Fire Protection Patrick Thornton, SNS/FPE June 9, 2008
Code Application • ICC International Building Code 2003 • NFPA 1 Uniform Fire Code • NFPA 45 Standard on Fire Protection for Laboratories Using Chemicals • NFPA 55 Standard for the Storage, Use, and Handling of Compressed gases and Cryogenic Fluids in Portable and Stationary Containers, Cylinders and Tanks, which incorporates NFPA 50A • & 50B. NFPA 50A & 50B were cancelled in 2005. • NFPA 69 Standard on Explosion Prevention Systems • NFPA 70 National Electrical Code • NFPA 496 Standard for Purged and Pressurized Enclosures for Electrical Equipment • NFPA 497 Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical process Areas • ASME B31.3 Process Piping • ASME B31.8 Gas Transmission and Distribution Piping Systems • ASME Boiler & Pressure Vessel Code
Area Electrical Classification NFPA 70 Class 1 Zone 2 Locations. The criteria for a Zone 2 location include the following: • Ignitible mixtures are not likely to occur in normal operation, and, if they do occur, will exist only for a short period. • Ignitible mixtures are handled, processed, or used in the area, but liquids, gases, or vapors normally are confined within closed containers or closed systems from which they can escape only as a result of accidental rupture or breakdown of the containers or system, or as the result of the abnormal operation of the equipment with which the liquids or gases are handled, processed, or used. • Ignitible mixtures normally are prevented by positive mechanical ventilation, but may become hazardous as the result of failure or abnormal operation of the ventilation equipment. • The location is adjacent to a Class I, Zone 1 location, from which ignitible concentrations of flammable gases or vapors could be communicated, unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air, and effective safeguards against ventilation failure are provided.
Area Electrical Classification NFPA 497 Unclassified Locations. • Experience has shown that the release of ignitible mixtures from some operations and apparatus is so infrequent that area classification is not necessary. For example, it is not usually necessary to classify the following locations where combustible materials are processed, stored, or handled: • Locations that have adequate ventilation, where combustible materials are contained within suitable, well-maintained, closed piping systems • Locations that lack adequate ventilation, but where piping systems are without valves, fittings, flanges, and similar accessories that may be prone to leaks • Locations where combustible materials are stored in suitable containers
Area Electrical Classification Locations considered to have adequate ventilation include the following: • An outside location • A building, room, or space that is substantially open and free of obstruction to the natural passage of air, either vertically or horizontally. (Such areas could be roofed over with no walls, could be roofed over and closed on one side, or could be provided with suitably designed windbreaks.) • An enclosed or partly enclosed space provided with ventilation equivalent to natural ventilation. (The ventilation system must have adequate safeguards against failure.)
Area Electrical Classification NFPA 70 5050.8 (K) Combustible Gas Detection System. A combustible gas detection system shall be permitted as a means of protection in industrial establishments with restricted public access and where the conditions of maintenance and supervision ensure that only qualified persons service the installation. Where such a system is installed, equipment specified in 505.8(K)(1), (K)(2), or (K)(3) shall be permitted. The type of detection equipment, its listing, installation location (s), alarm and shutdown criteria, and calibration frequency shall be documented when combustible gas detectors are used as a protection technique. 505.8 (K)(3) Interior of a Control Panel. In the interior of a control panel containing instrumentation utilizing or measuring flammable liquids, gases, or vapors, electrical equipment suitable for Class I, Zone 2 locations shall be permitted. Combustible gas detection equipment shall be listed for Class I, Zone 1, for the appropriate material group, and for the detection of the specific gas or vapor to be encountered.
Area Electrical Classification Features of BL-13 which will allow unclassified status: • The liquid hydrogen target system consists of provides triple containment, the LH2 target flask, the Vacuum chamber, and Helium channels which surround the weld joints and o-ring seals in the vacuum chamber and the hydrogen piping system. • A Residual Gas Analyzer (RGA) monitoring for leaks in a weld joint or seal in the vacuum chamber, the leak can be detected immediately by helium content in the vacuum. • A pressure relief system, consisting of a relief valve and a rupture disc in parallel, to release the hydrogen gas into a relief chamber connected to a vent stack line that exhausts gas safely outside of the Building 8700 • There are no fittings in the hydrogen transfer line not included in the double contained vacuum system.
Area Electrical Classification Features of BL-13 which will allow unclassified status: • The cave atmosphere and instrument control area will be continuously monitored for the presence of hydrogen gas. If hydrogen gas is detected, alarms will sound locally and in the SNS Control Room. In addition, the gas detection system performs interlock functions of shutting down electrical equipment in the cave and evacuating hydrogen from the cryostat. • Gaseous hydrogen flow is limited by orifice restriction devices and regulators to 25 slm or less. • Only one H2 cylinder will be opened to the system at any given time, limiting total available H2 to <300 ft3. H2 cylinders only open during filling operations. • LH2 boil-off rate sufficiently low to prevent adequate accumulation of H2 to reach LEL.
Area Electrical Classification Fire Protection features required for BL-13 • Extra Hazard sprinkler protection will be provided in the instrument cave, which provides the same coverage as the main instrument hall sprinklers. • Smoke detection will be provided in the instrument cave. • It is recommended that the H2 detection system be routed into the fire alarm system to provide building notification and immediate SNS Control Room and FD notification. This would be similar to the existing HUR system on the 4th floor.