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This troughing idler selection procedure for calculated idler load does not include impact force on idler at loading points or the effect of belt transitions (head and tail pulley) on idler loado See Step No. 3 foe impact idler series selection. Contact your CEMA idler manufacturer for idler series selection for other loading conditions. Table 2-1 WB-Estimated average beIt weight muItiple and reduced ply belts. IbsJft. Material Carried. Ibs.lcu. ft. Selt Width (inches (b})

30-74

75-129

130-200

18

3.5

4

4.5

24

4.5

5.5

6

30

6

7

8

36

9

10

12

42

11

12

14

48

14

15

17

54

16

17

19

60

18

20

22

72

21

24

26

84

25

30

33

96

30

35

38

l. Steelcablebelts - increaseabovevalue by 50%. 2. Actual belt weights vary with different constructions, manufacturers, cover gauges, etc. Use the above values for estimating. Obtain actual values from the belt manufacturer whenever possible. Table 2-2 K1-Lump adjustment factor Material Weight, Ibs.lcu. ft. Maximum Lump Size

Onches )

50

75

100

125

150

175

200

4

1.0

1.0

1.0

1.0

1.1

1.1

1.1

6

1.0

1.0

1.0

1.1

1.1

1.1

1.1

8

1.0

1.0

1.1

1.1

1.2

12

1.2

10

1.0

1.1

1.1

1.1

12

12

1.2

12

1.0

1.1

1.1

1.2

1.2

1.2

1.3

14

1.1

1.1

1.1

1.2

1.2

1.3

1.3

16

1.1

1.1

1.2

1.2

1.3

1.3

1.3

18

1.1

1.1

1.2

1.2

1.3

1.3

1.4

Return idler series selection

Step No. 2

Calculated Idler Load (lbs.)

= CILR = (WB

x SI) + IML

Use CILR and select proper series of idler from Tables 2-11 through 2-14. CILR should be equal to or less than returo ¡dler rating. 31

'" ---

----

--- ---

----------

--- ----------

----

--

-~--

----------- ------

Step No. 3

~

.

Impact Idler Series Selection Q (S1/HR)

For homogeneous material without lumps:

~

~

Impact Force (lbs) = F = (0.1389)Q.../H

Centerof Gravity

f

Q = Rate of flow (STI hr) H = Heightof fall (ft)

$

~.."'\.

~

i \.

Where:

\ . H(FT) I I

I

+

The calculated impact force is then multiplied by an impact idler spacing factor, f(Table 2-3), to determine the impact force on one idl Unit Impact Force (lbs)

:P

{tj

= Fu = F (f)

~ --

I I

F (LBS)

Use this unit impact force, Fu' and select proper series ofimpact ¡dler from Tables 2-11 through 2-14. Fushould be equal to or less than idler rating. For material containing large lumps: Impact Force (lbs)

Where: W = H = k =

= F = W +..j

W

~

2kWH

~

Weight oflump (lbs) Height of fall (ft) Spring constant for specific idler type (lbs 1ft) (CONSULT IDLER MANUFACTURER)

+

q

Use calculated energy rating, WH, and maximum lump size to select proper series of impact idler from Table 2-4. Both WH and lump size should be equal to or less than energy rating and maximum lump size.

""'..

.

t

,, H (F1) I

*f F (LBS)

Note: Both cases (material without lumps and material containing large lumps) should always be considered and the heavier duty idler selected to insure adequate impact resistance capabilities. Table 2-3 Impact Idler Spacing Factor 1 l' l'

Factor, f

-O" -6"

2'-0" >2' - O" Table 2-4 Minimum Energy Ratings for Impact Idlers 3-RollRubber .

~

CElV1ASeries B e D E

-

32 --

-

-

-

.

-

'"

-

-

. . .

K2 = Effect oí load 00 predicted beariog L10 liíe When Calculated Idler Load (CIL) is tess than CEMA load rating of series idler selected, the bearing LIO!ife will mcrease.

Step No. 4

Figure 2.5 K2 = Effect of Load 00 Predicted Beariog L10Life

.

...

10.0

Q

8.0

...

6.0

...

4.0

..

Roller Bearing

.

2.0

I

Ball Bearing

.............

1.0

0.0 0.5

-

0.6

0.8

0.7

0.9

CIL (Calculated Idler Load) Idler Load Ratiog

I 1 I

.(

l

1.0

~

¡&

(..L-\.:-i(

/~

k-r

e

o

o

¿ tU

O)

(:>

o

¿

'"

Q) Ü

:3

o

O)

es

tU u

'"

ü

o

Ü

:3

o

::c

.eO)

"

..c '" tU U o

0::0

Figure 2.10: K4C = Effect of operating temperature on potential idler life

--

--

0.0

o

130

150 170

210

190

Temperature (degrees F) 34

-

-

-

-----

-

--

--

300

I

.

CEMA LOAD RATINGS AND CAPACITIES TABLES TABLE 2-11 LOAD RATINGS

11

35'

45"

18

410

410

410

220

24

410

410

410

190

Width (Inches)

Two Rol! Vee Retum

20"

35"

45'

Retum

18

900

900

24

900

900

900 900

325

500

30

900

900

900

250

500

36

900

837

810

200

500

42

850

791

765

150

500

475

410

410

410

165

410

410

396

155

42

390

363

351

140

48

800

744

720

125

500

48

380

353

342

130

54

750

698

675

60 66

700 650 630

. .

500 500

TABLE 2-13

Belt

Width (lnches)

FOR CEMA "D"IDLERS, (RIGID FRAME)

.

500

Trough 20"

Angle 35'

45"

Single

Rol! Retum

TABLE 2-14 LOAD RATINGS FOR CEMA "E"IDLERS, LBS (RIGID FRAME ANO CATENARY WHERE APPLlCABLE)

LBS

Two Rol! Vee Retum

Belt Wldth Trough Angle (lnches) 20" 35' 45"

Single Rol!

Two Rol! Vee

Retum

Retum

1000

1300

42

1800 1800 1800 1800 1800 1800

1000

1300

850

48

1800 1800 1800

1000

1300

500

850

54

1800 1800 1800

925

1300

425

850

60

1800 1800 1800

850

1300

54

1200 1200 1200 1200 1116 1080

375

850

66

60

1150 1070 1035

280

850

72

215

850

78

155

850

84

125

850

90

24

1200 1200 1200

600

36

30

1200 1200 1200

600

36

1200 1200 1200

600

42

1200 1200 1200

48

66 72

1050 977

78

945

96

RATINGS BASED ON MIN. L,. OF 60.000 HOURS AT 500 RPM

1800 1800 1800 1800 1674 1620 1750 1628 1575

102

775

1300

700

1300

625

1300

550

1300

475

1300

400

1300

250

1300

AATINGS BASEO ON MIN. L,. OF 60,000 HOURS AT 500 RPM

NOTES FOR TABLES2-11 THROUGH2-14 1. 2. 3.

.

TROUGHING SDLERLOAD RATINGS ARE FOR THREE EaUAL LENGTH ROLLS. LOAD RATINGS AlSO APPL y FOR IMPACT ROLlS. TROUGHING IDLER LOAD RATINGS ARE BASED ON A LOAD DISTRIBUTION OF 70% ON CENTER ROLL AND 15% ON EACH END ROLL FOR ALL TROUGH ANGLES.

11

11

Single Rol!

30

LOAD RATINGS

11

11

Angle

RATINGS BASED ON MIN. l.. OF 30,000 HOURS AT 500 RPM . USE CEMA o RETURN 10lER

11

11

Trough

36

AATINGS BASED ON MIN. L.. OF 30,000 HOURS AT 500 RPM

111

11

20"

Single Rol! Retum

Trough Angle

Width (lnches)

.

TABLE 2-12 LOAO RATINGS FOR CEMA "C"IOLERS, LBS (RIGID FRAME)

LBS

Belt

Belt

11

11

FOR CEMA "B"IDLERS, (RIGID FRAME)

LOAD CAPACITY FOR CEMA LIVE SHAFT IDLERS LOAD RATINGS FOR CEMA PICKING IDLERS, LBS Sel! Wldth

CEMAC

CEMAD

24 30 36

475 475 325 250 200 150 125

600 600 600 600 530 440 400 280

~ 48 54 60 72 84 96

BeltWidth (in) CEMAClassC CEMAClassD CEMACtassE 18 1200 24 1200 1400 2100 1200 1400 2100 30

CEMAE

1260 1200 1000 1000 1000 925 775 625

36 42

1200

-

-

1400 1400

2100 2100

1275.

48

1100 1000

54

875

1150

2100 2100

60 72

780

1000

2100

850

2100 1825

84 96

-

-

-

35

- ------------

1550

E~PLEIDLERSELECTION Customer Furnished Data Peak Load: 3,000TPH Coal at 55/60 PCF minus 8" size (Maximum lump weight = 18 lbs.) 60" BW @ 650 FPM 37,000 lbs. TI (Belt tension carrying side) 12,000 lbs. T2 (Belt tension return side) 191bs.lft. Belt weight Y4" D (Misalignment due to installation tolerances) 10 ft. H (Drop height at transfer point) Conveyor system component design life 50,000 hours Requested Information: Recommended Idler Series and Spacing: WM=

3000 x 2000 60 x 650

= 154 lbs.lft.

11

Optional verification of customer data Reference: CEMA "Belt Conveyors for Bulk Materials", Fifth Edition (or later) A. Page 53 table 4-3: 35° Troughed belt cross2 section ofload 60" BW @ 20° Surcharge = 2.876ft Full belt load: 2.876 ft2 x 55 PCF = 158Ibs/ft. Percent fullload «100)

=

154 100 x 158

= 97.47%

Since this has been identified as Peak Load the belt width, belt speed and trough angle shown, are good selections. B. Page 64 table 5-2: Suggested normal spacing ofbelt conveyor idlers (SI). 60" BW @ 50 PCF = 4.0 ft. 60" BW @ 75 PCF = 3.5 ft.

~

Factors to be considered when selecting idler spacing are belt weight, material weight, idler rating, idler life, belt

rating and belt tension. For general conveyor design and selection, limit belt sag to 2% of idler spacing at minimum tension conditions. Sag limits during conveyor starting and stopping should also be considered in overall selection. For more details on this use CEMA "Belt Conveyors for Bulk Materials". Idler selection Step No. 1: Carrying / Troughing idler series selection based on Item B above. Use preliminary selection of 4 ft. 37,000 x .25 CIL = «19+(154 x 1.0))x 4) + "A = 1077 lbs. Kl = 1.0 for 8" lump Per table 2-13: D x 35° Per table 2-14: E x 35°

= =

1070 lbs. rating 1800 lbs. rating

36

-

--.....--...-

=;==== --

- -~--

=

----

=====

. . . . . . . I

I I I I I I I I I I

Note: Although it is recornmended that CIL be equal to or less than CEMA Idler Load Rating, there is a certain amount of judgment involved in [mal selection. In this example an experienced belt designer would know that max. IML load based on belt tension occurs at head or discharge for a level or incline conveyor. Since belt tension would be decreasing from this point towards tail or loading end, the number of idlers that slightly exceeded CEMA Idler Load Rating could be determined and D series x 35° could be used and request verification from CEMA idler manufacturero Other choices are:

A. D seriesat lessthan 4 ft. spacing B. E series at greater than 4 ft. spacing C. Increase belt speed which will decrease WM. This option would also decrease TI belt tension which would decrease IML. D. Customer to maintain less than Y4"height deviation due to installation tolerances. Some of these choices would require recalculating belt tensions, etc., and then weigh the economics with expected performance of each selection. For this example we will select D series x 35° troughing idlers at 4 ft. spacing, although optional choices C & D have great merit. Rated bearing LIOlife is 60,000 hours. Step No. 2: Return Idler Series Selection Option: From "CEMA Belt Conveyor Manual" (5thedition or later) page 64 table 5-2: suggested normal spacing ofbelt conveyor idler (SI)

Returnidlers60" BW = 10ft. CIL R = (19 x 10) +

12,~00 ~.:25

= 240 lbs.

Based on above option, use preliminary selection of 10ft. spacing. Note: Quite often it is desirable to have return idler spacing at a multiple oftroughing idler spacing to simplify stringer or truss designo However, this should not be the control for selection. Per table 2-13: D series single roIl return

= 280 lbs. rating

Per table2-12:C seriestwo roll V-return

= 500 lbs. rating

If this conveyor has long centers, consideration should be given to using two roll V-returns and increasing spacing. With this choice it would not be necessary to use training idlers. For this example select D series single roll return at 12' - O". Rated bearing LIOlife is 60,000 hours. CILR

=

(19 x 12) +

12,000 x .25 6 x 12

=

270 lbs.

37

-

-

-

-

-

--

-

-

-

-

-

-

----

Step No. 3: Impact Idler Series Selection F = (0.1389)Q -/H=

Case of material without lumps:

(0.1389)(3000)~

Assuming the impact idler spacing is 1.5 ft, from Table 2-3,

1318lbs.

f= 0.7

.

Fu= F (f) = (1318) (0.7) = 922.6 lbs. Per Table 2-13: D x 35° = 1070 lbs. rating This case requires a D series impact idler. WH

Case of material with large lumps:

= (18)

(10)

1

= 180 lbs-ft

Per Table 2-4: D = 240 lbs-ft minimum energy rating Per Table 2-4: D = 8 in. maximum lump size This case requires a D series impact idler.

I

Note: The impact idler series chosen here must satisfy both the minimum energy rating and the maximum lump size criteria from Table 2-4.

11

Comparing the two cases, a D series impact idler should be selected to handle the heavier impact loado This step completes the impact idler selection process. Steps 1, 2 and 3 have selected idlers based on loado Steps 4, 5 and 6 deal with predicted bearing LIOtife and Step 7 covers conditions affecting potential idler life. Step No. 4: K2 Effect ofLoad on Predicted Bearing LIOLife Troughing Idler

=

CIL = IdlerLoad Rating

1077 1070

=

1.007

K2 (from Figure 2.3 Tapered Roller Bearing) = 1.0 Bearing LIO = (60,000x 1.0) = 60,000hours CIL Idler Load Rating

Retum Idler

=

Bearing

= (60,000 x 1.15) = 69,000 hours

LIO

.96

J

J

Step No. 5: K3A Effect ofBelt Speed on Predicted Bearing LIOLife 650 FPM Belt speed specified.

J I I

Select minimum roll dia. For:S 500 RPM at 650 FPM From chart pg. 23, 5" dia. = 654 FPM K3A (from Figure 2.6)

= 1.0

Bearing LIOlife for D5 series idlers at 650 FPM Troughing idler = (60,000 x 1.0) = 60,000 hours Retum idler = (69,000 x 1.0) = 69,000 hours

J J

38

~,,-~_..~ -~ .~=~-

-

---

---

------

J J J J

11

270

= 280 = K2 (from Figure 2.3 Tapered Roller Bearing) = 1.15

--

J I J

---

-

-

-- ~ --- --

. . . . . . . . . . . .

. . . . . . . -

Step No. 6: IGB Effect ofRoll Diameter on Predicted Bearing L¡OLife Compare bearing LIOlife increase for 6" diarneter roll.

. 2 19ure .7) -

K3B (F

. b . L l.~ 6"Dia. RoIl= 1.50 _ 120 20°/. 5" Dia. RoIl= 1.25 -. or /0 Increase In eanng 10 he.

Troughing Idler = (60,000 x 1.2) = 72,000 hours Return Idler = (69,000 x 1.2) = 82,800 hours

Note: In addition the 6" roIl would have longer wear life and roIl resistance would be less which would decrease belt tension and reduce IML. D6 idlers are recommended. Idler selection based on customer furnished data. Troughing idlers D6 x 35° at 4 ft spacing with 72,000 hours predicted bearing L10life. Return idlers D6 at 12 ft spacing with 82,800 hours predicted bearing L¡Olife. Step No. 7: K4 Effect ofEnvironmental, Maintenance and Temperature on Potential Idler Life For purpose of example we will assume the following conditions. K4A (Figure 2.8) Maintenance: K4B (Figure 2.9) Environmental: K4C (Figure 2.10) Temperature:

Good to Fair Dirty < 120 F

Hostile environmental conditions and the level of commitment to the belt conveyor instaIlation and maintenance will affect idler life. With above assumed conditions it is apparent that potential idler life will be less than predicted bearing L)Olife. These conditions should be discussed with your CEMA idler manufacturero Expected or potential idler life may also be limited by shell wear. SheIl wear can vary considerably with each instaIlation. In addition to conveyed material characteristics, environmental, and maintenance factors, idler alignment and belt cIeaning can have a significant effect on shell wear and idler life. Note: Ca1culatedidler loads should be repeated for training idlers (ifused). Height deviation oftraining idlers must be inc1udedfor IML calculation or controIled by shimming and maintaining cIoser installation tolerances at these areas of conveyof. Conclusion: There are numerous options available to the belt conveyor designer in regard to idler selection. Through involving your CEMA idler manufacturer in this selection process these options can be explored, resulting in a reliable cost effective installation.

39

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--... -

-

"'"""

APPENDIX

CONVERSION FACTORS TO SI-METRIC UNITS

This Appendix is not part of the standard, but it is included for the infonnation of those who wish to become acquainted with the international system of measurement called SI-Metric. The conversion factors shown below are only for those measured quantities appearing in this standard and are based on the American National Standard Metric Practice Guide.

To convert from:

To:

Multiply by:

inches (in) feet (ft) mass (lbs) pound-force (lbf) velocity (fpm) mass per length (lbs/ft) pounds per cubic foot (lbs/fP)

millimeters (rnm) meters (m) kilograms (kg) newton (N) meters per sec (mis) kilogram.sper meter (kglm) kilograms per cubic meter (kglm3)

25.40 .3048 .4536 4.4482 .0051 1.4882 16.0185

.

. . . . 40

= -

-

I

=

~

--