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When atmospheric venting is used for the discharge of hydrogen from motor vehicle fuel storage tanks, such venting shall be in accordance with Sections 2311.8.1.2.1 through 2311.8.1.2.4.
2311.8.1.2.1 Defueling Equipment Required at Vehicle Maintenance and Repair Facilities
All facilities for repairing hydrogen systems on hydrogen-fueled vehicles shall have equipment to defuel vehicle storage tanks. Equipment used for defueling shall be listed and labeled for the intended use.
2311.8.1.2.1.1 Manufacturer's Equipment Required
Equipment supplied by the vehicle manufacturer shall be used to connect the vehicle storage tanks to be defueled to the vent pipe system.
2311.8.1.2.1.2 Vent Pipe Maximum Diameter
Defueling vent pipes shall have a maximum inside diameter of 1 inch (25 mm).
2311.8.1.2.1.3 Maximum Flow Rate
The maximum rate of hydrogen flow through the vent pipe system shall not exceed 1,000 cfm at NTP (0.47 m3/s) and shall be controlled by means of the manufacturer's equipment, at low pressure and without adjustment.
2311.8.1.2.1.4 Isolated Use
The vent pipe used for defueling shall not be connected to another venting system used for any other purpose.
2311.8.1.2.2 Construction Documents
Construction documents shall be provided illustrating the defueling system to be utilized. Plan details shall be of sufficient detail and clarity to allow for evaluation of the piping and control systems to be utilized and include the method of support for cylinders, containers or tanks to be used as part of a closed transfer system, the method of grounding and bonding, and other requirements specified herein.
2311.8.1.2.3 Stability of Cylinders, Containers and Tanks
A method of rigidly supporting cylinders, containers or tanks used during the closed transfer system discharge or defueling of hydrogen shall be provided. The method shall provide not less than two points of support and shall be designed to resist lateral movement of the receiving cylinder, container or tank. The system shall be designed to resist movement of the receiver based on the highest gas-release velocity through valve orifices at the receiver's rated service pressure and volume. Supporting structure or appurtenance used to support receivers shall be constructed of noncombustible materials in accordance with the International Building Code.
2311.8.1.2.4 Grounding and Bonding
Cylinders, containers or tanks and piping systems used for defueling shall be bonded and grounded. Structures or appurtenances used for supporting the cylinders, containers or tanks shall be grounded in accordance with NFPA 70. The valve of the vehicle storage tank shall be bonded with the defueling system prior to the commencement of discharge or defueling operations.

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