CLARIFLOCCULATOR
DESCRIPTION UNIT INPUT CALCULATED RANGE
VALUE VALUE
Floculator
Dimensionless parameter, G.t 54000 2-6x104
Detention time required mim 30 30-60
Liquid depth m 3.00 2.5-4.5
Calculated from dia of floccu.and
Volume required m3 492 assumed central shaft dia of 1200
Volume provided m3 492
Calculated from given dia of flocc.. and
Design Flow m3/hr 984 assumed detention time of 30min
Design flow m3/sec 0.273
INLET ARRANGEMENT
Velocity in the Central RCC Shaft m/sec 0.6 0.5-1.0
Required diameter of the central shaft mm 761.60
Diameter of the central shaft Provided mm 800
Diameter of Center column mm 1200
GO AHEAD
Free board mm 500 300-500
Area of Floculator m2 164.00
Diameter of Floculator zone required m 14.400
Diameter of Floculator zone provided m 14.50
Velocity of flow m/sec 0.6 0.2-0.8
Velocity gradient (G) S-1 30 10to75
Absolute viscosity of water (u) at 20degree Ns/m2 0.00089
Power W 394.1
Drag coeff.of blades (Cd) 1.8 1.8
Velocity of the tip of blades (V) m/sec 0.55
Velocity of water at the tip of blade m/sec 0.14
Density of water kg/m3 1000
Area of Blades (Ap) m 2
6.24
Ratio of total area of Blades to 1 0.156 0.10-0.25
Cross sectional area of tank % 15.635
Provide 16 Nos. of paddles, Area of each paddle m2 0.39
Height m 1.3
Width m 0.30
Two shafts will support 16 paddles, each shaft supporting 8 paddles.
Flocculator shaft speed (Ref Mechanical design rpm 9
as in BSBK)
Distance of paddle edge, r, from the centre line of vertical shaft is given by the equation.
V = 2*3.14*r*n/60
r m 0.58
The flocculator shaft distance from the centre line
of the Clariflocculator (1.5 times the diameter of
the impeller + radius of the central column) 2.35
Clarifier
Assume a surface overflow rate of 37m3/m2/day
Surface area of Clarifier m2 638.27
Diameter of the Clariflocculator, Dc is given by
3.14/4(Dc^2-14.8^2)=638.27 m 32.12
say 32 m
Provide Outside launder having width of 0.5m and wall thickness of 0.1m
Available weir length m 100.5
Weir loading rate m /m/day
3
234.91
<300 m3/m/day
OK
Mechanical design of Flocculator
Power per Flocculator (2Nos) W 197.05
Power P/ Efficiency of GB assumed = 2 X 3.14 X N X T / 60
Torque T N.m 84.61
Safety factor 1.5
Required torque 126.91
A237 Radicon single reduction gearbox (ratio 50:1) which is having output torque of 180 N.m
is selected initially.
Shaft handling RA, FOOT 1 IN POSITION 1.
Gearbox efficiency:
Output torque of the slected gearbox N.m 180 From Catalogue
Output speed rpm 30 From Catalogue
Output power (Po) w 565.49 Power P = 2 X 3.14 X N X T / 60
kw 0.57
Input power (Pin) kw 0.82 From Catalogue
Gearbox efficiency 0.69
The calculated efficiency (69%) is less than the assumed value (80%).
we have to reconsider the GB selection.
Torque T N.m 98.09
Safety factor 1.5
Required torque N.m 147.14
A237 Radicon single reduction gearbox (ratio 50:1) which is having output torque of 180 N.m
is confirmed finally.
Shaft handling RA, FOOT 1 IN POSITION 1.
Power per Flocculator
required/(Efficiency of the GB*Efficiency
Motor Power: HP 0.52 of the Bevel gears)*15% motor margin
HP say 0.75
Design of Intermediate Shaft:
Torque required T N.m 98.09
Max. Torque Mt N.m 127.52
Radial force N 218.52 Maximum torque / Radius of the Flocculator
Bending Moment (Mb) N.m 607.49 Radial force X (Over hang = 2.78m)
Select Kb=1.75, Kt=1.25 from the PSG Design data book.
M = SQRT((Kb.Mb)^2+(Kt.Mt)^2)
M N.m 1075.00
Take Allowable stress = 500kg/cm2
M=3.14*(shaft dia ^ 3)*Allowable stress/16
Shaft diameter cm 4.81
mm 50
Z value for solid shaft 24.54 3.14*(Shaft diameter^3)/16
Select suitable hollow shaft from the table.
80NB Light Mild steel tube having OD of 87.9 & 3.25mm thickness whose Z value is 35.28, is selected.
The selected steel tube is having weight of 6.81kg/m
Flash mixer
Tank size m 1.75 Given
Liquid depth m 3.50 Given
Actual volume of water m3 10.72
G.t 18000 Constant
Velocity gradient (G) S-1
300
Absolute viscosity of water NS/m2 0.001
Power input to water w 858.57 G2 x Absolute viscosity x volume
Motor power w 1097.06
HP 1.46
HP say 1.50
Diameter of the Impeller required m 0.58
Diameter of the Impeller provided (d) m 0.58
Density of water kg/m3 1000
Power consumed by the Impeller (P) w 858.57
P = Power no. X Density X (Impeller speed in rps)^3 X (Impeller dia. in m)^5
Where, Power no = 1.6 for Pitched blade turbine, 4.5 for Turbine impeller
Normally we are providing Pitched blade turbine.
From the above equation, we can calculate the speed of the impeller.
N rpm 120.87
Provide ABB 1.5 HP motor, 1410 rpm
Gearbox ratio 11.62
Next Available GB ratio in Catalogue 15
Therefore Actual speed of the Impeller (N) rpm 93.67
Power P/ Efficiency of GB assumed = 2 X 3.14 X N X T / 60
Torque T N.m 102.98
Safety factor 1.50
Required torque 154.47
A237 Radicon single reduction gearbox (ratio 15:1) which is having output torque of 186 N.m is selected.
Gearbox efficiency:
Output torque of the slected gearbox N.m 186.00 From Catalogue
Output speed rpm 100.00 From Catalogue
Output power (Po) w 1947.79 Power P = 2 X 3.14 X N X T / 60
HP 2.60
Input power (Pin) HP 3.00 From Catalogue
Efficiency of the Gearbox 0.87
The calculated efficiency (87%) is almost equal to the assumed value (85%). Hence no need to recalculate the motor power required.
Design of Intermediate Shaft:
Torque required T N.m 102.98
Max. Torque Mt N.m 133.87
Radial force N 461.63 Maximum torque / Radius of the Impeller
Bending Moment (Mb) N.m 877.09 Radial force X (Over hang = 1.9m)
Select Kb=1.75, Kt=1.25 from the PSG Design data book.
M = SQRT((Kb.Mb)^2+(Kt.Mt)^2)
M Kgf.m 157.39
Take Allowable stress = 500kg/cm2
M=3.14*(shaft dia ^ 3)*Allowable stress/16
Shaft diameter cm 5.43
mm 55.00
Z value for solid shaft 32.67 3.14*(Shaft diameter^3)/16
Select suitable hollow shaft from the table.
80NB Light Mild steel tube having OD of 87.9 & 3.25mm thickness whose Z value is 35.28, is selected.
The selected steel tube is having weight of 6.81kg/m
