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Maintenance Strategy

Increase profits by recycling metalworking fluids

Leaders in the metalworking and metal forming industries understand fluid recycling can have a positive effect on their bottom line
By Darrell Milton and Ronald Wendt March 8, 2020
Courtesy: Eriez

Coolants have improved significantly and are now better than those available 10 or 15 years ago. They last longer but are more expensive. Depending on location, coolant could cost up to $50 per gallon. Disposal costs also can vary from 25 cents to $6 per gallon.

Figure 1: Chips and solids are captured in a large basket located inside an Eriez sump cleaner. Courtesy: Eriez

Figure 1: Chips and solids are captured in a large basket located inside an Eriez sump cleaner. Courtesy: Eriez

Figure 1: Chips and solids are captured in a large basket located inside an Eriez sump cleaner. Courtesy: Eriez

A coolant can be up to 10% concentrate mixed with 90% water. Companies often pay to dispose of the used coolant and refill machines with new, greatly increasing equipment maintenance costs.

Recycle to save coolant costs

Metalworking shops have cradle-to-grave responsibility for coolants, even if a certified company is hired for their disposal. Federal and state authorities can hold the generator of the waste accountable for cleanup costs for improper coolant disposal, which can cost a company money and reputation.

Figure 2: Sump cleaners easily move from machine to machine. They reduce machine cleaning labor and downtime. Courtesy: Eriez

Figure 2: Sump cleaners easily move from machine to machine. They reduce machine cleaning labor and downtime. Courtesy: Eriez

Fluid recycling can change this scenario. Companies can save up to 60% of the coolant concentrate by removing tramp oils and solids. While this is a sizable payback, additional factors contribute to potential return on investment (ROI).

Tramp oil, also known as sump oil, is unwanted oil that has mixed with cutting fluid. It originates as lubrication oil that seeps out from the equipment slideways and washes into the coolant mixture, as the protective film with which a steel supplier coats bar stock to prevent rusting, or as hydraulic oil leaks.

Figure 3: This 50-gallon electric sump cleaner is a portable, powerful filter that helps shops clean machines efficiently and faster than when using a Shop-Vac or shovel and rake. Courtesy: Eriez

Figure 3: This 50-gallon electric sump cleaner is a portable, powerful filter that helps shops clean machines efficiently and faster than when using a Shop-Vac or shovel and rake. Courtesy: Eriez

Enhance machine tool performance. Removing tramp oil from the manufacturing process is critical as removal improves fluid performance and longevity, air quality, bacterial resistance, corrosion resistance and tool life. Removing small fines leads to better tool life, better part finish and reduced machine tool wear.

Improve air quality. Fluid recycling can limit liability and increase worker health and safety. Removing tramp oil from coolant regularly results in less airborne oil mist, which improves air quality. Maintaining a cleaner working area also reduces the amount of slippery moisture on floors, contributing to a safer work environment. A fluid recycling program also helps companies achieve and maintain ISO 14000 status.

Figure 4: Dirty coolant is vacuumed from the machine’s sump. Courtesy: Eriez

Figure 4: Dirty coolant is vacuumed from the machine’s sump. Courtesy: Eriez

Eliminate bacteria and minimize odors. While most machines have a system to remove most of the chips, smaller fines left behind settle in the tank. Because the residue contains anaerobic bacteria, these leftover fines often form as smelly, greasy sludge on the bottom of the tank. There is no effective process or coolant additive to penetrate the sludge and kill the bacteria. It must be physically removed regularly. Using a sump cleaner, a CNC machine tool sump with 50 gallons of coolant and 20 pounds of sludge can be cleaned in 10 to 15 minutes, with the filtered coolant returned to the sump for reuse.

A sump cleaner filters the fluid it removes from the sump, making it possible to pump the filtered fluid back into the sump. This reduces the need for new coolant concentrate purchase and disposal. Customers using a sump cleaner typically see an ROI in just a few months and continue to save money.

Cleaning coolant regularly pays off. Disposing of coolant without cleaning the machine afterward results in downtime and worker intervention. New coolant immediately mixes with bacteria, which shortens its life. Cleaning machine tool sumps and the coolant regularly improves the life of the coolant and reduces costs.

Fluid recycling approaches

Acceptable solutions and the accompanying equipment to keep fluids clean are numerous and depend on the complexity of machinery and the manufacturing process. Fluid recycling equipment choices include sump cleaners, coolant recycling systems, high speed centrifuges, coalescers, oil skimmers, permanent magnet filters and magnetic chip conveyors.

Figure 5: Clean coolant is returned to the machine tool. Courtesy: Eriez

Figure 5: Clean coolant is returned to the machine tool. Courtesy: Eriez

Fluid recycling equipment can be portable to treat fluid at the machine, or a centrally located coolant recycling system can be used based on customer needs and desires. For example, companies can achieve an excellent ROI with a simple sump cleaner instead of the traditional time-consuming methods used to dispose of fine particulates. A sump cleaner is a portable, powerful filter that helps shops clean machines efficiently and faster than a Shop-Vac or a shovel and rake. A sump cleaner reduces labor and downtime for cleaning the machine.

Figure 6: Eriez coalescers are positioned next to a sump to remove tramp oils. Courtesy: Eriez

Figure 6: Eriez coalescers are positioned next to a sump to remove tramp oils. Courtesy: Eriez

Looking ahead

The economic benefits of recycling metalworking coolant are many. The larger the shop, the larger the potential savings. Each time the coolant is reused, money is saved through decreased coolant purchasing and disposal costs. With attention — primarily by ensuring contaminants do not begin to interfere with performance — most coolants can be used many times before they must be replaced.


Darrell Milton and Ronald Wendt
Author Bio: Darrell Milton is director of heavy industry at Eriez; Ronald Wendt is fluid recycling product manager at Eriez.