Food Safe Lubricants - what you need to know.
Three simple steps to compliant, efficient and cost effective food machinery lubrication.
Step 1 protect your company
Ensure you only use products which carry an INS or NSF registration number. Every individual product must be registered in it's own right. Many unscrupulous companies make claims of registration which are at best misleading, at worst entirely false. Insist on your supplier providing a registration document for each product they claim is food safe and ensure the document matches the product details on the label - Name, Product Code, Grade etc. Don't put your business at risk of failing an external audit. The situation regarding false claims is even more critical when 3H registration is required, as these products are cleared for direct food contact it is crucial that they are fully compliant.
If you have any doubt over claims made by a lubricant supplier take 2 minutes and check the company listings on the INS and/or NSF websites on the links below. If the product AND company are not BOTH listed on at least one of these sites, they do not have the registration they are claiming.
Step 2 protect your machinery
All Food Grade Lubricants are not created equal. Synthetic or mineral base oils, additive packages, grease thickeners, solid lubricant additives, etc. all greatly influence how a lubricant performs and it's service life. Technically lard is a food safe grease and would achieve a food safe registration, however no engineer would consider lard as a bearing grease. Discuss the options with a lubricant specialist - a company that only offers one or two food safe greases cannot hope to offer the correct product for all operating conditions i.e. Extreme temperatures (high and low), harsh chemicals, water, high load, high speed, full direct food contact etc.
Molecular size is key to one of the synthetic lubricants' operational virtues - its traction coefficient or internal fluid friction (resistance). Traction coefficient is the shearing or tangential force required to move a load, divided by the load. The coefficient number expresses the ease with which the lubricant film is sheared. Compared to mineral oil molecules, synthetic lubricants, for example, have up to a 30 percent advantage over mineral oils for traction coefficient. This means the force needed to move a load is less, which means less horsepower to do the work. In a gear reducer, the lubricant in the tooth mesh is sheared, and the lower the traction coefficient, the lower the energy dissipated due to lubricant shearing. The difference is realized by low amperage draw on the motor and reduced lubricant /gear temperature. Changing to a low-traction synthetic will reduce power consumption in a spur/helical gear by 0.5 percent for each reduction, and up to 8 percent for high-reduction worm gears.
The issue of gear wear is also a consideration. A study cited in Machinery Lubrication magazine implied synthetic lubricants make gears more efficient than mineral oils. A polyglycol showed the highest efficiency (18 percent more than the highest-performing mineral oil). Synthetic hydrocarbon (SHC) gear oil also increased the efficiency of the best gears by eight to nine percent. The performance of synthetic lubricants in food-grade applications in accordance with the H1 incidental food contact registration scheme, is also a benefit. Food-grade synthetics are sometimes believed to be inferior in performance to industrial grade mineral oil lubes, a belief the study dispels.
Step 3 protect your budget
The lower cost of parafinic mineral and vegetable ester oil based food lubricants may seem attractive, however fully formulated synthetics offer superior protection extending machinery life by considerable margins and require change out or replacement much less often. Consider the hidden costs of "cheap" food safe lubricants before they end up costing more than you thought possible.
A popular topic concerning the difference between vegetable/ester oils and synthetic lubricants is service life. Synthetic lubricants as a class don't show their age, particularly at high temperatures, and have a longer service life. Often, the change interval is several times longer for synthetics at identical operating temperatures; however, the exact number depends on operating conditions, the additives and the specific synthetic used. Synthetic lubricants have a lower friction coefficient in a gearbox, better film strength and a better relationship between viscosity and temperature (viscosity index, VI). This indicates synthetic lubricants can be used at lower viscosity grades and lower temperatures. When this is the case, the gap between the service lives of minerals and synthetics significantly increases. Related to the oil change interval is the issue of product loss through evaporation and disposal. Both sludge and residue form more readily with mineral oil products. Evaporative losses are lower for synthetics due to the lack of lighter hydrocarbon structures. Purchase price tends to be a little higher for synthetic food grade lubricants than for parafinic or vegetable oil based lubes, but it is nowhere near enough to compensate for change-out intervals that are three to five times more frequent.