30 CFR § 7.302
The following definitions apply in this subpart:
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 occurring
subsequent to the initial explosion.
A joint comprised of two contiguous, concentric,
A metallic enclosure used as a winding
compartment, conduit box, or a combination of both that complies with the
applicable requirements of §7.304
of this part and is
constructed so that it will withstand the explosion tests of
of this part.
A bolt, screw, or stud used to secure adjoining parts to prevent
the escape of flame from an explosion-proof enclosure.
Two or more adjoining or adjacent surfaces between
which the escape of flame is prevented.
Internal free volume (of an empty enclosure).
The volume remaining after
deducting the volume of any part that is essential in maintaining the
explosion- proof integrity of the enclosure or necessary for operation of
the motor. Essential parts include the parts that constitute the
flame-arresting path and those necessary to secure parts that constitute a
The winding compartment including a conduit box when
specified. A motor assembly is comprised of one or more explosion- proof
A joint comprised of two adjoining surfaces in parallel
Step (rabbet) joint.
A joint comprised of two adjoining surfaces with
a change or changes in direction between its inner and outer edges. A step
joint may be composed of a cylindrical portion and a plane portion or of two
or more plane portions.
An entrance with a recess filled with packing material for
cables extending through a wall of an explosion-proof enclosure.
A joint consisting of a male- and a female-threaded member,
both of which are the same type and gauge.
[57 FR 61193, Dec. 23, 1992]