PAES 302:2000 Engineering Materials - Flat Belts and Pulleys for Agricultural Machines - PDF

PHILIPPINE AGRICULTURAL ENGINERING STANDARD PAES 302: 2000 Foreword The formulation of this National Standard was initiated by the Agricultural Machinery Testing and Evaluation Center (AMTEC) under the project entitled "Enhancing the Implementation of AFMA Through...

PHILIPPINE AGRICULTURAL ENGINERING STANDARD PAES 302: 2000 Foreword The formulation of this National Standard was initiated by the Agricultural Machinery Testing and Evaluation Center (AMTEC) under the project entitled "Enhancing the Implementation of AFMA Through Improved Agricultural Engineering Standards" which was funded by the Bureau of Agricultural Research (BAR) of the Department of Agriculture (DA). This Standard was reviewed by the Technical Committee for Study 2 – Development of Standards for Engineering Materials and was circulated to various private and government agencies/organizations concerned for their comments and reactions. These standards were presented to the Philippine Society of Agricultural Engineers (PSAE) and subjected to a public hearing organized by the National Agriculture and Fisheries Council (NAFC). The comments and reactions received during the presentation and public hearing were taken into consideration in the finalization of the standards. This Standard has been technically formulated in accordance with PNS 01:Part 4:1998 – Rules for the Structure and Drafting of Philippine National Standard. It provides specifications and proper application of drives using flat belts and does not cover manufacturing specifications. In the preparation of this standard, the following references were considered. Baumeister, Theodore (ed.) 1997. Mark’s handbook for mechanical engineers. 10th Edition. Mc Graw Hill Book Company, USA. Carmichael, C. (ed.) 1950. Kent’s Mechanical engineer’s handbook. Design and production volume. 12th Edition. John Wiley and Sons, Inc., USA. Horton, H. L. (Ed.) 1984. Machinery’s handbook. 23rd Edition. Industrial press inc., New York. PNS 647:1990, Specification for pulleys for flat transmission belts Shigley, Joseph, E. 1989. Mechanical engineering design. 3rd Edition. Mc Graw Hill Book Company, USA. Mitsuboshi Design Manuals PHILIPPPINE AGRICULTURAL ENGINEERING STANDARD PAES 302:2000 Engineering Materials – Flat Belts and Pulleys for Agricultural Machines – Specifications and Applications 1 Scope This Standard establishes specifications and provides technical information for the proper application of flat belts and pulleys for drives in agricultural machinery. 2 Reference The following normative references contains provisions which, through reference in this text, constitute provisions of this Standard: PAES 304:2000, Engineering Materials – Keys and Keyways for Agricultural Machines – Specifications and Applications 3 Application Flat belts are commonly used where center distances between pulleys are fairly long. They are very flexible and can transmit power in quarter twist and crossed drives. 4 Definitions 4.1 flat belt belts used to transmit rotary motion and power between two shafts, which lie flat on the face of its corresponding pulley 4.2 flat belt pulley wheel having flat or crowned face used to transmit motion and power by means of flat belts 4.3 flat belt drive power transmission device used to transmit power and motion between two shafts consisting of flat belts which ride in flat pulleys 4.4 pulley diameter outside diameter of the pulley 4.5 belt length stretched-out length of the belt  PAES 302:2000 4.6 speed ratio ratio of the angular velocities of the pulleys making no allowance for slip and creep 4.7 belt speed the linear speed of the belt calculated by multiplying the rpm and the diameter of the driver pulley and to the value of pi 5 Flat belts 5.1 Nomenclature Dimensions of flat belts are designated by its width (W), and by its thickness (t). 5.2 Materials Flat belts for agricultural machinery are usually made of rubberized cord and fabric and reinforced nylon cords. Flat belts may be spliced to obtain the desired loop size or made as a continuous loop. They can be arranged in layers or in plies. 5.3 Rubberized fabric 5.3.1 Description Rubber belting is made from fabric or cord, impregnated and bound together by vulcanized rubber compounds. Advantages are high tensile strength, strength to hold metal fasteners satisfactorily and resistance to deterioration by moisture. Rubber belts are used in places exposed to the weather or the action of steams. 5.3.2 Specifications Table 1 specifies the power rating (in watts per millimeter of belt width) for rubber belts given the number of ply and the types of rubber used while Table 2 specifies the minimum recommended diameters for rubber belts. Minimum and maximum number of ply is specified in Table 3. C-23 PAES 302:2000 Table 1 – Power rating of rubber belts (watts per mm of belt width) Belt Number of ply (Fabric belt) Number of ply (Hard fabric belt) Number of ply (Rayon cord belt) speed, m/min 3 4 5 6 7 8 3 4 5 6 7 8 9 10 3 4 5 6 7 8 152 21 26 35 41 47 53 21 29 38 44 50 56 62 68 47 62 76 91 106 120 305 41 56 68 82 94 106 44 59 73 88 103 117 132 147 91 120 150 18 211 241 2 457 62 82 10 120 138 156 65 88 109 132 153 173 194 214 135 179 223 27 314 358 0 0 610 79 106 13 159 182 206 85 114 144 173 203 232 261 288 176 235 297 35 414 476 2 5 762 97 129 16 194 226 255 103 138 173 208 244 279 311 343 214 288 361 43 511 584 1 5 914 114 153 19 229 264 299 120 161 203 244 285 326 364 402 252 338 426 51 599 687 1 4 1,219 144 191 23 282 329 373 150 200 250 299 349 399 449 499 311 426 537 64 763 875 8 9 1,524 164 217 27 323 376 429 170 229 288 343 399 455 511 567 352 487 619 75 890 1,022 0 5 1,829 176 232 28 343 399 455 182 244 202 261 420 479 537 596 373 523 675 82 975 1,127 8 5 2,134 179 238 267 355 414 470 526 581 361 523 690 84 1,013 1,174 8 2,438 161 214 264 314 364 414 464 514 314 481 652 81 989 1,157 9 Table 2 – Minimum pulley diameters for rubber belts (mm) Belt Number of ply (Fabric belt) Number of ply (Hard fabric belt) Number of ply (Rayon cord belt) speed, m/min 3 4 5 6 7 8 3 4 5 6 7 8 9 10 3 4 5 6 7 8 152 102 102 152 229 330 457 76 102 127 152 254 356 457 559 127 178 229 330 406 483 305 102 127 178 254 356 483 76 102 152 203 305 406 508 610 152 203 254 406 432 508 457 102 152 229 279 406 533 76 127 178 254 381 432 533 635 178 229 279 381 457 559 610 102 152 254 330 432 559 102 127 203 279 381 457 559 660 178 229 305 406 483 584 762 127 178 254 356 457 584 102 152 203 279 381 483 584 686 203 254 330 406 508 584 914 127 178 279 381 483 635 102 152 229 305 406 508 635 711 203 279 330 432 533 610 1,219 127 203 305 406 533 635 102 178 254 330 432 533 635 737 229 305 381 457 559 635 C-24  PAES 302:2000 1,524 152 229 330 457 559 686 127 178 279 381 483 584 686 787 254 305 406 483 584 660 1,829 152 254 356 483 610 737 127 203 305 406 508 610 711 838 279 356 432 533 610 711 2,134 152 229 330 457 559 686 787 889 305 381 483 584 660 762 2,438 178 305 406 533 660 787 914 1,041 330 432 533 635 737 838 C-25  PAES 302:2000 Table 3 – Minimum and maximum plies of rubber belting Width, Minimum Maximum number Minimum number Maximum Width, mm mm number of plies of plies of plies number of plies 51 3 4 406 5 8 76 3 4 457 5 8 102 3 5 508 5 8 127 4 5 559 5 8 152 4 6 607 5 8 203 4 6 660 6 8 254 4 6 762 6 10 305 4 6 914 6 10 356 5 8 1,067 6 10 5.4 Nylon cord belts 5.4.1 Description Nylon cord belts are endless belts made with single ply high tensile cords. They are oil and heat resistant. Their thin dimension allows them to be in smaller pulleys and with high-speed drives. 5.4.2 Specifications Tables 4, 5, and 6 specify the power rating of different types of nylon cord belts. Tables 7 and 8 specify the standard width and length of flat cord belts respectively. Table 4 – Power rating of section light capacity nylon cord belts, W rpm of Diameter of smaller pulley, mm smaller pulley 16 18 20 22 25 28 32 36 40 45 50 400 15 23 23 30 30 38 45 53 60 68 75 1,200 45 60 68 80 100 120 140 170 180 210 230 4,000 160 200 230 270 330 390 470 540 610 680 750 6,000 230 290 350 400 490 580 690 800 890 1,000 1,100 8,000 310 380 450 530 650 760 910 1,050 1,170 1,300 1,420 10,000 380 470 560 650 800 940 1,120 1,280 1,420 1,560 1,700 14,000 530 650 770 890 1,070 1,260 1,480 1,680 1,830 1,970 2,070 18,000 660 800 950 1,100 1,320 1,530 1,780 1,970 2,090 2,150 2,150 20,000 730 880 1,040 1,190 1,430 1,640 1,880 2,060 2,150 2,150 2,040 Table 5 – Power rating of section medium capacity nylon cord belts, W rpm of Diameter of smaller pulley, mm smaller pulley 40 45 50 56 63 71 80 90 100 300 53 75 90 120 150 180 21 230 260 900 160 220 280 360 440 530 620 700 770 1,500 260 360 470 590 740 890 1,030 1,160 1,280 3,000 520 710 920 1,180 1,460 1,760 2,030 2,270 2,510 4,500 770 1,060 1,370 1,740 2,160 2,600 2,980 3,310 3,630 6,000 1,010 1,390 1,790 2,270 2,820 3,370 3,840 4,230 4,590 7,500 1,230 1,700 2,190 2,780 3,420 4,070 4,590 5,000 5,330 10,500 1,630 2,240 2,870 3,620 4,410 5,150 5,650 5,880 5,950 13,500 1,920 2,650 3,370 4,190 5,030 5,690 5,930 15,000 2,030 2,780 3,530 4,360 5,150 5,710 Table 6 – Power rating of section high capacity nylon cord belts, W C-25 PAES 302:2000 rpm of Diameter of smaller pulley, mm smaller 80 90 100 112 125 140 160 180 200 pulley 200 150 190 230 270 320 370 430 480 530 600 450 560 670 800 950 1,100 1,280 1,440 1,600 1,000 750 920 1,110 1,340 1,570 1,830 2,130 2,390 2,650 2,000 1,490 1,840 2,200 2,630 3,100 3,590 4,160 4,640 5,100 3,000 2,200 2,710 3,230 3,860 4,520 5,230 5,990 6,610 7,170 4,000 2,870 3,530 4,200 5,000 5,810 6,660 7,520 8,150 8,660 5,000 3,500 4,280 5,070 5,990 6,920 7,830 8,660 9,140 9,380 Table 7 – Width for nylon cord belts and min. allowable pulley diameter, mm Min. allowable Recommendable Belt cross section Thickness Width diameter diameter Light capacity 1.5 16 25 10, 15, 20, 25, 30, 35, 40, 50 Medium capacity 2.5 40 56 20, 30, 40, 50, 60, 80, 100 Heavy capacity 3.5 80 125 50, 75, 100, 125, 150, 175, 200 Table 8 – Belt lengths, mm Inside Belt cross section Inside Belt cross section Inside Belt cross section length Light Medium Heavy length Light Medium Heavy length Light Medium Heavy 200 * 670 * * 1,400 * * * 224 * 710 * * 1,500 * * * 250 * 750 * * 1,600 * * * 280 * 800 * * * 1,700 * * * 315 * 850 * * * 1,800 * * * 355 * 900 * * * 1,900 * * * 400 * 950 * * * 2,000 * * * 450 * 1,000 * * * 2,240 * * 500 * * 1,060 * * * 2,500 * * 530 * * 1,120 * * * 2,800 * * 560 * * 1,180 * * * 3,150 * * 600 * * 1,250 * * * 3,550 * * 630 * * 1,320 * * * 4,000 * * * Indicates that such length is available. 5.5 Markings 5.5.1 The following information shall be marked on the belt: 1) Type of belt and its width (for endless nylon cord belts, length is indicated) 2) Manufacturer’s name and/or its trademark 5.5.2 The following information shall be marked on the packaging: 1) Type of belt and its width (for endless nylon cord belts, length is indicated) 2) Manufacturer’s name, trademark, and address 6 Flat-pulleys 6.1 Nomenclature Figure 1 shows the designation of dimensions of pulleys. C-26  PAES 302:2000 6.2 Classification Pulleys shall be classified into solid and split, by construction and into crown and level by the shape of external peripheral face (shown in Figure 1). Symbols indicating the classification are as follows: Solid – Sd Crown – C Split – St Level – L Solid Split Crowned Level Where: B is the pulley face width h is the crown height D is pulley diameter Figure 1 – Classification and designation of dimensions of flat pulleys 6.3 Materials Flat pulleys are usually made of cast iron or fabricated steel. 6.4 Specifications 6.4.1 Pulley face width, B is nominally the same as the width of the belts they are to carry. However, allowances should be made to ensure that the belt stays in the pulley. Minimum pulley diameters for rubber belts are given in Table 2. Allowances for pulley width for different belt width are given in Table 9. Table 9 – Allowances for pulley width Belt width, mm Allowance, mm Under 305 25 305 to 610 51 Over 610 76 6.4.2 Belts are made to center themselves in their pulleys by the use of crowned pulleys. The usual figure for the amount of crowning (h), is one percent or the pulley width. 6.4.3 Dimensions of flat pulleys are specified in Table 10. C-27 PAES 302:2000 Table 10 – Dimensions of flat pulleys, mm A B C D E F G H 152 102 3 5 19 11 76 10 152 152 3 5 19 11 89 13 152 203 3 5 19 11 89 13 152 305 3 5 19 11 102 13 203 102 3 5 21 11 76 10 203 152 3 5 21 11 89 13 203 203 4 6 27 14 114 13 203 305 4 6 27 14 140 13 254 102 3 5 24 14 76 13 254 152 4 6 27 14 89 13 254 203 4 6 27 14 114 13 254 305 4 6 33 16 140 16 305 102 4 6 25 11 83 13 305 152 4 6 44 13 102 13 305 203 4 6 44 13 127 16 305 305 5 8 38 19 165 16 356 102 4 6 34 13 89 13 356 152 4 6 34 13 114 16 356 203 5 8 33 14 127 16 356 305 5 8 43 21 165 16 406 102 4 6 35 14 89 13 406 203 5 8 37 16 127 16 406 305 6 9 37 16 165 19 406 406 6 9 48 24 210 22 457 102 5 8 33 14 102 16 457 203 6 9 38 17 140 19 457 305 6 9 34 17 184 22 457 508 6 10 57 32 229 22 508 102 5 8 35 16 102 16 508 203 5 8 35 16 127 19 508 305 6 9 41 19 178 19 508 508 7 11 57 29 254 25 559 102 5 8 38 16 102 16 559 203 5 8 38 16 127 19 559 305 6 9 44 21 165 22 559 508 7 11 64 32 279 29 610 102 6 9 40 17 102 16 610 203 6 9 40 17 140 19 C-28  PAES 302:2000 6.5 Pulley diameters In designing belt drives, it should be recognized that the use of larger pulley diameters will result in lower bearing loads and can result in the use of smaller and less expensive belt cross-sections. The largest possible pulley allowed by space limitations should be used so as to reduce required effective belt pull or friction force. Pulley diameters for rubber belts should conform to Table 2. Table 7 also specifies the minimum and recommendable pulleys diameters for nylon cord belts. 6.6 Markings 6.6.1 The following information shall be engraved or embossed on the pulley: 1) Classification of pulley 2) Diameter and width of the pulley 3) Manufacturer’s name and/or its trademark 6.6.2 The following information shall be marked on the packaging: 1) Classification of pulley 2) Diameter and width of the pulley 3) Manufacturer’s name, trademark, and address 7 Recommended Design Practices 7.1 Belt selection 7.1.1 The type of rubber belt to be used and the number of ply can be determined by using Table 2 given the belt speed and the pulley diameter. 7.1.2 The appropriate cross section to be used for nylon cord belts can be determined by using the belt selection chart presented in Figure 2. 7.2 Length calculations 7.2.1 The approximate belt length for an open two-pulley drive (Figure 3) may be calculated using the formula π L = 2C + (DL + DS ) + ( DL − DS ) 2 ……..………………...……………[Eq. 1] 2 4C Where: L = length of the belt (mm) C = distance between centers of pulleys (mm) DL = diameter of the large pulley (mm) DS = diameter of the small pulley (mm) C-29 PAES 302:2000 11,931 13,423 14,914 16,405 18,643 20,880 23,862 26,845 29,828 33,557 37,285 46,979 52,945 59,656 67,113 74,570 83,518 93,213 10,000 104,398 7,000 119,312 6,000 134,226 5,000 149,140 4,000 3,000 2,000 rpm of small pulley FL section FM section FH section 1,000 700 500 300 200 100 149 224 522 746 1,491 2,237 3,729 5,220 7,457 149,140 223,710 14,914 22,371 52,199 75 373 37,285 Design power, watts Figure 2 – Flat cord belt selection chart 7.2.2 For endless belts, if this calculation results in a length that is not of standard length, the next longer standard length should be used and necessary correction for center distance should be made. The center distance can be calculated from the formula: b + b 2 − 32(DL − DS ) 2 C= ………...………………………..………...[Eq. 2] 16 Where: b = 4 LS − 6.28(DL + DS ) Ls = available belt standard length 7.2.3 For crossed belts (Figure 4), the approximate belt length may be calculated using the formula π L = 2C + (DL + DS ) + ( DL + DS ) 2 ……..…….………………..….….[Eq. 3] 2 4C Where L = length of the belt (mm) C = distance between centers of pulleys (mm) DL = diameter of the large pulley (mm) DS = diameter of the small pulley (mm) C-30  PAES 302:2000 7.2.3 To determine the belt length when more than two pulleys are used on a drive (Figure 5), lay out the pulleys in terms of their effective diameters to scale in the position desired when a new belt is applied and first brought to driving tension. The length of the belt shall be the sum of the tangents and the connecting arcs around the effective diameters of the pulleys. The length of the connecting arcs can be calculated by the formula D× A Length of arc = …….……………………………………………………[Eq. 4] 115 Where D = the diameter of the pulley A = the angle in degrees subtended by the arc of belt contact on the pulley C DL DS Fig. 3 – Flat belt drive with two pulleys Fig. 4 – Crossed belt T A D Fig 5 – Flat belt drive with more than two pulleys C-31 PAES 302:2000 7.3 Correction for arc of contact Correction for arc of contact for small pulley is determined from Table 11, the arc of contact being given by the approximate formula: 60(DL − DS ) Arc of contact = 180 − ……...………………………………….…[Eq.5] C Where: DL = diameter of the large pulley DS = diameter of the small pulley C = center distance of drive. 7.4 Power rating The power rating for rubber belts are given in Table 1. Power ratings for nylon cord belts are given in Tables 4-6. The width of belts in millimeters can be calculated by the formula: H ×S W = …………………………………………………………...…….……[Eq. 6] K ×C Where W = belt width in millimeters H = actual power transmitted, or if not, the nameplate power rating S = service factor from Table 12 K = power rating of belt in watts per millimeter of belt width from Table 1 C = arc of contact factor from Table 11 Table 11 – Arc of contact factor for C Arc of contact*, deg Factor, C Arc of contact*, deg Factor, C 180 1.00 132 0.87 174 0.99 126 0.85 168 0.97 120 0.83 162 0.96 114 0.80 156 0.94 108 0.78 150 0.92 102 0.75 144 0.90 96 0.72 138 0.88 90 0.69 * For small pulley C-32  PAES 302:2000 Table 12 – Service factors, S Squirrel –cage ac motor Single- d-c Wound rotor Diesel engine, Normal phase shunt- Application High a-c motor 4 or more cyl, torque, line capacity wound torque (slip ring) above 700 rpm start motor motor Agitators 1.0-1.2 1.2-1.4 1.2 - - - Compressors 1.2-1.4 - 1.4 1.2 1.2 1.2 Belt conveyors - 1.4 - - 1.2 - Screw conveyors - 1.8 - - 1.6 - Crushing machinery - 1.6 1.4 - - 1.4-1.6 Fans, centrifugal 1.2 1.4 - 1.4 1.4 Fans, propeller 1.4 2.0 1.6 - 1.6 1.6 Generators and 1.2 - - - 1.2 2.0 exciters Line shafts 1.4 - 1.4 1.4 1.4 1.6 Machine tools 1.0-1.2 - 1.2-1.4 1.0 1.0-1.2 - Pumps, centrifugal 1.2 1.4 1.4 1.2 1.2 - Pumps, reciprocating 1.2-1.4 - 1.4-1.6 - - 1.8-2.0 8 Connectors Table 13 specifies the sizes of plate and diameter of bolt for belts using bolted plate fastener. Table 13 – Plate size based on belt width Diameter of bolt, Size of plate Belt width, mm mm 0 38-51 6 1 small 64-102 6 1 large 127-152 7 2 small 178 8 3 small 254-406 10 3 large 432-508 10 4 533-610 11 5 Above 610 13 9 Safety 9.1 Enclosing the drive with covers is recommended for safety and to avoid foreign materials from getting in contact with the drive. 9.2 Make drive inspection on a periodic basis. Drives should be inspected for the tightness of the belts, keys and setscrews. Condition of the belt should also be inspected. 9.3 Use belts with proper markings. 9.4 Use proper keys as specified in PAES 304:2000 C-33 PAES 302:2000 Annex A (Informative) Example of flat rubber belt drive selection A.1 Given parameters Assume a normal-torque squirrel-cage ac motor for a centrifugal-fan drive. The motor speed is 1,725 rpm and the pulley diameter is 127 mm. The power transmitted at the given rpm is 2,983 W. The arc of contact is 160°. Select the appropriate flat belt and the corresponding pulley to be used. A.2 Belt speed The belt speed is approximated as: π × DS × n S V = 1,000 Where: V is the belt speed DS is the diameter of the small pulley NS is the rpm of the small pulley π × DS × n S π × 127 mm × 1,725 rpm V = = = 688.24 m/min 1,000 1,000 A.3 Belt selection A.3.1 The appropriate belt for the given pulley diameter and the approximated belt speed is a 3 ply, Fabric belt (from Table 2). A.3.2 The power rating for a 3 ply, fabric belt, and at the computed belt speed is obtained from Table 1. The value is obtained by interpolating values of K between 79 and 97 m/min. This will result in a K value equal to 88.26 watts/mm. A.3.3 The arc correction factor, C, is equal to 0.93 (from Table 11) and the service factor, S, is equal to 1.2 (from Table 12). C-34  PAES 302:2000 A.3.4 The width of the belt is computed as: W = H ×S = (2,983 W × 1.2) = 43.61 mm K × C (88.26 W/mm × 0.93) Therefore, use a 44 mm width belt. A.4 Pulley width Using Table 9, the width of pulley to be used is computed as: B = belt width + allowance = 44 mm + 25 mm = 69 mm C-35