C H A P T E R
F I V E
A belt conveyor must be designed, constructed and maintained so that the belt consistently runs
centrally on its mechanical system of idlers and pulleys. To accomplish this, the following conditions
must prevail:
1. Square the tail and head pulleys with the conveyor frame.
2. Square all idlers and returns with the conveyor frame; be sure they are in line and lie in the same
horizontal plane; and tighten the attachment belts.
3. Level all frames to ensure a cross-section parallel to the ground plane. If one side of the
conveyor frame is lower than the other, gravity will force the belt off-center.
4. The belt must be straight and the belt splice square. If side creep occurs only in the vicinity of
the belt splice, the splice may not be square with the belt. In general, if the creep follows the
belt, there is a problem with the belt. If it remains in one general area, there is a problem with
the system.
5. The belt should have good contact with all troughing rolls.
6. Load material centrally on the belt.
B E LT C O N V E Y O R I D L E R S
Belt Alignment
Refer to Appendix D for information on CEMA Conveyor Installation Standards. There may be times
when the above procedure is not sufficient and the belt persistently runs to one side. The following
corrective measures may be initiated to prevent side creep:
1. While running the belt at the lowest speed possible, find the point of maximum side creep. The
idler preceding this point along the direction of belt travel can be adjusted to minimize side
creep. Facing the conveyor from the tail end, the idler must be pivoted clockwise to correct side
creep on the left and counterclockwise to correct side creep on the right. Once the belt is
centered, change to a higher speed (if possible) and load the belt with material. Continue
adjusting until normal operating conditions do not cause the belt to misalign.
2. If creep persists, insure that the head and tail pulleys are perfectly aligned. Steer the belt with
the carrying or return idlers. See Figures 5.10 and 5.16.
3. Training idlers can be installed to replace troughing or return idlers. They should only be used in
problem systems and should be at least 50 feet from any terminal or bend pulleys. Do not use a
training idler in a vertical curve. Reversible belt training idlers are available for reversible belt
conveyors. Free rotation of the training idler’s vertical bearing is essential for satisfactory
tracking results.
4. If creep still persists, some or all of the troughing idlers may be tilted not more than 2 degrees
from the vertical, in the direction of belt travel. See Figure 5.21.
5. If none of the above steps solve a belt misalignment condition, the conveyor should be laser
aligned and corrective action taken based upon the survey data.
NOTE: Maximum tracking effect occurs when the distance between the corrective components and the
following components is maximized.
89
B E LT C O N V E Y O R I D L E R S
CHAPTER FIVE
Belt Alignment Cont.
Table 5.41
Average weight (lbf)
of troughing idler
rotating parts –
steel rolls
Table 5.42
Average weight (lbf)
of return idler
rotating parts –
steel rolls
Table 5.43
WK2 (lbf-in2) average
for three equal-roll
troughing idlers
Table 5.44
WK2 (lbf-in2) average
for single steel
return idlers
90
Belt
Width
CEMA Idler Class
(in)
B4
B5
C4
C5
C6
18
24
30
36
42
48
54
60
72
84
96
15.0
18.3
21.8
25.3
30.8
32.9
19.2
24.2
28.3
33.0
38.1
41.6
14.5
17.5
20.5
23.5
26.5
29.5
19.1
23.2
26.8
31.3
35.2
39.3
45.9
50.1
26.7
32.6
38.0
43.6
49.2
54.8
62.3
68.3
Belt
Width
D5
D6
23.2
26.8
31.3
35.2
39.3
45.9
50.1
57.9
32.6
38.0
43.6
49.2
54.8
62.3
68.3
77.8
E6
E7
F6
F7
F8
64.8
73.3
81.9
93.6
102.2
119.4
132.0
145.3
81.8
91.7
101.3
121.8
132.7
154.5
164.0
173.0
143.0
169.0
195.0
221.0
162.0
191.0
219.0
248.0
180.0
211.0
243.0
274.0
E6
E7
F6
F7
F8
59.0
67.4
75.6
83.2
92.2
109.4
114.0
122.0
70.0
80.1
89.9
99.9
109.4
129.0
136.2
149.8
132.0
156.0
181.0
205.0
148.0
175.0
202.0
229.0
163.0
192.0
222.0
252.0
E6
E7
F6
F7
F8
446
502
564
628
689
811
985
1114
801
876
1017
1127
1234
1451
1598
1804
838
967
1095
1224
1278
1481
1695
1921
1901
2208
2532
2870
E6
E7
F6
F7
F8
419
479
539
597
659
779
933
1074
750
857
963
1070
1177
1391
1581
1737
753
884
1014
1145
1171
1376
1582
1790
1760
2071
2382
2693
CEMA Idler Class
(in)
B4
B5
C4
C5
C6
18
24
30
36
42
48
54
60
72
84
96
13.1
16.3
19.5
22.7
26.0
27.4
16.3
20.9
24.5
28.5
33.0
36.1
12.2
15.2
18.2
21.2
24.6
27.6
16.6
20.1
24.0
28.0
32.1
36.1
21.6
27.1
32.3
37.6
43.3
48.4
Belt
Width
D5
D6
20.9
25.8
30.1
34.3
38.7
43.4
49.2
55.1
30.1
35.4
40.5
47.2
54.4
60.8
68.1
74.9
CEMA Idler Class
(in)
B4
B5
C4
C5
C6
18
24
30
36
42
48
54
60
72
84
96
43
53
65
78
90
104
90
116
140
161
185
207
45
56
67
79
91
105
90
116
140
161
185
207
223
245
179
224
269
313
358
400
447
493
Belt
Width
D5
D6
116
140
161
185
207
223
245
266
224
269
313
358
400
447
493
538
CEMA Idler Class
(in)
B4
B5
C4
C5
C6
18
24
30
36
42
48
54
60
72
84
96
41
50
61
72
83
94
85
106
128
152
174
196
42
51
61
72
83
94
85
106
128
152
174
196
165
210
254
312
348
385
D5
D6
106
128
152
174
196
218
234
256
210
254
312
248
385
429
473
513