Heat stress in mining MINE PORTAL TEAM - PowerPoint Presentation

Slide1

Heat stress in mining

MINE PORTAL TEAM

www.MINEPORTAL.in

CALL/WHATSAPP-8804777500

www.fb.com/mineportal.inSlide2

Heat source of underground mine

Unusual high heat flow from earth

.

Need for development of new sources of minerals calls for an expansion of underground mining deeper therefore, hotter levels of the earth crust.

Use of electricity and other mechanical processes adds to the heat load of underground mines.

Estimated 90-95% of the energy released in blasting find its way into the underground environment as heat.

By

Autocompression

Slide3

Source

--

www.smenet.org/docs/meetings/2008/030.pdf

underground heat contributorsSlide4

HUMAN BODY AND ENVIRONMENT

Human body metabolism provides heat and energy for our physiological functions.

When environment and our body has temperature difference ,part of difference become less through convection and radiation from body to surrounding environment.

An active person loses part of his body heat through sweat evaporation .

The body core can dissipate its heat only through the shell. Blood serves as a vehicle for heat transfer.Slide5

Assessing the heat risk

Several factors can influence the heat load on the body. These include:

air temperature (Wet Bulb and Dry Bulb);

radiant heat;

humidity;

air movement;

the level of physical work; and

the amount and type of clothing being worn.

It is not possible to estimate the strain placed on the body by examining any one of these factors in isolation. In the mining situation, where radiant heat is not a major factor, it has been found that the best index is the Effective Temperature (ET), because it takes air velocity into account. Slide6

Concern

The steady stage of thermal equilibrium is represented by the following heat balance equation

M - E +/- K +/- C +/- R=0

where,M

=Metabolic heat generated

E=Evaporative heat loss

K=Conductive heat exchange

C=Convective heat exchange

R=

Radiative

heat exchange

For normal body

function,heat

exchange between the body and it’s environment need to be balanced and practically relies on

convection,conduction

and evaporation.Slide7

Continued…

In hot

environment,where

ambient temperature reaches core body temperature ,conduction and convection as a mean of thermoregulation.

Hyperthermia is caused by accumulation of heat .

Humidity decreases sweat evaporation.

Clothing impedes convective heat loss and interferes with the evaporation of sweat from the skin.

Heat stress overall affects the worker efficiency and thereby affects the production.Slide8

Variation of mean skin temp. with ambient wet bulb temp. for clothed(light and heavy),unclothed

Source

--

www.he.gov.uk/pubns/mines07.pdfSlide9

HOW HUMAN BODY COPES WITH HEAT STRESS

Warm-blooded animals can function regularly in almost all types of weather and climate.

At best, only some percent of the energy generated by the body's metabolism is converted into mechanical work.

Too much heat will interfere with the metabolism and cause health problems.Slide10

Heat Illness

Heat fainting-

It may occur as a result of

vasolidation,pooling

of blood in dependent

extremeties,reduced

.

Reduced blood volume (from dehydration ) result in reduced cardiac output.

It is not associated with an elevated body temperature.Slide11

Heat exhaustion-

There is a complex symptoms of

fatigue,headache,nausea

and giddiness.

Heat exhaustion occurs as a result of either dehydration and/or electrolyte depletions.Slide12

Heat cramp-

If the electrolytic balance of body fluids is sufficiently perturbed then painful muscular contraction occur in the

arms,legs

and abdomen.

This may occur by salt deficiency or drinking

lar

amounts of water following dehydration.Slide13

Heat rash-

Heat rash is caused by sweat duct obstruction and results in sweat retention within the gland.

This may result in infection or more commonly rupture within the skin with an inflammatory

respponse

result.

Sunburned skin and

occulsive

clothing interfering with free evaporation of sweat

increse

the risk of this condition.Slide14

Heat stroke-

This is a life threatening medical

condition.Symptoms

include altered mental status and core body temperatures above 40 degree

celcius

.

It occurs when the body’s thermoregulatory mechanism is overwhelmed by internal or external heat load and results in increasing core temperature.

Multiple organ failure or

distruption

of function is common and

shoul

be expected.Slide15

Improving the environment

The first step must be to reduce the impact of the environment,

ie

reducing effective temperature by engineering controls.

Provision of good quality air

Careful attention should be paid to the position and timing of ventilation connections, and the

minimising

of leakages between intake and return

outbye

, to

maximise

the quantity of air reaching the

inbye

workings.Slide16

Siting

of equipment that generates heat

Static equipment that generates heat should be kept sited either in the return airstream or in cross cuts.

Such equipment includes conveyors, as detailed above, compressors, pumps, and electrical switchgear, particularly transformers. Slide17

Use of equipment

A common source of excess heat is equipment that has been left running when not required.

Equipment should also be selected for the duty to be performed .

The selection of fire resistant hydraulic fluids can also have an effect on machine running temperature. Slide18

Control of water to

minimise

humidity

This can be achieved by eliminating standing water and by

minimising

the amount of water that is introduced underground .

Slide19

Artificial cooling

Air coolers remove heat from the passing air, but then dump that heat elsewhere. The plant is an additional heat source, but its use must be considered as part of the control measures.

Chilling the water supply underground is also worth considering. Slide20

CASE STUDY

:

The Granites Callie Mine - Australia

INTRODUCTION

-

Mineral : Granite

Production-2.1

Mtpa

Depth- 1000 m

Final Expected depth-1800 m

Mining Method:

Longhole

open

stoping

Slide21

Severe heat condition in mine

The mine heat load includes auto-compression, heat flow from rock and fissure water, heat released by the operation of electrical and diesel powered equipment.

The mine geothermal gradient is approximately 2°C/100 m resulting in 50°C rock temperature at the base of the mine.Slide22

FUTURE INFRASTRUCTURE

source--

www.deep

mining

2012.com/data/page/6998/5_howes.pdf

Slide23

COOLING REQUIREMENT-

Assuming an overall cooling requirement of 12500

kWR

, for an average mine airflow of 675 m3/s, the amount of cooling required is 18.5

kWR

/m3/s. The average mine cooling required is expected to average 10000 kW or 14.8

kWR

/m3/s.

.Slide24

WET AND DRY CONDENSING METHOD

Firstly condensers of a refrigeration plant remove heat from the refrigerant.

The refrigerant gas discharged from the compressor is superheated

Condenser cools it initially to the condensing temperature and then to a fully condensed liquid refrigerant in the condenser.Slide25

CONCLUSION

Heat Stress affects the mental condition of workers , hence affects the production.

The best solution to control heat is to use available technologies.

Better heat conditions in mine reduces mine accidents.Slide26

REFERENCES

Dresosti

A.O.,Problems

arising out of temperature and humidity in deep mines of the

Witwaterstand.Mine

society of

S.Africa

,vol.36:pp 102-129 retrieved from

http://www.minetech.com/technology/miningheat/

visited on 29 august 2011

Polton,E.C.,Environment

and human efficiency.vol 1:pp 204

McPherson M.J.,

Subsurface Ventilation and Environmental

Engineering,chapter

17-18:pp 680-749

http://www.geoexpro.com/technology/miningheat/

Date:1 sep 2011

www.hse.gov.uk/pubns/

mines

07.pdf

Date:30

aug

2011

http://www.sciencedirect.com/science/article/pii/037663497790013X

Date:30

aug

2011

www.deep

mining

2012.com/__data/page/6998/5_howes.pdf

Date:1 sep 2011