In many systems, online sensors continuously measure the relative humidity and temperature of the oil. However, their measurements do not predict how the relative humidity and saturation limit react when temperatures change or even how high the total water content is. But it is precisely this knowledge that is important so that appropriate measures can be taken in good time, in order to protect the systems from malfunctions caused by free water.
OELCHECK provides a remedy and now offers two additional and completely new extra tests:
- Determination of the relative humidity in % at specified temperatures between 30 and 80 °C.
- Calculation of the water saturation curve in the range of 30 to 80 °C.
The creation of a water saturation curve requires the determination of the absolute water content in ppm using the Karl Fischer method. Water saturation is determined analogously with this value and from the relative humidity measured at a wide range of temperatures. On this basis, OELCHECK creates the corresponding water saturation curve, a new maintenance tool.
If the absolute water content (at a particular temperature) is below the water saturation curve, the water is dissolved in the oil. If the water content (at a particular temperature) is above the curve, it can be assumed that the oil is cloudy or free of water, because the oil is already fully saturated with water.
A practical example: The oil circulation system of a paper machine is filled with 5,000 litres of CLP 100. The typical water saturation in such a system is usually approx. 90%.
- The laboratory analysis at 25 °C shows a clear oil, but some water droplets have settled in the container. The Karl Fischer method determines an absolute water content of 284 ppm.
- At the time of sampling at 45 °C, a water content of 425 ppm can be calculated from the water saturation diagram.
- At an operating temperature in the oil tank of 70 °C, the oil is transparent, although the water content determined on the basis of the water saturation curve is assumed to be 927 ppm at 90% saturation.
- This means that when the oil cools down from 70 °C to 25 °C, 643 ppm of free water can separate from the oil.
For the 5,000 litres in the paper machine, this would mean that approximately three litres of free water could separate from the oil during the cooling phase from 70 °C to 25 °C.
This free water should be continuously removed during the cooling phase. Without knowledge of the water saturation curve, it would not be possible to calculate or estimate the released water content.
With the new water saturation curve, proactive maintenance with water removal methods can take counteractive measures sooner – before the water saturation limit of an oil is exceeded and water is released at standstill. Using the saturation process, checking the oil fill depending on the temperature is significantly simplified. It becomes clear whether oil maintenance measures, drying or even an oil change are necessary or whether, for example, the oil should not fall below certain standstill temperatures.