Andy Macpherson, Industry Manager for Food & Beverage at Festo GB, offers advice to help system designers adhere to food safety guidelines while improving machine utilisation and performance.
Tip 3: Do not exhaust valves over the food zone
Exhausting a valve over the food zone is similar to holding a blow gun and blasting unfiltered air directly into the food or packaging. The only difference is that rather than the air coming directly from the compressor, air exhausted from the valve has also passed through the valves, into and out the cylinder, and back through the valve, which risks picking up contaminants along the way. Either mount the valves below the food/packaging zone or mount them above and duct the exhaust below the food zone.
Check valves are often overlooked in the food zone. While check valves can help improve machine cycle time because the air does not exhaust back to the valve, this means the air is exhausting over the food zone. If a check valve must be used, the exhaust should be ducted below the food zone.
Tip 4: Shorten tube length between valve and cylinder
One of the most important developments of the last several years has been machine mountable valve manifolds rated at IP69K washdown that, like washdown cylinders, conform to clean-design principles. The elimination of cracks and crevices reduces cleaning time for faster changeover and improved machine availability.
The new ability to move the manifold from the control panel to the machine in the food zone cylinder delivers advantages, not the least of which is energy savings. Figure 1 shows the dramatic energy cost saving of moving a manifold out of the panel and closer to the cylinder: 50% in this example.
Figure 1: Energy cost comparison between panel-mount and machine-mount manifolds
The shorter the tubing length between valve and cylinder, the faster and more repeatable the cylinder’s cycles. Faster cycles improve performance (see Figure 2). In many applications, such as filling, more precise cycles achieve better control of the process leading to higher consistency in product volume and weight and less waste.
The trend today is for smaller machines. Mounting valve manifolds on the machine allows control cabinets to be smaller or eliminated altogether, which can significantly reduce both cost and footprint. Moving the valve manifold outside of the control cabinet also eliminates pneumatic connections installed into the wall of the control cabinet, lowering machining costs in materials and labour as well as reducing the number of components required.
Figure 2: Relationship between tube length and cycle rates - shorter tubing results in higher cycle rates
There are other design considerations for food and beverage packaging applications such as selecting tubing materials that withstand harsh chemicals and resist plastic transfer to food. Hydrolysis-resistant polyurethane (PUN-H) and Polytetrafluoroethylene (PTFEN) tubing are ideally suited for use in the food and beverage industries. Both resist cleaning agents, microbes, and hydrolysis and are FDA compliant. PUN-H is more flexible and economical, while PTFEN is ideal for the harshest environments.
Designers can use one of the many free online tools offered by Festo to size the pneumatic system appropriately so that the system runs as energy efficiently as possible. And of course, specifying air filtration units to achieve 0.01 µm filter with 99.9999% efficiency is a must. It is the five tips, however, that lay the foundation for compliance, utilisation, and performance in food and beverage packaging applications.