In 1884, Frederick Taylor, an engineer at a Philadelphia machine shop, began directing constant streams of water mixed with carbonate of soda to prevent rusting. He also created a return system that drew used fluid to a holding well, then pumped it to a ceiling tank for redistribution.
All this was the very beginning of a development process that led to today’s central systems, which may hold thousands of gallons and distribute fluid to dozens of machines. The question for today’s shop leaders is, “How can we use this system in the best possible way?”
Let’s examine some best practices for use with central systems. Because there is so much variety in individual system designs and filtration methods, we’ll offer a general take on some of these methods.
Begin with a highly stable metalworking fluid (MWF)
More stability means fewer headaches in general, but especially when you’re dealing with a centralized system in which the cost of replacing fluid can be huge. As we mentioned in our recent blog on biological contamination [link to blog: Beating Back the Biologicals: Dealing With Bacterial Contamination], an outage in a 10,000-gallon central feed system can cost a shop $50,000 to $100,000 in fluid replacement or reclamation, disposal, and machine downtime.
Choose a metal working fluid that is biostable and rejects tramp oils. The newest generation of MWFs, such as the NuSol™ line from Chemtool Incorporated, are formulated for the highest degree of stability.
Maintain excellent water quality
If you’re using a water-soluble MWF, ensure your incoming water is well-treated for hardness. You not only need to protect the fluid’s integrity – hard water can change the chemistry of these types and make them more vulnerable to biological contamination – but the integrity of the distribution system. Scale from hard water can clog lines and pumps, and hard water interferes with anti-corrosion additives in the MWF, leading to internal rusting.
As we observed in our post on hard water [link to hard water blog], a deionization or reverse osmosis system will remove at least 95% of dissolved minerals.
Establish robust monitoring
Even after choosing a highly stable MWF, it’s crucial that you monitor the state of your fluid with frequent testing. Establish solid baselines and take immediate action if you see any indication of biological growth or degradation of fluid quality. At a minimum, test for product concentration, Ph and conductivity on a regular basis. Testing for bacteria, yeast, and mold is quick and easy using dip slides.
Pay close attention to the basics
As you plug in the data from your monitoring program, keep the usual common sense practices of good fluid management in place. When using water mix fluids, follow the manufacturer’s recommendations for concentration to the letter. Clean machines frequently and maintain them well to avoid tramp oil contamination.
If a problem shows up in one or two machines, it’s likely the problem is with them, but don’t assume that’s the case. Ask other operators if they have been seeing milder versions of the same issue; if so, look to your distribution system as a possible cause.
Protect against contamination from machines and external sources
Tramp oil is a common metalworking fluid contaminant. It may originate from leaky hydraulic systems, overfeeding of way lubes, or come in on parts as cutting oil or corrosion inhibitor. Tramp oil contributes to dirty systems and may promote microbiological growth. Minimize tramp oil by utilizing oil skimmers and repairing hydraulic oil leaks.
In an independent machine sump, even a small amount of contamination can be a big deal. In a central system, contaminants can be distributed to every machine in the shop, admittedly in a diluted form.
If your central system uses a floor-level collection trough or pit, take special care to guard against the introduction of floor cleaners into the fluid. The solvents and pine extracts in these cleaners can damage the chemical balance of your MWF and are difficult or impossible to counteract.