Watlow WATROD Application Guide

W A T L O W

Tubular and
Process Assemblies

Elements and Assemblies

Watlow tubular elements and
assemblies are primarily used for
direct immersion in water, oils,
viscous materials, solvents, process
solutions and molten materials as
well as air and gases.

Additionally, round and flat surface
tubular elements (WATROD and
FIREBAR®heaters respectively) can
be used for surface heating.

WATROD and FIREBAR heating
elements may be purchased
separately, or fabricated into
process heating assemblies,
including:

• Screw plug

• Flange

• Circulation

• Booster

• Engine Preheater

• Over-the-Side

• Vertical Loop

• Drum

• Duct
Both elements and assemblies are

available from stock. They can be
configured with a variety of watt and
volt ratings, terminations, sheath
materials and mounting options to
satisfy the most demanding
applications.

If our stock products do not meet
your application needs, Watlow can
custom engineer the optimum
heater.

Performance Capabilities

• Sheath temperatures up to
1800°F (983°C)

• Assembly wattages to 2.2
megawatts

• Process assembly ratings up to
1000 psi (70 kg/cm2)

• Watt densities up to 120 W/in
(18.6 W/cm2)

2

Assemblies, left to right:WATROD duct,WATROD screw plug, circulation and FIREBAR flange heater.
WATROD and FIREBAR elements are in front.

• Enhanced performance beyond

Features and Benefits

• 36 standard bend formations

• FIREBAR flat surface geometry

these specifications available
from Watlow Process Systems.

enable designing the heating
element around available space
to maximize heating efficiency.

enhances heat transfer in both
immersion and air applications,
and surface heating, too.
Increased surface area per linear
inch allows heaters to run cooler
in viscous materials.

➀

Tubular Elements & Assy.

• Wattages from 95 watts to 2.2
megawatts (on individual

elements and assemblies
respectively) make tubular
heaters one of the most versatile
electric heating sources
available.

Applications

• Liquids

• Air

• Gases

• Molten materials

• Contact surface heating

• Radiant surface heating

➀ Watlow Process Systems can design
thermal systems to meet specific
performance criteria. Contact your Watlow
representative for details.

261

Tubular and
Process Assemblies

Elements and Assemblies

The following two charts will help
you select an appropriate heater
based on your application and watt
density restrictions. These charts
are application driven. The total

wattage required by your application
should be known before selecting a
specific heater type(s) from the
stock tables. If your required
wattage is not known, please

consult your Watlow representative.
Once the heater type has been

identified, turn to the appropriate
product section for information on
the element or assembly.

Element and Assembly
Selection Guide

To identify the tubular heater type
best suited to your application,
consult the Element and Assembly
Selection Guide.

In most cases Watlow recommends
using single tubular heating
elements for low kilowatt
applications.

Assemblies are better suited for
large kilowatt applications to heat
liquids, air or gases.

When selecting a heater according
to watt density, be sure to consider
the following:

• Liquid viscosity at start up and at
process temperature

• Operating temperature

• Chemical composition

Under the “Heating Method”
column in the Element and
Assembly Selection Guide locate
the method that applies to your
application to find the
recommended “Heater Type.”

After identifying the heater type(s)
suitable for your application, refer to
the Supplemental Applications Chart
for further application data. This
chart will assist you in selecting the
appropriate watt density and sheath
material for your specific
application. It also presents the
performance characteristics for both
WATROD and FIREBAR elements.

Element and Assembly Selection Guide

Application Heating Method Heater Type

Liquids:

Acids Direct immersion (circulating/non-circulating) FIREBAR, WATROD, Screw Plug, Flange, Over-the-Side,

Vertical Loop, and Pipe Insert

Caustic Soda Direct immersion (circulating/non-circulating) WATROD, Screw Plug, Square Flange, Flange,

12% Concentrate Over-the-Side, Vertical Loop, Circulation, and Pipe Insert
10% Concentrate

75% Concentrate

Degreasing Solutions Direct immersion (circulating/non-circulating) FIREBAR, WATROD, Screw Plug, Square Flange, Flange,

Over-the-Side, and Pipe Insert

Electroplating Direct immersion (circulating/non-circulating) FIREBAR, WATROD, Screw Plug, Square Flange, Flange,

Over-the-Side, Drum, Vertical Loop and Pipe Insert

Ethylene Glycol Direct immersion (circulating/non-circulating) FIREBAR, WATROD, Screw Plug, Flange, Over-the-Side,

50% Concentrate Circulation, Booster, and Engine Preheater
100% Concentrate

Oils Direct immersion (circulating/non-circulating) FIREBAR, WATROD, Screw Plug, Square Flange,

Asphalt Flange, Over-the-Side, Drum, Vertical Loop, Circulation,
Fuel Oils Booster, and Pipe Insert

Light Grades 1 & 2
Medium Grades 4 & 5

Heavy Grade 6 & Bunker C
Heat Transfer
Lubricating

SAE 10, 20, 30

SAE 40, 50

API STD 614

Vegetable (Cooking)

Paraffin or Wax Direct immersion (circulating/non-circulating) FIREBAR, WATROD, Screw Plug, Square Flange, Flange,

Over-the-Side, Drum, and Pipe Insert

CONTINUED

262

W A T L O W

Tubular and
Process Assemblies

Elements and Assemblies

Element and Assembly Selection Guide

Application Heating Method Heater Type

Water

Clean Direct immersion (circulating/non-circulating) FIREBAR (non-process water only)
Deionized WATROD, Screw Plug, Screw Plug with Control Assembly,
Demineralized Square Flange, Flange, Over-the-Side, Drum, Vertical Loop,
Potable Circulation, Booster, Engine Preheater and Pipe Insert
Process

Air: Direct (forced or natural convection) FIREBAR, WATROD, FINBAR, WATROD Enclosure Heater,

Screw Plug, Flange, Circulation, and Duct

Gas: Direct (forced) FIREBAR, WATROD, Screw Plug, Flange, and Circulation

Hydrocarbons, Nitrogen, Oxygen

Ozone, Steam

Molten Materials:

Aluminum Indirect (radiant) WATROD

Lead Direct (non-circulating) FIREBAR and WATROD

Salt Direct (non-circulating) FIREBAR and WATROD

Solder Direct (non-circulating) FIREBAR and WATROD

Surface Heating:

Dies, Griddles, Molds, Platens Direct FIREBAR and WATROD

Tubular Elements & Assy.

Supplemental Applications Chart

This Supplemental Applications
Chart is provided in addition to the
Element and Assembly Selection
Guide. This chart will help you

select watt density and sheath

materials for either WATROD or
FIREBAR heating elements
according to the specific media
being heated.

For example, if you’re heating

vegetable oil, either WATROD or
FIREBAR elements at 30 and 40
watts per square inch respectively
(4.6 and 6.2 W/cm2) with 304
stainless steel sheath can be used.

Supplemental Applications Chart

WATROD Element FIREBAR Element

Maximum Maximum Maximum
Operating Watt Watt

Heated Material Temperature Density Sheath Material Density Sheath Material

°F (°C) W/in2(W/cm2) W/in

Acid Solutions (Mild)

Acetic 180 (82) 40 (6.2) 316 Stainless Steel 40 (6.2) Incoloy®800
Boric (30% max.) 257 (125) 40 (6.2) Titanium 40 (6.2) 304 Stainless Steel
Carbonic 180 (82) 40 (6.2) Inconel®600 40 (6.2) 304 Stainless Steel
Chromic 180 (82) 40 (6.2) Titanium N/A N/A N/A
Citric 180 (82) 23 (3.6) Incoloy

Fatty Acids 150 (65) 20 (3.1) 316 Stainless Steel 30 (4.6) Incoloy®800
Lactic 122 (50) 10 (1.6) 316 Stainless Steel N/A N/A N/A
Levulinic 180 (82) 40 (6.2) Inconel®600 40 (6.2) 304 Stainless Steel
Malic 122 (50) 10 (1.6) 316 Stainless Steel 16 (2.5) Incoloy®800
Nitric (30% max.) 167 (75) 20 (3.1) 316 Stainless Steel 30 (4.6) Incoloy®800

Phenol—2-4

Disulfonic 180 (82) 40 (6.2) 316 Stainless Steel 40 (6.2) Incoloy®800

Phosphoric 180 (82) 23 (3.6) Incoloy
Phosphoric (Aerated) 180 (82) 23 (3.6) 304 Stainless Steel 30 (4.6) 304 Stainless Steel

®

®

2

(W/cm2)

30 (4.6) Incoloy®800

30 (4.6) Incoloy®800

CONTINUED

Incoloy®and Inconel®are registered trade­marks of Special Metals Corporation.

263

Tubular and
Process Assemblies

Elements and Assemblies

Supplemental Applications Chart

WATROD Element FIREBAR Element

Maximum Maximum Maximum
Operating Watt Watt

Heated Material Temperature Density Sheath Material Density Sheath Material

°F (°C) W/in2(W/cm2) W/in

Proponic (10% max.) 180 (82) 40 (6.2) Copper 40 (6.2) 304 Stainless Steel
Tannic 167/180 (75/82) 23/40 (3.6/6.2) Steel/304 S.Steel 40 (6.2) 304 Stainless Steel

Tartaric 180 (82) 40 (6.2) 316 Stainless Steel 40 (6.2) Incoloy®800

Acetaldehyde 180 (82) 10 (1.6) Copper 16 (2.4) Incoloy®800
Acetone 130 (54) 10 (1.6) 304 Stainless Steel 16 (2.4) 304 Stainless Steel
Air ➀➀➀➀Incoloy

®

Alcyl Alcohol 200 (93) 10 (1.6) Copper 16 (2.4) Incoloy®800
Alkaline Solutions 212 (100) 40 (6.2) Steel 48 (7.4) 304 Stainless Steel

Aluminum Acetate 122 (50) 10 (1.6) 316 Stainless Steel 16 (2.5) Incoloy
Aluminum Potassium

Sulfate 212 (100) 40 (6.2) Copper N/A N/A N/A
Ammonia Gas ➀➀➀➀Steel ➀➀304 Stainless Steel
Ammonium Acetate 167 (75) 23 (3.6) Incoloy

Amyl Acetate 240 (115) 23 (3.6) Incoloy

®
®

Amyl Alcohol 212 (100) 20 (3.1) 304 Stainless Steel 30 (4.6) 304 Stainless Steel
Aniline 350 (176) 23 (3.6) 304 Stainless Steel 30 (4.6) 304 Stainless Steel
Asphalt 200-500 (93-260) 4-10 (0.6 - 1.6) Steel 6-12 (0.9 - 1.8) 304 Stainless Steel
Barium Hydroxide 212 (100) 40 (6.2) 316 Stainless Steel 40 (6.2) Incoloy®800

Benzene, liquid 150 (65) 10 (1.6) Copper 16 (2.5) 304 Stainless Steel
Butyl Acetate 225 (107) 10 (1.6) 316 Stainless Steel 16 (2.5) Incoloy®800
Calcium Bisulfate 400 (204) 20 (3.1) 316 Stainless Steel N/A N/A N/A
Calcium Chloride 200 (93) 5-8 (0.8 - 1.2) Inconel®600 N/A N/A N/A
Carbon Monoxide — — ➀➀ Incoloy

Carbon Tetrachloride 160 (71) 23 (3.6) Incoloy

®
®

Caustic Soda:

2% 210 (98) 48 (7.4) Incoloy

10% Concentrate 210 (98) 23 (3.6) Incoloy

75% 180 (82) 23 (3.6) Incoloy
Citric Juices 185 (85) 23 (3.6) Incoloy

®
®
®

®

Degreasing Solution 275 (135) 23 (3.6) Steel 30 (4.6) 304 Stainless Steel
Dextrose 212 (100) 20 (3.1) 304 Stainless Steel 30 (4.6) 304 Stainless Steel

Dyes & Pigments 212 (100) 23 (3.6) 304 Stainless Steel 30 (4.6) 304 Stainless Steel

Electroplating Baths:

Cadmium 180 (82) 40 (6.2) 304 Stainless Steel 40 (6.2) 304 Stainless Steel

Copper 180 (82) 40 (6.2) 316 Stainless Steel N/A N/A N/A

Dilute Cyanide 180 (82) 40 (6.2) 316 Stainless Steel N/A N/A N/A

Rochelle Cyanide 180 (82) 40 (6.2) 316 Stainless Steel N/A N/A N/A

Sodium Cyanide 180 (82) 40 (6.2) 316 Stainless Steel N/A N/A N/A

Potassium Cyanide 180 (82) 40 (6.2) 316 Stainless Steel 40 (6.2) 304 Stainless Steel
Ethylene Glycol 300 (148) 30 (4.6) Steel 40 (6.2) 304 Stainless Steel

Formaldehyde 180 (82) 10 (1.6) 304 Stainless Steel 16 (2.5) 304 Stainless Steel

®

Gas 300 (148) 2-5 (0.3 - 0.8) Steel ➀➀304 Stainless Steel

Freon
Gasoline 300 (148) 23 (3.6) Steel 30 (4.6) 304 Stainless Steel

2

(W/cm2)

➀➀Incoloy®800

®

800

30 (4.6) Incoloy®800
30 (4.6) Incoloy®800

➀➀Incoloy

30 (4.6) Incoloy

®
®

— — Consult factory
— — Consult factory
— — Consult factory

30 (4.6) Incoloy

®

CONTINUED

➀ Consult your Watlow representative.
Freon®is a registered trademark of
E.I. du Pont de Nemours and Company.

264