CEMA STANDARD NO

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1 CEMA STANDARD NO Revision of CEMA Standard Bulk Material Belt Conveyor Troughing and Return Idlers Selection and Dimensions CONVEYOR EQUIPMENT MANUFACTURERS ASSOCIATION ISBN

2 CEMA ORGANIZATIONAL CHART COMMITTEES BOARD OF DIRECTORS OFFICERS Conference Finance and Budget General Bulk Handling Section Meet in March and/or September Unit Handling Conveying Section Strategic Planning Bulk Handling Components and Systems Screw Conveyors Bulk Accessories Controls Conveyor Chain Palletizers Insurance Meetings Meets Each June Membership Engineering Conference Accessories Past Presidents Idlers Public Relations Committees Pulleys Statistics Safety Steering Conveyor Chain Performance Terminology Unit Handling Standards Unit Handling Section Bulk Handling Section Screw Conveyors Belt Systems Safety Controls Terms and Definitions International Standards Belt Manual For Information on Company Membership visit the CEMA Web Site at SAFETY NOTICE The Conveyor Equipment Manufacturers Association has developed Industry Standard Safety Labels for use on the conveying equipment of its member companies. The purpose of the labels is to identify common and uncommon hazards, conditions, and unsafe practices which can injure, or cause the death of, the unwary or inattentive person who is working at or around conveying equipment. The labels are available for sale to member companies and non-member companies. A full description of the labels, their purpose, and guidelines on where to place the labels on typical equipment, has been published in CEMA s Safety Label Brochure No The Brochure is available for purchase by members and non-members of the Association. Safety Labels and Safety Label Placement Guidelines, originally published in the Brochure, are also available free on the CEMA Web Site at PLEASE NOTE: Should any of the safety labels supplied by the equipment manufacturer become unreadable for any reason, the equipment USER is then responsible for replacement and location of these safety labels. Replacement labels and placement guidelines can be obtained by contacting your equipment supplier or CEMA.

3 DISCLAIMER The information provided in this document is advisory only. These recommendations are provided by CEMA in the interest of promoting safety in the work place. These recommendations are general in nature and are not intended as a substitute for a thorough safety program. Users should seek the advise, supervision or consultation of qualified engineers or other safety professionals. Any use of this document, the information contained herein, or any other CEMA publication may only be made with the agreement and understanding that the user and the user s company assume full responsibility for the design, safety, specifications, suitability and adequacy of the system component, or mechanical or electrical device designed or manufactured using this information. The user and the user s company understand and agree that CEMA, its member companies, its officers, agents and employees shall not be liable in any manner under any theory of liability for the user or user s reliance on these recommendations. The users and the user s company agree to release, hold harmless and indemnify CEMA, its member companies, successors, assigns, officers, agents and employees from any and all claims of liability, costs, fees (including attorney s fees), or damages arising in any way out of the use of this information. CEMA and its member companies, successors, assigns, officers, agents and employees make no representations or warranties whatsoever, either express or implied, about the information contained in this document, including, but not limited to, representations or warranties that the information and recommendations contained herein conform to any federal, state or local laws, regulations, guidelines or ordinances.

4 Bulk Material Belt Conveyor Troughing and Return Idlers Selection and Dimensions FOREWORD This standard has been established to provide uniformity of clearance and mounting dimensions among the various manufacturers of conveyor belt troughing idler and return rolls. This standard assures the users of conveyor idlers interchangeability of complete idler assemblies but does not restrict the manufacturer, who has complete freedom to design all parts of the idler according to its best engineering judgment. The various idlers are separated into nine different classes according to load ratings and roll diameters. There are some overlaps because of wide variation in idler construction. All manufacturers must specify into which class their particular designs fall. It is hoped this standardization will eliminate requests for special idler designs. Conformance with this standard will provide better designs at lower cost. The 18 edition added technical data for expanded belt widths on CEMA C, D, and E Rollers and Returns and the tables have all been reformatted to make the material easier to access. This 2001 edition has added technical data for CEMA C, D, and E Picking Idlers, Live Shaft Idler Dimensions and Load Capacities for Rubber Disc and Steel Tube Designs, and has modified the Idler Selection Procedures to include Impact Idler Selection. This 2004 edition has: 1. Reformatted the tables for CEMA Class B,C,D, and E Troughing Idlers, Picking Idlers, and Return Idlers for easier reference. 2. Redrawn the Idler Diagrams to conform with the revised tables. 3. Added CEMA Class F Idlers 4. Reformatted and Consolidated CEMA Load Ratings and Capacities Tables Prepared by The Idler Committee of the CEMA Engineering Conference CONVEYOR EQUIPMENT MANUFACTURERS ASSOCIATION 4 Lone Oak Blvd. Naples, Florida 34 (23) Fax: (23) cema@cemanet.org Web Site: Standard No Copyright 2004 Conveyor Equipment Manufacturers Association ISBN Publication Date: June, 2004

5 IDLER NOMENCLATURE CEMA STANDARD This standard provides uniform dimensional and load capacity information for several idler types, as follows. -Troughing Idlers, with equal length rolls. -Picking Idlers, with unequal length rolls. -Return Idlers, with a single steel roll but typically available with rubber discs. -V Return Idlers, with a pair of steel rolls but typically available with rubber discs. -Live Shaft Idlers with steel or rubber surfaces. Nomenclature and selection methods have been developed to provide a realistic and versatile means of classifying idlers. The idler classifications and historic series are tabulated below. CEMA Class Former Series Roll Diameter Belt Width Description A4 A5 STANDARD WITHDRAWN - October 1, 1 STANDARD WITHDRAWN - October 1, 1 Light Duty B4 B5 II II 4" 5" 18" through " 18" through " Light Duty C4 C5 C III III IV 4" 5" " 18" through " 18" through " " through " D5 D None None 5" " " through " " through " Medium Duty E E7 V VI " 7" " through " " through " Heavy Duty F F7 F8 New New New " 7" 8" " through " " through " " through " Heavy Duty Idler Designation TABLE OF CONTENTS Type and Angle Page CEMA CEMA CEMA CEMA CEMA B4, B5 C4, C5, C D5, D E, E7 F F7 F8 Troughing Troughing Troughing Troughing Troughing 20º 35º 45º 20º 35º 45º 20º 35º 45º 20º 35º 45º 20º 35º 45º CEMA CEMA CEMA CEMA CEMA B4 and B5 C4, C5, C D5,D E, E7 F and F7 Flat Return Flat and V Returns º & 15º Flat and V Returns º & 15º Flat and V Returns º & 15º Flat Return CEMA CEMA CEMA C4, C5, C D5 and D E and E7 Picking 20º Picking 20º Picking 20º CEMA Live Shaft Idler Dimensions and Load Capacities Rubber Disc and Steel Tube Designs CEMA Belt Scale Idler Standard Selection of Idlers Idler Selection Procedure Load Ratings and Capacities Tables Example: Idler Selection Conversion Factors to SI-Metric Units For final design, request certified prints

6 CEMA CLASS B TROUGHING IDLERS CEMA CLASS B TROUGHING IDLERS BELT WIDTH Trough Angle 4 E Max 5 4 H Max 5 4 K ± 1/ /2 1/2 1/4 3/ / /4 1 3/ /2 3/4 3/4 11 1/2 13 3/4 15 3/4 11 1/4 13 1/4 1/4 1/4 15 3/ /4 23 3/ /4 28 3/4 27 3/4 25 1/ /4 3/ /2 7 1/2 1/ /4 15 1/2 17 1/ /4 1/2 33 1/ /2 13 1/2 1 3/4 1 3/4 17 1/4 1 1/4 4 1/2 3 1/4 45 3/4 38 1/4 7 1/ / / / /2 51 3/4 47 1/2 43 1/4 7 1/2 8 A C MAX BELT WIDTH STD. BASE WIDE BASE STD. BASE WIDE BASE B D MAX /2 35 1/2 41 1/2 47 1/2 53 1/2 5 1/2 7 1/2 7 1/2 For final design, request certified prints 2.

7 CEMA CLASS C TROUGHING IDLERS CEMA CLASS C TROUGHING IDLERS BELT WIDTH Trough Angle 4 E Max 5 4 H Max 5 4 K ± 1/ /4 1/2 11 1/2 13 3/4 15 1/2 11 1/4 13 1/4 15 1/2 3/4 3/4 15 3/4 22 1/ /2 22 1/ /2 27 1/ / / /4 15 1/2 17 1/4 13 1/ /2 34 1/ / /2 1/2 27 1/ /4 1 1/4 18 3/4 13 1/2 1 3/4 1 1/4 17 1/4 1 1/4 40 1/2 37 1/ /2 37 1/ /2 32 1/ /4 20 1/4 1/2 18 1/4 20 1/2 15 1/4 18 3/4 20 3/4 4 1/ / /2 41 1/2 37 1/2 1/ /4 15 1/2 1 3/ / /4 52 1/2 1/ /2 1/ /2 47 1/2 1/2 1 3/4 20 1/4 23 1/4 1 1/ /2 17 1/4 21 1/4 23 3/ /2 52 1/2 47 1/2 8 3/4 1/4 3/4 17 3/4 21 1/ / /4 22 1/2 25 1/4 4 1/2 5 1/2 4 1/2 5 1/2 3 1/ /2 8 3/4 1/4 3/4 BELT WIDTH 18 STD. BASE A WIDE BASE STD. BASE 2 1/2 35 1/2 41 1/2 47 1/2 53 1/2 5 1/2 C MAX WIDE BASE 35 1/2 41 1/2 47 1/2 53 1/2 5 1/2 5 1/2 78 B 7 1/2 7 1/2 D MAX 11 1/2 11 1/2 For final design, request certified prints 3.

8 CEMA CLASS D TROUGHING IDLERS CEMA STANDARD CEMA CLASS D TROUGHING IDLERS BELT WIDTH Trough Angle 5 1/4 15 1/2 3/4 15 1/2 17 1/4 13 1/2 1 3/4 1 1/2 18 1/4 20 1/2 15 1/2 1 3/ / / / E Max 3/4 3/4 15 3/4 13 1/ /2 1/4 17 1/4 1 1/4 15 1/4 18 3/4 20 3/4 1 1/ /2 17 1/4 21 1/4 23 3/4 1 1/4 22 1/2 25 1/4 20 1/ / /2 34 1/ /2 37 1/ / /2 1/ /2 5 1/2 7 1/2 4 H Max 27 1/ /2 33 1/2 1/2 27 1/2 3 1/2 32 1/2 45 1/2 41 1/2 37 1/2 51 1/2 47 1/2 57 1/2 52 1/2 47 1/2 3 1/ /2 75 1/2 2 1/2 K ± 1/4 5 1/4 1/4 1/2 1/2 1/2 3/4 3/4 BELT WIDTH A C MAX B D MAX STD. BASE WIDE BASE STD. BASE WIDE BASE /2 41 1/ /2 47 1/ /2 53 1/ /2 5 1/2 7 1/ /2 5 1/2 7 1/ / / For final design, request certified prints

9 CEMA CLASS E TROUGHING IDLERS CEMA STANDARD CEMA CLASS E TROUGHING IDLERS BELT WIDTH 84 Dimension K for 84" and " belt w idths may differ w ith some manufacturers. E Max H Max K ± 1/4 Trough Angle / / /4 11 1/4 21 1/ /2 22 1/ /2 1 1/2 25 1/ / / /2 1 1/ / / /2 2 1/2 31 1/2 1/2 31 1/2 34 1/2 2 1/2 33 1/2 37 1/2 43 1/ / / / /4 3/4 3/4 3/4 11 1/2 11 3/4 11 3/4 11 1/4 11 1/4 11 1/4 11 1/4 1/4 1/4 BELT WIDTH 84 A C MAX B D MAX STD. BASE WIDE BASE STD. BASE WIDE BASE / / / / / / / /2 For final design, request certified prints 5.

10 CEMA CLASS F TROUGHING IDLERS CEMA STANDARD CEMA CLASS F TROUGHING IDLERS BELT WIDTH Trough Angle 84 Dimension K for 84" and " belt w idths may differ w ith some manufacturers. 21 1/ /2 2 1/2 31 1/2 1/2 31 1/2 34 1/2 2 1/2 33 1/2 37 1/2 E Max / /2 23 1/2 1/2 32 1/2 25 1/2 32 1/2 35 1/2 27 1/2 34 1/2 3 H Max /4 1/4 1/4 K ± 1/ /4 3/4 1/2 13 3/4 13 1/4 3/4 13 1/4 BELT WIDTH 84 A C MAX B D MAX STD. BASE WIDE BASE STD. BASE WIDE BASE For final design, request certified prints.

11 CEMA CLASS B RETURN IDLERS CEMA STANDARD FLAT RETURNS ( 4" AND 5" DIAMETERS ) For wide base returns, use next higher belt width. *Some differences may exist in dimensions with some manufacturers. **Also available with 1 1/2" drop. BELT WIDTH 18 A STD BASE C MAX 2 1/2 35 1/2 41 1/2 47 1/2 53 1/2 5 1/8 F MIN For final design, request certified prints

12 CEMA CLASS C RETURN IDLERS FLAT RETURNS ( 4", 5", AND " DIAMETERS ) For wide base returns, use next higher belt width. *Some differences may exist in dimensions with some manufacturers. **Also available with 1 1/2" drop. BELT WIDTH 18 A STD BASE C MAX 2 1/2 35 1/2 41 1/2 47 1/2 53 1/2 5 1/8 USE CEMA "D" RETURN ROLLER F MIN V-RETURNS **Also available with 4 1/2" drop which decreases all vertical dimensions by 2 1/2". For wide base returns use next larger belt width. BELT WIDTH A /2 43 1/2 4 1/2 55 1/2 1 1/2 7 1/2 73 1/2 7 1/2 C Max /4 44 1/4 50 1/4 5 1/4 2 1/4 8 1/4 74 1/4 80 1/4 5 3/4 7 1/2 7 7/8 5/8 1/8 3/4 1/ /8 8 1/8 5/8 1/4 E ± 1/ /8 1/2 11 1/4 1/8 7/8 13 5/ /2 1/8 3/4 11 5/8 3/8 13 1/8 15 7/8 1 3/8 1 3/4 17 3/8 17 7/8 18 7/8 1 1/2 20 3/8 G Max /4 17 3/ / /8 22 3/8 23 5/8 8 For final design, request certified prints

13 CEMA D RETURN IDLERS FLAT RETURNS ( 5" AND " DIAMETERS ) For wide base returns, use next higher belt width. *Some differences may exist in dimensions with some manufacturers. **Also available with 1 1/2" drop. BELT WIDTH A STD BASE 33 3 C MAX 35 1/2 41 1/2 F MIN /2 53 1/2 5 1/8 5 1/2 71 1/2 77 1/2 83 1/ V-RETURNS **Also available with 4 1/2" drop which decreases all vertical dimensions by 2 1/2". For wide base returns use next larger belt width. E ± 1/4 BELT WIDTH 78 A /2 55 1/2 1 1/2 7 1/2 73 1/2 7 1/2 85 1/2 1 1/2 C Max /4 5 1/4 2 1/4 8 1/4 74 1/4 80 1/4 8 1/4 2 1/ /8 5/8 1/8 3/4 11 1/4 11 3/4 7 3/8 8 1/8 5/8 1/4 3/4 11 1/4 5 5/8 1/2 11 1/4 1/8 7/8 13 5/8 5/8 15 1/2 15 1/8 3/4 11 5/8 3/8 13 1/8 1/ /8 17 1/ /8 1 1/ /2 21 G Max / /8 22 3/8 23 5/8 1/4 25 1/8 For final design, request certified prints

14 CEMA E RETURN IDLERS CEMA STANDARD FLAT RETURNS ( " AND 7" DIAMETERS ) For wide base returns, use next higher belt width. *Some differences may exist in dimensions with some manufacturers. **Also available with 1 1/2" drop. BELT WIDTH A STD BASE C MAX 1/2 1/2 1/2 1/2 1/ /2 0 1/2 1/2 2 1/2 1 1/2 V-RETURNS D MAX 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 F MIN **Also available with 4 1/2" drop which decreases all vertical dimensions by 2 1/2". For wide base returns use next larger belt width. BELT WIDTH A C ± 1/ E ± 1/ /8 7 5/8 8 1/8 8 5/8 1/8 1/2 7 5/8 8 1/8 8 5/8 1/8 5/8 5/8 11 1/8 11 5/8 1/8 5/8 13 1/8 1/8 5/8 11 1/8 11 5/8 1/8 5/8 1/8 7/8 5/8 11 3/8 1/ /8 1/2 15 1/4 1 1/8 1 7/8 17 3/ /8 3/8 1/8 7/8 11 5/8 1/2 13 1/8 3/4 15 5/8 1 3/8 17 1/4 18 1/4 18 3/4 1 1/4 1 3/4 20 1/4 21 1/ /2 23 1/8 23 5/8 1/4 3/4 G Max / /8 22 3/4 23 1/ /4 2 1/2 27 1/4 28 1/8 28 7/8 2 3/4 For final design, request certified prints

15 CEMA F RETURN IDLERS FLAT RETURNS ( ", 7" and 8" DIAMETERS ) For wide base returns, use next higher belt width. *Some differences may exist in dimensions with some manufacturers. BELT WIDTH A STD BASE C MAX F MIN /2 85 1/2 7 1/ /2 1 V-RETURNS For Vee Returns consider using CEMA E. 11 For final design, request certified prints

16 CEMA PICKING IDLERS CEMA STANDARD CEMA CLASS C PICKING IDLERS BELT E Max 4 7/8 7/8 7/ /4 11 1/ /8 11 3/8 11 3/8 11 1/2 11 1/2 11 3/4 11 3/4 11 7/8 11 7/8 11 7/8 1/4 1/4 H Max K ± 1/ /4 34 3/4 40 3/4 4 3/4 52 3/4 58 3/4 4 3/4 32 3/8 34 3/8 40 3/8 4 3/8 52 3/8 58 3/8 4 3/ /4 8 3/4 5 1/4 1/4 1/2 1/2 3/4 3/4 L Bolt Dia. 1/2 1/2 1/2 5/8 5/8 5/8 5/8 CEMA CLASS D PICKING IDLERS CEMA CLASS E PICKING IDLERS BELT WIDTH 84 BELT E Max H Max K ± 1/4 L WIDTH /8 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/8 3/4 3/4 3/4 3/4 3/4 3/4 3/ /4 34 3/4 40 3/4 4 3/4 52 3/4 58 3/4 4 3/4 7 3/4 32 3/8 34 3/8 40 3/8 4 3/8 52 3/8 58 3/8 4 3/8 7 3/8 5 1/4 1/4 1/2 1/2 1/2 3/4 3/4 BELT WIDTH E Max 7 H Max 7 K ± 1/ STD. A 3/8 5/8 BASE WIDE BASE /2 1/2 1/2 1/2 1/2 7/8 15 1/8 43 1/8 4 1/8 55 1/8 1 1/8 7 1/8 7 1/8 1 1/8 7/8 7/8 7/8 7/8 7/8 78 7/8 0 7/8 3/4 3/4 3/4 3/4 3/4 11 1/2 11 3/4 5/8 15 1/8 3 1/8 2 7/8 11 3/4 STD. BASE C/D E 35 1/2 41 1/2 47 1/2 53 1/2 5 1/ C MAX WIDE BASE C/D E 41 1/2 47 1/2 53 1/2 5 1/2 5 1/ /4 11 1/4 11 1/4 11 1/4 11 1/4 1/4 1/4 C/D 7 1/2 7 1/2 B Bolt Dia. 1/2 1/2 1/2 5/8 5/8 5/8 5/8 5/8 L Bolt Dia. 3/4 3/4 3/4 3/4 3/4 3/4 3/4 NOTE: ROLL LENGTHS VARY WIDELY BETWEEN MANUFACTURERS. CONSULT SPECIFIC MANUFACTURERS FOR ACTUAL DIMENSIONS. 3/4 CEMA CLASS E 1/2 1/2 1/2 1/2 1/2 1/2 C/D 11 1/2 11 1/2 D MAX E 1 1/2 1 1/2 For final design, request certified prints.

17 CEMA LIVE SHAFT IDLER DIMENSIONS (Inches) CEMA STANDARD CEMA Live Shaft Load Capacity (lbs) Live Shaft Idlers are developed to be compatible with commonly available bearing assemblies which may not be part of the idler assembly. Load ratings are developed for uniformly distributed steady running loads. Consult the manufacturer for non uniform loading and for application information important for long bearing life. For Live Shaft Load Capacities, Refer to Chart on Page 35 Rubber Disc and Steel Tube Designs Dim A Dim B Dim C Dim D Dim E BW+ CEMA Class C: J = " Live Shafts; O.D. = 5" & " BW to 3.75 BW+ to m inim um 1.50 m inim um CEMA Class D: J = 1.375" Live Shafts; O.D. = 5" & " BW+ BW =2.875 to BW+.35 to 3.88 m inim um 1.75 m inim um BW+ BW = Belt Width (in) CEMA Class E: J = " Live Shafts; O.D. = " & 7" BW+1.75 to 4.25 BW to 4.50 m inim um 2.25 m inim um 13. For final design, request certified prints

18 CEMA BELT SCALE IDLER STANDARD CEMA STANDARD Idlers and rolls produced to the basic CEMA Standard No. 502 have dimensional tolerances which, under certain conditions, may be insufficient to meet the requirement of a specific accuracy of an in-motion weighing system. The table below specifies dimensional tolerances for idlers and rolls to be classified for use with non-certified scales for belt conveyor systems. These will be referred to as Scale Quality idlers. (1) (2) (3) (4) (5) () (7) Roll run-out, mounted.015 T.I.R. max. (all rolls) Axis of roll ± 0.031" from perpendicular through center of base End brackets perpendicular to base angle 0O ± 1O Bottom of base to top of center roll + 0", - 1/8" Troughing angle by template ± 1O Foot plates to be flat within 0.0" Idler base deflection not to exceed 1/00 of the span at published CEMA idler load rating. Deflection measured at support for center roll. "Scale Quality" Idlers When considering the installation and or maintenance of a belt scale system, the use of like idlers and rolls within the scale area is important. Proper alignment of all components and the control of contaminants are essential. Belt conveyor scales from different manufacturers vary in characteristics, accuracy, and dimensions. Therefore, the basic installation requirements relative to idler spacing and position must be obtained from the respective scale manufacturer..

19 THE SELECTION OF IDLERS Foreword Previous to /1/ CEMA ratings were based on 0,000 hours Bu (useful bearing life) at 500 RPM. Bu values were approximately 3 times L. The Bu (useful bearing life) theory was technically correct. However, L bearing life is more commonly used and accepted for bearing life calculations and rating. Previous CEMA idler selection procedure used idler life (K) factors to calculate an adjusted idler load. Some of these (K) factors were entirely independent of idler load and bearing L life. This procedure provided a conservative selection based on load but did not necessarily provide clear data relative to expected idler life. Rating and Idler Life Idler life is determined by a combination of many factors, such as seals, bearings, shell thickness, belt speed, lump size / material density, maintenance, environment, temperature and the proper CEMA series of idler to handle the maximum calculated idler load. While bearing life is often used as an indicator of idler life it must be recognized that the effect of other variables (e.g., seal effectiveness) may be more important in determining idler life than the bearings. Nevertheless, since bearing rating is the only variable for which laboratory tests have provided standard values, CEMA uses bearing L life as a guide for establishing idler ratings. The definition of L for belt conveyor idlers: The basic rated life (number of operating hours at 500 RPM) based on a 0 percent statistical model which is expressed as the total number of revolutions 0 percent of the bearings in an apparently identical group of bearings subjected to identical operating conditions will attain or exceed before a defined area of material fatigue (flaking, spalling) occurs on one of its rings or rolling elements. The L life is also associated with 0 percent reliability for a single bearing under a certain load. Tables 2-11 through 2- show load ratings for CEMA B, C, D, and E idlers. These load ratings are based on the following: CEMA B load rating based on minimum L of,000 hours at 500 RPM CEMA C load rating based on minimum L of,000 hours at 500 RPM CEMA D load rating based on minimum L of,000 hours at 500 RPM CEMA E load rating based on minimum L of,000 hours at 500 RPM CEMA F load rating based on minimum L of,000 hours at 500 RPM These loads and L life ratings are minimum ratings for CEMA rated idlers. Actual values for load ratings and L life for specific series and belt sizes supplied by CEMA manufacturers may be higher. In some cases the idler frame design could be the limiting factor for load with L life being a higher value. Idler Selection There are many conditions that affect idler life. Those considered in this selection procedure are: 1. Type of material handled 2. Idler load 3. Impact forces 4. Effect of load on predicted bearing L life 5. Belt speed. Roll diameter 7. Environmental, maintenance and other special conditions In addition to information provided in the Idler Selection Procedure the above items are summarized as follows: 15.

20 Type of Material Handled The characteristics of the material handled have a direct bearing on the idler selection. The weight of the material governs the idler load and spacing, and lump size modifies the effect of weight by introducing an impact factor. Table 2-2 combines the unit weight and the lump size into a group of empirical factors referred to as K1. Note that in the table lump size means the largest lump which may occasionally be carried rather than the average lump. Lump Size Considerations The lump size influences the belt specifications and the choice of carrying idlers. There is also an empirical relationship between lump size and belt width. The recommended maximum lump size for various belt widths is as follows: Idler Load For a 20º surcharge, with % lumps and 0% fines, the recommended maximum lump is 1/3 the belt width (bw/3). With all lumps the recommended maximum lump is 1/5 belt width (bw/5). For a º surcharge, with % lumps and 0% fines, the recommended maximum lump is 1/ the belt width (bw/). With all lumps maximum lump is 1/ the belt width (bw/). To select the proper CEMA class (series) of idler, it is necessary to calculate the idler load. This procedure is shown in IDLER SELECTION PROCEDURE (Step No. 1) for troughing idlers and (Step No. 2) for return idlers. The idler load should be calculated for peak or maximum conditions. The belt conveyor designer should thoroughly investigate all conditions relative to calculating idler misalignment load (IML), in addition to structure misalignment. The idler height deviation between standard fixed idlers and training idlers (or other special types of idlers) must be accounted for either by idler series selection or by conveyor design and installation control. Impact Forces Impact forces at conveyor loading points are yet another consideration for idler selection. Whether the conveyed material contains large lumps or is a continuous flow of homogeneous material with no lumps, the impact force should be studied. This process is demonstrated in Step No. 3. When large lumps (greater than 2 inches) are present, the impact idler energy rating, WH, may become a factor. Table 2-4 shows the minimum energy rating and the maximum lump size for each CEMA series impact idler. The impact force, F, is then given by the following equation: F = W + 2kWH If the conveyed material does not contain lumps, but instead is a homogeneous stream of material, the impact force is simply a function of the rate of flow and the height of fall. This impact force is given by the following equation: F = (0.138) Q H Effect of Load on Predicted Bearing L Life When calculated idler load (CIL) is less than CEMA load rating of series idler selected, the bearing L life will increase. Figure 2.5 (Step No. 4) shows this relationship for either a tapered roller bearing or a ball bearing idler design. This chart can be used in conjunction with the type of service or life expectancy of the conveyor system. If the specified design life of the conveyor system exceeds the CEMA L life rating at rated load it may still meet specification based on percent of rated idler load vs calculated idler load (CIL). 1.

21 Belt Speed Bearing life (L ) is based on the number of revolutions of the bearing race. The faster the belt speed, the more revolutions per minute and consequently, a shorter life for a given number of revolutions. All CEMA L life ratings are based on 500 RPM. The following table lists belt speed at 500 RPM for standard roll diameters. Roll Diameter (in.) 4" 5" " 7" 8" Belt Speed (FPM) Figure 2. (Step No. 5) shows the effect of belt speed on predicted bearing L life. However, suitable belt conveyor speeds also depend upon the characteristics of the material to be conveyed, the capacity desired and the belt tensions employed. This subject is covered in more detail in CEMA "Belt Conveyors for Bulk Material," Fifth Edition (or later), Chapter 4. Roll Diameter For a given belt speed, using larger diameter rolls will increase idler bearing L life. Figure 2.7 (Step No. ) shows this relationship. In addition, since larger diameter rolls will be contacting the belt less due to a slower RPM the wear life of the shell will be increased. Environmental, Maintenance and Other Special Conditions Step No. 7 in the idler selection procedure identifies conditions that will affect potential idler life. All of these conditions do not have an exact mathematical basis and therefore can be very subjective. The most important phase of this step is in identifying the idler life condition for the application and then arrive at solutions to obtain maximum idler life for that application. Since idler roll configuration, type of bearing and seal design can vary with each idler manufacturer it is logical to state that idler life can also vary for a given environmental and maintenance condition. Figures 2.8, 2. and 2. show general conditions which will affect idler life. Those conditions are independent of idler load but can cause idler failure before obtaining predicted L life rating. CEMA recommends contacting your CEMA idler manufacturer for assistance in establishing guidelines for "POTENTIAL IDLER LIFE" for the various conditions shown or any unusual conditions not listed. Special Conditions Idler roll shell material usually used throughout the industry is electric resistance welded steel mechanical tubing. For most belt conveyor applications this material provides sufficient idler life, most economically. For severe abrasive or corrosive conditions, covered idler rolls are available in a variety of materials. CEMA has not compiled a relative wear index or corrosion compatibility index for these various materials. This information can be supplied by your CEMA idler manufacturer. However the economic issue vs increased life should be investigated thoroughly. Some of the generic available materials are listed below. There are numerous grades available in each of these materials which will affect performance. 1. Steel sleeves 2. Rubber lagging 3. Neoprene lagging 4. Polyethylene sleeves / rolls 5. Carboxylated nitrile. Urethane 7. Ceramic 17.

22 Another consideration for increasing shell wear life is to use thicker metal shells. Some idler manufacturers customarily supply larger diameter rolls with thicker metal shells and usually offer optional shell thickness for all roll diameters. Idler shell wear life is more of a factor for the return idlers since it normally contacts the "dirty" side of the belt resulting in abrasive wear of the shell. The exception to this would be a conveyor system with a belt turnover system. With normal conveyor systems, materials build up on the roll and increase its effective diameter. Because the buildup is never uniform and usually is less at the belt edges, the clean sections of the return roll travel at a slower surface speed than that of the belt. This results in relative slippage, thereby accelerating wear of both the belt cover and the surface of the roll. Thus the life of the roll shell is usually shorter on return belt idlers than on carrying idlers. The material buildup can also aggravate belt training. 18.

23 IDLER SELECTION PROCEDURE Initial Selection; Steps 1, 2 and 3: Preface to Selection Procedure Figures and Tables. Select idler class by comparing calculated idler load with idler load ratings (CIL and CILR) from Tables 2-11 through 2-. Select impact idler class, if necessary, as shown in Step 3. CEMA idler manufacturers have standard designs meeting these load ratings and dimensional standards shown in tables listed in this publication. Bearing L Life Correction; Steps 4, 5, and : Factors K2 (Fig. 2.5) and K3A (Fig. 2.) are multiplying factors used to adjust basic L life rating of idler class selected. Factor K2 is based on percent of idler load and K3A is factor for actual roll speed (RPM). Factor K3B (Fig. 2.7), step is an optional step showing advantage of using larger diameter rolls. It can be used as a multiplier to save repeating step 5 if a larger diameter roll is used. Determine Potential Idler Life; Step 7: Factors K4A (Fig. 2.8), K4B (Fig. 2.) and K4C (Fig. 2.) show conditions which will affect idler life and are independent of bearing L life, idler load and idler class. Use these figures to evaluate the potential expected idler life. Contact your CEMA idler manufacturer for recommendations. Step No. 1 - Troughing Idler Series Selection Calculated Idler Load (lbs.) = CIL = ((WB + (WM x K1)) x SI) + IML Where: WB = Belt weight (lbs./ft.) use actual or estimate from Table 2-1 WM = Material weight (lbs./ft.) = (Q x 2000) / ( x V) Q = Quantity of material conveyed (Tons per hour) V = Design belt speed (FPM) SI = Spacing of idlers (ft.) K1 = Lump adjustment factor (see Table 2-2) Note: Actual weight of lump should be compared with WM value. In situations it may be necessary to use actual lump weight as WM. Contact your CEMA idler manufacturer if you have doubts as to which value to use. IML = Idler misalignment load (lbs.) due to idler height deviation and belt tension = (D x T) / ( x SI) where: D = Misalignment (inches) T = Belt tension (lbs.) SI = Idler spacing (feet) When an idler is higher than adjacent idler, a component of belt tension will add load to that idler. The amount of height deviation can vary with the installation and type of idler. CEMA publication on "Conveyor Installation Standards" ( also found in Appendix D, "Belt Conveyors for Bulk Material," Fifth Edition or later) lists recommendations on structure misalignment). Use CIL and select proper series of idler from Tables 2-11 through CIL value should be equal to or less than idler rating. 1.

24 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 load. See Step No. 3 for impact idler series selection. Contact your CEMA idler manufacturer for idler series selection for other loading conditions. Belt Width (inches (b)) Table 2-1 WB-Estimated average belt weight multiple and reduced ply belts. lbs./ft. 1. Steel cable belts - increase above value by 50%. Material Carried, lbs./cu. ft 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 Maximum Lump Size (inches) Material Weight, lbs./cu. ft Step No. 2 - Return idler series selection Calculated Idler Load (lbs.) = CIL R = (WB x SI) + IML Use CIL R and select proper series of idler from Tables 2-11 through 2-. CIL R should be equal to or less than return idler rating. 20.

25 Step No. 3 - Impact Idler Series Selection For homogeneous material without lumps: Impact Force (lbs) = F = (0.138) Q Where: Q = Rate of flow (ST / hr) H = Height of fall (ft) H The calculated impact force is then multiplied by an impact idler spacing factor, f (Table 2-3), to determine the impact force on one idler. Unit Impact Force (lbs) = Fu = F (f) Use this unit impact force, Fu, and select proper series of impact idler from Tables 2-11 through 2-. Fu should be equal to or less than idler rating. For material containing large lumps: Impact Force (lbs) = F = W + 2kWH Where: W = Weight of lump (lbs) H = Height of fall (ft) k = Spring constant for specific idler type (lbs / ft) (CONSULT IDLER MANUFACTURER) 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. 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, SI 1' - 0" 1' - " 2' - 0" > 2' - 0" Impact Idler Spacing Factor Impact Idler Spacing Factor, f Table 2-4 Minimum Energy Ratings for Impact Idlers CEMA Series B C D E F 3-Roll Rubber Impact Idlers (Equal Length Rolls) WH (lbs-ft) Maximum Lump Size (in.)

26 Step No. 4 - K2 = Effect of load on predicted bearing L life When Calculated Idler Load (CIL) is less than CEMA load rating of series idler selected, the bearing L life will increase. Figure 2.5 K2 = Effect of Load on Predicted Bearing L Life.0 K2Factor Ball Bearing Roller Bearing CIL (Calculated Idler Load) Idler Load Rating Step No. 5 - K3A = Effect of belt speed on predicted bearing L life CEMA L life ratings are based on 500 rpm. Slower speeds increase life and faster speeds decrease life. Figure 2.4 shows this relationship. K3A Factor Figure K3A = Effect of Belt Speed on Predicted Bearing L Life Roll Speed (rpm) RPM = Belt Speed (fpm) x Roll Dia. (in.) x p Step No. - K3B = Effect of roll diameter on predicted bearing L life. For a given belt speed, using larger diameter rolls will increase idler L life. Figure 2.5 depicts L life adjustments for various roll diameters using 4 diameter as a value of 1.0. Percent life increase can be calculated for each roll diameter increase. 1.5 for " dia Example: = 1.20 or 20% increase in L life for 5" dia Figure 2.7 K3B = Effect of Roll Diameter on Predicted Bearing L Life (Based on same belt speed) 1.75 K3B Factor Note: In addition to increased predicted bearing L life, larger diameter rolls can increase idler wear life. 22.

27 Step No. 7 - K4 = Environmental, maintenance and other special conditions Figure 2.8: Figure 2.: K4A = Effect of maintenance on potential idler life K4B = Effect of environment on potential idler life Figure 2.: K4C = Effect of operating temperature on potential idler life Based on collective application experience by CEMA idler manufacturers these conditions are very important in determining potential idler life. However, exact mathematical basis is very subjective so contact your CEMA idler manufacturer for assistance or for any unusual conditions not listed. Figure 2.8: K4A = Effect of maintenance on potential idler life K4C Factor K4B Factor K4A Factor Clean, Dry GOOD FAIR POOR Figure 2.: K4B = Effect of environment on potential idler life Figure 2.: K4C = Effect of operating temperature on potential idler life 1.0 Dusty, Dry Dirty, Dry Clean, We t Dusty, W et Dirty, We t W et w/ph Press W ash Down Temperature (degrees F) 23.

28 CEMA LOAD RATINGS AND CAPACITIES TABLES CEMA STANDARD Load Ratings for CEMA Idlers - Rigid Frame (Lbs) Idler Class CEMA B Idlers CEMA C Idlers CEMA D Idlers CEMA E Idlers CEMA F Idlers Belt Width (Inches) Trough Angle Ratings Based on Min L of,000 Hours at 500 RPM Ratings Based on Min L of,000 Hours at 500 RPM * Use CEMA "D" Return Idler Single Roll Return * * * 1,200 1,200 1, ,200 1,200 1,200 1,200 1,200 1,200 1,200 1,200 1,200 1,200 1,200 1,200 1,200 1,11 1,080 1,150 1,070 1,035 1, Ratings Based on Min L of,000 Hours at 500 RPM ,800 1,74 1,750 1,800 1,74 1,28 Ratings Based on Min L of,000 Hours at 500 RPM Two Roll Vee ,800 1,800 1,800 1,000 1,0 1,800 1,800 1,800 1,800 1,800 1,800 1,800 1,800 1,800 1,800 1,800 1,800 Rigid Frame and Catenary Where Applicable 1,800 1,20 1,575 1,000 1, ,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 3,000 3,000 3,000 1,500 ** 3,000 3,000 3,000 1,200 ** 84 3,000 3,000 3, ** 2,800 2,800 2,800 0 ** Ratings Based on Min L of,000 Hours at 500 RPM Rigid Frame and Catenary Where Applicable ** For Vee Returns Consider Using CEMA "E" Series TABLE 2-15 TABLE 2- TABLE 2-13 TABLE 2- TABLE 2-11 NOTES FOR TABLES 1. TROUGHING IDLER LOAD RATINGS ARE FOR THREE EQUAL LENGTH ROLLS. 2. LOAD RATINGS ALSO APPLY FOR IMPACT ROLLS. 3. 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. Picking Idler Load Ratings (Lbs.) Belt Width CEMA C CEMA D CEMA E Liver Shaft Idler Load Capacities (Lbs.) Belt Width CEMA C CEMA D CEMA E ,2 1,200 1,000 1,000 1, ,200 1,200 1,400 2,0 1,200 1,400 2,0 1,200 1,400 2,0 1,0 1,400 2,0 1,000 1,275 2, ,150 2, ,000 2, ,0 1,825.

29 EXAMPLE: IDLER SELECTION Customer Furnished Data: Peak Load: 3,000TPH Coal at 55/ PCF minus 8" size (Maximum lump weight = 18 lbs.) " 50 FPM T1 (Belt tension carrying side) 37,000 lbs. T2 (Belt tension return side),000 lbs. Belt weight 1 lbs./ft. D (Misalignment due to installation tolerances) ¼&" H (Drop height at transfer point) ft. Conveyor system component design life 50,000 hours Requested Information: Recommended Idler Series and Spacing: 00 x 2000 WM = x 50 Optional verification of customer data = 1 lbs./ft. Reference: CEMA "Belt Conveyors for Bulk Materials", Fifth Edition (or later) A. Page 53 table 4-3: 35º Troughed belt cross section of load " 20º Surcharge = 2.87 ft 2 Full belt load: 2.87 ft 2 x 55 PCF = 158 lbs/ft. 1 Percent full load (<0) = 0 x = 7.47% 158 Since this has been identified as Peak Load the belt width, belt speed and trough angle shown, are good selections. B. Page 4 table 5-2: Suggested normal spacing of belt conveyor idlers (SI). " 50 PCF = 4.0 ft. " 75 PCF = 3.5 ft. Note: 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 = ((1+(1 x 1.0)) x 4) + K1 = 1.0 for 8 lump x 4 Per table 2-13: D x 35º = 70 lbs. rating Per table 2-: E x 35º = 1800 lbs. rating = 77 lbs. 25.

30 Note: Although it is recommended that CIL be equal to or less than CEMA Idler Load Rating, there is a certain amount of judgment involved in final 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 35º could be used and request verification from CEMA idler manufacturer. Other choices are: A. D series at less than 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 T 1 belt tension which would decrease IML. D. Customer to maintain less than ¼&" 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 35º troughing idlers at 4 ft. spacing, although optional choices C & D have great merit. Rated bearing L life is,000 hours. Step No. 2: Return Idler Series Selection Option: From "CEMA Belt Conveyor Manual" (5 th edition or later) page 4 table 5-2: suggested normal spacing of belt conveyor idler (SI) Return idlers " BW = ft.,000 x.25 CIL R = (1 x ) + x = 0 lbs. Based on above option, use preliminary selection of ft. spacing. Note: Quite often it is desirable to have return idler spacing at a multiple of troughing idler spacing to simplify stringer or truss design. However, this should not be the control for selection. Per table 2-13: D series single roll return = 280 lbs. rating Per table 2-: C series two 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 ' - 0". Rated bearing L life is,000 hours.,000 x.25 CIL R = (1 x ) + = 270 lbs. x 2.

31 Step No. 3: Impact Idler Series Selection Case of material without lumps: F = (0.138) Q H = (0.138) (00) = 1318 lbs. Assuming the impact idler spacing is 1.5 ft, from Table 2-3, f = 0.7 Fu = F (f) = (1318) (0.7) = 22. lbs. Per Table 2-13: D x = 70 lbs. rating This case requires a D series impact idler. Case of material with large lumps: WH = (18) () = 180 lbs-ft Per Table 2-4: D = 0 lbs-ft minimum energy rating Per Table 2-4: D = 8 in. maximum lump size This case requires a D series impact idler. Note: The impact idler series chosen here must satisfy both the minimum energy rating and the maximum lump size criteria from Table 2-4. Comparing the two cases, a D series impact idler should be selected to handle the heavier impact load. This step completes the impact idler selection process. Steps 1, 2 and 3 have selected idlers based on load. Steps 4, 5 and deal with predicted bearing L life and Step 7 covers conditions affecting potential idler life. Step No. 4: K2 Effect of Load on Predicted Bearing L Life CIL 77 Troughing Idler = = = Idler Load Rating 70 K2 (from Figure 2.3 Tapered Roller Bearing) = 1.0 Bearing L Return Idler = = (,000 x 1.0) =,000 hours CIL 270 = Idler Load Rating 280 K2 (from Figure 2.3 Tapered Roller Bearing) = 5 Bearing L = (,000 x 5) =,000 hours =. Step No. 5: K3A Effect of Belt Speed on Predicted Bearing L Life 50 FPM Belt speed specified. Select minimum roll dia. For < 500 RPM at 50 FPM From chart pg. 23, 5" dia. = FPM K3A (from Figure 2.) = 1.0 Bearing L life for D5 series idlers at 50 FPM Troughing idler = (,000 x 1.0) =,000 hours Return idler = (,000 x 1.0) =,000 hours 27.

32 Step No. : K3B Effect of Roll Diameter on Predicted Bearing L Life Compare bearing L life increase for diameter roll. " Dia. Roll = 1.50 K3B (Figure 2.7) = 5" Dia. Roll = 1.25 Troughing Idler = (,000 x 1.2) =,000 hours Return Idler = (,000 x 1.2) = 82,800 hours = 1.20 or 20% increase in bearing L life. Note: In addition the " roll would have longer wear life and roll resistance would be less which would decrease belt tension and reduce IML. D idlers are recommended. Idler selection based on customer furnished data. Step No. 7: Troughing idlers D x at 4 ft spacing with,000 hours predicted bearing L life. Return idlers D at ft spacing with 82,800 hours predicted bearing L life. K4 Effect of Environmental, 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.) Environmental: K4C (Figure 2.) Temperature: Good to Fair Dirty < 0 F Hostile environmental conditions and the level of commitment to the belt conveyor installation and maintenance will affect idler life. With above assumed conditions it is apparent that potential idler life will be less than predicted bearing L life. These conditions should be discussed with your CEMA idler manufacturer. Expected or potential idler life may also be limited by shell wear. Shell wear can vary considerably with each installation. In addition to conveyed material characteristics, environmental, and maintenance factors, idler alignment and belt cleaning can have a significant effect on shell wear and idler life. Note: Calculated idler loads should be repeated for training idlers (if used). Height deviation of training idlers must be included for IML calculation or controlled by shimming and maintaining closer installation tolerances at these areas of conveyor. 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. 28.

33 APPENDIX CONVERSION FACTORS TO SI-METRIC UNITS This Appendix is not part of the standard, but it is included for the information 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: inches (in) feet (ft) mass (lbs) pound-force (lbf) velocity (fpm) mass per length (lbs/ft) pounds per cubic foot (lbs/ft3) To: millimeters (mm) meters (m) kilograms (kg) newton (N) meters per sec (m/s) kilograms per meter (kg/m) kilograms per cubic meter (kg/m3) Multiply by:

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