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1、NFPA 257 Standard on Fire Test for Window and Glass Block Assemblies 2000 Edition National Fire Protection Association, 1 Batterymarch Park, PO Box 9101, Quincy, MA 02269-9101 An International Codes and Standards Organization The Standard is downloaded from Standard Sharing Copyright National Fire
2、Protection Association, Inc. One Batterymarch Park Quincy, Massachusetts 02269 IMPORTANT NOTICE ABOUT THIS DOCUMENT NFPA codes, standards, recommended practices, and guides, of which the document contained herein is one, are developed through a consensus standards development process approved by the
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25、 document. (For further explanation, see the Policy Concerning the Adoption, Printing, and Publication of NFPA Documents, which is available upon request from the NFPA.) The Standard is downloaded from Standard Sharing 2571 Copyright 2000 NFPA, All Rights Reserved NFPA 257 Standard on Fire Test for
26、 Window and Glass Block Assemblies 2000 Edition This edition of NFPA 257, Standard on Fire Test for Window and Glass Block Assemblies, was pre- pared by the Technical Committee on Fire Tests and acted on by the National Fire Protection Association, Inc., at its November Meeting held November 1417, 1
27、999, in New Orleans, LA. It was issued by the Standards Council on January 14, 2000, with an effective date of February 11, 2000, and supersedes all previous editions. This edition of NFPA 257 was approved as an American National Standard on February 11, 2000. Origin and Development of NFPA 257 This
28、 standard was tentatively adopted by the NFPA in 1969 and officially adopted in 1970. Subsequent revisions were released in 1975, 1980, 1985, and 1990. The 1996 edition of NFPA 257 was a complete rewrite that included editorial and technical revisions. Many of the editorial and technical revisions w
29、ere made to parallel those of NFPA 252, Standard Methods of Fire Tests of Door Assemblies. The technical revisions included modifica- tions to the furnace pressure. The neutral pressure was eliminated so that the test assembly could be tested to the pressure required by other code requirements (i.e.
30、, NFPA 101, Life Safety Code, and the model building codes). In addition, the duration of the test method was extended beyond the 45 minutes required in previous editions to allow for the testing of new glazing materials. The 2000 edition was completely revised for the purpose of consistency and edi
31、torial refor- matting. This document was modified so that the test protocols and equipment used will be more consistent with the provisions found in NFPA 251, Standard Method of Tests of Fire Endur- ance of Building Construction and Materials, and NFPA 252, Standard Method of Fire Tests of Door Asse
32、mblies. This revision recognizes the positive pressure testing required by some of the model building codes. It also provides greater clarification on how to conduct the hose stream test to achieve greater repeatability and reproducibility. The Standard is downloaded from Standard Sharing 2572FIRE
33、TEST FOR WINDOW AND GLASS BLOCK ASSEMBLIES 2000 Edition Technical Committee on Fire Tests Jesse J. Beitel, Chair Hughes Assoc. Inc., MD SE Patty K. Adair, American Textile Mfrs., Inst., DC M April L. Berkol, Starwood Hotels and Resorts, Inc., NY U Rep. American Hotel NFPA 252, Standard Methods of Fi
34、re Tests of Door Assemblies; and ASTM E 814, Stan- dard Test Method for Fire Tests of Through-Penetration Fire Stops. Although the temperaturetime curve is specified for stan- dard thermocouples located within the furnace, measurement of the temperaturetime curve using standard thermocouples does no
35、t establish a standard incident heat flux on the tested specimen. Incident heat flux that occurs in an actual fire can vary significantly from that developed by tests conducted by this standard test method. Similarly, this standard provides for a standard temperaturetime relationship to be followed
36、by all furnaces using this standard method, although the internal heat flux developed in various test furnaces can vary. B-7 Furnace Control. This standard contains specific instruc- tions for measuring temperatures in the furnace and for the selection of required thermocouples. Thermocouples of the
37、 design specified are sufficiently rugged to retain accuracy throughout anticipated test periods. However, their massive construction results in a significant time delay in response to temperature change, causing actual temperatures that exceed the indicated temperatures during the early stages of t
38、he test period, when the temperature rises rapidly. The iron or porcelain tubes surrounding the junction and leads of the thermocouple provide a shield against degrada- tion of the junction and increase thermal inertia. Depending on the type of thermocouple used and its method of protec- tion, some
39、laboratories replace furnace thermocouples after accruing 3 or 4 hours of use. B-8 Test Assemblies. Fire window assemblies are tested in rel- atively large sizes compared to most side-hinged swinging fire doors for example, 100 ft2 (9.3 m2) for windows versus 2040 ft2 (6.112.2 m2) for doors. The siz
40、e of individual panes of glazing material is determined by the designer. Fire window assemblies as large as 150 ft2 (13.9 m2) have been tested. When the size of any assembly is less than 100 ft2 (9.3 m2), it should be reported. B-9 Conduct of the Tests. The test frame or wall in which a fire window
41、assembly is installed should be rugged enough to endure the fire exposure during the test period without affect- ing the window assembly. Traditionally, this wall has been of masonry construction. Currently, fire windows are installed in walls of other than masonry construction and have been tested
42、in such walls as well. B-10 Furnace Pressures. A fire in a building compartment creates both negative and positive pressures on window assem- blies, depending on the following: (1) Atmospheric conditions (2) Height above ground (3) Wind conditions (4) Ventilation of the compartment at the beginning
43、of the fire (5) Ventilation during the fire A furnace pressure that is slightly higher than the ambient pressure outside of the furnace could have a significant impact on the performance of fire barrier assemblies. Operating a test furnace at a negative pressure differential has the effect of drawin
44、g any hot gases or flames back into the furnace cham- ber, so the ability to observe flaming around any openings on the unexposed surface is minimized. Furthermore, the draft induced by the negative pressure differential reduces any heating that might occur along the edges of any openings and, in fa
45、ct, provides some degree of cooling of surfaces. Positive compartment pressures in actual fires have the opposite effect. In previous editions, NFPA 257 specified that the pressure in the furnace should be maintained as nearly equal to atmo- spheric as possible. This method of test generally resulte
46、d in the test assemblys subjection to a negative pressure during the test because most laboratories set the neutral plane in the fur- nace at or above the top of the assembly. As revised, the stan- dard now permits tests to be conducted under any pressure situation, depending on the needs or require
47、ments of the manufacturer, the test laboratory, or the authority having jurisdiction. The pressure in the furnace is required to be measured and reported. The differential pressure employed is the pressure that is necessary to evaluate the fire window assembly with respect to its field installation.
48、 The differential pressure should be deter- mined by one of the following: (1) Code requirements (2) The design pressure that can occur in the type of installa- tion for which the test is proposed (3) The test sponsor (4) Other circumstances B-11 Hose Stream Test. Immediately following the fire test
49、, the test assembly is removed from the furnace, and the fire win- dow assembly is subjected to the impact, erosion, and cooling effects of a stream of water. The water discharges from a 21/2-in. (63.5-mm) hose through a standard play pipe, equipped with a 11/8-in. (28.5-mm) tip, under a specified pressure for a speci- fied duration based on the length of the fire test and the area of the fire window assembly. The application of water produces stresses in the assembly and provides a measure of its structural cap