Highly versatile and economical Durex tubular heater elements are applied in virtually every conceivable type of heating application. They can be applied straight or bent into complex formations. They can be reliably applied to heat a multitude of liquids, gases, and solids. Tubular heaters are also used for radiant heating in open air or in vacuum atmospheres. They can be cast into, or clamped on to, metal to form heated parts. Durex Industries’ application and design engineering team are available to assist in specifying the proper heater configuration.
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TUBULAR HEATER SPECIFICATIONS
Physical and Electrical Specifications
|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 Maximum||404" (10,260mm)||370" (9398mm)||337" (8560mm)||329" (8356mm)||281" (7137mm)||263" (6680mm)|
|Wattage Tolerance||Industry Standard +5% - 10%||Industry Standard +5% - 10%||Industry Standard +5% - 10%||Industry Standard +5% - 10%||Industry Standard +5% - 10%||Industry Standard +5% - 10%|
|Resistance Tolerance||Industry Standard +10% -5%||Industry Standard +10% -5%||Industry Standard +10% -5%||Industry Standard +10% -5%||Industry Standard +10% -5%||
Industry Standard +10% -5%
|Overall Sheath Length||11-20"||21-50"||51-80"||81-110"||111-140"||141-170"||171-200"||201" & up|
|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"|
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.
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.
Type S1 Type S2
Threaded Stud Terminal w/Ceramic Insulator Threaded Stud Terminal w/Stacked Mica
Type L1 Type L2
Screw Lug Terminal Screw Lug terminal 90°
Type D1 Type D2
Quick Connect Maximum 240V Quick Connect 90°
Leadwire Terminal Assembly
Type R Mounting Bracket
Type K Mounting Bracket
Type F Mounting Flange
Specify all required dimensions and tolerances.
Type B Threaded Bulkhead fittings
Type M Silicone Rubber Overmold
Heating Metal Parts
Durex recommends to “press fit” the tubular 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.
Tubular elements are typically formed into ‘U’ (hairpins) or loop type formations and either placed over the tank side or secured through a hole in the side (or bottom) of the tank. 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 section of our website for other liquid heating products.
To prevent overheating or fouling the heater element, ensure the heated portion of the tubular heater is immersed in liquid at all times. For optimal results, properly match the sheath material and heater watt density to the liquid application. Refer to the chart below for general sheath material and watt density guidelines.
Heating Air & Gases
Durex tubular heaters are robust solutions for furnace and oven heating as well as forced air and gas heating applications. Refer to the Circulation and Duct Heater sections of our website for forced air and gas heating products. Tubular elements are typically formed into ‘U’ (hairpins) or one of the multiple bend formations. They are installed through wall openings and secured with lock washers, clips, threaded fittings or mounting bracket.
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.
Radiant Heating and Vacuums
Tubular heaters used for radiant heating typically use reflectors to direct heat energy toward the part being heated. However, in a vacuum, heater elements operate at much higher temperatures. Therefore, reduce watt density by 20% to 30% versus air heating conditions to ensure good heater life. Aluminum sheath as well as Inconel® sheathed heaters are typically used with vacuum feed through assemblies. Vacuum leakage rates can be measured down to 8x10-8 SCCS He (3x10-6 Pa l/s).
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