Basics of Lubricants

7/25/2019 Basics of Lubricants

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Lubricant CompositionWhat you need to know

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Definition of Lubricants

Functions of Lubricants

Constituents of Lubricants

Types & comparison of mineral oils

Synthetic Lubricants

Additives for Lubricants

Greases

Advantages/Disadvantages of greases

NLGI classificationVarious thickeners and their advantages

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CONTENTS


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Lubricants are those substances, when introduced between two

solid surfaces which move over one another reduce resistanceto movement or friction and wear

Lubricants may be in any of the following forms :

Oils

Greases

Powders

Pastes

Dry-film

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WHAT ARE LUBRICANTS?


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Reduce friction by forming a separating film between two

contact surfaces

Reduce wear

Absorb shock

Reduce temperature

Minimize corrosion

Seal out contaminants

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BASIC FUNCTIONS OF LUBRICANTS


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COMPOSITION OF LUBRICANTS


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CONSTITUENTS OF LUBRICANTS

Base oils: Synthetic or Mineral

Performance Enhancing Additives

Solid lubricants (optional)

Thickeners ( for greases only)

Oils Additives Solid lubricants

(optional)

Thickeners

(only for greases)

LUBRICANTS


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LUBRICANTS COMPOSITION

Paraffinic Naphthenic Aromatic

Mineral oil Synthetic oil


(optional)

Thickeners

(only for greases)

LUBRICANTS


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MINERAL OILS - TYPES

Paraffinic Wide temp. range

High viscosity index

Poor low temperature properties

Naphthenic Good low temperature property Good additive compatibility

Aromatic Usually dark in color

High flash point

Unstable to temperature


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MINERAL OILS - COMPARISON

Type Naphthenic Paraffinic

Viscosity, cSt 38C 21 21

Viscosity Index 15 100

Pour point, C - 46 -10


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Mineral oil Synthetic oil

Oils Additives Solid lubricants(optional)

Thickeners(only for greases)

LUBRICANTS


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SYNTHETIC OIL - TYPES

Synthesized Hydrocarbons (PAO Polyalphaolefin)

Organic Esters diester & polyol ester

Polyglycols

Phosphate esters

Silicones

polymerized siloxanesPerfluoroalkyl Polyethers

Alkylated aromatics

Polybutenes


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RELATIVE COST OF SYNTHETIC OILS

Type Relative Cost

(Mineral oil cost =1)

1 Alkylated aromatic 2-3

2 Polybutenes 3-5

3 Esters 7-15

4 Polyglycols 7-20

5 PAO 7-25

6 Polyolesters 10-20

7 Silicones 40-200

8 Perfluoroalkyl Polyethers 400-800


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Additives are chemical compounds added to lubricating

oils/greases to impart specific properties to the finishedoils/greases for enhancing properties already present, in

addition to imparting new and useful properties.

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ADDITIVES

Oils

Surface active Performance

enhancing

Additives Solid lubricants

(optional)

Thickeners

(only for greases)

LUBRICANTS


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Pour point depressants

Viscosity Index improvers

Oxidation Inhibitors

Corrosion Inhibitors

Rust Inhibitors

Detergents and Dispersants

Antiwear additives

EP additives

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ADDITIVES


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Performance enhancing additives that influence the physical

and chemical properties of base fluids(VI improver, Lowtemperature property improver, antioxidant etc)

Additives that affect primarily the metal surfaces modifying

their physicochemical properties(EP, Antiwear, corrosioninhibitor, friction modifiers etc.)

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CLASSIFICATION OF ADDITIVES


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LUBRICANT COMPOSITION


(optional)

Thickeners

(only for greases)

LUBRICANTS


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Molybdenum-Di-Sulphide

Graphite

Zinc Sulphide

PTFE (Teflon)

Titanium Di Oxide

Boron Nitride

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SOLID LUBRICANTS


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Are solid to semi-fluid products of the dispersion of a thickeningagent in a liquid lubricant.

When the thickening agent is more than 40 % they are calledgrease pastes.

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WHAT ARE GREASES?


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Advantages:

Have lower friction co-efficient

Adhere better to the surfaces

More water resistant

Operate over a wider temperature range

Seal against dirt and other contamination

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GREASES (vis--vis oils)


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Disadvantages:

Not the right choice when heat transfer is a problem

Have a lower speed limit

More susceptible to oxidation.

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GREASES (vis--vis oils)


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Classification of greases by NLGI numbers

No. Appearance Penetration Used in

000 Semi-Fluid 445-475 Gears

00 Semi-Fluid 400-430 Gears

0 Very Soft 355-385 Gears

1 Soft 310-340 Bearings

2 Medium Soft 265-295 Bearings

3 Creamy 220-250 Bearings

4 Stiff 175-205 Seal

5 Soap like 130-160 Seal

6 Hard 85-115 Block grease


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(optional)

Soap based Non-soap based

Thickeners

(only for greases)

LUBRICANTS


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Soap Based: Lithium/Lithium complex

Calcium/Calcium Complex/Calcium Sulphonate

Lithium - Calcium

Aluminum/Aluminum complex

Sodium

Titanium complex

Barium

Non-Soap based Poly urea

Bentonite (Clay)

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THICKENERS


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Complex soaps have high drop points

Al-Complex is the easiest to pump, has good water

resistance and has good adherence.

Sodium soaps have good corrosion resistance.

Lithium soaps are good for multi-purpose application

Calcium soaps have good water resistance.

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ADVANTAGE OF VARIOUS THICKENERS


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Aluminum greases are very transparent and smooth

Polyurea based greases have extremely good oxidation

resistance and high temp. stability

Lithium and Calcium greases have better water resistance,

shear stability, better wear and friction performance.

Barium greases have high water resistance and shear

stability.

Calcium Sulphonate greases have superior corrosion and

shear resistance and have high load carrying capacity

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ADVANTAGES OF VARIOUS THICKENERS (contd.)


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Pour point depressants (also known as PPDs)

are polymers that are designed to control wax

crystal formation in lubricants resulting in lower

pour point and improved low temperature flow

performance

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POUR POINT DEPRESSANTS


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THANK YOU

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Basics of Lubricants

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