29.A.13 Blasting Machines.
- Blasting machines must be operated, maintained, tested, and inspected as prescribed by the manufacturer.
- Blasting machines must be tested prior to use and periodically thereafter as prescribed by the manufacturer.
- Blasting machines must be secured and accessible only to the blaster; only the blaster must connect the leading wire to the machine.
Blasting machines
29.A.14 When energy for blasting is taken from power circuits, the voltage must not exceed 550 volts. The wiring controlling arrangements must conform to the following (see Figures 29-1 and 29-2):
Figure 29-1
Figure 29-2
- The blasting switch must be an ungrounded UL (or other nationally-recognized testing laboratory) listed, enclosed, externally operated double-pole double-throw switch that, when locked in the open position, will shunt the firing lines.
- A grounded switch must be installed between the blasting switch and the power circuit at a distance not less than 15 ft (4.5 m) from the blasting switch.
- A lightning gap of at least 15 ft (4.5 m) must be provided between the two switches; the gap connection must be made by cable, plug, and receptacle.
29.A.15 The cable between switches must be disconnected and both switches must be locked in the open position immediately after firing the shot.
29.A.16 Keys to the switches must remain in the possession of the blaster at all times.
29.A.17 Insulated solid core wires of an appropriate gage in good condition must be used for all lines.
29.A.18 Sufficient firing line must be provided to permit the blaster to be located at a safe distance from the blast.
29.A.19 Mechanized equipment (including drills) must not be operated within 50 ft (15.2 m) of a loaded hole.
Exception: Mechanized equipment may be permitted to operate within 50 ft (15.2 m) of a loaded hole when placing blasting mats or back covering.
29.A.20 The use of black powder is prohibited.
29.A.21 All refuse from explosive loading such as empty boxes, paper, and fiber packing must not be used again for any purpose, but must be destroyed by burning at an approved location
.Knowledge Check Choose the best answer for the question.
29-3. Which of the following is allowed during blasting operations?
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