Councils for lubricant of rolling bearings
Basic purpose of lubricant for rolling bearings is:
- to reduce the sliding friction between swing bodies (balls, rollers) and the separator and also between boards of rings and end faces of rollers;
- to reduce the sliding friction between the surfaces of swing arising owing to elastic contact deformations under the influence of loading during the operation of the bearing;
- to protect high-quality finishing of the surface of bodies of swing and effective areas of rings from corrosion;
- to promote the best consolidation of the body for the purpose of protection from penetration of strangers abrasive and pollutants;
- to assist uniform distribution of heat in all parts of the bearing and withdrawal from it of heat developing as a result of friction work.
Quality of the lubricants applied to rolling bearings
The lubricant applied to ball and roller bearings has to meet the following main requirements:
- to have stability both chemical, and physical;
- not to contain mechanical impurity and water above the norms established by technical standards (GOST or TU);
- not to cause corrosion and to protect from it therefore lubricant should not contain free acids or other rusting substances.
- jellied lubricant has to have the good plastic properties allowing to resist action of the centrifugal forces aiming to throw out lubricant from the bearing at its rotation. Lubricant should not be stratified on constituents and emit soap which, hardening, can lead the bearing to premature failure or to accident. Ointment during the operating time has to keep initial consistence, plasticity and not fibrous structure;
- liquid mineral oils in the course of work should not change the viscosity sharply. It is desirable that change of viscosity in connection with change of temperature was not sharp. Oils have to be well cleaned, have good lubricant properties and have the smallest internal friction.
The choice of lubricant for rolling bearings
For lubricant of rolling bearings, depending on working conditions and the design of the bearing node, liquid oils or jellied lubricant can be applied.
Liquid lubricant - oils are the best lubricant for rolling bearings, but its application often demands some complication of the design of the bearing node for achievement of bigger tightness of the body.
At the choice of brand of oil it is necessary to consider loading, speed and working temperature in the bearing. The heavy load and is higher than temperature, the oil has to have bigger viscosity. At small loadings, low temperatures and high speeds apply low-viscous oil.
Oils of the animal and phytogenesis in pure form for lubricant of rolling bearings are not recommended as they contain the large amount of organic acids which can cause corrosion of the bearing. Besides, oils of this type in the course of work can change the chemical and physical properties, especially at the increased temperature and hashing that takes place during the bearing operating time.
The systems of supply of oil to the bearing
Oil in rolling bearings can move:
- from drop lubricators which are established usually on horizontally located shaft when the certain supply of oil to the bearing is required (several drops in the minute);
- by means of wick lubricators when bearings are installed on vertical shaft;
- oil bathroom by immersion of bodies of swing in oil or oil spraying by other parts submerged in one general with bearings the oil bathtub.
When greasing the bearing by its immersion in the oil bathtub at speed to 3000 in the minute it is necessary that the level of oil was not above the center of the lower ball or the roller, and at speed more than 3000 in the minute oil have to concern the lower ball or the roller only.
It is especially carefully necessary to approach the choice and supply of oil to high-speed bearings which demand constant supply of oil in small amounts in cases of low working temperatures (70 - 80 °C) and, on the contrary, in the increased quantities (up to 3 liters a minute) when it is required to take away heat from excessively heating up bearing. In the latter case it is the best of all to make oil supply by spraying under pressure or in the form of oil fog by its mixing in the certain proportion with the dry air under pressure.
As oils are liquids, for prevention of their leak from the body the corresponding consolidations have to be provided, and special attention has to be paid to this question. In those cases when under the terms of work and the design of the bearing node felt or felt consolidations can be applied, it is necessary that material before cutting of rings was purified from dust, dirt and other abrasive substances, and the edges of felt rings were exactly cut. Before installation of rings in body grooves they have to be dehydrated and impregnated with mineral oil, for this purpose submerge them in the oil bathtub with the temperature of 105 - 110 °C at 25 - 30 minutes. Oil for impregnation of rings undertakes the same, as for lubricant of bearings during their operation.
Recently consolidations from oilproof rubber began to be applied widely (sevanit) which very well protect the body of the bearing both from outflow of lubricant, and from penetration into it of different foreign particles, dust and dirt.
Jellied lubricant is the plastic colloid systems which are keeping the form set by it at the normal temperature (20 - 30 °C) and easily changing it under the influence of small external influence. They form the plastic lock between shaft and the body of the bearing and prevent penetration of abrasive and other pollution to effective areas of the bearing that is extremely important in case of high impurity of the environment.
On the structure jellied lubricant represents the difficult educations consisting generally of mineral oil and thickener.
Jellied lubricant which part are as thickener of soap of salt of natural or synthetic fatty acids have the broadest application.
Jellied lubricant is produced on calcic, calcium-sodium, sodium, aluminum, lithium, lead and other soaps.
Depending on the basis of the soap which is the part of lubricant the last have specific properties.
Calcic jellied lubricant (solid oil fatty L, M and T - GOST 1033 - 41) has melting temperature which is not exceeding 90 °C. Practically they are insoluble in water owing to what they are moisture resistant and can be applied in the conditions of high humidity when the working temperature of the bearing does not exceed 55 - 60 °C. Calcic lubricant which structure as the obligatory building block includes water not can is long to work in the bearing at the temperature of 55 - 60 °C, and is especially higher than this temperature. At such temperature there is the evaporation from lubricant of strukturnosvyazny water. Lubricant at the same time breaks up, the liquid part follows through body gaps, and soap is condensed, sometimes up to the firm black weight.
Sodium lubricant - консталин UT-I (GOST 1957 - 53), консталин SK-UTS-I (GOST 5703 - 51), KB lubricant - UTM (GOST 2931 - 55) is made, as a rule, on the purified mineral oils and natrovy soaps. This lubricant is very sensitive to moisture as they form when mixing with water the emulsion like oil-water and is washed away from effective areas of the bearing. Therefore sodium lubricant has to be applied during the operation of the bearing in the conditions of the dehydrated external environment.
Sodium lubricant more high-melting in comparison with calcic lubricant. Their melting temperature is different, depending on the lubricant grade, and reaches 175 °C.
Sodium lubricant has good stability. When cooling after melting they stiffen in ointment again, without losing the lubricant properties.
Lubricant No. 1-13 UTV (GOST 1631 - 52), SP 1 belongs to the combined calcium-sodium lubricant (GOST 3257 - 53). As lubricant of this look contains calcic soaps, they are less sensitive to moisture in comparison with purely sodium lubricant in this connection they can be applied widely in the conditions of the increased humidity.
Oil industry the number of lubricant of the special purpose is produced.
Tsiatim 201 - UTVM - I (TU 326 - 50) is applied to greasing of bearings of the small overall dimensions working with the broad range of positive and negative temperatures and also to bearings of the closed type with two sealing washers. In these bearings lubricant is put at assembly at the bearing plants and not replaced in use. It is not allowed to wash out bearings of the closed type before installation them on the workplace in gasoline or kerosene.
At use of jellied lubricant simplicity of consolidations, considerable term of operation of the bearing without lubricant replacement, effective isolation of the bearing from influence of the external environment, etc. is reached.
Jellied lubricant is not recommended to be applied when special requirements to the minimum bearing friction are imposed during operation.
Extent of filling of the body with jellied lubricant is defined practically in each case.
Giving of excessive amount of lubricant to the bearing always causes temperature increase of the node therefore if at observance of giving to the bearing of the set amount of lubricant and at full confidence in its quality nevertheless during the work of the node sharp increase in its temperature is observed, it is not necessary to enter additional amount of lubricant into the body, and it is necessary to find and remove the cause causing temperature increase of the node.
In the cut-in of the new bearing always perhaps some temperature increase which, however, under normal conditions works in several hours has to decrease and remain stable at further operation.Top