What are the requirements for the working medium of a four-column hydraulic press?

What are the main requirements for the hydraulic working medium of a four-column hydraulic press? Today I will introduce to you:

The viscosity is appropriate and changes little with temperature. If the viscosity of the working medium is too high, the pressure loss of the system will be large, the efficiency will be reduced, the oil suction condition of the pump will deteriorate, and cavitation and cavitation will easily occur, making the pump operation difficult. If the viscosity is too small, the system will leak too much, the volume loss will increase, the system efficiency will be low, and the rigidity of the system will become worse. In addition, the temperature of the working medium will change due to seasonal changes, as well as before and after the machine is started and during normal operation. Therefore, for the hydraulic system to work normally and stably, the viscosity of the working medium is required to change less with temperature.

② The working medium with good lubricity lubricates the moving parts in the hydraulic system to reduce friction and ensure that the system can work normally for a long time. In recent years, hydraulic systems and components have developed towards high performance, and many friction parts are in a boundary lubrication state. Therefore, the hydraulic working medium is required to have good lubricity.

③Anti-oxidation: The contact between the working medium and air will cause oxidative deterioration. High temperature, high pressure, and certain substances, such as copper, zinc, aluminum, etc., will accelerate the oxidation process. After oxidation, the acid value of the medium increases and becomes more corrosive. Moreover, the sticky substances generated by oxidation will block the pores and gaps of the components and affect the normal operation of the system. Therefore, the working medium is required to have good oxidation resistance.

④ Good shear stability: The working medium must undergo severe shear when passing through pumps, valves, and microporous components. This mechanical effect will produce two forms of viscosity changes in the medium, namely temporary viscosity loss at high shear rates and permanent viscosity drop caused by the destruction of polymeric tackifier molecules. This situation is particularly serious at high speeds and high pressures. Once the viscosity drops to a certain level, it cannot be used anymore. Therefore, the working medium is required to have good shear stability.

⑤ Anti-rust and non-corrosive metal Many metal parts in the hydraulic system have been in contact with the working medium for a long time, and their surfaces will rust under the action of moisture and air dissolved in the medium, destroying the accuracy and surface quality. Rust particles circulating through the system can also cause accelerated component wear and system failure. At the same time, the medium itself is not allowed to corrode metal parts or slowly decompose to produce corrosive substances such as acids. Therefore, the hydraulic working medium is required to have good properties of protecting metal, preventing rust, and not corroding metal.

⑥ Compatible with the sealing material The working medium must be compatible with the sealing material of the component and not cause swelling, softening, or hardening. Otherwise, the seal will fail, leakage will occur, the system pressure will drop, and the system will not work properly.

⑦ Good defoaming and anti-foaming properties. The air mixed and dissolved in the working medium often precipitates in two forms: bubble diameter greater than 1mm) and mist air (diameter less than 0.8mm), that is, foaming. The foaming medium reduces the pressure of the system, worsens the lubrication conditions, reduces the action rigidity, and causes abnormal noise, vibration, and cavitation in the system. In addition, the surface area of air bubbles and mist air is large, and contact with the medium accelerates oxidation. Therefore, the working medium is required to have good anti-emulsification properties.

⑧Others: Good chemical stability, low temperature start-up and fluidity, flame resistance, and sufficient cleanliness, non-toxic, and odorless.