The usage and environment of metal cutting fluids cause them to change over time. So, a similar product can have a very different composition after using it in certain systems for sometime. Therefore, fluid maintenance is crucial for a better application of the fluid.
Besides, keeping the properties of a fluid within the required limits can increase its life span. The parameters monitored when it comes to the correct maintenance of fluids are oil concentration, PH level, corrosion inhibition and microbial contamination.
High concentration raises the fluid costs via wasted concentrate, lowers the dissipation of heat, lubrication and foaming. Since the fluid undergoes evaporation under standard temperature and pressure (STP), the high concentration may make it more toxic as well.
High concentration mainly results from water evaporation during the machining process. On the other hand, low concentration causes shorter tool life, poor lubricity, high biological activity and a high risk for corrosion.
The fluid’s PH level shows its quality. The PH level is the measurement of a fluid’s acidity or alkalinity. Neutral PH value is usually 7. Values below 7 mean that the solution is acidic and higher values represent alkaline solutions. The recommended PH value for a water-miscible fluid is between 8.8 and 9.2.
When the PH value drops below 8.0, it means that the fluid is becoming less efficient and has a higher risk of both corrosion and microbial contamination. If the PH value exceeds 9.5, then the fluid poses a risk for dermatitis and skin irritation. The methods used for detecting the PH level are litmus paper, electronic PH meters and titration.
This can be estimated by checking the dissolved oxygen in a mixture. Aerobic bacterial growth depends on oxygen. Therefore, you can measure the dissolved oxygen and be able to estimate the biological contamination.
Testing the fluid’s corrosion properties helps to protect those metal parts that are in contact with the fluid. Corrosion protection of the fluid reduces with a complete dissolution of oil in water and this will guide you when to add oil to the system.