Selection of special lubricants

Selection of special lubricants

There are many types and grades of lubricating greases, and there are a wide range of applications. Choosing the appropriate lubricating grease should not only understand the physical and chemical properties of the lubricating grease, but also understand the industrial and mining conditions, refueling methods, and life requirements. Considering from many aspects, we can give full play to the performance of the grease and achieve the best use effect.

To properly select grease, the following aspects should be considered:

1. Purpose

1) Friction reduction Mainly consider the use of temperature range, bearing speed, load, etc.

2) Protection Mainly consider the contact medium, such as surface metal, water, chemicals, etc.

3) Sealing First, consider the compatibility of the grease with the sealing material; secondly, it depends on the contacting medium. Vacuum sealing grease should also consider the requirements of vacuum degree.

2. Temperature

 Working temperature is an important basis for selecting grease. Generally speaking, every time the bearing temperature rises by 10-15°C, the life of the grease is reduced by about half. The temperature resistance of grease is not only based on the dropping point, but also the type of base oil. For the temperature requirements of about 160-200℃, greases with complex soap, polyurea and bentonite as thickeners, ester oils, synthetic hydrocarbons and silicone oils as base oils should generally be used. The temperature requirement is 250 ℃, should use urea organic compounds, fluoride as a thickening agent, phenyl silicone oil, perfluoropolyether as the base oil grease.

 For greases required to work at low temperatures, generally lower than -30 ℃, it is necessary to use grease based on synthetic oil, the minimum limit temperature of synthetic oil grease is -80 ℃.

3. Load

  Some large equipment such as ore crushers, ball mills, large motors, etc., have large impact loads on their bearings. Therefore, when selecting grease, the wear resistance and extreme pressure of the grease must be considered. Many people think that it is not very scientific to use MOS2 grease as long as the load is heavy. In fact, we should focus on the anti-wear extreme pressure additives in the grease.

4. Rotating speed

  This is another important index for selecting grease, which is generally judged based on the DN value.

  DN = D (outer diameter mm) x R (speed rpm)

  In some industries, such as textiles, the bearing speed can reach 20,000 rpm, and the DN value can be as high as 1,000,000. Here, general grease is difficult to meet the requirements of the equipment. Only professional high-speed bearing grease can meet the requirements of the equipment.

 

5. Environment and media

  The environment in which the lubricated parts are located and the media in contact have a great influence on the performance of the grease, and must be carefully considered. Generally, it is suitable to use composite aluminum grease with good water resistance in places with humid environment, contact with water, water vapor, and seawater; for contact with acid or acid gas, it is suitable to use composite barium-based grease or urea group with good acid resistance Lubricating grease; For long-term contact with chemical solvents or strong acids, strong bases, and strong oxidants, such as the bottom bearing of the vertical centrifuge of the PTA production line, the liquid oxygen pump of the oxygen plant, etc., perfluoropolyether grease should be used.