energy test in § 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.
(5) There shall be no water inside the blasting unit enclosure, except for the battery compartment.
§ 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.
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 ¢o an average 100 amperes is applied for 10 milliseconds; and
(3) Not fire when a current of 250 milliamperes or less is applied.
§ 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.
§ 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.
(Approved by the Office of Management and Budget under control number 1219-0100)
§ 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.
Subpart J—Electric Motor Assembles
Source: 57 FR 61193, Dec, 23, 1992, unless otherwise noted.
§ 7.301 Purpose and effective date.
This subpart establishes the specific requirements for MSHA approval of certain explosion-proof electric motor assemblies intended for use tn approved equipment in underground mines. Applications for approval or extensions of approval submitted after February 22, 1996 shall meet the requirements of this part. Those motors that incorporate features not specifically addressed in this subpart will continue to be evaluated under part 18 of this chapter.
§ 7.302 Definitions.
The following definitions apply in this subpart:
Afterburning. The combustion of any flammable mixture that is drawn into an enclosure after an internal explosion in the enclosure. This condition is determined through detection of secondary pressure peaks subsequent to the initial explosion.
