Water Contamination in Oil - Kittiwake

1 Water Contamination in Oil Introduction Do you dare let this happen to your components? Water is widely considered as the second most destructive Contamination to a lube system, after particulate Contamination . This article will focus on how Water exists in oil, the effects of Water on oil and lube systems and measurement of Water amount in oil, as well as setting alarm targets for Water levels in oil. Where does Water come from? Water in lubrication systems can originate from the environment, such as rain or moisture in the air. Leakage, damaged gasket on reservoir covers, underperforming air breathers, or a damaged wiper on a hydraulic cylinder are also possible sources. Condensation of air in oil reservoirs due to temperature difference between day and night will turn any moisture in the air into Water droplets, mixing with the oil.

2 A damaged Water -based cooling system in a steam application is another potential Water source. How does Water exist in oil? Water in oil can exist in three stages: dissolved , emulsified and free. Below saturation level, the molecules of Water are dispersed alongside oil molecules, resulting in Water in the oil that is not visible. This is known as dissolved Water , the least dangerous Water state to a lube system. When the amount of dissolved Water exceeds the saturation point, the oil is no longer able to absorb more Water molecules, resulting in emulsified Water . This is characterised by a hazy or cloudy appearance of the oil. Further increments of Water content in oil will result in separate levels between oil and Water forming. This state is known as free Water . Due to its higher density, the Water forms the lower layer, settling at the bottom of the sump, with the oil floating on top.

3 However, emulsified Water will also be present in an intermediate phase, continuing to circulate in the lube system. Figure 1 shows the visible difference between dissolved , emulsified and free Water within oil samples. The saturation level of the oil is important, as it determines the amount of Water that can be held before an emulsion will develop. Saturation level depends on base oil type, additive package, temperature and pressure. A highly refined mineral oil with minimum additive level has a saturation level of about 100 parts per million (ppm) at 70 F, whereas ester-based hydraulic fluids can have saturation levels of more than 3000 ppm at 70 F. Figure 2 shows the saturation level curve of a typical turbine lube versus temperature. dissolved Water Emulsified Water Free Water Figure 1: dissolved , emulsified and free Water Figure 2: Saturation curve for a typical turbine lube oil (graph from Noria Corp) Effect on Oil Physical Higher viscosity Reduced load carrying ability Chemical Hydrolysis formation of acids, sludge and varnish Reduced dielectric strength (transformer application) Aeration foam formation and air entrainment Additive depletion Effect on machinery Corrosion on metal surfaces Loss of lubrication film strength Increased wear Cavitation Filter plugging What type of damage can Water do?

4 The effect of Water in oil is twofold, destroying both the beneficial physical and chemical properties and characteristics of the oil. This can lead to machine component damage. Based on a study by Cantley in 1977, it is estimated that bearing life can be extended by a factor of five if the oil contains only 25 ppm Water compared to 400 ppm, close to the oil saturation level at a test temperature of 150 F. Figure 3 shows the adaptation of Cantley s findings and the strong correlation between Water content and relative bearing life. Figure 3: The relationship between Relative Bearing Life and Water Content in Oil (graph from Noria Corp) Figure 4 illustrates Relative Wear Rates for similar systems running with different amounts of Water in oil. It shows that component wear rate directly correlates with the Water content in the oil.

5 How is Water in oil measured? Water in oil can be measured in 3 ways; on-site by sampling, in the laboratory and online in real time. 1. On-site (offline application) Crackle Test The most expedient and economical way to determine Water content in oil. Two drops of oil are placed on a hot surface (130 C) and any bubbling or crackling is observed. The size of bubbles may give an indication of the amount of Water in the oil (Figure 5). However, due to its course and unitless results, a crackle test is suitable only as a screening test. Figure 4: Relative wear rate vs. test time (graph from Noria Corp) Figure 5: Water in oil determination by the crackle test Calcium Hydride Test One of the most widely used methods on-site; this method uses a pressurised call containing the oil sample and a chemical reagent (calcium hydride).

6 Water in the oil reacts with the calcium hydride and forms hydrogen gas. The cell is shaken vigorously to accelerate the reaction. A change of pressure due to the hydrogen build up is detected by a pressure sensor and this is converted to a Water content figure, either in % or part per million. The advantages of this method are a very fast turnaround (less than 4 minutes per test) and a low cost per sample. The electronic Water in oil test developed by Kittiwake (Figure 6) is able to detect Water content between 100 ppm to 25,000 ppm, with an accuracy of A variation, based on the same principal, is the Kittiwake DIGI Water in Oil Test Kit (Figure 7) with a detection range of 200 ppm to 200,000 ppm. Figure 6: Kittiwake Electronic Water in Oil Figure 7: Kittiwake DIGI Water in Oil 2. Laboratory Karl Fischer Method One of the more accurate Water tests, able to measure as low as 10 ppm of Water in oil, but usually only available at a full service laboratory.

7 A disadvantage of the Karl Fischer Water test is that it is expensive and often time consuming when Water concentrations are high. Fourier Transform Infra-Red (FTIR) FTIR is used as a rapid test for multiple parameters on an oil sample. Infra Red light is passed through a sample of oil and the absorption at different wavelengths in the optical spectra is measured and from this, the concentration of Water can be determined. The technique also allows Nitration, Oxidation, Soot Concentration, Phosphate Anti-Wear and Anti-Oxidant depletion amongst other parameters. Traditionally a lab based test due to the sensitivity of the equipment, FTIR devices, such as Kittiwake s FTIR3 Oil Analyser, are now available for field use. Figure 8: Water by Karl Fischer test method Figure 9: Kittiwake s FTIR3 Oil Analyser 3. On-line (Real Time Measurement) Moisture Sensor As the critically of Water ingress increases, continuous monitoring of Water in oil may be needed.

8 On-line Moisture Sensors can be installed on machines where continuous, 24/7 monitoring is required. Kittiwake s Moisture Sensors measure the Relative Humidity of oil (resulting from dissolved Water within the lubricant). Using a combination of a proven thin film capacitance sensor combined with a smart algorithm, the device measures both the temperature and % Relative Humidity Value. On-line Infra-Red Measurement Another advanced online instrument to detect Water in oil is WaterSCAN, developed by Kittiwake . This measures the Water content in parts per million within the oil by utilising absorption of infrared light by the Water in the oil. This method has the advantage of being able to measure the total Water content ( dissolved , emulsified and free Water ). It can also measure soot content within the oil at the same time data is logged within the device and alarms can be set for notification purposes.

9 The data can also be transferred directly to a PC or downloaded via a USB drive. Figure 10: Kittiwake Moisture Sensors Figure 11: Kittiwake WaterSCAN How much is too much Water in oil? Setting an alarm level for Water in oil is very important for machine reliability. Establishment of levels, combined with testing at proper intervals, will allow the end user to act quickly if a sudden increment of Water is detected. Best practice is to maintain Water levels at or below half of the saturation level of the oil at its operating temperature. For example, if the saturation level is 1000 ppm at 50 C (used F previously, now switched to C), the caution level should be set at 500 ppm, with the critical level at 1000 ppm. Table 1 shows the levels of dissolved , emulsified and free Water in oil that will be expected for different types of oils.

10 It is important to know the oil base oil type, additive package, operating temperature and pressure before establishing the alarm level. Oil dissolved (ppm) Emulsified (ppm) Free (ppm) New hydraulic fluid 0-200 200-1000 >1000 Aged hydraulic fluid 0-600 600-5000 >5000 New R&O Oil 0-150 150-500 >500 Aged R&O Oil 0-500 500-1000 >1000 New crankcase oil 0-2000 2000-5000 >50000 Case Study Water ingression in a plastic injection moulding machine. Location: Shah Alam, Selangor, Malaysia. Date: March 2007 Overview The plant has about 20 plastic injection moulding machines, producing spare parts for automotive manufacturers in Malaysia. Most of the machines are running 24 hours a day, 7 days a week to meet client requirements. Machine No. 5, an 800 Tonne injection moulding machine, uses hydraulic oil, ISO 46 grade. The hydraulic system consists of a proportional valve, requiring ultra-clean oil.