Control Rancidity –
and Boost Your Bottom Line
Rancidity – the chemical decomposition of fats, oils and other lipids – happens when bacteria, yeasts and mold are allowed
to multiply in metalworking fluids. The result is a foul odor, diminished tool life, oxidation on the workpiece surface – and very
unhappy workers. Certain types of rancidity can also cause metalworking fluids to darken and stain parts, and neutralize the
rust-inhibiting characteristics of the fluid. Left unchecked, endotoxins, an illness-causing compound found inside bacteria and
other pathogens, can make things even worse.
The two major opportunities for rancidity to start are when the product is diluted for use (quality metalworking fluids manufactured
in the US arrive free of microbial contamination) and on weekends, when metalworking systems are typically shut down. The latter
becomes a problem because aerobic bacteria consume the available dissolved oxygen, setting up a chain of events that leads to
the distinctive smell of "rotten eggs."
It's not practical to eliminate all microorganisms from metalworking fluids, but you can keep them in check, prevent rancidity,
and achieve metalworking's holiest grail: maximum service life. Here are our 8 most important recommendations on how
to do that:
- Buy quality metalworking fluids from a reliable source. Don't risk your tooling, your time and your
production on No-name, Email Specials-of-the-Day.
- Get help. A credible suppler will test quality metalworking fluids in your systems so you can evaluate
performance, fluid stability, service life and cost. They can also help with water-related issues:
common water components such as calcium, magnesium and phosphates all contribute to rancidity;
water hardness also has an impact. Fortunately, all of this is manageable.
- Clean your machines, reservoirs, lines, etc. before each charge using a good machine cleaner.
This will eliminate the sludge, fines and oil that attract microorganisms.
- Never use reservoirs for general disposal. Food wrappers and other waste have no place here.
- Monitor concentration and pH. While too high a concentration is just wasteful, too much dilution
deprives your systems of the full benefit of the fluid's inherent rancidity control. To maintain optimum
concentration, consider a premix station or proportioning device to mix water and fluid at the right
concentration. The pH of a diluted metalworking fluid should fall between 8.8 and 9.2 to maintain
rust protection properties and control rancidity.
- Aerate at least intermittently, to keep all areas of the system in motion, and less susceptible to microbial attack.
- Keep tools in good condition to avoid leaking lubricating fluids into water-based coolants.
- If all else fails and rancidity strikes: get to know an Acculube metalworking fluids expert.
They have the most, and broadest experience with every major type of metalworking fluid and machining
system. They're eager to share ideas on how you can get out of trouble quickly – and make adjustments in
product, additives, or process that will serve your shop – and your wallet – in the long term.
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