Maintenance of modern cutting fluids
The four cornerstones to achieving proper cutting fluid economy are chemistry, system design, maintenance, and biological protection.
These four corner stones are necessary in order to optimize for a sustainable and energy efficient usage – extending the time between changes – as well as a good work environment and health of operators. Provided, of course, that ventilation, extraction and other handling meet, and preferably exceed, the norm.
In a series of blog posts, we will go through each of the four cornerstones. In this post, we are explaining more about cutting fluid maintenance and how the need for maintenance changes as the content of the cutting fluids changes.
The importance of concentration
One of the most important parameters is the fluids' concentration. Traditionally, having the right concentration was important only in terms of having the desired lubricity. In non-sensitive processes the concentration could therefore vary greatly, with it being possible to save the fluids with the addition of biocides.
Nowadays, biocides as we know them are being phased out. They are not prohibited – but any use requires labelling, air measurements, warning texts, and documentation of management and personnel for many years. That is why many avoid using biocides completely, making the workplace as healthy and attractive as possible.
In order to obtain stable fluids without traditional biocides, the formulas have changed radically in recent years. Instead of biocides, so-called biostatic components are used. This is usually a mix of substances that create an environment unfavorable to bacteria. The components are not registered as biocides, since their primary function is not to kill living organisms but instead to maintain a high pH – however, the purpose is the same and some experts have taken to calling them 'unregistered biocides'.
Unlike the active biocides used previously, biostatic components aren’t as effective at killing bacteria at a low concentration. Therefore there is now a much higher need for precise measurements, to ensure the concentration is correct and that the liquid can deliver maximal efficiency.
Common to most modern cutting fluids is that the pH value is higher than with older formulas. Between the 80s and the 00s, the lower limit for corrective action was around 8.7. Today, it is usually recommended that pH should be at 9.0-9.2 for most liquids, as a high pH value complements the unregistered biocide package’s bacterial effect.
Worth noting is that when the right concentration is maintained in modern cutting liquids, a correct pH value is also commonly maintained since, in most cases, the pH value and buffer capacity of the concentrate is higher than before. Thus, pH acts as an important parameter in the synergistic function of the new liquids.
So, if you repeatedly suffer from a reduced pH value in your cutting fluid, we recommend using tank-side pH-adjusters, or changing the cutting fluid type. The pH and buffer of the liquid may simply be too low in relation to the actual replenishment of concentrate.
Complementing biological protection with other technologies, such as UV-technology or automatic measurement and control of concentration has become increasingly common, and ensures that the cutting fluid is not spoiled by temporary pH drops or concentration dips. It’s an investment that pays off!