From Clogging to Dermatitis: The Burdens of Metalworking Fluids
When we think about “biological contamination,” our minds jump to health risks (and zombie movies). But bacterial and fungal colonies taking up residence in your metalworking fluid (i.e., the MWF’s “bioburden”) is actually more likely to damage production than hurt workers.
MWF Bioburden vs. Operator Health, Safety, and Comfort
Bioburden can have a negative impact on your operators. These come in three forms:
“Monday-morning stink”: Some bacteria excrete hydrogen sulfide (the gas that gives swamps, sewers, rotten eggs, and natural gas their distinctive stink). When sumps sit stagnant (as over the weekend), hydrogen sulfide dissolves into the fluid. When the equipment starts running again on Monday morning, that fluid gets churned up, and the gas released. In large amounts, hydrogen sulfide is indeed dangerous—but there’s next to no chance of such a huge gas buildup in a metalworking setting. For most operations, it’s an annoyance rather than a hazard.
Dermatitis: Some cases of skin irritation are caused by the organic salts and metabolic acids excreted by bacteria living in your fluids. But much more often, contact dermatitis is caused by the increased fluid pH and biocides needed to battle the bacteria that’s taken up residence in your system fluids.
Respiratory Issues: There’s some debate here, as MWFs can trigger different conditions in different people for different reasons—and bioburden us just one of those. But there is definitely a demonstrated connection between some cases of hypersensitivity pneumonitis (HP) and metalworking fluids supporting significant colonies of mycobacterium immunogenum. HP is a serious, chronic form of pneumonia that can lead to permanent scarring of the lungs. Metalworking fluid—which tends to get aerosolized during work, and thus can be easily inhaled—can create a significant risk of HP, especially in sensitive individuals. According to one study “It is not possible to prevent microbial contamination of metalworking fluids in use. Disease prevention should focus on stopping inhalation of aerosols, particularly by re-engineering to remove recirculation.”
MWF Bioburden Impact on Production
- Unchecked bacterial and fungal growth in your metalworking fluids will definitely cause production issues—and more quickly than you think. These headaches come in four varieties:
- Stains & Corrosion: Corrosion and stains may appear on workpieces or equipment. Bacteria contribute to corrosion in two ways. First, they eat the corrosion inhibitors out of your fluid package. Second, their waste products (organic acids, salts, and hydrogen sulfide) are all corrosive. These same by-products can also discolor pale metals.
- Degraded fluid performance: Bacteria also eat the emulsifiers meant to stabilize the oil in water emulsions. As they remove these, the oil droplets steadily get larger, the oil drifts to the surface, and your fluid stops performing as specced. This both increases tool wear and decreases part quality.
- Jammed filters: Fungus tends to form a “mat” as it grows. These fungal mats are slimy and grey, and often foul smelling; picture the slick covering rocks sitting in a sluggish creek. Fungal mats build up on system surfaces, like the walls of a tank. When they break loose, they’re ultimately caught by filters—which is good; that’s the filter’s job. But they are also really good at jamming filters, necessitating more frequent filter changes or regeneration.
Clogged plumbing: Fungal mats and bacteria colonies can collect in system plumbing. There they capture chips, swarf, tramp oil, and other residues, creating stubborn clogs.
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