Lubricants and Their Importance

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Questions and Answers

What is the primary purpose of lubrication in machines?

To enhance the appearance of machine parts

To minimize energy loss due to friction (correct)

To increase operational speed

To reduce the impact of vibrations

Which characteristic of a lubricant is essential for preventing metal contact and scoring between gear teeth?

Adhesion

Cooling capacity

Chemical stability

Film strength (correct)

In which type of lubrication is a thick film of lubricant formed to prevent direct contact between surfaces?

Solid lubrication

Hydrodynamic lubrication (correct)

Extreme pressure lubrication

Boundary lubrication

What is one of the key functions of a lubricant regarding heat?

To reduce heat energy loss Signup and view all the answers

Which property of lubricants aids in preventing the loss of lubrication due to centrifugal forces?

Adhesion Signup and view all the answers

What type of lubrication occurs when lubrication film thickness fails, but extreme pressure protection is provided?

Extreme pressure lubrication Signup and view all the answers

Why is viscosity an important characteristic of lubricants?

It ensures smooth operation and cushioning. Signup and view all the answers

What is one result of lubrication in terms of machine lifespan?

Extended machine life Signup and view all the answers

What is the primary feature of structural lubricants that makes them effective?

They have a layered lattice structure. Signup and view all the answers

Which type of lubricant is specifically designed for extreme conditions like those in aircraft engines?

Synthetic lubricants Signup and view all the answers

Which of the following lubricants is commonly used in rocketry and defense programs due to its high-temperature stability?

Refractories, ceramics, and glass Signup and view all the answers

What is a disadvantage of gas lubrication compared to liquid or solid lubricants?

Limited load capacity Signup and view all the answers

Which material is known for being thermally stable and anti-corrosive, and is used in aircraft turbines?

Poly alkylene glycols (PAGs) Signup and view all the answers

What is a common property of chemically active lubricants?

They react with metal surfaces. Signup and view all the answers

Which of the following gases is NOT typically used in gas lubrication bearings?

Carbon monoxide Signup and view all the answers

What advantage do gas lubricated bearings have over liquid lubricants?

They are frictionless and silent. Signup and view all the answers

What does a higher viscosity index indicate about an oil's characteristics?

Better viscosity temperature characteristics Signup and view all the answers

What is the formula used to calculate the viscosity index (V.I.)?

V.I. = (U - H) x 100 / (L - H) Signup and view all the answers

Which temperature range is suitable for testing using the Cleveland open cup apparatus?

Between 120℃ - 250℃ Signup and view all the answers

If an oil has a flash point below 30℃, how is it classified?

Flammable liquid Signup and view all the answers

What typically happens to low flash point oils used in high temperature operations?

They may lead to higher oil consumption Signup and view all the answers

What is the minimum requirement for the flash point of a lubricant for domestic use?

Above 50℃ Signup and view all the answers

Which factor is NOT related to the measurement of the flash point and fire point?

Temperature of the ignition source Signup and view all the answers

What does the term 'fire point' refer to?

Temperature at which vapors burn continuously for more than 5 seconds Signup and view all the answers

What does the saponification value indicate about a fat or oil?

The average molecular weight of the fatty acids Signup and view all the answers

Which reaction is described in the saponification process?

Alkaline hydrolysis Signup and view all the answers

How is the saponification value mathematically calculated?

Using the volume of KOH used in the reaction Signup and view all the answers

What does a higher saponification value suggest about the fatty acids present in the oil?

They are longer chain fatty acids Signup and view all the answers

Which of the following describes the neutralization number of an oil?

It measures the acidity or alkalinity of the oil Signup and view all the answers

What is the significance of the saponification value in relation to adulteration?

It suggests the presence of animal or vegetable oils in mineral oils Signup and view all the answers

In the equation for calculating saponification value, which variable represents the weight of the oil used?

Weight of KOH used Signup and view all the answers

When performing the pour point test, what does it signify if the oil shows no movement after tilting the jar horizontally for 5 seconds?

The oil is treated as solid Signup and view all the answers

What does the acidity number in an oil sample represent?

Mass of KOH required to neutralize 1g of oil Signup and view all the answers

What does a higher total acid number (TAN) indicate about oil?

Oil has undergone oxidation, leading to corrosion Signup and view all the answers

Which type of oil has an iodine value greater than 150?

Linseed oil Signup and view all the answers

What is the significance of iodine value in oils?

Shows the extent of unsaturation and tendency to oxidize Signup and view all the answers

How is the aniline point relevant in evaluating oils?

It characterizes the aromatic content and temperature for separation Signup and view all the answers

What type of oil is categorized with an iodine value less than 100?

Coconut oil Signup and view all the answers

What happens to oil as the neutralization point increases?

The age of the oil decreases Signup and view all the answers

What does a low iodine value indicate about an oil?

Good quality and less contamination Signup and view all the answers

Study Notes

Lubricants

Substances introduced between moving parts of machines to reduce friction.
Lubrication minimizes energy loss and friction between machine components.

Importance of Lubrication

Reduces friction and wear between moving parts.
Prevents heat generation, extending machine lifespan.
Decreases energy consumption and protects materials.
Acts as a sealant and contributes to overall machine efficiency.

Functions of Lubricants

Reduces contact between rubbing surfaces, minimizing wear and tear.
Serves as a coolant by reducing heat energy loss.
Enhances efficiency and lifespan by preventing excessive heat expansion.
Cleans and entraps dirt/foreign particles, protecting surfaces.
Reduces rust and corrosion, lowering maintenance costs.
Prevents frictional heat build-up, mitigating seizure risks.

Characteristics of Lubricants

Viscosity: Essential for smooth operation; good viscosity ensures effective cushioning.
Film Strength: Prevents metal contact and scoring between gear teeth.
Lubricity: Oiliness necessary for reducing friction.
Adhesion: Essential for maintaining lubrication under centrifugal forces.
Temperature Range: Normal operating temperatures range from 50°C to 550°C above ambient.
Chemical Stability: Prevents thickening and sludge formation; oxidation resistance is crucial.
Extreme Pressure Protection: Provides additional protection for heavily loaded gears.

Types of Lubrication

Hydrodynamic (Thick Film) Lubrication: Low friction coefficient (0.005-0.01); relies on a lubricant film.
Boundary (Thin Film) Lubrication: Contact occurs; relies on additives for protection.
Extreme Pressure Lubrication: Handles severe conditions with special additives.

Solid Lubricants

Structural Lubricants: Includes graphite and MoS2; widely used across various industries.
Mechanical Lubricants: Comprise plastics and metals.
Soaps: Form bonds with metal surfaces via fatty acids.
Chemically Active Lubricants: Include extreme pressure additives.
Refractories and Ceramics: Used at higher temperatures, especially in defense applications.

Synthetic Lubricants

Designed for extreme conditions, e.g., aircraft engines, with temperature ranges from -50°C to 250°C.
High performance with low freezing points and excellent thermal stability.
Suitable for high shear mechanical environments, used in aircraft turbines.

Gas Lubrication

Used in extreme conditions; involves gases like air, hydrogen, and nitrogen.
Provides advantages such as being virtually frictionless and silent.
Common applications include spindles and turbines.

Flash Point and Fire Point

Flash Point: Minimum temperature at which vapor ignites; an important safety characteristic.
Fire Point: Minimum temperature allowing continuous combustion for 5 seconds.
Both parameters are crucial for handling lubricants safely.

Measurement Techniques

Cleveland Open Cup Apparatus: Measures flash and fire points for petroleum products with specific temperature ranges.
Used to determine the pour point based on oil movement at regulated temperatures.

Saponification Value

Represents the amount of KOH required to saponify 1g of fat; indicates fatty acid chain length.
Provides insight into the extent of adulteration in oils.

Neutralization Number

Indicates acidity or alkalinity of oil; important for assessing oil condition.
Total Acid Number (TAN) and Total Base Number (TBN) compare against fresh oil to identify degradation.

Iodine Value

Measures unsaturated compounds in oils; sensitive to oxidation.
Classifies oils based on their tendency to absorb oxygen and indicates contamination levels.

Aniline Point

Reflects the minimum temperature at which aniline and lubricating oil are in equilibrium.
Used to characterize pure hydrocarbons and assess aromatic content in mixtures.

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Description

This quiz covers the essential aspects of lubricants used in machinery, including their functions and characteristics. Learn how lubrication reduces friction, extends machine lifespan, and contributes to overall efficiency. Test your knowledge on the unique properties that make lubricants vital for smooth operations.