United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 92-55: Current Fire Endurance Test Results for Thermo-Lag Fire Barrier Material

                                UNITED STATES 
                         NUCLEAR REGULATORY COMMISSION
                            WASHINGTON, D.C.  20555

                                 July 27, 1992

                               THERMO-LAG FIRE BARRIER MATERIAL


All holders of operating licenses or construction permits for nuclear power


The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to inform addressees of the results of current Thermo-Lag 330 fire
endurance tests conducted for the NRC at the National Institute of Standards
and Technology (NIST).  It is expected that recipients will review the
information for applicability to their facilities and consider actions as
appropriate.  However, suggestions contained in this information notice are
not NRC requirements; therefore, no specific action or written response is


The NRC has been reviewing Thermo-Lag 330 fire barrier systems to determine
their ability to adequately perform their 1-hour or 3-hour fire resistive
functions.  The NRC has issued three information notices and a bulletin on
this subject: 

1.   Information Notice 91-47, "Failure of Thermo-Lag Fire Barrier Material to
     Pass Fire Endurance Test," August 6, 1991
2.   Information Notice 91-79, "Deficiencies in the Procedures for Installing
     Thermo-Lag Fire Barrier Materials," December 6, 1991
3.   Information Notice 92-46, "Thermo-Lag Fire Barrier Material Special
     Review Team Final Report Findings, Current Fire Endurance Tests, and
     Ampacity Calculation Errors," June 23, 1992 
4.   Bulletin 92-01, "Failure of Thermo-Lag 330 Fire Barrier System to
     Maintain Cabling in Wide Cable Trays and Small Conduits Free from Fire
     Damage," June 24, 1992

NIST conducted small scale 1-hour and 3-hour fire endurance tests to determine
the fire resistive properties of Thermo-Lag pre-formed panels.  

On July 15, 1992, NIST conducted the 1-hour fire endurance test.  The average
thermocouple reading on the unexposed surface exceeded 162.7�C (325�F) (NRC
cold side temperature limit) in approximately 22 minutes and the unexposed
surface of the material reached an average temperature of 652�C (1206�F) at 


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45 minutes.  The unexposed surface of the material exhibited visible browning
in 35 minutes.  During the test, one thermocouple on the unexposed surface
reached a peak reading of 935�C (1716�F), exceeding the corresponding furnace
temperature of 923�C (1694�F), as the material burned and added heat to the
baseline furnace temperature.  The panels burned through at two locations in
46 minutes, resulting in a corresponding drop in surface thermocouple readings
as cold air entered the furnace.  At the end of 1-hour, approximately
85 percent of the unexposed surface was blackened.  

The 3-hour test was conducted on July 17, 1992.  The average thermocouple
reading exceeded 162.7�C (325�F) in 2 hours and 20 minutes, the average
temperature at the end of 3 hours was 206�C (403�F), and the peak thermocouple
reading was 222�C (432�F).  At the conclusion of the test, the material was
soft and exhibited plastic deformation, and the fire-exposed stress skin
crumbled upon contact.  Nevertheless, visible signs of damage on the unexposed
side were limited to off-gassing, slight browning, and crystallization at the

The furnace used to conduct these tests was a natural gas-fired small scale
type with internal dimensions of 0.94 m by 0.94 m by 1.09 m (37 inches by
37 by 42.9 inches).  The top of the furnace was equipped with a frame for
supporting horizontal test specimens of up to 0.81 m by 0.81 m (31.75 inches
by 31.75 inches).  An 86.5-mm (3.375-inch) wide steel lip attached around the
lower edge of the frame supported the sample.  This lip was insulated along
its bottom, edge, and top with a nominal 13-mm (0.5-inch) thick ceramic-fiber
blanket.  Thus, the actual area of the sample exposed to the furnace was
approximately 0.584 m by 0.584 m (23 inches by 23 inches).

To conduct this series of tests, nominally square samples were cut with
dimensions from 0.794 m to 0.800 m (31.25 inches to 31.5 inches) on a side. 
After being placed in the horizontal sample frame and centered, with ribs
facing upward (i.e., the ribbed face being the unexposed face), the gaps
between the edge of the sample and the frame were loosely packed with strips
of ceramic-fiber blanket.  The test configuration used bricks placed
side-by-side along the perimeter of the sample to hold the test samples in
place.  The stress skin on the 3-hour material was thereby restrained in
compression at the edges of the panel around the lip of the furnace and
restricted from separating from the panel.

The 1-hour fire endurance test was conducted on a Thermo-Lag 330 fire-barrier
panel, "nominal" thickness 13 mm (0.5 inch).  The actual thickness of the test
sample ranged from 13.7 to 18.3 mm (0.540 to 0.720 inches).  This material had
stress skin on only the ribbed (unexposed) surface.  The three-hour fire
endurance test was conducted on a Thermo-Lag 330 fire-barrier panel, "nominal"
thickness 25 mm (1 inch).  The actual thickness of the test sample ranged from
27.7 to 39.6 mm (1.09 to 1.56 inches).  This material had stress skin on both
surfaces.  The ribbed surface was on the unexposed side during the test.

The furnace temperature was measured with three slow-response chromel alumel
thermocouples, which met the requirements in American Society for Testing and
Materials (ASTM) Standard E-119.  The furnace temperature during the tests
followed the ASTM E-119 Standard time-temperature curve..

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                                                                Page 3 of 3

The unexposed material surface temperatures were monitored at five points,
placing one thermocouple approximately at the center of the specimen, and one
at the approximate center of each of its quarter sections.  The temperature
acceptance criterion was that the temperature rise on the unexposed surface
not exceed 138.8�C (250�F) above its initial temperature of 23.9�C (75�F) as
specified in the National Fire Protection Association (NFPA) Standard 251.

The NRC will provide additional information on fire endurance testing as it
becomes available.

This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.

                                   Charles E. Rossi, Director 
                                   Division of Operational Events Assessment 
                                   Office of Nuclear Reactor Regulation   

Technical contacts:  Ralph Architzel, NRR
                     (301) 504-2804

                     Patrick Madden, NRR
                     (301) 504-2854

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