Time-pressure systems are designed to dispense using a pressurized product supply and timed valve openings. A portion of the product path from the supply manifold to the filling nozzles is made of elastomeric tubing, which is used in association with an automatic tubing-pinch mechanism to create the valve.
The use of disposable tubing seems to make this system a good candidate for single use. This is not the case though. Time-pressure systems often use a small surge tank for product supply, and this tank must be pressurized to 10 psig or more. Replacing this tank with a bag would require that the bag be pressurized beyond its normal design pressure. There is currently no good solution for pressurization of a surge-bag system for use with time-pressure filling.
Other Technical Hurdles Exist
Ensuring that a single-use system dispenses at high speeds and is also durable enough for commercial use requires rigorous testing. No dosing system is appropriate for commercial use without proof of accuracy and precision. The run duration of commercial systems is typically a week or more, involving 500,000–1,000,000 dosing cycles per station. This is well beyond the design specification of existing single-use dosing systems.
The plastic filling needle limits all single-use, presterilized dosing systems at this time. Current plastic needles are not designed for commercial filling operations. Most are too wide to penetrate small containers and/or too short to perform bottom-up filling. Bottom-up filling, where the filling needle penetrates the container and is drawn out during dosing, is common with high-speed filling to reduce product splash and foaming.
In addition, plastic needles are not shaped to fit correctly within needle holders on common commercial filling systems, requiring custom fixtures to use them on existing machines.
High-speed filling requires needles made to tight tolerances, particularly the needle diameter, which influences dosing accuracy and precision. As high-speed needles travel during and after dispensing, needle drip between doses has to be eliminated. Precise needle opening size and opening shape is also required. Substituting plastic needles with ones made from stainless steel can solve most of these issues, but this is too expensive for single-use assemblies.
There are tremendous advantages to the use of single-use, presterilized dosing systems for commercial filling operations. Increased processing efficiency through the elimination of preparative steps like CIP and SIP, reduction of validation efforts including elimination of cleaning validation, containment of toxic products, and matching existing single-use upstream processes are all compelling arguments for these systems for product-filling operations. Significant technical achievements, however, must be realized before a system can be scaled for high-speed filling operations.
Jeff Jackson is director of product management, North American
pharmaceutical operations, at Bosch Packaging Technology.
Web: www.boschpackaging.com. Phone: (763) 493-6133. E-mail: Jeff.Jackson@boschpackaging.com