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MHD721S - Materials Handling 324 - 2nd Opp - Nov 2022 |
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n Am I BI A u n IV ERs ITY
OF SCIEnCE Ano TECHn OLOGY
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:
SECONDOPPORTUNITYQUESTION 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
,. - - .. _1_:°HISQUESTION PAPER CONSISTS OF 7 PAGES (Including this front page)
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Question 1 [20marks]
A 800 mm wide conveyor belt is to be designed for coal (SG=0.96 and surcharge angle 15)
haulage up a 600 m-long 10° at 2.8 m/s. The belt is a 3 idlers belt, troughing at 30 degrees
The belt drive will have a counterweight, lagged pulley, and a 240° arc of contact.
a) What is the production of the rate of the conveyor belt? (4 marks)
b) The mine requires 600 t/hr and the opted to increase production by changing the
belt width to 900 mm. Estimate the required tensions on both sides of the belt,
assuming moderate operating conditions Estimate the required tensions on both
sides of the belt. (10 marks)
c) Discuss the consideration for selecting a belt for hauling crushed ore? (6 marks)
Question 2 [20 marks]
a) A mine is considering following three different acquisition methods to obtain a dozer
for. The alternatives are
1 Immediate cash purchase the dozer for N$ 1 682 000 each and sell after 4 years
for an estimated price of N$ 500 000.
2 Purchase the truck using a time payment plan requiring an immediate down
payment of N$ 400 000 and N$ 450 000 at the end of each-year for 3 years.
Assume truck will sold for N$ 500 000 each after 4 years.
3 Lease the dozer for 4 years for N$ 400 000 per year paid in advance at the
beginning of each year. The mine pay all operating and maintenance cost for the
dozer, ownership retains with lessee
If the marginal rate of return is 9.25%, then determine the best choice to buy the trucks (10
marks)
b) Discuss how the mine location and the mining method will affect the choice of
equipment to be used. (10 marks)
Question 3 [20 marks].
Mine water is one of the materials that must be moved in mining operations, where pumps
-- . are.often used to clewater pits and tunnels.
a) D~cuss four (4) _theadvantages of using pumps as a materials handling system? (8
marks)
b) _ In a mine waterlogged workings must be dewatered. The distance from the pit
__. "b()_!:t911s1um1ftg_the dip most face up to which dewatering will have to done _is1200
-·---~m-::-'fhe_-water-level difference between the bottom most point and pit bottom sump-
- - -,,2=a"r2_o:q-'-m~ .-Tlie:"total quantity of water in the lodgment to be pumped out is 12000
kilo lit~rs and t_hepercolation from the strata in 24 hours is 2000 kilo liters. It has _
heen d·ecided to pump out the water in 30 days. Net hours of run of the pump is'2o~·
hours per day. Available pipe is of 150 mm diameter. Coefficient of friction of pipe
range is 0.015. The overall efficiency of pumping set is 75%. Calculate:
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i. Flow rate by the pump in m3/hr (5 marks)
ii. Total head that the pump must overcome. Ignore shock losses {5 marks)
iii. The power of the pump set you. need to install, if the density is 1100 kg/m 3{2
marks)
Question 4 [20 marks]
a) A certain mining operation intends to strip the overburden from a 1.8 m coal seam to
meet a contractual agreement to supply 1 Mt of coal per year. With the given the
following information, determine the limiting depth for this dragline. (5 marks)
Overburden swell: 0.30
Pit width: 20 m
Dumping radius ofthe shovel: 35 m
Tub Diameter: 10 m
Highwall angle of repose: 70°
Spoil angle of repose: 35°
b) A CAT77D truck weighs 64 670 kg empty and 155 070 kg when loaded. This truck has
one front axle {2 tyres) and one rear axles {4 tyres). The axle weight distribution
empty is 47% front and53% rear. The weight distribution loaded is 33% front and
67% rear. The truck works a 8-hr shift hauling blasted material. The one-way haul
distance is 6 km. The truck can make 16 trips per shift. What TKPH rating tyres will be
sufficient for this operation? (10 marks)
c) List five (5) hazards that are associated with loading and hauling operations {5
marks)
Question 5 [20 marks]
Given the following data work out the design parameters of a double drum hoist:
Two balanced skips, tower mounted hoist.
Production rate =400 t/hr
Shaft depth =520 m
Hoist round stranded
Skip weight= 6 tonnes
live load =8.25 tonnes
Load time = dump time= 6 sec
Acceleration =retardation = 10 s
Calculate the following:
a) What is the full speed time for this operation? (5 marks)
b) Minimum rope diameter to be used in this operation (5 marks)
c) Sheave diameter and length (5 marks)
d) What are the advantages of drum hoists in relation to friction hoists? (5 marks)
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-- - =-.-_.-=-;~-
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Rdd- 0. 75Et
P=-- pgHQ
1J
flvz
vz
hi=-+K2ig-d
2g
l.OSd
Formula Sheet
25000
SF= 4000+H
Tensio. n=~ Tmax
s
p = (1 + i)n
EA C = --,---P--i ----,,--...,....
(1- (1;on)
(w ) ] Rd= ---H--;;:+--~lHn1(el r
+ S) + -4tan0
-T
----
-,-----r---------------fl
Operating Conditions
'Belt Width
(mm) Belt Width
(in)
Light Duty
kg/m
(lb/ft)
Medium Duty Heavy Duty
kg/m
kg/m
(lb/ft)
(lb/ft)
500
20
4.1 (2.75) 6.2 (4.16)
600
~-7-50 ___
900
24
3__0__
36
5.0 (3.36) : 7.4 (4.97)
6-.2--(-4.-16--i-) 9.3 (6.25)
! 7.4 (4.97) 11.1 (7.46)
=-~1~0_5-o~-~_._r~~-4-2~~~-:_-~8_.-6-,5--.1-8)-J(183.7.o3)
10.3 (6.92)
II 12.3 (8.26·)-
I 15.5 (10.41) I
18.5 (12.43) I
I I 21.6 (14.51_[
~-12 _0__0___ 4__8__
----~13--5-0-1------; 54
1500
60
--------;-----·------;--------ii•
1650
66
~-1-80_0___ -·-12-·-
9_._8_(_6._58_)_~1J_4_.8_(9_._94_)2-4l1_._(_16_._60_)
11.0 (7.39) j 16.7 (11.22) I 27.8 (18.68)
12.3 (8.26)
13.5 (9.07)
14.7 (9,88)
18.6 (12.50)
20.5 (13.77)
22.3 (14.98)
30.9 (20.76)
33.9 ,22.78) I
37.0 (24.86) ,1
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·-1
Mass of Moving Parts (kg/m) (lb/ft)
Light Duty
Belt Width Belt Width 4" Idlers
(mm)
(in)
Light Belt
Medium
Duty
5" Idlers
Moderate
Belt
Heavy Duty
6" Idlers
Heavy Belt
Extra Heavy
Duty
6" Idlers
Steel Cord
Belt
450
18
23 (15.4) 25 (16.8) 33 (22.2)
600
20
29 (19.5) 36 (24.2) 45 (30.2)
49 (33.0)
750
24
37 (25.0) 46 (31.0) 57 (38.3)
63 (42.3)
- 900
1050
30
45 (30.0) 55 (37.0) 70 (47.0)
79 (53.0)
36
52 (35.0) 64 (43.0) 82 (55.0)
94 (63.2)
1200
42
63 (42.3) 71 (47.7) 95 (63.8) 110 (74.0)
1350
48
70 (47.0) 82 (55.0) 107 (72.0) 127 (85.3)
1500
54
91 (61.2) 121 (81.3) 143 (96.0)
1650
60
100 (67.2) 132 (88.7) 160 (107.5)
I ·-·21180000
66
72
2200
I
I
84
j
·+=144 (96.7)
168 (112.8)
177 (119.0)
- 178 (119.6)
205 (137.7)
219 (147.2)
- -· I
ARC OF CONTACT
10..-1
Single pulley
•,ea
·210
"220
0 230
"240
270
Tandem Pulley
360
390
"420
•440
•450
"460
'180
TABLE 1
STANDARD DRIVE FACTOR "K" VALUES
COUNTERWEIGHT TAKE-UP
Bini putley
µ •0.30
pull..,
j.L•0.35
SCREW TAKE-UP
Bare pulley
For 20%
T1
L9fi9dpulley
For 2°" hlghar T 1
0.64
0.50
0.97
0.50
0.38
0.80
0.46
0.43
0.35
0.32
i
!
0.76
0.72
0.40
0.30
0.68
0.32
0.24
0.58
..
0.18
0.13
0.42
0.15
0.11
0.39
0.13
0.09
0.36
0.11
0.07
0.34
0.11
O.o7
0.33
0.09
0.06
0.32
0.09
0.06
- 0.31
• Arc of contact commonly mat in actual practice
0.9C
0.66
0.63
0.59
0.56
0.49
0.36
0.33
C.31
0.30
0.29
0.29
0.27
Ropedesign
Round Strand 0.0036d2
Flat rope
0.0041d 2
Locked coiled 0.0056d 2
0.59d 2
0.63d 2
0.85d 2
5
-
.
..
•:... •.-=-.';-
-: ... •- .
• L-:- -~--_:•-•L••:
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2 Pages 11-20 |
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I
t I
100 i
I:ilock@d5
;
cotl-' drun1
&.K: -0e',9·
.,,./'
-
I
i
' ri
L.,..-..'.
90 :
I
I
·r0..~.i.3.
8(1'
I
'-O~
0
7() !
'
6:0::
I
-"'"
,-·-<und -~
:strand& tJattenedstrand·Ko:epe
i
I
LI ......_/
--·
..
I
I
I
rjrid ~/
.
I-
I
I
I
Romd sl &flatte~,clStrand-dnr.n, ~1
50 I
I
= 1000
--..J-
I
~t 2(Ji}Ct-
3010:1)
Deptt~:m Bl
=-~
'
1ZOQ
......
C.
1
a,a}
•l'.'i:,
11
•
w
!J.ffi[I
ft,~ IDrnrncii:arnr,:ter Meter-t
I.
J.__.....,. ________
- -··
2
::,;
i!
6
-·--·-·--_._:_.-_. -~ .--- -c--- ---··. ,-- .-- -· -- ----:::--- -------~-
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2.S
I'~
:,~
l'i
2.0
0
••
\\
,.s
r\\
' r\\.
I, I
1,05
,.o
10
'I\\
t\\~
' r-,....,_
20 30
100 200
1000
CONVEYORLENGTHCDISTANCE BETWEENCENTRESJ,L
5000m
Belt
Width
mm
500
650
800
l 000
Surcharge
Angle
oo
100
20°
30°
oo
10°
20°
30°
oo
100
20°
30°
oo
20°
0.009 8
0.014 2
0.018 7
0.023 4
0.018 4
0.026 2
0.034 2
0.042 7
0.027 9
0.040 5
0.053 5
0.067 l
0.047 8
25°
0.012 0
0.016 2
0.020 6
0.025 2
0.022 4
0.029 9
0.037 7
0.045 9
0.034 4
0.046 6
0.059 l
0.072 2
0.058 2
Trough Angle
30°
0.013 9
O.ol80
0.022 2
0.026 6
0.026 0
0.033 2
0.040 6
0.048 4
0.040 2
0.051 8
0.063 8
0.076 3
0.067 7
35°
0.015 7
0.019 6
0.023 6
0.027 8
0.029 4
0.036 2
0.043 3
0.050 7
0.045 4
0.056 4
0.067 8
0.079 8
0.076 3
40°
0.017 3
0.021 0
0.024 7
0.028 7
0.032 2
0.038 6
0.045 3
0.052 3
0.050 0
0.060 3
0.071
0.082 2
0.083 8
45°
0.018 6
0.022 0
0.025 6
0.029 3
0.034 7
0.040 7
0.046 9
0.053 4
0.054 0
0.063 6
0.073 6
0.084 0
0.089 8
7
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