Monitoring and maintaining MWFs
R. David Whitby | TLT Worldwide March 2011
A well-planned and structured program is all you need to keep them in good condition.
Monitoring tests for neat MWFs generally requires the use of specialized laboratory facilities.
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Correct monitoring and maintenance of metalworking fluids, whether water-mix or neat mineral oil types, is an important part of any lubricant program. Proper management of these fluids:
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Extends the service life of fluids, saving money on purchasing and disposal costs.
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Maintains tool life and allows for more consistent, high-quality production.
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Protects machine tools from corrosion.
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Protects the health of machine operators.
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Reduces impact on the environment.
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May insulate companies against the risk of prosecution under health, safety and environmental regulations.
There are a limited number of tests that are required for routine monitoring of water-mix MWFs such as appearance, pH, concentration, tramp oil content and bacteria and fungi per ml of fluid. Test kits are now available for most of these tests next to each machine, and additional testing may be required if more information is needed. For example, to investigate a problem, solids content (fines), corrosion resistance, biocide content (if present) and further microbiological tests may be needed to identify the types of microorganisms present.
Monitoring tests for neat MWFs generally requires the use of more specialized laboratory facilities, particularly for viscosity, additive levels, acid value, water content, particulate content and metals contents.
Planning a monitoring program for MWFs is relatively straightforward, as is communicating the results of the tests, which I’ll discuss in a later column.
Most of the actions required to keep MWFs in good condition can be carried out in-house. In practice, regular control of important parameters is much better than drastic corrective action later. As such, when a very high bacterial count is found, addition of a biocide may seem reasonable to treat the fluid. This may seem to have been completely successful when a low count is found following the biocide addition. Although bacteria are very small, millions of them have a finite mass, and dead, disrupted cells are still floating around the fluid, releasing substances which could be a health hazard.
Controlling the concentration of water-mix MWFs regularly can be achieved by simply adding distilled or deionized water or additional concentrate. When the concentration increases due to water evaporation, ions dissolved in the original water are still in the fluid.
Tramp oil can be removed easily using an oil skimmer, which is situated correctly in the machine’s MWF sump (tank). Solids (or fines as they are sometimes called) can be removed using several types of systems, particularly magnetic separators, centrifuges hydrocyclones or paper or fabric filters, usually in rolls or rotary drum configurations.
Maintaining concentration and general fluid condition can go a long way toward controlling pH. The pH value provides much information on fluid condition. A fall in pH may be a sign of microbiological growth, low concentration, contamination or incipient separation. Specific additives can be used to restore pH to its correct value, but whether this is the right course of action is best decided by a specialist taking into account the overall condition of the fluid.
Controlling neat MWFs is much easier than water-mix MWFs. Again, regular monitoring pays significant dividends. Viscosity and additive levels can be adjusted with appropriate additions of components. Particulates and metals can be removed using filtration. Increasing acid values or dissolved metal ions is a sign that the fluid may need to be replaced and the tools and machine needs to be checked for corrosion or leaching.
Because many of the tasks required to monitor and maintain MWFs are relatively easy and low-cost, small and large companies are able to achieve equally excellent results.
Operators in a small company, perhaps with only two or three machine tools, should have no lesser expectation of a safe and healthy working environment than their counterparts in a large company. Management support and a well-planned, structured approach with adequate documentation are critical to success.
David Whitby is chief executive of Pathmaster Marketing Ltd. in Surrey, England. You can reach him at pathmaster@dial.pipex.com.