7Calculation of pressure and quantity

measurement

PRANJAL SAO

GENERAL HEADING OF VENTILATION SURVEY

AIR QUANTITY SURVEY

PRESSURE QUANTITY SURVEY

TEMPERATURE SURVEY

AIR QUALITY SURVEY

Importance of ventilation survey

Check and supply of air

Detection of leakage

Size of airways Alteration in

magnitude and course of airways

Ventilation for control of fire and other explosion

Quantity Requirement

1> AIR REQUIREMENT IN THE WORKINGS

2>AIR REQUIREMENT IN DRIFTS AND TUNNELS

PRESSURE REQUIREMENT

1> OBTAIN A PRESSURE GRADIENT ALONG THE CIRCUIT 2> DETERMINING THE VALUES

OF FRICTION FACTOR FOR VARIOUS TYPES OF AIRWAYS

AIR REQUIREMENT IN THE WORKINGS:-

SUPPLYING THE WORKERS WITH BREATHABLE AIR

DILUTING IMPURITIES IN MINE AIR TO SAFE CONCENTRATIONS

DILUTING HEAT AND HUMIDITY OF MINE AIR

Supplying the workers with breathable air

MINE AIR SHOULD ONTAIN AT LEAST 19% O2 A MAN NEED ABOUT 0.125 M3MIN. CO2 SHOULD BE 0.5%

DILUTING IMPURITIES IN MINE AIR TO SAFE CONCENTRATIONS

1>THE DILUTION OF METHANE IS THE DETERMINING FACTOR IN

MINES .2>DGMS RECOMMENDS TO

KEEP THE INFLAMMABLE GASES BELOW 0.75%.

3>IF ELECTRICAL APPARATUS ARE USED METHANE SHOULD

KEPT BELOW 0.5%

THE RATE OF AIR FLOW Q REQUIRED TO DILUTE THE

METHANE

GAS IN INTAKE AIR + GAS ADDED IN THE WORKINGS = GAS IN EXHAUST AIR

Q ×a +q =( Q + q) cQ = q/(c−a)−qc/ ( c−a) m3 /min

a = concentration of gas present in intake air

q = rate of gas emission m3 /min

IF THE MINE IS TO BE PLANNED FOR DEPTHS FOR WHICH NO METHANE EMISSION DATA CAN BE OBTAINED , IT WOULD BE WISE TO ALLOW A 10 % INCREASE IN THE RATE OF GAS EMISSION FOR EVERY 100M DEPTH . RADON DOUGHTERS [RADIOACTIVE MINERALS ] :-- MAXIMUM PER LIMIT = 1/10 U Ci/m3 1 Ci = 37 BILLION DPS 1mCi = 37000DPS . MINIMUM 0.5 M3/S SHOULD BE DELIVERED FROM A TUBE OUTLET AT A INSTANCE NOT EXCEEDING 9M FROM FACE FOR EVERY PAIR OF MAN MINING URANIUM CORE

DILUTING HEAT AND HUMIDITY OF THE MINE AIR

1>It is difficult to estimate the quantity of air necessary to reduce the temperature of air at

the face , This depends on many factors . 2> heat from sources like machines , men etc

are easily measurable .3> heat due to spontaneous heating is more

difficult to estimate Q = ( q × p ×dL )/ (Ad ×Cp×dT)

Q = quantity of air flowing per unit time

q = rate of heat transfer from strata to air

P= perimeter

dL = length of airway

dT =rise in temperature

At Ventilation shaft with no winding equipment = 15m/s

At Ventilation shaft only used for mineral hoisting = 12m/s

At Ventilation shaft for man winding and haulage road = 8m/s

other roadways = 6m/s

conveyor roads ,loading pits = 4m/s

working faces in development ,depillaring = 4m/s

PRODUCING SUFFICIENT FACE AIR VELOCITY FOR COMFORTABLE

WORKING CONDITIONS1> FACE VELOCITY OF 0.5 TO

2.0 m/s FOR COMFORTABLE WORKING

2> VELOCITIES ABOVE THIS

CAUSE DISCOMFORT

3> FLOW AT FACE SHOULD BE TURBULENT

AIR REQUIREMENT IN DRIFTS AND TUNNELS

AIR QUANTITY USEDAT DRIFTS AND TUNNELS IS GREATER TO CLEAR THE GASES • EXTREMELY HOT FACES 0.75 M3 S-1 PER

M2 IS USED

IN HIGHLY GASSY COAL HEADINGS , TO DILUTE THE METHANE • IN ANY CASE QUANTITY OF 6 m3

min -1 per man

T = 2.303 (Vin/Q) Logq/(Vm.C)+(V-Vm)/QVm =vol of tunnel mixing of gases produced at face

q = total volume of noxious gas m = mass of noxious gas

q’ = vol of noxious gas produced V= vol to tinnel

C= conc at time t

CALCULATION OF RATE OF CH4 EMISSION FROM BROKEN COAL

Iu = b .r.t (Xo −X1) M3/MIN

B = WIDTH OF COAL FACE IN METRE

R = RATE OF FACE ADVANCE M/MIN

T = BULK DENSITY OF COAL TONE/M3

Xo, X1 = ACTUAL AND RESIDUAL METHANE %

AMOUNT OF AIR REQUIRED

Qz = 100.Iu/ (C−Co) M3/MIN

Iu = RATE OF METHANE EMISSION IN PHASE AFTER 30 MIN AFTER BLASTING

M3/MIN

C , Co = PERMISSIBLE GAS CONCENTRATION AT FACE AS INTAKE

CALCULATION OF AIR RERQUIRED ON THE BASIS OF EMISSION AND NOXIOUS GAS

WITHDRAWLQz = W/ (Kt.To ) In ( 100 Imax To + Co .W)/CW

M3/MIN

W= VOL OF MIXING ZONE BOUNDED BY THE END OF VENTILATION PIPE AT THE FACE M3

Kt = COEFFICIENT OF TURBULENT (= 0.4)

To = TIME WHEN MAXIMUM METHANE CONCENTRATION IS OBSERVED AT PHASE

IMMEDIATELY AFTER BLASTING IN MINUTES

Imax = MAXIMUM METHANE OUTPUT IN FACE ZONE M3/MIN

QUANTITY ESTIMATION BASED ON NITROUS FUMES AFTER BLASTING

Qz = 17 S/T √Ψ .B.b/s M/MIN

T = PERIOD OF UTILIZATION IN MIN

B = AMOUNT OF EXPLOSIVES BLASTED IN 1 TIME TAKEN AS EQUAL TO 100/Kg FOR COAL ,

40 Kg FOR ROCK

Ψ = SIZE OF COEFFICIENT OF WETNESS

B = WIDTH OF COAL FACE

QUANTITY ESTIMATION BASED ON DUST FACTOR

Qz = SVo 60 M3/MIN

S = CROSS SECTION AREA M2

Vo = OPTIMUM RATE OF FLOW

BASED ON OUTPUT ( COAL ) Qz = 2.5 (Td)M3/MIN

Td = DAILY OUTPUT IN TONNE

RATE OF AIR FLOW

MINE WORKING

MINIMUM POSSIBLE

OPTIMUM POSSIBLE

MAXIMUM POSSIBLE

ROBBING FACE

0.9 1.6 3.0

DEVELOPMENT FACE

0.3 0.6 -

DRIVE WITH CONVEYOR TOP POINT

0.7 1.3 1.8

FOR DEPILLARING AREA

Q = 100 Iz N / ( C− Co ) M3/MIN

Iz = MEAN METHANE EMISSION FROM PILLAR RIB IN M3/MIN

N = COEFFICIENT EQUILIBRIUM OF METHANE EMISSION

C = PERMISSIBNLE GAS CONC IN RETURN

Co = PERMISSIBLE GAS CONC IN INTAKE

VALUE OF NMINING METHOD

ADVANCING FACE M/DAY 1.4 --- 2.0

OVER 2.0

CUTTING MACHINE

1.8 ---2.2 1.4 ---1.8

PICK HAMMER 1.1--- 1.3 1.0 ---1.1

TOTAL QUANTITY OF MINE

Qsh = [ ∑ Qut.sch + 1.1 ( ∑ Qp + ∑Qo .v + ∑ Qk + ∑Qut) ] Kz-u

Qut.sch = AIR REQ TO VENTILATE IN A DISTRICTQp = VENTILATON OF DEVELOPMENT FACE

Qov = VENTILATION OF ISOLATED WORKING Qk = AIR FOR ROOMS OUTSIDE THE DISTRICT

Qut = LOSSES THROUGH VENTILATION DEVICES

LEAKAGE OF AIR

BETWEEN THE FAN AND THE FACE IN A MINE A LOT OF AIR IS LOST

THROUGH LEAKAGE .THE VOLUMETRIC EFFICIENCY OF

DISTRIBUTION OF AIR IN MINES VARY FROM 10 % TO 85% .

UNDER AVERAGE CONDITIONS 45% TO 55% OF AIR IS CIRCULATED BY

THE FAN

LEAKAGE ACROSS NEWLY FORMED GOAF

DISTANCE BETWEEN INTAKE AND RETURN GATES

LEAKAGE ACROSS GOAF AS PERCENTAGE OF AIR ON THE FACE

45 20

90 10

180 5

FAN drift pressure Leakage at pit top

1.25 11.7

2.50 16.3

3.75 21.0

5.00 23.3

6.25 25.7

PRESSURE REQUIREMENT

THE PRESSURE GRADIENTS AIDS IN DETERMINING REGIONS OF EXCESIVE RESISTANCE AND

FEASIBILITY OF CORRECTING THE CONDITIONS.

IF THE MINE CONSISTS OF SEVERAL PARALLEL SPLITS , THE PRESSURE REQUIRED FOR THE ONE

WITH THE LARGEST RESISTANCE IS GENERALLY TAKEN AS THE ACTUAL PRESSURE REQUIREMENT

THIS INVOLVES THE CONTROL OF QUQNTITIES FLOWING THROUGH THE OTHER SPLITS BY THE INSTALLATIONS OF REGULATION IN THEM .

INSTALLATION OF REGULATORS IS A SIMPLE MEANS OF VENTILATION CONTROL AND SHOULD BE ADOPTED IF THE DEGREE OF REGULATION AFFETS ONLY A MINOR NUMBER OF SPLITS

CALCULATION OF RESISITANCE OR PRESSURE LOSS

P = RQ.Q

TOTAL RESISTANCE = FRICTION LOSS + SHOCK RESISTANCE

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