Caterpillar Performance Handbook, January 2017, SEBD0351-47

Dipper Selection

Electric Rope Shovels

DIPPER SELECTION Selecting the correct dipper size plays an integral role in maximizing productivity from a truck shovel opera- tion. Optimal dipper size is a function of truck size, material loose density, and fill factor. The first step in calculating dipper size is to deter- mine the machine’s optimal payload based on truck size. To calculate this, divide truck payload by three and four (three or four pass even loading is ideal for high productivity). Compare these values to the machine’s maximum payload. The machine’s optimal payload is the largest value that is less than the maximum payload. For example, consider a mine operating a 7495 shovel (maximum payload = 120 tons) and 797 trucks (pay- load = 400 tons). 400 ÷ 3 = 133.3 and 400 ÷ 4 = 100. 133.3 can be eliminated as it is greater than the shovel’s maximum payload (120 tons). 100 tons is the largest value less than the machine’s maximum payload, and therefore, is the machine’s optimal payload. Once optimal machine payload is determined, mate- rial loose density and fill factor are used to calculate the optimum dipper size. To calculate material loose density, divide insitu (undisturbed material density) by 1 + swell factor.

Insitu (1 + swell factor)

Material loose density =

Once material loose density is calculated, use the equa- tion below to find the optimal dipper size. Fill factor is affected by the dipper geometry, rake angle, and mate- rial properties, including fragmentation and critical angle of repose. Fill factors are generally between 90% and 115% for efficiently-sized dippers.

Optimal machine payload Material loose density

Optimal dipper size =

× Fill factor

For example: For a mine with the following conditions: Insitu: 2.276 ton/yd³ Swell factor: 35% Fill factor: 95% Optimal machine payload: 100 tons

100 tons 2.276 ÷ (1 + 0.35)

Optimal dipper size =

× .95 = 62.5 yd³

MODEL

7295

7395

7495 HD

7495

Dipper Range

19.1- 38.2 m³

20.6- 55.8 m³

27.5- 60.4 m³

30.6- 62.7 m³

25- 50 yd³

27- 73 yd³

36- 79 yd³

40- 82 yd³

MODEL

7495 HydraCrowd

7495 HF

7495 HF HydraCrowd

Dipper Range

30.6-62.7 m³

30.6-62.7 m³

30.6-62.7 m³

40-82 yd³

40-82 yd³

40-82 yd³

Information subject to change.

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