3

-

High

concentration

of

wear

particles

-

Chipped

gears

Broken

-

planetary

gear

carriers

-

Broken

thrust

washers

and

so

on

These

are

observed

upon

draining

oil

or

upon

inspection,

leading

to

regular

differential

and

fnal

drive

overhaul.

In

some

cases,

tractors

end

up

losing

drive,

and

broken

half

shafts

are

often

discovered

as

a

result

.

The

incident

chart

below

il

lustrates

the

distribution

of

differential

failures

during

the

2017-2018

agricultural

season:

Incident

Chart

Showing

Differential

Failures

Wet

Season

Dry

Season

Differential

Failure

Incidents

As

shown

in

the

incident

chart

,

71%

of

differential

failures

occurred

during

the

wet

season

while

29%

occurred

during

the

dry

season.

In

al

l

these

failures,

broken

planetary

gear

carriers/spiders

were

discovered

upon

inspection.

Al

l

failures

were

linked

to

wet

weather

chal

lenges

and/or

post

wet

weather

impact

of

abrasive

wear.

The

introduction

of

wear

particles

in

the

differentials

and

fnal

drives

resulted

in

accelerated

wear

or

abrasive

wear.

The

end

result

is

a

spiral

effect:

as

more

wear

particles

are

generated,

the

wear

rates

increase

(advanced

wear)

and

in

some

cases

resulting

in

failures

which

are

costly,

especial

ly

in

terms

of

downtime

and

lost

production.

It

must

be

noted

that

the

above

are

only

symptoms,

not

the

root

cause

of

the

problem

at

hand.

To

get

to

the

root

source

of

this

phenomenon,

we

invoked

the

5-Why

analysis

technique:

Toyota’s

5-Why

strategy

is

a

good

trouble-

shooting

tool,

which

can

be

used

in

conjunction

with

the

WearCheck

oil

analysis

programme

to

discover

the

root

cause

of

a

phenomenon.

This

involves

asking

a

series

of

“why?”

questions

until

the

root

cause

of

the

problem

is

discovered

as

il

lustrated

below:

Problem

–

High

differential

failure

rate

1.

Why?

High

concentration

of

wear

particles

in

the

oil.

2.

Why?

Abnormal

wear

of

components.

3.

Why?

Chipped

gears/broken

drive

train

components.

4.

Why?

Tractors

stuck

in

the

felds/axle

spinning.

5.

Why?

Wet

weather

operating

conditions,

slippery

roads

and

felds.

Applied

solutions:

A

trend

in

operational

chal

lenges

has

been

noticeable

over

the

years.

To

counter

the

problem,

several

strategies

have

been

applied

to

remove

(avoid

wet

weather

operations

where

possible)

or

minimise

impact

(where

wet

weather

operations

cannot

be

avoided.)

These

strategies

are

discussed

below:

Assess

the

level

of

risk

Pay

attention

to

oil

analysis

severity

status

and

PQ

levels.

Pay

attention

to

repeat

problems.

Pay

attention

to

ICP

results

as

wel

l

in

view

of

holistic

analysis.

This

is

a

good

guide

to

determining

level

of

risk

.

Report

severity:

Normal

–

Low

risk

.

Borderline

–

Moderate

risk

.

Urgent

&

Critical

–

High

risk

.