Michigan Administrative Code
Department - Licensing and Regulatory Affairs
Bureau of Fire Services
Storage and Handling of Gaseous and Liquefied Hydrogen Systems
Part 2 - STORAGE AND HANDLING OF GASEOUS HYDROGEN NFPA 50A
Chapter 3 - Location of Gaseous Hydrogen Systems
Section R. 29.7035 - Vaults for aboveground containers
Current through Vol. 24-16, September 15, 2024
Rule 35. Sections 3-3 to 3-3.2 of the storage and handling of gaseous and Liquefied H2 code are added as follows:
3-3 Vaults for aboveground containers. Vaults may be installed aboveground, underground or partially buried.
3-3.1 General. Aboveground containers may be installed in vaults that meet the requirements of section 3-3. Except as modified by the provisions of section 3-3, vaults shall meet all other applicable provisions of these rules.
3-3.2 Vault design and construction. Vaults shall be designed and constructed to meet the following requirements:
(a) The walls and floor of the vault shall be constructed of reinforced concrete at least 6 inches (15.24 centimeters) thick.
(b) The top of an aboveground vault shall be constructed of noncombustible material and shall be designed to be weaker than the walls of the vault to ensure that, in the event of any explosion, the thrust occurring inside the vault is directed upward before destructive internal pressure develops within the vault. The top of an at-grade or below-grade vault shall be designed to relieve or contain the force of any explosion occurring inside the vault. The walls of a vault, which are partially below-grade, shall extend not less than 4 feet (1.2 meters) above grade.
(c) The top and floor of a below-grade vault and the container foundation shall be designed to withstand all anticipated loading from vehicular traffic, where applicable.
(d) The walls and floor of a below-grade vault shall be designed to withstand anticipated soil and hydrostatic loading. The vault shall be liquid tight.
(e) Adjacent vault may share a common wall.
(f) The vault enclosure shall not have openings except those necessary for access to, inspection of, and filling, emptying, and venting of the container.
(g) When required, the vault shall be designed to be wind and earthquake resistant, in accordance with good engineering practice.
(h) The vault shall be provided with an open and continuous vent to provide ventilation to dilute, disperse, and remove any vapors. This continuous vent line shall terminate 12 feet (3.7 meters) abovegrade.
(i) Each vault shall be provided with a means for personal entry, which shall only be at the top of the vault to allow for the visual inspection of the container and piping surfaces. At each entry point, a warning sign that indicates the need for procedures for safe entry into a confined space shall be posted. Each entry point shall be secured against unauthorized entry and vandalism.
(j) The vault shall be provided with an approved means to admit a fire suppression agent.
(k) The loading and unloading transfer connection for abovegrade vaults shall terminate outside the vault.
(l) Provisions shall be made for the normal operation of valves without entering the vault.
(m) A vault shall be located not less than 15 feet (4.6 meters) from buildings and property lines.
(n) Container selection and arrangement. Containers shall be listed for aboveground use. Each container or manifolded system, shall be in its own vault and shall be completely enclosed by the vault, and securely fastened to the floor of the vault. Sufficient clearance between the container and the vault shall be provided to allow for visual inspection and maintenance of all the vault surfaces as well as the tank and its appurtenances.
(o) The vault shall be provided with a continuous H2 gas leak detection device with an audible alarm set at 25% of the LEL and will render the system inoperable. The H2 leak detection device shall function during system maintenance operations.
