Optimization of Load Per Trip of a Rear Discharge Dumper

Rohit Pandey1

1 B.E. Mining Engineering, Bengal Engineering and Science University, Shibpur 2008-2012

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Optimization of Load Per Trip of a Rear Discharge

Dumper at Quarry S-E Block

July 10

2011 Project Report of Summer Internship 2011 at TATA STEEL (West Bokaro Division)

: Rohit Pandey

Rohit Pandey1


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Acknowledgement:

Myself, Rohit Pandey currently pursuing B.E. in Mining Engineering at Bengal Engineering and Science

University, Shibpur am most thankful to TATA STEEL for giving me the opportunity to complete my

summer internship project here at West Bokaro Division. I would like to thank Professor Suranjan Sinha,

HOD Department of Mining engineering, BESUS and all of my faculty members for guiding me properly

over the duration of my course. Special thanks to Mr. Sunil Kesarwani, my Project Guide; Mr. N. K. Gupta

(Chief Q-SE Block) my Project Mentor for guiding me to the insights of the project given to me. Thanks to

Capt. Salil Mohan for helping us with all our needs, Mr. B. Dinesh for helping me around the mines during

the shifts, to Mr. Subhankar Bose for helping me get all possible data required for the project, and to all who

have helped me in completing my project, and specially to all my fellow summer interns for making this

Summer Internship Program memorable.

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CONTENTS:

Sl. No TOPIC PAGE NUMBER

1.0 Introduction to WBD 4

2.0 Location of West Bokaro 5

3.0 Scope of Work 6

4.0 Time Line 6

5.0 Understanding Shift Operations 7

6.0 Dumper Specifications and Policy 7

7.0 Increase of mine revenues 8

8.0 What may go wrong 8

9.0 Effect of load on tires 9

9.1 Tire damage analysis 9

9.2 Overloading of Tires 11

10.0 Factors relating load carried by dumper to tires 12

10.1 TKPH 12

10.2 Inflation pressure of the tires 17

10.2.1 Current status of tires in the mines 17

11.0 Optimization of Load capacity 20

12.0 Volumetric analyisis of dump body 22

13.0 Diesel Consumption Analysis 23

14.0 Speed Analysis 26

14.1 Speed during Out Pit Haul 26

14.2 Speed during In Pit Haul 27

15.0 Recommendation 28

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1.0 Introduction to West Bokaro Division, Tata Steel:

West Bokaro (WB) came into existence in 1948, as an independent coal company, managed by M/S

Anderson Wright under the managing agency system. Tata Steel acquired the Company in 1956 to meet its

requirement of metallurgical grade coal for Iron making. Subsequently, in 1976, WB was made a Division of

Tata Steel. In 1974, when coal mines were nationalized, WB was exempted as it produced coal only for

captive consumption of the Steel Works. The coal industry in India is highly regulated with only few private

players allowed to produce coal only for captive use (in steel, cement and power industry). India has very

low reserves of coking coal. Indian coals in general are not suitable for steel making being high in

incombustible matter (Ash-25-38%) and also difficult to wash for reducing Ash. The first Washery of the

country was set up in WB. The current Washeries are designed to reduce Ash from 36% to 17% at a yield of

38%. Any further reduction in Ash was considered uneconomical because of significant drop in yield. (5%

drop for 1% drop in Ash). Though Ash can be reduced by improving process & application of technology,

Rank of coal which is result of „Metamorphosis‟ cannot be changed. Hence a large quantity of coking coal is

imported for blending with Indian coal to make it suitable for iron making. The business objective of WB

Division is to produce clean coal at optimum cost for captive use in the steel plant of Tata Steel at

Jamshedpur. The strategy is to reduce Ash with minimum loss of yield so that quality of coal improves and

yet the cost is beneficial vis-a vis imported coal.

The primary product of WB is the metallurgical grade coal (also called CC), for Coke Ovens, which converts

coal into coke for use in the Blast Furnaces. The type of coal deposit in WB is that of medium grade

metallurgical coal containing a very high percentage of Ash. Tata Steel has developed stamp charged

technology for using the coal from WB after blending it with imported coal. The coal after mining is washed

in the coal beneficiation plants to lower down the ash content from an average of 36% to 13%. Nowhere in

world the coal is beneficiated from 36% to 13% and in this regard the coal beneficiation process at WB is

unique. This is a highly commendable achievement especially in view of the fact that Indian coal comes

under the category of “difficult to wash coal”.

In order to improve the productivity of the Blast Furnaces, it is beneficial to lower down the Ash of CC.

However, with every 1% drop in Ash of CC the yield drops by 4-5% resulting in lower volume of CC and

thereby increasing the cost of production of CC. Every year Ash was reduced from 17% to 16% and this year

Ash has been further reduced to 13% at a very short notice from the customer. There was an extreme

Fig 1: Mining Processes in use at Q-SE Block

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exigency to increase the productivity of blast furnaces in view of imminent shutdown of G-BF and recurring

problem of F-BF. The division responded to the demand of the customer immediately by reducing the Ash

from 15% to 13% level in 24 hours. The process is being stabilized and there is a continuous improvement in

yield even while reducing Ash. The delivery mechanism to steel plant at Jamshedpur is mainly through rail.

2.0 Location of West Bokaro:

Owner - H.M. Nerurkar (MD TATA Steel)

Location - West Bokaro is located about 200 km NW of Jamshedpur in Hazaribagh district. It is about

35 km SW of Hazaribagh town and 26 km NE of Ramgarh town.

Latitude - 23°46'41"N

Longitude - 85°33'6"E

Geographically, it is located west of Lugu Hill. It can be accessed via road from the town of Ramgarh. There

are several other coal mines, owned by M/s Central coal Fields Ltd around West Bokaro. The rain-fed

Bokaro River flows through the property. Total area of the leasehold is 4300 acres and contain an estimated

mine area reserves of about 180 million tonnes of Coal. The loading station at Chainpur is situated 4km to

the South.

Geology: Correlation of various coal seams was done on the basis of geological observations and available

data from boreholes and quarry sections. The Gondwanas of the Coalfiel doverlying unconformably the

Archeans are represented by the Lower Gondwanas - Talchirs, Kharharbaris, Barakars, Barren Measures,

Raniganjs, Panchets and the Upper Gondwanas -Mahadevas. About thirteen regionally persistent coal seams

have been established in the area. The thick coal seams of the Coalfield are seam-V (7m on average) and

seam-X (10m on average). The coal seams belong to low moisture, low volatile, medium to high caking

bituminous group. The Grade varies from Grade-II to IIIB. Seam VI and VII are the best quality coal seams

which attain Grade-I quality in Ghato and Pundi areas and seam-X also have Grade-I quality in Kuju area.

The total reserves for the Coalfield have been estimated to be 2500 million tonne up to 600m depth

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3.0 Scope of work:

The project aims to selecting an optimum load that a RD is subjected to carry per trip, based on the Cost

benefit model.

4.0 Time line of work:

Week 1 • Visit to the mine.

• Familiarizing with the basic mine unit operations

Week 2 • Understanding the scope of work

• Identification of basic parameters of the project

Week 3 • Tire analysis

Week 4

• Tire analysis continued

• Volumetric analysis

• Review of work

Week 5 • Troubleshooting of work done

Week 6 • Fuel Consumption and TPMS Data Analysis

Week 7 • Speed Analysis

Week 8 • Recommendations

• Submission of project report

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5.0 Understanding shift operations:

The 1st 3 days (17

th may – 19

th of may) I went to the SEB in the First Shift . In these 3 days I studied the

basic Shift operations which are as follows:

1. Development Job

2. Drilling & Blasting

3. Loading & Hauling

4. Dump yard and CHP

6.0 Dumper Specifications and Policy:

The dumper being used is of CATERPILLAR make, model 777D (dual slope)

The rated payload is 95 T (Caterpillar specifications)

The proper working of the dumper is subjected to the 10/10/20 policy by Caterpillar according to

which;

‘Only 10% of all loads carried by the dumper should exceed (110%) 1.1 times the rated payload and

No load should exceed (120%) 1.2 times the rated payload.’

Optimum Load Zone

Fig 2:- Graphical representation of 10-10-20 policy

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7.0 Increase of Mine Revenues:

Any increase of payload per trip will decrease the cost of handling of Over burden/cubic meter.

This will reduce the mining costs and will better the breakeven ratio, resulting in the increase in the mine

revenues.

Above given is the general relation between the payload per trip to the cost of removal of OB.

8.0 What may go wrong:

Trying to increase the payload per trip of the dumper, a number of problems may arise. They are:

Tire Failure

Suspension failure

Excessive Spillage

Machine frame damage

Increase of Cycle time

Decrease of Speed

Increase of Fuel consumption with low efficiency, etc.

We try to assess the some real time factors in the following advancements.

Fig 3:- Payload of RD vs Cost of OB removal

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9.0 Effect of Load on Tires:

It is evident that the load carried by the tires directly affects the life of the tires and its performance.

Any overload situation will cause major damages to the tire which may or may not be reused. Following

damages might occur in any overload situation:

Ply separation

Cord and Bead damage

Uneven wear

Cut and Impact damages

Excessive heat generation

Centre wear out

So it is necessary to study the effects of load and other relative parameters on the tire.

9.1 Tire damages in FY 11:

We analyze the number of tires discarded due to different reasons in FY 1, which shows that the number of

tire cuts beyond point of repair has drastically increased. A further study in this will in the current months

will give us a proper picture.

Fig 4:- Tire failures in FY11

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Now, we try to analyze the number of tires cut/damaged beyond point of repair in FY11 and the current

months, where there has been a significant increase of load per trip carried by the Dumpers.

So we see that in APR‟11 and MAY‟11, where there was an increase of average load per trip carried by the

RD, the number of tire cuts went up by 1100%.

05

101520253035

Ap

r/1

0

May

/10

Jun

/10

Jul/

10

Au

g/1

0

Sep

/10

Oct

/10

No

v/1

0

Dec

/10

Jan

/11

Feb

/11

Mar

/11

Ap

r/1

1

May

/11

No

of

Tire

fai

lure

Radial Tires

Rainy Season

Fig 5:- Number of tire failures in FY11

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9.2 Overloading affects life of tires:

The effect of overload adversely affects the life of tires. Any overload can enhance the rate of damages

caused to the tire and hence bring about a significant decrease in the expected run hours of the tire. Adjoining

is given a comparison of the overload percent to the change in tire life to the corresponding overload.

Here we see that

overloading the tire reduces the

expected run hours of the tires and

proper loading will ensure that the

expected run hours are met with.

But the case may arise in

overloading, that there might be an

increase of Maintenance costs, but

simultaneously, the excess payload

that the dumper carries may

increase revenues in terms on cost

of OB removal / mt3

Fig 6:- Change in tire life vs Load on tire

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10.0 Factors relating load carried by the dumper to tires:

There are a few factors which relates load carried by the dumper with the tire. They are:

Ton Kilometre Per Hour Rating (tkph factor of a tire): The tkph factor should be less than the rated

factor to ensure proper conditions.

Inflation Pressure of the tire: The pressure to which the tire is inflated is in direct relation with its

load bearing capacity.

Gradient of the haul road: Uphill climb always adds excess weight on to the rear tires, and down hill

haul in case of in pit dumping does the same to the front tires.

Shift of c.g. at turns in the haul road: There is a slight shift of cg due to turning at haul roads although

proper super elevation helps in reducing the effect.

10.1 Tons Kilometer Per Hour (TKPH):

Heavy duty haulage causes heat development in tires. As the tires have limited resistance to heat, detoriation

of the tyre may begin at a very early stage of operation due to excess heat development. Hence, it is

necessary to determine the amount of work that will keep the tires within a safe range to avoid overheating

when the vehicle is operated under the given conditions and within the safe range can be determined as

below:

TKPH = mean tyre load * average work day speed

Mean tyre load = (empty tyre load + loaded tyre load)/2

Average work day speed = 𝑅𝑜𝑢𝑛𝑑 𝑡𝑟𝑖𝑝 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 ∗ 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑦𝑐𝑙𝑒𝑠 𝑝𝑒𝑟 𝑑𝑎𝑦

𝑇𝑜𝑡𝑎𝑙 ℎ𝑜𝑢𝑟𝑠 𝑜𝑓 𝑜𝑝𝑒𝑟𝑎𝑡𝑖𝑜𝑛 𝑝𝑒𝑟 𝑑𝑎𝑦

There must be a limit, both in load and haul distance, whereby the TKPH formulae will no longer apply,

Tires loaded at 20% above then rated capacity or used in haul roads of more than 25km will not qualify for TKPH calculation.

The following graph gives us an idea of the separation damages that can be caused due to increased

temperatures caused by high TKPH values.

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Let us consider a sample tkph calculation with real time data:

Dumper is RD 115

Dated April 21, 2011

Round trip distance = 3.81 *2 kms = 7.62 kms.

No of cycles= 17

Hours of operation = 05:32 hrs. to 14:54 hrs. = 9.5 hrs.

Average work day speed = (7.62*17)/9.5 = 13.635. .

Front Tires Rear Tires

Load on tire when the dumper is empty = 11.88 T

Load on tire when the dumper is loaded = 5.496 T

So, mean tire load = (11.88+25.496)/2 = 18.688 T

So, TKPH = 18.688 * 13.635

TKPH = 254.81



So, mean tire load = (12.06 + 25.85)/2 = 18.955 T

So, TKPH = 18.955 * 13.635

TKPH = 258.45

(safe operational TKPH values = 423)

TKPH Value calculation Neglecting Idle time, assuming the dumper was in operation for the whole time

continuously

Fig 7:- % Separation damage at different temperatures

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Dumper is RD 101

Dated 1-2-2011 to 14-2-2011

No of cycles= 576

Round Trip Distance= (1241.9 + 1420)/576 = 4.621 Kms

Hours of operation = 55.961 + 55.0565 = 121.0175 Hrs (only considering empty and loaded dumper travel

time)

Average work day speed = (4.621*576)/121.0175 = 21.9943

Total Load = 44060.544 T

Average Load/Trip = 76.494 T

Front Tires Rear Tires



So, mean tire load = (11.88+24.58)/2 = 18.23 T

So, TKPH = 18.688 * 21.9943 = 411.02

TKPH = 411.02



So, mean tire load = (12.06 + 24.95)/2 = 18.505 T

So, TKPH = 18.505 * 21.9943 = 407.00

TKPH = 407.00

Below is an extract of TKPH MAR'11.xlsx where instantaneous TKPH calculations are shown

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Load Emp

ty

Emp

ty

Load

ed

Loa

ded

Loade

d

Loaded

Dumper

Empty

Dumper

Mean tire

weight

Workday

Speed

TKPH Weig

ht

Trav

el

Trav

el

Trav

el

Trav

el

Dump

er Front Rear

Fron

t Rear front rear

Tim

e Dist. Time

Dist

. weight Tire Tire Tire Tire Tire Tire Front Rear

(tonn

e)

(min

) (km) (min)

(km

) T T T T T T T Tire Tire

79.5 5.38 2.1 12.4 5.3 153 25.24

5

25.627

5

17.2

7

9.73

8

21.257

5

17.682

75

24.9718785

2

530.8

3

441.5

7

82.3 7 2.2 13.2

8 5.1 155.8

25.70

7

26.096

5

17.2

7

9.73

8

21.488

5

17.917

25

21.5976331

4

464.1

0

386.9

7

85.9 11.0

2 5.1

13.2

3 5.1 159.4

26.30

1

26.699

5

17.2

7

9.73

8

21.785

5

18.218

75 25.2371134

549.8

0

459.7

8

78.9 10.6

5 5.1

13.0

3 5.1 152.4

25.14

6 25.527

17.2

7

9.73

8 21.208

17.632

5

25.8445945

9

548.1

1

455.7

0

83 11.2

2 5.1 2.8 0.6 156.5

25.82

25

26.213

75

17.2

7

9.73

8

21.546

25

17.975

88

24.3937232

5

525.5

9

438.4

9

71.2 2.65 0.6 12.9

3 5.3 144.7

23.87

55

24.237

25

17.2

7

9.73

8

20.572

75

16.987

63

22.7214377

4

467.4

4

385.9

8

86.2 12.0

7 5 14.7 5.9 159.7

26.35

05

26.749

75

17.2

7

9.73

8

21.810

25

18.243

88

24.4303324

6

532.8

3

445.7

0

81.4 5.38 1.6 12.1

2 5.3 154.9

25.55

85

25.945

75

17.2

7

9.73

8

21.414

25

17.841

88

23.6571428

6 506.6

422.0

8

69.7 8.17 4.5 10.2

5 4.5 143.2

23.62

8 23.986

17.2

7

9.73

8 20.449 16.862

29.3159609

1

599.4

8

494.3

2

85.6 8.92 4.5 10.5

7 4.6 159.1

26.25

15

26.649

25

17.2

7

9.73

8

21.760

75

18.193

63

28.0143663

4

609.6

1

509.6

8

92.2 8.63 4.5 11.1

2 4.6 165.7

27.34

05

27.754

75

17.2

7

9.73

8

22.305

25

18.746

38

27.6455696

2

616.6

4

518.2

5

48.3 5.67 2.1 6.82 2.2 121.8 20.09

7

20.401

5

17.2

7

9.73

8

18.683

5

15.069

75

20.6565252

2

385.9

3

311.2

887

49 6.47 2.2 7.37 2.4 122.5 20.21

25

20.518

75

17.2

7

9.73

8

18.741

25

15.128

38

19.9421965

3

373.7

4

301.6

93

52.2 7.88 2.2 7.65 2.4 125.7 20.74

05

21.054

75

17.2

7

9.73

8

19.005

25

15.396

38

17.7720540

9

337.7

6

273.6

2

93.6 6.33 2.2 8.05 2.4 167.1 27.57

15

27.989

25

17.2

7

9.73

8

22.420

75

18.863

63

19.1933240

6

430.3

2

362.0

5

90.6 7.1 2.1 7.15 2.4 164.1 27.07

65

27.486

75

17.2

7

9.73

8

22.173

25

18.612

38

18.9473684

2

420.1

2

352.6

5

47.1 9.73 2.4 8.68 2.6 120.6 19.89

9

20.200

5

17.2

7

9.73

8

18.584

5

14.969

25

16.2954915

8

302.8

4

243.9

3

60 8.42 2.2 7.98 2.6 133.5 22.02

75

22.361

25

17.2

7

9.73

8

19.648

75

16.049

63

17.5609756

1

345.0

5

281.8

4

44.8 7.73 2.2 7.5 2.6 118.3 19.51 19.815 17.2 9.73 18.394 14.776 18.9100459 347.8 279.4

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95 25 7 8 75 63 6 4 2

52.3 8.8 2.4 8.3 2.6 125.8 20.75

7

21.071

5

17.2

7

9.73

8

19.013

5

15.404

75

17.5438596

5

333.5

7

270.2

5

40.7 8.42 2.4 7.32 2.6 114.2 18.84

3

19.128

5

17.2

7

9.73

8

18.056

5

14.433

25

19.0597204

6

344.1

5

275.0

9

45.7 8 2.4 7.3 2.4 119.2 19.66

8 19.966

17.2

7

9.73

8 18.469 14.852

18.8235294

1

347.6

5

279.5

6

52.5 8.12 2.4 8.38 2.4 126 20.79 21.105 17.2

7

9.73

8 19.03

15.421

5

17.4545454

5

332.1

6

269.1

7

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10.2 Inflation Pressure of the Tires:

The load carrying capacity of a tire is directly related to its inflation pressure. The adjoining graph gives the

relation between inflation pressure of the tire (Radial 27.00 R 49 and Bias 27.0049) and load carrying

capacity.

The dumpers in the mine use two types of tire combinations:

1) Front and Rear Radial tires (2 in the front 4 in the back)

2) Front Radial and Rear Bias tires (2 Radial in the front 4 Bias in the back)

10.2.1 Current status of tires in the mine:

Front radial rear bias:

The Radial tires (27.00R49) are inflated to a 100 psi and the Bias tires (27.0049) are inflated to 85 psi

Load capacity of radial tires= 27100kgs/tire

Load capacity of bias tires= 25300kgs/tire

So the load capacity of the tires=

27100*2 + 25300*4 = 155.4 T.

Chassis + Body + Tyre weight = 50610+15875+7000 = 73.485 T

So the payload that the tire can carry is 155.4-73.485 = 82 T

Now due to operational conditions there is an increase in temperature and hence the internal pressure. This

normally increases the pressure in the range of 7 to 15 psi. This facilitates extra load to be accommodated

and the payload reaches a limit of:

[27100 + 27100*0.05]*2 + [25300 + 25300*0.05]*4= 163.17 (since for every percent increase of load the psi

increases by 2%, here taking average increase of 10%)

Hence the payload = 163.17 – 73.485 T= 89.685 T

Fig 8(a,b) :- Load Capacity of Tires at different pressures (Radial Tires, Bias Tires)

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Effect of gradient:

An increase of gradient uphill also causes increase of load on the rear tires of the dumper

The gradient of the haul road is at an average 1 in 14 to 1 in 16, i.e. 7% gradient.

So the excess load on the rear tires will be also increased to 7% of the original load.

The increase of load = 0.667 * 163.17 * .07 = 7 T

Hence, the optimum payload based on this factor should be: 89.685 – 7 = 82.685 T

Turning at haul roads:

Height of CG = 2.86 mt

Distance of CG form either end = 1.788 mt

Ra and Rb are the reaction forces acting on the tires on the 2 sides

The weight of the dumper (loaded) = 163.17 T

There is centrifugal force acting on the sides of the dumper during turn

Radius of turn in haul roads = 15 mts

Speed of the dumper at the turns = 7kmph = 1.944T

163170 ∗1.9442

15*2.80 + Rb*3.576 – 163170 * 9.81 *

3.576

2 = 0

or, Rb = 767344.3

We know Ra + Rb = m*g = 1600700 N

So, Ra = 833355.6

Now under normal circumstances, Ra‟ = m*g/2 = 800348 N

So difference in forces on the tyre when the tyre is in a turns and when the tyre is in linear motion =

Fig 9:- FBD of a Dumper

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Ra‟-Ra = 33007 N

So equivalent mass = 33007/9.81 = 3.36 T

So we have to reduce a mass of 3.36 T from the payload considering shift of CG due to turning at haul roads.

But we have already reduced 7T considering the gradient of haul roads and the turns are made at a level, so

the optimum load will be: 82.685 T

The mine conditions are such that the turns at haul roads are not in accordance with the DPR, with a 7%

incline at turns, the optimum load = 82.685-3.36 = 79.325

Case Of In Pit Dumping:

When the dumping of the overburden is In Pit, then the loaded dump truck will be hauling in down

gradient.

This creates an excess load on the tires on the front side, which is proportional to the gradient of the haul

road

The weight on the rear axel = 0.33 * 165 T = 54.45 T

Gradient of haul road = 7%

So increase of load on the front axel = 0.07 * 54.45 T = 3.8 T

So the effective increase of load on each tire = 1.9 T

So the optimum load for a dumper subjected to in pit dumping is= 89.685 – 3.8 = 85.885 T

If turns at haul roads are considered, optimum load = 85.885-3.36 =82.52 T

Front and rear radial tires:

The radial tires used in this case is also 27.00R49

They are inflated at a pressure of 100 psi

The load carrying capacity of tyre inflated at 100 psi = 27100 kgs

So the total load carrying capacity = 162.6 T

Due to 10% increase of internal pressure, the lad carrying capacity increases by 5%

Hence, the load capacity of the tyre = 162.6 + 162.6*0.05 = 171 T

Chassis + Body + Tyre weight = 50610+15875+8208 = 74.7 T

So the payload that the tire can carry is 171 – 74.7 = 96.3 T

Effect of gradient:

The gradient of the haul road is at an average 1 in 14 to 1 in 16, i.e. 7% gradient.

So the excess load on the rear tires will be also increased to 7% of the original load. The increase of load =

0.667 * 171 * .07 = 8T

N. B.:-The calculations for the other sets of tires are derived at and the calculation is not shown.

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So, based on these factors the optimum payload = 96.3 – 8 = 88.3 T

Effect of turns

Considering turns at haul road, the reduced optimum load = 88.3 – 3.52 = 84.78 T

Case of In pit dumping

The optimum load for in pit dumping will be = 96.3 – (171*.33*.07) = 92.35 T

And considering turns, the load = 92.35 – 3.52 = 88.83 T will be optimum load.

11.0 Optimization of load capacity

From the scenario considering load capacity of the tires it is clear that the tires are facing overload situation.

So we look at a solution as below.

We know that the maximum inflation pressure for Radial Tires is 120 psi and Bias tires have a safe range of

up to 100 psi.

Considering increase of internal pressure of the tires, the tires can be inflated to a maximum of 110 psi for

Radial and 90 for Bias.

These inflation pressures would ensure that the tires carrying load have enough capacity to bear the load,

which would have been overloaded otherwise.

Front radial rear bias tires:

Load capacity of the radial tires at 110 psi = 28318 kgs

Load capacity of the bias tires at 90 psi = 26044 kgs

Hence the total load bearing capacity of the tires = 26044 * 4 + 28318 * 2 = 160.812 T

Chassis + Body + Tyre weight = 50610+15875+7000 73.485 T

Hence payload the tyre is capable to carry = 87.327 T

Normally there is increase of temperature under working conditions. This results in increase of internal

pressure to about 10%. This facilitates an increase of load bearing capacity to 5%

Hence the load capacity of the tires is increased to = (28318.62+28318.62*0.05)*2 + (26044+26044*0.05)*4

= 59469 + 1093884 = 169 T

Hence the payload capacity of the tires = 95 T

Gradient of haul roads:

There is a 7% gradient of haul roads at an average. This gradient results in 7% increase of load on the rear

tires = 169 * 0.66 * 0.07 = 7.8 T

So, dumper with the tyre specification can carry an optimum load of = 95 – 7.8 = 87.2 T

Turns in haul roads:

Considering turns at haul roads, 87.2 – 3.49 = 83.71 T should be the optimum load

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Inpit dumping:

The load that can be carried down gradient for in pit dumping = 95 – 3.9 = 91.1 T

And if we consider the turns at haul roads, the optimum load = 91.1 – 3.9 = 87.2 T

Front and rear radial tires:

Load capacity of radial tires at 110 psi = 28318.62 kgs

Hence the load that the tires can carry = 28318.62 * 6 = 170 T

Chassis + body + tyre weight = 50610+15875+8208 74.7 T

So the payload that can be hauled = 95.3 T

Considering a 10% increase of internal pressure due to increase of temperature under working conditions

there is a 5 % increase of load capacity.

So load bearing capacity of the tires = (28318.62 + 28318.62 * 0.05) * 6 = 178.407 T

Hence the payload the tires will be able to bear = 103.707 T

Gradient of haul roads:

There is a 7% gradient of haul roads at an average. This gradient results in 7% increase of load on the rear

tires =178.407 * 0.66 * 0.07 = 8.2 t

Hence, optimum load that the dumper with the tyre specification can carry = 103.707 – 8.2 = 95.5 T

Turns at haul roads:

If the turns at haul roads are considered, the optimum load = 95.5 – 3.84 = 91.66 T

In pit dumps:

The optimum load that can be carried down gradient will be :

103.707 – (178.4 * 0.33 * 0.07) = 99.57 T

Considering turns at haul roads, optimum load = 99.57 – 3.84 = 95.73 T

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12.0 Volumetric Analysis of Dump Body:

XI OB X OB IX OB VIII OB VII OB VIOB V OB

Heaped volume

(SAE 2:1) =

60.1 mt3

Swell factor =

1.4

Fill factor = 0.8

Density

(T/cu

mt) 2.215 2.38 2.385 1.975 2.6 2.52 2.55

Tonnage

(T) 76.06 81.729 81.9 67.82 89.28 86.54 87.57

Tonnage subjected to change in swell factor, different seams have different swell factors.

Any increase of load from the given tonnage of the seams will result in spillage and loss of material.

Limiting the load per trip to the above limits will result in minimal spillage and better haul road conditions.

Considering dimensions of the dump body of the

dumper, we calculate tonnage for different seams

that can be carried with a 2:1 heap volume in

accordance with SAE.

Fig 10:- Dump Body of a Dumper

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13.0 Diesel Consumption Analysis:

Here we assess the diesel consumption of the dumper.

We see that there is an increase of overall diesel consumption and it bears a statistical relation with the

corresponding changes of load per trip of the rear dumper

.

Fig 11 :- Load per Trip vs Total diesel consumption in FY 11

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The above and below analysis, compares the Load Per Trip against Rate of Diesel Consumption.

The above graph compares data derived from the ECM module present in the dump truck, and the Graph

below compares the same, derived from the KPI data table of the FY 11

Fig 12:- Avg Load per Trip vs Fuel Consumption in lt/hr over 2 months

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Analysing, the data we find that there has been increase of fuel consumption corresponding to the increase of

load. This result is evident for both Total Diesel Consumption and Rate of Diesel consumption. This gives us

the general idea of the relation of Diesel Consumption with corresponding changes of Load per trip of the

Rear Discharge Dumper.

Fig 13:- Load per Trip and Lt. of Diesel consumed/ Hr in FY’ 11

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14.0 Speed Analysis:

The following plots are the results of the analysis of Speed of the dumper vs Payload of the dumper

On analysing this set of data, we find that the data set is spread over Two distinct region.

So for further analysis, the speed vs. load plot has been divided on the basis of lead distance which is lower

in case of In Pit Dumping and more in Out Pit Dumping. This gives us a clear idea of the scatter area formed

by the parameters.

14.1 Out Pit Haul:

Analysing the data set for the speed vs payload graph for out pit dumping, the trend does not quite give us a

clear idea of the nature of variation as R2< 0.1.

Fig 14:- Speed vs Load plot

Fig 15:- Speed vs Load plot in Outpit haul

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14.2 In Pit Haul:

In the case of In Pit dumping, the R2<0.1 and there is no certain trend that can be assumed.

So it can be concluded that the relation of Average Speed to the Load carried by the dumper is independent

of each other, considering no other factors influencing it.

Fig 16:- Speed vs Load plot in Inpit haul

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15.0 Recommendation:

Based on the study as above, the maximum limiting factors are as in Table 1. And table 2 shows the

maximum load that the dumper will be subjected to based upon the above factors (also colour coded)

Tire Capacity

OB

Density of

OB

Dump body

capacity Uphill Haul Downhill Haul

2R-4B 6R 2R-4B 6R T / cu mt 2:1 Heap filling

(T)

79.325 T 84.78 T 82.52 T 88.83 T XI OB 2.215 76.0631

X OB 2.38 81.7292

(present) (present) (present) (present) IX OB 2.385 81.9009

83.71 T 91.66 T 87.2 T 95.73 T

VIII OB 1.975 67.8215

VII OB 2.6 89.284

VI OB 2.52 86.5368

Optimized Optimized Optimized Optimized V OB 2.55 87.567

OB

Recommended optimum load Optimum load (present conditions)

Uphill Haul Downhill Haul Uphill Haul Downhill Haul

2R-4B 6R 2R-4B 6R 2R-4B 6R 2R-4B 6R

XI OB 76.0631 T 76.0631 T 76.0631 T 76.0631 T 76.0631 T 76.0631 T 76.0631 T 76.0631 T

X OB 81.7292 T 81.7292 T 81.7292 T 81.7292 T 79.325 T 81.7292 T 81.7292 T 81.7292 T

IX OB 81.9009 T 81.9009 T 81.9009 T 81.9009 T 79.325 T 81.9009 T 81.9009 T 81.9009 T

VIII OB 67.8215 T 67.8215 T 67.8215 T 67.8215 T 67.8215 T 67.8215 T 67.8215 T 67.8215 T

VII OB 83.71 T 89.284 T 87.2 T 89.284 T 79.325 T 84.78 T 82.52 T 88.83 T

VI OB 83.71 T 86.5368 T 86.5368 T 86.5368 T 79.325 T 84.78 T 82.52 T 88.83 T

V OB 83.71 T 87.567 T 87.2 T 87.567 T 79.325 T 84.78 T 82.52 T 88.83 T

The recommended inflation pressure for Radial tire = 110 psi and Bias tire = 90 psi. The optimized factors as

given in Table 1 are based on the above inflation pressures.

Present pressures of Radial tires = 100 psi and Bias tires = 85 psi. If the mine working is continued on the

present inflation pressures then the load per trip of a dumper will be as subjected in the Present Conditions

column.

Swell Factor of blasted OB = 1.4 Fill Factor of Dump body = 0.8, Heaped Volume (2:1) = 60.1 cu.mt

Table 1: Dictating Factors

Table 2: Optimized Conditions

Optimization of Load Per Trip of a Rear Discharge Dumper

Technology

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