70%-80% of the failures of the hydraulic press system are caused by hydraulic oil contamination. The oxidation of the hydraulic oil produces sludge, colloid, and other substances, which will cause the hydraulic system to work abnormally, block the oil circuit, and corrode the metal.

Hydraulic oil contamination is mainly manifested in two aspects:

1. Particle pollution of hydraulic oil;

2. Deterioration of oil's physical and chemical properties (such as viscosity, acidity, alkalinity, oxidation degree, etc.).

The main sources of particle pollution are:

(1) Original pollution: originates from the manufacturing, testing, transportation, installation, and other stages of hydraulic system products;

(2) The pollution brought to the system by the medium during the process of transportation, storage, oil replenishment, etc.;

(3) Particles produced by the hydraulic system after it is put into use.

The deterioration of the physical and chemical properties of hydraulic oil mainly includes:

(1) The mixing of different types of media causes chemical reactions, making the media deteriorate;

(2) During the production process, the oil temperature is too high or the oil is used for too long due to oxidation and deterioration, resulting in medium pollution;

(3) When water is mixed into the medium, the oil becomes an emulsion, which reduces the lubricating and anti-corrosion effects of the lubricating oil, and easily causes cavitation;

(4) The quality of hydraulic oil is low or inferior sealing materials are used, which will cause damage to the sealing materials and cause hydraulic oil contamination.