What viscosity of oil should be used for all kinds of vacuum pumps

- May 23, 2019-

What viscosity of oil should be used for all kinds of vacuum pumps

 

The vacuum technology to achieve rapid development of our country in recent decades, has become an independent science, the basis of the vigorous development of many industries such as aerospace science, vacuum coating, vacuum smelting, high energy physics, controlled thermonuclear reactions, such as surface research cutting-edge science and the progress of the vacuum technology has a direct and even interdependent relationship.Vacuum oil as various types of machinery vacuum pump special lubricating oil, in the vacuum pump bearing lubrication, sealing, cooling and other functions. Although there are different types of mechanical vacuum pumps, the oil must have suitable viscosity, good oil-water separation, excellent thermal and oxidation stability, as low as possible saturated vapor pressure, because the quality of the oil directly affects the vacuum equipment may reach the limit pressure, pumping rate, back pressure and oil return rate. In recent years, with the development of vacuum technology, mechanical vacuum pump to high speed, low noise, miniaturization development. The linear velocity on the surface of the friction pair inside the pump chamber increases, and the oil temperature rises, so the oil of the mechanical vacuum pump tends to be of low viscosity, and it is required to maintain low vapor pressure under the operating temperature of the pump. According to the working state of oil in use, vacuum oil can be divided into mechanical vacuum oil, steam jet pump oil, lubricating oil for vacuum machinery and vacuum sealing oil.

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Vacuum pump oil viscosity is one of the important factors to play the vacuum pump performance, liquid viscosity is liquid flow resistance, or the internal friction of the liquid, so the greater the viscosity, the greater the resistance by various moving parts; But the viscosity is too small, the pump sealing performance is poor, causing gas leakage, vacuum worse. Therefore, all kinds of vacuum pump on the choice of oil viscosity is very important.

 

1. Oil viscosity selection principle
(1) the higher the speed of the pump, the greater the linear speed of the pump rotor, the lower the viscosity of the selected oil;
(2) the more precise the machining precision of the pump parts or the smaller the clearance between the friction parts, the lower the viscosity of the selected oil products;
(3) when the vacuum pump is used at high temperature, the viscosity of the oil should be greatly selected;
(4) for the vacuum pump with cooling water circulation, generally choose oil with lower viscosity;
(5) winter and summer vacuum pump oil, should be a viscosity grade.

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2. Choice of viscosity range of various vacuum pumps
According to the above principles, the selection of vacuum pump oil viscosity range is recommended as follows:

(1) piston vacuum pump (W type) generally choose HVI100 and HVI150 neutral oil.
(2) rotary vane vacuum pump (type 2X) selects V68, V100 viscosity grade oil.
(3) direct (high speed) rotary vane vacuum pump (2XZ type) choose V46, V68 viscosity grade oil.
(4) slide valve vacuum pump (type H) adopts V68, V100 viscosity grade oil.
(5) trochoid vacuum pump (YZ, YZR type) selects V100, V150 viscosity grade oil.
(6) roots vacuum pump (mechanical booster pump) gear transmission system lubrication, can choose V32, V46 viscosity grade vacuum pump oil.
(7) for other types of vacuum pumps, corresponding oil products can be selected according to their rotational speed, processing accuracy, limit vacuum, etc.

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In addition, must go to the regular manufacturers of oil products, because some manufacturers in the production of vacuum pump oil, not through distillation cutting, direct use of basic oil, add ordinary antioxidant, as a product sales, its harm is:
(1) although the product can also be used as a vacuum pump oil to a certain extent, it will greatly extend the vacuum pumping time in the use process;
(2) common antioxidants are easily oxidized and decomposed at high temperature, resulting in acidic substances, peculiar smell and environmental pollution. At the same time, oil products are also easily oxidized and deteriorated, and the service cycle is shortened;
(3) the ultimate pressure and saturated vapor pressure can not reach the quality standard, affecting the ultimate vacuum degree of the vacuum pump.

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Mechanical vacuum pump oil is the product of deep refining, vacuum degassing or molecular distillation, and does not contain light components. The following items must be paid attention to in use:

(1) storage of oil products. Oil containers must be clean and must not be exposed to the sun or stored in the open air. Keep them in a dark, dry and cool place.
(2) when taking oil or filling oil, the dust around the barrel cover must be removed to prevent sundries from mixing into the oil and causing pump friction.
(3) different brands, varieties and old and new vacuum pump oil can not be mixed.
(4) vacuum pump oil should be strictly avoided to mix with other petroleum products, especially light oil products, otherwise it will affect the vacuum performance of the pu

(5) vacuum pump to avoid the extraction of solvents, water vapor and corrosive gases, etc., when it is necessary to remove this kind of gas, it is necessary to take necessary remedial measures, but also to check, frequently changing oil, especially when oil emulsification or dilution to affect the sealing performance of the pump, must exchange for new oil.

(6) when changing the oil, the old oil must be drained clean, and the new oil must be poured into the pump from the suction port, and the pump shaft should be slowly rotated by hand to clean the pump chamber and exhaust the residual oil. The pump chamber should be cleaned several times, and then the residual oil in the pump shell should be cleaned and put into the new oil.

(7) pump overhaul must be used in solvent or cleaning agent to clean all parts of the pump, and the parts drying.During assembly, the components must be impregnated with new vacuum pump oil before they can be combined. After the assembly, rinse them again with the new oil and then load the new oil.

(8) the refueling appliances must be special equipment and must not be containers containing other oil products or solvents.

(9) for the vacuum pump in a highly corrosive atmosphere or high cleanliness requirements, according to the equipment requirements can choose fluoropolyether oil.