Mecanico

Failure Analysis • Installation & Maintenance

®

Gear – Shafts – Bearings – Seals

CONTENTS

(Page 1 of 20)

1 - INTRODUCTION
Page

Part 1 Introduction. · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 1
Part 2 Gear Distress and Failure Modes · · · · · · · · · · · · · · · · · · · · 2
Surface Fatigue – Pitting · · · · · · · · · · · · · · · · · · · · · · · · · ·3
– Spalling · · · · · · · · · · · · · · · · · · · · · · · · 5
Wear · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 6

– Degrees of Wear · · · · · · · · · · · · · · · · · · 7

–Types of Wear · · · · · · · · · · · · · · · · · · 8

– Miscellaneous Wear Modes · · · · · · · · · · 9
Plastic Flow · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·· 10
Breakage · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 11

Failure Associated with Processing · · · · · · · · · · · · · 13

Part 3 Shaft Distress and Failure Modes · · · · · · · · · · · · · · · · · · · 14
Part 4 Anti-Friction Bearing Failures · · · · · · · · · · · · · · · · · · · · · · 16
Part 5 Failure of Contact Oil Seals · · · · · · · · · · · · · · · · · · ·· · · 18

FIG. 1.1 (253-2) TORQUE METER RECORD

The function of the industrial power transmission gear drive is
to reliably transmit torque and rotary motion between a prime
mover and a driven piece of equipment at acceptable levels of
noise, vibration and temperature. When one or more of the
preceding operating characteristics exceeds allowable limits,
the drive and its applicationshould be examined to determine
the cause of the problem. Gear drive components most
commonly subject to distress are the gears, shafts, bearings
and seals. The purpose of this paper is to describe a number
of distress and failure modes of each of these components and
to indicate probable causes and possible remedies for these
failure modes.
For drives that are properly designed andmanufactured,
abnormal distress or failure can result from misapplication or
poor installation or poor maintenance.
Continuous steady state overloads can result from erroneous
initial power requirement calculations, over motoring,
increased output demands, etc. Such loading should be
detectable by motor overheating or from electrical meter
readings on the driving motor.
Momentary or transient peakloads are of such short duration
that electrical meters do not respond accurately to them. In
such cases torquemeter readings of instantaneous loads, as
shown in Figure 1.1 may be necessary to determine actual
torque loads.

FIG. 1.2 (253-1) TORQUE METER RECORD

The Falk Corporation, P
.O. Box 492, Zip 53201-0492
3001 W. Canal St., Zip 53208-4200, Milwaukee, WI USA Telephone: 414-342-3131Fax: 414-937-4359 e-mail: falkinfo@falkcorp.com web: www.falkcorp.com

108-010

August 1978 (.pdf revision)
Replaces 690801

Installation & Maintenance • Failure Analysis
(Page 2 of 20)
Gear – Shafts – Bearings – Seals
Vibratory loads, or system dynamic loads depend on the
interrelation of the components in the entire system with one
another and torquemeter readings or a study of thesystem is
required to assess instantaneous loads. From properly
obtained torquemeter readings, see Figure 1.2, the load
characteristics of the system can be determined including
steady state loads, peak loads, accelerating loads, reversing
and vibratory loads and other dynamic effects that may exist.
Once the nature of the load within a system has been
established, the manner in which theload affects each of the
drive components must then be assessed.
Unexpected environmental conditions affecting gear drive
performance can be grouped into three categories:
1 – ambient temperature, either high or low
2 – airborne abrasive material
3 – corrosive materials of gaseous, liquid or solid form
Ambient temperatures that are too high may result in lube
temperatures so high that...