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Lubricant additives

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Introduction to lubricant additives in short

Veröffentlicht in: Ingenieurwesen

Lubricant additives

  1. 1. Submitted By Submitted To Shivanshu Trivedi Dr. R. K. Mondloi Scholar No. 162116219 Coordinator M. Tech. I Sem. Maintenance Engg. Maintenance Engg.
  2. 2. Introduction  Lubricants are not just oils they contains chemical compounds as well.  Lubricants comprises of base oil and additives.
  3. 3.  Additives are chemical compounds that improve the lubricant performance of base oil (or oil “base stock")  Additives are organic or inorganic compounds dissolved or suspended as solids in oil.  Additives typically range between 0.1 to 30 percent of the oil volume, depending on the application of lubricant.  The additives are used to enhance the performance characteristics of the lubicating oil.  Additives suppresses undesirable properties and impart new required properties in base oil
  4. 4. Why we need additives in lubricants?  In Gears at very high contact stresses lubricant will be squeezed out, metal to metal contact occur so to avoid failure and seizure of parts we require extreme pressure additives.  In IC Engines there is a very high working temperature, at this temp. lubricant may oxidize that effects in reducing efficiency and damaging engine so to avoid oxidation additives are used.  Refrigerating systems operate at very low temp lubricating oil required a flow ability to get circulated from one place to other place so that it can carry wear debby particle, requiring low temperature lubricant, need to add additives to impart low temperature properties .  From above examples it is clear that additives are needed in lubricating oils as they improve the characteristics of base stock as required.
  5. 5. Role of Additives Additives have three basic roles:  1) Enhance existing base oil properties with antioxidants, corrosion inhibitors, anti-foam agents and demulsifying agents.  2) Suppress undesirable base oil properties with pour-point depressants and viscosity index (VI) improvers.  3) Impart new properties to base oils with extreme pressure (EP) additives, detergents, metal deactivators and tackiness agents.
  6. 6. Types of lubricant additives  Performance Enhancing Additives - Improves overall properties of lubricants  Viscosity Index improvers  Anti foaming additives  Detergent or Dispersant additive  Pour point depressant  Acid neutralizer additives  Surface protecting additives – protects the interacting surfaces in metal to metal contact from chemically active lubricants.  Extreme pressure additives  Anti rust additives  Antiwear additives  Lubricant protecting additives – protects the lubricity of base oil  Anti oxidant additives  Emulsifier additives
  7. 7.  Detergent additives, dating back to the early 1930s, are used to clean and neutralize oil impurities which would normally cause deposits (oil sludge) on vital engine parts. Typical detergents are magnesium sulfonates.  Corrosion or rust inhibiting additives retard the oxidation of metal inside an engine.  Antioxidant additives retard the degradation of the stock oil by oxidation. Typical additives are organic amines and phenols.  Metal deactivators create a film on metal surfaces to prevent the metal from causing the oil to be oxidized.  Pour point depressants improve the oil's ability to flow at lower temperatures
  8. 8.  Viscosity modifiers make an oil's viscosity higher at elevated temperatures, improving its viscosity index (VI). This combats the tendency of the oil to become thin at high temperature. The advantage of using less viscous oil with a VI improver is that it will have improved low temperature fluidity as well as being viscous enough to lubricate at operating temperature. Viscosity modifiers are often plastic polymers.  Friction reducers, like molybdenum disulfide, are used for increasing fuel economy by reducing friction between moving parts. Friction modifiers alter the lubricity of the base oil. Whale oil was used historically.  Extreme pressure agents bond to metal surfaces, keeping them from touching even at high pressure.  Antiwear additives or wear inhibiting additives cause a film to surround metal parts, helping to keep them separated. Zinc dialkyldithiophosphate or zinc dithiophosphates are typically used.
  9. 9.  Dispersants keep contaminants (e.g. soot) suspended in the oil to prevent them from coagulating.  Anti-foam agents (defoamants) inhibit the production of air bubbles and foam in the oil which can cause a loss of lubrication, pitting, and corrosion where entrained air and combustion gases contact metal surfaces.  Antimisting agents prevent the atomization of the oil. Typical antimisting agents are silicones.  Wax crystal modifiers are dewaxing aids that improve the ability of oil filters to separate wax from oil. This type of additive has applications in the refining and transport of oil, but not for lubricant formulation.  Rust inhibitor prevent rust formation by forming a protective surface film
  10. 10. Usage of common additives
  11. 11. How Additives Work  Additives are polar molecules or elements.  Additive polarity is defined as the natural directional attraction of additive molecules to other polar materials in contact with oil.  It’s important to note that additives are also sacrificial. Once they are gone, they’re gone.  Additives are attracted to, such as dirt, silica and water, the additives will cling to the contaminants and settle to the bottom or will be filtered out.  There are a three polar mechanisms such as particle enveloping, water emulsifying and metal wetting occurs generally in additives.
  12. 12.  Particle enveloping means that the additive will cling to the particle surface and envelop it. These additives are metal deactivators, detergents and dispersants. They are used to peptize (disperse) soot particles for the purpose of preventing agglomeration, settling and deposits, especially at low to moderate temperatures.  Water emulsifying occurs when the additive polar head clings to a micro-droplet of moisture. These types of additives are emulsifying agents.  Metal wetting is when additives anchor to metal surfaces, which is what they are supposed to do. They attach to the interior of the gear casing, gear teeth, bearings, shafts, etc. Additives that perform this function are rust inhibitors, anti-wear (AW) and EP additives, oiliness agents and corrosion inhibitors.
  13. 13. Too much of a good thing  When using oil additives, more is not always better. As more additive is blended into the oil, sometimes there isn’t any more benefit gained, and at times the performance actually deteriorates. In other cases, the performance of the additive doesn’t improve, but the duration of service does improve.  In addition, increasing the percentage of a certain additive may improve one property of an oil while at the same time degrade another. When the specified concentrations of additives become unbalanced, overall oil quality can also be affected.  Some additives compete with each other for the same space on a metal surface. If a high concentration of an anti-wear agent is added to the oil, the corrosion inhibitor may become less effective. The result may be an increase in corrosion- related problems.
  14. 14. Trends in Lubricant Additives  Need for enhanced lubricant performance is overreaching mega trend in automotive, marine, aviation, and industrial segments. Base oils are complemented with additive packages to enhance lubrication and reduce toxic emissions.  Reducing consumption of expensive and non renewable petroleum based lubricants.  Industries and Governments are in a continual search for high performance lubricants that does not affect environment and reduce carbon footprint.
  15. 15. References  www.Wikipedia.org  NPTEL Videos  Hand book of Maintenance Engg. By McGraw Hill  www.machinerylubrication.com  www.elf.com  Chevron Oronite's oil Additives
  16. 16. Thank You