Mine Haulage

Unit 20

Haulage

In this unit, you will learn about mine haulage systems used to transport ore/waste, men, and materials within a mine.

After completing this unit, you should be able to:

List the major types of haulage systemsExplain the purpose of :

Scrapers Slushers Scooptrams Locomotives Ore Cars

Explain the ore circuit in a mineExplain the ore circuit in an open pit

Ore/Waste Handling

• Haulage is the moving of men, supplies, ore and waste.

• In mines of small output, hauling is done on several levels, tonnage handled on each level is small, and light equipment is used.

• In mines of high output, a main haulage level is used and all the ore is dropped to the haulage level via ore

passes.

Early methods of underground haulage included carrying material in sacks, baskets, or other containers, sleds, wheelbarrows, to cars running on a track.

At first ore cars were pushed by hand, later pulled by ponies, and horses

The first electric loco was used in 1882. A gasoline or diesel engine drive may be used instead of electricity

include conveyors, trucks, trains, and Today, haulage methods aerial tramways. Bulk solid transport of solids in

pipelines is used for coal and other materials

Principles of Loading

• After material has been broken, it must be loaded on some type of conveyance system to be removed. The following are the most common methods :

• a) This is a typical person operated shovel. The shovel is pushed into the pile and then lifted. Most mechanical power and hydraulic shovels use this action.

Playing the banjo

• Hand shovelling underground is called "playing the banjo". In general, 1 shoveler can move about 1 ton 100 ft. in 2.5 hours. A shoveler can handle about 17 to 20 tons per shift.


• b) Instead of pushing the shovel into the pile it can be pulled. Most backhoes and draglines use this action.


• c) The clamshell action is often used in shaft sinking. It digs from the top down.


• d) The slusher or scraper bucket is similiar to a garden hose. The bucket is pulled towards the hoist.

Mucking Machine

• i) A mucking machine runs on compressed air and uses the overhead cast type of loading. It is necessary to have an ore car either close or attached to the machine, so the material cast from the bucket will land in the ore car.

Removing Ore from Stope

Slusher

The slusher or scraper system often used in underground loading, Slusher work is divided into 3 main classes:

• for loading cars at the face of drifts, crosscuts, tunnels and stopes, where material transported a short distance and the ore is pulled into an ore car.

• for moving ore from the face to ore cars some distance away.

• for moving ore to chutes or ore passes which lead down to a main haulage level


• e) After a bucket is loaded it has to be hoisted, positioned, and dumped. Most power shovels hoist the bucket and swing to a dumping position


) A conveyor system is often used in coal loading. A gathering lip or pan is mounted on the end of a conveyor belt. The pan or lip has gathering arms or some type of rotating wheel or chain attached to it which gathers, scrapes, or pushes the broken material onto the conveyor belt.


• g) A slusher system is often used underground. Ore is fed to the slusher lane through drawpoints. The material is scraped to the loading point

and loaded by gravity.


• h) A recent development has been the LHD - Load-Haul- Dump unit. This unit loads a large bucket and lifts it a short distance and then carries it to a dump point. Generally these machines are powered with diesel engines and have great flexibility and versatility. Another term for LHD removal is "trackless mining".

Mucking Machine

• i) A mucking machine runs on compressed air and uses the overhead cast type of loading. It is necessary to have an ore car either close or attached to the machine, so the material cast from the bucket will land in the ore car.

Loading ore with mucking machine

Selecting a Mine Haulage System

Start

!

Vertical --------------------------------- No ----- Shallow Overburden

Yes

Shaft --------------------------------- No ----- --------Sound Rock

Yes

Hoisting --------------------------------- No ----- Orebody < 500m deep

Yes

Production < 5000tpd -- ---- No ---- Inclined Belt Conveyor

Yes

----- Production < 2500 tpd ----- No ---- Orebody < 300m deep

Yes Yes

Ramp Haulage by Truck Ramp Haulage by Truck

MATERIALS HANDLING

• In cyclic operations, the two principal operations are loading and haulage with hoisting an optional third. In continuous operations, where machines combine the breakage and handling functions, cutting, drilling and blasting are eliminated, and extraction and loading are performed in a single operation or function (excavation) e.g. bucket wheel excavator, auger, highwall mines, continuous miner, boring machine.

• Materials handling in modern mechanized mining is equipment oriented. Unit operations are characterized by and sometimes identified with the equipment that performs them. Thus field terminology refers to a mining shovel, stripping dragline or coal loader.

• From time to time the mining engineer is faced with the necessity to make a haulage study to determine not only the most suitable method of hauling materials, but also

the most effective and economical type of equipment to use for the operation.

Typical Haulage Steps to move muck from a stope to surface

• The ore is drilled and blasted in the stope.

• The broken ore (muck) is picked up a LHD unit.

• Transported and dumped down an orepass into chutes on the level below.

• A train hauls the muck from the chute to a main orepass where it enters a skip and is hoisted to surface. Several main orepasses can be used throughout the mine.

Ore Transportation

Step 1 - From the Stope

• After the ore is blasted, it is removed from the stope. Most mines today use LHD or scooptrams to move the muck to centralized chute systems, which lead to levels below.

• Some mines use trucks, conveyor belts, pneumatic, or hydraulic systems to move the ore directly to surface

Ore Transportation

Step 2 - From the Chutes

• At the bottom of each chute is a gate mechanism which regulates the flow of the ore into ore cars. Production schedules determine which chutes should be "pulled" or emptied. In track mining, the chutes are located directly above the level below.

Ore Transportation

Step 3 - From the Level

• Ore in the chutes is usually loaded into ore cars and hauled by an electric loco to a centralized orepass. Tramming is the moving of ore from chutes to a central orepass. Ore car used underground range from 1/2 ton to 30 ton capacity. Cars are pulled by locomotives powered by electricity, diesel engine, or compressed air. Electricity can be supplied by an overhead trolley system or by their own batteries

Ore Transportation

Step 4 - Main Ore Pass

• All ore is dumped by the trains into a centralized ore pass. Gravity pulls the ore down to a loading pocket usually located at the bottom of the shaft..

Ore Transportation

Step 5 - Loading Pocket

• The loading pocket prepares the ore for loading on a skip. Oversize chunks are broken before entering the skip. Some mines use crushers to reduce the ore to about 6 inches in size. A measuring pocket is usually installed at the lower end of the storage pass. This holds only one skip full. There are protective devices to prevent this pocket from over-filling and spilling ore down the shaft. When the skip gets into position, the measuring pocket dumps rapidly into the skip.

Ore Transportation

Step 6 - Skip

• Skips are usually automatically self-dumping. A double drum hoist is used for skips. As one drum is wound the other is unwound, so when one skip is hoisted the other one is lowered into the

mine.

Ore Passes

• Mines take advantage of gravity to collect broken ore by means of ore passes. The ore passes are raises driven by drill and blast or raisebored. While ore passes are most commonly used for underground mining. Long raises are also employed as waste passes to drop quarried rock for cemented rock fill (CRF) from surface directly to the mining horizons.

• Ore passes often lead to an underground storage bin to provide surge capacity in the ore stream. In turn, the ore is normally drawn off the bottom of the bin into a chute

Ore Pass Inclination

• Most mine operators prefer that the ore pass be 70 degrees or steeper, but not vertical. Others prefer that the ore passes are all inclined at near 55 degrees. The steep ore passes are run nearly full while the ore passes at 55 degrees are run empty. Ore will not run on a footwall inclined at less than 50 degrees, which explains the minimum desired inclination

Ore Pass Linings

• In bad ground, ore passes are often lined with concrete. In many cases, the concrete is faced with a high strength steel liner that also provides the formwork that is required to pour the concrete.

• The steel lined ore pass has proven itself worldwide; however, the high cost and time required often make this design impractical.

Ore Pass Stability

• A circular ore pass is more stable than a square or rectangular ore pass. The latter invites arching on the sides and stress concentration at the corners. The most stable ore pass is a circular raisebored hole; however, this type of pass has two disadvantages. The first is the problem of placing ground support in the raise and the second is the fact that a smooth circular raise is more prone to hang-ups than a rectangular raise that has been drilled and blasted. In highly stressed, burst prone ground, an ore pass usually has to be raisebored for safety reasons.

Bins

• Underground bins are required to provide surge capacity to the ore stream. In the past, small mines simply slashed out an ore pass between levels to provide a bin. Today, most underground bins stand vertical and have a circular cross section. Larger bins are built with the bottom coned to inhibit rat holing of the ore. In some cases, liners are provided in the cone section to improve ore flow. Until recently, the maximum practical underground bin diameter was approximately 28 feet.

Chutes

• Chutes are inclined steel troughs used for transferring shot rock. Near vertical chutes are covered on four sides and equipped with an access door. Inclined chutes are often left open on top to facilitate clearing blockages. The chute width should never be less than three times the size of the largest lump to be free running. Chute inclination in most operating mines varies between 37 and 40 degrees. Steeper chutes may require control chains to stem the muck flow

Chutes

MATERIAL PROPERTIES

• Bank: Usually applied to weights or volumes of materials. The bank-weight or bank-volume of a material refers to material in its natural state before disturbance. It is often referred to as "in-place" or "in-situ" material. A unit volume is referred to as bank cubic yard (bcy) or bank cubic meter (Bm3).

• Loose: Material which is in a loose, broken or blasted state or material that has been excavated or loaded. A unit volume is referred to as loose cubic yard (Lcy) or loose cubic meter (Lm3)

• Swell: Rocks or Soils increase in volume when they are excavated or blasted because soil or rock grains are loosened during excavation and air fills the void spaces created. Consequently, a unit volume of soil or rock in the bank condition will occupy more than one unit volume after excavation. This phenomenon is called swell.

Types of Excavating and Bulk Handling Equipment

• a) Mobile Bulk Handlers - trucks, shuttle cars, ram cars b) Mobile Excavators - dozers, tractor scrapers, FEL c) Transitional Excavators - shovels, draglines, clamshells, muckers, cutters, loadersd) Integrated Excavators - boring machines, continuous miners, BWE dredges, longwallse) Intermediate Handlers - railroads, hoists, tramways f) Fixed Handlers - belt, flight, spiral conveyors

TRUCK HAULAGE

• In handling earth, aggregate rock, ore, coal and other materials, trucks serve one purpose. They are hauling units which, because of their high speeds when operating on suitable roads, have high capacities and provide relatively low hauling costs.

• They provide a high degree of flexibility as the number in service may be decreased or increased easily to permit modifications in the total hauling capacity of a fleet.

Capacity and PRODUCTIVITY

• Truck capacity measured on a weight rather than volume basis and divided into normal and giant sizes.

• Normal sizes: 22, 30, 35, 40, 55, 85, 100, and 130 tons Giant sizes: 150, 175, 200, 250, 300, and An estimate of haulage production must indicate sustained or average hauling production over a long period of time. Two of the estimating factors which are employed to permit the estimator to develop the average hauling production of the equipment being evaluated in the estimate are job efficiency and machine availability.

RAIL (LOCOMOTIVE) HAULAGE

• Whenever large tonnages have to be transported over relatively long distances on a relatively flat terrain, locomotive haulage is often the most efficient system to use. Rail haulage today in mining stands at the cross roads. Radical departures must be made from past practices and new innovations made in order for rail haulage to remain a viable alternative in the face of new developments for the transport of materials in mines

Advantages of Rail Haulage

• 1. Very low production costs where production requirements and volumes justify their installation. 2. Small labor force required. 3. Very versatile as to the type of materials handled. 4. High tonnage capacity 5. Spillage is minimal 6. Minimum maintenance requirements 7. High loading and unloading costs can be justified by economy of haul and high tonnage. 8. Efficient and cheap over long distances. Increased haul distance does not increase costs proportionally. 9. Traffic control is simple using two-way radios. 10. Can provide a certain amount of regeneration on downhill runs resulting in energy savings. 11. Ability to utilize automatic traffic control systems (CTC) and to operate the locomotives remotely. 12. Good availability

Disadvantages of Rail Haulage

• 1. Locomotives are limited to fairly shallow gradients 2. Frictional grip between the driving wheels and the rails also limits the size of train which can be hauled. 3. Mines considering rail haulage must have large reserves to support long life and large production. 4. High initial installation costs 5. System is inflexible 6. Special unloading devices required. 7. Mostly used in ore transport due to difficulty in spreading waste.

Types of locomotives used in mines today

• 1. Diesel Electric - most prevalent because they can be adapted to any track gauge and are available in all sizes from small switch engines to large freight haulers.

• 2. Trolley Electric - have a top mounted pantograph or a side mounted collector to receive power provided by an electrified wire.

• b. voltages: 250 V and 500 V

• c. Size range: 2 - 50 tons.

Haulage

Types of Rail Cars

• a. Side dump - more versatile and usually with capacities that range from 30 yd3 to 50 yd3.

employed in hard rock mines and metal mines.

can dump on either side

b. Bottom dump more prevalent in coal mines

fast unloading

• higher maintenance costs.

• c. Rotary dumping machines which turn over the rail cars for quick dumping of ore.

• d. Rocker type

Conveyors

• Underground hard rock mines use belt conveyors for lateral and inclined ore transfer; however, belt conveyors are not as popular as they are for similar surface applications. Belt conveyors for underground service usually are designed more rugged and operate at slower speeds than a comparable overland conveyor.

• Hard rock mine belt conveyors normally require the ore to be crushed before it is conveyed or at least broken enough to pass through a grizzly opening. The finer the ore is crushed, the longer the belt life, the more reliable the system, and the

lower the operating cost.

The capsule pipeline

• Sumitomo’s announcement that it has successfully tested transportation of limestone in solid form by capsule pipeline is path-breaking news. While transportation of slurry has been in place and pipelines handling crude over several thousands of kilometers across countries are in existence, the capsule transportation of aggregates is a milestone in mine transportation history.

The system runs trains of wheeled capsules with limestone in a pipeline using low air pressure. The entire system is centrally computer controlled and needs minimum attention and personnel. Since the pipeline is maintenance free and also tamper proof, many of the problems associated with other systems like trucks and conveyors are eliminated. A major advantage of the system is its immunity to climatic conditions. It is important to note that this system is very eco-friendly.

You have reached the end of unit 20.

Mine Haulage

Documents

Transcript of Mine Haulage