PC-MAY23-PG22-23.1_Layout 1 11/05/2023 09:11 Page 22
FOOD & BEVERAGE FIVE WAYS TO OPTIMISE PNEUMATIC SYSTEMS
cleaning cannot be achieved. These cylinders feature high-gloss surface finishes, which are essential for components in the food zone. High gloss reduces microbial contamination. FDA-approved seals and NSF-H1 grease protect against unintentional adulteration of the food product. Be sure the cylinders have dry run seals for long service life. Other key qualities for these cylinders include machine parts that resist corrosion, are mechanically and chemically stable, and are rigorously designed to conform to GMP criteria. A cylinder’s self-adjusting end position cushioning system should be constructed without adjusting screws.
Tip 3: Do not exhaust valves over the food
The MPA-C manifold, top centre, is installed in a difficult to adjust position. Proportional pressure regulators, lower left, plumbed to the manifold, solve the adjustment problem
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
Andy Macpherson, Industry Manager for Food & Beverage at Festo GB, offers advice to help system designers adhere to food safety guidelines while improving machine performance in packaging applications
L
et’s begin with a fundamental question: why apply pneumatic automation in the food zone instead of electric automation? Pneumatic automation remains a key solution because of its lower relative cost compared to electric automation in food and beverage applications. In the food and splash zones, components must withstand harsh cleaning processes; even in dry cleaning applications, they still need to be cleanable. Moisture, chemicals, and electronics do not mix well.
While electric automation can and does exist in food and beverage packaging automation, the cost of protecting the electronics and motor drives is significant. When electrics are applied, they tend to be used selectively. Furthermore, components in many food applications have shorter operational lives due to the harsh environment, which means parts need replacing sooner. Replacing a less expensive pneumatic actuator keeps operational costs lower. Pneumatic automation is the predominant solution for its lowest total lifecycle cost.
Taken together, the following tips will help Tubing length 6 ft
you achieve three important design objectives:
• Conformance to food safety and hygienic design guidelines
• Improved machine utilisation • Increased machine performance Tip 1: Standardise on metric pneumatic systems: Tubing and fittings for metric cylinders use G-thread fittings that have parallel threads. Parallel threads seal flush to a gasket and eliminate exposed crevices. Utilising G-threads with metric tubing is the best option for food safety applications. Tapered thread fittings pose a contamination risk because they seal by wedging threads together and require sealing tape. G-threads lower the risk of
contamination and clean faster, which equals greater machine availability.
Figure 1: Energy cost comparison between panel-mount and machine-mount manifolds Scenario
Manifold in a panel Machine Mounted Manifold 20 ft
Tubing volume 75 cm3 Cylinder volume 25 cm3 Total volume/cycle 200 cm3 Annual energy cost* $85.43
23 cm3 25 cm3 96 cm3 $41.01
*Assumptions: 20 cycles/min, 16 hours/day, 300 days/year, 6 bar pressure, $0.35/1000 SCF
Tip 2: Select a clean-design cylinder family: Instead of designing with generic cylinders, begin by identifying a cylinder family that was created for washdown and cleanability in food and beverage applications. Then design the pneumatic automation system around that family. Food and beverage cylinders are intended to be easy and fast to clean. They have large radii that do not pose a hygiene risk because they promote high flow velocities of the cleaning agents and disinfectants. There are no tight spaces where required
22 MAY 2023 | PROCESS & CONTROL
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, the air is actually 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 (left) shows the dramatic energy cost saving of moving a manifold out of the panel and closer to the cylinder: 50% in this example. 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
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