PAG technology a new staple for food-grade lubricants
Since the original introduction of H-1/food grade lubricants into the food, beverage and pharmaceutical processing industries in the early 1960s, there have been significant advances in H-1 lubricant research and development which have produced top performing H-1 products. Polyalkylene Glycol (PAG) fluid technology is a shining example of these performance advances.
The original introduction of food grade lubricants into the food and beverage industry in the 1960s had two purposes: to provide protection for machinery, and to maintain food safety. In the beginning, food and beverage manufacturers were generally limited to using USP white oils having no additives. Functional lubricants were non-food grade conventional industrial lubricants.
Continuous improvements since the 1960s have led to today’s food grade lubricants which provide superior performance in hydraulic systems, gear and chains, compressors and many other standard applications.
Although the lubricant industry has achieved many successes, the search for even better performance by lubricant manufacturers continues. To food safety, there has now been added consideration of the impact of food grade lubricants on the environment. Most food plant managers have switched from non-food grade lubricants to advanced lubricants; however, there are still some who believe the performance or the cost of the advanced lubricants does not give them an edge over conventional industrial lubricants. But inevitably there are still occasions when a lubricant leak from machinery comes into contact with food being processed, resulting in fines or product recall.
A researcher seeking to develop a food grade lubricant to serve a specific purpose can select from base stocks and additives that have been approved by the Food and Drug Administration, as well as from a long list of substances in the Generally Recognized As Safe category. These are substances that have not been approved by the FDA, but that have been in long use as ingredients in foods and beverages.
Food grade lubricants are approved and registered by the National Sanitary Foundation, a non-for-profit organization. Before 1999, approval and registration had been in the hands of the USDA. The NSF registers lubricants according to the FDA-approved ingredients listed in 21 CFR 178.3570, “Lubricants with Incidental Food Contact or category H-1."
NSF toxicologists determine product acceptability based on FDA’s list of approved ingredients/raw materials against CFR 9, 21. NSF approval of a lubricant tells firms using the lubricants, as well as FDA inspectors, that the lubricants used conform with food safety requirements. The NSF’s online “White Book” lists all currently approved lubricants.
The NSF places each non-food compound that it approves into one of these three categories:
H-1: Compounds and lubricants that are approved for use on a machine whose lubricated parts may potentially come in contact with food. Collectively known as “incidental food contact lubricants,” these are the lubricants that are approved for food and beverage manufacturing.
H-2: Compounds and lubricants that may be used on equipment that is sufficiently removed from food processing operations that there is no possibility of the lubricant or lubricated parts coming in contact with food. A remote compressor that provides air to food processing equipment is an example of the equipment that uses compounds and lubricants from this category.
H-3: Water-soluble lubricants often applied to equipment manufacturers to new equipment to avoid rust and corrosion during transport. These lubricants intended only for temporary application during transport, and are not acceptable for use in food processing plants and must be removed before the equipment enters production.
Within the Category H-1 food grade lubricants which comply with the FDA CFR 21, 178.3570 there are four types of approved lubricants. Plant managers can select from the following types of food grade lubricants:
- White Mineral Oils
- Natural Oils
- Polyalphaolefins (PAO)
- Polyalkylene Glycols (PAG)
The first two types are made using natural or non-synthetic base stocks. The latter two types are made from synthetic base stocks. Much of the progress in matching a food grade lubricant to the needs of an application have come from synthetic fluids, and of these the most significant are the PAGs.
PAGs are made from the reaction of alkylene oxide monomers to form polymers, which are composed of ethylene oxide and propylene oxide. Lubricants based on PAGs have been received favorably by food manufacturers because their performance exceeds the performance of lubricants whose base stock is a mineral oil.
A key reason for the superiority of PAGs is their ability to provide sufficient lubrication even in the presence of water. PAGs can be fine-tuned to achieve optimum performance. If the PAG polymers contains a higher percentage of ethylene oxide, then the base stock will have higher solubility in water; if the polymers contain a higher percentage of propylene oxide, the base stock will have lower solubility in water. Blending different PAG base stocks permits the production of lubricants that meet specific targets for viscosity and other properties.
PAGs are also less harmful to equipment that has accidentally over-heated. Lubricants in the other three groups – white oils, natural oils, and PAOs – tend to leave a residue of carbon, gum or varnish. PAGs experiencing the same conditions leave practically no residue.
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.
PAG’s can be used to formulate food grade lubricants for applications such as compressors, hydraulic systems, gears and 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 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. 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.
Because PAG’s 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. Limited scale testing of energy consumption showed that these lubricants may enable a machine to use up to 8% less energy than an identical machine using petroleum-based industrial gear oils or food grade white oil based gear oils.
Lower energy requirements and superior thermal stability mean that these products will have longer life. In addition these lubricants biodegrade rapidly and have lower impact on the environment.
|Lubriplate PGO 100||Lubriplate PGO 150||Lubriplate PGO 220|
|Viscosity at 40°C||102.4||156.0||221|
|Four-Ball Wear Test||0.52||0.54||0.53|
|Weld Load Kg||160||160||160|
|Load Wear Index||32.9||33.4||33.4|
|FZG Wear Test, Pass Stage||12||12||12|
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 about 15°F cooler on the new gear oil. At the same time, power consumption measured was about 7% less. Physical properties of the gear oil are shown in Chart 2.
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.
Sibtain Hamid is General Manager for the Toledo, OH operations and corporate technical director for LUBRIPLATE Lubricants Company. He can be contacted at (419) 697-4156 or by e-mail at shamid(at)lubriplate.com