Selection and use of construction machinery grease
2019-10-15
First, the main performance indicators of grease ①, Dropping point: It refers to the temperature when heating under specified conditions to reach a certain fluidity. It can roughly determine the operating temperature of the lubricating fingers (dropping point is 15 ~ 30 degrees higher than the use temperature) ② Cone penetration: refers to the depth (unit: 1 / 10mm) that the test cone penetrates into the grease freely and vertically within 5s under the specified temperature and load. It is a measure of consistency and softness. ③. Colloidal stability (oil separation): Refers to the ability to lubricate oil in the skeleton of its thickener under the action of external force, which is determined by the amount of oil. When the amount of grease released exceeds 5% -20%, this grease cannot be used basically. ④, oxidation stability: refers to the ability to resist oxidation during storage and use. ⑤, mechanical stability: refers to the ability to resist changes in consistency under mechanical working conditions. Poor mechanical stability can easily cause the consistency of the grease to decrease. ⑥. Evaporation loss: refers to the percentage of the total loss under the specified conditions. It is an important factor affecting the service life of grease. ⑦.Water resistance: refers to its ability to be insoluble in water, absorb water from surrounding media, and not be washed off by water. ⑧.similar viscosity: refers to the ratio of the shear stress to the shear rate of non-Newtonian fluid flow. When the speed is high, the viscosity is low, otherwise the viscosity is large. II. Failure analysis of grease ① Failure caused by physical factors In use, the grease will be subjected to mechanical shear and centrifugal force at the same time. Under the effect of grease, the grease will be thrown out of the friction interface to separate the oil, resulting in reduced grease oil content, reduced penetration and hardening. After a certain degree of grease It will completely fail; under the action of mechanical shear, the grease structure loves to be destroyed (such as soap fiber disengagement or orientation), causing its softening, consistency decrease, and oil growth, etc., which eventually leads to failure. Under normal circumstances, if the grease transfer speed is increased by 2000r / min, its life will be reduced by about half. Under high shear stress, the speed is doubled, and the service life is only 1/10 of the original life. ②, failure caused by chemical factors The chemical reaction between the grease and the oxygen in the air produces acidic substances. It is the first to consume the antioxidant additives in the fat, but to a certain extent, the organic acids generated will corrode metal components and destroy the structure of the fat, causing it to drip. Decrease, increase in base oil viscosity and poor fluidity. Numerous tests have shown that the higher the temperature, the more pronounced the decline in grease life. For example, if the temperature is...