FIRE TESTING FURNACES
STATE FIRE MARSHAL SCOPE
This standard sets forth the general requirements for the design and control of fire testing furnaces intended for fire exposure testing and assignment of fire endurance ratings of building materials, assemblies of building materials, equipment and devices.
Furnace design and dimensions
Furnaces shall consist of a furnace chamber and an insulated specimen frame. The furnace chamber walls and floor shall consist of insulating fire brick or equivalent heat-reflective materials. Furnace dimensions shall be not less than shown in the following:
- Vertical large-scale wall furnace. The furnace exposure panel or door shall consist of an insulated steel restraining frame having an available opening for the test sample of not less than 200 square feet in area with neither dimension less than 9 feet.
- Vertical half-scale wall furnace. The furnace exposure panel or door shall consist of an insulated steel restraining frame having an available opening of not less than 50 square feet for the test sample. Neither dimension of the furnace opening shall be less than 7 feet.
- Horizontal large-scale floor furnace. The furnace exposure panel shall consist of an insulated steel restraining frame having an available opening of not less than 180 square feet for the test sample. Neither dimension of the furnace opening shall be less than 12 feet.
- Horizontal small-scale furnace. The furnace exposure panel shall consist of an insulated frame having an available opening of not less than 35 square feet for the test sample. Neither dimension of the furnace opening shall be less than 5 feet.
- Horizontal large-scale beam furnace. The furnace exposure panel shall consist of an insulated steel restraining frame having an available opening of not less than 180 square feet for the test sample. Neither dimension of the furnace opening shall be less than 5 feet.
- Horizontal small-scale beam furnace. The furnace exposure panel for the “Alternate Test of Protection for Structural Steel Beams, Girders and Trusses” shall consist of an insulated steel frame having an available opening of not less than 35 square feet for the test sample. Neither dimension of the furnace opening shall be less than 5 feet.
- Column furnace. The column furnace shall be of such dimensions as to provide an opening for column sections not less than 8 feet in clear length.
- Protection of equipment and test specimen. The testing furnaces, equipment and test specimen undergoing the fire test shall be protected from any condition of wind or weather, that might lead to abnormal results. The ambient air temperature of the testing room at the beginning of the test shall be within the range of 50°F to 90°F (10°C to 32°C). Velocity of air across the unexposed face of the test specimen shall not exceed 4.4 feet per second, as determined by an anemometer placed at right angles to the unexposed surface, measured before or during the test. If mechanical ventilation is employed during the test, an airstream shall not be directed across the surface of the specimen.
BURNERS AND FUEL
- In vertical furnaces, burners shall be placed in the back wall of the furnace. The location of the burners and provisions for combustion air shall be such as to provide an even flame exposure to the entire exposed face of the test specimen. Combustion air openings shall be provided in such a manner as to normally prevent induction of combustion air through any opening in the test specimen.
- In horizontal furnaces, burners shall be placed in the floor or side walls. Burrs and the provisions for combustion air shall be so arranged as to provide a uniform exposure to the entire exposed face of the test specimen.
- In column furnaces, burners shall be placed in the four walls to provide an even luminous flame exposure to all sides of the test sample.
- Fuel. Furnaces shall be supplied with natural, manufactured or bottled gas.
The conduct of fire tests of materials, assemblies, methods of construction, equipment and devices shall be controlled to conform to the applicable portion of the standard time-temperature curve shown in Figure 12-7-3-1. The points on the curve that determine its character are:
|1000°F (538°C). . . . . . . . . . . . . . at||5 minutes|
|1300°F (704°C). . . . . . . . . . . . . . at||10 minutes|
|1500°F (843°C). . . . . . . . . . . . . . at||30 minutes|
|1700°F (927°C). . . . . . . . . . . . . . at||1 hour|
|1792°F (978°C). . . . . . . . . . . . . . at||11/2 hours|
|1850°F (1010°C). . . . . . . . . . . . . at||2 hours|
|1925°F (1052°C). . . . . . . . . . . . . at||3 hours|
|2000°F (1093°C). . . . . . . . . . . . . at||4 hours|
For a closer definition of the time-temperature curve, see Table 12-7-3A.
- Furnace thermocouples shall be protected by sealed porcelain tubes having 3/4-inch outside diameter and 1/8-inch wall thickness, or, as an alternate, in the case of base-metal thermocouples, shall be protected by 1/2-inch wrought steel or wrought iron pipe of standard weight or equivalent protection of approved type. The exposed length of the pyrometer tube and thermocouple in the furnace chamber shall be not less than 12 inches.
- In the large-scale horizontal floor and vertical wall furnaces, the temperature of the fire test exposure shall be deemed to be the average temperature obtained from the readings of not less than nine thermocouples symmetrically disposed and distributed to show the temperature near all parts of the test specimen. In the vertical half scale and horizontal small-scale furnaces, the number of thermocouples shall be proportioned to those of the large-scale furnaces, but shall in no case be less than four thermocouples.
- In the column furnace, the temperature of the fire test exposure shall be deemed to be the average temperature obtained from the readings of not less than eight thermocouples symmetrically disposed at two levels to show the temperature near all parts of the test specimen. The two levels shall be located approximately 2 feet from the top and bottom of an 8-foot clear height furnace.
- In the vertical wall furnaces, the junction of the thermo-couples shall be placed 6 inches from the exposed face of the test specimen at the beginning of the test. The junction of the thermocouples shall, during the fire test and as a result of deflection, be maintained at 6 inches from the exposed face of the test specimen.
- In horizontal beam, floor and roof furnaces having a furnace chamber not less than 180 square feet in area, the junction of the thermocouples shall be 12 inches from the exposed face of the test specimen at the beginning of the test, and shall not touch the test specimen during the test as a result of its deflection.
- In horizontal beam, floor and roof furnaces having a furnace chamber less than 180 square feet in area, the junction of the thermocouples shall be placed 6 inches from the exposed face of the test specimen at the beginning of the test and, during the test, shall not touch the test specimen as a result of its deflection.
- Temperature recording. The furnace temperatures shall be read at intervals not exceeding 5 minutes during the first 2 hours, and thereafter the intervals may be increased to not more than 10 minutes.
- Furnace control accuracy. The accuracy of the furnace control shall be such that the area under the time-temperature curve, obtained by averaging the results from the thermocouple readings, is within 10 percent of the corresponding area under the standard time-temperature curve for fire tests of 1 hour or less duration, within 7.5 percent for those over 1 hour and not more than 2 hours, and within 5 percent for tests exceeding 2 hours in duration. Individual thermocouple readings shall not exceed or fall below the standard time-temperature curve by more than 15 percent.
- Furnace pressure. The pressure in the furnace chamber during the fire test shall be maintained as nearly equal to atmospheric pressure as possible. Horizontal furnaces may be operated at a slight negative pressure sufficient to reduce haze permitting visual observation. Furnace stacks shall be equipped with dampers to facilitate maintenance of furnace pressure.
Tests of specific assemblies of materials shall be conducted for correlation (or correlation factor) of furnace exposure by comparison with tests of identical assemblies and materials conducted in furnaces of “Approved Listing Agencies” which furnaces are deemed as conforming to the design and operating requirements of this standard.
Correlation tests of wall furnaces shall include tests of two assemblies, one combustible and one noncombustible.
Correlation tests of horizontal furnaces dependent on intended test specimens shall include at least one test for each type of assembly such as combustible ceiling-floor assembly, noncombustible assembly having a high thermal capacity floor for heat dissipation, noncombustible assembly having an insulating concrete floor or other type of design.
Comparison of test results shall provide evidence of equivalent exposure based on transmitted temperatures on the unexposed side, on structural framing members, on the underside of floor or roof decks, and in the plenum space.
STANDARD TIME-TEMPERATURE CURVE FOR CONTROL OF FIRE TESTS
|TIME||AREA ABOVE 68°F BASE||AREA ABOVE 20°C BASE|
|hr.: min.||°Fahr.||°Fahr. min.||°Fahr. hr.||°Cent.||°Cent. min.||°Cent. hr.|