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The electric detonation method is implemented by a detonation network consisting of three parts: electric detonator, wire and power supply. The selection requirements for each part are as follows:
First, the choice of electric detonator In the same network, especially in large blasting, should try to use the same factory, the same model, the same batch of electric detonator, with a special bridge for resistance inspection. At present, when most mines are equipped with detonators, the resistance difference generally allows ± (0.1 ~ 0.2) Ω, the maximum does not exceed 0.25 Ω. When performing the differential detonation, it is necessary to select different milliseconds of differential electric detonators according to the detonation sequence, so that the delay is reasonable, consistent and accurate. The instantaneous power generation detonator has a certain deviation due to the delay precision, and is generally not used in the medium-deep hole blasting.
Second, select the initiation of the network wire, insulation should be good, good copper wire or aluminum wire conductors do conductivity. Aluminum core wire bending able than copper wire, but the price is cheap, the aluminum wire sheath thread peel easily oxidized, it is necessary to wipe oxide sandpaper wiring exposed metallic luster, before being coupled. In order to facilitate calculation and laying, the wires of the network are usually divided into foot lines, end lines, connecting lines, area lines and main lines according to their positions.
(A) foot line, the factory with a long detonator 2m, 0.4 ~ 0.5mm diameter copper core or iron core pin wire insulating plastic sheath.
(2) End line, which is used to lengthen or replace the original detonator foot line so that it can lead out the wire of the gun hole, or to connect the part outside the lead hole of the detonator foot line in the adjacent hole in the same string group; The length is determined according to the depth of the blasthole and the spacing of the holes. A multi-strand copper core plastic cord is commonly used.
(3) Connecting wires refer to the wires connecting the series or parallel groups, and the copper core or aluminum core plastic wire with a cross section of 2.5 to 16 mm 3 is usually used.
(4) The regional line is a wire connecting the connecting wire to the main wire, and a copper wire or an aluminum core plastic wire of 6 to 35 mm 2 is commonly used.
(5) Main line refers to the wire connecting the power supply and the regional line. Because it is not in the range of collapse, it is generally used with power cable or special blasting cable, which can be used multiple times.
In actual work, the wire size should be simplified as much as possible, and the foot line, end line, connecting line and area line of the same specification should be selected.
The wire resistance can be calculated as follows:
R=PL/S
In the formula:
R-wire resistance, Ω;
P-resistivity, Ω·mm 2 /m;
L-wire length, m;
S-wire cross-sectional area, mm 2 .
Third, the choice of power supply Electric detonation can be AC ​​power supply, but also DC power supply. Commonly used detonating power sources include detonators, lighting lines, and power lines.
(1) Detonator: The detonator has high detonation voltage, reliable detonation, simple operation and convenient carrying. It is an ideal detonating power source and is suitable for the detonation of medium and small scale engineering blasting series network.
(2) Lighting lines and power lines are all AC power sources, and the output voltages are 220V and 380V respectively. They are reliable power sources commonly used in power detonation, especially in long lines, many detonators, large doses, complex networks, and quasi-explosive current requirements. High medium and deep hole blasting is an ideal power source.
November 13, 2019