Addressing the Bioburden of your Metalworking Fluids
It’s an unavoidable fact: metalworking fluids (MWFs) are highly susceptible to bacterial growth. In fact, research shows that “sumps operating under typical conditions for machining … provide optimum conditions for the proliferation of bacteria.“
These fungal and bacterial colonies excrete caustic, acidic, and toxic substances that can harm workers, machines, workpieces, and your production process.
Fungus and bacteria can also directly alter the chemistry of your fluid package, eating emulsifiers and anti-corrosion additives. These degraded fluids then fail to perform, causing excess equipment wear, damaging part quality, and driving up maintenance costs.
In addition to it being “not possible to prevent microbial contamination of metalworking fluids in use”—you may struggle to even measure how big your MWF bioburden is:
Most bacterial and fungal growth is in colonies that cling to the walls of pipes and tanks, or hide in the swarf that collects at the bottom of tanks. If you draw a circulating sample, you’re likely to see less than 1 percent of what’s really happening. A test might indicate your MWF has “10^6 CFUs/ml” or “10^6 bacteria”—i.e., “a million microorganisms per milliliter of working fluid.” (“CFU” stands “colony forming units,” and is the same as individual microorganisms.) But that likely translates to something more like one-hundred million bacteria/ml system-wide, primarily hiding in plumbing and pumps.
Minimizing MWF Bioburden
Like many situations in life, the best cure is prevention. Here are four steps you can take to reduce the bioburden supported by your metalworking fluids:
- Reduce the “dirt load” in your system: Keep machines clean; chips, swarf, and sludge are where bacteria hide and thrive
- Take sump hygiene seriously: Operators do silly things, like spitting chaw or tossing sandwich crusts in the sumps; this massively increases the likelihood of bacterial growth
- Reduce tramp oil contamination: Tramp oil is good food for some bacteria, letting them thrive at the oil-water interface; starve them by cutting off the food supply
- Use good water: Water—even clean city drinking water—can be a major source of contaminants in an industrial setting, including the bacteria and fungus themselves, as well as the mineral on which they thrive
Preventing fungus and bacteria from gaining a foothold is the key. It can be quite a job to eliminate an established colony. Research shows that, if you simply dump and recharge a tank where bacteria has thrived—without thoroughly cleaning the pumps, plumbing, and filters first—bacteria levels will return to pre-intervention levels in just four days.
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