Tel: +27 (0)11 864 1643 Fax: +27 (0)11 908 5728 E-mail:
[email protected]
conveyor pulley design There are many elements to consider during the design o a conveyor pulley. The most important however is the design o the shats. Other elements that need to be considered are the pulley diameter, the shell, the hubs and the locking elements.
1.3 caat mmt M = ^ Bearing center - Pulley faceh $
Combined torsion:
Te =
Combined bending: Me = 1.0 shaft
2
Tres $ K b 4
2
T -M
1 ^ M + Teh 2
1.4 caat haft There are three main actors that inuence shat design. Bending rom the tensions on the conveyor belt. Torsion rom the drive unit and deection. The shat thereore needs to be designed considering all three o these elements. For the design o the shat, based on bending and torsion, a max stress is used. This stress varies according to the material that is used or the shat or according to the max stress allowed by the end user. Typical allowable stresses, or the most commonly used shat material, are: 43 MPa or BS970 070M20 ( EN3 ) 55 MPa or BS970 080M40 ( EN8 ) 83 MPa or BS970 709M40 ( EN19 ) For the design according to maximum stress the ollowing needs to be considered:
To calculate the shat size rom the above, the Guest (equivelent bending) and Rankine (equivalen torsion) ormulas need to be considered. 16000 $ Te Torsion based diameter: Dg = 3 mr
Bending based diameter: Dr = 3
32000 $ Me vr
For the above ormulas σ and � are taken to be equal since the allowable direct stress ( σ) is a atigue case and the shear stress λ) (λ) is not. The third calculation determines ree shat deection limit. This limit ensures that there is no excessive deection o the shat at the point where the bearings and the locking elements are ftted. The industry standard is 0.0015 rad to 0.0017 rad max allowable deection. Deection based diameter: Dd = 4
W $ a $ L $ 16000 E $ r $ a
The largest o the three possible diameters should be chosen and then rounded up to the next standard shat size. Denitions:
The industry uses additional saety actors or shat design, as ollows:
P =
Absorbed power (kW)
n
Rev / min (rpm)
=
D λ
=
σ •
Load Factor (Kb = 1.5 to 1.75) and; Torque Factor (Kt = 1.25 to 1.4)
=
=
Pulley diameter (m) Shear stress (MPa) Direct stress (MPa)
�=
3.142
W=
Nett tension without K b (KN)
1.1 caat tq
a
=
Bearing center to hub distance (mm)
Teff = T1 - T 2 (Calculate eective torsion)
L
=
Hub spacing (mm)
•
T =
Teff $ Kt $ D 2
or
T
=
P $ 9550 $ K t n
(Calculate absorbed torque)
From the above, use the greater value o torque to input into subsequent calculations.
E α
=
=
Young’s modulus or shat (N/mm 2) Allowable deection (radians)
β =
Wrap angle (degrees)
T eff
Eective tension (KN)
T res
Resultant tension (KN)
1.2 caat tat f
{=
2 $ r (90 -
Tres =
360
b ) 2
(Calculate resultant wrap angle)
^T1 $ Sin{ + T2 $ Sin^- {hh2 +^T1 $ Cos{ + T2 $ Cos^- {hh2 (Calculate resultant torsion) 181
Tel: +27 (0)11 864 1643 Fax: +27 (0)11 908 5728 E-mail:
[email protected] The table below gives a guideline on recommended pulley diameters, standard pulley ace widths and bearing centers using belt widths rom SABS 1669. 900 1050 1350
1050 1200 1700
1200 1350 1850
1350 1500 2050
1500 1700 2300
1800 2000 2600
2100 2300 2900
2400 2600 3200
10
9
8
7
16 22 30 41
14 20 28 37
13 19 26 35
12 16 22 30
10 14 19 25
54 70 88 112 138 170 250 340 430 535 660
49 64 81 100 130 155 230 320 430 535 660
45 60 75 95 120 145 210 300 410 535 660
40 50 65 82 100 125 185 260 360 480 640
35 45 55 70 90 110 160 230 310 420 560
A t sAns 1669
Bt Fa B ct
p damt 200
shaft da/ p da 100 / 315
21
18
16
13
10
250 315 400 500
110 / 400 120 / 400 130 / 400 140 / 500
30 45 60 80
26 37 51 70
23 33 45 60
19 27 37 50
630 800 1000 1250
150 / 500 160 / 500 170 / 630 180 / 630 190 / 630 200 / 630 220 / 800 240 / 800 260 / 800 280 / 1000 300 / 1000
100 119 144 170 200 235 313 405 515 640 790
90 119 144 170 200 235 313 405 515 640 790
80 105 133 165 200 235 313 405 515 640 790
66 86 110 138 170 210 285 370 470 585 720
1650 1850 2450
rtat t (kn)
The recommended shat sizes are calculated using 55MPa stress, 0.0015 rad defection and no torque. This table is to be used as a guideline only. only. 2.0 p
Pulley is normally used or heavy duty applications The T-Bottom Pulley is with shat diameters o 200mm and bigger. The main eature o this construction is a ace welded pulley and thus the shell to hub weld is moved out o the high stressed area at the end plate
There are various actors inuencing the pulley diameter. diameter. The pulley diameter is mainly determined by the conveyor belt class, but the required shat diameter also inuences the diameter. diameter. A golden rule or the pulleys diameter is that it should be at least three times the diameter o the shat. 2.1 p T There are two main types o pulleys i.e. the Turbine Turbine pulley and the TBottom Pulley. Pulley. In both these types o pulleys the shat is removable or easy maintenance. The Turbine Pulley is well suited or low to medium duty applications with a hub designed to allow or exing, thus preventing high stresses on the locking assemblies or welds.
2.2 p w •
•
Full Crown: From the centre line o the pulley with a ratio o 1:100 Strip Crown: Crown rom the frst and last third o the pulley ace with a ratio o 1:100
Crowning is normally only done on specifc request. 2.3 la Various types o lagging can be applied to the pulley i.e. rubber lagging, ameproo (neoprene) lagging or ceramic lagging. 182
