30 CFR § 7.10
MSHA acceptance of equivalent non-MSHA product safety standards.
(a) MSHA will accept non-MSHA product safety standards, or groups of standards, as equivalent after determining that they:
(1) Provide at least the same degree of protection as MSHA's applicable technical requirements for a product in the subparts of this part; or
(2) Can be modified to provide at least the same degree of protection as those MSHA requirements.
(b) MSHA will publish its intent to review any non-MSHA product safety standard for equivalency in the Federal Register for the purpose of soliciting public input.
(c) A listing of all equivalency determinations will be published
in this part 7. The listing will state whether MSHA accepts the non-MSHA
product safety standards in their original form, or whether MSHA will
require modifications to demonstrate equivalency. If modifications are
required, they will be provided in the listing. MSHA will notify the
public of each equivalency determination and will publish a summary of
the basis for its determination. MSHA will provide equivalency
determination reports to the public upon request to the Approval and
Certification Center. MSHA has made the following equivalency
determinations applicable to this part 7.
(1) MSHA will accept applications for motors under Subpart J
designed and tested to the International Electrotechnical Commission's
(IEC) standards for Electrical Apparatus for Explosive Gas Atmospheres,
Part 0, General Requirements (IEC 60079-0, Fourth Edition, 2004-01) and
Part 1, Electrical Apparatus for Explosive Gas Atmospheres, Flameproof
Enclosures ``d'' (IEC 60079-1, Fifth Edition, 2003-11) (which are
hereby incorporated by reference and made a part hereof) provided the
modifications to the IEC standards specified in § 7.10(c)(1)(i)
through (ix) are met. The Director of the Federal Register approves
this incorporation by reference in accordance with 5 U.S.C. 552(a) and
1 CFR part 51. The IEC standards may be inspected at MSHA's Electrical
Safety Division, Approval and Certification Center, R.R. 1, Box 251,
Industrial Park Road, Triadelphia, West Virginia 26059 or at the
National Archives and Records Administration (NARA). For information on
the availability of this material at NARA, call 202-741-6030, or go to:
regulations/ ibr--locations.html. These IEC standards may be obtained
from International Electrical Commission, Central Office 3, rue de
Varemb[eacute], P.O. Box 131, CH-1211 GENEVA 20, Switzerland.
(i) Enclosures associated with an electric motor assembly shall be
made of metal and not have a compartment exceeding ten (10) feet in
length. External surfaces of enclosures shall not exceed 150 [deg]C
(302 [deg]F) in normal operation.
(ii) Enclosures shall be rugged in construction and should meet
existing requirements for minimum bolt size and spacing and for minimum
wall, cover, and flange thicknesses specified in paragraph(g)(19) of
§ 7.304 Technical requirements. Enclosure fasteners should be
uniform in size and length, be provided at all corners, and be secured
from loosening by lockwashers or equivalent. An engineering analysis
shall be provided for enclosure designs that deviate from the existing
requirements. The analysis shall show that the proposed enclosure
design meets or exceeds the mechanical strength of a comparable
enclosure designed to 150 psig according to existing requirements, and
that flamepath clearances in excess of existing requirements will not
be produced at an internal pressure of 150 psig. This shall be verified
by explosion testing the enclosure at a minimum of 150 psig.
(iii) Enclosures shall be designed to withstand a minimum pressure
of at least 150 psig without leakage through any welds or castings,
rupture of any part that affects explosion-proof integrity, clearances
exceeding those permitted under existing requirements along flame-
arresting paths, or permanent distortion exceeding 0.040-inch per
(iv) Flamepath clearances, including clearances between fasteners
and the holes through which they pass, shall not exceed those specified
in existing requirements. No intentional gaps in flamepaths are
(v) The minimum lengths of the flame arresting paths, based on
enclosure volume, shall conform to those specified in existing
requirements to the nearest metric equivalent value (e.g., 12.5 mm, 19
mm, and 25 mm are considered equivalent to \1/2\ inch, \3/4\ inch and 1
inch respectively for plane and cylindrical joints). The widths of any
grooves for o-rings shall be deducted in measuring the widths of flame-
(vi) Gaskets shall not be used to form any part of a flame-
arresting path. If o-rings are installed within a flamepath, the
location of the o-rings shall meet existing requirements.
(vii) Cable entries into enclosures shall be of a type that
utilizes either flame-resistant rope packing material or sealing rings
(grommets). If plugs and mating receptacles are mounted to an enclosure
wall, they shall be of explosion-proof construction. Insulated bushings
or studs shall not be installed in the outside walls of enclosures.
Lead entrances utilizing sealing compounds and flexible or rigid
metallic conduit are not permitted.
(viii) Unused lead entrances shall be closed with a metal plug that
is secured by spot welding, brazing, or equivalent.
(ix) Special explosion tests are required for electric motor
assemblies that share leads (electric conductors) through a common wall
with another explosion-proof enclosure, such as a motor winding
compartment and a conduit box. These tests are required to determine
the presence of any pressure piling conditions in either enclosure when
one or more of the insulating barriers, sectionalizing terminals, or
other isolating parts are sequentially removed from the common wall
between the enclosures. Enclosures that exhibit pressures during these
tests that exceed those specified in existing requirements must be
provided with a warning tag. The durable warning tag must indicate that
the insulating barriers, sectionalizing terminals, or other isolating
parts be maintained in order to insure the explosion-proof integrity
for either enclosure sharing a common wall. A warning tag is not
required if the enclosures withstand a static pressure of twice the
maximum value observed in the explosion tests.
(d) After MSHA has determined that non-MSHA product safety standards are equivalent and has notified the public of such determinations, applicants may seek MSHA product approval based on such non-MSHA product safety standards.