Ala. Admin. Code r. 480-3-3-.19

Current through Register Vol. 43, No. 1, October 31, 2024

Section 480-3-3-.19 - Electrical Blasting

(1)Method of Blasting_- Electric blasting with blasting machines or special blasting circuits is permissible. With blasting machines, connections shall be made in series or in a combination connection recommended by the manufacturer. With power currents, connections shall be made in series, parallel, or a combination of the two.

(2)Blasting Equipment - When blasting by means of a special blasting circuit, no one shall enter the place in which the blasting has been done until the permanent blasting wires have been disconnected from the source of electrical energy and the blasting switch has been locked in the open position.

(a) All blasting machines for generating or supplying electricity for shot firing shall, when in the mine, be in charge of a person properly instructed in blasting practice and no other person shall connect the blasting machine to the leading wires, and such connections shall not be made until all other steps preparatory to the firing shall have been completed and the men removed to a safe place.

(b) Electric power shall not be used for firing shots in a mine except when connections are made through a blasting switch as described in these rules.

(3)Electrical Blasting Required - Only electric or delay electric blasting caps shall be used:

1. In sinking shafts or winzes.

2. In cutting shaft stations.

3. In drifts, crosscuts, storage pockets, and lumps where there is not enough protection for the men from flying rock or concussion.

4. In any raise where a hazard exists in the blasting operation by reason of the unusual length of the raise or lack of stations for protection.

(4)Placing and Maintenance of Circuits - Blasting lines shall be kept well in the clear from all power and lighting lines and from all pipes, rails, etc., and shall be run on the side of the working opposite all power and lighting circuits.

(a) Grounded circuits or systems shall not be used for electric blasting.

(b) Permanent blasting lines, safety switches and blasting switches shall be maintained by a competent electrician.

(5)Leading Wires - Leading wires from portable generating blasting devices or approved type batteries shall be not less than #14 A.W.G. insulated wires except that for single shot they shall be not less than #16 A.W.G. insulated wires.

(6)Permanent Blasting Circuits - Permanent blasting wires shall be so installed and maintained that they provide the electrical current carrying capacity required by the electrical firing device. All such wires shall be in conduit, shall consist of type "S" cable or equivalent, or shall consist of two (2) rubber covered wires strung on glass insulators or porcelain knobs. If rubber covered wires are used, they shall be kept at least five (5") inches apart.

(a) All splices and joints shall be well made, clamped or soldered and taped.

(7)Wire Sizes - Connecting wires shall be not less than #20 A.W.G. insulated wires, temporary wires shall be not less than #14 A.W.G. insulated wires and bus wires shall not be smaller than #16 A.W.G. bare copper wires.

(8)Blasting - At the location where the shot firing is to be controlled, there shall be installed in the blasting circuit an approved, enclosed, externally operated pole switch with the handle or lever arranged to be locked in the 'off' position only.

(9)Safety Switch to be Used - Single Blasting Circuit: Where the blasting lines run to a single face to be blasted, a "safety" switch of the same type as required for blasting switch shall be installed between the blasting switch and the face. This switch shall be installed in a safe location guarded from flying rock.

(a) Multiple Blasting Circuit: Where a single blasting switch is used for several blasting circuits, a "safety" switch shall be installed in each circuit immediately adjacent to the blasting switch.

(10)Handling of Electrical Detonators - A blasting galvanometer or circuit tester especially designed for blasting work shall be used for testing.

(a) Leg wires of electric detonator shall be kept short circuited by means of short circuiting device or by twisting ends of leg wires together, except that the short-circuiting devices may be removed temporarily for the purpose of testing detonators with a galvanometer.

(11)Connecting up for Blasting - Before connecting the temporary wires to the leg wires, or bus wires, the ends of the temporary wires, that are to be connected to the safety switch, shall be "shorted" by being twisted together.

(a) The man making the connection at the face must have the "shorted" ends of the temporary wires in his possession and after making the connections at the face, he shall run the temporary wires to the safety switch and he shall never attach the temporary wires to the safety switch before attaching them to the leg wires or bus wires.

(b) At the safety switch, he shall untwist the temporary wires, unlock the safety switch, attach the temporary wires to the terminals of the safety switch and then place the safety switch in the "on" position. He shall then proceed to the blasting switch, unlock it, throw it in the "on" position to fire the shot then immediately return the blasting switch to the "off" position and lock it in that position.

(c) After blasting, no one shall go nearer the face that has been blasted than the safety switch until that safety switch has been opened, the temporary wires disconnected and the safety switch locked in the "off" position.

(d) No electric blasting or preparation for electric blasting shall knowingly be done during electrical storms.

(12)Precautions in Electric Blasting - No electrical equipment using direct current shall be in operation, within two hundred (200') feet of holes loaded for electric blasting or while such holes are being loaded.

(a) The minimum necessary number of men shall be at the heading or face when making the blasting connections. All other men shall be away from the heading at least as far as the safety switch.

Author: Marcus Davis, Workers' Compensation Examiner.

Ala. Admin. Code r. 480-3-3-.19

Statutory Authority:Code of Ala. 1975, § 25-2-13(2).