DEF is composed of deionized water and a nitrogen compound called urea. For the fluid to work properly, there must be roughly twice as much water as urea. Too much water and the DEF won't be able to eliminate all the NOx; too much urea and the fluid will not evaporate properly. Refractometers allow you to ensure that your DEF has the proper concentrations of water and urea.
Originally designed to test the quality of engine coolant, optical refractometers measure what happens to light when it moves through a liquid. To use one, first place a sample of the DEF on the refractometer's prism and look through the lens. The higher the concentration of urea, the more the light will be distorted, and the darker the sample will appear. You can then compare the sample to a color spectrum, which will tell you whether the DEF has the correct concentration of urea.
If you don't trust your eyes, you can also use a digital refractometer, which will calculate the concentrations of water and urea for you. This device is capable of controlling for outside temperature and other factors that can cause you to misread optical refractometers.
Another option for measuring the concentrations of water and urea in DEF is the hydrometer. Hydrometers measure the DEF's density and compare it to the density of water. To use it, pour some of the DEF in a graduated cylinder, place a weighted bulb in the DEF, and record the point at which the bulb floats freely. The higher up the bulb floats, the higher the density of the DEF, and thus the higher the proportion of urea.
Oil Test Strips
In addition to urea and water concentrations, you must also make sure that no outside contaminants have gotten into the DEF. To do this, simply place a test strip into the DEF. Contaminants will cause the strip to change color.
If you need equipment for DEF, fuel, and other industrial fluids, Innovative Fueling Solutions in Amarillo sells and installs a wide range of fuel storage, management, and dispensing products. For more information, contact us today.