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In the vacuum pump accessoriesVacuum pump oilSelected 10 requirements:

Requirement 1: Tightness

The pump oil in the vacuum pump accessories should have a suitable viscosity, which can make the vacuum pump start quickly at low temperature, and the pump oil can have good sealing performance at high temperature, and the pump oil has a low temperature rise. Does not contain light volatile components, reduce the use of the process of vacuum pump oil return rate.

Requirement two: saturated vapor pressure

Saturated vapor pressure is one of the key indicators of pump oil. In a closed container at constant temperature, the pressure when the vapor and liquid phases reach dynamic equilibrium is called saturated vapor pressure.

The saturated vapor pressure of the oil should be as low as possible. At the maximum operating temperature of the pump, it is still necessary to have a sufficiently low saturation vapor pressure, and to be lower than the limit pressure of the vacuum pump rules. At least 6.5 × 10-5 kPa should be reached at 60 ℃ (the saturated vapor pressure will drop by about one order of magnitude for every 20 ℃ rise in temperature rise).

Requirement three: limit full pressure and limit pressure

Ultimate full pressure: The sum of the pressure generated by all substances (gases) in the vacuum pump is measured by a Pirani gauge or a thermocouple vacuum gauge. At present, foreign countries pay attention to the test index of full pressure.

Ultimate partial pressure: The ultimate partial pressure of the pump measured by a mercury compression vacuum gauge (McGill), and the partial pressure of the two-stage rotary vane pump shall be ≤ 6 × 10-5kPa. Limit full pressure and limit pressure difference request is not greater than an order of magnitude. The greater the difference between the two, the more volatile components contained in the pump oil, the worse the nature of the oil.

Requirement four: vacuum pump accessories in the smoothness of the vacuum pump oil

Friction surface friction wear, appearance tired wear and corrosion wear, etc., are related to smooth conditions. Good performance of the pump oil is conducive to the suppression of corrosion and wear; can effectively reduce the adhesive wear and appearance of tired wear; fluid smooth agent on the friction surface cleaning effect, but also can reduce friction and wear. Reduce friction resistance to save energy and reduce wear to extend mechanical life.

Requirement 5: cooling performance

Reducing the temperature of the friction surface is an important function of smoothness. When the friction surface movement must restrain the friction force and work, the work spent on the restraint friction force is all converted into heat, the result will cause the friction surface temperature rise. The magnitude of friction heat is related to the smooth state, the heat of high viscosity is the largest, the heat of low viscosity is the smallest, and the heat of border friction is between the two. It can be seen that the pump oil with suitable viscosity can not only complete the smooth liquid and reduce the generation of frictional heat, but also bring the frictional heat out of the pump body in time.

Requirement six: cleanliness

Friction to prevent contact with the surrounding media, causing corrosion, rust and damage. The vacuum pump oil with excellent performance cleans the scale of the friction area as much as possible.

Requirement seven: oxidation stability of pump oil

The oxidation stability clarifies the anti-aging performance of smooth oil, and this special performance request is made for vacuum pump oil in industrial assembly line operation. All smooth oils have different levels of auto-oxidation tendency depending on their chemical composition and external conditions. Pump oil in the presence of air (or oxygen) and metal catalyst, at a certain temperature oxidation time, will show the oil acid value, viscosity changes and the formation of sediment. Oxidation will occur with the application process, so some aldehydes, ketones, acids, colloids, asphaltenes and other substances will be gradually generated. Oxidation stability is the performance of suppressing the above-mentioned substances that are not conducive to the application of oil products.

Requirement eight: heat stability

It indicates the high temperature resistance of oil, that is, the resistance of smooth oil to thermal synthesis, that is, the thermal synthesis temperature. Some harsh vacuum application environment will put forward the request of thermal stability of vacuum oil.

Natural mineral oil has its unavoidable defects, heat resistance is worse than synthetic oil, composition is easy to deteriorate with thermal oxidation synthesis, limit pressure stability is poor, pumping speed also decreases with the use of time. Ordinary pure mineral oil oxidation test method D943 is about several hundred hours, while synthetic oil D943 can be extended to more than 3000 hours. It can be seen that its service life is extended.

Requirement nine: anti-emulsification

During the operation of the vacuum pump, the moisture and cold air in the system are discharged into the pump oil. If the anti-emulsification property is not good, it will form an emulsion with the mixed water, so that the water is not easy to be released from the bottom of the circulating oil tank, which may form Vacuum degree drop and smooth bad.

Therefore, anti-emulsification is a very important physical and chemical property of industrial smooth oil. Especially in medicine, food, ceramics and other industrial use of vacuum drying process, anti emulsification performance is more important. Good anti-emulsification of pump oil and water separation can be strong, water vapor and condensed gas through the opening of the gas ballast valve, will discharge local water vapor. In addition, low viscosity anti emulsification can be better than high viscosity vacuum pump oil.

Requirement ten: anti-foam

During the operation of the vacuum pump, due to the presence of air, foam is often produced, especially when the oil contains additives with external activity, it is easier to produce foam, and the foam is not easy to disappear. Smooth oil in the use of foam will cause the destruction of the oil film, not only the friction surface of the attack or increase the wear and tear, and promote the oxidation of smooth oil. The gas in the vacuum system in operation is discharged from the sealed pump oil layer from time to time. The discharged gas layer produces a large number of bubbles on the outer surface of the oil layer and overflows from the exhaust hole of the pump, resulting in oil loss and equipment pollution. The vacuum pump oil with anti-foaming agent has obvious progress in anti-foaming effect.