Improvements in load design and/or conveyor equipment may be required if belting is prematurely failing from material impact. Indications of an impact problem include:

1. Breaks in belt parallel to belt angle
2. Star breaks to top cover
3. Gouges in top cover
4. Failure of mechanical lacing from physical abuse

To calculate number of plies required, first determine the lump weight factor (Table E₁), including calculated variables, and then determine minimum plies to withstand impact from Tables E₂ or E₃.

Table E₁ -- Lump Weight Factor in Pounds

Density Lump Size -- Inches lbs ft3 2 3 4 5 6 7 8 9 10 12 14 16 18 50 0.4 1.3 3.0 5.8 10 14 21 30 40 70 100 148 211 75 0.6 1.9 4.5 8.6 15 21 31 44 61 105 149 222 316 100 0.7 2.6 5.9 12 20 28 41 59 81 140 199 296 421 125 0.9 3.2 7.4 14 25 35 52 74 101 175 248 371 527 150 1.1 3.8 9 17 30 42 62 89 121 210 298 444 632 175 1.3 4.5 10.4 20.2 35 49 73 104 142 245 348 518 737

Density may be determined from Table E₄. Table E₁ may be used to determine lump weight factor that must be adjusted as follows:

1. If free fall is different than 4 feet, divide Lump Weight Factor by 4 and multiply by free fall of material in feet.
   
2. If material momentum includes a chute preceeding free fall, add to the above the value determined by multiplying the distance of drop in chute area times the size of the chute angle squared.
   [Additional factor = h (sine Angle in degrees)²]
    
3. If large lumps exceed 10% of material, add one more ply to minimum table rating (E₂).
    
4. If impact idlers are not used, multiply the lump factor by 2 for belts 4-ply and less, by 1.25 for 5-ply belts, and 1.15 for 6-ply and over belts.

For multiple-ply belts, use calculated lump factor to determine minimum number of plies to resist impact from Table E₂. For reduced-ply belts, use Table E₃.

Table E₂
Maximum Impact Rating Multiple-Ply Belts

MP Fabric Identification Number of Plies 35 43 50 60 & 70 90 240 3 8 16 20 38 48 4 16 28 38 62 80 5 40 60 75 175 320 6 120 160 210 475 700 7 240 320 410 775 1060 8 - 520 660 1050 1440

Table E₃
Maximum Impact Rating Reduced-Ply Belts

Number of Plies 75 105 125 150 2 10 20 45 110 3 60 105 200 290 4 150 280 430 600 5 300 500 800 1000

• NOTE: Individual belting manufacturers should be consulted for recommendations on proper reduced-ply belting impacted resistance