Question

i: A hydraulic shovel with a bottom-dump bucket with a heaped bucket volume of 5 m³ is excavating tough clay. The swing angle is 47 degrees and the job efficiency is 0.86. Calculate the shovel production in BCM

ii: Estimate the time required to load 452 m³ of gravel from a stockpile into trucks using a clamshell having a heaped bucket capacity of 0.57 m³. The estimated cycle time is 20s. Swing depth factor = 1.0. Job efficiency is estimated to be 51min/h.

iii: A small hydraulic excavator will be used to dig a trench in hard clay. The trench size is 0.76 m wide by 1.52m deep. The excavator bucket available is 0.76 m wide and has a heaped capacity of 0.51m³. The maximum digging depth of the excavator is 4.90 m. The average swing angle is expected to be 75° and the job efficiency is 71 %. Estimate the hourly trench production in BCM and in linear meters of a trench.

Answer 1

Ans i) We know,  

Shovel produuction (BCM/hr) = C x S x V x B x E x L

where, C = cycle per hour

S = swing factor

V = heaped bucked volume = 5

B = bucket fill factor

E = job efficiency = 0.86

L = Load factor = 0.77 for clay

According to table 3-6, for tough clay and bottom dump shovel, cycle per hour (C) = 140

For swing angle 47 degree, S = 1.14

For clays, fill factor (B) = 0.95

Putting values,

=> Production = 140 x 1.14 x 5 x 0.95 x 0.86 x 0.77

=> Production = 502 BCM/hr

.

Ans ii) We know,

Produuction (LCM/hr) = C x S x V x B x E

where, C = cycle per hour = 3600 sec / 20 sec = 180

S = swing factor = 1

V = heaped bucked volume = 0.57

B = bucket fill factor = 0.70 for gravel

E = job efficiency = 0.51 min/hr or 51 min/60 min = 0.85

Putting values,

  Production (LCM/hr) = 180 x 1 x 0.57 x 0.70 x 0.85

=>  Production (LCM/hr) = 61.05 LCM/hr

Given volume to be excavated = 452

=> Time required = 452 / 61.05 = 7.40 hr

.

Ans iii) We know,

Production (BCM/hr) = C x S x V x B x E x L

where, C = cycle per hour = 3600 sec / 20 sec = 180

S = swing factor = 1.21

V = heaped bucked volume = 0.51

B = bucket fill factor = 0.95

E = job efficiency = 0.71

L = Load factor = 0.77 for clay

According to table 3-3, for small excavator , cycle per hour (C) = 160

For swing angle 75 degree, S = 1.21

For clays, fill factor (B) = 0.95

Putting values,

Production (BCM/hr) = 180 x 1.21 x 0.51 x 0.95 x 0.71 x 0.77

=>  Production (BCM/hr) = 57.7 BCM/hr

Also, production per linear meter = Production in BCM/hr / (excavator width x depth)

=> Production per linear meter = 57.7/ (0.76 x 1.52)

=> Production per linear meter = 49.93 linear meter/hr