Use of Linux system architecture to reinvent glass container pressure testing and volume measurement

Agr International, Inc. recently unveiled an all-new Sampling Pressure Tester, the SPT2, which pushes the boundaries of throughput, pressure generation, handling versatility and measurement precision to levels previously thought impossible.  In this product, Agr has married the rugged and reliable performance of previous Agr pressure testing systems with the latest pressure and volume measurement technology.  This combination has resulted in a device that can perform highly accurate, hands-free pressure and volume tests on bottles at a rate of up to 300 bottles per hour.

The Agr SPT2 is an automated testing station designed to provide critical pressure strength and volume performance data for glass containers, on a sampling basis on the production floor. Integrated into the production line, it can automatically test and collect pressure and volume data on bottles selected for sampling, without operator intervention, on a 24/7 basis.

At the heart of the SPT2 is an advanced, controlled-velocity pressure generation system that can pressurize containers up to 1000 psi (1 minute equivalent) while providing extremely accurate and controlled pressurization throughout the testing process.  The pressure system is designed specifically to meet the rigid testing requirements defined in ASTM C-147, Standard Test Method for Internal Pressure Strength of Glass Containers, and ISO 7458, where a constant-rate of increasing pressure must be applied to the bottle in a very precise and defined manner. The SPT2 meets and exceeds the requirement by offering an un-matched level of precision in the control and application of pressure, resulting in the highest accuracy and repeatability of test data possible.

The SPT2 incorporates a Linux-based architecture and operating system to manage the continuous, multi-function operations of this system.  Linux’s ability to run efficiently on embedded computing platforms is an advantage for the elevated temperatures of the factory-floor environment and 24/7 operation of the SPT2. Linux was chosen for this system because of its efficiency, stability, security and long-term availability.

One of the many features of the SPT2 is an optional volume measurement system.  The volume measurement system utilizes positive-displacement technology that makes it possible to fill at any rate, without compromising accuracy or repeatability. This method ensures rapid fill and precise measurement while overcoming the problems and inaccuracies associated with flow-meter based systems, the complexity of gravimetric products and variability due to water density. With this approach, measurement precision is not affected by water quality, container shape or rate of fill, regardless of the size and volume of the container.  The positive-displacement filling technique, in combination with a high-precision fill height sensor, makes it possible to deliver defined volume and fill measurements to a high level of accuracy at any point within the process. Final test data can be reported as volume at defined fill point, fill height at defined volume, brimful volume or any combination of these.  

To ensure optimal throughput, the SPT2 employs a two-station design with concurrent volume measurement and pressure testing operations.  A servo-controlled positioning system provides for optimal bottle travel and placement through the system. Continuous bottle management and closed-loop monitoring of all processes facilitate the most efficient bottle processing and throughput.

An added feature of this system is the ability of the infeed height and finish gripper to adjust “dynamically” to accommodate bottles of different sizes or from multiple production lines.  This capability makes it possible to perform in-process job changes to test bottles from different manufacturing lines, or hand-feed a set of bottles as required, without the need to stop and reconfigure the system. 

The SPT2, along with the recently introduced Dimensional Sampling Gauge, reflects a new spirit of innovation at Agr International.  According to Robert Cowden, Agr’s Chief Operating Officer, “We challenged the project team to dramatically increase the value-added with the new product design.  The project team exceeded our expectations with the new features and performance of the SPT2, including throughput, measurement precision, and flexible handling, while achieving a durable industrial design.”

The SPT2 is designed to operate seamlessly with Agr’s OmniLab automated measurement system.  When integrated with the OmniLab system, pressure and volume as well as dimension, weight and thickness data can be correlated into one report. The SPT2 can be configured on a sampling line and work directly with most commercial plant-wide process management systems such as those offered by Vertech, EKF and other proprietary information systems.

The SPT2 is the latest generation in a long line of automated pressure testing systems supplied by Agr for the glass container manufacturing industry. Agr’s automated pressure testing stations date back to 1979 when Agr first pioneered the concept of automatically sampling containers from the production line and testing them for pressure strength on a regularly scheduled basis.  This development made it possible to continuously monitor the pressure strength of bottles being produced and provide a statistically significant level of sampling that is not possible with laboratory-based testing. Over the past 35 years Agr has supplied over 1,000 pressure testing units to the global glass container industry. The SPT2 takes this one step further with its high throughput and its ability to provide precision volume measurements as well