B-6 (Part) 9-10 & 23-24,
BSCIC Industrial Estate, Block-A,
Post Office: Custom Academy Sagarika Road,
Chittagong -4219, Bangladesh.
A lubricant is a substance introduced to reduce friction between surfaces in mutual contact,
which ultimately reduces the heat generated when the surfaces move. It may also have the
function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces.
The property of reducing friction is known as lubricity.
A good lubricant generally possesses the following characteristics:
• high boiling point and low freezing point (in order to stay liquid within a wide range of
• high viscosity index
• thermal stability
• hydraulic stability
• corrosion prevention
• high resistance to oxidation.
Lubricants perform the following key functions:
• Reduce friction
• Transfer heat
• Carry away contaminants & debris
• Transmit power
• Protect against wear
• Prevent corrosion
• Seal for gases
• Stop the risk of smoke and fire of objects
• Prevent rust.
1. Gaseous lubricants. For ex. N2 , H2
2. Liquid lubricants. For ex. vegetable oil , mustard oil
3. Semi-solid lubricants. For ex. grease
4. Solid lubricants. For ex. Polytetrafluoroethylene. MOS2
Corrosion inhibitors, Rust inhibitors
Viscosity index improvers
Stickiness improver, provide adhesive property towards tool surface (in metalworking)
Complexing agent (in case of greases)
The Manufacturing Process
Lube oil is extracted from crude oil, which undergoes a preliminary purification process (sedimentation) before it is pumped into fractionating towers. A typical high-efficiency fractionating tower, 25 to 35 feet (7.6 to 10.6 meters) in diameter and up to 400 feet (122 meters) tall, is constructed of high grade steels to resist the corrosive compounds present in crude oils; inside, it is fitted with an ascending series of condensate collecting trays. Within a tower, the thousands of hydrocarbons in crude oil are separated from each other by a process called fractional distillation. As the vapors rise up through the tower, the various fractions cool, condense, and return to liquid form at different rates determined by their respective boiling
points (the lower the boiling point of the fraction, the higher it rises before condensing). Natural gas reaches its boiling point first, followed by gasoline, kerosene, fuel oil, lubricants, and tars.
• 1 The crude oil is transported from the oil well to the refinery by pipeline or tanker ship. At the refinery,
the oil undergoes sedimentation to remove any water and solid contaminants, such as sand and rock, that maybe suspended in it. During this process, the crude is pumped into large holding tanks, where the water and oil are allowed to separate and the contaminants settle out of the oil.
• 2 Next, the crude oil is heated to about 700 degrees Fahrenheit (371 degrees Celsius). At this temperature it breaks down into a mixture of hot vapor and liquid that is then pumped into the bottom of the first of two fractionating towers. Here, the hot hydrocarbon vapors float upward. As they cool, they condense and are collected in different trays installed at different levels in the tower. In this tower, normal atmospheric pressure is maintained continuously, and about 80 percent of the crude oil vaporizes.
• 3 The remaining 20 percent of the oil is then reheated and pumped into a second tower, wherein vacuum pressure lowers the residual oil’s boiling point so that it can be made to vaporize at a lower temperature. The heavier compounds with higher boiling points, such as tar and the inorganic compounds, remain behind for further processing.
Filtering and solvent extraction
• 4 After further processing to remove unwanted compounds, the lube oil that has been collected in the two fractionating towers is passed through several ultrafine filters, which remove remaining impurities. Aromatics, one such contaminant, contain six-carbon rings that would affect the lube oil’s viscosity if they weren’t removed in a process called solvent extraction. Solvent extraction is possible because aromatics are more soluble in the solvent than the lube oil fraction is. When the lube oil is treated with the solvent, the
aromatics dissolve; later, after the solvent has been removed, the aromatics can be recovered from it.
Additives, inspection, and packaging
• 5 Finally, the oil is mixed with additives to give it the desired physical properties (such as the ability to withstand low temperatures). At this point, the lube oil is subjected to a variety of quality control tests that assess its viscosity, specific gravity, color, flash, and fire points. Oil that meets quality standards is then packaged for sale and distribution.