Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE Figure 4. Swab showing rusting and presence of biofilm in the MWF emulsion
No.109 page 4
of a MWF emulsion in the sump. Microbes demand a more innovative and constantly evolving approach to prevent them from spoiling the MWF industry. Also, different geographies need different strategies to mitigate microbial problems since different geographies have different types of microbial flora. After analysing the market, problems, comparing and testing different biocide chemistries, it was observed is that there is a strong need and demand for a biocide that when added in concentrates will be robust enough to suppress the need for frequent tankside addition and which can withstand mishandling in the MWF system. Also, there is a need for a good quality fungicide that will be stable for a long time in the concentrate and can act in combination with bactericide.
Based on this knowledge, trials and testing were done to see which biocidal chemistry can fulfil these requirements. Working with available chemistries, it was found that in Indian conditions, to achieve microbial contamination and long term stability, a combination biocide should be used. Oxazolidines in combination with OIT perform better in the Indian scenario. This combination when used in new sumps or properly cleaned sumps works with maximum effectiveness and minimises biofilms formation. Biofilms can be removed from sumps during cleaning by adding suitable biofilm removal products in their washing water.
Figure 5. Swab showing rusting and presence of biofilm in the sump surface
A similar case was seen in an audit of another mid scale Indian MWF manufacturer where the issues of foul smell and fungal growth were faced in their semi-synthetic MWF at some of the machines running at their customers end in North India. They tried to rectify it using a high dosage of bis-morpholine, triazine and IPBC (3-iodopropynylbutylcarbamate) combinations doses. Although this provided temporary relief, after 5-6 months, they faced the same issue again. They asked for microbiological audit of the site. The fluid samples were taken and analysed. It was observed that the majority of the microbes found in different samples were Gram negative bacteria related to the Enterobacteriaceae family and few Gram positive bacteria. Most of the samples had 2-3 different morphotypes. Hard water as well as RO water had a contamination level of >105
CFU/ml per ml of sample. Also, after incubation, colonies of SRBs were observed.
They used tankside addition of DBNPA (2,2-dibromo-3- nitrilopropionamide) and got relief from foul smell almost immediately. In aqueous alkaline environments, DBNPA decomposes quickly and is deactivated by sulphide, so it will degrade rapidly in environments containing SRB. Ultimately, only carbon dioxide, ammonia, and bromide ion remain as end products. Similarly, they were using IPBC chemistry as fungicide in their concentrate formulation but when it was tested for the presence of IPBC using High Performance Liquid Chromatography (HPLC), it was observed that the IPBC concentration was lower than expected. The OIT chemistry was found to be quite stable in their MWF formulation compared to the IPBC.
CONCLUSION: There are a lot of factors responsible for microbial contamination
40 LUBE MAGAZINE NO.138 APRIL 2017
The proper cleaning of sumps is crucial because as these combinations controls the bacterial growth and not just kill it with brute force, any prior presence of bacterial contamination in the sumps reduces its effectiveness.
Finally, as wise men say “Prevention is better than cure”, no matter how robust the metalworking fluid is, it is always better to maintain good plant hygiene and be aware of basic microbial knowledge. After all, a little knowledge is not always dangerous!
REFERENCES: • Terry M. Williams, Best Practices for Microbial Control and Biocide Treatment of Metal Removal Fluids, Vol. 60 No. 10, Compoundings, Page 29-30
• T. Kaeberlein et al., Isolating “Uncultivable” Microorganisms in Pure Culture in a Simulated Natural Environment, Science Magazine, Volume 296, 10 May 2002
• Bergey’s Manual of Systematic Bacteriology, Second Edition, Volume One, Chapter 1 and 2, The Archaea and the deep branching and Phototropic Bacteria
• Rodney M. Donlan, Biofilms: Microbial Life on Surfaces, Emerging Infectious Diseases, Vol. 8, No. 9, September 2002
• Richard Beercheck, Replacing Formaldehyde, Page 12-18, July 2012, Lubes and Greases, Europe-Middle East-Africa
• Analysis of Global Metalworking Fluids Market, Market Research by Frost and Sullivan • Global Metalworking Fluids, Market Analysis and Opportunities, Asia-Pacific: Published March 2014, Base year 2012, Report by Kline and Company
• Michael Scholz, Update on the Use of Biocides in Metalworking Applications, Lube Magazine, No. 86, August 2008, page 19-20
• Steven J. Skerlos, Kim F. Hayes, et al, Current Advances in Sustainable Metalworking Fluids Research Paper
• Hypersensitivity Pneumonitis: Is There an Association with Triazine Biocides and Mycobacteria in Metalworking Fluids, A White Paper Produced by the Safety, Health, Environmental Regulatory Affairs Committee of the Independent Lubricant Manufacturers Association
LINK
www.dowmicrobialcontrol.com
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