3
Heating Cable Repair
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3.1
General
• For field modifications, heating cable resistance
should be checked with an ohmmeter to ensure
that it is within ± 10% of the cable’s calculated
resistance.
Calculated resistance = heated length (ft) x Ω/foot;
(heated length (m) x Ω/meter)
Note: Ω/foot (Ω/meter) of heating cable may
be obtained from the product data sheets, H56870
for Alloy 825 sheath heating cables and H56990
for copper sheath heating cables.
• For field repairs, check continuity of both sections
of cable to be joined using the ohmmeter. If open
circuited, other faults may exist in the cable.
–
For two conductor heating cable, conductors or
tails on far end of cable may have to be shorted
together.
–
For single conductor heating cable, the conductor
or tail on far end can be shorted to the sheath and
continuity checked between the conductor and
sheath on opposite end.
• Follow appropriate repair procedure to make a
joint (Section 3.3) or end cap (Section 3.4).
• When brazing, avoid excessive heating of parts
to be joined as this can lead to embrittlement
of materials and
cause the silver solder at the
conductor joint to melt.
• Once a joint or end cap installation has
been started, it must be completed without
interruptions. This will prevent the cable from
absorbing moisture and causing a decrease in the
insulation resistance.
