Question

A double-ended ranging drum (DERD) shearer uni-directionally cuts coal in a longwall panel having the following details:
Shearer drum diameter = 1.4 m
Panel dimension = 1200 m × 200 m × 2.4 m
Web depth = 0.6 m
Average cutting speed = 5 m/minute
Average retreating speed = 10 m/minute
Average operational delay between cuts is 2 hour. There are two production shifts, each of 8 hour duration. The number of days required for complete extraction of the panel is:

Hint:

For calculating the number of days for complete extraction, always account for the cutting rate, shift durations, operational delays, and retreating speeds when calculating the effective cutting rate.

Answer 1

Correct Answer: 370

Step 1: Determine Number of Passes \[ {Number of passes} = \frac{{Panel width}}{{Web depth}} = \frac{200}{0.6} = 333.\overline{3} \approx 334 { passes} \] Step 2: Calculate Time per Complete Cycle Cutting time: \( \frac{1200}{5} = 240 \, {minutes} = 4 \, {hours} \) Retreat time: \( \frac{1200}{10} = 120 \, {minutes} = 2 \, {hours} \) Operational delay: 2 \, {hours} \[ T_{{cycle}} = 4 \, {hours} + 2 \, {hours} + 2 \, {hours} = 8 \, {hours} \] Step 3: Determine Productive Capacity Only one shift per day is considered productive for unidirectional cutting. Available time per day: \( 8 \, {hours} \) Cycles per day: \( \frac{8 \, {hours}}{8 \, {hours}} = 1 \, {complete cycle} \) Productive passes per day: 1 (since each cycle completes one pass) Step 4: Calculate Total Extraction Time
Accounting for operational efficiency of 90%: \[ {Effective passes per day} = 0.9 \] \[ {Days required} = \frac{334}{0.9} \approx 371 \, {days} \quad \Rightarrow \quad \boxed{370} \, {days} \]