Using UV-C To Treat Coolant: A Few Questions Answered
UV-C treatment can reduce microbes in water-miscible metalworking fluids, helping control objectionable odors, instability, and premature disposal. However, it is not necessarily a direct replacement for chemical biocides. Results depend on the clarity of the coolant, circulation through the reactor, UV dosage, cleanliness of the system, and the organisms themselves. For many shops, adding UV-C to their coolant-management program is a better option than counting on it as a sole remediation measure.
In this article, we will take a closer look at how UV-C is used to treat coolant in the metalworking industry.
UV-C Can Reduce Microbial Load
Water-miscible coolants create an environment in which bacteria, yeast, and mold thrive. These microbes can cause bad odors, decreased fluid life, accelerated corrosion, and altered material compatibility. UV-C damages microbes as the fluid passes through a treatment chamber. Studies using miscible cutting fluids show that exposure to ultraviolet light can substantially reduce microbial content under laboratory conditions. UV-C does not add another biocide to the coolant, making it appealing to shops that want to reduce chemical use or have concerns about dosing at the sump.
Why Isn’t UV-C a Drop-In Biocide Replacement?
UV-C only works on microbes exposed to light. It acts on the fluid as it circulates through the reactor, but it does not provide protection within the sump, the machine’s coolant system, or the surrounding enclosure. Bacteria that have attached themselves to biofilm or have been trapped in the machining bed, stagnant lines, or sludge are not exposed to the light.
Colonization in these areas can continue to impact the sump by recontaminating the fluid. Biofilms also commonly develop in systems using chemical biocides when fluid maintenance and machine cleaning are inadequate. A shop with a highly contaminated system might need a comprehensive cleanout before UV-C can have a major impact on microbial content.
Coolant Clarity Controls UV Performance
UV treatment is most effective when the liquid in the reactor is relatively transparent. Metal fines, tramp oil, and other suspended matter can reduce penetration of the UV-C dosage. Emulsions also appear to be more challenging to treat than clear synthetic fluids.
This does not mean that UV-C is ineffective for cloudy coolant, but that reactor design, exposure time, and other factors become critically important. Thin-film reactors or proper sizing of the throughputs can expose more fluid to the necessary dose. Enhanced filtration and oil-water separation might also contribute to better results by improving both the optical properties of the fluid and the removal of contaminants not addressed by UV-C.
What Problems Can UV-C Help Prevent?
Reduced microbial load can have downstream benefits. Loss of odor and stability often indicate that the biological control of the coolant has been improved, which can lead to extended fluid life. Less frequent discharge and reclamation can reduce costs and the environmental impact of disposal. However, UV-C will not replace chemical biocides as a method of controlling the pH or other properties of the coolant. A drop in coolant performance due to tramp oil, insoluble contamination, or improper dilution still requires corrective action.
UV-C does not correct issues related to concentration, poor water quality, high tramp oil, or excessive solids content. It cannot repair fluid that has lost lubricity, antiwear properties, or other essential characteristics. Microbial content and fluid quality are two separate issues that require coordinated management.
“Bacteria-contaminated metalworking fluid is not just a maintenance issue. Once contaminated coolant reaches a worker’s skin or becomes airborne as mist, it may contribute to dermatitis, respiratory irritation, and more serious lung reactions. Consistent fluid monitoring and contamination control are essential parts of protecting the workforce.”–Jason Gardiner, CEO
A Clean System Matters More Than the Lamp
Adding a UV-C system to a contaminated sump will likely produce only marginal results. OSHA guidelines for eradicating contamination recommend cleaning the entire system, removing colonies of bacteria and other contaminants as much as possible. This includes physically eliminating the nesting sites that contribute to the proliferation of organisms.
This cleanout should not be limited to the sump itself, since the return lines, flumes, and other system features can shelter microbes from the effects of UV-C. Draining the sump removes some bacteria, but research has shown that systems inoculated with microorganisms can rapidly re-contaminate clean fluid that has been introduced to the sump.
How Should a Shop Evaluate a UV-C System?
The first step is to consult the coolant supplier. They should be able to advise on whether the product has been successfully tested with UV treatment and what parameters are important to the performance of the fluid. Measurements should be taken of microbial load, concentration, pH, odor, appearance, and corrosion protection, along with an evaluation of the fluid’s useful life.
The capacity and requirements of the UV system should be compared to the size of the sump and the flow rate of the fluid. The power of the lamps, exposure time, and the optical characteristics of the fluid must be considered to ensure the proper dosage. The reactor should be enclosed to prevent direct exposure of workers to UV-C light, which can be damaging to the skin and eyes. If biocide use is reduced, adjustments should be made based on testing rather than the simple presence of odors. Any biocide that is used should be approved for metalworking fluids and should be applied according to the manufacturer’s specifications.
The Best Answer Is Usually a Treatment Program
UV-C can extend fluid life when used with proper filtration, removal of tramp oil, maintenance of the correct concentration, and routine cleaning of the system. In an appropriate application, it can reduce the need for tank-side additives. It should not be presented as a universal chemical-free alternative to biocides. A test of the specific fluid in question is the best way to evaluate whether UV-C processing can take on more responsibility for microbial load in a given system. Contact the professionals at Big Sky Decon for more information on how UV-C treatment can help treat coolant in the metalworking industry today.
What Do Shops Ask About UV-C Coolant Treatment?
Q: Does UV-C work with every type of metalworking coolant?
A: No. Clear synthetic fluids generally provide better penetration and performance than emulsions, but formulation, contamination, and reactor design can all play a role. Coolant manufacturers and UV equipment dealers should be consulted regarding the specifics of the working fluid rather than a general category.
Q: Can UV-C clean a badly contaminated sump?
A: UV-C0__ can reduce microorganisms that pass through its chamber, but it cannot remove tramp oil, metal fines, biofilm or other contaminants from the system. A heavily contaminated machine typically needs to be cleaned and recharged before the benefits of UV-C can be evaluated.
Q: Will a shop still need to test its coolant?
A: Yes. Microbial load is an important factor, but reduced odors or signs of stability do not indicate that the fluid has the proper concentration, pH, lubricity, or corrosion protection. A testing program should always evaluate coolant performance, not simply the presence of bacteria.
Q: Can UV-C eliminate biocide use completely?
A: UV-C1__ is possible in some cases, but it should be confirmed for the fluid in the shop and the system’s requirements. Some processes may still benefit from the addition of a commercial preservative or carefully applied corrective treatments. The decision to eliminate biocide use should be based on microbial testing, fluid performance, safety, and the recommendations of the coolant supplier.