Refractometers – How they are used and why they are important!

A refractometer is used to measure concentrations of liquids using the refractive index. They have varying units of measure, although I see Brix, Percent, or freezing point, being most common. There will also be a designation inside the refractometer of the fluid being measured. The refractometers we supply with our chillers, read Ethylene Glycol or Propylene Glycol. Note: Ethylene glycol is not food grade and should not be used in food or beverage applications. 

We use Propylene glycol as the heat transfer fluid in our chillers. For an example a 35% propylene glycol mixture is required. When checking the concentration, you will take a sample from the chiller reservoir or process piping. Make sure the system has had ample time to circulate before taking a sample for a reading. I find that pulling a sample strait from the reservoir using a tape measure is easiest. It may sound funny, but I have had people drop things in the reservoir before and it turns in to a nightmare!  Using a tape measure larger than the fill spout, run the tape down into the bath and pull out a few drops. Then you will take your refractometer lift the illuminator flap and drop a few drops on to the glass under it. Once you have your sample on the glass, close the illuminator flap and smooth out any air bubbles that might have formed between. Now you will look through the eye piece of the refractometer to view the concentration. There will be a separation of color inside between blue and white. This is indicating the concentration of the applied sample. Find the correlating propylene glycol reading inside and you are done. 

In my experience, a poor glycol mixture is the number one cause of chiller failure. Most people have a misconception that the glycol mixture is freeze protection for ambient temperature outside. Although it does serve this purpose, the glycol concentration is to provide freeze protection in the chiller evaporator (heat exchanger). This is the part of the system where the glycol mixture is being cooled by the refrigerant. The refrigerant temperature in the evaporator commonly reaches 15°-25° cooler than the set point of the chiller. If you plan on running a 28° setpoint in a brewery you will need freeze protection good for about 25° cooler than that set point. Without the proper propylene glycol mixture, you can freeze the fluid in the evaporator and cause catastrophic damage to your chilling system. To emphasize the importance of a proper glycol mixture G&D sends a complimentary refractometer with every chiller. Of course, a different refractometer may be used if you have one on site. For reference a 35% mixture should read 24.75 brix. Also, a 35% propylene glycol mixture will read a 2f freezing point. 

Don’t hesitate to give us a call at 1-800.555.0973 or email our Tech Support team at info@gdchilllers.com and they will assist you. G&D offers 24/7 service to help keep things running smoothly. We’re big enough to produce, small enough to care.