Tubular Heaters

The 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.

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.