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1、NFPA 251 Standard Methods of Tests of Fire Endurance of Building Construction and Materials 1999 Edition National Fire Protection Association, 1 Batterymarch Park, PO Box 9101, Quincy, MA 02269-9101 An International Codes and Standards Organization Copyright National Fire Protection Association Prov
2、ided by IHS under license with NFPA Not for ResaleNo reproduction or networking permitted without license from IHS -,-,- Copyright National Fire Protection Association, Inc. One Batterymarch Park Quincy, Massachusetts 02269 IMPORTANT NOTICE ABOUT THIS DOCUMENT NFPA codes and standards, of which the
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27、m IHS -,-,- 2511 Copyright 1999 NFPA, All Rights Reserved NFPA 251 Standard Methods of Tests of Fire Endurance of Building Construction and Materials 1999 Edition This edition of NFPA 251, Standard Methods of Tests of Fire Endurance of Building Construction and Materials, was prepared by the Technic
28、al Committee on Fire Tests and acted on by the National Fire Protection Association, Inc., at its May Meeting held May 1720, 1999, in Balti- more, MD. It was issued by the Standards Council on July 22, 1999, with an effective date of August 13, 1999, and supersedes all previous editions. This editio
29、n of NFPA 251 was approved as an American National Standard on August 13, 1999. Origin and Development of NFPA 251 NFPA 251 originated in the recommendations of the International Fire Prevention Con- gress in London in 1903. It was presented to the NFPA by the Committee on Fire-Resistive Constructio
30、n in 1914. It was adopted officially in a revised form in 1918. Successive editions were published in 1926, 1934, 1941, 1955, 1958, 1959, 1960, 1961, 1963, 1969, 1979, 1985, and 1990. It was overseen, in succession, by the Technical Committee on Fire-Resistive Construc- tion, the Technical Committee
31、 on Building Construction, and, for the last three editions, by the Technical Committee on Fire Tests. The 1995 edition of this document was a reconfirmation of the earlier edition with only a few items being addressed. Substantial investigation and record research was done on the topic of the hose
32、stream application on test specimens. The findings of the committee did not support modification of the provision that permits a test assembly to be tested for one-half the time required for an hourly rating and then to be tested by a hose stream. The committee also modified the title of this docume
33、nt in response to the research done to convey a truer sense of the standards proper application. The 1999 edition is a reconfirmation of the 1995 edition with minor editorial modifications. 2512BUILDING CONSTRUCTION AND MATERIALS 1999 Edition Technical Committee on Fire Tests Jesse J. Beitel, Chair
34、Hughes Assoc., Inc., MD SE Patty K. Adair, American Textile Mfrs. Inst., DC M April L. Berkol, ITT Sheraton Corp., NY U Rep. American Hotel one shall be located approximately at the center of the speci- men and four shall be located approximately at the center of each quadrant. The other four thermo
35、couples shall be located at the discretion of the testing authority to obtain representa- tive information on the performance of the construction under test. (b) All of the thermocouples shall be located at a distance of at least 11/2 times the thickness of the construction or 12 in. (305 mm) from t
36、he edges of the test specimen. Exception: Distance requirements are not applicable where an element of the assembly is located near the edge only. (c) None of the thermocouples shall be located opposite or on top of beams, girders, pilasters, or other structural mem- bers if temperatures at such poi
37、nts are obviously lower than at more representative locations. (d) None of the thermocouples shall be located opposite or on top of fasteners such as screws, nails, or staples that are obviously higher or lower in temperature than at more repre- sentative locations if the aggregate area of any part
38、of such fas- teners projected to the unexposed surface is less than 1 percent of the area within any 6-in. (152-mm) diameter circle. Such fasteners shall not be required to extend through the assembly. 2400 2000 1600 1200 800 400 00 2468 1200 1000 800 600 400 Temperature (C) Temperature (F) Time (hr
39、) 1000F ( 538C)at 5 minutes 1300F ( 704C)at 10 minutes 1550F ( 843C)at 30 minutes 1700F ( 927C).at 1 hour 1850F (1010C).at 2 hours 2000F (1093C).at 4 hours 2300F (1260C).at 8 hours or over Note: The following are the points that determine the curve. 2516BUILDING CONSTRUCTION AND MATERIALS 1999 Editi
40、on 2-3.3 Temperature readings shall be measured at intervals not exceeding 1 minute. 2-3.4 Where the conditions of acceptance place a limitation on the rise of the temperature of the unexposed surface, the temperature end point of the fire endurance period shall be determined by the average of the m
41、easurements taken at indi- vidual points. Exception: Where a temperature rise of 30 percent in excess of the spec- ified limit occurs at any one of these points, all other points shall be ig- nored and the fire endurance period shall be judged as ended. 2-4 Furnace Pressure. 2-4.1 The pressure-sensi
42、ng probes shall be as shown in Figures 2-4.1(a) or 2-4.1(b). Figure 2-4.1(a) Static pressure-sensing probe dimensions. Figure 2-4.1(b) Pressure-sensing probe. 2-4.2 The pressure shall be measured using a differential pressure instrument capable of reading in increments no coarser than 0.01 in. wg (2
43、.5 Pa) with a precision of not less than 0.005 in. wg ( 1.25 Pa). The differential pressure mea- surement instrument(s) shall be located to minimize stack effects caused by vertical runs of pressure tubing between the furnace probe(s) and instrument locations. 2-4.3 The furnace pressure(s) shall be
44、measured and recorded at intervals not exceeding 1 minute throughout the test. 2-4.4 Control of the furnace pressure shall be established no later than 10 minutes after the start of the test and shall be maintained throughout the remainder of the test. For vertical specimens, the vertical pressure d
45、istribution within the furnace shall be measured by at least two probes separated by a vertical distance minimum of 6 ft (1.8 m) within the furnace. A calculation of the neutral planes (zero differential pressure) location shall be made based on the ver- tical separation of the probes and their pres
46、sure differences. The pressure measurements made inside the furnace, along with the calculation showing the position of the neutral plane with respect to the top of the vertical assembly during the test, shall be reported. For horizontal specimens, the pressure shall be measured at two locations alo
47、ng the centerline of the specimen and 12 in. (305 mm) below the specimen. The pressure (the average of the two readings) during the test shall be reported. Chapter 3Test Specimen 3-1 Specimen. 3-1.1 The test specimen shall be a true representation of the construction for which classification is to b
48、e determined with respect to materials, workmanship, and details such as dimen- sion of parts. The specimen shall be built under conditions representative of those properties that are practically applied in building construction and operation. The physical proper- ties of the materials and ingredien
49、ts used in the test specimen shall be determined and recorded. 3-1.2 The size and dimensions of the test specimen described in the standard shall be recognized as intending to apply in rating constructions of dimensions within the usual general range used in buildings. Exception: Where the conditions of use limit the construction to small- er dimensions, a proportionate reduction shall be permitted to be made in the dimensions of the specimens for a test used to qualify them for such