Manufacturers with metalworking operations and machine shops use and dispose of a substantial amount of metalworking fluid each year. These operations have the potential to extend metalworking fluid life. Prolonging the life of the metalworking fluid and optimizing its performance are very dependent on the control of the metalworking fluid system. This control is as important as the selection of the proper fluid (please refer to OilChat #37).
Regardless of the fluid type and application, all metalworking fluids require some form of management. Neat oils are relatively easy to maintain, but they do require some management. Straight oils should be filtered on a regular basis to remove metal fines and other contaminants to provide a long service life, improved cutting performance and a high level of surface finish. The majority of cutting and grinding fluids in use today, however, are water soluble. These fluids, on the other hand, differ from straight oils because they require a higher degree of maintenance to provide extended periods of satisfactory cutting performance, bio-stability, and longevity.
When a soluble metalworking fluid is mixed with water, a new level of potential problems is presented. The coolant sump is an excellent breeding space for bacteria, fungi, yeasts, and moulds because it is dark, humid and provides an excellent nutrient source (the fluid itself) for bacteria to thrive on as shown on the right. If you are familiar with metalworking facilities you have probably encountered a variety of unpleasant odours. You must have noticed that “rotten egg” or “Monday morning” smell (bacteria) when metalworking fluids have been allowed to settle over the weekend.
The majority of cutting and grinding fluids in use today are water soluble. Over time, these fluids can become rancid or contaminated with microbiological growth. With use, fluids lose their rust control capabilities, as well as their anti-foam characteristics. During normal fluid use, evaporation of water increases the concentration of the metalworking fluid. In addition, the fluids contain the chips and “fines” from the machining operation. During use, the cutting fluid collects hydraulic oil and other lubricants from the machine tool. This oil, called tramp oil, contributes to the growth of bacteria. These micro-organisms smell like rotten eggs and shorten fluid life. The fluid is disposed of once its efficiency is lost. Good fluid management practices can go a long way towards solving fluid problems and making the most cost-effective use of metalworking fluids.
Monitoring and maintaining fluid quality are crucial elements of a successful fluid management program. Important aspects of fluid monitoring include system inspections and periodic measurements of fluid parameters, such as concentration, biological growth, and pH. Changes in optimal fluid quality must be corrected with appropriate adjustments (such as fluid concentration adjustments, biocide addition, tramp oil, and metal cuttings removal and pH adjustment). It is important to know what changes are taking place in your system and why they occur. This allows you to take the appropriate steps needed to bring fluid quality back in line and prevent fluid problems from recurring.
Many of the contaminants that cause fluids to be disposed of prematurely are foreign materials, such as floor sweepings, cleaners, solvents, dirt, tobacco, food, etc. If improved fluid life is a goal, it must start with education and revised shop practices. The first step in fluid control is improved housekeeping and sanitation. Only then control of natural metalworking fluid contaminants, such as chips, fines, tramp oil, and bacteria will be effective in improving fluid life.
The link below provides more information and advice on how to manage water miscible and neat metal-working fluids at every stage from ‘’cradle to grave”. It aims to give a broader understanding of cutting fluid management and provides practical advice to get the best results from metalworking fluids.