Pranjal Sao

Mining…“the most difficult lighting environment in the world”

Illumination Engineering Society of North America, 2003.

Provision of suitable work

environment for the workers is essential for

achieving higher production and productivity in

both surface and underground mines. Poor

lighting working conditions have negative effects

on the workers’ morale and adversely affects

their safety, health and performance.

In order to assess the status

of illumination levels in mines, systematic

illumination surveys are needed to be conducted

using appropriate statutory guidelines so that

effective control measures can be taken up in

mines.

Light Physics

Two major systems of units are currently used for

the quantification of light-

1) illumination Engineering society (IES)

2)international systems of units (SI)

All standard systems of light units employ

certain fundamental concepts

These basic concepts are luminous flux,

illumination, luminous intensity, and luminance.

Intensity of light:

it is the relative amount of luminous energy given by

an source and is measured in candles or candle

power or in candelas (in CGS unit).

Mean horizontal candle power:

it is the average candle power of a lamp in all

directions in a horizontal plane passing through the

center of the sources and is usually obtained by

rotating the lamp about a vertical axis.

Mean spherical candle power:

it is the average candle power of a lamp in all

directions, or the candle power of a uniform source

giving the same total flux of light. It is directly

proportional to the total light given by the lamp and is

measured by taking intensity readings in all

directions.

Luminous flux:

The luminous flux symbol is Ø, and the lumen (lm)

is the flux unit n used in both the IES and SI

systems. Luminous flux is the time flow rate of light

energy. Flux is a power quantity in the same manner

as horsepower. The unit of luminous flux, the

lumen, is most frequently used to describe the

lighting power of light sources.

Lumen (unit):

The lumen (symbol: lm) is the SI unit of

luminous flux, a measure of the perceived power

of light. Luminous flux differs from radiant flux, the

measure of the total power of light emitted, in that

luminous flux is adjusted to reflect the varying

sensitivity o f the human eye to different

wavelengths of light.

Illuminance:

Illuminance is the amount of light falling on a

surface. The unit of measurement is lux (lx) and

2 lumen /min the SI system (or lumens per square

meter = 10.76 foot candles, fc). A light meter is

used to measure it. Readings are taken from several

angles and positions.

Luminance:

Luminance is the amount of light reflected

from a surface. The unit of measurement is

candela per square meter (equals 0.29 foot-

lamberts). An illuminance meter is used to measure

it. Several measurements are made and averaged.

Luminance tables are consulted for reference

values.

Reflectance:

This is the ratio of reflected luminous flux to

incident luminous flux. In other words, the ratio of

light energy reflected from a surface to the

amount striking it. Objects with higher levels of

reflectance will appear brighter than those of

lower reflectance under the same lighting

conditions

Contrast

The relative difference in luminance between two

adjacent surfaces.

In other words, how bright one surface looks

compared to the other or the background against

which it is being viewed.

Uniformity Ratio

This may be expressed as a ratio of average

to minimum or it may be expressed as a ratio

of maximum to minimum level of illumination

for a given area.

Surface Reflectance percentage(%)

Coal 3-15

Calcite stone dust 59

Dolomite stone dust 09

Rust 09

Fresh white wash 65-95

Faded white wash 20-60

General lighting arrangements have to be

provided in a mine at the following places and if

electricity is available the lights should be electric.

(a) On the surface at the pit top/incline top and

in every engine room if natural light is insufficient.

(b) Below ground:

At every shaft inset and shaft bottom or siding

which is in regular use;

In every travelling roadway normally used by 50 or

more person during any shift;

At the top and bottom of every self-acting incline in

regular use;

At every place on a haulage roadway, at which

tubs are regularly coupled or uncoupled from

haulage rope;

At every place at which tubs are regularly filled

mechanically;

At every room and place containing any engine,

motor or other apparatus;

At every place where any pillar is under ex

traction;

At every first aid station below ground;

Every lighting fitting in underground coal mine has to

be of flame proof design.

1. Acetylene portable hand

lamp:

A commonly used portable lamp in

metal mines is the acetylene hand

lamp.

It is also known as carbide lamp.

These are simple lamps that produce and burn

acetylene (C2H2) which is created by the

reaction of calcium carbide (CaC2) with water.

The conventional format of producing acetylene

in a lamp is by putting the calcium carbide in the

lower chamber (the generator).

The upper reservoir is then filled with water.

A threaded valve or other mechanism is used to

control the rate at which the water is allowed to

drip onto the chamber containing the calcium

carbide.

By controlling the rate of water flow, the production

of acetylene gas is controlled.

This, in turn, controls the flow rate of the gas and

the size of the flame at the burner, (and thus the

amount of light it produces).

This type of lamp generally has a reflector behind

the flame to help project the light forward.

An Acetylene Gas powered lamp produces a

surprisingly bright, broad light

. This type of unfocused light works well underground as it improves peripheral vision in the complete dark.

The reaction of carbide with water produces a fair amount of heat independent of the flame.

In a cold mine a carbide lamp can be used by a miner to provide a heat to help prevent hypothermia.

The first carbide lamp (mining lamp) developed in the United States was patented in New York on August 28, 1900 by Frederick Baldwin.

2.Flameproof safety torch:

Safety torches intrinsically safe in inflammable

atmosphere.

The torch is locked in the lamp cabin and can be

opened only by special tools. Unlocking and

opening in a mine is impossible.

The glass at the mouthpiece is toughened acrylic

disc(unbreakable type).

The glass is protected by a grill of 2mm wide

brassplates in the mouthpiece.

The bulb is protected by a spring placed over.

If the glass breaks, the spring is thrown out and

the bulb loses its contact with the battery terminal

thereby ceasing to burn.

Exposure of the hot filament of the bulb in case of breakage of the latter is out of question.

There is a spring cushion, a sort of shock

absorber, between the bulb and dry cell which

prevent crushing of the bulb against the weight of

the dry cells in case of accidental dropping of the torch.

3.Electric cap lamps:

The electric cap lamps used in our mines are the

popularly known Oldham cap lamps and also the

cap lamps manufactured by mines safety

appliances Co. ltd.

In cap lamps the entire cap lamp unit consists of a

4-v lead acid battery (re-chargeable type)

A lamp which can be hooked to the helmet and a

connecting cable. The lead acid battery consists of

two cells.

In the Oldham cap lamp unit each cell of the lead

acid battery consists of a number of composite lead antimony tubes or plates.

Plates carrying the active materials and immersed

in a 30% of sulphuric acid and distilled water.

The positive plate in each cell is of pasted flat

type, and the insulating separators are of sponac (

a highly absorbant type of wood) which absorbs about 85% of the total acid in the cell.

In the fully charged condition, the active material

in the positive plates in brown lead

peroxide(PbO2) and in the negative plates, it is

grey spongy lead (Pb).

During discharge, both positive and negative

plates change partly into lead sulphate ,with

liberation of water. During discharge, negative

plates ,it is grey spongy lead.

The following reaction takes place during charging, it is reversible reaction, during discharging-

PbO2 + 2H2SO4+ Pb = PbSO4 + 2H2O + PbSO4

problem Possible cause solution

Cap lamp does not give light

Battery was not charged Charge the battery

Damaged cable Replace the cable

Loose connections Tighten all loose connections

Loose non functional switch tighten replace the

switch

Problem with LED PCB

Battery does not accept charge

Loose battery connections

Tighten the battery connections

Worn out or damaged cable

Replace the cable

Worn out charging key Replace the charging key

Damaged charging circuit on the headpiece

PCB

Replace the PCB

Battery power does not last a shift after a full

charging cycle

Poor charging e.g. Charging rack does not

conform

Make sure the rack conforms to point 3.3

of this document

Blocked charging contacts Clear the charging contacts

Damaged LED driver circuit on the headpiece

PCB

Replace the PCB

Battery past its life expectancy

Replace the battery

LAMP ROOM LAYOUT

It is situated at the surface .

In this room batteries of the cap lamp are charged.

The batteries are of 4 volts.

These batteries are of lead acid battery

rechargeable type.

The nominal voltage of led acid cell is of 2 volt so

that two cell must be connected in series to give 4

volt.

Following reaction takes place in the cell:-

Pbo2 + 2H2SO4 + Pb =PbSo4 + 2H2O +PbSO4

5-6 volt D.C. power is required to charge the

battery, but 4.8 volt is the stander.

The light provided by the flame safety lamp and

electric cap lamp is inadequate for general lighting

and proper illumination in ug mines.

Electric lamp should therefore be used for general

lighting and at places where more illumination is

required.

When providing for general lighting car should be

taken to that workers should not have to face tha

glare of the lamps.

Deep shadows are not cast by the lights and there

is sufficient illumination.

An illumination on 20 to 40 lumens per m2 at the

pit bottom.

15to 20 lumens per m2 at haulage junction is

considered adequate.

Use of lamps of high candle power, but low

intrinsic brightness.

By closure spacing.

By white washing the area.

Power can be used at voltage exceeding 110

volts.

Lights at 220/250 volts cannot be used.

Lighting transformers should provide the voltage

by stepping down form the usual 550/440 or 3300

volts and neutral point of the secondary

transformer should be earthen.

All lights and light fittings should be in flame proof

enclosure.

There are only 2 or 3 well known companies in

India, who manufacture such flameproof light

enclosure.

It is not clearly laid down in the electricity rules it is

advisable not to use electric lights from mains at

or within a distance of 100 m from a longwall coal

face from emmision of firedamp.

Electric light can be used in the main return of

gassy mine degree 2 and 3, if the lighting fittings

are flame proof.

Electric discharge lamp.

Fluorescent tubes for mine lighting.

At atmospheric and higher pressure the resistivity

of gas is very high and a breakdown of this

resistivity by a sufficiently high voltage causes

spark or arc.

If the pressure of gas in a closed space is reduced

to a very low value not only is the voltage required

to breakdown the insulation of the gas reduced but

when this breakdown occurs the current passing

through the gas does not form an arc but forms

what is called a discharge.

The light produced by the current is not localized,

but comes from the whole of the rarefied gas

through which the current passes.

The colour of the life given by the discharge

depends upon the gas from which it takes place

and this colour can be varied by mixing different

gases.

A discharge in mercury vapour produces what are

called ultra violet rays.

It consist of long glass tube coated on the inside

with a fluorescent material and having tungsten

electrode at each end.

When the tube is switched on an electrical

discharge takes place across the electrodes.

The tube is filled with argon gas and mercury

vapour but it should be remembered that a

mercury vapour lamp is quite different type of

lamp of high wattage giving greenish light.

The colour of light available from a fluorescent

tube can be controlled by a suitable choice of the

composition of the fluorescent coating on the

inside of the tube.

The fluorescent tube has high effficiency the

lumen output been as much as 3.5 times that of

the incandescent filament bulb.

This is the reason for the popularity of fluorescent

tubes for lighting but the control equipment for

these lamps is more elaborate and they need

more maintenance.

Moreover these tube lights are not yet

manufactured in flameproof design in our country.

For degree 2 and 3 gassy coalmines they are not

permitted to be used underground but in degree

one gassy mine they may be installed with

permission from director of mine safety.

Some degree 2 coal mines have installed

imported fluorescent lamp of flame proof design.

For underground lighting the tubes have an

advantage of reduction of glare and they do not

produce strong shadow effacts but they suffer

from disadvantage of flicker.

They can be operated on 100 volts.

The wattage of these tube is low.

The most common industrial fitting takes two

tubes of 1.5m length giving a lamp wattage of only

160.

In a coal mine where gas is likely to be present it is tested with the help of a flame safety lamp in two ways.

1. Accumulation test2. Percentage test.

The purpose of this is to ascertain if

there is any accumulation of gas in

places where it may be suspected or

is likely to accumulate. In a mine, if

the mining sardar finds accumulation

of gas at any place, he has to inform

the matter to the overman who should

take steps for determining its % its

removal.

To test for accumulation, switch

off the cap lamp, raise the flame

safety lamp cautiously with normal

size of flame, or a flame only slightly

reduced and watch its behavior; if it

elongates i.e. if is spires or jumps, the

percentage of gas can be taken as

nearly 3 % or more.

No effort should be made to raise

the flame safety lamp higher than is

necessary to test for accumulation

because this result in keeping the

flame in richer mixture of methane

and air which may explode inside the

lamp and extinguish the flame.

Even if mixture is not explosive

the gas will burn inside the lamp and it

may produce CO2which will extinguish

the flame.

It is necessary to conductpercentage test when the flamespires up in a safety lamp as it isclear that the gas percentage is notless than 3.

If by mischance, firedamp begins to burn within the guage, it should in no circumstances be allowed to continue to burn.

The examiner should shelter his

lamp from the air - current, hold it

near the floor, and retreat carefully

covering the air-inlet holes with a

handkerchief.

To conduct percentage test formethane with flame safety lampremove all the bright light in vicinityand switch off the cap lamp. Lower inflame of the safety lamp with theregulating knob till there is acontinuous blue line (actually curvedline) across the top of the flame justabove a speck of white (or yellow) asshown in the plate.

This should be done not at the

place where has percentage is to be

detected, but at the place nearest to it

and free from gas.

Where fire damp present in the air

at spot of a non - luminous flame

(bluish) which varies in height

depending on the percentage of the

gas.

The size and height of the non-luminous flame produced by theburning of the gas cap alsodepends on the size of the wick(fig1.6) and the quality of the fuel usedhence for determining the gaspercentage, the lamp to be used,the size of wick and fuel has to bestandardized.

An oil flame safety lamp, through a

convenient handy and inexpensive

device for detection of fire damp has

certain limitations.

It can be used only by persons

trained for the purpose.

If there is a shortage of oxygen,

flame of the oil safety lamp will

reduce in size and will completely

extinguish if oxygen percentage is

17% or less. Minimum 14%

oxygen is required in supporting

human life.

If blackdamp or CO2 is present in

air, the flame of flame safety lamp

diminishes in size and will be

extinguished if CO2 percentage is 3

or more.

A commonly used portable hand lamp in

metal mines is the acetylene hand lamps.

The lower container contains calcium

carbide and is provided with a burner. The

upper container contains water which

flows to the lower container, drop by drop,

and is regulated by a valve operated by

hand.

The water acts on calcium carbide to

generate acetylene gas which can be

ignited at the burner to give a white flame

of good intensity

T lamp requires less oxygen for its

combustion than oil lamps. It does not

provide the early indication of the

presence of blackdamp as compared to

others oil lamps.

But it weights 1k without water and carbide.

Carbide lamps can withstand an air velocity

of 5m/s but for safe working the air velocity

should not exceed 2.5m/s

Fig: Acetylene portable hand lamps

While the introduction of the steam engine for dewatering and hoisting had led to the deepening of the collieries in England, the ventilation technology to control the increased dangers of methane fell behind. In the early 1800's, several large colliery explosions in the North of England had killed many pit men. Attention was called for the need of a flame lamp that would not ignite "firedamp".

Although there is a dispute to who invented the "first" miner's flame lamp that was safe to use in fiery mines, the success of the flame safety lamp was a culmination of the principles discovered by Dr. William R. Clanny, Sir Humphrey Davy, and George Stephenson. All three men worked independently on the problem at about the same time, and all had some knowledge of the other's work.

The principle of isolating the flame of the lamp was evolved by Dr. Clanny in 1813. Clanny's first lamp designs involved enclosing the flame, and pressurizing the lamp via bellows that would use water reservoirs to isolate the flame. The lamp was rather clumsy, and saw no practical use in the mines. But the feature of a glass window would be later a common feature on safety lamps.

At about the same time, Sir Humphrey Davy was performing several experiments of his own for the development of a safety lamp. In 1815, Davy discovered that if two vessels were filled with explosive gas, they might be connected together by a narrow tube, and the gas in one of the chambers could be exploded without transmitting the explosion to the adjoining chamber. This meant that a flame in a lamp, fed mine air through small orifices, would not ignite the surrounding air of the mine.

Davy's further experiments found that mesh-

holes of fine metallic gauze acted the same way

as narrow tubes. The adjacent drawing depicts

Davy's principle utilizing a Bunsen-burner. The

flame will burn on one side of the gauze without

igniting the gas on the under side of the

gauze. This is because the gauze will dissipate

heat fast enough that the temperature of the gas

beneath is unable to rise to the point of ignition.

Davy built a lamp that totally enclosed the flame

with a cylinder of gauze. While it did not give off

much light, it was success in minimizing,

although not eliminating, explosions from flame

lamps. Davy's wire gauze principle was used in

almost every type of flame safety lamp that was

developed for near 200 years.

While Clanny and Davy were working on their

safety lamps, George Stephenson (who would

later go on to invent the steam locomotive) was

working on his safety lamp. In 1815 ,

Stephenson was an enginewright at the

Killingworth colliery near New

Castle. Stephenson started developing and

testing lamps designed on 2 principles: 1)"burnt

air" (carbonic gas, CO2) would prevent

transmission of explosions. 2) The velocity of

burning firedamp was slow.

So, if an air draft opposite to the direction

of combustion of great enough velocity

could be created, transmission of

explosion would not occur. Stephenson's

third lamp was a success, and with

modifications was successfully used in

coal mines mainly in the North of England.

There has been a long dispute to as who really

invented the first "safety lamp". Clanny, Davy,

and Stephenson each contributed to the

evolution of the safety lamp. To summarize their

contributions:

Dr. Clanny- Separated the flame from the mine's

firedamp atmosphere.

Sir Humphrey Davy- Enclosed the flame in a

wire gauze.

George Stephenson- Leave space above the

flame for "burnt air".

Clanny eventually incorporated Davy's wire

gauze.

Stephenson eventually incorporated Davy's

wire gauze in his famous "Geordie" lamp.

The overpowering element that

perpetrated almost all flame safety lamp

designs was Davy's wire gauze. In fact,

Clanny and Stephenson eventually

incorporated Davy's wire gauze in their

design. This is why, even to this day, a

miner's flame safety lamp has generically

been called a "Davy Lamp".

Early on in the development of the flame

safety lamp, it was realized that it could be

used for gas measuring

purposes. Eventually, many lamps where

developed for the sole purpose of

measuring the amount of methane in a

mine atmosphere. Thus, safety lamps

where categorized as either for lighting or

gas measuring.

The safety lamp started to be replaced

with electric mine lighting devices after

1900. By 1930 or so, almost all flame

safety lamps were replaced by electric

lamps. But, safety lamps still continued to

be use for detecting and measuring gas

long after their use for lighting was

obsolete.

Instruments are required to evaluate lighting

systems and components.

The photometer is one of the most important tools

for illumination system design and evaluation.

Many types of photometers are available

to measure light energy and related quantities,

including illumination, luminance, luminous

intensity, luminous flux, contrast, color and

visibility.

Specific uses for underground mine illumination

survey are

Verification of compliance with illumination and

luminance specifications in the regulations;

Evaluation of illumination system design options.

Calculation of reflectance of mine and mine

simulator surfaces

Checking light distribution

Checking illumination reduction over time

Evaluation of discomfort and disability glare.

consists of a photocell that receives light and

converts it into an electrical signal

that is conditioned through an electrical circuit

and is displayed on a visual meter.

Before taking measurements with a photometer,

care must be taken to insure that a luminaries or

illumination system is in the proper condition to

satisfy the purpose of the measurements.

Color Correction

The meter reading is proportional to the light

energy level received by the photocell.

which adjusts the response of the assembly to

closely match that of the human eye.

Its done by the placement of filters on the

surface of the photocell

Calibration

Calibration is a method by which the response

of a photometer is set to match a working

standard.

Cosine Correction

The response of a photocell changes as the

angle of light falling on its surface changes

At high angles of incidence, a greater portion of

incoming light is reflected from the cell surface.

This is because the reflectance of most surfaces

increases as the angle of incidence increases.

The problem is corrected by placement of a

diffusing cover over the photocell.

This cover adjusts the level of light received by

the cell to the correct proportion for various angles

of incidence

Diffusing cover for cosine correction on

photometers

Temperature and Humidity Effects

Wide temperature variations effect the

performance of photocells.

Silicon photocells are less susceptible to

temperature variation when compared with

selenium photocells.

Sensitivity

Illumination and luminance levels in underground

coal mines are very low

A meter with high sensitivity and accuracy

permits the very necessary fine tuning of lighting

systems

Contamination

In mines, dust can rapidly accumulate on the

photo detector surface and diminish measurement

accuracy.

These factors can easily affect the accuracy and

useful life of an instrument.

Photometers should be kept in a well sealed case

and, to avoid contamination

Photometer Zeroing

It is important to check photometer zeroing prior

to taking measurements.

It should be verified that the meter remains

correctly zeroed, when the photometer scale

selector is changed.

Photometric measurements in mines are of three

types:

1. Illuminance measurement

2. Luminance measurement

3. reflectance measurement.

Illuminance measurement

This process measures the incident light (in lux)

received by a surface.

Three different techniques can be used in mine

illumination surveys:

1. Direct planar measurement

2. Separate measurements for direct and diffused light

3. Maximum reading method

In the planar measurement method, the general

illuminance level of the work place is measured

using photocell photometer. The photometer is

laid on the surface and readings are taken on

points at regular intervals.

In the second method, Separate determinations

of the quantity of light reaching the measuring

point directly from the source and the light

reaching the same point after one or more

reflections from the walls and roof are made

In the maximum reading method: in this method

the photocell is pointed at the light source and the

reading is normally resolved to the plane being

considered. The resolved component is

assumed to be the illuminance at the point of

measurement.

Luminance measurement

The photometer is aimed at the surface to be

measured. Luminance measurements state that

the photometer shall be held approximately

perpendicular to the surface being measured.

They also require that the sensing element be at a

sufficient distance from the surface to allow the

light sensing element to receive reflected light

from a field not less than 3 ft nor more than 5 ft .

Reflectance measurement

Four different methods are employed.

1. Incident –reflected light comparison

2. Standard chips comparison

3. Reflectance standard comparison

4. Sphere reflectometry

In the first method, a photometer is placed about

0.1 m from the surface and a reading of the

luminance is given off by the surface is recorded.

The meter is then turn around and the incident

light is measured ..

The reflectance is then calculated as the ratio of

reflected to incident light

place Minimum average

lumens/sq. ft.

Pit bottom 1.5 to 3.0

Main junction 1.25

Roadways 0.4

Haulage engines & control gear rooms

1.5

The roof and side should be

properly white- washed and stone dusted on

the floor as required under the statue to achieve

the illumination to the standards for providing

necessary visibility for safe and efficient work at

different places.

The standard of lighting in depillaring area

should be at less 1.5 lumens/Sq. ft. at the

floor level.

Deg. 1 gassy mines – four or more 250 watt bulbs

cluster if height of working is over 3m.

Deg. 2 or 3 gassy mines or mines having fire-

cluster of 15 to 20 cap lamps placed on a suitable

stand, in addition to cap lamps for individual

workmen.

Sl. no Place /Area Minimum

1. At the bottom of a sinking shaft10 Vertical

2. At the mechanized quarry face 15 Horizontal

3. At coal depot where wagons are loaded

10

3

Vertical

Horizontal

4. At fully mechanized long wall face 10 Vertical

The general lighting

scheme of an opencast mine generally connected

to common power source. The electric power

failure may occur at any time when the whole

area may be plunged in absolute darkness which

may lead to an accident .

Individual lights may,

therefore, be provided to individual workers in

addition to the general lighting scheme in the

opencast mines.

The very high benches ,up to

45m high ,made by draglines or other heavy

earth moving machinery (HEMM) are very difficult

to keep properly illuminated .It may become

difficult to pinpoint the places require dressing

,from the working points over the draglines or

Shovels.

Moving flood lights, akin to the hunters search

light on the boom of the draglines or on the

bucket of the shovels ,may be mounted and these

flood lights may be rotated at will lighting up

every nook and corner of the high benches.

Sl.no Place /Area to be illuminated

Manner in which it is to

be illuminated

Minimumstandard

of illuminatio

n(LUX)

Plane level in which

the illumination is to be provided

1. General working area as determined by the manager

in writing-

0.2 At the level of

surface tobe

illuminated

2.Work place of heavy

machinery

So as to cover the

depth and height

through which

5.0

10.0

Horizontal

Vertical

3.Area where bulldozer or

othertractor mounted

machineworks

- 10.0 At the level of crawler tracks

4. Area where drilling rig works

So as to illuminate

the full height of the rig

10.0 Vertical

5. Places where manual work isdone

To be provided at

level of the surface on

which work is done

5.0

10.0

Horizontal

Vertical

6.Place where loading or unloading or transfer

,loadingof dumpers ,trucks or train

iscarried on

- 3.0 Horizontal

7. Operators cabin of machines ormechanism

To be provided up to a height of 0.8m from

floor level

30.0 Horizontal

8. At hand picking points along conveyor belt

To be provided up to distance

of not less than 1.5m from

picker

50.0On the

surface of conveyor

belt

9. Truck hauling roads To be provided at the

level of the road

0.5 to 3.0

Horizontal

10. Rail haulage track in the pit

To be provided at the

level of the railheads

0.5 Horizontal

11. Roadways and footpaths from

bench to bench

- 3.0 Horizontal

12. Permanent paths for use ofpersons employed

- 1.0 Horizontal

Country/place

Shafts Loadings Around machines

Haulages Headings U/Gworkshop

Belgium 20-50 20 25 10

Hungary 40-100 40-60 20-50 2-10 20-50

Canada(British

Columbia)

21 21 53

Poland 30 30 10 2-10 5-15 30

( Source: ECSC, 1990; MVS, 1992; Piekorz, 1997)

UK(British coal)

70 30 2.5 50-150

European coal & steel community

40-90 15-80 5-15 10-30

West Germany

30-40 40 80 15

Czechoslovakia

15 20 20 5

South African gold

mines

20-160 160 20 400