GOVERNMENT COLLEGE OF ENGINEERINGTIRUNELVELI

DESIGN PROJECT

DESIGN OF SCREW CONVEYOR

GUIDED BYDONE BYMrs.SUPRIYA (AP, GCE)RAJESH M 13MEED1511 950813408011

Screw flight development

We selected sectional flight screw The outside diameter of screw = 304.8mmThe inside diameter of the screw=101.16mmDevelopment of outside diameterA==A= 1004.87mmDevelopment of inside diameterB==B= 441.33mmThe developed inside radius of the flight will be= = 1.2769r= 220.667mm Conveyor length =1m+ 2*pitchFor one meter length= 1000+ 2(304.8)=1609.6mmNo. of flights= = 5 flightsThickness of flight= 6.35mmMaterial = Mild steel(ms)

Calculation of various loads acting on screw conveyor:1. Load due to coalCoal bulk density = 61 * 16.018= 977.098 kg/m3

LetV = volume in which coal loads acts downwards (i.e. on the center pipe)

V = [(width of trough) * (height of end plate above center pipe)] (0.5* volume of hollow pipe)

Width of trough = 330.2mm = 0.3302m

Height of end plate above center pipe = 196.85mm = 0.19685m

Volume of hollow pipe = 0.785[(101.16)2 (88.9)2]

= 1.899*106 mm3

= 1.8918*10-4 m3

V = (0.3302*0.19685) (0.5*1.8918*10-4)

= 0.06499 9.459*10-4

= 0.0648 m3

We know thatBulk density = Mass / volume

Mass = 0.0648 * 980.941

= 63.56kg

The weight of coal = 63.56*10

W1= 635N

2. Load due to flights

Volume of one flight = 3.142/4 * (D0*D0 Di*Di) thickness = 0.784(0.3048*0.3048 0.1016*0.1016)* 0.00635 = 0.785(0.0929 -0.01032) * 0.00635 = 4.11640*10-4m3Mass of flight = 5 * density * volume = 5*7800*4.1164*10-4 = 16 kg/mW2 = 160 N/mAdding 1 & 2Total UDL on 1m length = 635+160= 795 N/mTaking 50% overload to be on safer sideUDL= 1192.5 N/mLoad fluctuations may come due to dynamic loadingTherefore increasing UDL say = 1200 N/m

3. Load due to each solid shaft

a) Drive end shaft diameter = 76.2mm

= 0.7853*0.0762*0.0762*0.508

= 0.7853*2.94967*10-3

= 2.3163*10-3 m3

Density = Mass / volume

Mass = 2.3163*10-3 * 7800

= 18 kg

W3 = 180 N

b) Coupling shaft diameter = 76.2mm

= 0.784*0.0762*0.0762*0.20955

= 9.55*104m3

Mass = 7800*9.55*10-4

= 7.45kg

W4= 74.5 N

4. Load due to hollow pipe

Mass = volume * density

= 0.785(0.10162 -0.08892)*7800

= 14.81kg

Taking 60% overload to be on safer sideM= 23.696kg

Considering this also as UDL of 240 N/m

Total UDL= 1200+240= 1440N/m

Bearing selection (End bearing)

We select SKF 6216 deep groove ball bearing is selected based on the shaft diameter 76.2mm from the PSG data book

The static load C0 = 4550kgf

The dynamic load C = 5700kgf

Maximum permissible speed (rpm) = 5000rpm

Assume life required to be 10,000hrs

90% probability of survival

Life in million revolution = L*60*N/ 1000000

= 10000*60*53.29/1000000

= 31.974 million revolution

The equivalent load P = [X.Fr+Y.Fa]*S

Where X = radial factor Y = Thrust factor S = Service factor

Fa/ Co = 635/4550 = 0.1395

From the PSG data book

e = 0.31

Fa/Fr= 635/345 = 1.840 > e

The radial factor X = 0.56

Thrust factor Y = 1.4

P = [0.56(345) +1.4(635)]*1.2

= (193.2+88.9)*1.2

= 1298.64N = 129.86kgf

The ratio c/p in the graph from PSG data book

C/P = 3.36

C= 3.36*1298.64

= 4363.43 N

= 436.34 kgf

The bearing SKF6216 is selected because in our case dynamic capacity is 436.34kgf.It be lesser than permissible dynamic capacity. So, bearing is very well safe.

Deflection calculation:

The deflection of the screw is given by

D =

Where W -Total weight of screw in pounds

L - Screw length inchesE - Modulus of elasticity

I - Moment of inertia (in)4

Here w =189 lbs

L = 132 in

E = 29,000,000 for low carbon steel

I = 4.788in4

For schedule 40 pipe

=

= 0.040 in = 1.1016mm

It is lesser than the allowable deflection 6.35mm.For schedule 80 pipe

= 0.0310in =0.787mm

As comparing the both schedule 40 & 80 pipe, the deflection is less than allowable deflection 6.35mm

Torque calculation:

Torque acting on the screw conveyor is given by the relation

= 63025 * motor horse power / N (rpm of the screw)= 63025* 3 / 54 = 3501.38 lbs. in= 3501.38*4.44*2.54

T= 395.60*103 N.mm

From the CEMA correspond to shaft diameter 3 = 76.2 mm. The calculated torque is less than the maximum allowable torque 15435 lbs. in under 2 bolts in shear and bearing.

Based upon the torque ratings as per CEMA the following dimension are selected to transfer the torque in safer.

The screw flight diameter = 12 = 304.8 mm

The shaft diameter = 3 = 76.2mm

Pipe outer diameter = 4 = 101.6mm

Inner diameter = 3 = 76.2mm

Selection of hanger

Corresponding to bearing material and characteristics We select 99A hanger. It is designed for maximum support and its slim design minimizes obstruction of material flow.

Corresponding to screw diameter 12 the dimension of the hanger bearing

A= 330.2mm B= 177.8mm C= 76.2mm D = 431.8mm E=50.8mm F=101.6mm G=25.4mm

H (Bolt Size) = 12.7mm K=9.525mmSelection of Motor and gear boxBased upon the horsepower calculation, we select 3hp, 415v, 3;50 Hz A/C squirrel cage induction motor is selected from Hindustan electric motor catalogue.

The speed of motor = 1425 rpmThe speed of conveyor = 57 rpmService factor = 1.2The output torque of the conveyor = 374.93 N-mThe step ratio = 25 Based upon the step ratio & input horse power the size 43 three stage inline helical gear unit is selected for screw conveyor.

Dimension of shafts and coupling bolt

Standard End Shaft

Based on shaft dia 76.2mmC=25.4mm D=76.2mm F=25.4mm G= 44.45mmH (bolt size) = 19.05mmM= 25.4mm N=7.93mmZ= 152.4mm

Drive shaft

Hanger end shaft

Based on shaft diameter 76.2mm, the hanger end shaft is selectedF=203.2mmG=76.2mmH (bolt) = 19.05mmL= 25.4mmM = 76.2mmN =25.4mmCoupling shaft

Troughs and coversWe selected U trough formed flange A= 330.2mm B=177.8mmC=50.8mm D=431.8mm

The dimension of cover D=431.8mm G=15.8mmInlet and discharge spout

The dimensions areB= 254mm C=203.2mm D=228.6mm K =4.76mm

Saddles and feet

Flange feet

Trough ends

EXPLODED VIEW OF SCREW CONVEYOR1. Screw6. Hanger11. Shaft seal2. Drive shaft7. Hanger bearing12. End plates3. Coupling shaft8. Discharge13. Internal collars4. End (tail) shaft9. Flange foot14.Coupling bolt5. Covers10. End bearing15. Bolt pads16. Cover clamps17.Inlet 18. U-Trough