What to do if gear oil has high viscosity and poor filterability?
June 05, 2021
How to filter high viscosity Gear Oil? how to solve this problem? Relatively low-viscosity lubricating oil, high-viscosity lubricating oil is indeed more difficult to filter. However, oil is difficult to filter, not necessarily due to high viscosity, but other reasons. 1. Poor filterability of lubricating oil: The filterability of lubricating oil is also called filterability and filterability in some places, which refers to whether the lubricating oil can flow through the filter smoothly. Therefore, first check whether the gear oil you use has good filterability. The oil has a large viscosity, is relatively viscous, and has lower fluidity than low-viscosity oils. However, in some cases, high-viscosity oils are difficult to filter not because of the high viscosity, but other reasons. The filterability of lubricating oil is closely related to three factors: the type of lubricating oil additives, the insoluble matter in the lubricating oil, and the hydrolytic stability of the hydraulic oil. Some additives in oil will affect filterability, including solid additives and viscosity index improvers. If the lubricating oil contains some precipitates, oxidation by-products, insoluble matter, precipitated paraffins, and poor oil blending techniques, the oil will contain impurities that are difficult to filter. In addition, the poor hydrolytic stability of the oil will also affect the filterability. The lubricating oil is agitated unevenly during the production process, the additives are not fully dissolved, or the lubricating oil contains some solid additives, which are easily filtered out by the high-precision filter element. This will not only block the filter element, but also affect the performance of the lubricating oil. Although most lubricant additives are in liquid form, they are easily soluble in Base Oil and can pass through high-precision filter elements smoothly. However, some additives are exceptions. Certain polymer additives, such as viscosity index improvers, at low temperatures (below 30°C), molecular chains will condense into clusters, which are easily filtered out. In some cases, even filter elements with low filtration accuracy will have this problem. When the oil temperature rises, this problem disappears because the molecules of the Viscosity Index Improver unfold at high temperatures, without agglomeration, and easily penetrate the filter element. 2. Low oil temperature: Temperature will affect the viscosity of the oil, which in turn affects the filterability of the oil. Low temperature will increase the viscosity of the oil. Therefore, during cold start, the viscosity of the lubricating oil will become greater. When the equipment is running, the oil temperature will increase and the viscosity of the oil will decrease. If the oil is difficult to filter at the cold start, you can heat the oil appropriately, or use gear oil with better low-temperature performance. Many filters have a bypass valve. During a cold start, the viscosity of the oil will cause filtration difficulties, and the bypass valve will open to allow the oil to pass through. After running for a period of time, the oil temperature rises, the viscosity of the oil decreases, and it is normally filtered through the filter element.
3. The flow rate is too high: If the oil flow rate is too high, it will cause high oil pressure. Therefore, under the premise of ensuring the flow rate, appropriately reducing the oil flow rate can avoid excessive oil pressure. Most of the fine filters or offline filters for gear oils are used at low flow rates. Generally, the flow rate can be as low as 1 gallon/minute. 4. Filter element size: Some filter elements have a larger filtration area, which can adapt to the filtration of high-viscosity lubricating oil, and the adaptable flow rate is also higher. For example, the filter element used in the bearing oil of a paper machine has many folds and a larger filter area, but the price is more expensive. But in the long run, it's worth using. 5. Material of filter element: The filter medium suitable for high-viscosity oil should have the following characteristics: dense filter holes and finer fiber of the Filter Material. Many good quality hydraulic oil filter elements belong to this type. Check the filter description when purchasing. The PQ curve can check the relationship between oil flow/viscosity and the effect on oil pressure. The depth filter is not suitable for high-viscosity gear oils. 6. The oil contains impurities: If the oil contains impurities, it is also one of the reasons for the difficulty of filtering. In addition, the oxidation of gear oil will produce some insoluble precipitates or jelly, which will affect the filterability of the oil. If the gear oil contains water, it will also cause the filter element to block and affect the filtration. Other substances are mixed into the lubricating oil, such as different types and brands of lubricating oil, or salts, chemical substances, and so on. These substances enter the lubricating oil and produce sediment after chemical reaction with the oil, causing the filter element to block. There are many reasons for impurities mixed in the lubricating oil, such as seal damage, seal selection, poor installation; failure to take anti-pollution measures, resulting in impurities in the lubricating oil, for example, a newly purchased machine is put into use without cleaning, anti-rust coating or The peeled paint enters the oil; the machine that has been stored for a long time is not cleaned, and the lubricating oil enters impurities during storage, transportation and transfer; the debris generated by abrasion causes the filter element to block and so on.
