Earthmover tyre fitment and rotation: Strategies for mines

Harry Godwin 2012 Bachelor of Materials Engineering (Hons) – University of Queensland

2012 – 2016 Otraco International -Extreme tyre enthusiast -Spend too much time looking ahead (crystal ball style) -Developed new automated forecasting program specific to OTR tyres. -Living and breathing numbers

Tyre Fitting is Dangerous Work All fatalities associated with rubber tyred equipment maintenance (Australian mining industry, 1980 – present)

3 x tyre fitters

8 x non tyre fitters Fatalities during non – tyre equipment maintenance

Fatalities while servicing tyres

Most fatalities were caused by tyres or rims during only 2% of total

machine hours.

Fatality risk up to 10 x higher.

How do we reduce this exposure? Best practice procedures Fit-for-purpose tooling Trained and competent tyre fitting

personnel Custom built tyre bay/changing facility

What else….? Improved tyre life Tyre rotation and fitment strategies

Normal Life Cycle of an OTR Tyre OTR haul truck tyres start life fitted

to the front axle

After certain interval (nominally33% of life) tyre is removed

Placed into “run out” stock

Then tyre is fitted to rear axle to be “run out”

How to reduce the number of tyre changes?

Increase tyre life

Line up major component changes and rim Non-Destructive Testing (NDT)

Smarter tyre rotation strategies

Better tyre specification selection for site application

The Effect of Tyre Life on Tyre Changes

300 900

800 250

New

Tyr

e R

equi

rem

ents

and

Tyr

e

Cha

nges

120

240

720

103

206 617

Proj

ecte

d D

ownt

ime

Hou

rs

Base calculation

Number of tyre hours required / average tyre life

6 tyre positions per truck

200

150

100

50

700

600

500

400

0 300 ~500 engine hours Tyre Life = 6,000 hours Tyre Life = 7,000 hours per truck per month

New Tyres Required Minimum Tyre Changes Minimum Annual Downtime 500 x 12 x 20 =

120,000 operational tyre hours/year Haul Truck Fleet

-20 Trucks -Availability: 86% -Utilisation: 80%

Truck Config. -Front axle: 2 tyres -Rear axle: 4 tyres (two sets of duals)

Change Time = 3 hours Min. changes per tyre = 2

Potential Tyre Fitment and Rotation Strategies

Fit new tyres as required (no rotation strategy)

Fit all new tyres to front axle positions only

Fit a proportion of new tyres to rear axle positions

Tyre Usage and Rotation Strategy

0

50

100

150

200

Num

ber o

f Tyr

es

Front Rotation Interval (Hours) New-To-Front Tyres New-to-Rear Tyres Total Tyre Requirements Run Out Tyres Required

Change @ 33% Life Total Tyres Required = 120

Change @ 67% Life Total Tyres Required = 120

Total New Tyre Requirements

New-to-Rear tyre fitments Common arguments against new-to-rear fitments Tyres more likely to fail prematurely on the rear

It’s preferable to lose a well worn tyre due to premature failure

Problem with these arguments As the proportion of new tyres fitted to the front axle increases,

front tyres have to be replaced at even lower average life

Average haul truck life overall is independent of the proportion of new tyres fitted by axle

There is a considerable detrimental effect on haul truck downtime

The Tyre Change Index Tyre Change Index = Proportion of new tyre fitment to front axle + 1

All tyres fitted new to front: Index = 2.0 40% of tyres fitted new-to-rear: Index = 1.6 Result – 20% decrease in haul truck downtime

Tonnes-Kilometres-Per-Hour TKPH is the work rating of a tyre. This work rating is similar to the load capacity of a tyre, but also

accounts for heat generation due to load, speed and flexing.

Value given to all Earthmover tyres by manufacturers. In theory, if SITE TKPH is less than a rated TYRE TKPH

operation can occur with little risk of heat failures.

Operational TKPH Low High

Select more cut resistant compounds Select more heat resistant compounds

Positives -Slower wear -Fewer rock cuts -Fewer sidewall cuts Negatives -Can’t tolerate high speeds

Selected tyre always has to

be a compromise

Positives -Copes well with high speeds Negatives -Faster wear -More prone to rock cuts & sidewall damage

TKPH = Average Work Day Speed x Average Tyre Load

Good starting point for tyre selection.

TKPH – Real Life Data - Lower TKPH on the rear axle

0

250

500

750

1000

1250

1500

1750

2000

3:30 PM 29-Jul-15

9:30 PM 29-Jul-15

3:30 AM 30-Jul-15

9:30 AM 30-Jul-15

3:30 PM 30-Jul-15

9:30 PM 30-Jul-15

3:30 AM 31-Jul-15

9:30 AM 31-Jul-15

Ope

ratin

g TK

PH /

Tyre

TK

PH R

atin

g

Komatsu 930E Dump Truck

Front TKPH 4 hour moving Avg. Rear TKPH 4 hour moving Avg. 53/80R63 Bridgestone VRPS E3A E-4 53/80R63 Bridgestone VRPS E1A E-4 TKPH Rating – Heat Resistant Compound TKPH Rating – Standard Compound

Case Study – Coal Site New fleet of 17 ultra-class trucks mobilised on site. New 53/80R63 tyres (same specification/rubber compound)

fitted to front and rear axle of most trucks. Batch analysis showed the following results for tyre life.

Tyre

Life

(Hou

rs)

Average Tyre Life by Fitment Axle 6,500

6,250

6,000

5,750

5,500 New Fitments (2011-2012)

New-To-Front New-To-Rear

5,926

6,285

No corrections for uneven wear

completed

New-to-Front 30 tyres fitted 2.7 changes per tyre

New-to-Rear 54 tyres fitted 1.9 changes per tyre

-43 tyre changes saved -Tyre life ~4% higher

Case Study – Hard Rock 220 tonne truck fleet (20 trucks) – 40.00R57 tyres New tyre fitments occurred 2011-2012 Standard Compound (regular TKPH rating) – front axle Abrasion/Cut Resistant Compound (low TKPH rating) – rear axle

(seasonal)

Stnd Tyres -Life = 3,898 hrs

-New Tyres = 178 Changes/tyre = 4.0

Cut Resistant Tyres -Life = 4,376 hrs -New Tyres = 53

Changes/tyre = 3.5

Est. Cost = $8.085M Total Changes = 898 Downtime = 1,041

Standard Tyres -Life = 3,969 hrs

-Equiv. New Tyres = 238

Est. Cost = $8.325M Total Changes = 951 Downtime = 1,105 R

ecom

men

ded

Prac

tice

Stan

dard

Prac

tice

Two Pronged Approach: Tyre Selection and Fitment Policy

0

50

100

150

200

Num

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f Tyr

es

Front Rotation Interval (Hours) New-To-Front Tyres New-to-Rear Tyres Total Tyre Requirements Run Out Tyres Required

Tyre Life: New-to-Front = 6,000 hours New-to-Rear = 7,500 hours

Tyre Changes: Front Fitments = 2 Rear Fitments = 1

100% New-To-Front New Tyres = 120 Tyre Changes = 240

Front Rotat. Int. +50% 80 Tyres New-To-Front 32 Tyres New-to-Rear Tyre Changes = 192

Potential Benefits Reduced annual tyre usage by 8 @ $50,000 / tyre = $400,000

Reduced minimum tyre changes by 48 At 3 hours/change = 144 hours tyre related downtime

Fitting tyres new-to-rear the most effective method to rectify run-out stock levels

Wear rates decreased – Asymmetric (uneven) wear severity reduced

Summary Easy change to tyre management practices on site

Check TKPH requirements of front and rear axle for your major haul truck fleets

Fit more cut resistant tyres to rear axle (if appropriate)

Benefits Lower exposure to high risk tyre change activities

Increased truck availability (fewer tyre changes)

Increased tyre life

Reduced annual tyre usage for haul fleets

Thank You

4th August 2016