Materials Handling and Hoisting
1. Consider a 20 tonne mine locomotive travelling at 15 km/hour. Determine the retarding forceof the brakes required to stop it in 40m on a level track.
2. If a surface haulage truck accelerates at a uniform rate of 0.7 m/s2 from rest, what will be its velocity after 20 seconds?
3. A shuttle car travels at an average velocity of 1.5 m/s from a loading machine to a conveyor belt where it will discharge its payload. If the travel time =80 sec, what will be the distance between the loading point and the dump?
4. Locomotives of this type are the heaviest of those used anywhere in the mine. A mine utilises a 55 tonne locomotive. On clean dry rails the adhesion factor =0.2 for braking. In these circumstances what is the tractive e_ort in kg?
5. For the locomotive in Q.4: if the locomotive resistance =15 kg/tonne determine the drawbar pull.
6. An evacuation hoist is to be installed for an underground coal mine. The vertical hoist will evacuate 6 miners at one time every 4 minutes. The depth of the overburden is 165.5m.
Determine if a 0.625 in 6_19 haulage rope would be adequate for this application?
The following may be assumed:
(a) escape capsule weigh =902.5 kg
(b) total weight of the miners is 690 kg
(c) the maximum rope velocity is 1.520 m/s
(d) For the rope the weight per metre of rope =0.1 kg/m
(e) minimum factor of safety for man riding =9
(f) breaking strength =11280 kg.
7. A vertical hoist is to be designed to haul ore at a rate of 500 tonnes/hour, from a depth of 400m, at an average skip velocity of 6.3 m/s. Determine the required skip load in tonnes.
8. Design a double drum hoist for a 460.5m (_1510ft.) vertical shaft based on the following conditions:
(a) Balanced operation
(b) Weight of load = 5.75 long ton (5.844 tonne)
(c) Weight of skip = 8.25 long ton (8.382 tonne)
(d) Desired capacity = 400 tph (406.4 tonnes/hr)
(e) Acceleration time = 10 sec
(f) Deceleration time = 10 sec
(g) Rest time per trip = 8 sec
(h) E_ciency = 0.85 %
(i) An induction motor is to be used
(j) A round strand rope is to be used.
9. For the system in Q.8 what would be the rmsHP for the hoist be if a self ventilated DC motor were used?
10. (a) For a hoisting system with a 3-period Trapezoidal speed time diagram determine the hoisting capacity of a shaft if the skip payload =25tonnes, hoisting distance =930m, maximum rope speed =10m/s, acceleration and deceleration are 2m/s2 and the rest time between winds =10sec.
(b) For the following winding conditions determine if a rope with a minimum breaking force of 2 MN gives a satisfactory factor of safety for the winding of ore?
i. Depth of wind = 450m
ii. Mass of skip and attachments = 7tonne
iii. Mass of ore wound per wind = 10tonne
iv. Height of sheaves above skip top when skip unloading at shaft top = 20m
v. Mass of rope/100m = 750kg/100m
(c) If the maximum winding speed for the wind described in (b) is 15m/s and acceleration = deceleration = 2m/s2 (assume linear change of speed during acceleration and deceleration) determine:
i. Accelerating period
ii. Decelerating period
iii. Distance travelled by skip in accelerating period
iv. Distance travelled by skip during decelerating period
v. Time travelling at maximum speed
vi. Distance travelled at maximum speed.
vii. Total cycle time assuming a 10 s rest period between winds
viii. Number of cycles per hour
ix. Capacity of the system per hour
11. A 60-tonne locomotive is used to haul coal from a loading sidetrack to an unloading centre2000m distant. The trips are designed to accelerate at a rate of 0.23 kphps up a 2% grade.
If 10 tonne capacity cars with a tare weight of 5 tonnes are used. Determine the number of locomotives required to haul a shift tonnage of 6500 tonnes. It can be assumed that the locomotives average a speed of 16 kph with a 5 minute turnaround at each end. Roller bearings are used throughout and an adhesive factor of 25% is to be used. Operating time per shift =6 hours.
12. Determine the size of locomotive required to pull a 400 tonne train from a level siding at a maximum acceleration of 0.4 kphps if anti-friction bearings with an F=0.1kg/tonne are used on all equipment. An adhesive factor=25% should be used.
13. For the locomotive in Q.12: determine the maximum grade against which the locomotive can pull the train without decelerating, using the same adhesive factor.
14. For the situation in Q.13: if the adhesive factor is 35% what is the maximum grade the locomotive can pull the train without decelerating?
15. Design a conveyor belt to haul coal, density 1950 kg/loose m3, 1500m on the level in an underground mine. Peak capacity is to be 2500 tonne/hr, the advised belt speed =3 m/s. Assume that the drive has automatic take-up, lagged pulley and a 270_ arc of contact. Motor drivee_ciency =0.83.
16. Design a conveyor belt for the same situation as in Q.15, except the belt is hauling the coal up a 10_ slope.
17. Two 5 tonne shuttle cars operate at an average speed of 1.5m/s during the development phase of a panel. The loading machine has a rate of 2.5t/min.
Loader/ change out distance =30m. If each shuttle car incurs a wait at the change out point of 0.5min and the shuttle car discharge time =0.45 min what is the haul distance from the change out point to the dumping point?
18. Estimate the cycle time and production of a 70 tonne GVW off highway truck with 40 tonnes on its rear wheels when loaded to its rated capacity, operating on a level haul road of 2000m length. The road is a rutted dirt roadway with no maintenance and no stabilisation, tyre penetration is 12.5 cm. The following can be assumed:
(a) Loading time =1.5 min
(b) Manoeuvre and dump time =0.8 min
(c) Truck hauls 40 tonnes of ore each trip
(d) Job efficiency =0.8
19. For the situation in Q.20, determine the cycle time if road conditions were improved to a rolling resistance of 30 kg/tonne.
20. For the problem in Q.19 the engineer at the site is considering the use of a shorter, 1050 m haul road that has a slope of 6% adverse. If all other factors remain the same which haul route should be selected on the basis of shortest cycle times? What are the cycle times and hourly productions?
21. What is the difference between a drum hoist winding system and a Koepe winding system? What factors inuence the application of each system?
22. For a standard load haul dump situation drawing ore from an open stope and dumping to an ore pass, describe the factors that make up the cycle time for the unit. Also to achieve a desired production rate detail the method you would use to select the required bucket size and number of units to be used.
23. Describe in detail one method of arresting a cage in an emergency situation in a shaft.
24. What guide arrangements can be employed in a shaft winding system and why are guiding systems required? Describe one method of guiding in greater detail.
25. Detail the main components of a belt conveyor system. With respect to such systems what is meant by the terms transfer point and tandem operation.
26. A shaft winding system is made up of a number of principal components, list each of these.
27. An off highway truck weighs 25 t empty and carts a payload of 35 t up an 8% grade. The RRfactor is 40 kg/tonne. Calculate:
(a) The total resistance in kg
(b) The effective grade in %
28. A 50 t rubber-tyred scraper is towed by a crawler tractor weighing 40t up a 5% grade. The
RR factor is 50kg/t. Calculate:
(a) The rolling resistance in kg
(b) The grade resistance in kg
(c) The total resistance in kg
29. A Caterpillar D30D articulated dump truck has the rim pull curve in Figure 1. (Gross weight 21.9 t empty, 49.117 t loaded). If the truck ascends a 5% grade with a rolling resistance of 50kg/t, _nd the following: a) Total resistance in kg) b) The required rim pull in kg when loaded
c) The maximum speed of the truck when loaded in km/h
30. The average speed of an 20m3 scraper is 40 km/hr and its return speed uphill is 20 km/hr over a 400 m haul distance and a 450 m return distance. Using a _xed time of 5 minutes, calculate the cycle time in minutes.
31. A Caterpillar 631E tractor scraper has the following characteristics:
Figure 1: CAT D30D gradeability (in Caterpillar Performance Handbook version 31 (2000).
(a) Maximum heaped volume = 19.6 Bm3
(b) Maximum payload = 34,000 kg
(c) The material hauled is earth with a density of 1825 kg/Bm3
Rolling resistance is 30 kg/t and operating conditions are average with a job e_ciency of 50
min/hour. The haul route comprises of the following sections:
_ Section 1 (100 m) level-loading zone
_ Section 2 (80 0m) 5% down grade
_ Section 3 (100 m) level dumping zone
_ Section 4 (1 km) 6% up grade
_ Section 5 (90 m) level turnaround area.
Estimate the machines production under these conditions using the travel time curves given in
Figures 2,3,4 and 5.
32. What is meant by line of sight operation of automated equipment?
Figure 2: Speed gradebility for wheel scrapers: total resistance vs. gross weight
Figure 3: Retarding for wheel scrapers: e_ective grade vs. gross weight
Figure 4: Travel time for wheel scrapers: time vs. total resistance
Figure 5: Travel time (empty) for wheel scrapers: time vs. total resistance