Tubular Heaters

 

Tubular Heaters

tubular heatersThe most versatile of all electric heating elements, the tubular heater is capable of being formed into virtually any configuration. The basic design consists of a helical coil of nickel-chromium resistance wire precisely centered in a metal sheath. This coil is surrounded by magnesium oxide powder which is vibration loaded to insure even density throughout the length of the heater. This entire assembly is then reduced to the finished diameter, compacting the MgO and “freezing” the coil in the center of the heater. The range of ratings, sizes, materials and terminations available makes the tubular heater adaptable to many industrial, commercial and scientific applications.
Copper Sheath: Water heating, water solutions non-corrosive to copper.

Steel Sheath: Immersion in oils, molten salt baths, alkaline cleaning solutions, tars and asphalt. Also suitable for clamping to metal surfaces and casting into aluminum.

Stainless Steel Sheath: Corrosive liquids, food processing equipment.

Incoloy Sheath: Air heating, radiant heating, cleaning and degreasing solutions, plating and pickling solutions, corrosive liquids.

Other sheath materials are also available for application considerations. Commonly specified are 316 stainless steel and Carpenter 20 stainless steel for corrosive immersion heating, copper clad steel for metal casting, Inconel for high temperature applications, and titanium for severely corrosive solution heating. Porcelain and ceramic coatings can also be provided for corrosive atmospheres in process air applications, immersion heating, or for other application considerations.

process electric heaters
Minimum Unheated Section On Each End:
1-1/4″ 11-1/2″ to 50″
1-1/2″ 51″ to 80″
1-5/8″ 81″ to 110″
1-3/4″ 111″ to 140″
2″ 141″ to 170″
2-1/4″ 171″ to 192″
2-1/2″ 193″ and Longer
Sheath
Material
Max. Sheath
Temperature
Max. Watts
Per. Sq. In.
Copper 350°F/175° 55
Steel 750°F/400° 22
Stainless Steel 1200°F/650° 30
Incoloy 1500°F/815° 40
Tolerances and Limitations
Sheath Diameter ±.005* .210 .250 .312 .375 .430/.437 .475/.490 .625
Minimum Sheath Length 11-1/2 11-1/2 11-1/2 11-1/2 11-1/2 11-1/2 11-1/2
Maximum Sheath Length 144 144 420 480 420 312 250
Maximum Voltage 240 250 250 480 600 600 600
Maximum Amps 12 15 30 30 40 40 40
Minimum OHMS/inch of EHL .177 .100 .060 .040 .040 .040 .050
Maximum OHMS/inch of EHL 8 17 21 21 21 21 17
Wattage +5% -10%
Resistance +10% -5%
Sheath Length ±1/2%
Effective Heated Length ±1%

* Other diameters are available including metric sizes

Forming

Tubular heaters can be formed into virtually any shape required. Minimum radius dimension for forming is equal to the diameter of the tubular being formed. Bends are repressed as required.

When ordering, specify the appropriate dimensions for the corresponding figure shown. If configuration is not shown, provide a sketch or sample. “SL” reference is Sheath Length.

Formations 1-28 are shown with Fig.1 terminals. Any terminal figure is available.

Type 1 Type 2
Type 3 Type 4
Type 5 Type 6
Type 7 Type 8
Type 9 Type 10
Type 11 Type 12
Type 13 Type 14
Type 15 Type 16
Type 17 Type 18
Type 19 Type 20
Type 21 Type 22
Type 23 Type 24
Type 25 Type 26
Type 27 Type 28

Finned Tubular Heaters

  • Fins increase heat transfer surface area allowing higher wattage in the same space requirement of non-finned units
  • Available in .312″,.375″,.430″,.475″and.625″ element diameter
  • 2 fin diameter selections
  • Continuous spiral fins of steel with rust and corrosion protection to 850°F/455°
  • Five turns per linear inch of element
  • 38, 50 and 67 watts per square inch
  • Standard terminal is Fig.1 – any terminal design available
  • Stainless steel fins and Stainless steel element available for operation to 1200°F/650°. Incoloy sheath and fins are available in some diameters for additional protection in high temperature processes

Element Diameter Standard Fin Outside Diameter Small Fin Outside Diameter
.312″
.375″
.430″
.475″
.625″
1.0312″
1.093″
1.156″
1.1875″
1.375″
.830″
.890″
.948″
.993″
1.14″

Single Ended Tubular Heaters


Single ended tubular heaters terminate at one end which can simplify wiring and installation. The end opposite the terminals is sealed by a welded disc. 12″ lead wires with fiberglass sleeving is standard. Specify longer length if required. Available in .475″ and .625″ diameter. Incoloy, stainless steel, copper and steel are standard sheath materials.

Single Ended Finned Tubular Heaters


Single ended finned tubular heaters are available in steel sheath with steel fins, and in stainless steel sheath with stainless steel fins. Simplifying wiring without bending provides advantages over standard finned tubular heaters in some applications. 4-5 continuous spiraled fins per inch are permanently furnace brazed to the sheath. Available in .475″ diameter element (1.1875″ fin diameter) and .625″ diameter element (1.375″ fin diameter).

Triangulated Cross Section Tubular Heaters

A flat or triangulated cross section for certain application considerations is available in .375″ and .475″ diameter. This shape resists sagging or other distortion of the element in applications such as high velocity air heating, heating thick liquids, radiant heating or other high element temperature processes. Between 112″ and 212″ at each end is round for the addition of bushings or other mounting devices including retaining rings. Consult us for bending, other options or see current Stock List. A flat cross section is also available.

Bushing and Locator Rings

A threaded bushing is brazed, welded or ring staked to the sheath to provide quick, rigid, liquid or air tight mounting through tank walls, oven walls, etc. Consult Big Chief for bushing specifications not shown.
  • Available in Brass, Stainless Steel or Steel
  • All bushings furnished with nickel plated washer, compressed non-asbestos gasket and jam nut
  • Hex head bushings standard
  • Specify location from end of sheath
  • Locator washers or retaining rings can also be attached to the element
  • Specify O.D., thickness and distance from end of sheath
Sheath
Dia.
Bushing
Thread Size
Hex Dim A B
.250 1/2-20 3/4 5/8 3/16
.312 1/2-20 3/4 5/8 3/16
.375 5/8-18 7/8 7/8 1/4
.430/.437 5/8-18 7/8 7/8 1/4
.475/.490 3/4-16 1 15/16 1/4
.625 7/8-14 1-1/8 1-1/8 1/4

Tubular Heaters

The following Standard Product PDF file is a list of standard length tubular heaters in various diameters and watt densities. The illustration shows Fig. 1 terminals, but any of the standard terminal figures are available. The sheath length is fully annealed for factory or field bending. The Incoloy sheath provides maximum corrosion and oxidation protection. The watt densities listed can be utilized in many air, liquid or solid heating applications and are U.L. recognized and C.S.A. certified components. CE testing and certification can be provided.

Terminal Design

Fig. 1
10-32 Cold rolled steel threaded stud. Standard terminal configuration supplied on .430/.437 and .475/.490 and .625 diameters.*
Fig. 2
8-32 Nickel plated steel welded stud. Standard terminal configuration supplied on .375, .312, .250 and .210 diameter. 10-32 Stud available.*
Fig. 3
Flag Terminal, projection welded.
Fig. 4
Flag terminal, side projection welded.
Fig. 5
Right angle Flag terminal, projection welded.
Fig. 6
Quick – connect, projection welded.

*Stainless steel terminals, other thread sizes and thread lengths available.

Fig. 7
Quick-connect, projection welded.
Fig. 8
Lead wire. (Specify length-12″ standard.)
Fig. 9
Epoxy seal: Maximum temperature at seal – 265°F/130°.** Epoxylite seal – for temperatures to 600°F/315°. Ceramic insulator would not be provided on Figures 2-7.
Fig. 10
Rubber Mold: Maximum temperature at Mold – 220°F/105°.
Sheath Diameter A B
.250 7/16 1-3/4
.312 7/16 1-3/4
.430 3/4 2-1/4
Fig. 11
Hermetic Seal: Max. temp. at seal – 1000°F/538°.
.
Heater
Dia.
A B C Thread
Size
Max.
Amps
.250 1.688 .406 .280 8-32 15
.312 1.875 .406 .350 10-32 30
.375 1.875 .406 .380 10-32 30
.430 2.125 .656 .480 1/4-28 40
.475 2.125 .656 .530 1/4-28 40

**Other materials availablen.