Among various vacuum equipment, a pump that obtains a vacuum by continuously changing the volume of the suction chamber in the pump by a mechanical method is often called a mechanical vacuum pump. In mechanical vacuum pumps, vacuum oil not only acts as a medium for obtaining vacuum, but also acts as a lubricating and cooling agent for mechanical friction components. What are the main performances of pump oil in Leybold vacuum pump accessories ?
1, vacuum pump oil tightness
The vacuum pump oil needs a proper viscosity, the low temperature can make the vacuum pump start quickly, the high temperature vacuum pump oil can have good sealing performance, and the pump vacuum pump oil temperature rises low. Does not contain photo-volatile components, reducing the use of vacuum pump oil return rate.
2. Saturated vapor pressure of vacuum pump oil
One of the key indicators of saturated steam pressure is vacuum pump oil. The saturated vapor liquid reaches a dynamic equilibrium in a closed vessel at a constant temperature, pressure of steam pressure.
The saturated vapor pressure oil should be as low as possible, and the operating temperature of the pump still has enough low saturated vapor pressure, which is lower than the ultimate pressure of the vacuum pump. The temperature of 60 degrees Celsius is at least 6.5 x kPa pure (since the temperature rises at 20 degrees Celsius, the saturated vapor pressure is about to drop by an order of magnitude).
3, very low vapor pressure
This is an important performance of vacuum pump oil. Since the vacuum pump requires a vacuum of 1.33×10-4Pa (or 10-6mmHg) and a high requirement of 1.33×10-6Pa (10-8mmHg), the evaporation of the vacuum pump oil is required. Extremely low and requires very little consumption to prevent evaporation. Paraffin-based narrow-cut lubricating oils are generally used. For diffusion vacuum pumps, silicone oils or other synthetic oils having a very low vapor pressure can also be used.
4, vacuum pump oil lubricity
Friction and wear, surface fatigue and corrosion wear, etc., related lubrication conditions. The good performance of vacuum pump oil is beneficial to inhibit corrosion and wear. It can effectively reduce surface adhesive wear and fatigue wear; the cleaning effect of liquid lubricant friction surface can also reduce friction and wear. Save energy, reduce frictional resistance, reduce wear and extend the life of the machine.
5, the cooling performance of vacuum pump oil
Reducing the temperature of the friction surface is an important lubrication. Friction surface motion must overcome friction and work, and power consumption overcomes the frictional heat of all work, with the result that the friction surface temperature rises. The magnitude of the frictional heat is the state of lubrication, the large high viscosity, the lower viscosity, and the lower the thermal boundary between the two. It can be seen that the vacuum pump oil of appropriate viscosity can not only achieve liquid lubrication, but also reduce the generation of friction heat, but it can also rub the heat pump outside the body in time.
6. Oxidation stability of vacuum pump oil
Oxidative stability indicates the anti-aging properties of lubricating oils, and this special performance requirement for vacuum pump oil industrial line operations. All lubricants are based on their chemical composition and different external environmental conditions, and have a tendency to auto-oxidize to varying degrees. The presence of air (or oxygen) and metal catalyst in the vacuum pump oil, oxidation time at a certain temperature, there will be oil acid value, viscosity change and precipitation conditions. The process of oxidation is used to gradually form some aldehydes, ketones, acids and resins, asphaltenes and other substances, and oxidative stability is a material which inhibits the above-mentioned properties which are disadvantageous to the use of the product.
7. Thermal stability of vacuum pump oil
The expressed high temperature resistant oil, that is, is resistant to pyrolysis of petroleum, that is, thermal decomposition temperature. A severe vacuum environment is proposed for thermal stability requirements.
Natural mineral oil has its inevitable defects, heat resistance is better than synthetic oil, the composition of the pump oil and thermal oxidative decomposition are easily deteriorated, extreme pressure stability is poor, and the pumping speed also reduces the use time. Generally, the pure mineral oil oxidation test method D943 is about a hundred hours, and the synthetic oil D943 can be extended to more than 3000 hours. It can be seen that its service life is extended.
8. Good corrosion resistance and demulsibility
If the vacuum pump in the Leybold vacuum pump fittings is inhaled, it will chemically change with the oil and corrode the metal parts inside the pump. In addition, the inhaled air often contains water vapor condensed water, causing emulsification of the vacuum pump oil and corrosion of the metal, so it is required to have good corrosion resistance and emulsification resistance (water separation performance). The emulsification of the vacuum pump oil used in the vacuum dehydration process is more prominent.
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