Nace CP 1, Course Manual

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Installing C.P. Components 8:13
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
07/01/04
Pipe Surface
Handle
Graphite Mold
Starting Powder
Weld Metal
Metal Disk
Copper Wire
Figure 8.12 Thermite weld process
The manufacturer’s literature specifies the proper size mold and charge for
different size wires and structures. Different alloy charges are used for steel
and cast/ductile iron structures.
Caution: Do not use larger than a 15-gram charge for carbon steel
pressure pipe. Before thermite welding to any grade of steel, however,
check your company’s standards for the proper size charge. The heat
affected zone around the weld can be hardened and thus serve as a site for
failure initiation. This is particularly true for high yield point steels.
After the weld has partially cooled, remove the welder and clean welding
slag from the weld with a chipping hammer and wire brush. Check the
security of the weld by tapping with a hammer. If the weld is not secure, or
if the wire is burned partially through, remove the wire and make a new
weld.
Thermite welding may be used for connections to above ground structures,
too. There are welders for making connections to both horizontal and
vertical surfaces.
Be certain the mold and welding surface are thoroughly dry. Damp
conditions will cause the molten metal to spatter, creating a safety hazard.