Vaults: Sealing, Venting, and Ventilation [49 CFR 192.187]

(A)A. Each underground vault or closed top pit containing either a pressure regulating or reducing station, or a pressure limiting or relieving station, must be sealed, vented or ventilated, as follows. [49 CFR 192.187]#

(1)1. When the internal volume exceeds 200 cubic feet (5.7 cubic meters): [49 CFR 192.187(a)]#

(a)a. the vault or pit must be ventilated with two ducts, each having at least the ventilating effect of a pipe 4 inches (102 millimeters) in diameter; [49 CFR 192.187(a)(1)]#

(b)b. the ventilation must be enough to minimize the formulation of combustible atmosphere in the vault or pit; and [49 CFR 192.187(a)(2)]#

(c)c. the ducts must be high enough above grade to disperse any gas-air mixtures that might be discharged. [49 CFR 192.187(a)(3)]#

(2)2. When the internal volume is more than 75 cubic feet (2.1 cubic meters) but less than 200 cubic feet (5.7 cubic meters): [49 CFR 192.187(b)]#

(a)a. if the vault or pit is sealed, each opening must have a tight fitting cover without open holes through which an explosive mixture might be ignited, and there must be a means for testing the internal atmosphere before removing the cover; [49 CFR 192.187(b)(1)]#

(b)b. if the vault or pit is vented, there must be a means of preventing external sources of ignition from reaching the vault atmosphere; or [49 CFR 192.187(b)(2)]#

(c)c. if the vault or pit is ventilated, Paragraphs 1 or 3 of this Subsection applies. [49 CFR 192.187(b)(3)]#

(3)3. If a vault or pit covered by Paragraph 2 of this Subsection is ventilated by openings in the covers or gratings and the ratio of the internal volume, in cubic feet, to the effective ventilating area of the cover or grating, in square feet, is less than 20 to 1, no additional ventilation is required. [49 CFR 192.187(c)]#

AUTHORITY NOTE: Promulgated in accordance with R.S. 30:501 et seq.#

HISTORICAL NOTE: Promulgated by the Department of Natural Resources, Office of Conservation, LR 9:226 (April 1983), amended LR 10:518 (July 1984), LR 27:1540 (September 2001), LR 30:1238 (June 2004).#