An exceptional level of hygiene is necessary in the food and beverage industry, with stringent hygienic standards, such as ISO and FSSC 22000, to ensure that there is no compromise in the quality of consumables being produced. Certain things need to be taken into account that aren’t issues in many other industries, including wash-down capabilities and extremes of temperature.
Pneumatic cylinders provide a compact and reliable method of generating both linear and rotary motion, and can even combine both with great precision to achieve 3D motion. This allows extremely accurate positioning at all points in the production cycle, from ingredients to finished products and packaging.
Pneumatic systems are most commonly used in processes that require precision and speed. These include highly repetitive tasks, and more delicate operations such as the handling of eggs or bananas, and placing pastries in a precise position for icing. Compressed air systems are also commonly used in conveying food and beverages along a production line, as they're easier to keep clean than electrically driven or hydraulic systems.
How Is Compressed Air Used In The Food & Beverage Industry?
There are many food and beverage industry uses for compressed air, due to the greater flexibility it supports in its operating environments. Environmental factors that govern the choice of pneumatics include excess levels of vibration, extremes of ambient temperature, and the presence of chemicals or other fluids. Very high or low temperatures are not unusual, requiring pneumatic cylinders to perform in operating temperatures from -40°C up to 150°C.
Food and beverage industry uses for compressed air include sorting, cutting and shaping foodstuffs like cheese, and separating ingredients, such as the liquid whey that is removed from milk solids that will later form the cheese. Pneumatic cylinders are very effective in providing high-precision control over the applied pressures necessary for such delicate operations.
Chopping, Cutting, Slicing & Dicing
Most of these operations are carried out by compressed air-driven tools, including saws, knives and mandolin blades. These can be mounted on a rotary table or travelling carriage. Chopping foodstuffs into a coarse pulp requires a rotating bowl and high-speed rotary blades, which can be programmed for the time and degree of chopping.
Bacon slicing, cheese grating and fruit fanning can be undertaken with compressed air tools, as well as dicing vegetables for freezing, or canning and chopping meat for processing. Precision adjustments can be made for size, thickness, angle and direction of cutting. More sophisticated designs allow for variations in the uniformity of product to offer a more natural result.
Compressed air is used to push materials through static or flexible pipework to move them from the point of supply to the point of use, or to transfer materials from delivery point to in-plant storage. A compressed air pump will create a vacuum at the receiving end of the transport, drawing liquids, grains or powders through the pipework. A series of valves open and close ports where the ingredients are to be dispensed, and can be very precisely programmed for the timing and amount of material to be dispensed. Items can be placed on a conveyor or rotary table, passing beneath a dispenser.
Pneumatic mixers use compressed air or air bubbles to mix materials, and consist of a mixing silo and usually a conveying tube, which dispenses and spreads the materials. They have nozzles at the side or bottom of the mixing silo which intermittently pump in high-velocity compressed air or gas. Increasing the air velocity agitates the powder bed, causing bubbles to form and initiate blending. Powders at the bottom expand when they're aerated, and cause other particles to reorient themselves and rise up.
Other food and beverage industry uses for compressed air include blow-moulding hollow objects. This is a similar process to glass blowing, where compressed air is forced into a hollow tube, and a molten material is extruded from it to form a particular shape, dictated by a mould. Most hollow polyethylene (PET) products are produced in this way, including milk, water and soft drink bottles, and bottles for cooking oil, salad dressings and honey.
Pneumatic presses can be used for mincing and pulping operations, where the press contains a central pneumatic inflatable membrane or is pushed down by a pneumatic actuator. They're also used for the forming and shaping of many items such as bread and pastries, confectionery and cheese. Many of these processes are now governed by automated controls and sensory equipment. This can assess the condition of the food to be processed and adjust the degree of processing accordingly.
Vacuum pressure is very well adapted for the efficient lifting, placement and manipulation of food products, especially if they're delicate or asymmetric. Items can be placed on conveyors or rotary tables, and picked up by vacuum cups or pneumatic grippers to place into cartons or packs. Compressed air systems are also used in food packaging, for tasks like forming bubble packs, and the cleaning, filling and sealing of all types of package.
What To Consider When Using Compressed Air?
Various matters must always be considered when using compressed air, to ensure absolute hygiene, compliance with standards, and the smooth running of the application.
Solid particulates, including spores, dirt and rust from metal components can adhere to parts and clog up nozzles. Downstream pneumatic tools and equipment will be damaged if subjected to contaminated compressed air, causing potential downtime, expensive repairs and loss of productivity.
It is imperative to eliminate moisture for compressed air applications in the food and beverage industry, as it provides an ideal breeding ground for fungi and micro-organisms. Water may collect in areas of the piping system where the compressed air actually comes into direct contact with foodstuffs. Micro-organisms or fungi could then be transferred into food containers or products.
It's also crucial to take into consideration the ingredients to which the application's component parts may be exposed. Ingredients like sugar crystals, ice or dough mixtures can interfere with the proper operation of the cylinder, by forming deposits on the piston rods. These residues can be removed by installing metal (rather than plastic or rubber) scraper rings with the piston rod seal, which will prevent any deposits from building up.
In order to eliminate contamination, the compressed air must be properly prepared before it reaches any active part of the system. This entails installing an FRL unit and ensuring it's regularly maintained. Whenever possible, lubrication-free or pre-lubricated assemblies should be installed, which use food-grade grease and don’t demand any additional lubrication.
Automatic stainless steel or tapped manual drains are often used as filter options. These remove any excess liquid that might otherwise collect and drain straight onto the floor. Non-relieving regulators are also advisable for the food and beverage industry, as they don't allow any liquid or gases to escape into the atmosphere.
Reductions in the type of materials used in, for example, PET bottles, mean that the amount of energy required to produce them can also be reduced. The amount of PET previously needed for a 450g bottle was upwards of 14g. Reducing the amount per bottle demand of PET to under 10g has decreased the demand on compressed air pressure, leading to great energy savings.
Over the last 20 years, advances have also been made in the development of compressed air recovery systems. In this way, energy savings can be increased by recovering and reusing high-pressure compressed air from the exhaust for other processes. This compressed air can be recirculated for use as pre-blow air in a moulding application, for example, or as service air for the blowing apparatus. In some traditional types of machinery, this process can recover up to 60% of the exhausted compressed air for reuse in lower pressure circuits.
Food Safe Pneumatic Components
Clean design is essential when manufacturing food-grade pneumatics, as strict hygienic standards cannot be compromised. Pneumatic products for use in the food and beverage industry are commonly made of high-performance stainless steel, which can withstand the corrosive materials that are often used in wash-downs. Some components, including valves, may be designed for mounting within a protective enclosure, but cavities or crevices may exist in the enclosure where bacteria can linger, and must be cleaned even more carefully.
Stainless steel is expensive, so cheaper alternatives are being developed for food and beverage applications that combine it with anodised aluminium parts. Moving parts such as pistons and bearings can now be constructed from low-friction thermoplastics, which have high rigidity and excellent dimensional stability.
Critical Issues And Compressed Air
Cleanliness, hygiene and sanitation are critical in the food and beverage industry. Failure to comply with the requisite standards can lead not only to prosecution and fines, but to illness, a consequent loss of customer confidence, and even the potential of bankruptcy. Food and beverage industry uses for compressed air are many, but the principle behind all applications is that they must be scrupulously clean and sterile.