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Certain machines are continuously challenged by the ingression of moisture. When water mixes with a lubricating oil or hydraulic fluid, it can wreak havoc on the quality and state of lubrication. This can begin a chain of events that can quickly turn reliability into failure and safety into catastrophe.
In response to the need for a quick, corrective response at the first indication of moisture contamination, Kytola Oy of Finland has advanced a new online moisture sensor called Oilan. The innovative device is intended for use with circulating lubricating oils or hydraulic fluids. The sensor technology is based on the absorption of infrared light.
Many people involved in oil analysis are already familiar with infrared as used by laboratories to detect a host of contaminants and lubricant properties. For instance, it is common for laboratories to use infrared spectrometers to detect concentrations of soot, glycol, oxidation products, additives, fuel and water.
The method most commonly deployed is Fourier Transform Infrared (FTIR) spectroscopy involving the search and analysis of infrared absorption across a broadband infrared spectrum. In contrast, the Kytola Oy sensor uses a much simpler narrow-spectrum device, an approach that is favored by other portable and online instrument suppliers as previously reported in Practicing Oil Analysis magazine.
Oilan uses a two-channel detector to measure oil moisture levels. One channel measures the amount of water in the oil while the other is a reference channel. Water in oil accentuates the absorption intensity of the measurement wavelength called a spectral band.
The infrared absorption is determined from the difference between these two channels at the target spectral band for water. This absorption, using a calibration curve, is used to estimate the amount of water in the oil sample as traditionally presented in ppm or percent.
The Oilan device is unique in that it is an online real-time sensor dedicated to a particular machine. As such, the moisture levels of critical lubricating oils and hydraulic fluids can be continuously monitored and reported. The RS-232, 1,200-baud serial communication port will report both average and current water content. According to Kytola Oy, water can be measured up to 20,000 ppm (2 percent water).
The unit can be used with all types of mineral oils, as well as some synthetic fluids. It is worth noting that certain phosphate ester synthetic fluids are not suitable. The operating viscosity range is from 5 to 680 cSt with a line pressure range of 7 to 150 psi [.50 to 10 bar(s)]. The instrument requires a fluid flow rate of 0.1 to 0.5 LPM (0.03 to 0.13 GPM). The output signal is 4-20 mA.
Although the Oilan is designed to measure very small quantities of water in oil, the device does not exhibit sustained saturation errors if water levels exceed the measuring range. Instead, when the moisture level returns to the sensor’s measurement range the concentration can once again be reported.
Best results are achieved when fluid temperature, water drop size and pressure remain stable.
According to the manufacturer, the Oilan unit has been used successfully in many maintenance applications and was first developed for the pulp and paper industry. Once installed, the Oilan is relatively maintenance-free. There are no special cleaning requirements although its use with excessively dirty fluids is not recommended. Also, there is an occasional need for recalibration.
Kytola Oy of Muurame, Finland is a 9002-registered manufacturer of various flow and pressure measurement, control and monitoring devices for the pulp and paper, mining, steel and chemical industries. Esko Industries Ltd. of North Vancouver, British Columbia, Canada has been distributing instruments in North America manufactured by Kytola for almost 20 years.