Select the type of hydraulic oil according to the working environment and working conditions. When selecting the hydraulic oil used in hydraulic equipment, you should comprehensively consider and judge from several aspects such as working pressure, temperature, working environment, hydraulic system and component structure and material, and economy. . Environmental factors include: above ground, underground, indoor, outdoor, coastal, cold area, high temperature, open flame. Operating conditions: pump type, pressure, temperature, material, sealing material, running time. Oil properties: physical and chemical properties. Economy: use time, oil change period, price.

work pressure

Mainly put forward requirements on the lubricity of hydraulic oil, that is, anti-wear property. The hydraulic components of the high-pressure system, especially the friction pair in the boundary lubrication state in the hydraulic pump, due to the increase of positive pressure and high speed, the friction and wear conditions are relatively harsh, so it is necessary to choose HM oil with excellent lubricity, that is, anti-wear performance and extreme pressure performance. . Select hydraulic oil according to the working pressure of the hydraulic system and oil pump. For pressure <8MPa, use L-HH, L-HL (for vane pump, use L-HM), for pressure 8-16MPa, use L-HL, L-HM, L-HV, for pressure >16MPa use L-HM, L-HV hydraulic oil. The working pressure of the hydraulic system is generally marked by the rated or maximum pressure of the main oil pump.

Operating temperature

It refers to the temperature of the hydraulic oil in the hydraulic system when it is working. It mainly puts forward requirements on the viscosity temperature and thermal stability of the hydraulic oil. For the working temperature of -10-90°C, use L-HH, L-HL, L-HM hydraulic oil, Use L-HV and L-HS for temperatures lower than -10°C, and high-quality L-HM, L-HV, and L-HS for working temperatures >90°C. The general relationship between the ambient temperature and the operating temperature is: the hydraulic equipment is in the workshop, and the normal working temperature is 15-25°C higher than the ambient temperature; the hydraulic equipment is outside the temperate zone, and the temperature is 25-38°C; under the tropical outdoor sunshine, the temperature is 40-50°C higher .

type selection

① According to the form and material of the friction pair

According to the form of the friction pair and its material. The vane of the vane pump and the stator surface are in contact with the oil and are easily worn during movement. The steel-steel friction pair material is suitable for L-HM anti-wear with ZDDP (zinc dialkyldithiophosphate) as the anti-wear agent. Hydraulic oil; the friction form and movement form of the cylinder, oil distribution plate, and piston of the plunger pump are also suitable for using HM anti-wear hydraulic oil, but there are bronze parts in the plunger pump, which will cause corrosion and wear due to the action of this material part and ZDDP Therefore, the plunger pump with bronze parts cannot use HM anti-wear hydraulic oil with ZDDP as additive. At the same time, the selection of hydraulic oil should also consider its compatibility with the sealing material in the hydraulic system.

Generally, vane pumps can use zinc-containing anti-wear hydraulic oil, and plunger pumps should use ashless oil. For hydraulic systems where the pressure of the vane pump is higher than 15MPa, the pressure of the plunger pump is higher than 30MPa, and two types of pumps exist at the same time, the oil that meets the Denison HF-0 specification should be selected.

②Gear pumps, vane pumps and plunger pumps are the main types of pumps in hydraulic systems.

The order of the lubricity of hydraulic oil on the anti-friction effect of the three major pumps is vane pump>piston pump>gear pump. Therefore, it is better to use HM oil regardless of the pressure of the hydraulic system where the vane pump is the main oil pump. The higher the accuracy of the hydraulic system, the higher the cleanliness of the selected hydraulic oil is required. For example, the closed-loop hydraulic system with electro-hydraulic servo valve requires the hydraulic oil of CNC machine tools. These two oils can be used with high-grade HM and HV hydraulic oil respectively. replace. The test shows that the three types of pumps require the order of hydraulic oil cleanliness to be that the plunger pump is higher than the gear pump and the vane pump, and the order of the extreme pressure performance is that the gear pump is higher than the plunger pump and the vane pump.