Watlow MI Band Specifications
Band/Barrel Heaters
Max. Operating Typical Max.
Temperatures Watt Densities
Band/Barrel Heaters Sheath Materials °F °C W/in2 W/cm
Mineral Insulated (MI) Stainless steel 1400 760 100 15.5 493
2
Page
Band/Barrel Heaters
WATLOW
®
491
492
WATLOW
®
Band/Barrel Heaters
Mineral Insulated (MI) Band Heaters
The mineral insulated (MI) band heater from Watlow® is
a high-performance heater that incorporates Watlow’s
exclusive mineral insulation. This material offers much
higher thermal conductivity than mica and hard ceramic
insulators that are used in conventional heaters.
A thin layer of the “high” thermally conductive MI material
electrically insulates the element wire from the inside
diameter of the heater sheath. A thicker, low thermally
conductivity layer backs up the element wire directing the
heat inward toward the part being heated. The result is
more efficient heat transfer, which lowers element wire
temperatures and increases heater life.
Performance Capabilities
• Heater operating temperatures up to 1400°F (760°C)
• Watt densities up to 100 W/in
on large diameter barrel bands
• Maximum voltage to 480V
2
(15.5 W/cm2) available
Features and Benefits
High thermal conductivity of MI and low mass
construction
• Provides an almost instant response to temperature
control
• Eliminates thermal lag and temperature overshoot
associated with ceramic insulated heaters
Operating temperatures up to 1400°F (760°C)
• Allows safe melting of resins such as PEEK™,
Teflon®, Ultem® and Zytel®
Higher watt densities
• Contributes to faster heat-up and throughput for
increased productivity
Stainless steel cover and side fold design
• Resists contamination from overflow of plastic or other
free-flowing materials
Attached clamp bars
• Eliminates cumbersome clamping straps to ease
installation
Typical Applications
• Extruders
• Blown film dies
• Injection molding machines
• Other cylinder heating applications
Thick Low
Conductivity
MI Backing
Thin High
Conductivity
MI Insulation
430 Stainless
Steel Sheath
Element Wire in
Mineral Insulation
Coiled or Sinuated
Wire Element
WATLOW
®
493
Band/Barrel Heaters
Mineral Insulated (MI) Band Heaters
Applications and Technical Data
The Physical Limitations of Variations table shows the
availability of widths, inside diameters and terminations
If the application requires a heater exceeding limitations
shown, contact your Watlow representative.
for Watlow’s MI band, barrel and nozzle heaters. To
ensure available terminations meet application needs,
refer to the termination variation illustrations in this
section.
Physical Limitations of Variations
I.D. Available—in. (mm)
1 pc. Construction Expandable 2 pc. Construction
Width Min. Max. Min. Max. Min. Max.
in. (mm) in. (mm) in. (mm) in. (mm) in. (mm) in. (mm) in. (mm) Available Terminations
1 (25) 1 (25) – 6 (152) 3 (76) – 12 (305) 3 (76) – 12 (305) All
3
1
/8 (35) 1 (25) – 3 (76) 3 (76) – 6 (152) 3 (76) – 6 (152) All - Except SLE
1
1
/2 (38) 1 (25) – 14 (356) 3 (76) – 14 (356) 3 (76) – 28 (711) All
2 (51) 1
1
2
/2 (64) 11/4 (32) – 14 (356) 3 (76) – 14 (356) 3 (76) – 28 (711) All
3 (76) 1
1
3
/2 (89) 13/4 (45) – 14 (356) 3 (76) – 14 (356) 3 (76) – 28 (711) All - Except 90° “B” Leads
4 (102) 2 (51) – 14 (356) 3 (76) – 14 (356) 3 (76) – 28 (711) All
1
4
/2 (114) 21/4 (57) – 14 (356) 3 (76) – 14 (356) 3 (76) – 28 (711) All
5 (127) 2
1
5
/2 (140) 23/4 (70) – 14 (356) 3 (76) – 14 (356) 4 (102) – 28 (711) Post Terminals, SLE only
6 (152) 3 (76) – 14 (356) 3 (76) – 14 (356) 4 (102) – 28 (711) All
7 (178) 4 (102) – 14 (356) Post Terminals, SLE only
1
/4 (32) – 14 (356) 3 (76) – 14 (356) 3 (76) – 28 (711) All
1
/2 (38) – 14 (356) 3 (76) – 14 (356) 3 (76) – 28 (711) All
1
/2 (64) – 14 (356) 3 (76) – 14 (356) 4 (102) – 28 (711) All - Except 90° “B” Leads
General Limitations
• Maximum width of 1 in. (25 mm) diameter heater:
11/2 in. (38 mm)
• Maximum heater width: 2x heater diameter
• Minimum I.D. for Type B, C, E and H leads:
1 in. (25 mm)
• Minimum I.D. for Type B—90° leads: 1
• Maximum lead amperes: 12.5A per pair
• SLE maximum: 17.0A
• Maximum amperes (post terminals): 30A per pair
• Minimum diameter and width for SLE: 4 in. x 1
(102 mm x 38 mm) width
• 90° leads not available over 250VAC
• Minimum I.D. for post terminals: 1
• Actual width for 7 in. (178 mm) wide heater:
7
6
/8 in. (175 mm)
1
/8 in. (29 mm)
1
/4 in. (32 mm)
1
/2 in.
Gaps
• ≤ 3 in. = 1/8 in. nomin al
• 3 in.
≤ 6 in. =
• 6 in.
≤14 in. =
• >14 in. =
1
/4 in. nominal ±1/8 in.
3
/8 in. nominal ±1/8 in.
1
/2 in. nominal ±1/4 in.
494
WATLOW
®
Band/Barrel Heaters
03
Mineral Insulated (MI) Band Heaters
Applications and Technical Data (Continued)
Calculating Watt Density
Watt density is the amount of wattage per square inch of
heated area. To determine watt density, divide the total
wattage by the heated area.
Watt Density =
Total Watts
Heated Area
To apply this equation, the term “heated area” must be
defined. Heated area is the total contact surface of the
heater less the areas of no-heat found around terminals,
mounting holes, etc.
Heated Area = Total Contact Area - No-Heat Area
Maximum Allowable Watt Density
The following derating factors apply to the Maximum
Allowable Watt Density chart, which are displayed in both
inches and millimeters. Review these factors and the
chart to determine the correct watt density curve for
the application.
Derating Factors:
• For units over 2 in. (51 mm) in width, multiply the watt
density by 0.80.
To calculate the heated area:
1. Locate the no-heat factor from the chart below that
corresponds to the type of heater being considered.
Type No-Heat Factor
in.
1 pc. lead unit Type B, C, H, E
or 90°B
1 pc. post terminal 1.60
1 pc. expandable post term 3.18
1 pc. expandable lead unit 3.00
True 2 pc. post term 3.20
True 2 pc. leads 2.74
SLE 3.68
1.37
2. To use the formula below, insert the no-heat factors,
diameter and width (in inches).
Heated Area =
(3.14 x Diameter - No-Heat Factor) x Width
• For applications where unusual operating conditions
are present, such as irregular mounting surfaces,
contact your Watlow representative for watt density
limitations.
• For two-piece units used in vertical applications, refer
to Clamping Matrix Application Guide on page 496.
• For applications where insulating blankets are used,
multiply watt density by 0.75.
1300
1200
1100
1000
900
800
700
600
500
Part Temperature — °F
400
300
200
WATLOW
Maximum Allowable Watt Density
Watt Density - W/cm
5101520253
6 in. (152 mm) I.D.
1
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230
®
10 in. (254 mm) I.D.
4
i
n
.
(
3
5
6
m
m
)
I
.
D
.
&
2
P
i
e
c
e
3 in. (76 mm) I.D.
1
2
i
n
.
(
3
0
5
m
m
)
I
.
D
.
Watt Density — W/in
2
Allowable watt density for 11⁄2 in. (38 mm) wide
MI band heaters:
• Moderate cycling
• Heaters properly clamped
• Heaters mounted on a smooth cylinder
1
1
/
2
in. (38 mm) I.D.
2
5
700
600
500
400
300
200
100
Part Temperature — °C
495
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