Regulations & Approvals

Pltz explained, The food industry has become a global enterprise, and groups that operate worldwide have issued guidelines regarding the use of lubricants that may come into contact with food. For example, the German Food and Feed Act regulates lubricant use in the food industry and related areas, such as packaging and machine manufacturing, through the Food Hygiene Directive. This directive represents a local implementation of European Union Directive 93/43/EWG that promotes the protection of food in the EU.

The EU directive is implemented by the food companies who determine the points in the process that are critical for food safety, said Pltz, and they ensure that appropriate safety measures are defined, implemented, observed and checked. To this end, the Hazard Analysis and Critical Control Points (HACCP) system must be applied.

In the United States, the Food and Drug Administration and Department of Agriculture regulated the use of chemical products in the food industry until 1998 when they ceased issuing certifications. In early 2000, NSF International, located in Ann Arbor, Michigan, United States, was established to take over the certification of products to the H1 standard based on the former FDA regulations, Pltz continued. H1 lubricants are used in food-processing environments where there is the possibility of incidental food contact.

Then, in March 2006, DIN EN ISO 21469 was issued, which is an international guideline for hygiene requirements, authorizations and registration criteria for lubricants with incidental food contact. This standard stipulates the definitions and hygiene-related requirements for the formulation, manufacture, use and handling of lubricants that may have incidental contact with products during their manufacture, treating and processing.

The standard includes the field of application, references to other standards, list of dangers, hygiene requirements and proof of accordance, Pltz said. Two appendixes list substances and the criteria for certification institutions.

Food-Safe Lubricants

Food processing and packaging production rely on a wide variety of machines and machine elements comparable to those in other industries, including compressors, gears, bearings and hydraulic components, said Pltz. Thus, the primary requirements for food grade lubricants are the same as those for conventional lubricants; namely, friction and wear reduction, corrosion protection, heat dissipation and sealing.

Depending on the application, additional requirements for food grade lubricants can also include resistance to foodstuffs and chemicals, water resistance, neutral reaction to plastics and rubber, steam resistance and the ability to dissolve sugar, he added. Color and appearance also play important roles for food lubricants.

Pltz said, In considering the requirements of the DIN standard, our research shows that synthetic based H1 lubricants often perform better than mineral oil based lubricants. He acknowledged, however, that this was not always the case.

In the past, for example, H1 hydraulic fluids often developed heavy residues in as little as 2,000 hours. Todays H1-registered hydraulic fluids, in contrast, have lifetimes of up to 20,000 working hours. In addition, he noted, hydraulic fluids based on polyalphaolefins not only provide long lifetimes, they also have excellent viscosity indexes, flash points, pour points, corrosion protection and FZG performance.

Bremer & Leguil found similar results for H1-rated PAO and polyalkalene glycol gear lubricants compared to non-H1 PAG gear oils. Also, H1-rated aluminum complex greases exceeded the performance of standard lithium soap, mineral oil greases, said Pltz. Therefore, it is possible to change conventional lubricants to high-quality synthetic H1 lubricants without affecting machine reliability.

However, Pltz admitted that this claim is the subject of intense discussion, especially between users or original equipment manufacturers and lubricant suppliers. Depending on geographic location, the prevailing opinion is that lubricants for the food industry do not match the performance of standard lubricants, he said. The belief is that H1 lubricants provide less wear protection and have shorter life.

Pltz disputed this point by saying, H1-registered synthetic lubricants now achieve performance profiles at least as high as those of conventional synthetic lubricants, if not higher. He noted that food grade synthetic lubricants have advantages over mineral oil lubricants in the areas of oxidation stability, antiwear characteristics, corrosion protection, low- and high-temperature performance and overall life.

In general, synthetic lubricants perform better, Pltz said, so a user usually gets cleaner and safer products, better machine performance, and extended lubricant and machine life, as well as a rationalized lubricant portfolio. He concluded by saying, The higher cost of using synthetic lubricants is often offset by longer lubricant life and lower overall maintenance costs.

Critical Lubrication Points

Typical risk points for lubricants in the food and related industries are gearboxes, hydraulic systems, bearings and chain drives. One of the first recognized points of contamination was the gearboxes for mixers located above the food being processed, Pltz said. Here, leaking oil may drop into and contaminate foodstuffs. Also, gearboxes on conveyors for both food and packaging may be positioned above or near the product, and oil can leak onto it.

Hydraulic systems also pose potential risks. The fluid reservoir and hoses can contaminate the product if they leak, Pltz said. And a burst hydraulic hose can spray fluid over a wide area.

While H1-registered hydraulic fluids can provide excellent wear and corrosion protection and long life, Pltz said that a great deal of care is required when replacing mineral oil based fluids with synthetic H1 fluids. To ensure that the old oil is completely removed, flush the system with the replacement oil, drain and refill, he directed. Also, filters must be changed.

Pltz continued, A multitude of bearings are used to move products in food and packaging equipment. Primary areas of risk are the points where bearings are greased. In moving to a synthetic H1 grease, he cautioned that mineral oil and PAO greases are not compatible. The challenge is to change the grease without mixing the two. Where mixing is unavoidable, the regreasing schedule should be shortened for a time to ensure that the old grease is completely flushed out.

Open chains lubricated with oil spray or central lubrication systems can be a risk point as well, he said. Fermentation cabinets, for example, operate in areas of high dust and humidity, and thin oil is needed to lubricate the chains to ensure adequate penetration into the links. These oils can drip onto the product.

Plastic injection molding machines are normally used to fabricate containers or other components of food packaging. Pltz said, In Europe, hydraulic fluids and gear oils in these machines must conform to DIN 51524-2 HLP for ISO viscosities 10 to 68 and CLP for ISO 100 to 460. Greases must meet the requirements of DIN 51825 K2K or KP2K.

Typical requirements for lubricants used in plastic injection molding are high-temperature and aging stability, high adhesion, low contaminant absorption, reduced friction and wear, low maintenance costs and compatibility with a wide range of plastic materials. They also must resist breakdown caused by residue from injected material and outgassing, all while providing long service life, Pltz said.

Conventional lubricants often are overstressed because the base oil thins too much at the temperatures involved. As a result, oil consistency changes. Also, conventional grease can liquefy and run out of the bearing or pivot point, Pltz explained. This results in insufficient lubrication, increased wear, increased oil evaporation and drying out of the grease.

Oil evaporation can cause residues to form on injection-molded parts, recognized as black and brown spots, and the parts must be rejected. This problem can be avoided with synthetic lubricants that are compatible with even sensitive plastics, said Pltz. In addition, lubrication intervals can be increased significantly with these lubricants.

Because the operating conditions in injection molding machines often exceed the performance limits of mineral oil lubricants, more machine builders are specifying synthetic oils such as PAO and polyalkalene glycol and high-temperature greases using polytherafluoroethylene thickeners, Pltz noted. These lubricants can be used at temperatures as high as 250 degrees C.

Also, mineral oil based gear oils exposed to high temperature plastic and high loads deteriorate quickly. PAO or polyglycol based oils can not only increase lubricant life and performance but also meet food safety requirements, Pltz said.

Hydraulic fluids are stressed by high temperatures, high pressures and plastic residue. Bremer & Leguil testing showed that fluid life can be increased significantly by using synthetic H1 lubricants that meet DIN 51524-2 HLP and CLP.

Temperatures in ejectors also can be very high, and lubricating greases must be adhesive, stable and resist melting to avoid contaminating the plastic. Many options are available for greases in this area, Pltz said.

For tool temperatures up to about 80 degrees C, synthetic grease based on PAO with a special thickener can be used. This grease does not leave resinous deposits and forms a stable, adhesive lubricant film on the movable parts that prevents wear and noise, he explained.

For higher temperatures, ejectors and actuators require a DIN 51825 KFKU-30 grease that can withstand temperatures of 80 to 260 degrees C. This type of grease will not contaminate injection molded parts and exhibits good compatibility with sensitive materials, said Pltz.

Finally, slideways need highly adhesive grease that stays in place under extreme pressure. An NSF registered grease is available that meets food safety standards and resists temperatures as high 160 degrees C, he said. The grease can also be used on guide bolts, column guides and geared tools with open teeth.