The most harmful contaminants aside from solid particles are found in water. It is often overlooked as the primary root cause of machine problems when the presence of water is found. Also, premature oil degradation, increase in wear and corrosion can be caused by excess moisture contamination.
Moisture, upon contaminating hydraulic and lubricating oils, has a degrading effect on both the lubricant and the machine itself. Some additives adsorb to the water and are removed when the water separates from the oil, while others are destroyed by chemical reactions induced by water. The critical, load-bearing film strength can be reduced by rust and corrosion of the machine surface when water starts to promote oxidation of the oil’s base stock. In short, water is the main threat to the equipment and should be controlled to a greater extent. We are the trusted partner who delivers you the best water in oil monitoring tool in Dubai.
Saturation Meters
Saturation meters can be used to indirectly quantify water content when the amount of water present in an oil sample is below the saturation point. At a certain temperature, the point at which the oil contains as much water in the dissolved state is simply the saturation point of the oil.
At this point, the oil is saturated or has a relative humidity of 100 percent. Most of saturation meters use a thin film capacitive device in determining the percent saturation of used oils, saturation meters have proven to be accurate and reliable.
The contaminants, wear particles, and additives including the presence of polar species as well as temperature are the factors responsible for the accuracy of saturation meters. Also, saturation meters fail to quantify the water content accurately if the water contents are in excess of the saturation point. Despite these limitations, saturation meters can be used to determine onsite moisture contents.
Monitoring and controlling water levels in any lubricating system are important. Water is responsible for both the reliability and longevity of the equipment whether it is a hydraulic system, a steam turbine, an electrical transformer, or a large diesel engine.
The Varying States of Water
Due to the water’s chemical attraction to the fluid, single water molecules are dispersed throughout the oil. The amount of water dissolved by oil depends on many factors such as viscosity, base stock type, impurities, and additive package.
In addition, the dissolved volume is a function of the oil’s temperature, so the relative humidity is reported (depending on the temperature). Oil is saturated when it has dissolved all the water it can at a given temperature. It is difficult to control dissolved water, but its effects on the machine and oil are minimal.
The saturated oil reaches a point at which water cannot condense into free form during a temperature decrease. This is called the dew point temperature. Free water is the other state in which water coexists with oil. Undissolved globules of water in the oil are considered to be in a free state.
Generally, large globules settle at the bottom of the reservoir or sump. Mechanical equipment, on the other hand, crushes water into so small globules that a stable emulsion is formed because of the shearing forces.
Emulsions are composed of chemically insoluble substances, such as oil and water, which coexist in a stable state. The addition of additives and impurities which decrease the surface tension of the oil can strengthen the emulsion. Free and emulsified water poses the greatest risk to the machine and the lubricant and should be placed under strict control.
FTIR Analysis
The FTIR method can be used to screen samples containing in excess of 1,000 ppm of water, provided a valid new oil baseline is available for spectral subtraction. However, due to its limited precision and comparatively high detection limits, FTIR is not adequate in many situations where precise water concentrations below 1,000 ppm or 0.1 percent are required.
Visual Crackle Test
You can determine the presence of water in oil by performing a Visual Crackle Test. Despite its effectiveness in determining free and emulsified water down to 500 ppm, this test has a lot of limitations, such as being nonquantitative and relatively subjective.
With entrained volatile solvents and gases, false positives are possible. However, the crackle test will always have a place as a screening tool both in the lab and in the field where a quick yes or no answer is needed for free and emulsified water.
Karl Fischer Moisture
When accuracy and precision are required in determining the amount of free, dissolved, and emulsified water in an oil sample, the Karl Fischer Moisture test should be used. However, even within the scope of Karl Fischer’s testing, there are several methodologies that are used.
Karl Fischer’s procedures are similar. Oil samples are titrated with Karl Fischer reagent until an endpoint is reached. Different methods of testing depend on the amount of sample used and the method for determining the titration endpoint.
The most reliable method is ASTM D6304, complete with distillation. With the co-distillation method, the oil sample is heated under a vacuum so that any water present in the sample evaporates. The water vapors are condensed and dissolved into toluene, which is then titrated using the D6304 procedure.
Since the additives and other interfering contaminants in used oil samples remain dissolved or suspended in the oil, the condensed water in the toluene is free from interference and represents the true amount of water present in the oil sample.
Calcium Hydride Test Kits
An easy and convenient way to determine water concentrations is to use a calcium hydride test kit. Hydrogen gas is produced using the well-known reaction between water and solid calcium hydride. The amount of hydrogen released is directly proportional to the amount of water present in the sample since the reaction occurs stoichiometrically.
In this case, the water content of the sample can be determined by measuring the rise in pressure in a sealed container due to the release of hydrogen gas as water in the sample reacts with calcium hydride. If used correctly, it is said to be accurate down to 50ppm free or emulsified water.
Dean and Stark Method
In the past, the Dean and Stark distillation method (ASTM D95) was used to determining water content in oil. Currently, this method is not commonly used in production-style oil analysis labs because it takes a relatively large sample to ensure accuracy.
Oil samples are directly distilled in this method. As the oil is heated, any water present in it vaporizes. The water vapors are then condensed and collected in a graduated collection tube, such that the volume of water produced by distillation can be measured as a function of the total volume of oil used.
Conclusion
Always remember, like all tests, the techniques used to detect water in oil have their own strength and weaknesses. Hence, it is important to wisely select the one that meets your needs and desired detection limits. For the best water in oil monitoring tool in Dubai, let us know.
