Some fluids utilized in the manufacturing industry are water-dilutable coolants, which are oil-in-water dilutions used for machining. Coolants must operate within a specific concentration window to maintain the right amount of lubricity and additive content.
Refractometers are instruments used to obtain a °Brix reading, which measures the oil content present in a coolant mixture. Additionally, each coolant refracts light differently and therefore has its own specific multiplier, called a refractometer factor. The °Brix reading can be multiplied by the coolant’s refractometer factor to determine the coolant concentration.
Hand refractometers are the traditional method for obtaining a °Brix reading. They are generally inexpensive and can be purchased from Lube-Tech.
- Clean the sample lens underneath the window using DI water
- Add a few drops of DI water onto the lens and close the lens
- Look through the viewing lens. If the line is not reading zero, use the adjustment screw to adjust this reading to zero
- Clean off the lens
- Place a drop of sample on the sample lens beneath the clear window
- Look through the viewing lens to obtain a reading. If the line is clear and crisp, the coolant is in great condition. If the line is hazy, the coolant may be dirty and unstable
- Clean off the lens with DI water
Digital refractometers are becoming more and more common to the industry. They rely on digital optics to obtain a °Brix reading. These can also be purchased from Lube-Tech.
- Clean the lens using DI water
- Place a few drops of DI water on the lens to cover the seeing eye, then close the cover
- Press the GO button to turn on the refractometer. Press the MENU button on the display panel until “Set Zero ?” appears on the screen. Press the GO button
- Wait until the display reads “Ready”. At this point the calibration is complete. Clean off the lens
- Place a drop of sample on the sample lens to cover the seeing eye, then close the cover
- Press the MENU button until “Brix” appears on the screen. Press the GO button
- The LED will display a number on the screen. This is the °Brix reading. Record this value. Clean off the lens with DI water
Converting from °Brix Reading to Concentration
Each coolant has its own refractometer factor which can be found on a product data sheet or determined using known sample concentrations. This refractometer factor can be multiplied by the °Brix reading taken from the refractometer to ultimately obtain the coolant concentration.
% Concentration = (°Brix Reading ) x (Refractometer Factor)