Why Machine Coolant Becomes Contaminated

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Metalworking coolant operates in a demanding environment. During normal machining, coolant can become contaminated with tramp oil, metal fines, organic material, bacteria, and other debris that gradually affect fluid condition and performance.

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One of the most noticeable warning signs is the familiar sour or rotten egg smell that can develop inside a CNC coolant reservoir. That odor is often associated with microbial growth, particularly when coolant remains stagnant for extended periods or operating conditions allow bacteria to multiply.

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Tramp oil can make the problem worse. Hydraulic oil, way lubricant, gearbox oil, and other machine lubricants can enter the coolant reservoir and collect on the surface of the fluid. When contamination continues building, shops may find themselves replacing coolant more frequently, cleaning reservoirs more often, and losing productive machine time.

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The Big Sky Decon Coolant Decontamination Unit was developed to address several of these coolant-management problems within one mobile system.

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More Than a CNC Coolant Skimmer

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The CDU is not simply an oil skimmer and it is not simply a UV-C light.

It combines multiple coolant-maintenance functions into one portable unit.

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• Coolant circulation: Coolant is pumped from the machine reservoir into the CDU and continuously circulated through the treatment system.

• Tramp oil separation: Unwanted oil can be separated from the coolant and collected in an external container.

• UV-C treatment: Coolant passes through UV-C exposure designed to address bacteria associated with contaminated and foul-smelling coolant.

• Coolant return: Treated coolant is returned directly to the machine reservoir.

• Portable operation: The rolling stainless-steel unit can be moved between compatible machines throughout a shop.

 

This gives machine shops a way to treat coolant where it is being used instead of automatically draining an entire reservoir when odor and contamination begin to develop.

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What Causes the Rotten Egg Smell in CNC Coolant?

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Bad-smelling CNC coolant is more than an inconvenience for employees working around the machine.

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A strong sour, musty, or rotten egg smell can be a warning that microorganisms are multiplying inside the metalworking fluid system.

Stagnant coolant can be particularly susceptible. Machines that remain unused overnight, over a weekend, or during longer shutdowns may develop areas with reduced circulation where microbial activity can increase.

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The Occupational Safety and Health Administration recommends monitoring metalworking fluids for conditions including concentration, pH, microbial levels, tramp oil, and suspended particulate matter. OSHA also notes that foul-smelling fluid commonly indicates uncontrolled microbial growth.

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Machine shops can review OSHA's Metalworking Fluids Safety and Health Best Practices Manual for additional guidance on metalworking-fluid management.

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The CDU gives shops a non-chemical UV-C treatment method specifically designed to address the bacterial component of this coolant problem

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How the CDU Helps Control Tramp Oil

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Tramp oil is unwanted oil that enters metalworking coolant from sources such as hydraulic systems, way lubrication, gearboxes, and other machine components.

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Removing that oil is an important part of maintaining water-miscible coolant.

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The Big Sky Decon CDU includes an oil-separation and skimming process that allows unwanted oil to be collected externally while the coolant continues through the treatment system.

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This is an important advantage because machine shops do not need to choose between an oil skimmer and microbial treatment. The CDU was designed to address both issues as part of the same coolant-maintenance process.

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Can the CDU Help Extend CNC Coolant Life?

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Extending coolant life is one of the primary goals of the Coolant Decontamination Unit.

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Coolant replacement involves more than purchasing another drum of concentrate. A complete change can also require employee labor, machine downtime, removal of old fluid, reservoir cleaning, disposal, preparation of new coolant, and time before the machine is back in normal production.

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By controlling bacteria, separating tramp oil, and continuously circulating existing coolant, the CDU can help shops maintain usable coolant longer when the fluid is otherwise kept within the coolant manufacturer's recommended operating specifications.

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Actual coolant life will vary based on coolant formulation, machining load, reservoir size, water quality, contamination, maintenance practices, and other operating conditions.

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For a deeper look at these costs, read Maximize ROI in Your Machine Shop With the Coolant Decontamination Unit.

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Real-World Coolant Results at Big Sky Decon

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Big Sky Decon not only manufactures the CDU. The company also uses the system within its own manufacturing operation.

Big Sky Decon reports that coolant in three machines at its manufacturing facility has remained in service for more than three years without requiring replacement.

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According to the company, that has resulted in:

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• Elimination of coolant odor associated with bacterial contamination

• No additional coolant disposal or replacement costs on those machines during that period

• Reduced machine maintenance and cleaning labor

• More than $10,000 in reported coolant replacement savings

 

Those results reflect Big Sky Decon's own facility and should not be interpreted as a guaranteed coolant lifespan or savings amount for every machine shop. Every coolant system operates under different conditions.

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One CDU Can Serve Multiple Machines

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Many machine shops operate several different types of machining equipment, which makes permanently installing a separate coolant-treatment system on every machine impractical.

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The CDU was designed with mobility in mind.

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The stainless-steel system is mounted on a rolling stand so it can be moved from one coolant reservoir to another. Big Sky Decon designed the CDU for applications including:

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• CNC mills

• CNC lathes

• Drill presses

• Saws

• Other machining equipment using compatible coolant reservoirs

 

This allows a shop to build coolant treatment into its preventive-maintenance schedule and move the CDU wherever it is needed.

See the CDU and other Big Sky Decon equipment in operation on our videos page.

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Use the CDU as Part of a Preventive Coolant Maintenance Program

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The best time to address contaminated coolant is usually before the sump becomes severely fouled.

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Machine shops should continue monitoring the condition of their coolant and follow the coolant manufacturer's recommendations for concentration, pH, water quality, filtration, and general fluid maintenance.

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Operators should watch for warning signs such as:

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• Rotten egg or rancid coolant odors

• Tramp oil collecting on the coolant surface

• Changes in coolant color or clarity

• Persistent foaming

• Slime or visible biological growth

• Metal fines and accumulated debris

• Repeated bacterial problems

• Shorter-than-expected coolant life

• Frequent sump cleanouts

 

The CDU should complement good coolant management rather than replace it.

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Machine leaks should still be repaired, metal fines should still be filtered or removed, coolant concentration should still be monitored, and severely degraded coolant may eventually require replacement.

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What the CDU gives machine shops is another tool for addressing contamination before repeatedly dumping usable coolant becomes the default solution.

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Reduce Coolant Replacement, Disposal and Machine Downtime

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The real cost of bad coolant reaches beyond the coolant itself.

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Every unnecessary coolant change can mean stopping production, assigning employees to clean a machine, removing contaminated fluid, managing disposal, preparing a replacement mixture, and bringing the machine back into service.

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A coolant-maintenance strategy that extends usable fluid life can therefore affect several operating costs at once.

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The Big Sky Decon Coolant Decontamination Unit was designed to help machine shops:

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• Control odor-causing bacteria

• Separate tramp oil from coolant

• Reduce unnecessary coolant replacement

• Reduce coolant disposal requirements

• Reduce labor associated with frequent sump cleanouts

• Reduce machine downtime related to coolant changes

• Maintain coolant across multiple machines using one portable system

 

Learn more about how Big Sky Decon developed the system in Revolutionize Your Coolant Management With the CDU.

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Is Bad Coolant Costing Your Machine Shop?

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If your machines are dealing with persistent coolant odor, bacterial contamination, tramp oil, frequent coolant changes, or expensive disposal, the Coolant Decontamination Unit may provide a more practical approach to ongoing coolant maintenance.

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Talk with Big Sky Decon about your machines, coolant reservoirs, and current maintenance process.

Contact Big Sky Decon

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Frequently Asked Questions About the Coolant Decontamination Unit

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What does the Big Sky Decon Coolant Decontamination Unit do?

The Coolant Decontamination Unit circulates coolant from a machine reservoir through a portable treatment system. The CDU separates unwanted oil, collects the separated oil externally, exposes circulating coolant to UV-C to address odor-causing bacteria, and returns the treated coolant to the machine.

Does the CDU remove tramp oil from CNC coolant?

Yes. The CDU includes oil separation and skimming as part of its treatment process. Tramp oil can be separated from the circulating coolant and collected in an external container before the coolant is returned to the machine reservoir.

Can the CDU get rid of rotten egg coolant smell?

The CDU is designed to address bacteria associated with foul-smelling and contaminated machining coolant. Because coolant odor can have multiple contributing causes, shops should also maintain proper coolant concentration, remove contaminants, correct machine leaks, and follow the fluid manufacturer's maintenance recommendations.

Does the CDU use chemicals to kill coolant bacteria?

The CDU uses UV-C exposure as its microbial-treatment component rather than relying on an additional chemical treatment during the UV-C process. Machine shops should continue following their coolant manufacturer's recommendations concerning coolant chemistry and any additives used in the system.

Can the CDU extend the life of machine coolant?

Yes, extending usable coolant life is one of the main purposes of the CDU. By controlling bacterial contamination, removing tramp oil, and circulating the coolant, the unit can help reduce the need for premature coolant replacement. Actual coolant lifespan depends on the fluid, machine, water quality, workload, maintenance practices, and contamination levels.

How long can coolant last when using the CDU?

There is no single coolant lifespan that applies to every machine shop. However, Big Sky Decon reports that coolant in three machines at its own manufacturing facility has remained in service for more than three years without replacement. Results will vary depending on operating conditions and coolant-management practices.

Can one CDU be used on several CNC machines?

Yes. The CDU is mounted on a rolling stand specifically so it can be moved from one compatible machine reservoir to another. This allows one unit to be incorporated into a shop-wide preventive coolant-maintenance program.

What types of machines can use the Coolant Decontamination Unit?

Big Sky Decon designed the CDU for use with a range of machining equipment, including mills, lathes, drill presses, saws, and other machines using compatible coolant reservoirs.

Can the CDU operate while a CNC machine is running?

Big Sky Decon indicates that the CDU can circulate coolant while machines are being used, or it can be allowed to cycle for longer periods such as overnight, depending on the machine, coolant system, and shop operating procedure.

Does the CDU replace normal coolant maintenance?

No. The CDU should be part of a broader coolant-maintenance program. Shops should still monitor concentration, pH, water quality, contamination, solids, filtration, machine leaks, and other conditions according to the coolant manufacturer's recommendations.

Does the CDU filter metal chips and fines?

The CDU is primarily designed for coolant circulation, tramp-oil separation, UV-C microbial treatment, and odor control. Machine shops should continue using appropriate filtration and chip-removal systems for metal fines, swarf, and machining debris.

Will the CDU save money compared with replacing coolant?

Potential savings can come from reduced coolant purchases, disposal costs, machine downtime, and labor associated with frequent coolant changes. Big Sky Decon reports more than $10,000 in coolant replacement savings from three machines in its own manufacturing facility after using the CDU for more than three years. Results will vary by facility.

When should coolant be replaced instead of treated?

Coolant that has reached the end of its usable life, is severely degraded, is outside acceptable operating specifications, or cannot be restored through appropriate maintenance may still need to be replaced. The coolant manufacturer or supplier should be consulted when determining whether a particular fluid can remain in service.

Where is the Coolant Decontamination Unit manufactured?

Big Sky Decon manufactures its decontamination products in Montana and develops equipment for manufacturing, law enforcement, first responders, commercial facilities, and other specialized decontamination applications.

How can I find out whether the CDU will work with my machines?

The best starting point is to discuss your current machines, reservoir sizes, coolant type, contamination problems, and maintenance process with Big Sky Decon. Contact Big Sky Decon to discuss your application or request additional information about the Coolant Decontamination Unit.