The Pure, Safe Approach to Food Grade Lubricants
Food Grade Lubricants have been a part of industrial lubrication since the early 1960s. They were first introduced and used in the United States market. Since their initial development, there have been great high technological advancements with research, development, introduction and use of food grade lubricants.
by Sibtain Hamid
The food industry is one of the largest and most diverse industries in the world and is the best example of industry globalization. Major factors influencing this trend are better equipment technology, efficient transportation, awareness of food safety and a movement towards more common packaged or processed food consumption around the world.
Food grade lubricants are the workhorses for ensuring the equipment that is processing food is properly lubricated and running smoothly. The type of machinery used in the food industry includes: processing equipment, cutting and grinding and food preparation equipment. Hydraulic fluids, gear oils and greases are common to many such applications. Demand for food grade lubricants is also increasing for gears and compressors. As a consequence of globalization, the market for food grade lubricants is emerging as a growth segment within the global lubricant market.
Demand for the use of food grade lubricants comes from equipment manufacturers, food and beverage manufacturing, food processing, food distribution centers and regulatory bodies. At the same time original equipment manufacturers (OEMS) are reducing the size of the equipment with smaller sump sizes, meaning there will be more thermal stresses on lubricant. As a result lubricant suppliers will not only have to incorporate new advanced technology additives but also look for synthetic base stocks to make this happen.
Some of the same trends are also influencing greases. Specialty greases incorporating the benefits of mixed base oil or full synthetics. The growth of these high performing synthetic lubricants or blends is directly related to the requirements for improved productivity, efficiency and environmental concern.
A broad range of food grade lubricants is used in food plants. Common applications such as gears, hydraulics, compressors and bearings use USP grade white mineral oils as a base stock. To meet the demands of higher performance applications, successful formulations require use of full or partial synthetic basestocks such as polyalphaolefins (PAOs), esters or polyalkylene glycols (PAGs) — or a combination of these fluids.
Since synthetics enhance or build certain properties into the product, formulators or compounder/blenders select base fluids based on application requirements and economic drivers. A list of Approved Incidental Contact Lubricant Base stocks includes:
- White mineral oils
- Polyisobutylene (PIB)
- Polyalphaolefins (PAO)
- Polyol Esters
- Polyalkylene Glycols (PAG)
All food grade lubricants (incidental contact) must be registered with the National Sanitary Foundation (NSF) under H-1 classification (or H-2 where incidental contact cannot occur). All ingredients used in the formula must comply with the CFR 21-178.3570; such ingredients must also be registered under one of three NSF HX categories. In order to meet the growing demands of customer or OEM driven applications, plants producing these lubricants should, preferably, also have NSF 21469 registration.
The environment of many food processing facilities contains high levels of moisture. As such, lubricants in use or equipment sumps can potentially get contaminated with water. Additionally, food plants also use a detergent and hot water to wash down the equipment and floors. Thus, lubricants and greases in use must resist water and other contamination and protect the equipment from rust and corrosion.
Operating temperature for hydraulic fluids in a food processing plant is usually mild. In such conditions, white oil-based hydraulic fluids perform very well.
Fire-resistant PAG based hydraulic fluids are found in significant quantities in meat, poultry, dairy and sea food processing. Many food processors use these fluids to reduce the risk of fire in areas of the plant where there is a constant source of ignition. Where water containing PAG are not recommended due to fluid maintenance issues, polyol esters fire resistant hydraulic fluids find application.
Gear and Bearing Lubricants
Gear lubricants are typically formulated from white mineral oil, PAOs or PAG with registered additives. Many of these gearboxes are inside large spiral freezers. Other applications include augers, meat blenders, mixing equipment and conveyors.
In food plants, chains carrying food items to baking ovens are often exposed to temperatures over 500°F. In the higher temperature applications, food grade approved thermally stable polyol esters are found. For milder temperature applications, (e.g. below 300°F) white mineral oils or PAO-based lubricants are used.
Food Grade Greases
Greases find many applications in food plants including use in bearings and conveyers. Most common greases are made with white mineral oil and aluminum complex thickening agents along with HX registered additives. For higher performance applications greases made with PAOs and aluminum complex gelling agents can be found.
The Benefits of PAG-Based Food-Grade Lubricants
Among the base fluids approved for incidental contact listed above, PAG fluids offer unique properties found beneficial in industrial application. The performance flexibility offered by PAGs means that uses have become increasingly diverse. It is not uncommon to find PAGs in compressors, hydraulics, gearboxes and tenter frame and chain lubricants. In addition PAGs are useful in applications where a narrow molecular distribution, high viscosity index and low carbon residue/sludge is critical for the application.
Performance Advantages of PAG-Based Food-Grade Lubricants
PAGs leave virtually no residue and are thus less harmful to equipment that has accidentally over-heated. When overheated to decomposition temperatures, these gear oils produce no sludge, varnish, gums or tars. Instead, PAG-based gear and chain oils, when they reach decomposition temperatures, convert to simple molecules and evaporate without leaving hard carbon deposits. Lubricants in the other three groups — white oils, natural oils, and PAOs — tend to leave a residue of carbon, gum or varnish.
In addition, PAGs have excellent lubricity, low toxicity and a high index of viscosity. They are biodegradable, have good cold flow behavior, and have good oxidative and thermal stability. Overall, PAGs represent a dramatic improvement of the base stocks that were being used in the 1970s.
PAGs can be used to formulate food-grade lubricants for applications such as compressors, hydraulic systems, gears, chains and many other applications in food plants. Lubrication manufacturers use PAGs to develop lubricants specifically targeted for gear and chain applications for the food industry.
These are fully formulated, extreme pressure gear lubricants designed for use on worm and hypoid gears. They were developed with select ingredients identified in FDA regulation 21 CFR 178.3570 for use in situations where incidental food contact may occur. They have been registered with the NSF international under the H-1 classification.
PAG-Based Gear Oils — An Example
Industrial gearboxes are expected to perform under conditions of high heat and heavy loads; and in environments often contaminated with dirt, process debris and water. Without adequate protection, gears will wear prematurely. In order to avoid failure, operators often need to replace parts and oil frequently; all while experiencing equipment downtime and maintenance labor expenses. PAG-based gear oils offer significant benefits compared to conventional white oil or PAO-based products.
Both water soluble (higher Ethylene Oxide, EO) and water insoluble base fluids (higher propylene Oxide, PO) PAGs are used in gear oil formulations. As mentioned previously, food manufacturing and processing facilities commonly have such high moisture environments. Furthermore some food manufacturing plants wash down their equipment towards the end of day/night shifts with water. In this environment, water soluble fluids offer better Extreme Pressure, EP/boundary lubrication performance, higher load carrying ability making these fluids particularly suitable for applications where high level of moisture is present. The complete water solubility feature of PAGs helps in washing process of the equipment compare to lubricants which are not water soluble. Due to these and other advantages, food grade H-1 (incidental food contact) gear oils are now being made with water soluble PAGs.
Water insoluble fluids are used where demulsifying properties are essential.
PAG-based food grade gear lubricants 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. Because PAGs inherently have lower coefficient of friction, the gear box runs cooler. Most gear sumps tested were found to be cleaner compared to those lubricated by mineral oil based gear oils.
Lower energy requirements and superior thermal stability mean that PAG-based food-grade lubricants offer longer life. In addition these lubricants biodegrade rapidly and have lower impact on the environment.
The energy saving advantage of PAG gear oils has been documented by many authors. In one study, a polyglycol oil resulted in the highest degree of efficiency — 18 percent more than the high performance mineral gear oil. These lubricants ensure low friction coefficients, which makes them suitable for gears with a high sliding percentage (worm gears). With the appropriate additives, they provide excellent antiwear protection in steel/bronze worm gears, and have a good extreme pressure performance. In gear systems, higher polarity polyglycols allow greater interaction on the metal gear surface. This gives polyglycols mild extreme pressure performance even without additives.
A side-by-side field trial testing with the PAG gear oil and AGMA 5 petroleum based gear oil showed that the worm gear box unit ran cooler with PAG based gear oil. At the same time, measured power consumption was about 7 percent lower.
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 the longevity of both the lubricant itself and the food processing machinery on which it is being used.
Hamid is corporate technical director and vice president, general manager for Lubriplate Lubricants. He may be reached at 419-691-2491 or email@example.com.
Sibtain Hamid, PAG Technology a New Staple for Food-Grade Lubricants, Plant Engineering, 1/10/2011
Sibtain Hamid, Food Processing White paper, 2011, choosing and Applying Lubricants in Food processing Plants.
Sibtain Hamid, Mike Raab, Additives for Food Grade Lubricants, (Chapter 17) Lubricant Additives & Application, Marcel Dekker, 2003.