Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
bio-resistant metal removal fluids along with “dip slides” that can measure bacteria on one side and fungus on the other side. Also, be prepared to have an effective antimicrobial pesticide (i.e. biocide) dosing plan, in case it is needed.
Caution:
A biostable/bio-resistant fluid will be less likely to grow bacteria and/or fungus, however, these fluids typically require a minimum concentration to be effective. It is best to work with the fluid supplier before adding biocides. Other areas that can improve fluid life are controlling “dead spots” where fluids can stagnate and grow bacteria and/or fungus. As stated earlier, an excessive influx of tramp oil can overwhelm the best metal removal fluids. Therefore tramp oil ingress should be minimised as best as practical. Incoming water, even though safe to drink is not necessarily sterile and can also be a significant source of bacteria. Treating water by RO can minimise bacteria influx for potable water sources. Do not use rainwater or air conditioning condensate for water makeup into these fluids since these types of water sources can be highly contaminated with bacteria, fungus, and algae.
Additional steps to minimise fluid failure Control your concentration as close as possible to the maximum level as recommended by your fluid supplier. At a minimum, check your concentration every day and make adjustments.
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Determine fluid stability by holding a sample of the metal removal fluid in a clear glass jar for 24 hours. Take pictures before and after and compare results. If a fluid is stable, there will be minimal if any separation (see Figure 5).
In summary Metal removal fluids will undergo some level of failure during their service life. The rate of failure can be lessened to some extent. No metal removal fluid will last indefinitely. Poor control of the metal removal fluid will cost the end user money. Over-extending the life of a metal removal fluid past the failure point, can cost the end user money through the decline of machine productivity and loss of tool life.
Control Plan Summary 1. Filter fluids well - Start at 30 micron. 2. Use good water - Low hardness and low chlorides. 3. Remove tramp oil - Continuously remove or change the tramp oil type and fix leaks.
4. Control pH - Additives are required over time. 5. Use antimicrobial pesticides (biocides) properly. 6. Measure stability - Jar test. 7. Measure and control concentration regularly – There are many fluid measurement options. At a minimum, use a hand held refractometer.
John Burke is a consultant to Quaker Houghton specialising in fluid recycling and industrial wastewater treatment processes. He received his engineering degree in 1971. He has over 50 years of experience in the metalworking industry and 21 of those years with Quaker Houghton. He has 11 U.S. patents and over 50 international patents. He is the author of two chapters in the Third Edition of the book Metalworking Fluids. John has been an instructor for the STLE Metalworking Fluid Education Course for the past 26 years. He is a Certified Metalworking Fluid Specialist. Furthermore, he is an associate editor for the STLE Journal Tribology Transactions. He received the P. M. Ku Award from STLE in 2006 and has been a Fellow in STLE since 2011. In 2015 he received the John A. Bellanti Award for dedicated service from ILMA. John received an award from then President George Bush at the White House in 1991 for advances in waste minimisation.
https://home.quakerhoughton.com Figure 5: Basic Demonstration of Metal Removal Fluid Stability.
LUBE MAGAZINE NO.174 APRIL 2023
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