30 CFR § 36.46 Explosion tests of intake and exhaust systems.
(a) Explosion tests to determine the strength of the intake and
exhaust systems to withstand internal explosions and the adequacy of the
flame arresters to prevent the propagation of an explosion shall be made with
the systems connected to the engine or the systems simulated as connected to
the engine. The system shall be filled with and surrounded by an explosive
natural gas-air mixture. The mixture within the intake and exhaust systems
shall be ignited by suitable means and the internal pressure developed by
the resultant explosion shall be determined. Tests shall be conducted with
the ignition source in several different locations to determine the maximum
pressure developed by an internal explosion.
(b) Explosion tests shall be made with the engine at rest and with
the flammable natural gas-air mixtures in the intake and exhaust systems. In
other tests with the flammable mixture in motion, the engine shall be driven
(externally) at speeds prescribed by MSHA but no liquid fuel shall be
supplied to the injection valves.
(c) The temperature of the flame arresters in the intake or exhaust
systems shall not exceed 212° F. when an explosion test is conducted. Any
water-spray cooling for the exhaust system shall not be operated and water
shall not be present in the exhaust cooling boxes except when water is the
cooling agent for a cooling box designed to act as a flame arrester, in
which case MSHA will prescribe the test conditions.
(d) The explosion tests of the intake and exhaust systems shall not
(1) Discharge of visible flame from any joint or
(2) Ignition of surrounding flammable gas-air mixture.
(3) Development of dangerous afterburning.4
4 The term "afterburning" as used in this part is
applied to combustion of a flammable gas-air mixture drawn into the system
under test by the cooling of the products from an explosion in the
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