Tubular Heating Elements
Highly versatile and economical, electric 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 formed into complex formations.
Durex manufactured 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. We offer a wide selection of standard designs, or tubular heating elements can be custom designed for your requirements. Durex Industries' application and design engineering team are available to assist in specifying the proper electric tubular heater configuration.
- 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
Advantages of Using a Tubular Heating Element
In addition to its versatility, other benefits of using a tubular heating element include:
- Capable of 600V or higher in specific applications
- Can be factory pre-formed or field formed with proper tooling
- Heavy wall construction is available for high-pressure and high corrosion applications
- Diameters available from 0.26” to 0.496” to suit individual applications
- Copper, Steel or high alloy sheath materials to mitigate corrosion
- High temperature capability of 1500°F+
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 0.260", 0.315", 0.375", 0.430", 0.475" and 0.496". Other special sizes are available. Depending on the diameter, lengths can be supplied up to 335". Standard sheath materials range from copper and steel to stainless steel and Incoloy® alloys. Special sheath materials may be available based on diameter and size of the element required. 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. 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 virtually 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.
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.
- Precision intricate forming
- Operating temperature to 1500°F (800°C)
- Diameters from 0.260 to 0.475 inch
- High-temperature moisture seals
- Helium leak, electrical, and X-ray testing
Considerations when Selecting a Tubular Heating Element
When choosing which tubular heating element is right for your application, there are several factors one should consider before making a decision. Factors include:
- Electrical termination type
- Temperature control
- Voltage and wattage rating
- Installation and mounting requirements (brackets, fittings, etc.)
- Forming and bending requirements
- Operating temperature
- Corrosive environment and effects on the heater
Contact the Tubular Heating Experts at Durex Industries Today
At Durex Industries, we look forward to new designs and challenges. We have extensive experience applying tubular heating elements in challenging applications from cryogenic temperatures to over 1500F, from low or high-power densities, from benign or highly corrosive environments. Let’s get started on your next tubular heater element project today.
Tubular Heater Specifications & Options
Physical and Electrical Specs
|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)|
|Wattage Tolerance||Industry Standard +5% -10%|
|Resistance Tolerance||Industry Standard +5% -10%|
|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"|
Tubular Sheath, Temperature and Watt Density Guidelines
|Heated Medium||Process Temperature
|Sheath Material||Max. Watt Density
|Clamp on to Metal||To 500 (260)
To 1000 (540)
|Milled Groove Molds||To 500 (260)
To 1000 (540)
|Vacuum Platens||To 650 (345)
To 1000 (540)
Incoloy® or Inconel®
|Clean Potable Water||To 212 (100)
To 500 (260)
|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 &
|To 200 (95)||Incoloy®, 316SS or
|15-23 (2.3 - 3.5)|
|Oils (Depends on Type & Use)||50 - 600 (10-315)||Steel 6 - 23||(1 - 3.5)|
|Ovens, Natural Convection||To 700 (370)
To 1200 (650)
|Flowing Air @
Min. 500 fpm
|To 800 (425)
To 1000 (650)
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 K MOUNTING - Mounting bracket
Specify all required dimensions and tolerances.
TYPE F MOUNTING - Mounting flange
Specify all required dimensions and tolerances.
TYPE B MOUNTING - Threaded bulkhead fittings
|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 S1 TERMINATION - Threaded stud terminal with stacked mica.
TYPE L TERMINATION - Screw lug terminal.
|#10-32||0.375" and above||1 1/16"||7/16"|
TYPE L1 TERMINATION - Screw lug terminal 90°.
|#10-32||0.375" and above||1 1/16"||7/16"|
TYPE D TERMINATION - Quick connect. Maximum 240V
TYPE D1 TERMINATION - Quick connect 90°. Maximum 240V
TYPE W TERMINATION - Leadwire terminal assembly.
Note: If protective armor cable (hose) is required, please consult factory.
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 M SEAL OPTION - Silicone rubber over mold, max. temperature 300°F (150°F)
TYPE PA SEAL OPTION - Potted adapter
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)
Tubular Heater Construction Options
Unheated Length - The unheated length can be varied to suit application requirements. Longer unheated sections are often used to keep the termination area cool or to focus heat generation in a specific area of the part or media being heated.
Distributed Wattage - Durex tubular heaters can be tailor-made to vary the watt density along the length of the heater. This aids in temperature uniformity in-mold applications or to make up for heat losses close to the ends.
Sheath Treatment and Finish - For tubular heaters that will be field bent, please be sure to specify "full anneal" on the order. For pharmaceutical and other "clean" applications, a bright anneal finish can be supplied. Also available, depending on configuration, is sheath passivation which removes any free iron that may stain or rust the finish of the sheath.
Tubular Heater Bending Options
Tubular heating elements can be formed into 2-D and 3-D shapes to better suit application requirements. Ensure to allow for up to 10% dimensional increase due to thermal expansion and to provide adequate support to prevent heating element sagging due to high temperatures. If field bending of straight elements is necessary, contact Durex Industries for field bending guidelines prior to bending. Also, specify "full sheath anneal" to allow for field bending.
Bend Tolerances for Incoloy® and Stainless Steel Sheath Elements
|Bend Data Reference||Heater Diameter|
|Minimum Bend Radius Standard||0.437"||0.562"||0.687"||0.75"||0.812"||0.875"|
|Minimum Bend Radius w/Repressed Bend||0.375"||0.50"||0.562"||0.625"||0.687"||0.75"|
|Standard Bend Tolerances||1/8"||1/8"||1/8"||1/8"||1/8"||1/8"|
|Special Bend Tolerances||1/16"||1/16"||1/16"||1/16"||1/16"||1/16"|
|Precision Bend Tolerances w/Tooling||0.005"||0.005"||0.005"||0.005"||0.005"||0.005"|
Note: Tighter bend radii possible for steel and copper sheath elements. Please consult Durex Industries for more information.
- Tubular Heater Bend Formations - 406KB (PDF)
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.
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.
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