 Good morning to one and all. With our today's session, we are going to learn about Lubricant. In that, we will learn about selection of Lubricant. So, at the end of this session, student will be able to explain the selection of Lubricant for different processes. Introduction, Lubricant. Any substance which is introduced between two moving or sliding surfaces with a view to reduce the frictional resistance between them is known as a Lubricant. This type of chemical we are using as a Lubricant and this is being used in our day to day practices for several purposes. In industry also, we are using this and as well as for automotive sections, we need this Lubricant. So, what are the functions of this Lubricant? Surface deformation. It reduces the surface deformation by wear and tear because the direct contact between the rubbing surfaces is avoided. Second, energy loss. It reduces the loss of energy in the form of heat. In other words, it acts as a coolant also, efficiency. It reduces the wastage of energy so that efficiency of the machine is enhanced. Next, expansion of metal. It reduces the expansion of metal by local fractional heat. It avoids the size of moving surfaces since the use of Lubricant minimizes liberation of fractional heat, avoids or reduces unsmooth relative motion of the moving or sliding parts. It reduces the maintenance and running cost of the machine. It also sometimes acts as a seal. For example, Lubricant used between piston and the cylinder wall of the internal combustion engine acts as a seal thereby preventing the leakage of gases under high pressure from the cylinder. So, we will now go for the selection of Lubricant for a different operations. So, the first operation is internal combustion system. So, what are the conditions for this internal combustion engine? That is it shows high temperature. It shows low to high speed and it is concerning with low to high pressure also. So, how to select the Lubricant for this type of operation? The Lubricant which is having high thermal stability we can select for this. Lubricant should be non-corrosive in action for this type of operation. It should have high viscosity index, good oiliness and it should act as a seal between piston rings and the cylinder wall against high pressure combustion gases. Also, it should be stable towards oxidation because temperature is high, air is available, oxygen is available and it should not undergo any oxidation process. Otherwise, our aim of selection of such a material for smooth operation will be collapsed. Next one, moderate viscosity. It should show a moderate viscosity also. Example, petroleum oil blended with above property improvers can be selected as a lubricant for ice engines. Second operation is refrigeration. We know that in case of refrigeration the temperature is reduced. So, the conditions which are related with this particular operation that is refrigeration are it has low temperature and it shows moderate load also. So, the lubricants with certain properties we can select for such a type of operations that is for refrigeration. So, lubricant should have low pore point that is below 40 degree Fahrenheit. It should show moderate viscosity and it should have low cloud point also. So, the example for this type of operation that is lubricant is naphthenic base oil can be selected as a lubricant for refrigeration type of systems. Third operation that is gears. So, gears, conditions which are related with this gear operations are the pressure is very high. Again, it shows high temperature and low to high speed. So, intermittent speed is concerning with this particular operation and that is why the selection of lubricant for this particular operation is very essential. The lubricant which bears the properties which are given below can be selected for this type of operation. So, the lubricant should have high oiliness that means it should stick up to the walls under very high pressure. Second it should show proper viscosity that is medium to high viscosity is expected. Third it should show resistance towards oxidation next one it should have high viscosity index that means there should not be any change in viscosity with respect to change in temperature during this particular operation and it should show good anti foam property also. There should not be any dissolution effect on rubber seals that is example proper viscosity petroleum oils can be selected that is which are blended with anti foam, antioxidant, viscosity index and oiliness improvers or graces can be selected even for this type of operation. Next operation that is cutting and drilling operation. So, the conditions which are related with this particular operation are very high pressure and temperature is also high. So, lubricants bearing certain properties can be selected for this particular operation and these properties are like it should show low viscosity, it should have high oiliness property, it should be anti corrosive in nature, it should act as a coolant also extreme pressure additives in it are expected. So, cutting oils like emulsion of vegetable oil in water medium with emulsifier mixed with antioxidants extreme pressure additives etcetera can be selected for this type of operation. So, at this moment pause the video and answer this question. Question is lubricant selected for cutting tool should options A have low viscosity, B have high oiliness, C be coolant and D all the above welcome back. So, the answer for it should have all the above properties that is D is the answer for this particular question. Fifth operation that is transformers. So, in case of the transformers conditions which are related with this are insulation for heat transfer and higher temperature on load condition. Therefore, the properties which we expect from the lubricant are that is it should show low viscosity, it should have high dielectric property, it should show high oxidation resistance also and it should be stable chemically. Example, highly refined petroleum oil without any trace of dirt and moisture can be selected for transformers. Next operation is delicate instruments. The conditions which are related with this particular operation are low load and second high speed. So, the properties of lubricant the lubricant should have low to moderate viscosity, it should be non-volatile in nature and third one it should show low pore point also. So, the examples for this type of lubricant it is vegetable oils, animal oils or low viscosity petroleum oils can be selected for this particular operation. References for this lecture I have referred a textbook of engineering chemistry by Jane and Jane. Thank you.