The
PREDICT Navigator is a portable screening device for qualifying the condition
of lubricants in non-combustion applications. This hand-held oil condition monitor
can be used at the equipment site as a stand-alone unit or as a complete system
backed by a laboratory. The typical test requires about 10 - 15 ml of lubricant
and four minutes to complete. No sample preparation is required. As a comparative
device, Navigator identifies shifts in oil characteristics relative to a reference
sample. By cost-effectively screening samples that have shifted in quality,
Navigator enables the user to focus resources on correcting problems instead
of finding them.
Navigator technology is based on the measurement of both conductivity and permittivity at four unique frequencies using a patented method of impedance spectroscopy. The frequencies were selected to maximize sensitivity to water, wear metals and oxidation. Navigator's lower sensitivity detection limits are:
- Water: 100ppm
- Wear Metals: 120ppm
- Oxidation: 7abs. units/cm (as measured with infrared)
The use of impedance spectroscopy that simultaneously combines low and high frequency analysis expands the Navigator's capability as an oil analyzer. Low frequency analysis measures changes in conductivity. Water, the primary contaminant affecting conductivity, causes a linear shift that is proportional to the concentration of water. During the low frequency test, capacitance, or permittivity, is blocked to isolate the water measurement. High frequency analysis measures changes in permittivity. Wear metals primarily cause a shift in permittivity. During high frequency testing, conductivity is blocked to isolate wear metal measurement. Oxidation is measured at both low and high frequencies making it unique relative to water and wear particles. The Navigator's response at the different frequencies identifies the presence of contamination, wear debris or lubricant degradation. At contamination levels greater than 800 ppm water and wear particles greater than 170 microns, Navigator will respond " Possible Water" or "Possible Wear >170µm", respectively.
PREDICT/DLI has learned through years of experience that each piece of equipment and oil combination is unique. Trending lubricant characteristics for one to three months identifies the normal range for each frequency. Customer programmable alarm limits are easily adjusted to bracket the typical characteristics for each Navigator measurement frequency. As additional data is collected, or if the oil type is changed, the alarm limits can be adjusted. The alarm limits are set to identify the maximum acceptable performance deterioration relative to the new reference condition. Testing oils that are within alarm limits will receive a Navigator response of "Sample is OK". For oil conditions outside alarm limits, Navigator produces an "Out of Limits" response.
Many years of laboratory experience has led to the conclusion that approximately 80% of the samples analyzed in contract laboratories are "OK", or within acceptable performance limits. Navigator cost effectively screens the samples to identify the 20% problem samples so they may be scheduled for detailed analysis at the laboratory to assess the nature, severity and root cause of the problems.
The PREDICT Navigator complements an overall oil analysis and machine condition monitoring program by providing the following onsite capabilities:
- Provides user friendly, cost effective pass/fail oil analysis screening
- Trends oil condition
- Adjusts to specific applications
- Reduces laboratory sampling costs
- Expands one’s PdM oil-monitoring program to include equipment not presently included due to cost restrictions
The benefits of identifying "Out of Limit" samples is demonstrated in the following case of a critical gearbox in a mining application. In normal service oil deteriorates, leaks from the system and is frequently sampled. Make-up oil is added as required. Addi-tionally, the unit is exposed to water and dirty conditions causing concern about contamination ingress. Significant deterioration in lube condition due to contamination leads to reduced reliability of the gearbox. Figure 1 presents water concentration trending for eleven samples analyzed by Navi-gator. The dashed lines in the graph are the recommended alarming limits for this application. An out-of-limit water condition was identified in the tenth sample and verified by the laboratory. The source of the abnormal water condition was eliminated, as such was the risk to the machine.
The example demonstrates Navigator's ability to identify out- of-limit samples from "OK" samples, reducing total lab resource requirements. This screening process will effectively reduce the overall cost of an oil analysis program. The frequency of onsite sampling can be adjusted to the application without the corresponding lab expenses.
The capability of Navigator to discriminate between contaminants is demonstrated in a trend study monitoring a large equipment reservoir in a chemical plant. The lubricant is collected from several areas, filtered and reused. The primary contaminant is water; however, occasionally wear metals and ammonia increase beyond acceptable levels. In this type of application, lubricant characteristics vary as different types of equipment are involved. The primary concern is the condition of the lubricant after filtration.
The Navigator responses are presented in Figures 2 and 3. In this study the first used oil sample was used as reference condition. The responses are compared to specific parameters on the horizontal axis. The key findings include:
- High water concentration identified by the primary water frequency.
- High wear metal concentration identified by two of the other frequencies.
- No changes in oxidation identified. Oxidation ranged from 5.6 to 6.6 absorb. units/cm.
For more information contact
Predict/DLI at 216-642-3223 or go to www.predictdli.com.
