Raychem nvent MI Series User manual

Mineral Insulated Cable
Heating Cable Repair Guide

Important Safeguards
WARNING: Fire and shock hazard. nVent RAYCHEM
heating cables must be installed correctly to ensure
proper operation and to prevent electrical shock and
fire. Read these important warnings and carefully
follow all the installation instructions.
• To minimize the danger of fire from sustained
electrical arcing if the heating cable is damaged
or improperly installed, and to comply with the
requirements of nVent, agency certifications, and
national electrical codes, ground-fault equipment
protection must be used on each heating cable branch
circuit. Arcing may not be stopped by conventional
circuit protection.
• Damaged heating cable can cause electrical arcing or
fire. Repair or replace damaged heating cable or
terminations. Contact factory for assistance.
• To prevent shock or personal injury, discon-
nect allpower before repairing or modifying the
heatingcable.
• When drying out cable, care must be taken not to trap
moisture as this could cause the cable to burst, pos-
sibly causing injury.

Table of Contents
1 General Information 1
1.1 Introduction 1
1.2 Safety Guidelines 2
1.3 Electrical Codes 2
1.4 Heating Cable Configurations 2
1.5 Heating Cable Identification 3
2 Pre-Repair Information 4
2.1 General 4
2.2 Safety Precautions 4
2.3 Changes to the Heating Cable Length 5
2.4 Tools and Materials Required 6
2.5 Repair Kit Components 7
2.6 Cross-section of Completed Joints and End Cap 9
3 Heating Cable Repair 11
3.1 General 11
3.2 Selecting the Correct Size of Joint and/or End Cap 12
3.3 Joining Design B, D, and E Cables 14
3.4 End Cap Procedure 34
4 Appendix A:
Field Modification Approval Request Form 46
5 Appendix B:
Heating Cable Testing 48
5.1 Testing 48
5.2 Insulation Resistance (Megohmmeter) Test – Test 1 48
5.3 Continuity (Resistance) Test – Test 2 49
6 Appendix C:
Cable Size vs Drill Bit Selection Chart 51
7 Appendix D:
Drying Out Procedure 52

8 Appendix E:
Flame Size for Oxy-acetylene Torch 54
9
Appendix F:
Heat Shrink Tubing Installation for Polymer
Jacketed Cables 55
9.1 Cables using a 1/2 in (13 mm) joint 55
9.2 Installation for end cap 57
10 Appendix G:
Stripping the Cable Sheath 58
11 Appendix H:
Typical Repair Jig 61

1
General Information
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1.1 Introduction
The purpose of these instructions is to provide
a procedure for the repair or modification of
RAYCHEM Copper and Alloy 825 sheath mineral
insulated (MI) heating cables manufactured
by nVent. They must be carefully followed to
ensure that the MI cable performs safely and
asintended.
During the installation of MI cables or during
plant maintenance processes, the cables are
occasionally damaged, cut or broken. It is usually
impractical to remove these cables and return
them to the manufacturer for repair. The field
repair of these cables is therefore, the only
feasible alternative.
The successful repair or modification of
these cables is a specialized procedure, and
as such, only qualified personnel at industrial
establishments, with the necessary competency,
are permitted to repair or modify MI heating
cable sets. Where the work involves a change to
the existing design, participation in the redesign
is required by the manufacturer; or alternately,
the design may be carried out by a professional
engineer using design tools provided by the
manufacturer.
For assistance, technical support, or other
information regarding the repair of RAYCHEM MI
cables, please contact your nVent representative
or nVent directly.
nVent
7433 Harwin Drive
Houston, TX 77036
USA
Tel [phone]
Fax [phone]
[email protected]
nVent.com

General Information
1
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1.2 Safety Guidelines
The safety and reliability of any heat tracing
system depends on both the quality of the
products selected and the manner in which
they are installed and maintained. Incorrect
design, handling, installation, or maintenance
of any of the system components can cause
damage to the heating cable system, and may
result in system failure, electric shock, or fire.
The guidelines and instructions contained in this
manual are important. Follow them carefully to
minimize these risks and to ensure that the MI
system performs reliably.
1.3 Electrical Codes
Refer to the appropriate sections of the National
Electrical Code (NEC) and Canadian Electrical
Code (CEC) regarding the field repair or
modification of MI electrical heat tracing cables.
The repair of MI heat tracing cables must comply
with all national and local codes.
1.4 Heating Cable Configurations
The Field Repair Kit includes two joints and an
end cap to allow for field repair or modification of
the heating cable configurations shown in
Table 1.
TABLE 1: MI HEATING CABLE CONFIGURATION
MI cable
design
Heated
length
Cold lead
length Cold lead
length
Heated length Cold lead length
Heated
length
Cold lead
length Cold lead
length
Number of
conductors Configuration
B single conductor
(61 series)
D dual conductor
(32 & 62 series)
E dual conductor
(32 & 62 series)
A sectional view of a Design D MI heating cable is
shown in Figure 1. All of the cables include both
a heated section and one or two non-heating
cold lead sections. These sections are joined at
the hot-cold joint where the heating element is

1
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General Information
spliced into larger bus wires. A final transition
at the end of the cold lead section provides an
environmental seal and tails for the electrical
connection. At the opposite end of the cable, the
conductors of Design D cables are joined and
hermetically sealed within an end cap.
Pot
Tails
(standard length
12" (300 mm))
Bus wires Gland
connector
Hot-cold
joint
Cold leadHeating section
End
cap Heating
element
Figure 1: Sectional view of Design D MI cable
1.5 Heating Cable Identification
Each MI heating cable is supplied with an
identification tag (see Figure 2) on which the
heating cable catalog number is permanently
printed. In addition to its identification purposes,
the catalog number provides information
regarding the heating cable length, power output,
and operating voltage. Also printed on the tag
are the designer’s circuit identification number
(optional), the cable current rating, serial number
and maximum cable sheath temperature.
If the cable has been designed for a hazardous
location, the area classification is printed in the
‘Haz. Locations’ section of the tag.
®
CAT. NO. – NO. DE CAT.
DESIGN / CABLE REF. / LENGTH / WATTS / VOLTS / C.L.LENGTH / A.W.G. / TERM.
DESSIN / REF. DU CABLE / LONGUEUR / WATTS / VOLTS / C.L. LONG. / CODE C.L. / TERM.
SERIAL NO. – NO. DE SERIE
ORDINARY LOCATIONS – ORDINAIRES
TAG NO. – NO. DE L’ETIQUETTE
AMPS
THE SURFACE OF THE HEATING CABLE MAY ATTAIN A TEMPERATURE OF
LA SURFACE DE CE CABLE CHAUFFANT PEUT ATTEINDRE UNE TEMP. DE
(SEE OTHER SIDE)
(VOIR AU VERSO)
ºC
D / 32SA2200 / 35 / 200 / 120 / 7 / LS23A / X / N12
F1-107169801
5A 5B
HAZ. LOCATIONS – ENDROITS DANGEREUX
CID2 BCD
1. 7
215
HT-105-34
Figure 2: Typical MI heating cable tag (front)

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2Pre-Repair Information
2.1 General
Both single conductor and dual conductor copper
sheath and Alloy 825 sheath cables can be field
repaired or modified. The field repair kits can be
used to complete the following:
• To repair or replace a joint in the heated section
(hot-hot joint)
• To repair or replace a joint between the heated
section and the non-heating cold lead section (hot-
cold joint)
• To repair or replace the end cap for Design D
cables
Brass joints and end caps are used to repair or
modify heating cables with a copper sheath heated
section and copper sheath cold lead section and
are suitable for exposure temperatures up to 392°F
(200°C).
Stainless steel joints and end caps are used to repair
or modify heating cables with an Alloy 825 sheath
heated section and Alloy 825 sheath cold lead
section and are suitable for exposure temperatures
up to 1022°F (550°C). They are also used to repair
or modify heating cables with an Alloy 825 sheath
heated section and copper sheath cold lead section
for exposure temperatures up to 482°F (250°C).
Note: If the attempted repair cannot be done
successfully, please contact nVent for assistance.
2.2 Safety Precautions
• Safety glasses and gloves must be worn when
making field repair joints
• Take care to avoid burns when handling welding
torches and hot work pieces
• Wear a welding apron when working with welding
torches
• Follow all safety instructions supplied with the
equipment you are using
• Disconnect all power before repairing or modifying
the heating cable
CAUTION: When drying out cable, care
must be taken not to trap moisture as this could
cause the cable to burst, possibly causing injury.

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2Pre-Repair Information
2.3 Changes to the Heating Cable Length
A new tag is not required for repaired or modified
heating cables provided the total length of the
heated section of the cable is not changed by more
than 3%. Where the heated section of the cable set
is changed by more than 3%, to facilitate the repair
or where the cable is modified, then a new MI cable
tag must be ordered. In these cases, the MI Heating
Cable Field Modification Approval Request Form in
Appendix A must be filled in and reviewed by nVent
before proceeding with the repair or modification
and a permanent record of the modification must be
retained.
Caution: Shortening the length of the heated
section will decrease the resistance,
resulting in increased current draw and wattage.
Similarly, increasing the length of the heated
section will increase the resistance, resulting in
decreased current draw and wattage. Pay special
attention to the over-current protective device to
ensure that it will still conform to the
requirements of national and local codes when
such modifications are made to heating cables.
WARNING: A significant decrease in the
length of the heated section may result in a
considerable increase in wattage and cable sheath
temperature with the potential of starting a fire.
Verify the cable design before applying power.

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2Pre-Repair Information
2.4 Tools and Materials Required
TABLE 2: TOOLS AND MATERIALS
500 Vdc Megohmmeter
Small hammer
Ohmmeter (multimeter)
Needle nose pliers
Drill press and bits (see Appendix C)
Steel rule
Vernier caliper (or Micrometer)
Flat file (3/16 in thick)
Small tube cutter
Round file
Diagonal (side) cutters
Hacksaw
An oxy-acetylene torch with No. 0 welding tip or
equivalent
Flat nose pliers
Knife (to strip jacketed copper cable)
Scribe or pick
Vise grip pliers or Handvise tool
Cotton cloth or rag
Small screwdriver with flat blade
Bottle of water
Steel repair jig or equivalent and two ‘C’ clamps to
hold cable firm when welding (see Appendix H)
Engraving tool (Dremel® Model 290-01 or
equivalent)

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2Pre-Repair Information
2.5 Repair Kit Components
TABLE 3: FIELD REPAIR KIT FOR COPPER SHEATH CABLES
Item Qty Description
A1 ea 3/4 in (19 mm) brass joint (grooved)
B1 ea 1/2 in (13 mm) brass joint (grooved)
C1 ea 7/16 in (11 mm) brass end cap
(grooved)
D1 ea Brass end cap plug
E10 in A-56T flux coated silver solder (orange
color)
F1 ea 3/8 in heat shrink tubing 13.7 in (35
cm) long
G1 ea 3/4 in heat shrink tubing 6.9 in (18
cm) long
H1 ea 1/2 in heat shrink tubing 6.9 in (18
cm) long
I3 ea # 6-32 brass machine screw
J24 in Fine grit emery cloth (180 grit)
K1 ea Syringe assembly with MgO and steel
needle (vacuum sealed)
L1 ea Joint packing rod
AI
J
L
K
B
C
D
E
F
G
H
Figure 3: Kit contents for copper sheath cables

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2Pre-Repair Information
TABLE 4: FIELD REPAIR KIT FOR ALLOY 825 SHEATH
CABLES
Item Qty Description
A1 ea 3/4 in (19 mm) stainless steel joint (grooved)
B1 ea 1/2 in (13 mm) stainless steel joint (grooved)
C1 ea 7/16 in (11 mm) stainless steel end cap
(grooved)
D1 ea stainless steel end cap plug
E10 in A-56T flux coated silver solder (orange color)
F24 in Medium grit emery cloth (80 grit)
G3 ea # 6-32 brass machine screw
H1 ea Syringe assembly with MgO and steel needle
(vacuum sealed)
I1 ea Joint packing rod
A
G
I
H
B
C
D
E
F
Figure 4: Kit contents for Alloy 825 sheath cables

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2Pre-Repair Information
2.6: Cross-section of completed joints and end cap
Groove
Silver
solder
Joint Heating
cable
Heating
cable
6-32 Brass
screw
Magnesium oxide
Silver
solder
Figure 5: Completed heated-section to heated-
section joint for single conductor cable
Groove
Magnesium oxide
Heating
cable
Heating
cable Joint
Silver solder
6-32 brass screw Silver
solder
Filler hole
perpendicular
to plane of
conductors
Cross section view
Filler hole
Conductors
Figure 6: Completed heated-section to heated-
section joint for two conductor cable
Groove
Magnesium oxide
Heating
cable
Cold lead
cable Joint
Silver
solder
Silver
solder
6-32 Brass
screw
Figure 7: Completed heated-section to cold-
section joint for single conductor cable

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2Pre-Repair Information
Groove
Magnesium oxide
Cold lead
cable Joint
Silver solder Silver
solder
6-32 brass screw
Heating
cable
Filler hole
perpendicular
to plane of
conductors
Cross section view
Filler hole
Conductors
Figure 8: Completed heated-section to cold-
section joint for two conductor cable
Groove
Silver
solder Endcap
Magnesium
oxide
Plug Heating
cable
Silver
solder
Figure 9: Completed end cap

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.

3
Heating Cable Repair
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3.2 Selecting the Correct Size of Joint and/or End Cap
Use a vernier caliper or micrometer to measure the
outside diameter of the heated section and/or the
cold lead section. Select the 1/2 in (13 mm) or 3/4 in
(19 mm) stainless steel or brass joint from Table 5 or
Table 6. If the heating cable is polymer jacketed, strip
back the jacket and measure the diameter of the
bare copper cable.
TABLE 5: SELECTING JOINT SIZE FOR DESIGN B, D, OR E
ALLOY 825 SHEATH HEATING CABLES
1/2 in (13 mm) stainless steel joint
For heated-section to
heated-section joint
For heated-section to cold lead section
joint
Max. diameter
heated-section cable
Max. diameter
heated-section
cable
Max. diameter cold
lead section cable
0.325 in 0.292 in 0.325 in
3/4 in (19 mm) stainless steel joint
For heated-section to
heated-section joint
For heated-section to cold lead section
joint
Max. diameter
heated-section cable
Max. diameter
heated-section
cable
Max. diameter cold
lead section cable
0.543 in 0.480 in 0.543 in
Note: If heated section is Alloy 825 sheath
and the cold lead section is copper sheath, use
the stainless steel joint.

3
Heating Cable Repair
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TABLE 6: SELECTING JOINT SIZE FOR DESIGN B, D, OR E
COPPER SHEATH HEATING CABLE
1/2 in (13 mm) brass joint
For heated-section to
heated-section joint
For heated-section to cold lead section
joint
Max. diameter
heated-section cable
Max. diameter
heated-section
cable
Max. diameter cold
lead section cable
0.325 in 0.292 in 0.325 in
3/4 in (19 mm) brass joint
For heated-section to
heated-section joint
For heated-section to cold lead section
joint
Max. diameter
heated-section cable
Max. diameter
heated-section
cable
Max. diameter cold
lead section cable
0.543 in 0.480 in 0.543 in
The end cap supplied with the kit is suitable to
repair the majority of MI heating cables. Select
the appropriate end cap and plug from Table 7. In
those instances where the heating cable diameter
exceeds 0.300 in, contact nVent technical support
for assistance.
TABLE 7: SELECTING END CAP FOR DESIGN D CABLES
Max. diameter
of heated
section
Alloy 825
sheath cables
Copper
sheath cables
End cap Size
0.300 in Use stainless
steel end cap
and plug
Use brass end
cap and plug
7/16 in
(11 mm)

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Heating Cable Repair
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3.3 Joining Design B, D, and E Cables
The instructions following apply to both heated
section-heated section (hot-hot) joints and heated
section-cold lead section (hot-cold) joints. Read
these instructions completely before attempting
to complete the repair or modification and refer to
the Appendices for additional information where
indicated. The instructions that apply specifically to
a hot-hot or hot-cold joint are clearly identified and
must be followed.
Note: Shield work area from environmental
factors such as wind as it will cool the joint
temperature making brazing difficult and
disconnect power from the heating cable before
attempting any repairs or modifications to the
heating cable.
Ensure that the portion of the cable being worked
on can be moved away from the surface at least 6
in (15 cm) to allow access when brazing (see repair
jig in Appendix H).
Expose heated section and/or cold lead section so
that 12 in (30 cm) minimum on either side of the
joint or failure point is accessible.
If replacing an old joint, heat the bell-mouth (strain
relief fitting on heating cable end of joint) with the
torch and use pliers to separate it from the joint. Use
a hacksaw to remove old joint from cable.
Bell-
mouth
Joint
Figure 10: Remove joint

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.

3
Heating Cable Repair
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Figure 12: Check insulation resistance
Verify continuity of conductors using a multimeter or
ohmmeter.
Using a vernier caliper (or micrometer), measure
the outside diameter of the heated section and/or
cold lead section (not including polymer jacket) and
select the 1/2 in (13 mm) or 3/4 in (19 mm) joint
from Table 5 or Table 6.
Figure 13: Check cable diameter
Note: If replacing the hot-cold joint, the
diameters of both the heated section and cold lead
section must be considered when choosing the
correct size joint from Table 5 or Table 6.