Page 247 - Advances In Productive, Safe, and Responsible Coal Mining

226 Advances in Productive, Safe, and Responsible Coal Mining

Fig. 12.6 Stiffeners and the location of excitations applied at different cutting bits to estimate
the noise reduction yielded by these control concepts: (A) Plate stiffeners on helical vanes,
(B) L-shape stiffeners on face ring, (C) excitation near the discharge end, (D) excitation near the
center of the cylindrical body, and (E) excitation near the face side of the drum.

Sound power level reduction, dB(A) 3.5 2.7 dBA
3.7 dBA
3.5 dBA
4
3
2.5
2
1.5
1
0.5
0
Bit on vane at the Bit on vane near Bit on face ring
discharge side face ring
Fig. 12.7 Sound power level reduction for different excitation cases.

12.4.1.3 Constraints
Constraints that had to be observed during the development of noise controls for
longwall cutting drums were as follows: First, noise controls should not affect
drum-cutting performance. Second, noise controls should not affect drum-loading
ability. Both of these constraints are directly related to mine production require-
ments. In terms of structural modifications, constraints imply restrictions on