30 C.F.R. § 27.38 Tests to determine adequacy of windows and lenses.
Title 30 - Mineral Resources
Impact tests. A 4-pound cylindrical weight with a one-inch diameter hemispherical striking surface will be dropped (free fall) to strike the window or lens in its mounting or the equivalent thereof at or near the center. At least three out of four samples shall withstand the impact according to the following table: Lenses or windows of smaller diameter than 1 inch may be tested by alternate methods at the discretion of MSHA.
Title 30: Mineral Resources
PART 27—METHANE-MONITORING SYSTEMS
Subpart C—Test Requirements
§ 27.38 Tests to determine adequacy of windows and lenses.
------------------------------------------------------------------------ Height Overall lens diameter (inches) of fall (inches)------------------------------------------------------------------------Less than 4................................................... 64 to 5........................................................ 95 to 6........................................................ 15Greater than 6................................................ 24------------------------------------------------------------------------
