What are the reasons for the failure of food grade bearing grease?
November 05, 2021
When we are using food grade bearing grease, there is grease failure. What is the situation? The factors that cause failure are also quite complex, including chemical, physical, and environmental influences, and more are the result of the combined effects of multiple factors.
The following is an analysis of the causes of grease failure: 1. Failure caused by chemical factors Bearing grease chemically reacts with oxygen in the air to produce acidic substances, which first consumes the antioxidant additives in the grease. However, the organic acid generated will corrode metal components to a certain extent, destroy the structure of the grease, reduce its dropping point, increase the viscosity of the Base Oil, and make its fluidity worse. A large number of tests have shown that the higher the temperature, the more obvious the decrease in grease life. For example, when the temperature is 90~100℃, the grease life of every 19℃ is halved, and when the temperature is 10~150℃, the life of the grease is halved every 15℃. 2. Failure caused by physical factors During use, the grease will be subjected to mechanical shear and centrifugal force at the same time, the grease will be thrown out of the friction interface to separate the grease, resulting in a decrease in oil content and a decrease in penetration and hardening, and the grease will completely fail to a certain extent; Under the action of mechanical shearing, the structure of grease is destroyed (such as soap fiber detachment or orientation), resulting in its softening, decrease in consistency, increase in oil content, and ultimately failure. Under normal circumstances, if the transmission speed is increased by 2000 rpm, the life of the grease will be shortened by about half. Under high shear stress, the speed doubles and the service life is only 1/10 of the original. 3. Failure caused by other factors It will be affected by heat, such as frictional heat generation or high temperature environment, which promotes the evaporation of the base oil of the grease, so that the amount of oil is reduced, the grease becomes hard, the lubricity becomes worse, and the lubrication effect is finally lost. Studies have shown that, for whatever reason, a grease will not work properly when its base oil content loses half. The grease in the bearing is also affected by centrifugal force. If the viscosity of the grease is not appropriate, the adhesion is not enough, the structure is not stable, and the colloid stability is not good, it may be thrown out of the bearing or severely segregated, which will also reduce the oil content. It hardens and eventually loses normal function. In addition, moisture, dust, and harmful gases in the environment where the grease is used are also important factors that degrade it. For example, if the grease is mixed with abrasion particles such as copper, iron, lead and bronze, it will catalyze the oxidation of the grease. In short, there are many reasons for the failure of grease, and sometimes it may be caused by one reason, but most of them are the result of a combination of multiple factors, or one reason is a breakthrough, and then other reasons work together. The main reason may be the quality of the grease itself, or it may be "catalyzed" by some external factors.
