The food industry is edging away from “synthetics” in almost every way. But there’s one notable exception.
Food-grade lubricants are broadly divided into two classes: synthetic and mineral oil-based. The situation is roughly analogous to motor oil: Synthetics are more expensive but last longer and can handle a wider range of conditions.
Jim Girard, chief marketing officer for Lubriplate (www.lubriplate.com), says that his company’s food industry customers want long-life food-grade lubricants. Equipment manufacturers “are recommending synthetic fluids and greases, which is the market driver,” he says. New Lubriplate products in this line include polyol ester food grade chain oils and perfluoropolyether (PFPE) greases for extreme high temp applications.
The difference between synthetic and non-synthetic lubricants is mostly in the raw material. “Mineral oil” is a catchall term that denotes a range of products, including lubricants, based purely on crude oil. White mineral oil, used for applications with direct food contact, derives from highly refined petroleum. Synthetic products are based mostly on chemicals other than crude oil, most often esters or olefins, although some synthetic lubricants are blends that include materials derived from crude oil.
The biggest single determinant for using synthetic oil is temperature. Synthetics can be engineered to endure both higher and lower temperatures than most mineral-oil-based lubricants.
The highest feasible temperature for an application with a mineral oil lubricant is about 160°F, says David Turner, product specialist at the Clarion Lubricants division of Citgo (www.clarionlubricants.com/FoodGrade). “When you get up around 200°F, it’s time to start thinking synthetic, because the service life of a mineral oil product will be significantly shorter than it would be at a lower temperature,” Turner says.
Matching application temperature to lubricant type is not just a matter of making sure the equipment won’t break down. The lube’s service life should be considered; if it has to be changed too often, any money saved by using it will turn out to be a false economy.
The base temperature for maximum service life tends to be around 175°F for synthetic lubricants, compared with about 140°F for mineral oils, Turner says. As the application temperature rises above 140°F, mineral oils, or any lubricants based on hydrocarbons, tend to break down rapidly. For every 18°F over 140°F, the service life tends to get cut in half. That means a lubricant rated for 1,000 hours of service life at 140°F would have only about 125 hours at 194°F.
On the other hand, end users have a powerful incentive to use mineral oil lubricants: price.
“We recommend the white mineral oil for most food-grade applications simply for economic purposes,” Turner says. He cites a global survey from the National Lubricating Grease Institute that determines that 90 percent of the greases produced around the world are mineral-oil based.
“The vast majority of applications out there, be it gear oils or hydraulic fluids or a few other things, are basically very well covered by mineral oil-based products,” he says. “But there are a few places where a synthetic fluid would be needed.”
Even among synthetics, there are widespread price differences. Much of the product development in synthetic lubricants has to do with finding less expensive alternatives for a given application. For example, Food NH174-401, a new oil from Klüber (https://www.klueber.com/en/), can be used in applications like pulleys and bearings at temperatures up to 450°F. It uses a polyuvea thickening additive with a synthetic base at one-fourth the cost of PFPE grease, according to food marketing manager Marius Czech.
Making the grade
Both mineral-oil-based and synthetic products are subject to certain basic classifications when it comes to use in food plants. Perhaps the most basic is what constitutes being a “food-grade” lubricant in the first place.
Broadly speaking, being classified as food-grade means a lubricant is not toxic if consumed in trace amounts. This is for the most part a matter of starting with a nontoxic base, whether mineral oil or an ester or olefin, and avoiding toxic additives like lead, zinc or lithium.
The entire concept of “food-grade” lubricants doesn’t have long-standing roots. As recently as the late 2000s, a poll of food processors by NSF International showed three out of five did not stock any lubricants rated as suitable for applications with a possibility of food contact.