Using Microbe- and Hydrolysis-Resistant Pneumatic Tubing to Simplify Automation and Robotics in Food Processing

Using pneumatic tubing in food processing automation and robotics presents significant challenges related to hygiene, durability, performance, and maintenance. Microbe- and hydrolysis-resistant pneumatic tubing that’s also kink-resistant can simplify and speed up the installation of automation equipment and robotics, and improve long-term reliability.

Other desirable features of pneumatic tubing in food processing applications include excellent flexibility, suitability for use in energy chains, push-in fittings that ease installation and disassembly for reconfiguration and maintenance, and availability in various colors, including transparent tubing for monitoring system conditions.

The tubing materials must be highly resistant to the chemical sanitizers and high-pressure, high-temperature washdowns used in food processing, and they need to meet all related FDA requirements.

This article details how PUN-H pneumatic tubing from Festo meets the numerous demands for automation equipment and robotics in the food processing industry.

Made with modified polyurethane, PUN-H pneumatic tubing is highly versatile and can support small bending radii, making it ideal for compact installations. Polyurethane is inherently resistant to hydrolysis and is FDA certified for use in food production processes.

The flexibility of PUN-H makes it suitable for moving parts, such as energy chains, as well as general pneumatic applications in the biotech, pharmaceutical, and cosmetics industries, as well as standard uses in the automotive, electronics, and chemical industries.

PUN-H tubing is available in a variety of colors, as well as a transparent version (Figure 1). Standard colors include blue, blue/black, yellow, green, natural, red, silver, and black. It’s also offered in translucent versions, including blue, yellow, green, and black.

Figure 1: Festo PUN-H pneumatic tubing is available in a variety of colors and transparent. (Image source: Festo)

Black PUN-H tubing is UV-resistant and suitable for outdoor applications. The transparent tubing provides machine operators with immediate insight into the quality of the compressed air. Contaminants like particles, water, or oil are easy to spot. Condensation, for example, indicates that moisture is in the system. Moisture is not acceptable in most food processing safety standards. It can also reduce the operating life of pneumatic components.

PUN-H tubing is designed to carry compressed air, vacuum, and water. It has an operating temperature range of -35°C to +60°C. Its operating pressure range varies with the temperature. The maximum pressure rating of 1.0 MPa (10 bar / 145 psi) applies for temperatures between -35°C and +30 °C. In the high-temperature range from +30°C to +60°C, the maximum pressure specification decreases to 0.6 MPa (6 bar / 87 psi).

It's available in nine sizes with outer diameters (ODs) from 2 to 16 mm and delivered on reels that vary in length depending on the OD of the tubing. For example, model PUN-H-3X0,5-BL-500 has an OD of 3 mm and is delivered in a standard length of 500 meters. Model PUN-H-12X2-SW-200 has an OD of 12 mm and is delivered in a standard length of 200 meters. DigiKey can custom-cut shorter tubing lengths.

The use of a modified polyurethane material is the source of the high flexibility and elasticity of PUN-H tubing. It can bend more than other materials without creasing or permanently deforming.

The inherent flexibility of PUN-H makes it easy to install in tight spaces, reducing machine and installation sizes. The material is resistant to hydrolysis, preventing cracking and ensuring durability and reliable operation. The microbial resistance of the FDA-listed food-grade modified polyurethane, combined with its superior resistance to cleaning agents, makes it well-suited for food processing and packaging systems, where frequent contact with water can occur.

Installation considerations

A rule of thumb for pneumatic tubing installations is to ensure the tube is only as long as necessary and as short as possible, thereby preventing it from being stretched. Additionally, tubing diameters that are either too large or too small, as well as bending radii that are too small, can result in lower flow rates.

Different sizes of tubes can support varying flow rates and different bend radii. It’s essential to match the tube size to the specific application and installation requirements to ensure proper system operation.

When bending PUN-H tubing, there are two critical factors: the flow-relevant bending radius (Rd) and the minimum bending radius (Rmin). The distinction is important when designing machines using PUN-H tubing. Rmin relates to the structural integrity of the tubing, and Rd corresponds to the flow rates it can support.

Festo has developed specific tests for Rd and Rmin (Figure 2):

• To measure Rd, the tube is bent until a 5% flattening of the outer diameter (O.D.) occurs. There is no reduction in the flow rate until the Rd is reached.
• To measure Rmin, a movable plate is used to bend the tube until a kink forms, which corresponds to the Rmin value, resulting in a considerable reduction in flow.

Figure 2: Tubing movements used to determine Rd (left) and Rmin (right) (Image source: Festo)

Making connections

The QS push-in fittings (connectors) for PUN-H pneumatic tubing include an internal collet with gripping teeth that clamp onto the tubing to secure the connection. Pushing the quick-release mechanism disengages the gripping mechanism, allowing the tube to be inserted or removed.

Both the fitting and the tubing can be reused multiple times. Some models of fittings have push-in connections on one side and threaded connections on the other.

QS fittings are available in various geometries, including straight, T-shaped, Y-shaped, and angled versions, to suit specific system requirements. Some examples include:

• QS-6, push-in straight fitting (Figure 3)
• QST-1/8-4, push-in T fitting
• QSYL-1/4-10, push-in Y fitting
• QSML-M5-6, push-in right-angle fitting

Figure 3: QS-6 straight push-in connector for PUN-H tubing. (Image source: Festo)

Not just for new installations

Festo PUN-H tubing can be a crucial component in retrofitting and upgrading existing pneumatic systems used for manufacturing, processing, packaging, and storing food, drugs, dietary supplements, and other products. These upgrades may be necessary to meet the requirements of the Food and Drug Administration's (FDA) Food Safety Modernization Act (FSMA) and the FDA's current Good Manufacturing Practice (cGMP) regulations.

FSMA is a broad set of regulations without a single compliance deadline. The regulations have staggered deadlines, some of which have passed, while others don’t come into effect until 2028. The cGMP guidelines, on the other hand, are continually updated to adapt to new technologies, scientific advancements, and evolving public health concerns, as a form of continuous improvement. In both cases, PUN-H tubing can be a cost-effective part of compliant solutions.

Two tubes can be better than one

Two tubes are used in applications such as double-acting pneumatic cylinders and grippers in robotic and automation processes that require both forward (extension) and return (retraction) motions. One of the tubes supplies compressed air, and the other exhausts the air to control movement in applications like parts handling, sorting, and packaging.

When a pair of tubes is needed, designers can turn to Festo’s PUN-H-DUO tubing. DUO tubing features the same high flexibility, hydrolysis resistance, and food-grade properties as regular PUN-H tubing, making it suited for use in food processing, biotechnology, pharmaceutical, cosmetic, and other industries. Using connected pairs of tubes simplifies routing and eliminates the need for tie wraps or cable wraps. The tubes are easily split, simplifying the addition of connectors.

PUN-H-DUO tubing is available with outer diameters of 4, 6, 8, and 10 mm, corresponding to inner diameters of 2.6, 4.0, 5.7, and 7.0 mm, respectively. For example, model PUN-H-10X1,5-DUO has two tubes with 10 mm ODs and is delivered as a 50-meter roll (Figure 4).

Figure 4: This PUN-H-DUO has two tubes with 10 mm ODs and is delivered as a 50-meter roll (Image source: Festo)

When food contact is a consideration

Festo PUN-H tubing is suitable for use in food processing operations, but it should not be used if food contact is expected. When contact is anticipated, machine designers can turn to PUN-H-F tubing, such as part number PUN-H-F-10X1,5-BL, paired with a food-grade push-in connector, like model NPQR-DK-M7-Q4.

PUN-H-F tubing offers the same microbe and hydrolysis resistance as regular PUN-H tubing, and is also kink-resistant. It is made with FDA-listed materials certified to FDA 21 CFR 177.2600 and is fully food-safe, meeting both FDA regulations and EU regulations (EC) 1935/2004. The NPQR series fittings are made with stainless steel, conform to (EC) 1935/2004, and are certified according to NSF 169 (Figure 5).

Figure 5: Examples of PUN-H-F tubing with NPQR connectors. (Image source: Festo)

Like standard PUN-H tubing, PUN-H-F is easy to insert and remove using the NPQR fittings, thereby speeding up installation and maintenance. The captive, chambered O-ring in the fittings prevents leakages.

Conclusion

Kink-resistant PUN-H tubing is easy to install and is offered in a range of sizes and colors. Its resistance to hydrolysis and microbes makes it well-suited for automation and robotics in food processing and other industries. For applications that require two tubes, Festo offers the PUN-H-DUO, which simplifies machine design and installation. Designers can turn to PUN-H-F tubing when food contact is expected.

Recommended reading:

1. What Are Some New IP69K Sensor Options for Food, Beverage, and Pharmaceutical Processing Lines?
2. How to Measure the Flow of Water to Improve Treatment Effectiveness and Efficiency
3. Savoring Success: Efficient Motion for OEMs in Food and Beverage
4. How to Use Sensor Fusion to Improve Industry 4.0 Production Processes and Logistics
5. Using Temperature Controllers and Micro PLCs to Speed Small-Scale Automation Projects