Metalworking Fluid Glossary

Glossary of Metalworking Fluid Maintenance Terms

Aeration or oxygenation is the process of injecting air into your coolant sump. Just as every aquarium has something making bubbles, so should every machine sump. And the reasons are the same. Aerobic bacteria consume oxygen (O2) so that the levels of O2 will decrease, especially under floating oils. As the O2 level drops, anaerobic bacterial activity rises. And it is these anaerobic bacteria that eat your coolant.

Bacteria comes in two types as far as coolant is concerned. Both are always present in the environment. Aerobic bacteria consume oxygen and organic materials. Anaerobic bacteria hates oxygen, and loves to consume hydrocarbon based materials, like rust inhibitors and anti-emulsification agents in coolant.

Coalesce is a term indicating the collection of anything, from a water molecule to herding cows. Water vapor typically coalesces into clouds, while cows are coalesced into a barn. In our industry, we’re interested in tramp oils. In many cases tramp oils are emulsified into droplets that are so small that they don’t float any more. Forces acting upon them from turbulence and other molecules keep them from rising naturally to the surface. The coalescing media used in a typical coalescing unit is made of material that is very similar to the oils, so there is a strong attraction. Once a small droplet sticks to the coalescing media it creates a bump that makes it more likely to catch yet another droplet. Each captured droplet increases the size of the bump, and in turn increases the chances of catching another droplet. In time, the combined droplets become so large that they will float on their own, rising to the surface of the coalescing unit. This ‘cleans’ the surface of the coalescing media, allowing the process to begin again. If there were no media, these droplets would continue to circulate through the machine, never being captured.

Coolant is a soup of ingredients that have been specially blended by your coolant supplier. Two of the ingredients are rust inhibitors and anti-emulsion agents. It has been particularly designed to work with pure water at a specific concentration. It is, in fact, a type of oil.

Coolant Flux is the vertical change in fluid level in your machine’s sump between its highest and lowest values. A sump with flux of 3 inches may vary from being 6 inches deep when the machine is running to 9 inches deep when everything is off and dripped into the sump.

Floating Oils are generally bad for coolant because they create oxy-dead zones where anaerobic bacteria grow. They should be removed as quickly as possible.

Intake Attachments (also known as passive skimmers) are devices designed to work in conjunction with a pump of some kind to draw surface fluids from a sump into a collection device.

Monday Morning Smells are caused by large numbers of anaerobic bacteria decaying. Because they consume hydrocarbon-based compounds, some of their decay bi-products are HCl and H2S (hydrochloric acid and hydrogen sulfide). The HCl can appear as a greenish cloud when a machine is started after a long time of sitting idle.

Oleophilic is a term that means oil loving. Anything that attracts oil is therefore oleophilic. We know that some things attract oil better than others, especially materials made of polypropylene.

Reach is the vertical distance a skimmer must reach in order to touch the surface of your dirty coolant when your coolant is at its lowest point. The top of this vertical distance is the mounting plane of the skimmer.

Refractometer is a device that uses the properties of bending light to indicate the concentration of some material in water. Most refractometers are used to measure the amount of sugar in our beverages using a scale called Brix. In our industry, coolants are often designed to use the Brix scale, so that reading a 5 on our scale indicates a concentration of 5%.

Sump Lifetime is the time it takes for brand new coolant to ‘die,’ using your criteria for coolant death. Many continue to use coolant even after it has ceased functioning, because some components are still effective (such as lubricity). Eventually the smell, skin irritation, or something will get you to suck all the coolant from the sump, shovel out the chips, scrub the sides of the tank, clean the fluid lines, and fill it up with clean new coolant.

Tramp Oil originates as lubrication oil which then seeps out from the slide-ways and washes into the coolant mixture, or as the protective film with which the steel supplier coats the bar stock to prevent rusting, or as hydraulic oil leaks. In extreme cases it can be seen as a film or skin on the surface of the coolant or as floating specks of oil. Tramp oil is an organic contaminant that feeds bacteria and is a potential pollutant if not dealt with properly.Tramp oil is removed with tramp oil skimmers and coalescers.