(a) Laboratory tests for reliability and durability. Five hundred successful consecutive tests2 for gas detection, alarm action, and power shutoff in natural gas-air mixtures3 shall be conducted to demonstrate acceptable performance as to reliability and durability of a methane-monitoring system. The tests shall be conducted as follows:
2Normal replacements and adjustments shall not constitute a failure.
3Investigation has shown that, for practical purposes, natural gas (containing a high percentage of methane) is a satisfactory substitute for pure methane in these tests.
(1) The methane detector component shall be placed in a test gallery into which natural gas shall be made to enter at various rates with sufficient turbulence for proper mixing with the air in the gallery. To comply with the requirements of this test, the detector shall provide an impulse to actuate an alarm at a predetermined percentage of gas and also provide an impulse to actuate a power shutoff at a second predetermined percentage of gas. (See §§27.21, 27.22, 27.23, and 27.24.)4
4At the option of MSHA, these tests will be conducted with dust or moisture added to the atmosphere within the gallery.
(b) Field tests. MSHA reserves the right to conduct tests, similar to those stated in paragraph (a) of this section, in underground workings to verify reliability and durability of a methane-monitoring system installed in connection with a piece of mining equipment.
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