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Lubricating Principles and Lubricating Oils

A. Bhatia, B.E.


Course Outline

Lubrication can be a daunting obstacle to someone unfamiliar with its basic concepts. Even someone with experience can be confused by the technology combined with the multitude of lubricants available on the market today. Reviewing a few of the basic principles of lubrication can make it easier to see why proper lubrication is necessary in every application.

This 2-hr course material is based entirely on the US Army Corps of Engineers document EM 1110-2-1424, "Lubricants and Hydraulic Fluids" and covers Chapter 2; "Lubrication Principles" and Chapter 3, "Lubricating Oils".
The course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the readers will:

Intended Audience

This course is aimed at students, mechanical and process engineers, O & M professionals, H &S professionals, machinery specialists, energy auditors, plant layout professionals and general audience.


Course Introduction

The primary function of lubrication is to help reduce friction and the secondary benefits include cooling, minimizing wear, extend longevity and reduce production down time. To minimize friction, an effective lubricant should be able to handle the pressures and speeds of the surfaces it will separate.

Although there are many ways to reduce friction, the most common way is through the use of a fluid or semi-fluid material. The key characteristic of such materials is that they are not readily compressible. Fluid and semi-fluid materials allow us to minimize component contact or eliminate contact altogether. These fluids are commonly referred to as lubricants.

In this course, you will learn the basic principles of lubrication and the relative merits between different types of lubricant oils.

Course Content

In this course, you are required to study US Army Corps of Engineers document EM 1110-2-1424, "Lubricants and Hydraulic Fluids":

EM 1110-2-1424, "Lubricants and Hydraulic Fluids" - Chapter 2 "Lubrication Principles"

EM 1110-2-1424, "Lubricants and Hydraulic Fluids" - Chapter 3 ""Lubricating Oils"

You need to open or download above documents to study this course.

Course Summary

There are three types of lubrication situations that can exist between two surfaces separated by a lubricant. Whether or not these situations occur is dependent upon the ability of the lubricant to provide adequate protection to the moving surfaces.

1) Full Fluid Film Lubrication: The condition in which surfaces are completely separated by a continuous film of lubricating fluid and are also commonly referred to as Hydrodynamic Lubrication. Although hydrodynamic lubrication is the ideal lubrication scenario, in many situations it cannot be maintained. Hydrodynamic lubrication is limited by the lubricant's viscosity, the rotation speed or RPM and by component loading. An increase in load decreases oil film thickness.

2) Boundary Lubrication is a condition in which the lubricant film becomes too thin to provide total surface separation. This may be due to excessive loading, low speeds or a change in the fluid's characteristics. In such a case, contact between surface asperities (or peaks and valleys) occurs. Friction reduction and wear protection is then provided via chemical compounds rather than through properties of the lubricating fluid.

3) The third type lubrication situation is known as Elastohyrodynamic Lubrication (EHD or EHL). This situation occurs as pressure or load increases to a level where the viscosity of the lubricant provides higher shear strength than the metal surface that it supports. As a result, the metal surfaces deform elastically in preference to the highly pressurized lubricant. This increases the contact area and decreases the effectiveness of the lubricant.

Lubricating oils are generally composed of two groups of materials. The first is a base or stock fluids which are produced from the refinement of petroleum crude oil or vegetable oils. These stocks are further classified as Paraffin and Naphthenic oils. To this, base or stock chemical compounds may be added to enhance or impart new properties to the mineral oil. These compounds are commonly referred to as additives. The other category is the synthetic oils that are produced from chemical synthesis. The properties and performance features of synthetics provide lower pour points, lower coefficients of friction, better oxidation stability and a better viscosity index and are generally superior to mineral lubricants in most circumstances.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

Take a Quiz

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.