What is the effect of moisture on grease?
January 16, 2022
Moisture refers to the mass fraction of water in industrial grease, which is used to control the percentage of water in product specifications. The determination method is carried out in accordance with GB/T512 "Lubricating Grease Moisture Determination Method".
There are two forms of water in grease. One is structural water, which forms hydrate crystals. This kind of water is a stabilizer of grease and an indispensable ingredient. It is allowed to exist in grease. The other is free water, which is adsorbed or mixed in the grease, which is harmful to the grease and will reduce the lubricity, mechanical stability and chemical stability of the grease. If there is too much free water, it will have a corrosive effect on the machine parts. The effect of moisture on grease The presence of moisture in the grease will directly affect the appearance of the product, which will cause the additives in the lubricating oil to hydrolyze and precipitate, which will cause the additives to fail and reduce their function; moisture will reduce the viscosity of the oil, reduce the carrying capacity of the oil film, and even Damage to the oil film causes mechanical wear; it may also vaporize under high temperature and high pressure, forming small bubbles that burst instantly, causing cavitation wear, or vaporizing in the oil circuit, causing air resistance and blocking the oil circuit; the presence of moisture strengthens the acid The corrosive effect of metal causes the rust of the parts. The generated rust residue and metal chips will also accelerate the oxidative deterioration of the catalyzed oil, and accelerate the aging of the oil; the water and the lubricating oil will form a white emulsion after mixing and make the surface active The failure of strong detergents and dispersants and rust inhibitors will cause sludge to be produced in the oil; the precipitation produced by the hydrolysis of additives, metal particles produced by abrasion, rust residues produced by rust, and settled sludge can also block the oil circuit and block the filter. Causes insufficient oil supply to the system. The moisture in the lubricating oil increases the freezing point of the oil. When the operating temperature is low, the fluidity of the lubricating oil will deteriorate due to the freezing point, the viscosity and temperature will be deteriorated, and even ice will block the oil circuit; the moisture will also make the lubricating oil The thermal conductivity of the thermal conductivity becomes worse, such as the heating of the thermal oil system cannot rise.
Calcium-based grease contains structured water with a mass fraction of 1.5%-3%. This kind of grease containing structured water should generally be used at a temperature not exceeding 70-80°C, otherwise it will lose water, destroy the structure of the grease, cause oil-soap separation, and lose its lubricating effect. There are mainly the following ways for water to enter the lubricating oil: ⑴The raw material carries water: the Base Oil carries water during the processing and refining process, and the additive preparation process produces water. The base oil and additives are easy to absorb water due to their polarity; during the purging process, water is brought into the compressed air. ⑵Water ingress during storage and transportation: In a humid environment, the storage time of bulk oil products is too long, and the water vapor in the air condenses into liquid water and enters the oil products; rain and snow are caused by improper storage, such as light transmission holes or unclosed gauge holes. Water enters the oil; heating equipment that is in direct contact with the lubricating oil, such as steam or hot water heating facilities, causes water to enter the oil; the water in the tanker is not cleaned or rain and snow enters the oil from the manhole during transportation. (3) Water intake during use: the water produced after the lubricating oil is burned in the oil tank or chemically reacted at high temperature enters the oil, and the outside air enters the crankcase and is heated and then condenses into water and enters the oil. The cooling water leaks into the crankshaft due to inadequate sealing. Box, etc. Therefore, we must pay close attention to the patrol inspection of all hole covers in the operating procedures to control the entry of moisture into the oil during the production process; regularly clean oil storage tanks, tanks, tanks and other containers, and inspect and test the heating equipment and sealing equipment of the lubricating oil system. Maintain to prevent water from entering the lubricating oil and causing harm to the quality of the oil.
