NFPA 50B-1999 Standard for Liquefied Hydrogen Systems at Consumer Sites.
2-5.2 Containers, if out of service in excess of 1 year, shall be inspected and tested as outlined in 2-5.1. The pressure relief devices shall be checked to determine if they are operable and properly set. 2-6 Liquefied Hydrogen Vaporizers. 2-6.1 The vaporizer shall be anchored and its connecting pip- ing shall be sufficiently flexible to provide for the effect of expansion and contraction due to temperature changes. 2-6.2 The vaporizer and its piping shall be protected on the hydrogen and heating media sections with pressure relief devices. 2-6.3 Heat used in a liquefied hydrogen vaporizer shall be indirectly supplied utilizing media such as air, steam, water, or water solutions. 2-6.4 A low-temperature shutoff switch or valve shall be pro- vided in the vaporizer discharge piping to prevent flow of liq- uefied hydrogen in the event of the loss of the heat source. 2-7 Electrical Systems. Electrical wiring and equipment shall be in accordance with Table 2-7 and Article 501 of NFPA 70, National Electrical Code ® . Exception No. 1: Where equipment approved for Class I, Group B at- mospheres is not commercially available, the equipment used shall meet the following requirements: (a) Purged or ventilated in accordance with NFPA 496, Standard for Purged and Pressurized Enclosures for Electrical Equipment (b) Intrinsically safe (c) Approved for Class I, Group C atmospheres Exception No. 2: Electrical equipment installed on mobile supply trucks or tank cars from which the storage container is filled. .
3-1.5 If liquefied hydrogen is located (as specified in Table 3-2.1) in a separate building, in a special room, or inside buildings where not in a special room or exposed to other occupancies, containers shall have the pressure relief devices vented unobstructed to the outdoors at a minimum elevation of 25 ft (7.6 m) above grade to a safe location as required in 2-2.3. 3-2 Specific Requirements. 3-2.1 The location of liquefied hydrogen storage, as deter- mined by the maximum total quantity of liquefied hydrogen, shall be in the order of preference indicated by the Roman numerals in Table 3-2.1. 3-2.2* The minimum distance in feet from liquefied hydro- gen systems of indicated storage capacity located either out- doors, in a separate building, or in a special room to any specified exposure shall be in accordance with Table 3-2.2. Exception: The distances in numbers 1, 4, 6, 7, 8, and 11 in Table 3-2.2 shall be permitted to be reduced by two-thirds, but not to less than 5 ft (1.5 m), for insulated portions of the systems. For uninsulated por- tions of the system, the distances shall be permitted to be reduced by the use of protective structures having a minimum fire resistance rating of 2 hours. The protective structure or the insulated liquefied hydrogen tank shall interrupt the line of sight between uninsulated portions of the liquefied hydrogen storage system and the exposure. 3-2.3 Unloading connections on delivery equipment shall not be positioned closer to any of the exposures cited in Table 3-2.2 than the distances given for the storage system. 3-2.4 The minimum distance of container fill connections from parked vehicles shall be 25 ft (7.6 m).
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