Grease in working parts due to the external environment (such as air, water, dust or other harmful gases, etc.), and the relative movement of working parts to produce mechanical forces (such as stamping, shearing, etc.), will be changed in two ways：

1) Chemical changes: grease components (base oil, thickener) due to the role of light, heat and air, oxidation may occur, the base oil suffered oxidation to generate trace organic acids, aldehydes, ketones and lactones and other components, thickener fatty acids, organic metal salts may decomposition and the formation of trace organic acids, etc., so the acid (grease acid value increases) lead to lubricated parts corrosion, and rust, and loss of lubrication. and rust, and lose lubrication, protection role.

2) Physical changes: Due to the mechanical effect of the grease structure deterioration and even destruction, grease consistency decline, lubrication effect is poor, or due to mechanical lubrication parts sealing conditions, resulting in grease mixed with ash, impurities and water and grease quality deterioration.

Discern whether the grease deterioration method：

a. grease with the naked eye or feel dust, mechanical impurities, or because of mixed with water grease emulsification and become white, light, or consistency significantly smaller, or have obvious grease sour odor, etc., can indicate grease deterioration.

b. Instrumental analysis method, the most direct way to distinguish is to take a small number of used samples with infrared spectrometer to determine whether the sample has 1720cm-1 absorption peak. Or determine the change in the absorption peak of the sample before and after the use of the carbonyl index of 1710cm-1 and 1378cm-1 two absorption peak ratio. Or directly determine the acid value of the sample, if the acid value is greater than 1.0mgKOH/g when the table clearly grease has begun to deteriorate.