(d)
Hydrogen systems of less than 3,000 CF when located inside buildings and exposed to other occupancies shall be situated in the building so that the system will be as follows:
(1) In an adequately ventilated area as in paragraph (b)(3)(ii)(b) of this section.
(2) Twenty feet from stored flammable materials or oxidizing gases.
(3) Twenty-five feet from open flames, ordinary electrical equipment or other sources of ignition.
(4) Twenty-five feet from concentrations of people.
(5) Fifty feet from intakes of ventilation or air-conditioning equipment and air compressors.
(6) Fifty feet from other flammable gas storage.
(7) Protected against damage or injury due to falling objects or working activity in the area.
(8) More than one system of 3,000 CF or less may be installed in the same room, provided the systems are separated by at least 50 feet. Each such system shall meet all of the requirements of this paragraph.
(3) Design consideration at specific locations—(i) Outdoor locations.
(a) Where protective walls or roofs are provided, they shall be constructed of noncombustible materials.
(b) Where the enclosing sides adjoin each other, the area shall be properly ventilated.
(c) Electrical equipment within 15 feet shall be in accordance with subpart S of this part.
(ii) Separate buildings.
(a) Separate buildings shall be built of at least noncombustible construction. Windows and doors shall be located so as to be readily accessible in case of emergency. Windows shall be of glass or plastic in metal frames.
(b) Adequate ventilation to the outdoors shall be provided. Inlet openings shall be located near the floor in exterior walls only. Outlet openings shall be located at the high point of the room in exterior walls or roof. Inlet and outlet openings shall each have minimum total area of one (1) square foot per 1,000 cubic feet of room volume. Discharge from outlet openings shall be directed or conducted to a safe location.
(c) Explosion venting shall be provided in exterior walls or roof only. The venting area shall be equal to not less than 1 square foot per 30 cubic feet of room volume and may consist of any one or any combination of the following: Walls of light, noncombustible material, preferably single thickness, single strength glass; lightly fastened hatch covers; lightly fastened swinging doors in exterior walls opening outward; lightly fastened walls or roof designed to relieve at a maximum pressure of 25 pounds per square foot.
(d) There shall be no sources of ignition from open flames, electrical equipment, or heating equipment.
(e) Electrical equipment shall be in accordance with subpart S of this part for Class I, Division 2 locations.
(f) Heating, if provided, shall be by steam, hot water, or other indirect means.
(iii) Special rooms.
(a) Floor, walls, and ceiling shall have a fire-resistance rating of at least 2 hours. Walls or partitions shall be continuous from floor to ceiling and shall be securely anchored. At least one wall shall be an exterior wall. Openings to other parts of the building shall not be permitted. Windows and doors shall be in exterior walls and shall be located so as to be readily accessible in case of emergency. Windows shall be of glass or plastic in metal frames.
(b) Ventilation shall be as provided in paragraph (b)(3)(ii)(b) of this section.
(c) Explosion venting shall be as provided in paragraph (b)(3)(ii)(c) of this section.
(d) There shall be no sources of ignition from open flames, electrical equipment, or heating equipment.
(e) Electric equipment shall be in accordance with the requirements of subpart S of this part for Class I, Division 2 locations.
(f) Heating, if provided, shall be by steam, hot water, or indirect means.
(4) Operating instructions. For installations which require any operation of equipment by the user, legible instructions shall be maintained at operating locations.
(5) Maintenance. The equipment and functioning of each charged gaseous hydrogen system shall be maintained in a safe operating condition in accordance with the requirements of this section. The area within 15 feet of any hydrogen container shall be kept free of dry vegetation and combustible material.
(c) Liquefied hydrogen systems—(1) Design—(i) Containers.
(a) Hydrogen containers shall comply with the following: Storage containers shall be designed, constructed, and tested in accordance with appropriate requirements of the ASME Boiler and Pressure Vessel Code, section VIII—Unfired Pressure Vessels (1968) or applicable provisions of API Standard 620, Recommended Rules for Design and Construction of Large, Welded, Low-Pressure Storage Tanks, Second Edition (June 1963) and appendix R (April 1965), which is incorporated by reference as specified in § 1910.6.
(b) Portable containers shall be designed, constructed and tested in accordance with DOT Specifications and Regulations.
(ii) Supports. Permanently installed containers shall be provided with substantial noncombustible supports securely anchored on firm noncombustible foundations. Steel supports in excess of 18 inches in height shall be protected with a protective coating having a 2-hour fire-resistance rating.
(iii) Marking. Each container shall be legibly marked to indicate “LIQUEFIED HYDROGEN—FLAMMABLE GAS.”
(iv) Safety relief devices.
(a)(1) Stationary liquefied hydrogen containers shall be equipped with safety relief devices sized in accordance with CGA Pamphlet S–1, part 3, Safety Relief Device Standards for Compressed Gas Storage Containers, which is incorporated by reference as specified in § 1910.6.
(2) Portable liquefied hydrogen containers complying with the U.S. Department of Transportation Regulations shall be equipped with safety relief devices as required in the U.S. Department of Transportation Specifications and Regulations. Safety relief devices shall be sized in accordance with the requirements of CGA Pamphlet S–1, Safety Relief Device Standards, part 1, Compressed Gas Cylinders and part 2, Cargo and Portable Tank Containers.
(b) Safety relief devices shall be arranged to discharge unobstructed to the outdoors and in such a manner as to prevent impingement of escaping liquid or gas upon the container, adjacent structures or personnel. See paragraph (c)(2)(i)(f) of this section for venting of safety relief devices in special locations.
(c) Safety relief devices or vent piping shall be designed or located so that moisture cannot collect and freeze in a manner which would interfere with proper operation of the device.
(d) Safety relief devices shall be provided in piping wherever liquefied hydrogen could be trapped between closures.
(v) Piping, tubing, and fittings.
(a) Piping, tubing, and fittings and gasket and thread sealants shall be suitable for hydrogen service at the pressures and temperatures involved. Consideration shall be given to the thermal expansion and contraction of piping systems when exposed to temperature fluctuations of ambient to liquefied hydrogen temperatures.
(b) Gaseous hydrogen piping and tubing (above −20 °F.) shall conform to the applicable sections of Pressure Piping section 2—Industrial Gas and Air Piping, ANSI B31.1–1967 with addenda B31.1–1969. Design of liquefied hydrogen or cold (−20 °F. or below) gas piping shall use Petroleum Refinery Piping ANSI B31.3–1966 or Refrigeration Piping ANSI B31.5–1966 with addenda B31.5a–1968 as a guide, which are incorporated by reference as specified in § 1910.6.
(c) Joints in piping and tubing shall preferably be made by welding or brazing; flanged, threaded, socket, or suitable compression fittings may be used.
(d) Means shall be provided to minimize exposure of personnel to piping operating at low temperatures and to prevent air condensate from contacting piping, structural members, and surfaces not suitable for cryogenic temperatures. Only those insulating materials which are rated nonburning in accordance with ASTM Procedures D1692–68, which is incorporated by reference as specified in § 1910.6, may be used. Other protective means may be used to protect personnel. The insulation shall be designed to have a vapor-tight seal in the outer covering to prevent the condensation of air and subsequent oxygen enrichment within the insulation. The insulation material and outside shield shall also be of adequate design to prevent attrition of the insulation due to normal operating conditions.
(e) Uninsulated piping and equipment which operate at liquefied-hydrogen temperature shall not be installed above asphalt surfaces or other combustible materials in order to prevent contact of liquid air with such materials. Drip pans may be installed under uninsulated piping and equipment to retain and vaporize condensed liquid air.
(vi) Equipment assembly.
(a) Valves, gauges, regulators, and other accessories shall be suitable for liquefied hydrogen service and for the pressures and temperatures involved.
(b) Installation of liquefied hydrogen systems shall be supervised by personnel familiar with proper practices and with reference to their construction and use.
(c) Storage containers, piping, valves, regulating equipment, and other accessories shall be readily accessible and shall be protected against physical damage and against tampering. A shutoff valve shall be located in liquid product withdrawal lines as close to the container as practical. On containers of over 2,000 gallons capacity, this shutoff valve shall be of the remote control type with no connections, flanges, or other appurtenances (other than a welded manual shutoff valve) allowed in the piping between the shutoff valve and its connection to the inner container.
(d) Cabinets or housings containing hydrogen control equipment shall be ventilated to prevent any accumulation of hydrogen gas.
(vii) Testing.
(a) After installation, all field-erected piping shall be tested and proved hydrogen gas-tight at operating pressure and temperature.
(b) Containers if out of service in excess of 1 year shall be inspected and tested as outlined in (a) of this subdivision. The safety relief devices shall be checked to determine if they are operable and properly set.
(viii) Liquefied hydrogen vaporizers.
(a) The vaporizer shall be anchored and its connecting piping shall be sufficiently flexible to provide for the effect of expansion and contraction due to temperature changes.
(b) The vaporizer and its piping shall be adequately protected on the hydrogen and heating media sections with safety relief devices.
(c) Heat used in a liquefied hydrogen vaporizer shall be indirectly supplied utilizing media such as air, steam, water, or water solutions.
(d) A low temperature shutoff switch shall be provided in the vaporizer discharge piping to prevent flow of liquefied hydrogen in the event of the loss of the heat source.
(ix) Electrical systems.
(a) Electrical wiring and equipment located within 3 feet of a point where connections are regularly made and disconnected, shall be in accordance with subpart S of this part, for Class I, Group B, Division 1 locations.
(b) Except as provided in (a) of this subdivision, electrical wiring, and equipment located within 25 feet of a point where connections are regularly made and disconnected or within 25 feet of a liquid hydrogen storage container, shall be in accordance with subpart S of this part, for Class I, Group B, Division 2 locations. When equipment approved for class I, group B atmospheres is not commercially available, the equipment may be—
(1) Purged or ventilated in accordance with NFPA No. 496–1967, Standard for Purged Enclosures for Electrical Equipment in Hazardous Locations,
(2) Intrinsically safe, or
(3) Approved for Class I, Group C atmospheres. This requirement does not apply to electrical equipment which is installed on mobile supply trucks or tank cars from which the storage container is filled.
(x) Bonding and grounding. The liquefied hydrogen container and associated piping shall be electrically bonded and grounded.
(2) Location of liquefied hydrogen storage—(i) General requirements.
(a) The storage containers shall be located so that they are readily accessible to mobile supply equipment at ground level and to authorized personnel.
(b) The containers shall not be exposed by electric power lines, flammable liquid lines, flammable gas lines, or lines carrying oxidizing materials.
(c) When locating liquified hydrogen storage containers near above-ground flammable liquid storage or liquid oxygen storage, it is advisable to locate the liquefied hydrogen container on ground higher than flammable liquid storage or liquid oxygen storage.
(d) Where it is necessary to locate the liquefied hydrogen container on ground that is level with or lower than adjacent flammable liquid storage or liquid oxygen storage, suitable protective means shall be taken (such as by diking, diversion curbs, grading), with respect to the adjacent flammable liquid storage or liquid oxygen storage, to prevent accumulation of liquids within 50 feet of the liquefied hydrogen container.
(e) Storage sites shall be fenced and posted to prevent entrance by unauthorized personnel. Sites shall also be placarded as follows: “Liquefied Hydrogen—Flammable Gas—No Smoking—No Open Flames.”
(f) If liquified hydrogen is located in (as specified in Table H–3) a separate building, in a special room, or inside buildings when not in a special room and exposed to other occupancies, containers shall have the safety relief devices vented unobstructed to the outdoors at a minimum elevation of 25 feet above grade to a safe location as required in paragraph (c)(1)(iv)(b) of this section.
(ii) Specific requirements.
(a) The location of liquefied hydrogen storage, as determined by the maximum total quantity of liquified hydrogen, shall be in the order of preference as indicated by Roman numerals in the following Table H–3.