
[Code of Federal Regulations]
[Title 30, Volume 1]
[Revised as of July 1, 2001]
From the U.S. Government Printing Office via GPO Access
[CITE: 30CFR7]

[Page 22-28]
 
                       TITLE 30--MINERAL RESOURCES
 
  CHAPTER I--MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR
 
PART 7--TESTING BY APPLICANT OR THIRD PARTY--Table of Contents
 
Subpart D--Multiple-Shot Blasting Units

    Source: 54 FR 48210, Nov. 21, 1989, unless otherwise noted.

Sec. 7.61  Purpose and effective date.

    This subpart establishes the specific requirements for MSHA approval 
of multiple-shot blasting units. It is effective January 22, 1990. 
Applications for approval or extensions of approval submitted after 
January 22, 1991 shall meet the requirements of this subpart.

Sec. 7.62  Definitions.

    The following definitions apply in this subpart:
    Blasting circuit. A circuit that includes one or more electric 
detonators connected in a single series and the firing cable used to 
connect the detonators to the blasting unit.
    Blasting unit. An electric device used to initiate electric 
detonators.
    Normal operation. Operation of the unit according to the 
manufacturer's instructions with fully-charged batteries, with electric 
components at any value within their specified tolerances, and with 
adjustable electric components set to any value within their range.

Sec. 7.63  Application requirements.

    (a) Each application for approval of a blasting unit shall include 
the following:
    (1) An overall assembly drawing showing the physical construction of 
the blasting unit.
    (2) A schematic diagram of the electric circuit.
    (3) A parts list specifying each electric component and its 
electrical ratings, including tolerances.
    (4) A layout drawing showing the location of each component and 
wiring.

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    (5) The model number or other manufacturer's designation of the 
blasting unit.
    (b) All drawings shall be titled, numbered, dated, and include the 
latest revision number. The drawings may be combined into one or more 
composite drawings.
    (c) The application shall contain a list of all the drawings 
submitted, including drawing titles, numbers, and revisions.
    (d) A detailed technical description of the operation and use of the 
blasting unit shall be submitted with the application.

[54 FR 48210, Nov. 21, 1989, as amended at 60 FR 33723, June 29, 1995]

Sec. 7.64  Technical requirements.

    (a) Energy output. Blasting units shall meet the acceptable 
performance criteria of the output energy test in Sec. 7.66.
    (b) Maximum blasting circuit resistance. The maximum value of the 
resistance of the blasting circuit that can be connected to the firing 
line terminals of the blasting unit, without exceeding its capacity, 
shall be specified by the applicant. The specified maximum blasting 
circuit resistance shall be at least 150 ohms.
    (c) Visual indicator. The blasting unit shall provide a visual 
indication to the user prior to the operation of the firing switch when 
the voltage necessary to produce the required firing current is 
attained.
    (d) Firing switch. The switch used to initiate the application of 
energy to the blasting circuit shall--
    (1) Require deliberate action for its operation to prevent 
accidental firing; and
    (2) Operate only when the voltage necessary to produce the required 
firing current is available to the blasting circuit.
    (e) Firing line terminals. The terminals used to connect the 
blasting circuit to the blasting unit shall--
    (1) Provide a secure, low-resistance connection to the blasting 
circuit as demonstrated by the firing line terminals test in Sec. 7.68;
    (2) Be corrosion-resistant;
    (3) Be insulated to protect the user from electrical shock; and
    (4) Be separated from each other by an insulated barrier.
    (f) Ratings of electric components. No electric component of the 
blasting unit, other than batteries, shall be operated at more than 90 
percent of any of its electrical ratings in the normal operation of the 
blasting unit.
    (g) Non-incendive electric contacts. In the normal operation of a 
blasting unit, the electric energy discharged by making and breaking 
electric contacts shall not be capable of igniting a methane-air 
atmosphere, as determined by the following:
    (1) The electric current through an electric contact shall not be 
greater than that determined from Figure D-1.
    (2) The maximum voltage that can be applied across an electric 
contact that discharges a capacitor shall not be greater than that 
determined from Figure D-2.
    (3) The electric current through an electric contact that interrupts 
a circuit containing inductive components shall not be greater than that 
determined from Figure D-3. Inductive components include inductors, 
chokes, relay coils, motors, transformers, and similar electric 
components that have an inductance greater than 100 microhenries. No 
inductive component in a circuit with making and breaking electric 
contacts shall have an inductance value greater than 100 millihenries.

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[GRAPHIC] [TIFF OMITTED] TC22OC91.001


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[GRAPHIC] [TIFF OMITTED] TC22OC91.002


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[GRAPHIC] [TIFF OMITTED] TC22OC91.003

    (h) Maximum temperature. In the normal operation of the blasting 
unit, the maximum temperature of any electric component shall not exceed 
302  deg.F (150  deg.C).
    (i) Capacitor discharge. The blasting unit shall include an 
automatic means

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to dissipate any electric charge remaining in any capacitor after the 
blasting unit is deenergized and not in use.
    (j) Construction. Blasting units shall meet the acceptable 
performance criteria of the construction test of Sec. 7.67.
    (k) Locking device. The blasting unit shall be equipped with a 
locking device to prevent unauthorized use.
    (l) Enclosure. The blasting unit enclosure shall be protected 
against tampering by--
    (1) Sealing the enclosure, except the battery compartment, using 
continuous welding, brazing, soldering, or equivalent methods; or
    (2) Sealing the electric components, other than batteries, in a 
solidified insulating material and assembling the enclosure with tamper-
resistant hardware.
    (m) Battery charging. Blasting units that contain rechargeable 
batteries shall have the following:
    (1) A blocking diode, or equivalent device, in series with the 
battery to prevent electric energy in the battery from being available 
at the charging connector.
    (2) The charging connector recessed into the enclosure.

Sec. 7.65  Critical characteristics.

    The following critical characteristics shall be inspected or tested 
on each blasting unit to which an approval marking is affixed:
    (a) The output current.
    (b) The voltage cut-off time.
    (c) The components that control voltage and current through each 
making and breaking electric contact.
    (d) Operation of the visual indicator and the firing switch.

Sec. 7.66  Output energy test.

    (a) Test procedures. The blasting unit shall be tested by firing 
into each of the following resistive loads, within a tolerance of 
<plus-minus>1%:
    (1) The maximum blasting circuit resistance.
    (2) Any resistive load between 3 ohms and the maximum blasting 
circuit resistance.
    (3) One ohm.
    (b) Acceptable performance. (1) The voltage shall be zero at the 
firing line terminals 10 milliseconds after operation of the firing 
switch.
    (2) The electric current from the blasting unit shall be:
    (i) Less than 50 milliamperes except during firing of the blasting 
unit.
    (ii) Available only through the firing line terminals.
    (iii) At least an average of 2 amperes during the first 5 
milliseconds following operation of the firing switch.
    (iv) Not exceed an average of 100 amperes during the first 10 
milliseconds following operation of the firing switch.

Sec. 7.67  Construction test.

    The constuction test is to be performed on the blasting unit 
subsequent to the output energy test of Sec. 7.66.
    (a) Test procedures. (1) The blasting unit shall be dropped 20 times 
from a height of 3 feet onto a horizontal concrete floor. When dropped, 
the orientation of the blasting unit shall be varied each time in an 
attempt to have a different surface, corner, or edge strike the floor 
first for each drop.
    (2) After the blasting unit has been drop tested in accordance with 
paragraph (a)(1) above, it shall be submerged in 1 foot of water for 1 
hour in each of 3 tests. The water temperature shall be maintained 
within <plus-minus> 5  deg.F (<plus-minus>2.8  deg.C) of 40  deg.F (4.4 
deg.C), 70  deg.F (21.1  deg.C) and 100  deg.F (37.8  deg.C) during the 
tests.
    (3) Immediately after removing the blasting unit from the water at 
each temperature, the unit shall be operated first with the firing line 
terminals open circuited, then operated again with the firing line 
terminals short circuited, and last, the output energy tested in 
accordance with the output energy test of Sec. 7.66.
    (b) Acceptable performance. (1) The blasting unit shall meet the 
acceptable performance criteria of the output energy test in Sec. 7.66 
each time it is performed.
    (2) There shall be no damage to the firing line terminals that 
exposes an electric conductor.
    (3) The visual indicator shall be operational.
    (4) The batteries shall not be separated from the blasting unit.

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    (5) There shall be no water inside the blasting unit enclosure, 
except for the battery compartment.

Sec. 7.68  Firing line terminals test.

    (a) Test procedures. (1) The contact resistance through each firing 
line terminal shall be determined.
    (2) A 10-pound pull shall be applied to a No. 18 gauge wire that has 
been connected to each firing line terminal according to the 
manufacturer's instructions.
    (b) Acceptable performance. (1) The contact resistance shall not be 
greater than 1 ohm.
    (2) The No. 18 gauge wire shall not become disconnected from either 
firing line terminal.

Sec. 7.69  Approval marking.

    Each approved blasting unit shall be identified as permissible by a 
legible and permanent marking securely attached, stamped, or molded to 
the outside of the unit. This marking shall include the following:
    (a) The assigned MSHA approval number.
    (b) The maximum blasting circuit resistance.
    (c) A warning that the unit's components must not be disassembled or 
removed.
    (d) The replacement battery types if the unit has replaceable 
batteries.
    (e) A warning placed next to the charging connector that the battery 
only be charged in a fresh air location if rechargeable batteries are 
used.
    (f) A warning that the unit is compatible only with detonators that 
will--
    (1) Fire when an average of 1.5 amperes is applied for 5 
milliseconds;
    (2) Not misfire when up to an average 100 amperes is applied for 10 
milliseconds; and
    (3) Not fire when a current of 250 milliamperes or less is applied.

Sec. 7.70  Post-approval product audit.

    Upon request by MSHA, but not more than once a year except for 
cause, the approval holder shall make an approved blasting unit 
available for audit at no cost to MSHA.

Sec. 7.71  Approval checklist.

    Each blasting unit bearing an MSHA approval marking shall be 
accompanied by a description of what is necessary to maintain the 
blasting unit as approved.

[54 FR 48210, Nov. 21, 1989, as amended at 60 FR 33723, June 29, 1995]

Sec. 7.72  New technology.

    MSHA may approve a blasting unit that incorporates technology for 
which the requirements of this subpart are not applicable if the Agency 
determines that the blasting unit is as safe as those which meet the 
requirements of this subpart.
