3
Heating Cable Repair
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Note: Do not remove more than 3% of length
of heated section. If more than 3% must be
removed to facilitate the repair or modification,
a new MI cable tag must be ordered (see Section
2.3).
If the bell-mouth is not re-used, care must be taken
not to bend the cable at the joint as this will break
the cable at the new braze.
Note: If replacing a 5/8 in (15.9 mm) diameter
joint with a new 3/4 in (19 mm) diameter joint, it
will not be possible to reuse the 5/8 in (15.9 mm)
bell-mouth.
If heated section and/or cold lead section is polymer
jacketed, remove heat shrink tubing and strip back 6
in (15 cm) of the jacket from each end, taking care
not to nick or damage the copper sheath.
6 in.
Figure 11: Remove polymer jacket
Check the insulation resistance (IR) of the cable
at this point using a 500 volt Megohmmeter (see
Appendix B for details on testing). This test checks
for the presence of moisture in the magnesium
oxide insulation. A value greater than 20 MΩ should
be attained before proceeding. If the IR is lower,
remove the moisture from the cable by following the
drying out
procedure in Appendix D. Repeat IR test.
Note: If the insulation resistance (IR) for a
polymer jacketed cable is still low after drying out
the cable
(see Appendix D), it will be necessary to remove
a a longer length of the polymer jacket and begin
drying out the cable further back from the end.
