How Oil Skimming Supports Coolant Maintenance Routines

In CNC machining and other metalworking applications, maintaining a healthy coolant maintenance routine is essential.

A healthy routine fosters a fluid that supports tool life, a safe work environment, and a consistent, quality output. The goal should always be to keep coolant within the manufacturer’s recommended operating range while taking measures to remove tramp oil, metal chips, and prevent bacterial growth and concentration changes from shortening coolant life.

Tramp Oil

Tramp oil is an umbrella term referring to any unwanted oil that settles into coolant bays or sumps via machine way lubricants, hydraulic leaks, spindle oils, and greases as a result of regular operations. This can be problematic when machines are off for the weekend, as oil rises to the surface and prevents oxygen exchange. When this happens, it creates the perfect environment for anaerobic bacteria to thrive, which excrete sulfur scented hydrogen sulfide gas.

Other side effects of tramp oil contamination include coolant instability, which affects tool and machining performance as a result of increased heat transfer, and a generally shorter fluid life. In cutting tool operations, oil-laden coolant that comes in contact with hot tools may smoke, contributing to poor visibility and safety concerns for operators.

Disposing of coolant heavily concentrated with oil also tends to be more expensive than disposing of the two separately, as there are companies that can reuse or resell the separated oil for recycling.

Proactive Oil Removal

Because tramp oil is an ever-present source of contamination across the metalworking industry, oil skimming is a proactive means of routine maintenance. In using the word ‘proactive’ when we talk about oil removal, we’re iterating that removing tramp oil before it can become a shop-wide issue saves time, money, and effort.

Operating on the differences in surface tension and specific gravity between oil and water, oil skimmers use oleophilic media to pick up oil and carry it out of the fluid to be scraped into disposal containers. When installed in coolant bays, sumps, or reservoirs, they collect and remove tramp oil without picking up the coolant itself, preventing buildup and associated issues.

For one bolt manufacturer out of Cleveland, OH, tramp oil contamination in their coolant created clouds of smoke during the trimming process. The air quality and visibility in the shop became so poor that at times workers could see only feet in front of them.

The problem stemmed from machine coolant being combined with lubricating oil as it seeped from oiled parts into a common reservoir. Anytime oily coolant was sprayed on hot bolts, the oil smoked.

Struggling with the smoke, plus the replacement strain the tramp oil placed on their coolant system, they installed several oil skimmers throughout the operation. The skimmers, Model 4 Oil Grabbers, were able to collect and remove tramp oil from coolant reservoirs at a rate of roughly 32gph. By operating continuously, they prevent oils from accumulating so that coolant remains effective for longer periods. The manufacturer’s plant conditions improved. They replaced their coolant less frequently, and air quality and visibility throughout the shop increased.

Read the full case study here.

In Conclusion

Healthy coolant routines should include proper mixing, regular monitoring of pH levels and concentration, chip removal, regular cleaning, and of course, consistent tramp oil removal.

When incorporated into part of the larger shop routine, oil skimming helps boost tool performance, working conditions, and longer fluid life. While there are a variety of oil skimmers capable of removing tramp oil in metalworking applications, we suggest working directly with an Abanaki representative to decipher the best unit for your specific operational needs.