What Is Tribology?

what is tribology

The term“Tribology” is derived from a Greek work “Tribos” which originally means“rubbing”. So the simplest way to explain What Is Tribology is that “Tibology”is the analysis of the rubbing surfaces, i.e. the friction, wear and lubrication analysis. It is a complete science it self, which deals with the detailed study and analysis of four major factors involved for the prevention from wear and tear of the sliding surfaces:

• Corrosion: destruction or degradation of material by electrochemical or chemical reactions between the surface and environment.


• Abrasion : It is a mechanical process, in which the sliding surfaces start scratching or scuffing away.


• Adhesion: It is the attraction between dissimilar particles or the surfaces


• Erosion: Layer by layer degradation or destruction of material surface.

It not only helps in minimizing the wear and tear of the surfaces, but also helps in extending the working life of the equipments. Although tribology is more about mechanical engineering, then chemical engineering; but the processes under tribology tree are more concerned with the chemical engineering. Out of them, Lubrication is the most important.

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Lubrication is probably the vital science, used in the field of Tribology. Lubrication works by making the surfaces in contact more slippery and greasy to eliminate several factors like overheating, friction, or tearing. There are several different types of Lubricants, which are used for different surfaces; most important of them are Petroleum lubricants, Synthetic Oils, Greases, Solid film lubricants and Metal films.

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The application sectors of the tribology are unlimited, from a little lip gloss to the very large machinery or equipment, every single substance, which has to slide on any other substance, is designed by keeping the rules of tribology in mind. With the help of tribology, the friction losses, and other heat losses are minimized, and so is the operational cost of the process.

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What Is Tribology?

The term“Tribology” is derived from a Greek work “Tribos” which originally means“rubbing”. So the simplest way to explain What Is Tribology is that “Tibology”is the analysis of the rubbing surfaces, i.e. the friction, wear and lubricationanalysis. It is a complete science it self, which deals with the detailed studyand analysis of four major factors involved for the prevention from wear andtear of the sliding surfaces:

• Corrosion: destruction or degradation of material by electrochemical or chemical reactions between the surface and environment.
• Abrasion : It is a mechanical process, in which the sliding surfaces start scratching or scuffing away.
• Adhesion : It is the attraction between dissimilar particles or the surfaces
• Erosion : Layer by layer degradation or destruction of material surface.

Itnot only helps in minimizing the wear and tear of the surfaces, but also helpsin extending the working life of the equipments. Although tribology is moreabout mechanical engineering, then chemical engineering; but the processesunder tribology tree are more concerned with the chemical engineering. Out ofthem, Lubrication is the most important.

Lubricationis probably the vital science, used in the field of Tribology. Lubricationworks by making the surfaces in contact more slippery and greasy to eliminateseveral factors like overheating, friction, or tearing. There are severaldifferent types of Lubricants, which are used for different surfaces; mostimportant of them are Petroleum lubricants, Synthetic Oils, Greases, Solid filmlubricants and Metal films.

Theapplication sectors of the tribology are unlimited, from a little lip gloss tothe very large machinery or equipment, every single substance, which has toslide on any other substance, is designed by keeping the rules of tribology inmind. With the help of tribology, the friction losses, and other heat lossesare minimized, and so is the operational cost of the process.

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What is Desalination

Desalination(also called as Desalting) refers to the methods that remove the dissolvedminerals, and salt from the brackish water (having salt concentrations from 5ppt to 20 ppt; while ppt abbreviates for parts per thousand) or sea water (> 20 ppt), to produce clean and pure water, which can be easily used fordomestic or industrial purposes.

How Does Desalination Work

There are many desalination methods used today. We can classify them as:

1) Thermal Desalination

Thermal desalination methods are the widely used desalination techniques all over the world. In thermal desalination, the water brings to boil by the applied heat or the high pressure, and then the water vaporizes and condenses as clean water. The method used for the thermal desalination is called as Distillation.

The distillation of salt water refers to the use of heat energy. The water is heated at a constant temperature, until its vapor pressure becomes equal to the atmospheric pressure (its boiling point attained) and the water begins to vaporize. The salt and other sediments mostly have the greater boiling point then that of the water, so the sediments kept at the bottom,while pure water vaporizes, condensed and used as the pure water, while the sediments left behind are treated separately.

The distillation methods used for industrial desalination of salt water are:

• Multi-Stage Flash Distillation (MSF)

In MSF, the water to be treated is heated in a container called “Brine heater”. Then the heated water enters to the second low pressure container called as “Stage”. Some amount of water starts boiling quickly,because of this lower pressure. The remaining water then flows to the next stage, where the pressure is even lower then that of the second stage, causing more vaporization of water. In the same way, MSF have 15-25 stages, each having lower pressure then the previous.

• Multiple Effect Distillation

It is similar to MSF, because it also works with the series of“effects” (containers), each having lower pressure then the previous one. The difference is that unlike stage, effect is made up of a container and a heat exchanger. So, the water boils, condenses and give rise to the water temperature of next effect.

• Vapor-Compression Distillation

It is generally used for small sized plants. During distillation, a steam jet or mechanical compressor generates heat. The feed water enters, partially vaporizes, and condenses into clean water.

2) Membrane desalination

Membrane desalination can also be divided into two more categories:

2.1)Method uses electric current to attract salt molecules through membrane

• Electro-Dialysis (ED)

In electrodialysis desalination,the electric current is passed through the membranes. The salt and other mineral particles, being ionic attracts towards the membranes leaving desalinated water behind. It has higher water recovery then RO, but generally not usable for sea water, because of higher concentration of salt.

• Electro-Dialysis Reversal (EDR)

This is same as ED, but in reverse.

2.2)Method uses high pressure to force water through membrane

• reverse osmosis

It is the reverse phenomena of Osmosis. It can remove suspended solids, all minerals, organic elements like algae and bacteria and salt from the water. A semi-permeable membrane separates solutions with different concentrations of suspended minerals. An applied pressure forces the dissolved minerals from the higher concentration solution to move towards the lower concentration solution.

• Nano-filtration

It is some what similar to the RO, the membrane used innano-filtration has larger pore size then that of the RO, and so the lesser pressure is needed to be exerted to pass the water through the membrane.

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What is Desalination

Desalination (also called as Desalting) refers to the methods that remove the dissolved minerals, and salt from the brackish water (having salt concentrations from 5 ppt to 20 ppt; while ppt abbreviates for parts per thousand) or sea water ( > 20 ppt), to produce clean and pure water, which can be easily used for domestic or industrial purposes.

How Does Desalination Work

There are many desalination methods used today. We can classify them as:

1) Thermal Desalination

Thermal desalination methods are the widely used desalination techniques all over the world. In thermal desalination, the water brings to boil by the applied heat or the high pressure, and then the water vaporizes and condenses as clean water. The method used for the thermal desalination is called as Distillation.

The distillation of salt water refers to the use of heat energy. The water is heated at a constant temperature, until its vapor pressure becomes equal to the atmospheric pressure (its boiling point attained) and the water begins to vaporize. The salt and other sediments mostly have the greater boiling point then that of the water, so the sediments kept at the bottom, while pure water vaporizes, condensed and used as the pure water, while the sediments left behind are treated separately.

The distillation methods used for industrial desalination of salt water are:

• Multi-Stage Flash Distillation (MSF)

In MSF, the water to be treated is heated in a container called “Brine heater”. Then the heated water enters to the second low pressure container called as “Stage”. Some amount of water starts boiling quickly, because of this lower pressure. The remaining water then flows to the next stage, where the pressure is even lower then that of the second stage, causing more vaporization of water. In the same way, MSF have 15-25 stages, each having lower pressure then the previous.

• Multiple Effect Distillation

It is similar to MSF, because it also works with the series of “effects” (containers), each having lower pressure then the previous one. The difference is that unlike stage, effect is made up of a container and a heat exchanger. So, the water boils, condenses and give rise to the water temperature of next effect.

• Vapor-Compression Distillation

It is generally used for small sized plants. During distillation, a steam jet or mechanical compressor generates heat. The feed water enters, partially vaporizes, and condenses into clean water.

2) Membrane desalination

Membrane desalination can also be divided into two more categories:

2.1) Method uses electric current to attract salt molecules through membrane

• Electro-Dialysis (ED)

In electrodialysis desalination, the electric current is passed through the membranes. The salt and other mineral particles, being ionic attracts towards the membranes leaving desalinated water behind. It has higher water recovery then RO, but generally not usable for sea water, because of higher concentration of salt.

• Electro-Dialysis Reversal (EDR)

This is same as ED, but in reverse.

2.2) Method uses high pressure to force water through membrane

• reverse osmosis

It is the reverse phenomena of Osmosis. It can remove suspended solids, all minerals, organic elements like algae and bacteria and salt from the water. A semi-permeable membrane separates solutions with different concentrations of suspended minerals. An applied pressure forces the dissolved minerals from the higher concentration solution to move towards the lower concentration solution.

• Nano-filtration

It is some what similar to the RO, the membrane used in nano-filtration has larger pore size then that of the RO, and so the lesser pressure is needed to be exerted to pass the water through the membrane.

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Distillation

Distillation is the phenomenon of separation of mixtures into the individual components at their boiling points. Distillation is almost widely used method in chemical,petrochemical and other process industries, and is generally used to carry out the separation of those mixtures, which are impossible from other separation methods like the separation of fractions from crude oil, distillation of salt water, separating components of air, distillation of alcohols etc.

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The distillation method is based on the difference in composition between the liquid mixture and the vapors formed from this mixture. However there is also a specific type of the distillation, known as “Azeotropic distillation”. In chemical engineering, the azeotropic distillation is the one, in which the vapors and liquids have exactly the same composition at equilibrium. The most common example of the Azeotropic distillation is the ethanol-water system. Experimentally the composition of vapor and liquids at the equilibrium is determined by the vapor-liquid equilibrium, and the results are expressed as the temperature-composition diagram.

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There are many types of distillation based on the application criteria and the number of components in the mixture. Some important types for a chemical engineer to know are described as under:

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1)    Differential Distillation

It is the most elementary form of the batch distillation, in which the liquids mixture is brought to the boiling temperature of the low volatile liquid. The lower volatile liquid is vaporized and condensed. So the mixture is separated as the two components. This method is also carried out fora single liquid having impurities. I.e. it utilizes single equilibrium stage to obtain separation. But this is the single stage process, so complete separation is impossible in this system, so this system is used for the processes where high purification is not needed.

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2)    Flash Distillation

It is also named as the equilibrium distillation. This is a single stage continuous process, in which the liquid mixture is partially vaporized, so the produced vapors are in equilibrium with the residual liquid.The process is carried out in such a way, that the feed stream is pumped through heater to the separator through a valve, where the pressure is reduced.So the liquid and vapors produced due to the reduction reaches to the equilibrium. Then the vapors are removed from the top of the separator, while the liquid is collected from the bottom.

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3)    Rectification

The rectification is also named as the fractional distillation. It is undoubtedly the most important distillation method, as in rectification, art of the separated vapors are condensed and returned back to the separator, to achieve highest purification. Now, how does fractional distillation work? The fractionating column is the special column used for this type of distillation having number of plates. The solution at the bottom is heated, and the vapors rises in the column, to the first plate, cools and condensed on the first plate, then the vapors from lower rises to the first plate, heats the liquid of this plate, whose vapors condensed at the second plate, and this vaporization-condensation cycle goes on, giving the high purity components. But the above describes fractionating column is an ideal column, in real does not occur at the same exact position,that’s why the concept of theoretical plate occurs.

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4)    Azeotropic Distillation

As described above, this is the distillation in which the vapors and liquids have the same composition at equilibrium. The water-Ethanol mixture is the perfect example of the azeotropic distillation. If this water-ethanol mixture is distilled, then the alcohol concentration increases in vapors, until it reaches 96% by mass, i.e. the concentration of vapors and liquid is same. In process engineering, the azeotropic distillation is handled by adding a new element to the mixture(termed as entrainer in the case of azeotropic distillation), which can increase the relative volatility of the two main components. In actual, the third added component makes an azeotrope with one or more components of the mixture. Benzene is added to the water-Ethanol mixture as the third component,and makes a ternary azeotrope with a boiling point lesser then that of the binary mixture.

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5)    Extractive Distillation

This method is almost similar to that of the azeotropic distillation, i.e. for those mixtures, which are unable to distilled by any other method, a third component (termed as solvent for extractive distillation), is added which changes the relative volatility of the components, thus leading to separation. The extractive distillation is used, when the relative volatility of the binary component is very low, and if the continuous distillation is carried out, then it will give almost same purity products with high reflux rations, and thus the greater heat consumption and the requirement for the tower having large cross section areas, and number of plates.

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The basic difference between above two methods of distillation is very simple, the substance added in azeotropic distillation forms anazeotrope with the components of the mixture, while the substance added in extractive distillation in non-volatile in comparison with other components and thus added continuously from top of the column, so it run down as the reflux.

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There are several other types of distillation like steam distillation, vacuum distillation, air sensitive vacuum distillation,

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Distillation

Distillation is the phenomenon of separation of mixtures into the individual components at their boiling points. Distillation is almost widely used method in chemical, petrochemical and other process industries, and is generally used to carry out the separation of those mixtures, which are impossible from other separation methods like the separation of fractions from crude oil, distillation of salt water, separating components of air, distillation of alcohols etc.

The distillation method is based on the difference in composition between the liquid mixture and the vapors formed from this mixture. However there is also a specific type of the distillation, known as “Azeotropic distillation”. In chemical engineering, the azeotropic distillation is the one, in which the vapors and liquids have exactly the same composition at equilibrium. The most common example of the Azeotropic distillation is the ethanol-water system. Experimentally the composition of vapor and liquids at the equilibrium is determined by the vapor-liquid equilibrium, and the results are expressed as the temperature-composition diagram.

There are many types of distillation based on the application criteria and the number of components in the mixture. Some important types for a chemical engineer to know are described as under:

1)     Differential Distillation

It is the most elementary form of the batch distillation, in which the liquids mixture is brought to the boiling temperature of the low volatile liquid. The lower volatile liquid is vaporized and condensed. So the mixture is separated as the two components. This method is also carried out for a single liquid having impurities. I.e. it utilizes single equilibrium stage to obtain separation. But this is the single stage process, so complete separation is impossible in this system, so this system is used for the processes where high purification is not needed.

2)     Flash Distillation

It is also named as the equilibrium distillation. This is a single stage continuous process, in which the liquid mixture is partially vaporized, so the produced vapors are in equilibrium with the residual liquid. The process is carried out in such a way, that the feed stream is pumped through heater to the separator through a valve, where the pressure is reduced. So the liquid and vapors produced due to the reduction reaches to the equilibrium. Then the vapors are removed from the top of the separator, while the liquid is collected from the bottom.

3)     Rectification

The rectification is also named as the fractional distillation. It is undoubtedly the most important distillation method, as in rectification, art of the separated vapors are condensed and returned back to the separator, to achieve highest purification. Now, how does fractional distillation work? The fractionating column is the special column used for this type of distillation having number of plates. The solution at the bottom is heated, and the vapors rises in the column, to the first plate, cools and condensed on the first plate, then the vapors from lower rises to the first plate, heats the liquid of this plate, whose vapors condensed at the second plate, and this vaporization-condensation cycle goes on, giving the high purity components. But the above describes fractionating column is an ideal column, in real does not occur at the same exact position, that’s why the concept of theoretical plate occurs.

4)     Azeotropic Distillation

As described above, this is the distillation in which the vapors and liquids have the same composition at equilibrium. The water-Ethanol mixture is the perfect example of the azeotropic distillation. If this water-ethanol mixture is distilled, then the alchohol concentration increases in vapors, until it reaches 96% by mass, i.e. the concentration of vapors and liquid is same. In process engineering, the azeotropic distillation is handled by adding a new element to the mixture (termed as entrainer in the case of azeotropic distillation), which can increase the relative volatility of the two main components. In actual, the third added component makes an azeotrope with one or more components of the mixture. Benzene is added to the water-Ethanol mixture as the third component, and makes a ternary azeotrope with a boiling point lesser then that of the binary mixture.

5)     Extractive Distillation

This method is almost similar to that of the azeotropic distillation, i.e. for those mixtures, which are unable to distilled by any other method, a third component (termed as solvent for extractive distillation), is added which changes the relative volatility of the components , thus leading to separation. The extractive distillation is used, when the relative volatility of the binary component is very low, and if the continuous distillation is carried out, then it will give almost same purity products with high reflux rations, and thus the greater heat consumption and the requirement for the tower having large cross section areas, and number of plates.

The basic difference between above two methods of distillation is very simple, the substance added in azeotropic distillation forms an azeotrope with the components of the mixture, while the substance added in extractive distillation in non-volatile in comparison with other components and thus added continuously from top of the column, so it run down as the reflux.

There are several other types of distillation like steam distillation, vacuum distillation, air sensitive vacuum distillation,

Read More