality testing, is an ASTM Test Method F3004 and FDA Recognized Standard for seal quality integrity testing.
A pouch seal is a structural element that joins flat film material, and a component designed to close a pouch airtight. Traditional test methods e.g. peel strength or burst, can measure the joint strength of the seal, using destructive methods. However, this type of testing is often unreliable. A strong seal is not necessarily an airtight one, and the flow of gas or liquid through the seal (leak) is just one type of seal defect. As such, there is a fundamental challenge to any leak testing method, whether it is a fish tank-bubble, vacuum differential, or manual visual method, none of these methods detect non-leaking seal defects.
PTI’s proprietary Airborne Ultrasound technology is a non-destructive and non-invasive seal quality inspection method. It can be used for many material types such as Tyvek®, paper, foil, film, aluminum, plastic & poly. In this method, ultrasound waves are allowed to propagate through the package seal causing the reflection of sound waves. Defects are identified by measuring the variation of the reflected signal strength.
Seal Scan® and Seal Sensor
PTI's Seal-Scan® and Seal-Sensor utilize non-contact airborne ultrasonic testing technology. In order to use ultrasonic inspection effectively, it must be possible to place the seal in a direct line between a pair of transducers and move it (or move the transducers) along the seal. The ultrasound is transmitted and reflected at the transition from one media to the next. The greater the acoustic difference between mediums the more sound is reflected and the less sound transmitted through. The variation of the material thickness has only a minor effect.
Any material fold, foreign media inclusion and even a microscopic air gap between layers of pouch material causes a significant reflection, so the transmitted signal is lower. A small cut, abrasion or missing layer in a material causes less reflection, so the transmitted signal is higher. Therefore, the level of a signal received after passing through the seal is a function of the seal quality. Various types of defects, visible and invisible, leaking and non-leaking, process-related and random, are detectable.
Seal-Scan® technology has been proven in the field by several online and offline units installed. PTI's ability to adapt this technology into various production constraints and environments make it an excellent solution for flexible packaging systems. It has been established as one of the most effective methods for non-destructive testing of flexible packages. In 2013, airborne ultrasound technology was awarded the ASTM Test Method F3004-13. This test method was developed using PTI Seal Scan technology. This ASTM Test method is also a FDA Recognized Consensus Standard for seal quality inspection.
Advantages of PTI’s Seal Scan and Seal Sensor Method:
- Deterministic seal quality inspection method that produces quantitative results.
- This method works for any material type and combinations regardless of color, transparency, print, surface finish or porosity.
- Non-destructive and non-subjective test method that requires no sample preparation.
- Technology can be integrated for 100% online defect detection of the final pouch seal.
- Repeatable, reproducible and reliable results for seal quality inspection.
- Cost-effective solution for seal integrity testing and seal analysis that characterizes overall quality and uniformity of the seal.
Seal-Sensor Technology Integration
PTI works closely with industry leaders to integrate PTI’s Seal-Sensor inspection technology into their equipment for automated seal quality control on the production line.