Important indexes affecting the quality of hydraulic oil
Particle size assessment (nas1638 standard) is a simple classification method for particle size grade and quantity. Generally, impurities are divided into five categories according to their size, and the quantity of impurities is limited by different levels. According to the actual situation of oil sample, the first level beyond the limit is the next level, which is divided into 12 levels. If the oil sample test results are shown in blue in the above table.
In addition, the larger the size of impurity particles, the less the number of particles required, and the greater the impact on the quality of oil samples. Therefore, it is necessary to avoid the secondary pollution of the oil sample, that is, the precautions for the above-mentioned hydraulic oil sampling.
The following table shows the different requirements of each manufacturer for particle size:
2. The water in the oil mainly comes from the moisture, rain water and sea water in the air. It can change the acid-base value of oil, promote microbial pollution, etc. the ice crystal condensed in low temperature water is easy to cause the abrasion of accessories and sealing rings.
There are two kinds of water in oil: free water and dissolved water. In general, dissolved water needs special instruments for detection, and the detection accuracy error is large. As shown in the figure below, with the decrease of temperature, the water solubility of the oil decreases, and the dissolved water will become free water. Therefore, the accuracy of oil sample water content can be effectively improved by oil sampling (such as in the early morning) and detection in low temperature environment. This also applies to the selection time of fuel tank drain.
3. Impurities in oil mainly include: silicide (external dust, casting residues), sulfide (external dust, sealant), metal particles (parts processing, wear, coating peeling particles, etc.), aluminum alloy particles (abrasives, polishing agents, etc.), rubber particles (sealing ring wear), plastic particles (packaging residues, plastic parts wear), cotton fiber, etc The hardness of medium silicide and aluminum alloy particles is higher, and the hardness increases with the decrease of particle size, which has a great influence on the hydraulic actuator parts and sealing rings, resulting in more impurities. Pay attention to the source of impurities in the maintenance, ensure the regular replacement of various filter elements, and avoid long-term failure to keep effective control.
Other parameters such as viscosity, density, acid value, conductivity and so on are not beyond the comprehensive reflection of the above factors, and will not be described in detail.
