MHD721S - Materials Handling 324 - 1st Opp - Nov 2022 :: NUST past examination papers between 2020 and 2024

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MHD721S - Materials Handling 324 - 1st Opp - Nov 2022

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2 Pages 11-20

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MHD721S - Materials Handling 324 - 1st Opp - Nov 2022

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nAm I BI A u n IVE RS ITV

OF SCIEnCE Ano TECHnOLOGY

FACULTYOF ENGINEERINGAND BUILTENVIRONMENT

DEPARTMENT OF CIVIL, MINING AND PROCESSENGINEERING

QUALIFICATION: BACHELOR OF MINING ENGINEERING

QUALIFICATION CODE: 08BMIN

LEVEL: 7

COURSE CODE: MHD721S

COURSE NAME: MATERIALS HANDLING 324

SESSION: NOVEMBER 2022

DURATION: 3 HOURS

PAPER: THEORY

MARKS: 100

EXAMINER(S)

MODERATOR:

FIRSTOPPORTUNITYQUESTION PAPER

Mr H.K Hengari

Mr L. Madziwa

INSTRUCTIONS

1. Answer all questions.

2. Read all the questions carefully before answering.

3. Marks for each question are indicated at the end of each question.

4. Please ensure that your writing is legible, neat and presentable.

PERMISSIBLEMATERIALS

1. Examination paper.

2. Calculator and appropriate stationery

THIS QUESTION PAPER CONSISTS OF 8 PAGES (Including this front page)

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Question 1 [15 marks]

Acquiring equipment for a specific mining operation is one of the major concerns of mine

planning. Equipment can be bought, rented, or leased.

a) State five (4) advantages of buying machinery over the other methods of

procurement. (4 marks)

b) Consider a dozer with an ownership cost of N$ 238.20 per hour. Cost is based on

assumption that the machine will work 2400 hours each year of its service life.

Checking with a local rental company, the mine receives rental quotes of N$ 40 000

per month {168 hrs), N$15 600 per week (40 hrs), and N$ 5000 per day (9 hrs). What

are the breakeven working hours for all four options? {16 marks)

Question 2 [20 marks]

A 15.8 m3 shovel is used to load poorly blasted rock (1.65 t/m 3, bucket fill =0.85). Consider

loading a CAT 777D truck, with a heaped volume of 60.1 m3 and a maximum payload of 90.4

tonnes. The shovel bucket swing cycle time is 49 seconds. Dump time is 1.2 minutes. The

haul distance is 7.7 km from the face to the dumping point. The ramp is 1.3 km, with a

gradient of 10%. The rolling resistance of the haul road will be maintained at 5%. Both

machines operate on a 50 min/hr efficiency.

a) How many buckets are needed to fill the truck? Perform a gravimetric check on the

number of buckets you select (3 marks)

b) Estimate the cycle time of the truck and the balanced number of trucks (10 marks)

c) What is the overall mine production in tonnes per hour? (3 marks)

d) Discuss two (2) modifications will you make to the truck-shovel operation to increase

production, without changing the size of the units. (4 marks)

Question 3 [20 marks]

Given the following data work out the design parameters of a friction sheave hoist:

Two balanced skips, tower mounted hoist.

Production rate = 500 tonnes/hr

Shaft depth = 600m

Headframe height= 30m

Hoist rope 4 flattened stranded

Skip weight= 13 tonnes

live load =13 tonnes

Hoist speed = 4 m/s

Load time = dump time = 6 sec

Acceleration = retardation = 1.29 m/s 2

Calculate the following:

a) Minimum rope diameter to be used in this operation (5 marks)

b) Rope slippage, if the friction ratio should be below 1.6. (5 marks)

c) Sheave diameter and tread pressure (5 marks)

d) Horsepower to accelerate the suspended load (5 marks)

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Question 4 [20 marks]

A 1200 mm wide conveyor belt is to be designed for coal (SG=0.96) haulage up a 600 m-

long 5° slope. The peak capacity is estimated to be 1,000 tph, and the belt speed will be set

at 3 m/s. The belt drive will have a counterweight, lagged pulley, and a 240° arc of contact.

Due to high production rates, consider heavy-duty operations.

a) Estimate the required tensions on both sides of the belt. (10 marks)

b) If the maximum allowable sag of the belt is 0.02 m, will 1.5 m and 3 m spacing for

the carrying and return idlers be sufficient to support or will additional tensioning be

required (6 marks)

c) Calculate the Allowable tension of the belt to suit this operation (2 marksj

d) If motor drive efficiency is assumed to be 90%, determine the power required. (2

marks)

Question 5 [20 marks]

In an underground mine, water must be pumped from the working. There are 650 m

between the water source to the shaft. From there, there is a vertical height of 590 m. The

mixture of water and solids has a density of 1.36 t/m 3•

a) How many pumps are needed to pump this water if the maximum power rating of

the pump available is 50 kW? The pumping rate is assumed to be 0.05 m3/s. The

piping to be used has a diameter of 139 mm and a friction factor of 0. 0084. All the

coupling and fittings in the system have KL= 6.5. The efficiency ofthe pump is 80%

and the motor that drives it at 84%. (10 marks)

b) What improvements can you suggest for this design? (5 marks)

c) What are the benefits of pit dewatering in mining operations? (5 marks)

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1.7 Page 7

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Te=Ti-Tz

T1+T2

p= NDd

TSL x V2

HP1=

77gta

pgHQ

P=--

Formula Sheet

G-

3. 6V

SF- 25000

4000 +H

. Tmax

Tension=~

P= (1 + 011

EAC=

on) ( 1 - (1:

Te= T2 K

d~ JN(fj~«,H)

TeV

PA=-

flvz

hi=-+KZig-d

TSL = We + W0 + 2Ws

+2WR

Tcmin

l~(mb

mG)g

BP=- LT

Trmin

l';.(mb)g

Truck Load X # of Trucks X TC X jF X p

Te = af Lg{midlers + (Zmb + me) cos o} + Rs + mcgL sin o

C ---

-~--

Operating Conditions

I 'Belt Width

(mm)

Belt Width

(in)

Light Duty

kg/m

Medium Duty Heavy Duty

kg/m

500

600

750

900

1050

1200

I 24

,------

(lb/ft)

4.1 (2.75)

I 5.0 (3.36)

6.2 (4.16)

I 7.4 (4.97)

8.6 (5.78)

9.8 (6.58)

I (!b/ft~-

6.2 (4.16)

I 7.4 (4.97)

9.3 (6.25)

I 11.1(7.46)

13.0(8.73)

14.8 (9.94)

(lb/ft)

10.3 (6.92) I

12.3 (8.26)

~·

iI 15.5 (10.41)

18.5(12.43)

! 21.6(14.51)

24. 7 (16.60)

1350

1500

11.0 (7.39)

12.3 (8.26)

Ir 16.7 (11.22)

18.6 (12.50)

27.8 (18.68)

30.9 (20.76)

1650

1800

I 72

13.5 (9.07)

----14.7 (9,88)

20.5 (13.77) 33.9 (22.78)

I 22.3 c14.98) 37.o (24.86)

-- - -

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Belt Width Belt Width

(mm)

(in)

450

600

750

900

1050

-·

1200

1350

1500

1650

-- 1800

2100

2200

-6-6--·

Mass of Moving Parts (kg/m) (lb/ft)

Light Duty

4" Idlers

Light Belt

Medium

Duty

5" Idlers

Moderate

Belt

Heavy Duty

6" Idlers

Heavy Belt

Extra Heavy

Duty

6" Idlers

Steel Cord

Belt

23 (15.4) 25 (16.8) 33 (22.2)

29 (19.5) 36 (24.2) I 45 (30.2)

49 (33.0)

37 (25.0) 46 (31~

57_(38.3)

63 (42.3)

45 (30.0) 55 (37.0) 70 (47.0)

79 (53.0)

52 (35.0) 64 (43.0) 82 (55.0)

94 (63.2)

63 (42.3)

70 (47.0)

71 (47.7) 95 (63.8)

82 (55.0) 107 (72.0)

·-1 110 (74.0)

127 (85.3)

91 (61.2) 121 (81.3) 143 (96.0)

100 (67.2) 132 (88.7) 160 (107.5)

144 (96.7) 178 (119.6)

·-

168 (112.8) j 205 (137.7)

177 (119.0) 219 (147.2)

ARC OF CONTACT

10...--1

Single pulley

•100

·210

·220

0 230

•240

270

Tandem Pulley

360

390

•420

•440

•450

'180

TABLE 1

STANDARD DRIVE FACTOR "K" VALUES

COUNTERWEIGHT TAKE-UP

Berwputl•Y

µ •0.30

Lllggedpullav

µ•0.35

SCREW TAKE-UP

e,rwpull-v

Far 20% hlgh,r T 1

L9gged pull-v

Far 2°" hlllh•r T 1

0.64

0.50

0.97

0.90

0.50

0.38

0.80

0.66

0.46

0.35

0.76

0.63

0.43

0.32

0.72

0.59

0.40

0.30

0.68

0.56

0.32

0.24

0.58 ----~·

0.49

0.18

0.13

0.42

0.36

0.15

0.11

0.39

0.33

0.13

0.09

0.36

0.31

0.11

0.07

0.34

0.30

0.11

0.07

0.33

0.29

0.09

0.06

0.32

0.29

0.09

0.06

0.31

0.27

• Arc af contact commonly m•t in actual practice

Rapedesign Rope Weight (kg/m)

Round Strand 0.0036d 2

Flat rope

0.004ld 2

Locked coiled 0.0056d 2

0.59d 2

0.63d 2

o.ssd2

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2 Pages 11-20

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100 iLock,gd•' con:drum & Koe(e

__.,/.

90 i

.,,,_,/,.~

.----if'

1._ij

'"5E-,i

7U I

60 !

Rounds!F.nd& llartenedslramJ•KocpeJ

...-,,- ... -

_.,.-..-,,./

I ~'==r= tIl;,-..,,../."..-,-./-

...

Ho1u11S1'ir.n1nd& filaUenIedstrari.d·d.tu1l

·1

-ii

100-0

.200H

31'JDD 40t:HJ·

oepmm_.J. tr ~•

7i:1_,ocm-

i 6MOO~

17tJ.00{t

I 1 6".),(_\\{1(1

- 1- 114000,1.,Q(W[J(CI •.........I....--LS. 'tnugf•i~lereO.:1:r~uuum1..._..

,_ =

~3CUJIKt~I

Ko\\:te;:;,

'- ·-"'- I

"' -~_•,1 I

I '-l

! "- ' B'Jr,1}00

- I

W.000

v- ~- eJ,_ooc, I-

~'),iJO.':•

_J 4fi_!)0{)

~/r r)j•,(10-0

ai,.rn:10

rV- I i w.om:,

n I'--

',,/

/~ ..,.J.

")( I

,•'I'"

[ I ..--r '·-,.J_,...,; /

/,,,-'

b/l

1,.,-'

;,-

V.......-1[.,...,.-.--~---LjM ~·!/I 1

_j______

Drnm di.arneterft-t~ l111eteri

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2.3 Page 13

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2.S

2.0

I.S

, •1

1,05

,.o

Iv.:~

I':

,~,f'-

o._...

r'\\

' t\\.

' !"I

"I'"

20 30 50 100 200

1000

CONVEYORLENGTH(DISTANCEBETWEEN CENTRES J,L

5000m

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• - - - - Typical Field Empty Weight

"• • • •• • • • • 163 360 kg (360,143 lbl Load

kg X

1000

GrossWeight

40 50

100

60 80 100

I I

I I 150 200 kg x 1000

I I II

I 150 200 250 300 400 5001b x 1000

I 111111111

II II

__,,

:a::.:., 5

=:5 3

0.50

0.30

TorqueConverterDrive • • •

Direct Drive

0.5

0 5 10 15 20 25 30 35 40 45 50 mph

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 km/h

SPEED

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