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Tools for Mining: Techniques and Processes for Small Scale Mining (GTZ, 1993, 538 p.)
	Technical Chapter 10: Surface Mining Equipment
		(introduction...)
		10.1 Aerial cable-way by gravity
		10.2 Cable tool drill
		10.3 Suction dredge
		10.4 Hydram, hydraulic ram pump, rife ram
		10.5 Noria
		10.6 Tyre pump
		10.7 Archimedian screw
		10.8 Boat mill
		10.9 Hydraulic mining gravel pump mining

Tools for Mining: Techniques and Processes for Small Scale Mining (GTZ, 1993, 538 p.)

Technical Chapter 10: Surface Mining Equipment

SPECIFIC SURFACE MINING TECHNIQUES

10.1 Aerial cable-way by gravity

Pit Banks for Deep Mines and Open-Pit Mines
Surface Mining Equipment

germ.:

Einfache Schwerkraftseilbahn

span.:

teleferico simple por gravedad, cablevia por contrapeso, andarivel por contrapeso

quechua:

hualaycho

TECHNICAL DATA:

Dimensions:

depends on vertical deviation as transport distance

Form of Driving Energy:

technique without external drive

Operating Materials:

Which:

lubricants

Quantity:

small quantity

ECONOMICAL DATA:

Investment Cost:

somewhat low, pulleys, cable, container

Operating Cost:

very low

CONDITIONS OF APPLICATION:

Operating Expenditures:

low |————|————| high

Maintenance Experience:

low |————|————| high

Location Requirements:

extensive difference in topographic level is needed to overpower the friction only by weight of material

Mining Requirements:

the mine or production is above topographic level of beneficiation or further processing

Replaceable Equipment:

roads with transport of mined ore by truck to beneficiation or reloading place

Regional Distribution:

worldwide applied, not only for mining

Experience of Operators:

very good |————|————| bad

Environmental Impacts:

low |————|————| very high

eventually avoids roads and their consequences (erosion, etc.)

Suitability for Local Production:

very good |————|————| bad

Under what Conditions:

construction of foundations for pulley piles, probably installation of stretching device

Lifespan:

very long |————|————| very short

Bibliography, Source: Priester, Hentschel

OPERATING PRINCIPLE:

Aerial cable-way by gravity is comprised of a circulating cable guided by two pulleys, one at the upper loading level, and the other at the lower unloading level. The buckets which are hitched on the cable are driven by the difference in weights of loaded or non loaded material.

Thus, the loaded bucket is driven along the cable downward by gravity and pulls the empty one upwards for the next hauling procedure. To control speed, one pulley (preferably the upper one) has a brake, e.g. band brake or shoe brake. An automatic unloading device can contribute to make haulage easier. One pulley should allow cable tension or stretch to vary.

REMARKS:

As an alternative, the simple gravity aerial cable-way can be equipped with separate rail ropes and pull ropes or brake ropes. Two parallel stretched cables serve as rail ropes. They are usually made of mashed wire steel. Along the cables, rollers run which carry suspended buckets. The pull or brake rope that leads over a pulley and put on the brake, connects the two buckets. These are equipped with bottom gates which open automatically while passing a ripper.

Aerial cable-ways driven by gravity are used where ore is to be transported from a mine at the mountain side toe a processing plant located in the valley. Often, processing is bound at the river side to avail of huge quantities of water for Industrial purposes including for hydromechanic driven machines.

SUITABILITY FOR SMALL-SCALE MINING:

Following the chutes, gravity driven aerial cable ways are the simplest and cheapest systems for transporting in vertical distances.

10.2 Cable tool drill

Open-Pit Mining, Well Drilling probably Deep Mining
Surface Mining Equipment

germ.:

Seilbohren

span.:

perforacion a cable

TECHNICAL DATA:

Dimensions:

pennsylvanian drilling

drilling in China

lift 500 - 1000 mm

striking height of bit

frequency approx. 30 min-1

up to about 12 cm

Driving Capacity:

12 - 15 strikes per minute

Mode of operation:

continuous

Throughput/Capacity:

2 - 5 years for 1000 m deep drillings in China

Technical Efficiency:

at 250 mm (above) - 125 mm (below) 0 0.5 - 1.2 m/d

ECONOMICAL DATA:

Operating Cost:

very low drilling cost, partly high rope wear

CONDITIONS OF APPLICATION:

Operating Expenditures:

low |————|————| high

Maintenance Experience:

low |————————| high

Deposit Requirements:

brine and natural gas were already found (before Christ) while drilling with a cable tool drill, where sandstone rocks, soft sandstones, limestones, claystones, generally non sturdy, cohesive loose rocks were drilled out but are not supposed to break back andshould not show much Joining or big cavities, such as karst.

Replaceable Equipment:

bench drilling machines, probably in quarries

Environmental Impacts:

low |————|————| very high

Suitability for Local Production:

very good |————|————| bad

Under what Conditions:

cable tool drilling, for example with wooden drilling rigs and wooden or metallic drilling beam can be produced locally

Lifespan:

very long |————|————| very short

a problem is the short lifespan of rope

Bibliography, Source: Feldhaus, Arnold, Treptow, Schmiedchen

OPERATING PRINCIPLE:

In China, cable tool drilling was used with a four-leg rig made of bamboo bundles, above which a drilling tool bit hanging on a rope was being moved. The movement was caused either by a seesaw, e.g. a one side tipping wooden beam on which one or two persons bounced Up and down' or directly by pulling the rope. This then lifted the drill bit a little above the drill bottom and fell down consequently due to its own weight. By twisting the rope, the drilling bit could be moved or turned. Once the drill bottom was filled with drill cuttings, these loose materials were taken out or excavated into the surface by a simple bailer pulled by the rope. In the mounting and dismantling of the bit and the bailer, a hoist is being used. Bamboo rods served as casings which are partly sealed off with bitumen, resin and linen rags. Water bearing strata could be filled up with mud or clay and resin and could be penetrated again. The Pennsylvanian cable tool drilling method follows the principle of this chinese cable free falling drilling.

AREAS OF APPLICATION:

for drilling of vertical deep blasting holes in open-pit mining
for sampilag
for putting down ventilation holes with 100 - 150 mm diameter

REMARKS:

Cable tool drilling is known in China since more then 2000 years in boring for salt brine sources.

Disadvantages of cable tool drilling are:

- difficult assessment of rope lift due to rope twisting
- aperiodic rotation due to twisting of rope
- no possibility to apply water circulation or flushing
- difficulties in fishing out lost bit if rope breaks, usually a system of rods has to be available

Advantages of cable tool drilling are:

- low weight of needed drilling equipment
- fast installation of drill device
- very straight, exact vertical holes

Rope elasticity is being used in drilling, which means the rope is still stretched as it reaches the drill bottom. Otherwise it will be compressed which leads to breaking of the rope near the bit joint. The Pennsylvanian cable drilling method avoids this rope compression by using drilling jars in the drilling tool.

SUITABILITY FOR SMALL=SCALE MINING:

Cable tool drilling is a suitable technique of putting down deep vertical drill holes without the use of external energy. However, drilling efficiency is comparably low.

Fig.: The chinese method of putting down a deep well. Source: Feldhaus.

Fig.: Deep drilling installation in China. Source: Arnold.

Fig.: Drilling instalation in China with percussion device in ca. 600 before Chr. Source: Arnold.

Fig.: Piping or pipe installation in a Chinese deep drilling in ca. 600 before Chr. Source: Arnold.

Fig.: Schematic diagram of the Pennsylvanian cable drilling method. Source: Schmiedchen.

10.3 Suction dredge

Aluvial Mining in Open-Pit on River
Surface Mining Level Equipment

germ.:

Saugbaggerflo�e

span.:

dragalina de succion, draga aspirante, draga de succion

Producer:

Keene, HG (Colombia), Humphreys Mineral Ind., Mining Equipment Inc., Dopke, COMESA, IAA

TECHNICAL DATA:

Dimensions:

approx. 2 × 3 m area

Weight:

from 20 - 350 kg weight of machines (engine, pump, chutes)

Extent of Mechanization:

fully mechanized

Form of Driving Energy:

approx. up to 10 PS internal combustion engine

Technical Efficiency:

Other Opportunities: probably drive type "Schiffsmuhle" (see 10.8)

Mode of Operation:

semi-continuous/continuous

Throughput/Capacity:

from 7.5 m³/d to approx. 220 m³/d

Operating Materials:

Which:

gasoline

Quantity:

0.3 - 1.0 I/m³ sediment

ECONOMICAL DATA:

Investment Cost:

approx. 7500 to 20.000 DM

Operating Cost:

fuel cost

Consequential Cost through Coupling Effects:

eventually outboard motor

CONDITIONS OF APPLICATION:

Operating Expenditures:

low |————————| high

two man crew, one diver

Maintenance Experience:

low |————|————| high

Location Requirements:

river with depth of < 10 m

Ore Requirements:

relatively high amount of large sized material

Deposit Requirements:

alluvial, not cemented, loose sandy sediment

Adjoining Rock Requirements:

low clay content

Mining Requirements:

significant locations for mining are places where natural strips or barriers at the river bed traps for gold particles have been formed

Regional Distribution:

Bolivia, Brazil, Ecuador, Colombia, Venezuela, etc.

Experience of Operators:

very good |————|————| bad

Environmental Impacts:

low |————|————| very high

exhaust, fumes, used oil, river contamination by muddy waste which flow back into the river

Suitability for Local Production:

very good |————|————| bad

if components are imported such as motor and pump

Lifespan:

very long |————|————| very short

Bibliography, Source: Dahlberg

OPERATING PRINCIPLE:

The whole machinery unit (e.g. suction pump, engine, beneficiation) is installed on a floating boat anchored at river banks or controlled by an outboard motor. The motor drives a centrifugal pump. Water is injected by a pressure hose near the suction nozzle into the suction hose and carries water and sediments through this suction hose. This mud flow reaches the float and on a mostly simple gravimetric separation with screening off of large sized fractions and various types of through washers. The remaining pre-concentrate will then be sorted out later by batea, and finally, will either be sorted by hand or amalgamated.

AREAS OF APPLICATION:

Suction dredges are applied or used for mining of alluvial gold in riverbeds. Between 0.75 and 22.5 m³/h sediment is being pumped from a depth of 2 - 10 m with a suction nozzle diameter of between 15" and 8", and is then processed.

REMARKS:

Due to the mostly simple processing with through washers, only large sized gold particles are won. Thus, fine gold is lost. It is to be investigated if fine gold extractions can be recovered by spiral separator or centrifuge. It would be advantageous if the material would have been completely suspended already.

The smallest suction dredges are transportable and are weighing only about 25 kg including the float. In this case, floats are made of truck tyres. Bigger floats have an uplift mechanism, for instance, by the use of barrels.

Bigger floats are equipped with compressed air supply for the divers who will then guide the suction nozzle directly along the river bed or ground.

SUITABILITY FOR SMALL-SCALE MINING:

Not considering the somewhat high amount of investment and operation cost, suction dredges are quite suitable for small-scale recent fluviatile alluvial gold mining with relatively large size particles. Thus, deposits can be mined which otherwise cannot be extracted with manual rustic mining methods.

Fig.: Schematic diagram of a suction dredge. Source: Dahlberg.

10.4 Hydram, hydraulic ram pump, rife ram

Pit Banks for Deep/Open-Pit Mining General
Surface Mining Equipment

germ.:

Wasserschlagpumpe, hydraulischer Widder, Sto�heber, Druckstopumpe, Wassersto�er

span.:

bomba a golpe de ariete, ariete hidraulico, bomba de impulso a presion, impulsor de ague

Producer:

WAMA, Campo Nuevo, Pfister & Langhans, Gebr. Abt, Schlumpf AG, Ch, J. Blake, Las Gaviotas, Rife Hydraulic Engine Man., Cyphelly & Cie, Inteco

TECHNICAL DATA:

Dimensions:

from 3 - 12 1/min (3/4") drive water, 320 mm height to 280 - 600 1/min (6") 1400 mm

Weight:

18 - 427 kg

Extent of Mechanization:

partly mechanized

Form of Driving Energy:

energy of drive water

Mode of Operation:

semi-continuous

Throughput/Capacity:

quantity of pump water depends on conveying distance: head of drive water 40 % (2 : 1 ) - 1.25 % (20 : 1 ) up to 250 m conveying distance

Technical Efficiency:

30 - 60 %

Operating Materials:

Which:

drive water

Quantity:

depends on conveyance discharge and head of water (minimum 0.5 m)

ECONOMICAL DATA:

Investment Cost:

brand new, fob Grafing 1400 to 2.000 DM; Campo Nuevo approx. 250 to 550 US$

Operating Cost:

very low, low maintenance, very low wearing

Consequential Cost through Coupling Effects:

delivery pipe, hydraulic engineering works

CONDITIONS OF APPLICATION:

Operating Expenditures:

low |————|————| high

Maintenance Experience:

low |————|————| high

Personnel Requirements:

very few, only a periodic control of air content in the air chamber is important

Location Requirements:

water and relief necessary

Mining Requirements:

typical application is in alluvial mining in flood-plain terraces which lie above the drainage level

Replaceable Equipment:

all kinds of pneumatic, mechanical and electrical pumps

Regional Distribution:

earlier worldwide, replaced by electrical systems

Experience of Operators:

very good |————|————| bad

Environmental Impacts:

low |————|————| very high

Suitability for Local Production:

very good |————|————| bad

Under what Conditions:

metal manufacture, construction material: standardized pipes

Lifespan:

very long |————|————| very short

Bibliography, Source: Fracokel, Meyer, Monninghoff, companies inforation

OPERATING PRINCIPLE:

Drive water flows through the lower part of widder and is released through the open waste valve with accelerating speed. If the speed exceeds a certain limit, the waste valve is automatically closed by the streaming water. A pressure peak occurs caused by this inertia which opens the delivery valve to the air chamber. The backwater is being pressed into the air chamber until the accumulated pressure falls below the internal pressure of the air chamber. Here, the delivery valve then closes while the waste valve opens again.

The procedure as described above reiterates itself periodically. Water that is inside the air chamber is then conveyed through internal pressure to the end user by a delivery pipe.

AREAS OF APPLICATION:

Hydraulic ram pump can always be applied where huge quantities of water with low falling gradient are available and where simultaneously, water is needed above water level for mining, beneficiation, water supply or for other purposes.

REMARKS:

This pump was invented by the Montgolfier Brothers who were awarded with a related patent in France In 1797, and called It hydraulic ram pump or hydram.

Hydraulic ram pumps are suitable for local production if qualified metal manufacture shops are available. As a result, the pumps components can be manufactured with simple pipes, etc. and allows savings in the cost of material and complicated welding works.

A very important source of failure in the operation of the hydram lies with the fact that air cushion in the air chamber can dissolve in (drive) water. If this happens, huge pressure peaks occur in all parts of the hydram thus stopping delivery. As a counteraction, a hole can be drilled into the drive water pipe near the hydram entrance to let fresh air enter into the air chamber, using the principle of the jet pump.

Of further importance is the length of drive water pipe which influences pressure distribution by the closing and opening of valves. Length of the pipe should be preferably between 5 - 12 times of the water gradient or inclination.

Drive water should be free of suspended materials and sediments as much as possible.

It is necessary that the water drive pipe is made of metal since flexible materials, such as PE or PVC usually yield to pressure peaks which then leads to falling pressure and decreased efficiency in the conveyance. The delivery pipe can be made of plastic and can be connected with adhesives, welding seams, or clamping devices.

SUITABILITY FOR SMALL-SCALE MINING:

Hydrams are very suitable for mining purposes if infrastructure for energy supply is lacking, but sufficient water and water level differences are available. The pumps are very reasonably priced, they are stable and are suitable for local production.

Fig.: Function of a hydraulic ram pump. Source: Fraenkel.

Fig.: Different types of hydrams. Source: Fraenkel. Above left: Traditional European type (Blakes); Above right: South-East-Asian type; Below: Hydram made of pipes.

Table: Falling and efficiency gradients for a hydraulic ramp pump. Source: Schlumpf Company Information.

Pumped quality as a percent of the water volume pumped throught the hydraulic ram:

Table

10.5 Noria

Pit Banks for Deep/Open-Pit Mining General, Open-Pit Mining General
Surface Mining Equipment Hauling

germ.:

Schopfrad, Hesselrad

span.:

noria, rueda elevadora

Producer:

M. Impler

TECHNICAL DATA:

Dimensions:

diameter 2.5 m and bigger, 0.7 m wide

Weight:

700 - 800 kg

Form of Driving Energy:

hydromechanic

Mode of Operation:

continuous

Throughput/Capacity:

1 I/sec, head of water approx. 1.5 m

Technical Efficiency:

up to 60 %

Operating Materials:

Which:

water

Quantity:

very low vertical interval, but high flowing speeds

ECONOMICAL DATA:

Investment Cost:

14.000 DM, substantially lower if locally produced

Operating Cost:

very low

Consequential Cost through Coupling Effects:

few water engineering works, flood protection

CONDITIONS OF APPLICATION:

Operating Expenditures:

low |————|————| high

Maintenance Experience:

low |————|————| high

Personnel Requirements:

low

Location Requirements:

water with streaming speed needed

Mining Requirements:

water demand should be relatively near above the river level since water head ranges only between ca 50 to 60 % of wheel diameter such as for beneficiation of raw ore mined from gravel terraces at river banks.

Replaceable Equipment:

smaller pumps, hydraulic ram pump

Regional Distribution:

historically, widely known; until today, still used in the agricultural industry in Asia and Africa

Experience of Operators:

very good |————|————| bad

Environmental Impacts:

low |————|————| very high

Suitability for Local Production:

very good |————|————| bad

Under what Conditions:

wood manufacture

Lifespan:

very long |————|————| very short

Bibliography, Source: M. Impler, Eckholdt, Meyer, Cancrinus, Fraenkel

OPERATING PRINCIPLE:

Noria is an undershot (Zuppinger-) water wheel with lateral attached buckets. It draws water from the river level and empties out automatically at the upper dead point into a draining chute. Needed is a relatively high streaming or flowing speed but a low falling gradient.

AREAS OF APPLICATION:

Water wheels are used for water haulage from large rivers to a level which is a little higher, such as for operating through washers, wet screening, etc. near a river.

REMARKS:

Wooden water wheels can also be designed so that components can be disassembled and allow its transporting even in remote areas.

Local manufacture with local materials can be implemented easily per instructions and leads to substantial cost savings.

A problem for the operation of water wheels are fluctuating levels of the water surface. If the water level rises to the height of axis, the water wheel could be damaged. Here, flood protection is indispensable. Besides, efficiency declines by a rising water surface level.

Water wheels were built with a diameter of 10 m (Syria) but were less efficient and needed more construction efforts than the other systems.

SUITABILITY FOR SMALL-SCALE MINING:

Only suitable in rivers with less daily or yearly fluctuating water levels and short conveying distance or low head of water.

Fig.: A water wheel in North Bavaria. Source: Eckhold.

Fig.: Lifting wheel. Source: Treptow.

Fig.: Early types of water conveying machines. Source: Cancrinus.

10.6 Tyre pump

Pit Banks for Deep/Open-Pit Mining General
Surface Mining Equipment

germ.:

Reifenpumpe

span.:

bomba con llanta como membrane

TECHNICAL DATA:

Dimensions:

approx. 1 m × 1 m × 0.5 m + rods

Weight:

approx. 30 kg

Extent of Mechanization:

not mechanized/partly mechanized

Form of Driving Energy:

mechanical, for example, energy from wind and water

Other Opportunities:

manual drive, pedal drive

Mode of Operation:

intermittent

Operating Materials:

none

ECONOMICAL DATA:

Investment Cost:

approx. 250 DM if locally produced

Operating Cost:

only labor cost

Consequential Cost through Coupling Effects:

driving system, leverage system

CONDITIONS OF APPLICATION:

Operating Expenditures:

low |————|————| high

depends on form of drive

Maintenance Experience:

low |————|————| high

Location Requirements:

low suction and pressure heights

Replaceable Equipment:

other types of diaphragm or piston pump

Experience of Operators:

very good |————|————| bad

Environmental Impacts:

low |————|————| very high

Suitability for Local Production:

very good |————|————| bad

Under what Conditions:

simple metal manufacture

Lifespan:

very long |————|————| very short

Bibliography, Source: Landtechnik Weihenstephan, Fraenkel

OPERATING PRINCIPLE:

A tyre pump is a simple diaphragm pump. The pump room inside the tyres enlarges and becomes smaller alternatively, as the space between the casings of the tyre increases and decreases pulsatingly. The check valves in the feed and discharge line control the inflow and outflow of water.

AREAS OF APPLICATION:

To convey huge quantities of water with small head of water.

REMARKS:

Tyre pump is one of the most simple forms of pumps driven by a pulsating connecting rod and works simultaneously with low pulse code (even < 100 min-1).

High forces appear to be a problem. A car tyre with 400 mm diameter has a working area of 0.126 m². Such area needs 1.230 N/m pressure height, which means for a 3 m diameter, this is approximately 3,7 N or 376 kg force of connecting rod. All in all, tremendous forces occur at the rods.

SUITABILITY FOR SMALL-SCALE MINING:

Tyre pump is the simplest design to pump water with slow R.P.M. of drive and high torque. It conveys large quantities of water with small head of water which is often used in alluvial gold mining.

Fig.: Schematic diagram of a tyre pump with eccentric tumbling rod. Source: Landtechnik Weihenstephan.

10.7 Archimedian screw

Alluvial Mining Open-Pit and Quarry Industry
Underground Mining Open-Pit Mining/Drainage

germ.:

Archimedische Spirale, Wasserschnecke, Tonnenmuhle, Wasserschraube

span.:

Espiral de arquimides, espiral pare desague

TECHNICAL DATA:

R.P.M.:

40 min-1 (min.) - 70 - 80 min-1 (max.); 20 min-1 (min.) - 40 - 50 min-1 (max.)

Angle of Inclination:

open: max. 30°, closed: max. 45°

Dimensions:

covered conveying screw 300 - 700 mm up to max. 12 m length, open screws: 500 - 900 mm

Extent of Mechanization:

not mechanized

Driving Capacity:

depends on head of water: 0.25 - 0.3 kW/m³/min × m h; open screws 0.2 - 0.3 kW/m³/min × m h

Form of Driving Energy:

manual or pedal driven (- 0.6 m h)

Other Opportunities:

in combination with wind wheel, animal power gear

Throughput/Capacity:

- 10 m³/min up to max. 6 m h

Technical Efficiency:

approx. 30 % (wooden traditional closed conveying screws) 60 - 70 % (steel screws in open concrete coverage)

Operating Materials:

none

ECONOMICAL DATA:

Operating Cost:

energy cost

Consequential Cost through Coupling Effects:

eventually a driving system

CONDITIONS OF APPLICATION:

Operating Expenditures:

low |————|—| high

depends on form of drive

Maintenance Experience:

low |————|————| high

Replaceable Equipment:

pumps with comparably high conveying rate for low head of water, e.g.,water wheel

Regional Distribution:

peat mining in Germany

Experience of Operators:

very good |————|————| bad

Environmental Impacts:

low |————|————| very high

Suitability for Local Production:

very good |————|————| bad

Under what Conditions:

wood manufacture

Lifespan:

very long |————|————| very short

Bibliography, Source: Fraenkel, Hausding, Rittinger

OPERATING PRINCIPLE:

The archimedian screw is comprised of a strong shaft which is twined by a spiral shaped surface thread. To be distinguished are open and closed conveying screws. The open screws rotate with tow tolerance within a fixed half cylindrical channel. The closed screws are completely covered by a cylinder which rotates with the screw. Water is being enclosed by plunging in of screw threads at the lower end of the archimedian screw. The slight inclined screw displaces water along the cylindrical cover upwards until it flows out at the upper end of the screw.

AREAS OF APPLICATION:

Draining of peat digging, water utilization with very low vertical interval, e.g. in open-pit mining within ground water.

SPECIAL AREAS OF APPLICATION:

Water conveyance with low head of water, recirculation of water in arid regions

REMARKS:

The archimedian screw is one of the oldest water lifting systems. It has been in use since about 200 B.C. in the silver mines In Spain.

Water screws are very stable against suspended solids and other impurisation of water to be conveyed.

Failure in operation of water screws are very seldom and can be easily repaired by an experienced technician locally.

Water screw is most efficient if the filling end is dipped by 50 - 65 % of its diameter into the water and decreases rapidly as the filling end is under water. For fluctuating water levels, a lifting device is recommended.

Only drives of low specific rpm are adequate in order to mechanize archimedian screws otherwise high losses in efficiency caused by shifting have to be put up with. "animal power gear" or wind wheels would be appropriate as drives.

The pitch of a water screw is mostly identical or a little smaller as the external diameter. The screw is often designed as double or tripple screw.

SUITABILITY FOR SMALL-SCALE MINING:

As manual pumps, archimedian screws are to be used for large conveyance quantities and low lifting height. Due to their simple design and high efficiency, archimedian screws are suitable for use as draining equipment in open-pit mines and for lifting industrial water.

Fig.: A cross-section of an open archimedian screw. Source: Fraenkel.

Fig.: A waterscrew. Source: Hausding.

Fig.: A manual driven archimedian screw. Source: Fraenkel.

Fig.: A archimedian screw, animal-driven by car axis. Source: Fraenkel.

10.8 Boat mill

Open-Pit Mining at River Level
Surface Mining Machinery

germ.:

Schiffsmuble

span.:

barco con ruedas hidraulicas pare generar energia, barco o ponton con ruedas de ague pare generar enegia

TECHNICAL DATA:

Dimensions:

approx. 15 × 5 m

Extent of Mechanization:

partly mechanized

Form of Driving Energy:

hydromechanical, hydraulic energy

Mode of Operation:

continuous

Throughput/Capacity:

up to approx. 10 kW

Technical Efficiency:

equal to a"Zuppinger" wheel: 65 - 70 % (see 19.6)

Operating Materials:

Which:

water

Quantity:

bigger river with strong rapids

ECONOMICAL DATA:

Investment Cost:

30.000 to 50.000 DM including water wheels

Operating Cost:

extremely low

Consequential Cost through Coupling Effects:

anchorage

CONDITIONS OF APPLICATION:

Operating Expenditures:

low |————|————| high

Maintenance Experience:

low |————|————| high

Location Requirements:

river with strong rapids

Regional Distribution:

today almost unknown

Experience of Operators:

very good |————|————| bad

Environmental Impacts:

low |————|————| very high

Suitability for Local Production:

very good |————|————| bad

but requires too much time and very expensive

Under what Conditions:

experienced wood manufacture, metal manufacture

Lifespan:

very long |————|————| very short

Bibliography, Source: Kur, Mager, Meyer, Muller 1939, v. Konig 1985

OPERATING PRINCIPLE:

Boat mills are stationarily anchored pontoons, floats or boats in river streams equipped with one, two or several undershot water wheels. They are similar to paddle steamers. However, the water wheels are not used as the driving unit, but used exclusively for the production of energy.

The mechanical energy can either be used directly for pumping, beneficiation or for other purposes, or can be converted into electrical energy by a generator (see below).

REMARKS:

A big advantage of the boat mill is its simple control and there's no need for water engineering works. The water wheels are always equally submerged deep into the streaming water, so that during both high and low tides equal forces are applied at the wheels at the same rate of rapid or streaming speed.

Thus, energy can be easily produced from large rivers with heavily fluctuating water levels, such as rivers in tropical climatic zones.

The conversion of energy into electrical power is difficult due to very low rpm of the driving axis of the boat mill. Beforehand, generators should be converted into slow moving generators by rewinding with long and fine wires. Only in this way can the necessary voltage be attained.

Likewise, a gear has to be placed between the driving axis and the generator.

Boat mills are very old forms in utilizing water energy or hydro power. Their invention could be traced back to 536 A D. and were found to have been used already in mining.

Boat mills were designed in two different models:

- with one water wheel between the main boat and the outrigger boat; and
- with two laterally attached, directly coupled or unattached undershot water wheels and only one boat or ship.

The second model is the one that is more suitable for production of energy and for mining purposes.

SUITABILITY FOR SMALL-SCALE MINING:

A good investment if utilized and financed collectively, such as by cooperatives under appropriate environmental conditions (isolated locations in large rivers). Main advantages are the multi-purpose utilization and there is no need for supply of operating materials and equipment.

Fig.: A boat mill with an outrigger boat and a main boat; left, side view; right, top view. Source: Kur.

10.9 Hydraulic mining gravel pump mining

Open-Pit Mining of Heavy Mineral and Precious
Surface Mining Extraction Metal Alluvial Deposits

germ.:

Kiespumpenabbau

span.:

explotacion con bomba de grave

Manufacturer:

Brauer (Mammutpumpe), Warman Dopke, Met. Lacha, Volcan Buena Fortuna

TECHNICAL DATA:

Dimensions:

10 - 50 m head of water, 6 - 12" delivery pipe, 50 - 600 m length (conveying distance)

Power required:

100 - 600 kW drive for gravel pump, less for water pumps for monitors

Form of Driving Energy:

diesel or electric motors

Alternative Forms:

none

Throughput/Capacity:

20 - 100 m³/h

Technical Efficiency:

about 0.45 for gravel pump, manufacturer's figures for new pump approx. 60 % by optimal operation

Operating Materials:

Type:

water

Quantity:

about 20 times the volume of conveyed material with additional auxiliary equipment about 10 times the material volume, up to approx. 65 % (by weight) solids (limestone) and 30 - 40 % (by weight) sand can be pumped

ECONOMIC DATA:

Investment Costs:

comparably low especially if locally produced. Gravel pump locally manufactured (Malaysia), 8 × 10", approx. 2000 DM without motor; for pumps (5 m³/h output) manufactured in industrialized countries approx. 5000 DM.

Operating Costs:

approx. 50 % for energy, 18 % for spare parts and material, 25 % for personnel

Related Costs:

high cost of energy-supply installation

CONDITIONS OF APPLICATION:

Operating Expenditures:

low |————|————| high

2 persons minimum

Maintenance Expenditures:

low |————|————| high

Location Requirements:

large quantities of water must be available

Deposit Requirements:

Gravel pump mining of alluvial deposits of heavy minerals (tin) and precious metal (gold) which exhibit non-consolidated or only slightly consolidated host rock and limited coarseness of granulation suitable for pumping. The strata underlying the deposit should be water-impermeable and preferably slightly inclined. There are no requirements regarding the thickness of the deposit. Steeply inclined overlying strata is unfavorable,and when present must be of minimal thickness.

Host Rock Requirements:

none; however, the abrasive strength of the host rock has a major effect on the lifespan of the pump in hydraulic mining

Replaces other Equipment:

dry mining with wheel loader, trucks, bulldozer, excavators

Regional Distribution:

in tin mining in Thailand and Malaysia, in gold mining worldwide

Operating Experience:

very good |————|————| bad

Environmental Impact:

low |——————| very high

The major cause of environmental pollution is the occaisional high sediment (sludge) load in the high quantities of waste produced; an additional source is the pump's drive-unit.

Suitability for Local Production:

very good |————|————| bad

Under What Conditions:

very good metal foundries are necessary for repeated casting of new sand-pump impellers. Gravel pumps are locally produced in Malaysia and Thailand.

Lifespan:

very long |————|————| very short

The working lifespan of gravel pump impellers ranges between 80 and 1200 hours of operation; for locally-manufactured Impellers this figure can lie substantially lower. It has been reported that in Thailand impellers can already wear out after only two days in operation, and are then melted down and recast in a local foundry. The lifespan of the pump housing is about three times longer than that of the impellers.

Bibliography, Source: Hageluken, Gartner

OPERATING PRINCIPLE:

In sand-pump mining of heavy-mineral and precious-metal alluvial deposits, mining is performed hydraulically, and the mined slurry is transported hydraulically to the beneficiation facility where it undergoes wet mechanical and gravity separation. Hydraulic mining can be differentiated according to two different methods.

Thin sediment deposits of medium-sized granulation with a thickness of less than 3 meters are mined from above by water jets. All other thicker deposits are mined from underneath with a so-called monitor. A monitor is a water-powered water Jet stream which is fed by a fresh-water pump (pressure up to 10 bars, discharge velocity 15 · 50 m/s). The jet stream is directed toward the part of the deposit to be mined, whereby the rock bonds are loosened from the impact, releasing the valuable minerals which then Join the slurry being drawn into the gravel pump. The hydraulic gravel pump is placed at the deepest point of excavation and hydraullically conveys the slurry, with a maximum solids content of 5 - 10 % (by volume), through the delivery pipe to the beneficiation facility. Gravel pumps are usually manufactured with wear-resistant housings and impellers. The beneficiation of the slurry occurs in a parallel-operated system of sluices, possibly with subsequent processing in Jig washers, spiral separators (see 14.18), conical separators or similar apparatuses.

SPECIAL AREAS OF APPLICATION:

Reverse-polarity gravel pumps are also used as turbines when turbid slurries or waters with high solids contents make up the propelling fluid flow.

REMARKS:

Gravel pump impellers are subject to extremely high wear due to the abrasive effects of coarse-grained suspended solids, the extent of which depends on the soil conditions. In general, impeller wear increases with increasing grain size. In order to limit this abrasive wear, it is advisable to screen the slurry prior to its being drawn into the pump, choosing a cut-off fraction Just above the largest grain-size with valuable-mineral content.

To avoid Individual particles from settling out during slurry transport, the specified minimum flow velocity must be maintained.

For positioning the gravel pump, the most successful solution has been to suspend the complete apparatus (directly-coupled pump and drive-unit) from a tripod. This avoids the necessity for an expensive foundation construction. Additionally, suspending the system from a tripod makes the frequent repositioning of the gravel pump easier as mining work progresses.

The smallest incline of the underlying strata between the monitor and the gravel pump should be at least 1:40 In order to avoid losses in valuable minerals through sedimentation. An auxiliary monitor, or booster, can possibly be used to maintain the slurry as a stable suspension and to transport materials which have already settled out.

To increase the density of slurry to be conveyed, auxiliary equipment such as bulldozers, hydraulic shovels, bucket wheel loaders, etc. are employed.

The drive-unit of the gravel pump should be about 30 - 50 % oversized to account, in advance, for excessive loading or increased output demands resulting from fluctuations in slurry density, extension of the delivery pipe, etc.

SUITABILITY FOR SMALL-SCALE MINING:

Gravel pump mining is characterized by its low investment cost but high cost of energy. It can be the most profitable method of mining heavy mineral sands if deposit conditions are suitable.

Fig.: Forms of hydraulic mining with with gravel pumps. Source: Gartner.longitudinal section I·I

1. gravel pump. 2. hydromonitor 3. water jet-stream flow direction 4. discharge direction of the slurry (sediment/water mixture)

Fig.: Sand-pump hydraulic mining operation with sluice separation. Source: Gast.

Fig.: Flow chart of alternative mining methods in Southeast Asian open-pit tin mines (not considering floating dredge operation or solid-rock quarries). Source: Hageluken.

Table: Summary of comparison of mining and transporting methods applied in Southeast Asian tin mining.

Source:Hageluken

A

B

C

D

Hidraulic transport

with monitor mining

with monitor mining and auxiliary equipment

Truck transport with dry mining

Combined truck and hydraulic transport

Water requirements

depending on type of earth generally very high since ore is loosened only by water impact

lower than A, since loosening of ore also by auxiliary equipment

low, water only needed for classifying and beneficiation

medium, for interim dump only small loosening forces required

Utilization of energy

bad, mainly transport of water

a little better than A, since higher contents of solids possible

depending mainly on loading capacity/total weight relation of trucks as well as on work organization and conditions of roads

Abrasive wear

depending on type of earth, generally high wear on pump and pipes

EME: depending on on type of soil, load and EME conditions of roads

HT: as A

Coordination of equipment capacity

difficult; necessary power varies after re-location of pump and changed pipe length; mostly oversizing of motors

EBG: simple, since appropriate equipment can be chosen

greater transport

HT: simple, since

distances require

length of pipes

high investments

remain constant

Downtime of the entire operation

by failure of water supply, by moving of the pump position and by failure of a part of the system (pump, pipes, beneficiation or dumping of tailings); direct connection from extraction to waste dump

Total downtime only there is no intermediate deposit and simultaneous failure of all extraction equipment or of all trucks resp. by failure of beneficiation of dumping or tailings if intermediate deposit is impossible

-

Intermediate buffer deposit

not possible

only limited (with auxiliary equipment at the face)

possible

already existing because of method used

Variations in content of solids

high because monitor operations in untouched material

depending on layout of dump, high when dumped directly on grate

lower with controlled monitor operation

Variations in content of valuable material

high because heterogene deposits and sedimentation of heavy minerals in delivery channel and pump sump

reduction of influence by deposit possible by means of blending stockpile

HT: as A

Desintegration of the ore

through monitor (auxiliary equipment), pump and pipe transport; long reaction time of water

by excavator and addition of water at dump point/screen short reaction time

as A, but shorter reaction time of water

Dependence on climatic conditions

in some areas the mining operation must possibly be ceased because of water shortage during dry season

generally, truck open ation is impossible during the rainy season

Operation in difficult terrain:

- swamp

possible

limited

not possible

- lime slone pockets

possible

limited

limited

Widespread very small deposits

only possible for very small mines since for larger operations continuous moving of haulage system and beneficiation would be required

possible, high flexibility through truck transport to centrally positioned beneficiation

Abbreviations: EME = earth moving equipment / HT = hydraulic transportation system

germ.:	Einfache Schwerkraftseilbahn
span.:	teleferico simple por gravedad, cablevia por contrapeso, andarivel por contrapeso
quechua:	hualaycho

TECHNICAL DATA:
Dimensions:	depends on vertical deviation as transport distance
Form of Driving Energy:	technique without external drive
Operating Materials:
Which:	lubricants
Quantity:	small quantity
ECONOMICAL DATA:
Investment Cost:	somewhat low, pulleys, cable, container
Operating Cost:	very low

Operating Expenditures:	low \|————\|————\| high
Maintenance Experience:	low \|————\|————\| high
Location Requirements:	extensive difference in topographic level is needed to overpower the friction only by weight of material
Mining Requirements:	the mine or production is above topographic level of beneficiation or further processing
Replaceable Equipment:	roads with transport of mined ore by truck to beneficiation or reloading place
Regional Distribution:	worldwide applied, not only for mining
Experience of Operators:	very good \|————\|————\| bad
Environmental Impacts:	low \|————\|————\| very high
	eventually avoids roads and their consequences (erosion, etc.)
Suitability for Local Production:	very good \|————\|————\| bad
Under what Conditions:	construction of foundations for pulley piles, probably installation of stretching device
Lifespan:	very long \|————\|————\| very short

TECHNICAL DATA:
Dimensions:	pennsylvanian drilling	drilling in China
	lift 500 - 1000 mm	striking height of bit
	frequency approx. 30 min-1	up to about 12 cm
Driving Capacity:	12 - 15 strikes per minute
Mode of operation:	continuous
Throughput/Capacity:	2 - 5 years for 1000 m deep drillings in China
Technical Efficiency:	at 250 mm (above) - 125 mm (below) 0 0.5 - 1.2 m/d
ECONOMICAL DATA:
Operating Cost:	very low drilling cost, partly high rope wear

germ.:	Saugbaggerflo�e
span.:	dragalina de succion, draga aspirante, draga de succion
Producer:	Keene, HG (Colombia), Humphreys Mineral Ind., Mining Equipment Inc., Dopke, COMESA, IAA

TECHNICAL DATA:
Dimensions:	approx. 2 × 3 m area
Weight:	from 20 - 350 kg weight of machines (engine, pump, chutes)
Extent of Mechanization:	fully mechanized
Form of Driving Energy:	approx. up to 10 PS internal combustion engine
Technical Efficiency:	Other Opportunities: probably drive type "Schiffsmuhle" (see 10.8)
Mode of Operation:	semi-continuous/continuous
Throughput/Capacity:	from 7.5 m³/d to approx. 220 m³/d
Operating Materials:
Which:	gasoline
Quantity:	0.3 - 1.0 I/m³ sediment
ECONOMICAL DATA:
Investment Cost:	approx. 7500 to 20.000 DM
Operating Cost:	fuel cost
Consequential Cost through Coupling Effects:	eventually outboard motor

Operating Expenditures:	low \|————————\| high
two man crew, one diver
Maintenance Experience:	low \|————\|————\| high
Location Requirements:	river with depth of < 10 m
Ore Requirements:	relatively high amount of large sized material
Deposit Requirements:	alluvial, not cemented, loose sandy sediment
Adjoining Rock Requirements:	low clay content
Mining Requirements:	significant locations for mining are places where natural strips or barriers at the river bed traps for gold particles have been formed
Regional Distribution:	Bolivia, Brazil, Ecuador, Colombia, Venezuela, etc.
Experience of Operators:	very good \|————\|————\| bad
Environmental Impacts:	low \|————\|————\| very high
	exhaust, fumes, used oil, river contamination by muddy waste which flow back into the river
Suitability for Local Production:	very good \|————\|————\| bad
	if components are imported such as motor and pump
Lifespan:	very long \|————\|————\| very short

germ.:	Wasserschlagpumpe, hydraulischer Widder, Sto�heber, Druckstopumpe, Wassersto�er
span.:	bomba a golpe de ariete, ariete hidraulico, bomba de impulso a presion, impulsor de ague
Producer:	WAMA, Campo Nuevo, Pfister & Langhans, Gebr. Abt, Schlumpf AG, Ch, J. Blake, Las Gaviotas, Rife Hydraulic Engine Man., Cyphelly & Cie, Inteco

TECHNICAL DATA:
Dimensions:	from 3 - 12 1/min (3/4") drive water, 320 mm height to 280 - 600 1/min (6") 1400 mm
Weight:	18 - 427 kg
Extent of Mechanization:	partly mechanized
Form of Driving Energy:	energy of drive water
Mode of Operation:	semi-continuous
Throughput/Capacity:	quantity of pump water depends on conveying distance: head of drive water 40 % (2 : 1 ) - 1.25 % (20 : 1 ) up to 250 m conveying distance
Technical Efficiency:	30 - 60 %
Operating Materials:
Which:	drive water
Quantity:	depends on conveyance discharge and head of water (minimum 0.5 m)
ECONOMICAL DATA:
Investment Cost:	brand new, fob Grafing 1400 to 2.000 DM; Campo Nuevo approx. 250 to 550 US$
Operating Cost:	very low, low maintenance, very low wearing
Consequential Cost through Coupling Effects:	delivery pipe, hydraulic engineering works

germ.:	Schopfrad, Hesselrad
span.:	noria, rueda elevadora
Producer:	M. Impler

TECHNICAL DATA:
Dimensions:	diameter 2.5 m and bigger, 0.7 m wide
Weight:	700 - 800 kg
Form of Driving Energy:	hydromechanic
Mode of Operation:	continuous
Throughput/Capacity:	1 I/sec, head of water approx. 1.5 m
Technical Efficiency:	up to 60 %
Operating Materials:
Which:	water
Quantity:	very low vertical interval, but high flowing speeds
ECONOMICAL DATA:
Investment Cost:	14.000 DM, substantially lower if locally produced
Operating Cost:	very low
Consequential Cost through Coupling Effects:	few water engineering works, flood protection

TECHNICAL DATA:
Dimensions:	approx. 1 m × 1 m × 0.5 m + rods
Weight:	approx. 30 kg
Extent of Mechanization:	not mechanized/partly mechanized
Form of Driving Energy:	mechanical, for example, energy from wind and water
Other Opportunities:	manual drive, pedal drive
Mode of Operation:	intermittent
Operating Materials:	none
ECONOMICAL DATA:
Investment Cost:	approx. 250 DM if locally produced
Operating Cost:	only labor cost
Consequential Cost through Coupling Effects:	driving system, leverage system

Operating Expenditures:	low \|————\|————\| high
	depends on form of drive
Maintenance Experience:	low \|————\|————\| high
Location Requirements:	low suction and pressure heights
Replaceable Equipment:	other types of diaphragm or piston pump
Experience of Operators:	very good \|————\|————\| bad
Environmental Impacts:	low \|————\|————\| very high
Suitability for Local Production:	very good \|————\|————\| bad
Under what Conditions:	simple metal manufacture
Lifespan:	very long \|————\|————\| very short

germ.:	Archimedische Spirale, Wasserschnecke, Tonnenmuhle, Wasserschraube
span.:	Espiral de arquimides, espiral pare desague

TECHNICAL DATA:
R.P.M.:	40 min-1 (min.) - 70 - 80 min-1 (max.); 20 min-1 (min.) - 40 - 50 min-1 (max.)
Angle of Inclination:	open: max. 30°, closed: max. 45°
Dimensions:	covered conveying screw 300 - 700 mm up to max. 12 m length, open screws: 500 - 900 mm
Extent of Mechanization:	not mechanized
Driving Capacity:	depends on head of water: 0.25 - 0.3 kW/m³/min × m h; open screws 0.2 - 0.3 kW/m³/min × m h
Form of Driving Energy:	manual or pedal driven (- 0.6 m h)
Other Opportunities:	in combination with wind wheel, animal power gear
Throughput/Capacity:	- 10 m³/min up to max. 6 m h
Technical Efficiency:	approx. 30 % (wooden traditional closed conveying screws) 60 - 70 % (steel screws in open concrete coverage)
Operating Materials:	none
ECONOMICAL DATA:
Operating Cost:	energy cost
Consequential Cost through Coupling Effects:	eventually a driving system

Operating Expenditures:	low \|————\|—\| high
	depends on form of drive
Maintenance Experience:	low \|————\|————\| high
Replaceable Equipment:	pumps with comparably high conveying rate for low head of water, e.g.,water wheel
Regional Distribution:	peat mining in Germany
Experience of Operators:	very good \|————\|————\| bad
Environmental Impacts:	low \|————\|————\| very high
Suitability for Local Production:	very good \|————\|————\| bad
Under what Conditions:	wood manufacture
Lifespan:	very long \|————\|————\| very short

germ.:	Schiffsmuble
span.:	barco con ruedas hidraulicas pare generar energia, barco o ponton con ruedas de ague pare generar enegia

TECHNICAL DATA:
Dimensions:	approx. 15 × 5 m
Extent of Mechanization:	partly mechanized
Form of Driving Energy:	hydromechanical, hydraulic energy
Mode of Operation:	continuous
Throughput/Capacity:	up to approx. 10 kW
Technical Efficiency:	equal to a"Zuppinger" wheel: 65 - 70 % (see 19.6)
Operating Materials:
Which:	water
Quantity:	bigger river with strong rapids
ECONOMICAL DATA:
Investment Cost:	30.000 to 50.000 DM including water wheels
Operating Cost:	extremely low
Consequential Cost through Coupling Effects:	anchorage

germ.:	Kiespumpenabbau
span.:	explotacion con bomba de grave
Manufacturer:	Brauer (Mammutpumpe), Warman Dopke, Met. Lacha, Volcan Buena Fortuna

TECHNICAL DATA:
Dimensions:	10 - 50 m head of water, 6 - 12" delivery pipe, 50 - 600 m length (conveying distance)
Power required:	100 - 600 kW drive for gravel pump, less for water pumps for monitors
Form of Driving Energy:	diesel or electric motors
Alternative Forms:	none
Throughput/Capacity:	20 - 100 m³/h
Technical Efficiency:	about 0.45 for gravel pump, manufacturer's figures for new pump approx. 60 % by optimal operation
Operating Materials:
Type:	water
Quantity:	about 20 times the volume of conveyed material with additional auxiliary equipment about 10 times the material volume, up to approx. 65 % (by weight) solids (limestone) and 30 - 40 % (by weight) sand can be pumped
ECONOMIC DATA:
Investment Costs:	comparably low especially if locally produced. Gravel pump locally manufactured (Malaysia), 8 × 10", approx. 2000 DM without motor; for pumps (5 m³/h output) manufactured in industrialized countries approx. 5000 DM.
Operating Costs:	approx. 50 % for energy, 18 % for spare parts and material, 25 % for personnel
Related Costs:	high cost of energy-supply installation

Operating Expenditures:	low \|————\|————\| high
2 persons minimum
Maintenance Expenditures:	low \|————\|————\| high
Location Requirements:	large quantities of water must be available
Deposit Requirements:	Gravel pump mining of alluvial deposits of heavy minerals (tin) and precious metal (gold) which exhibit non-consolidated or only slightly consolidated host rock and limited coarseness of granulation suitable for pumping. The strata underlying the deposit should be water-impermeable and preferably slightly inclined. There are no requirements regarding the thickness of the deposit. Steeply inclined overlying strata is unfavorable,and when present must be of minimal thickness.
Host Rock Requirements:	none; however, the abrasive strength of the host rock has a major effect on the lifespan of the pump in hydraulic mining
Replaces other Equipment:	dry mining with wheel loader, trucks, bulldozer, excavators
Regional Distribution:	in tin mining in Thailand and Malaysia, in gold mining worldwide
Operating Experience:	very good \|————\|————\| bad
Environmental Impact:	low \|——————\| very high
	The major cause of environmental pollution is the occaisional high sediment (sludge) load in the high quantities of waste produced; an additional source is the pump's drive-unit.
Suitability for Local Production:	very good \|————\|————\| bad
Under What Conditions:	very good metal foundries are necessary for repeated casting of new sand-pump impellers. Gravel pumps are locally produced in Malaysia and Thailand.
Lifespan:	very long \|————\|————\| very short

	A	B	C	D
	Hidraulic transport
	with monitor mining	with monitor mining and auxiliary equipment	Truck transport with dry mining	Combined truck and hydraulic transport
Water requirements	depending on type of earth generally very high since ore is loosened only by water impact	lower than A, since loosening of ore also by auxiliary equipment	low, water only needed for classifying and beneficiation	medium, for interim dump only small loosening forces required
Utilization of energy	bad, mainly transport of water	a little better than A, since higher contents of solids possible	depending mainly on loading capacity/total weight relation of trucks as well as on work organization and conditions of roads
Abrasive wear	depending on type of earth, generally high wear on pump and pipes		EME: depending on on type of soil, load and EME conditions of roads
				HT: as A
Coordination of equipment capacity	difficult; necessary power varies after re-location of pump and changed pipe length; mostly oversizing of motors		EBG: simple, since appropriate equipment can be chosen
			greater transport	HT: simple, since
			distances require	length of pipes
			high investments	remain constant
Downtime of the entire operation	by failure of water supply, by moving of the pump position and by failure of a part of the system (pump, pipes, beneficiation or dumping of tailings); direct connection from extraction to waste dump		Total downtime only there is no intermediate deposit and simultaneous failure of all extraction equipment or of all trucks resp. by failure of beneficiation of dumping or tailings if intermediate deposit is impossible		-
Intermediate buffer deposit	not possible	only limited (with auxiliary equipment at the face)	possible	already existing because of method used
Variations in content of solids	high because monitor operations in untouched material		depending on layout of dump, high when dumped directly on grate	lower with controlled monitor operation
Variations in content of valuable material	high because heterogene deposits and sedimentation of heavy minerals in delivery channel and pump sump		reduction of influence by deposit possible by means of blending stockpile
				HT: as A
Desintegration of the ore	through monitor (auxiliary equipment), pump and pipe transport; long reaction time of water		by excavator and addition of water at dump point/screen short reaction time	as A, but shorter reaction time of water
Dependence on climatic conditions	in some areas the mining operation must possibly be ceased because of water shortage during dry season		generally, truck open ation is impossible during the rainy season
Operation in difficult terrain:
- swamp	possible	limited	not possible
- lime slone pockets	possible	limited	limited
Widespread very small deposits	only possible for very small mines since for larger operations continuous moving of haulage system and beneficiation would be required		possible, high flexibility through truck transport to centrally positioned beneficiation
Abbreviations: EME = earth moving equipment / HT = hydraulic transportation system