Mineral Insulated Heating Cable
PDS MI
B
A
C
Mineral
Insulated
Heating
Cable
Description
• Constant Wattage Series
Resistance Heating
Cable Sets
Chromalox MI mineral insulated heating cables provide rugged and reliable
heat tracing for a variety of demanding applications. The alloy 825 sheath,
magnesium oxide dielectric insulation and resistance wire construction allow
the tracing of equipment up to 900°F maintenance temperatures and excellent
resistance to many corrosive environments. At lower temperatures, watt densities of up to 50 W/Ft can be designed.
• Process Temperature
Maintenance up to 900°F
• Maximum Continuous
Exposure Temperature
(Power Off) up to 1100°F
Construction
A
Metal Sheath: High nickel content Alloy 825 is used for all heating cables and
cold leads. Alloy 825 is recognized for its use in high temperature applications,
and use in many corrosive environments. This alloy has excellent resistance to
pitting, chloride-stress, acid, and alkali corrosion.
• Wattages up to 50 W/Ft.
• Corrosion Resistant,
Alloy 825 Sheath
• Factory Assembled
Cable Sets—Ready for
Installation
B
C
MgO: Highly compacted Magnesium Oxide provides insulation of the
resistance wire for voltages up to 600V. Completely sealed sheath protects the
MgO from moisture & contamination.
Resistance Wire: A large number of available resistances enables the design of
a large range of lengths and wattages.
Cold-Lead (Not shown above): Non-heating Alloy 825 sheathed MI cable
extends the leads away from the high temperature equipment. 7 ft. long is
standard.
• Fully Annealed Sheath
allows Field Bending
D
Gland Fitting (Not shown above): Every set includes one or two 1/2” NPT
fittings for connection to a junction box. The number of fittings depends on the
configuration of the cable set (i.e. single-end or double-end).
PRECISION HEAT AND CONTROL
1382 Heil Quaker Blvd • Lavergne, Tennessee 37086 • PH: 615-793-3900 • FX: 615-793-3563 • www.chromalox.com
MI - Mineral Insulated Heating Cables
Heating Cable System Design
1. Heater Design
Determine heater design to use. See page 6 for details.
2. Calculate Heat Loss
Using the Chromalox Design Guide for Heat Tracing (PJ304), calculate the heat loss of the system. To calculate the heat
loss (Watts) you will need to know pipe diameter, insulation type and thickness, minimum ambient temperature and the
pipe maintenance temperature. In addition, Chromalox® offers ChromaTrace, a heat trace design program to facilitate heat
tracing system design.
3. Determine Total Cable Length
In addition to the system piping, in-line equipment such as valves, flanges and pipe supports require additional heat tracing
to maintain the system operating temperature. See Chromalox Design Guide (PJ304) to determine the proper component
cable allowances for your system. Add the heated pipe lenth and the component cable allowance lengths to calculate the
total cable length.
Guidelines for tracing tanks and vessels are also given in the Chromalox Design Guide (PJ304)
4. Determine Available Voltage (V)
Determine what Voltage is available. At a given voltage, not every cable length and power output is available. For example,
shorter lengths may require 120V supply. Trying several voltages may result in a more efficient design.
5. Calculate Resistance per Foot (R/ft) using the
desired Watts per Foot (W/ft) and cable length (L)
8. Determine Current Draw (I)
I= V/(R/ftactual x L)
2
2
R/ftdesired = V /(W/ftdesired x L )
9. Select Heater Single or Double Conductor Length
6. Select the Proper Resistance per Foot (R/ft) Rating
Choose a cable having equal or the next lower resistance per
foot value from the Ordering Information Table
7. Calculate Actual W/Ft. and Total Wattage (WTOTAL)
The cold lead is determined by the customer or by using a standard 7 ft. Standard cold lead is #14 awg.
10. Convert Design to a Model Number.
See table on page 6.
W/ftactual = V2/(R/ftactual x L2)
WTOTAL = W/ftactual x L
Note: Some cable resistances must be modified according to the resistance curves in the Order Information Table.
Modify your resistance according to the following procedure:
2
a.
Based on the desired power output in Watts/ft, use Graph-1 to determine the Sheath Temperature Rise for the
particular cable diameter you select.
b.
Add the sheath temperature rise to the desired maintenance temperature to determine the cable resistance at
operating conditions.
c.
From Graph-2, determine the cable resistance multiplier for your application. Multiply the resistance value
given in the resistance tables by this multiplier to determine the cable resistance at operating conditions.
d.
Determine the electrical and thermal conditions. Once the cable resistance has been selected, verify the
performance of the cable you have selected from Graph-3 and 4.
• 1382 Heil Quaker Blvd. • LaVergne, TN 37086 • Ph: 1-888-996-9258 • Fax: 615-793-3563 • www.chromalox.com
Mineral Insulated Heating Cables - MI
Ordering Information
Available Resistances
Two Conductor, 3/16” Dia. O.D.
Alloy 825, 300 Volts
Cable Number
Ohms/ft
Maximum Exposure Temperature
Rating ˙F
Resistance Curve
556K
0.043
1
658K
0.0581
1
674K
0.0742
1
600
693K
0.0926
712K
0.1170
1
715K
0.1470
1
721K
0.213
3
732K
0.319
742K
0.416
752K
0.520
766K
0.660
774K
0.740
783K
0.830
810K
1.00
813K
1.30
818K
1.80
824K
2.34
830K
2.96
838K
3.70
846K
4.72
860K
5.60
866K
6.60
894K
9.00
919K
18.00
1
1100
N/A
Two Conductor, 5/16” Dia O.D.
Alloy 825, 600 Volts
Cable Number
Ohms/ft
588B
0.0071
614B
0.0149
627B
0.027
2
640B
0.040
3
670B
0.065
710B
0.104
715B
0.162
720B
0.205
732B
0.325
750B
0.500
774B
0.735
810B
1.162
819B
1.87
830B
2.97
840B
4.30
859B
5.98
Maximum Exposure Temperature
Rating ˙F
Resistance Curve
1
600
1
1100
N/A
• 1382 Heil Quaker Blvd. • LaVergne, TN 37086 • Ph: 1-888-996-9258 • Fax: 615-793-3563 • www.chromalox.com
3
MI - Mineral Insulated Heating Cables
Ordering Information
Available Resistances
One Conductor, 3/16” Dia. O.D.
Alloy 825, 600 Volts
4
Cable Number
Ohms/ft
145K
0.0046
189K
0.0090
216K
0.0165
239K
0.039
250K
0.050
279K
0.079
310K
0.095
316K
0.157
326K
0.260
333K
0.330
346K
0.457
372K
0.730
412K
1.17
415K
1.48
423K
2.36
430K
2.80
447K
4.50
Maximum Exposure Temperature
Rating ˙F
Ohms/ft
1
600
1
2
1100
N/A
• 1382 Heil Quaker Blvd. • LaVergne, TN 37086 • Ph: 1-888-996-9258 • Fax: 615-793-3563 • www.chromalox.com
Mineral Insulated Heating Cables - MI
Specification / Application Information
Graph-1
Cable Sheath Temperature Rise
Graph-2
Cable Resistance Temperature Multiplier
Sheath Temperature Rise (F˚)
Resistance Multiplier
2.5
600
550
2.25
500
2.0
450
1
400
1.75
K
350
1.5
300
B
2
250
3
1.25
200
1.0
150
100
0.75
50
0.5
0
10
20
30
40
50
60
70
80
90
0
100
100
200
300
400
500
600
700
800
900
1000
Sheath Temperature
Cable Watts/Foot
Graph-3
Maximum Wattages - All Cables
With Hot/Cold Junction Under Insulation
Graph-4
Maximum Wattages All 1100˚F Maximum Temperature
Cables With Hot/Cold Junction Under Insulation
Maximum Watts/Foot
Maximum Watts/Foot
70
100
65
90
60
80
55
50
70
45
60
40
B
35
50
B
30
40
25
K
30
20
K
15
20
10
10
5
0
0
100
200
300
400
500
Maintain Temperature (˚F)
600
700
200
400
600
800
1000
1200
Maintain Temperature (˚F)
• 1382 Heil Quaker Blvd. • LaVergne, TN 37086 • Ph: 1-888-996-9258 • Fax: 615-793-3563 • www.chromalox.com
5
MI - Mineral Insulated Heating Cables
Available Designs
Form “A” (one cold lead connection and termination w/end cap, .050” fittings)
Available in two conductor only
Heated Length
Form “E” (two cold lead connections, .050” fittings)
Available in one conductor or two conductor
Heated Length
Heated Length
Accessories
Pulling Eye For “A” form 0nly
QHT-3 High Temperature Adapter is used to heat sink the hot section transistion as it passes through the thermal
insulation when the hot to cold connection must be located outside the thermal insulation due to sheath
..................................................................temperatures over 600˚F, and cable wattage above 20 w/ft.
Optional Construction
Prefix
P
X
Suffix
EM
QT
UG
UH
PH
CH
CHB
Description
Pulling Eye for “A” form only
Oversized cold section current >25 Amps and <40 Amps
Mounting of hot-cold junction outside thermal insulation (freeze protection of
lones over 600ºF
QHT-3 High temperature adapter
UL listing tag**
UL hazardous area listing tag**
FM hazardous area listing tag**
CSA hazardous area listing tag**
CSA group B hazardous area listing tag**
**Required volts,amps, and watts with each cable order
6
• 1382 Heil Quaker Blvd. • LaVergne, TN 37086 • Ph: 1-888-996-9258 • Fax: 615-793-3563 • www.chromalox.com
Mineral Insulated Heating Cables - MI
Model Numbers
To Order Complete the Model Number by using the Matrix below. If applicable, specify hazardous location classifications.
Heater Set Design “A” or “E”
Cable Number (determined by resistance value required for needed wattage output)
Cable Heated Section Length in Feet
Cable Cold Section Length in Feet
Heater Set Total Wattage (WTOTAL)
Operating Voltage (V)
P
A
670B
150
07
1477W 120V
UG
Typical Model Number
(120V, 9.9 w/ft cable, 150 feet long, with pulling eye and UL listing tag)
• 1382 Heil Quaker Blvd. • LaVergne, TN 37086 • Ph: 1-888-996-9258 • Fax: 615-793-3563 • www.chromalox.com
7
MI - Mineral Insulated Heating Cables
MI PDS
PJ328-2
February 2003
8
• 1382 Heil Quaker Blvd. • LaVergne, TN 37086 • Ph: 1-888-996-9258 • Fax: 615-793-3563 • www.chromalox.com
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