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Why use food grade lubricants?

Wed, 05/21/2008 - 8:23am
Sibtain Hamid, BASF Corporation

Historically, food grade lubricants have not matched the performance delivered by industrial lubricants (gear oils, hydraulic oils and compressor oils). Food and beverage plant managers chose industrial grade lubricants because they were unwilling to jeopardize the longevity or output of their equipment. Of course, by using industrial grade lubricants these managers risked the potential contamination of their products by accidents, leakage, or human error.

Recently this situation has changed profoundly. The lubricant industry has developed new synthetic food grade lubricants that equal or surpass the high performance of synthetic industrial-grade lubricants. Synthetic lubricants typically have better performance than the conventional mineral-oil based lubricants, and the expected service life is two to three times longer. The performance of these new food grade lubricants has been demonstrated in hydraulic, compressor and gear lubrication systems.

The earlier generation of food grade lubricants - chiefly United States Pharmacopeia (USP) grade white oils (a highly refined petroleum base) with few additives - has been replaced by high-performance synthetic lubricants. Product development and improvement is still continuing as additional additives are qualified and approved by the United States Food and Drug Administration (FDA). To a significant degree, progress in gaining FDA approval for new lubricants for food and beverage equipment has depended on the innovative use of a wide variety of additives.

Why use food grade lubricants?


Product contamination from equipment using lubricants is a significant concern. A plant still using non-food industrial grade lubricants risks an expensive product recall that could damage the brand name or the company reputation. The cause of contamination can be subtle. For example, a minor leak resulting from normal wear and tear could mean that product has been packaged and shipped before the contamination is noticed. Food grade lubricants protect the manufacturer in a case such as this because the FDA allows contamination with food grade lubricants up to 10 parts per million. Many food plants, slaughterhouses, bakeries and food packagers are required to undergo regular inspections by the United States Department of Agriculture (USDA) to ensure the quality of food being prepared.

To reduce the risk of contamination or fines, many companies are switching to food grade lubricants that are registered with the independent not-for-profit National Sanitary Foundation (NSF). The NSF registers lubricants based on FDA pre-approved ingredients under 21 CFR Section 178.3570, and assigns each lubricant to one of these three categories:

  • H-1: "Incidental contact lubricants" that are permitted on equipment where the food or beverage may potentially be exposed to the lubricated parts of machine. These are the recommended lubricants for food and beverage plants.
  • H-2: Compounds and lubricants that may be used on equipment locations where there is no possibility of the lubricant or machinery parts lubricated with such lubricant coming in contact with the food or beverage being processed. Most industrial grade lubricants are in this category.
  • H-3: Water soluble lubricants used on machine parts that are required to be cleaned prior to food contact. These lubricants should not be used in food processing plants as lubricants.



Selecting a food grade lubricant


In the past, few original equipment manufacturers (OEMs) approved H-1 category lubricants for their equipment, generally because of the shortcomings of the earlier generation of white oil based lubricants. The development of synthetic food grade lubricants has helped to alleviate this problem.

BASF Corporation and other companies have successfully developed synthetic food grade lubricants suitable for major applications including compressors, hydraulics, gears, bearings and chains. H-1 food grade lubricants can now perform the same technical functions as many industrial grade lubricants, including:

  • Protection against wear and friction.
  • Protection against corrosion and oxidation
  • Heat dissipation
  • Compatibility with elastomers and seals
  • Protection against degradation from plant food ingredients, plant process chemicals and water
  • Inhibition of the growth of microorganisms such as bacteria and fungi



Food grade lubricants types & make-up


Food grade lubricants are composed of a basefluid (the main body of the lubricant) and additives. The basefluid provides the basic properties such as lubricity, viscosity, pour point and flash point. Additives enhance some of the basefluid’s properties and may add additional properties to the finished lubricant. For example, an additive may enhance the anti-wear protection of the basefluid, and may additionally protect metal surfaces from corrosion.

Three basefluids have been approved by the FDA for use in H-1 lubricants:

  • White mineral oil (White Oils)
  • Polyalphaolefins (PAOs)
  • Polyalkylene glycols (PAGs)



PAGs are gaining greater acceptance as food grade lubricants because of their overall superior performance in food and beverage plant environments. This superiority may be attributed to their ability to tolerate large amounts of water and still function as adequate lubricants. They also exhibit low coefficients of friction and better thermal conductivity, resulting in longer life lubricants.

PAGs tolerate water well because they contain both ethylene oxide and propylene oxide, making it possible to fine-tune the water solubility of the lubricant. Lubricants can therefore be customized to meet specific needs by blending different PAG stocks. PAGs also have an advantage in case of accidental overheating of the lubricated machine part. Mineral oils and PAOs leave a hard black carbon residue when they are overheated, but PAGs leave no residue and the part remains clean because overheated PAGs tend to decompose into carbon dioxide and water. Parts lubricated with PAG therefore exhibit no carbon buildup or gumming even after prolonged use.

Food grade fire-resistant hydraulic fluid


The development of a food grade fire-resistant hydraulic fluid is a good example of the new generation of synthetic food grade lubricants - a fully formulated product that satisfies all of the requirements typically associated with an industrial grade, non-food grade fire-resistant hydraulic fluid. The industrial grade fire-resistant hydraulic fluids are water glycol based and meet FM Global standards for fire resistance. These industrial grade fluids protect metal parts from corrosion and rust, and provide boundary lubrication to the bearing and vanes. They also provide vapor phase corrosion protection to the sump parts and to other parts of the hydraulic system. The risk is that water will be vaporized out of the fluid and that the water will then corrode metal surfaces; vapor phase corrosion additives prevent this because they are vaporized along with the water and thus are in place to protect the metal surfaces.

By contrast, food grade glycol-based fire-resistant hydraulic fluids have typically provided boundary lubrication and have held FM Global Approvals. Their shortcoming, however, was that they did not provide vapor phase corrosion and rust protection to the hydraulic system. So the conversion from mineral oil based hydraulic fluids to food grade hydraulic fluids could create a severe risk of corrosion and rust, especially on sump overheads, which are generally made of carbon steel

To solve this problem, a water/glycol-based fire-resistant hydraulic fluid has been developed that - like existing fluids - provides boundary protection and has FM Global Approval, but that also provides protection against rust and vapor phase corrosion.

The newly developed water/glycol-based fluid was tested alongside existing hydraulic fluids in a vapor phase corrosion (VPC) test. In this test, three freshly polished carbon steel coupons are suspended with the bottom half of the coupon submerged in a 100 ml sample of the hydraulic fluid. This assembly is placed in an 18-inch long cylinder that is closed at the top with a condenser. The cylinder is then placed in an oil bath heated to 145°F. The coupon is inspected for rust and corrosion every 24 hours for up to 96 hours.

The results of the VPC test are shown in Figure 1. On coupon A, a commercially available food grade water/glycol-based fire-resistant hydraulic fluid was used. This hydraulic fluid provided no protection from vapor phase corrosion, and the coupon is visibly corroded. On coupon B, the newly developed hydraulic fluid containing a protective additive was used. Coupon B has no corrosion at all.

Addition of these additives did not change any of the existing properties of the basefluid such as boundary lubrication. Several vane pump tests (Figures 2 and 3) were carried out to verify that the lubrication performance of this food grade hydraulic fluid is at least equal to the performance of industrial grade hydraulic fluids.

New food grade gear lubricants


New food grade gear lubricants for the food and beverage industry have also been developed. These are fully formulated, extreme pressure gear lubricants, and were designed for use on worm and hypoid gears. They were developed with select ingredients identified in FDA regulation 21 CFR 178.3570 for use where incidental food contact may occur. They have been registered with the NSF international under the H-1 classification.

These food grade gear oils provide high lubricity (i.e., a lower coefficient of friction), and have a high viscosity index that permits them to be used over a wide range of operating temperatures. When overheated to decomposition temperatures, these gear oils produce no sludge, varnish, gums or tars. Because the gear box runs cooler, most gear sumps tested were found to be cleaner compared to those lubricated by mineral oil based gear oils.

In addition to excellent lubricity and a high viscosity index, these new gear lubricants have better oxidation stability and a low pour point. In-house testing of energy consumption showed that these lubricants may enable a machine to use up to 8 percent less energy than an identical machine using petroleum-based industrial gear oils or food grade white oil based gear oils.

A side-by-side field trial testing with the new gear oil and AGMA 5 petroleum based gear oil showed that the worm gear box unit ran about 15°F cooler on the new gear oil (Figure 4). At the same time, power consumption measured was about 7 percent less. Physical properties of the gear oil are shown in Figure 5.

Conclusion


High performance food grade PAG based lubricants match or exceed the performance of conventional non-food industrial lubricants. PAG based lubricants tolerate food chemical contaminations and water, and thereby increase lubricant and equipment life of food processing machinery.

For more information, contact the author, Sibtain Hamid, at (734) 324-6452 or by e-mail at sibtain.hamid@basf.com.

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