By CbS | 26-May-2021 | Contamination in Hydraulic Oil? We got a solution
Hydraulic oil is a sensitive mineral based oil and is used widely in the manufacturing units to transfer power in hydraulic machinery. However, hydraulic oil is also responsible for lubrication, cooling, sealing and removing contamination and wear materials.
Contamination in Hydraulic Oil? We got a solution
The three most common varieties of hydraulic oils found on the market today are petroleum-based (mineral) oil, water-based oil and synthetic oil. Biodegradable oils are becoming increasingly important.
Petroleum-based oils are made by refining crude oil to a desired level. Additives are added to improve lubricant performance. These oils offer a lower cost alternative to other oil types and performance is often adequate.
Water-based oils are the least common of the fluid types. These fluids are typically required where there is a high probability of fire. They are more expensive than petroleum but less expensive than synthetics. While they offer good fire protection, they do lack wear-protection abilities.
Synthetic oil is a man-made chain of molecules that are precisely arranged to provide excellent fluid stability, lubrication and other performance-enhancing characteristics. These oils are great choices in challenging conditions (such as very high or low temperature), however they can have disadvantages such as high cost, toxicity and potential incompatibility with certain seal materials.
Demand for equipment operators to use biodegradable oils has increased recently with concern for the environment. However, these oils are still costly and suffer from technical issues such as difficulty in avoiding contamination with mineral oils as well as compatibility with seal material.
Types of contamination
Contamination in hydraulic systems can be classified into particle contaminants (Metal particles from wear, dirt ingression) or chemical contaminants (water, air, heat, etc). Examples of damage from contamination are: accelerated component wear, orifice blockage, formation of rust or other oxidation, depletion of additives, formation of other chemicals, oil degradation.
Particle contaminants
Particle sizes are generally measured in micrometers or microns. Some examples of microns: Grain of salt 100 microns, human hair 70 microns, lower limit of visibility 40 micron, milled flour 25 micron, average bacteria 2 micron. Note that most damage-causing particles in hydraulic or lubrication systems are smaller than 14µm micrometres, so they cannot be seen.
Chemical contaminants
Water
The most common chemical contaminant in hydraulic systems is water. The presence of water in hydraulic oil can have wide-ranging effects on system components because of its effect on the physical and chemical properties of hydraulic oil. Rust in tanks, reduced lubrication characteristics resulting in accelerated metal surface wear are some of the most obvious physical results of excessive water, however the effects could be as diverse as the jamming of components due to ice crystals at low temperatures. Chemical effects include additive depletion or deposition, oxidation, unwanted reactions which can result in the formation of acids, alcohols or sludge. Oil becomes cloudy when it’s contaminated with water above its saturation level. The saturation level is the amount of water that can dissolve in the oil’s molecular chemistry and is typically 200 to 300 ppm at 20°C for mineral hydraulic oil. SKF state that hydraulic oil containing just 0.1% water by volume cuts bearing life in half, while 1% reduces bearing life by 75%.
Air
Air in a hydraulic system can exist in either a dissolved or entrained (undissolved, or free) state. Dissolved air may not pose a problem, providing it stays in solution. When a liquid contains undissolved air, problems can occur as it passes through system components. There can be pressure changes that compress the air and produce a large amount of heat in small air bubbles. This compressibility of air means that control of the system is lost. Air bubbles and frothing in the oil reservoir can cause major damage to pumps or it can also cause oil to “boil” out of the tank.
Heat
Excessive heat in hydraulic systems can also result in additive depletion or chemical changes to the oil.
How we can increase the life span of the Hydraulic Oil
While using hydraulic oil we often face problem in maintaining the NAS Level in the Hydraulic System. This can be due to presence of dusty environment and also because of internal wear and tear. Where as manufacturer of Hydraulic oil commit NAS level between 5-10, but as soon as the new barrel is opened the NAS level raise to above 10. The issue of mixing of moisture due to water/coolant leakage in the system and also due atmospheric condition is also common.
CbS with its Hydraulic Oil Filtration Machine, provides complete solution to this condition of oil by pre-heating the oil and treat under vacuum dehydration leaving the oil moisture without affecting the chemical properties of the oil. CbS provides closed loop circulation of oil through series of high Beta Ratio Cartridge filter that enhance the quality of oil NAS 5 and below.
