| Some
of this evidence may point toward the use of copper-based
thermite as the accelerant. Copper-based thermite is used
in railways to weld electrical cables to the tracks. Such
materials could easily have been obtained from the PATH
railway under the WTC.
EXOTHERMIC
WELDING OF HEAVY ELECTRICAL CABLES TO RAIL
Copper-based,
exothermic welding is widely used in railroad tracks
to connect
electrical cables to rail. Such welds, when properly
made, can have current-carrying capacity equal to that
of the conductor and usually require less maintenance
than certain mechanical attachments. However, studies
have shown that copper-based, exothermic welding can
produce untempered martensite in high-hardenability
rail steels. That finding is of special concern when
heavy electrical cable is welded because the cable can
be a substantial heat sink, quenching the weld and its
heat-affected zones. Transit systems would like to determine
if exothermic welding of heavy electrical cables to
the rail web is a cause of rail defect and service rail
failures.
RELATED
AAR AND AREMA MANUALS FOR COPPER-BASED, EXOTHERMIC WELDING
1. AAR Signal Manual Part 8.1.30, “Recommended
Design
Criteria for Non-Propulsion Welded-Type Railhead
Bonds,” revised 1996.
2. AAR Signal Manual Part 8.1.31, “Recommended
Design
Criteria for Copper Based Welded-Type Propulsion Railhead
Bonds,” 1996.
3. AAR Signal Manual Part 8.1.34, “Recommended
Design
Criteria for Copper Based Exothermic Welding Material,”
1996.
4. AAR Signal Manual Part 8.6.40, “Recommended
Instructions
for Application of Head-of-Rail Type Welded Bonds,”
revised 1994.
5. AREMA Manual, Chapter 33, Part 7, Section 3, “Specifi-
cation for Welded Type Rail Head U-bonds and Extended
Bonds,” 1996.
6. AREMA Manual, Chapter 33, Part 7, Section 5, “Specifi-
cation for Thermite Type Welded Rail-Head Bonds and
Track Connectors,” 1996.
7. AREMA Manual, Chapter 33, Part 7, Section 6, “Specification
for Copper Thermite Welded Electrical Connections,”
1996.
Track-Related
Research
Volume 3: Exothermic Welding of Heavy Electrical Cables
to Rail
Applicability of AREMA Track
Recommended Practices for Transit Agencies
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