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Is the separation of grease normal? High temperature grease models are complete!

Issuing time:2023-10-24 23:50

Is the separation of grease normal? High temperature grease models are complete!


Functional characteristics of grease


1. Assimilation


The primary characteristic of lipids is compressibility. When the external force is released, the fat flow slowly softens and the viscosity decreases, but when the work is stationary, the viscosity will be improved again in a short time (repair), which is called compressibility. Because of the characteristics of the grease, even parts that are not suitable for lubrication with grease can be moistened, and at the same time show excellent performance.


2. Viscosity


Grease is generally indicated by its surface or similar viscosity. When describing the viscosity of the grease, it is necessary to specify the temperature and shear rate. Similar viscosity coefficients are suitable for manipulating cold flow and ground pump levels.


3. Yield to limits


The limit of fat strength is the minimum shear stress required for the gradual fluidity of the test product. Also known as limit shear stress. The yield limit of grease is a function of temperature. The higher the temperature, the lower the yield limit of the fat. The lower the temperature, the greater the yield limit of the fat. The specifications are based on the type and content of the thickener and the prerequisites of the processing process of the moistening grease.


4. Low temperature fluidity


One of the key indicators to consider the grease cooling characteristics is the cold rotation, in other words, the ultra-low temperature (within -20°C) of the grease will prevent the slow speed bearing from rotating. The low temperature torque of the grease is determined by the starting torque and 60MM rotation. Indicates the mean value of the trailing torque.


5. Go low


In the specified standard oil hot fat reaches a certain fluidity * low temperature called the drop point. Grease drop point is helpful to identify the type of grease and possibly the highest working temperature of the grease. In general, for soap-based component lipids, the operating temperature should be lower than 20-30°C after dripping. The bigger the drop, the better the temperature resistance.


6. Volatilization


The evaporation level of grease is considered to be the volatiles of grease when used for a long time in a high temperature environment. The lower the volatilization level, the better. The volatilization of grease depends entirely on the characteristics of the lubricating oil and the composition of the distillate.


7. Colloidal solution reliability


The poor performance of colloidal solutions will cause serious oil stains due to the influence of heat, working pressure, centripetal force, etc. Separation is produced, and the service life is greatly reduced. It hardens the grease and loses its lubrication.


8. Oxidation stability


Oxidation stability refers to the ability of wetting grease to resist the harm of hot oxygen and maintain the use performance without changing during long-term storage at high temperature. Air oxidation reduces the content of free alkali and increases the content of dispersed organic matter, reduces the reduction point, darkens the appearance, shows the taste, hinders the consistency and strength of the mortar, and reduces the similar viscosity. Formation of corrosion products and damage to grease structure A substance that separates soap from oil. Therefore, in order to store grease for a long time, please store it in a dry and ventilated environment to prevent direct sunlight, and regularly maintain the change and corrosion of free alkali and dispersed organic matter to ensure its quality and performance.




In actual work, the grease is discharged under the action of the equipment, just like the sponge is squeezed from the water. After removing the thermal shock, some of the discharged grease can also be sucked back into the thickener.


It is composed of base oil price thickening agent additives, and the main component is base oil price (mineral oil or synthetic oil). Thickeners consist of fibrous tissues such as sponges and include base oil prices and additives. Just as extruded sponges can cause water to flow out, extruded fat "sponges" can cause base oil prices to deposit. There are two main methods of "extrusion molding" grease: mechanical extrusion molding and high temperature.


As can be seen from the above, it is normal to separate the oil. If the fat can not release the oil, the wetting depends on the price of the base oil, and the lubricating effect of the thickener is not large and will not be moistened. The oil content in the oil is related to the content of the thickener, and the composition of the oil indicates that the content of the thickener in the oil is not the same. Think about sponges. It's not hard to understand the thickener content. The higher the value, the lower the probability of foundation settlement of base oil price and the lower the separated oil. Is the thickening agent contained in the grease good? Well, not really. Obviously, if the thickener is too much, the base oil price should be firmly sucked in. How to moisten oils that can not be released from base oil prices? Therefore, it is necessary to find such a compromise in the fat thickener process.


The structure of grease shows that the separation of grease is an important process in the use of lubrication effect. However, because of temperature changes and vibration analysis (static data oil or oil infiltration), oil also brings oil during storage. In the specific link, this stress is much weaker than the thermal shock, but it can still deposit a little grease. Over time, the accumulated grease gradually forms a layer of oil. Therefore, even if a small amount of oil is separated, it does not affect the application.


Grease will cause the oil foundation to settle during storage and use. A small amount of oil separation is normal, too much oil separation will directly destroy the structure of the fat, and even lose the actual value. There are two ways to separate oil from oil: static data oil separation and trend oil separation. Apart from the objective factors of fat quality, these two factors will also lead to oil separation. Static data oil separation: affected by one of the following factors: static data oil separation: affected by storage temperature, storage time, storage standards (such as the vibration of the container and the gloss of the grease surface during storage and transportation), oil separation is relatively good: It is self-evident: The viscosity of the grease is relatively low (NLGI00, NLGI0, NLGI1), and the viscosity of the base oil is relatively low (ISO68 or lower). Under normal storage conditions, oil separation caused by this condition will not affect the lipid performance. Dynamic oil separation: Dynamic oil separation is mainly caused by extrusion molding of mechanical equipment or high temperature of commonly used grease. Dynamic oil separation has a significant impact on the application of lipids and must be controlled. Improve dynamic oil separation. Excessive addition of grease can also lead to high temperature, increased oxidation of oil air and rapid separation of base oil price and thickener.




Second, the classification and advantages of moisturizing fat


1. Calcium-based fats


Calcium-based grease (often referred to as "unsalted butter") has excellent water resistance, universal raw materials and reduced costs, making it suitable for wetting and water or wet environments in contact with a wide variety of mechanical parts. Its disadvantages are that the drop is too low, the operating temperature should not exceed 60°C, the service life is short, the temperature resistance is low, it is easy to dry in the steam, the shear stress is low in the mobile environment and its rapid application.


2. Calcium compound fat


High dripping, water resistance, excellent mechanical stability, extreme pressure, colloidal solution reliability, temperature resistance. It is suitable for wetting mechanical parts that work under high temperature and long time load, and the working temperature is about 150°C.


3. Barium grease


High dripping, waterproof, excellent mechanical stability, insoluble in gasoline and ethanol, generally used in gasoline pumps, centrifugal pumps, ships and aircraft propellers, organic chemical pumps and so on.


4. Calcium-based fats


It can be used for excellent temperature resistance, operating temperatures up to 120°C, excellent extreme pressure wear resistance, poor water resistance, exposure to water emulsion and dilute rolling bearings, especially high mechanical vibration and high temperature rolling bearings. In wet environments or parts in contact with water, do not use low speed and full load mechanical parts.


5. Lithium based grease


Lithium based grease drops too high, the operating temperature range includes -20 to 120°C, has excellent water resistance, mechanical stability, rust resistance and oxidation resistance, while potassium based grease has excellent wear resistance. It has the defect of durability and is not suitable for mixing with other oils. Easy separation of oil during storage. Compared with non-metal soap grease, its working temperature range is narrow, low water resistance, can not meet the increasingly clear provisions of modern industrial production.


6. Extreme pressure compound lithium base grease


It has high drip-pass, high water resistance, very high extreme pressure and wear resistance, and is suitable for wetting transmission gears, turbine engines, scroll rods and rolling bearings for long time loading machine equipment at temperatures from 20 to 120°C.


7. Aluminum-based grease


Adhesive force, waterproof, low drip, generally within 70°C. With the increase of temperature, the adhesion of aluminum grease to metal decreases. In general, it is only used as a defensive lipid for optical instruments, and cannot be used as a wetting device. The production process of compound aluminum grease is complicated and consumes a lot of kinetic energy. The service life of rolling bearings is shorter than that of lithium compound grease.


8. Urea-based fats


High dripping, hydrophobic, temperature resistance, excellent oxidation stability. However, in high speed and low speed cutting environments, it is expensive, low cutting resistance, mortar consistency change is obvious, soft and easy to damage. In addition, because of the high chemical properties of isonitrile as a raw material, maintenance during production and use is very strict, storage and transportation are difficult, and there are certain restrictions on application.


9. Crooked night grease


There is no lower point, the working temperature is high. However, it is easy to turn into coke at high temperatures, and seriously harm the lubrication performance. Sodium bentonite is a mineral that is difficult to remove very fine grit. Conclusion, rolling bearing is also noisy and its application is limited.


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