Page 131 - Root Cause Failure Analysis

Conveyors 119

Table 9-4 Factor A for Self-Lubricating Bronze Bearings

ConveyorDiameter,in. 6 9 10 12 14 16 18 20 24
Factor A 54 96 114 171 255 336 414 510 690
Source: Theodore Baumeister, ed., Marks’ Standard Handbook for Mechanical Engineers. 8th ed. (New
York: McGraw-Hill, 1978).

where

A = factor for size of conveyor (see Table 9-4);
c = material volume, ft3/h;
F = material factor, unitless (see Table 9-5);
L = length of conveyor, ft;
N = conveyor rotation speed (rpm);
W = density of material, Ib/ft3.

Table 9-5 Power Requirements by Material Group
Max. Cross-Section (a) Max. Density Max. rpm for Max. rpm
Material Occupied by the of Material 6-in. for 20-in.
Group Material Ob@) diameter diameter
1 45 50 170 110
2 38 50 I20 75
3 31 75 90 60
4 25 100 70 50
5 12 112 30 25
Group 1: F factor is 0.5 for light materials such as barley, beans, brewers, grains (dry), coal (pulv.), corn
meal, cottonseed meal, flaxseed, flour, malt, oats, rice, wheat.
Group 2: Includes fines and granular material. The values of F are alum (pulv.), 0.6; coal (slack or fines).
0.9; coffee beans, 0.4; sawdust, 0.7; soda ash (light), 0.7; soybeans, 0.5; fly ash, 0.4.
Group 3: Includes materials with small lumps mixed with fines. Values of F are alum, 1.4; ashes (dry),
4.0 borax, 0.7; brewers grains (wet), 0.6; cottonseed, 0.9; salt, coarse or fine, 1.2; soda ash
(heavy), 0.7.
Group 4: Includes semiabrasive materials, fines, granular and small lumps. Values of Fare acid phosphate
(dry). 1.4; bauxite (dry), 1.8; cement (dry), 1.4; clay, 2.0; fuller’s earth, 2.0; lead salts, 1.0; lime-
stone screenings, 2.0; sugar (raw), 1.0 white lead, 1.0 sulfur (lumpy), 0.8; zinc oxide, 1.0.
Group 5: Includes abrasive lumpy materials which must be kept from contact with hanger bearings. Val-
ues of F are wet ashes, 5.0 flue dirt, 4.0 quartz (pulv.), 2.5; silica sand, 2.0: sewage sludge (wet
and sandy), 6.0.
Source: Theodore Baumeister. ed., Marks’ Standard Handbook for Mechanical Engineers, 8th ed. (New
York: McGraw-Hill, 1978).