pressure & quantity measurement
TRANSCRIPT
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7Calculation of pressure and quantity
measurement
PRANJAL SAO
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GENERAL HEADING OF VENTILATION SURVEY
AIR QUANTITY SURVEY
PRESSURE QUANTITY SURVEY
TEMPERATURE SURVEY
AIR QUALITY SURVEY
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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
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Quantity Requirement
1> AIR REQUIREMENT IN THE WORKINGS
2>AIR REQUIREMENT IN DRIFTS AND TUNNELS
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PRESSURE REQUIREMENT
1> OBTAIN A PRESSURE GRADIENT ALONG THE CIRCUIT 2> DETERMINING THE VALUES
OF FRICTION FACTOR FOR VARIOUS TYPES OF AIRWAYS
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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
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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%
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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%
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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
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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
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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
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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
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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
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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
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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
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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 %
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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CALCULATION OF RESISITANCE OR PRESSURE LOSS
P = RQ.Q
TOTAL RESISTANCE = FRICTION LOSS + SHOCK RESISTANCE
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