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Appendix D:
Drying Out Procedure
IMPORTANT: Wear full face shield when drying
out MI cable.
Damage to the cable sheath or a damaged or missing
joint or end cap will cause the magnesium oxide insulation
(white powder) to absorb moisture, resulting in low IR
readings. The cable must be "heated out" to remove the
moisture and bring the IR back to an acceptable level.
If moisture is detected in the cable, use the oxy-acetylene
torch with a large sizzling flame (Appendix E) and dry out the
cable beginning 12 in ( 30 cm) back from the joint or end cap
(heat cold lead first if making a hot-cold joint). If repairing
polymer jacketed heating cable and/or cold leads, begin 4 in
(10 cm) back from the joint or end cap to avoid melting the
polymer jacket. Alloy 825 sheath cable should be heated to a
dull red color and copper sheath cables should be heated to a
bluish-gray color.
Use a short sweeping motion of the torch and heat about
2 in (5 cm) of cable at a time, repeating 4 to 5 times. Move
the flame towards the joint or end cap as shown in Figure
D1. Do not sweep the flame in the opposite direction as this
will drive the moisture into the cable.
Figure 68: Use sweeping motion of torch
52 | nVent.com
2 in (50 mm)
Repeat 4 to 5 times
Joint
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