by Mark Copeland, Key Account Manager, Acculube
"If my water is good enough to drink, it's good enough to clean with, right?"
If you're cleaning your kitchen, sure. But if you're using your drinking water to clean your CNC machine or to mix with your machine's coolant, you may be secretly killing your machine.
That's because the water you add has a powerful affect on the quality of the product. Water mixable products such as coolants and cleaners are 90 percent water and 10 percent active ingredients. Bad water will turn even the best coolant or cleaner into a rust-inducing liquid.
Water varies everywhere
The problem arises in water variations across the country. First, water sources vary. A manufacturing plant may access water from a well, reservoir, lake, or river. Other factors affecting water quality include the local geology, aquatic plants residing in the water, the amount and type of sediment, and temperature. Even the basic change of seasons has an affect. A test of your water in January will yield different results than in July.
What to test for
The first step toward quality water is to test your current water supply for the following additives. Most suppliers can test your water for you or you can send it to an independent lab.
Chloride is a naturally-occurring chemical in water. It can also be added during a municipal water treatment operation. However, high levels can cause rust. The acceptable amount of chloride is dependent on the type of coolant or cleaner you use. However, a common rule of thumb is to use water with a chloride level below 20 parts per million.
Dissolved gases such as sulfate or sulfur
Similar to chloride, high levels (above 40 parts per million) of dissolved gases in the water can cause rust.
Hardness and softness
It is possible for water to be too clean. If your water is too pure, it can affect pH levels. Your water may take on an acid property and become corrosive. Some coolants contain oil and include an emulsifier to hold the water and oil together. If your water is too soft, it causes the emulsifier to foam like a detergent. If your water is too hard, the abrasiveness will ruin the emulsifier molecule and the coolant will come apart. The goal is to find the happy median between the two. Water hardness should be between 100 to 200 parts per million.
Minerals, such as phosphates, sodium, magnesium, and calcium
Using any water mixable product in a manufacturing application involves evaporation. The problem is that while the water evaporates, the minerals in the water don't. Minerals act like sand paper on a microscopic level. They break down the coolant or cleaner, reducing the product's life span. Minerals are part of the water's hardness. Again, water hardness should be between 100 to 200 parts per million.
How to fix your water
The cheapest solution to improving your water quality is to find a product made for your type of water. There are specially-formulated cleaners and coolants for soft or hard water.
However, there are some parts of the country—including parts of Ohio and Indiana—that have water hardness beyond what products can handle. When this happens, you must look into a water treatment system. The two most popular are DI (deionized water) and reverse osmosis.
Deionized water (DI)
Using chemistry, DI involves adding a chemical charge to the water to drop out the hardness. This is the process used to make bottled water. It gives you 100% pure water.
DI is less expensive to install as it doesn't need equipment. You only need to pay for the plumbing costs to set it up. However, it is more expensive to operate long-term. The chemical reaction takes place in a cylinder, which depletes and has to be replaced, sometimes as often as weekly. The average cost of a cylinder is $200.
With reverse osmosis, you install a membrane with microscopic holes that act as a filter. Forcing the water through the filter removes the minerals and dissolved gases. This approach gives you 90% pure water.
Reverse osmosis is more expensive upfront, costing about $10,000 to $20,000 for the filter unit and installation. Long-term maintenance costs are less than DI with only about $200 spent every couple of months to clean the membrane of collected minerals.
Which method to use depends on what you're manufacturing. For most industrial applications, the 90% pure water produced by reverse osmosis is enough. However, some manufacturers—such as those for medical devices—may need 100% pure water which only the DI process can produce.
For most companies, making your water good enough for cooling and cleaning is simply a matter of testing it and finding the right cleaner and coolant for that type of water. With the right combination, you can save on maintenance costs and extend the life your machines.
Mark Copeland is a key account manager at Acculube (http://acculube.com), a Dayton-Ohio based fluids supplier to American manufacturers and service providers.