Watlow flange heaters are easy to
install and maintain. Designed for
heating liquids and gases in tanks
and pressure vessels, flange
immersion heaters are ideal for
applications requiring higher
kilowatts.
Watlow flange heaters are made
with WATROD or FIREBAR®tubular
elements brazed or welded to a
flange. Stock flange heaters are
equipped with a general purpose
(NEMA 1) terminal enclosure.
Flange heaters, with FIREBAR
elements, also answer the need for
liquid immersion applications
requiring high kilowatts in small
tanks. The FIREBAR element’s
unique flat surface geometry packs
more power in a smaller bundle,
with lower watt density, making it
especially well suited for petroleumbased liquid heating applications.
Performance Capabilities
• Watt densities to 100 W/in
(15.5 W/cm2)
• Wattages to one megawatt
®
•UL
and CSA component
recognition to 480VÅ(ac) and
600VÅ(ac) respectively
• Incoloy®sheath temperatures to
1600°F (870°C)
• Passivated 316 stainless steel
sheath temperatures to 1200°F
(650°C)
• 304 stainless steel sheath
temperatures to 1200°F (650°C)
• Steel sheath temperatures to
750°F (400°C)
• Copper sheath temperatures to
350°F (175°C)
2
Features and Benefits
• ANSI and ANSI compatible 2,
21⁄2
inch flanges provide appropriate
heater size-to-application and fit.
• Flange sizes up to 24 inches
available on made-to-order units.
• Element sheath and flange materials to meet application
needs.
• Integral thermowells provide
convenient temperature sensor
insertion and replacement without
draining the fluid being heated.
• A standard, general purpose
(NEMA 1) terminal enclosure
offers easy access to wiring.
• Element support(s) provide
proper element spacing to
maximizing heater performance
and life.
Conduit Opening
, 3, 4, 5, 6, 8, 10, 12 and 14
On stock chart units:
• Three to five working days on most heaters
• 10 working days on special voltages and/or
wattages
• 15 working days on special element lengths
Flange
Terminal Enclosure
Thermowell
FIREBAR
Heating Element
WATROD Heating Element
• To facilitate lifting, drilled and
tapped holes come supplied for
eye bolts on 10 inch and larger
flange heaters.
• All units are inspected and/or
tested to ensure element-toflange pressure seals do not leak.
• Four or six inch FIREBAR
flange heaters pack more
kilowatts in smaller bundles—in
liquid immersion applications, a
conventional 10 inch round
tubular element flange can be
replaced with a six inch FIREBAR
flange.
• WATROD hairpins are
repressed (recompacted) to
maintain MgO density, dielectric
strength, heat transfer and life.
• Branch circuits meet NEC with
48 amps per circuit maximum.
®
• UL
and CSA component
recognition under file numbers
E52951 and 31388 respectively.
See pages 268-271 for details.
Flange Heaters
Incoloy®is a registered trademark of
Special Metals Corporation.
UL®is a registered trademark of
Underwriter's Laboratories.
339
Tubular and
Stand-off
Terminal
Enclosure
Ref. 6"
(150 mm)
Stand-off
Height
ANSI
Flange
Conduit
Openings
Process Assemblies
Flange Immersion Heaters
Applications
• Water:
Deionized
Demineralized
Clean
Potable
Process
Options
Terminal Enclosures
General purpose terminal
enclosures, without thermostats, are
standard on all flange immersion
heaters. Optional terminal
enclosures include:
• General purpose (NEMA 1) with a
single or double pole thermostat.
• Moisture resistant (NEMA 4–
steel). Available with or without a
single or double pole thermostat.
• Corrosion resistant (NEMA 4X).
Available with or without a single
or double pole thermostat.
• Explosion resistant (NEMA 7)
class 1 groups C and D.
Available with or without a single
or double pole thermostat.
• Industrial water rinse tanks
• Vapor degreasers
• Hydraulic oil, crude, asphalt
• Lubricating oils at API specified
watt densities
• Air and gas flow
• Caustic solutions
• Explosion/moisture resistant
(NEMA 7/4) combinations.
Available with or without a single
or double pole thermostat.
• For class 1, group B enclosures,
consult your Watlow
representative.
Enclosure Enhancements
• Enclosure heater to solve
condensation and freeze
problems.
• Power distribution blocks to
facilitate power feed line wiring.
Prior to ordering, refer to the
terminal enclosure dimensions on
page 341. Order by adding the
appropriate suffix letter(s) to the
base flange heater code number, as
• Chemical baths
• Process air equipment
• Boiler equipment
• Freeze protection of any fluid
• Anti-freeze (glycol) solutions
• Paraffin
shown on the Build-a-Code chart.
Heater code numbers and suffix
letters are depicted on the Stock
and Options charts, pages 345 to
362. Specify class and group, if
applicable.
Caution
Explosion-resistant terminal
enclosures are intended to provide
explosion containment in the
electrical termination/wiring
enclosure only. No portion of the
assembly outside of this enclosure
is covered under this NEMA rating.
NEMA rating effectiveness may be
compromised by abuse or
misapplication.
Stand-off Terminal Enclosures
Stand-off terminal enclosures
provide an air-insulating barrier
between the flange and terminal
enclosure by mounting the
terminations and wiring away from
the flange. Stand-off terminal
enclosures are recommended
CSA Certified Enclosures
CSA certified moisture and/or
explosion resistant terminal
enclosures protect wiring in
hazardous gas environments.
These terminal enclosures, covered
under CSA file number 61707, are
340
whenever a process operating
temperature exceeds 400°F
(205°C). This helps minimize
terminal enclosure temperatures.
To order, specify stand-off terminalenclosure.
available on all WATROD and
FIREBAR flange heaters. For
additional information, consult your
Watlow representative.
To order, specify CSA certifiedenclosure, process temperature
(°F), maximum working pressure of
application (psig), media being
heated and heater mountingorientation (horizontal or vertical)
and flange size.
ASTM Type J or K thermocouples
offer more accurate sensing of
process and/or sheath temperatures. A thermocouple may be
inserted into the thermowell or
attached to the heater’s sheath.
Thermocouples are supplied with
120 inch (3050 mm) leads (longer
lead lengths available). Unless
otherwise specified, thermocouples
are supplied with temperature
ranges detailed on the
Thermocouple Types chart.
Using a thermocouple requires an
appropriate temperature and power
control. These must be purchased
separately. Watlow offers a wide
variety of temperature and power
controls to meet virtually all
applications. Temperature controls
can be configured to accept
process variable inputs, too.
Thermostats
To provide process temperature
control, Watlow offers optional
single pole, single throw (SPST) and
double pole, single throw (DPST)
thermostats.
Unless otherwise specified,
Consult your Watlow representative
for details.
To order, specify Type J or K
thermocouple and lead length.
Indicate if the thermocouple is for
process temperature sensing or
heater sheath high-limit protection.
Please specify if the flange heater
will be mounted vertical or horizon-
tal in the tank. If vertical, specify if
the housing is on top or bottom.
thermostats are mounted inside the
terminal enclosure. For details
and ordering information, refer to
Thermostats on pages 423 to 425.
Please verify that the thermostat’s
sensing bulb O.D. is compatible with
the flange heater’s thermowell I.D.
If the flange heater is part of an
in-line circulation heating
application, indicate flow direction
relative to the heater’s enclosure.
RTDs
If your process requires greater
temperature sensing accuracy than
is possible with thermocouples,
Watlow can also supply RTDs in DIN
or JIS calibrations. Consult Watlow
for details.
Thermocouple Types
Recommended
ASTMConductor CharacteristicsTemperature Range
TypePositive Negative°F (°C)
JIronConstantan0 to 1000(-20 to 540)
(Magnetic)(Non-magnetic)
KChromel
(Non-magnetic)(Magnetic)
➀
Type J and Type K thermocouples are rated 32 to 1382°F and 32 to 2282°F (0-750°C and
0-1250°C), respectively. Watlow does not recommend exceeding temperature ranges
shown on this chart for the tubular product line.
®
Alumel
®
0 to 2000(-20 to 1100)
➀
Wattages and Voltages
Watlow routinely supplies flange
immersion heaters with 240 to
480VÅ(ac) as well as wattages from
150 watts to one megawatt. If
®
and Chromel®are registered trademarks
Alumel
of the Hoskins Manufacturing Company.
342
required, Watlow will make heaters
with voltage up to 600VÅ(ac) and
wattage beyond one megawatt. For
more information on special voltage
Branch Circuits
Branch circuits are subdivided by
National Electrical Code (NEC)
requirements to a maximum of
and wattage configurations, consult
your Watlow representative.
48 amps per circuit. Consult factory
for circuit requirements other than
those listed in the stock charts.
W A T L O W
Direction of Flow
Tubular and
Process Assemblies
Flange Immersion Heaters
Options
Sheath Materials
The following sheath materials are
available on WATROD and FIREBAR
flange heaters:
External Finishing
Passivation
During the manufacturing process,
particles of iron or tool steel may
become embedded in the stainless
steel or alloy sheath. If not removed,
these particles may
Standard Sheath Materials
WATRODIncoloy
FIREBARIncoloy
corrode, produce rust spots and/or
contaminate the process. For
critical sheath applications,
passivation will remove free iron
from the sheath. To order, specify
passivation.
®
316 stainless steel
Steel
Copper
®
Made-to-Order Sheath Materials
WATROD304 stainless steel
FIREBAR304 stainless steel
Monel
®
Exotic Sheath Materials
Consult your Watlow representative
for details and availability.
Other Finishes
Simple belt polishing and glass
beading are available to meet
cosmetic demands. Consult factory
for details.
Flange Heaters
Flanges
Flange Sizes and Styles
Standard: 2➀, 21⁄2➀, 3, 4, 5, 6, 8, 10,
12 and 14 inch ANSI raised
face/blind flanges.
Made-to-Order: 16, 18, 20 and 24
inch in any recognized
configuration, as well as customer
specified. Over 24 inch, consult
Watlow Process Systems.
Gaskets
Rubber, asbestos-free and spiral
wound gaskets are available for all
flange sizes. Order by specifying
gasket type, flange size/rating,
process operating temperature and
pressure.
To make the correct selection, see
the Gasket Selection chart.
Baffles
For forced circulation applications,
baffles can be arranged on the
heating element bundle to enhance
and/or modify fluid or gas flow for
better heat transfer.
Flange Materials
StandardCarbon steel
316 stainless steel
304 stainless steel
Made-to-OrderExotic materials to
meet specific
application needs➁
It provides a recommended gasket
type and effective temperature
rating.
To use this chart, multiply operating
temperature by the operating
pressure to arrive at “Maximum
PSIG X °F.” This is listed in the
chart’s first column.
For open tank or convection heating
applications, standard element
supports will be supplied.
To order, specify baffles.
Pressure Classes
Standard150 lb
Made-to-Order300 lb
600 lb
Over 600 lb
➁
Gasket Selection
MaximumTemperature
PSIG X °F°FGasket Type
Up to 15,000300Rubber
Over 250,000700Asbestos-Free
Over 250,000➂Spiral Wound
➂ Depends on metal gasket material.
Gasket
➀ ANSI compatible only.
➁ Consult Watlow Process Systems in
Troy, Missouri.
®
is a registered trademark of
Monel
Special Metals Corporation.
343
Tubular and
C
D
E
F
A
No-Heat Section
K
B
Immersed Length ± 1%
H
Bundle
150 lb Flange
Conduit Opening
WATROD Element
Thermowell for 0.375"
(10 mm) Diameter Bulb
No-Heat
Section
Process Assemblies
Flange Immersion Heaters
Application Hints
• Select the recommended heating
element sheath material and watt
density for the substance being
heated. Use the SupplementalApplications Chart on pages
263 to 266. If unable to
determine the correct heating
element sheath material and type,
consult your Watlow
representative.
• Extend the element no-heat
section completely into the fluid
being heated to help prevent
premature heater failure. See
accompanying illustration for
proper no-heat section
placement.
• Locate flange heater low in the
tank, but above the sludge level.
• Choose a FIREBAR element when
your application requires a
smaller system package or lower
watt density.
• Ensure wiring integrity by keeping
terminal enclosure temperature
below 400°F (205°C).
• Keep electrical connections
clean, dry and tight.
• Minimize problems associated
with low liquid level conditions by
using low liquid level sensor or
sheath temperature high-limit
control.
• Periodically remove the flange
assembly to inspect and clean
the heating element(s). This
preventive maintenance will
reduce premature failure and
optimize heater performance.
• Refer to the Installation andMaintenance Instructions for
correct orientation of FIREBAR
elements. This is important in air
applications with customer
supplied circulation tanks.
Correct element orientation to
flow minimizes pressure drop,
increases buoyancy force and
heater performance.
Flange Immersion Heater
➁
➀
For terminal enclosure
dimensions (K and E) see
page 341.
Flange Immersion Heater Dimensions
Flange
ElementFlange
TypeSizeSiz eNumberLengthA DimensionC DimensionD DimensionF Dimension H DimensionElements
➀ Thermowells are not provided on two and 21⁄2 inch units. 150 lb rating is not available on two and 21⁄2 inch stock units.Note: The number and size of conduit openings will comply with the National Electrical Code standards.