Tubular Heating Elements

Highly versatile and economical Durex manufactured tubular heating elements are applied in virtually every conceivable type of heating application. These robust tubular heaters are a reliable thermal source used to heat a multitude of liquids, gases, and solids and can be applied straight or bent into complex formations.

Straight Heating Elements

Durex manufactures standard tubular heating elements for any application. Tubular heating elements are a versatile and economical heat source for a wide variety of industrial and commercial applications. Standard diameters are .260", .315", .375", .430", .475" and .496". Other special sizes are available. Depending on the diameter, lengths can be supplied up to 400". Standard sheath materials are Incoloy®, stainless steel, or copper coated steel. Special sheath materials may be available based on diameter and size of the element required. The typical electrical termination is a ceramic insulator with a threaded stud terminal. Flexible lead wire extensions or other mounting options are available for specific applications.

Formed Heating Elements

Custom heating elements can be provided to any length, formed into any configuration and sheathed in a variety of different materials to suit your application. Likewise, the connection/termination possibilities are limited only by your imagination and the availability of components. Standard terminations include a threaded stud, threaded bulkhead, screw lug, quick disconnect spade, ceramic-to-metal hermetic, molded rubber lead, conventional lead wire terminal assembly and more. Durex frequently fabricates custom tubular heaters in conjunction with an OEM's design staff, both for prototype and production.

Manifold Heating Elements

Durotube™ manifold tubular heaters provide an economical, robust, and versatile heat source. These elements are commonly used to fit into milled grooves for hot runner molding systems. The precision fit optimizes heat transfer to the working surface. Durex can provide formed elements "ready to go" into your existing channel or new tool design. Due to the fact that these designs are made to order, our engineering staff will require a detailed drawing or CAD disk for design purposes.

Tubular Immersion Heating Elements

Tubular immersion heaters are commonly used in radiant and immersion heating applications such as infant incubators where a formed tubular heating element warms the air flow and an immersion tubular heater assembly vaporizes water to provide humidity. These heater assemblies are also the preferred solution for laboratory sterilizers and environmental chambers.

Request a Quote or Contact us for assistance.


Tubular heaters are also used for radiant heating in open air or vacuum atmospheres. The heating elements can be cast into or clamped onto metal to form heated parts.  A wide selection of standard designs are available or they can be custom designed for your requirements.  Durex Industries' application and design engineering team are available to assist in specifying the proper tubular heater configuration.

DESIGN FEATURES:

  • Precision helical wound nickel-chromium resistance wire provides uniform thermal profile
  • Circumferential cold pin-to-wire fusion weld ensures robust connection for long heater life
  • Compacted, high purity MgO dielectric insulation extends resistance wire life at high temperatures
  • Recompacted bends provide longer life by ensuring insulation integrity
  • UL & CSA recognized elements assures safe and reliable performance

Tubular Heater Specifications

Physical and Electrical

Sheath Diameter +-0.005" (+-0.13mm) 0.260" (6.60mm) 0.315" (8.00mm) 0.375" (9.52mm) 0.430" (10.92mm) 0.475" (12.07mm) 0.496" (12.60mm)
Sheath Length Max. 404" (10,260mm) 370" (9398mm) 337" (8560mm) 329" (8356mm) 281" (7137mm) 263" (6680mm)
Maximum Voltage 250 480 480 600 600 600
Maximum Amperage 15 30 30 40 40 40
Wattage Tolerance Industry Standard +5% -10%
Resistance Tolerance Industry Standard +5% -10%

Length

Overall Sheath Length 11-20" 21-50" 51-80" 81-110" 111-140" 141-170" 171-200" 201"& up
Sheath Length ± 3/32" ± 1/8" ± 5/32" ± 3/16" ± 7/32" ± 1/4" ± 3/8" ± 1/2"
Heated Length ± 1/4" ± 1/2" 7/8" ± 1 1/8" ± 1 3/8" ± 1 5/8" ± 1 7/8" ± 2 3/8"
Minimum Unheated 1" 1 1/4" 1 1/2" 1 5/8" 1 3/4" 2" 2 1/4" 2 1/2"

Temperature & Watt Density Guidelines

Tubular Sheath & Watt Density

Heated Medium Process Temperature
°F (°C)
Sheath Material Max. Watt Density
W/in2 (W/cm2)
SOLIDS
Clamp on to Metal To 500 (260)
To 1000 (540)
Incoloy® 20 (3)
10 (1.5)
Milled Groove Molds To 500 (260)
To 1000 (540)
Incoloy® 60 (9)
30 (4.5)
Vacuum Platens To 650 (345)
To 1000 (540)
Aluminum, SS
Incoloy® or Inconel®
40 (6)
20 (3)
LIQUIDS
Clean Potable Water To 212 (100)
To 500 (260)
Copper
Incoloy®
60 - 90 (9 - 14)
30 - 40 (4.5 - 6)
De-I Water To 212 (100) 316SS 60 (9)
Process Water &
Very Diluted Corrosives
To 200 (95) 304SS or Incoloy® 48 (7.5)
Mild or Diluted Acids &
Alkalies
To 200 (95) Incoloy®, 316SS or
Inconel®
15-23 (2.3 - 3.5)
Oils (Depends on Type & Use) 50 - 600 (10-315) Steel 6 - 23 (1 - 3.5)
AIR
Ovens, Natural Convection To 700 (370)
To 1200 (650)
Incoloy® 30 (4.5)
10 (2.3)
Flowing Air @
Min. 500 fpm
To 800 (425)
To 1000 (650)
Incoloy® 30 (4.5)
23 (3.5)

Available Sheath Materials and Maximum Recommended Sheath Temperatures

Sheath Materials Maximum Temperature in Air °F (°C) Typical Applications
Standard Available Sheath Materials
Copper 350 (175) Clean, potable water heating
Aluminum 750 (400) Vacuum platens
Steel 750 (400) Oils, glycol, molten salts, non-corrosives
304SS 1200 (650) Improved corrosion resistance over steel
316SS 1200 (650) De-ionized water and some corrosives
Incoloy® 840 1600 (870) Improved corrosion resistance over steel and 304SS
Incoloy® 800 1600 (870) Improved resistance to chloride attack, other corrosives
Other Available Sheath Materials
321SS 1200 (650) Improved corrosion resistance over steel and 304SS
Incoloy® 825 1600 (870) Highly resistant to many acids, salts, and other media
Inconel® 600 1800 (980) Highly resistant to many acids, salts, and other media

Heater Mounting Options

TYPE R MOUNTING - Locator washers

----Type-R-Mounting.jpg

Heater Diameter A B
0.260" 3/4" Specify
0.315" 5/8" Specify
0.375" 3/4" Specify
0.430" 3/4" Specify
0.475" 3/4"
Specify

TYPE K MOUNTING - Mounting bracket

----Type-K-Mounting.jpg

Specify all required dimensions and tolerances.

TYPE F MOUNTING - Mounting flange

----Type-F-Mounting.jpg

Specify all required dimensions and tolerances.

TYPE B MOUNTING - Threaded bulkhead fittings

----Type-B-Mounting.jpg

Type Material
BB Brass
BS Steel
B4 304SS
Diameter Thread A B C
0.260" 1/2 - 20 3/4" 5/8" 3/4"
0.315" 1/2 - 20 3/4" 5/8" 3/4"
0.375" 5/8 - 18 15/16" 3/4" 7/8"
0.430" 5/8 - 18 15/16" 3/4" 7/8"
0.475" 3/4 - 20 1" 7/8" 1"

Tubular Heater Termination Options

TYPE S TERMINATION - Threaded stud terminal with a ceramic insulator.

----Type-S-Termination.jpg

TYPE S1 TERMINATION - Threaded stud terminal with stacked mica.

----Type-S-Termination.jpg

TYPE L TERMINATION - Screw lug terminal.

----Type-L-Termination.jpg

Screw Size Diameter A W
#8-32 To 0.315" 7/8" 5/16"
#10-32 0.375" and above 1 1/16" 7/16"
Maximum 240V

TYPE L1 TERMINATION - Screw lug terminal 90°.

----Type-L1-Termination.jpg

Screw Size Diameter A W
#8-32 To 0.315" 7/8" 5/16"
#10-32 0.375" and above 1 1/16" 7/16"
Maximum 240V

TYPE D TERMINATION - Quick connect. Maximum 240V

----Type-D-Termination.jpg

TYPE D1 TERMINATION - Quick connect 90°. Maximum 240V

----Type-D1-Termination.jpg

TYPE W TERMINATION - Leadwire terminal assembly.

----Type-W-Termination.jpg

Type Insulation Max. Temperature Volts
WS Silicone 390°F (200°C) 600V
WF Fiberglass 480°F (250°C) 600V
WM Mica/Glass 840°F (450°C) 600V

Note: If protective armor cable (hose) is required, please consult factory.

Seal Options

TYPE G SEAL OPTION - Silicone Conformal Coating - General protection, porous, maximum temperature 220°F (105°C)

TYPE E SEAL OPTION - Epoxy Seal - Moisture and contamination resistant (better choice for long-term moisture resistance), low porosity, maximum temperature 450°F (230°C)

TYPE V SEAL OPTION - Silicone RTV - Moisture and contamination protection, porous, max. temperature 400°F (200°C)

----Type-G-E-V_Seal-Option.jpg

TYPE M SEAL OPTION - Silicone rubber over mold, max. temperature 300°F (150°F)

----Type-M-Seal-Option.jpg

Diameter A
0.260" 7/16"
0.315" 7/16"
0.430" 5/8"

TYPE PA SEAL OPTION - Potted adapter

----Type-PA-Seal-Option.jpg

Potted protection tube ensures an integral bond between wire insulation, the seal, and protective sleeving that may be required.

Type PS is silicone RTV and silicone insulated lead wireType PP is epoxy coating and Fiberglass insulated lead wireType PT is epoxy coating and Teflon® insulated lead wire

TYPE HS SEAL OPTION - Ceramic to metal hermetic terminals, max. temperature 1000°F (540°C)

----Type-HS-Seal-Option.jpg

Thread Size Diameter W
#8-32 0.260" 1 3/4"
#10-32 0.315" 1 7/8"
#1/4-28 0.430" 2 1/8"

 


Heater Construction Options

Tubular Heater Bending Options

Typical Bend Formations

Tubular Heater Application Guidelines

Heating Metal Parts

Below are the installation methods for heating metals in order of best to least effective.

Durex Industries recommends to "press fit" the tubular heating element into milled groove plates for extended heater life. Ensure that all heated portions of the heater are in contact with the part. Heat transfer cement should be used to promote heat transfer. If clamps are used, they should be closely spaced and not over tightened to ensure good heater-to-part contact. Allow for up to 10% length increase due to thermal expansion during heating.

Heating Liquids

To prevent overheating or fouling the heating element, ensure the heated portion of the tubular heater is immersed in liquids AT ALL TIMES. For optimal results, properly match the sheath material and heater watt density to the liquid application. Factory installed fittings or field installed compression fittings are used to mount and seal the tubular element against the tank wall. Refer to the Immersion, Circulation, and Over-The-Side Heater sections of our website or catalog for other liquid heating products.

Heating Air & Gases

Tubular heating elements are typically formed into a "U" hairpin or other formation, installed through wall openings and secured with lock washers, clips, threaded fittings, mounting bracket or flange. For optimal results, use an Incoloy® sheath and ensure reasonable watt densities are used. Allow for 10% length increase due to thermal expansion. For horizontal installations, provide supports at least every 18" of length to avoid element sagging due to high temperatures. Refer to the Circulation and Duct Heater sections of the website or catalog for forced air and gas heating.

Radiant Heating and Vacuums

Tubular heaters used for radiant heating typically use reflectors to direct heat energy toward the part being heated. This works well for warming, drying, and curing applications. However, when using heaters in a vacuum, the only heat transfer is through radiation, so reduce watt density by 20% to 30% versus air heating. Aluminum sheath, as well as Inconel® sheathed heaters are typically used with vacuum feedthrough assemblies. Durex Industries can test and measure vacuum leakage rates down to 8x10-8 SCCS He (3x10-6 Pa 1/s).

 

Request a Quote or Contact us for assistance.

Back to Top

Typical Tubular Heating Element Applications

  • Metal mold, die and platen heating
  • Medical and analytical device heating
  • Cast into metal parts and platens
  • Cut and seal heads on packaging equipment
  • Tank wall and pipe heating
  • Liquid immersion & circulation heaters
  • Furnace & oven heating
  • Comfort heating and freeze protection
  • Process air and gas heating
  • Thermoforming, curing, drying

Request a Quote or Contact us for assistance.

Tubular Heaters 5-27-14 - 776KB

Request Info