Straight & Formed Tubular Heaters

Straight and Formed Tubular HeatersIndustrial tubular heaters are highly adaptable to most applications where electrical heating is required. They can be used in their straight form or bent into various shapes. Tubular heaters can be used in free air, clamped to a surface, placed inside a groove or cast into metal. These versatile heating elements are available in Steel, Copper, Stainless Steel or Incoloy outside sheath and can be utilized in application temperatures of up to 1400º F.

Bucan tubular heaters use 80% Nickel 20% Chromium high grade coiled resistance wire as a heating core. This core is welded at both ends to pins that provide a cold section that varies in length depending on the application requirements. The coil-pin assembly is precisely centred inside a heavy gauge, oversize metal tube, and embedded inside a 96% pure, high-grade MgO insulating medium. This assembly is then compacted through a roll-reducing process that reduces the outside tube diameter to its final size, and transforms the MgO matrix into a rock-hard solid that acts as an excellent heat transferring medium, as well as an electric insulation with high dielectric strength. Finally, heaters are annealed inside a high-temperature furnace to eliminate internal stresses accumulated during the cold-forming and roll-reducing process to make them soft. Heating elements are then formed into special shapes, or supplied in their straight form. Proper electrical terminations are added to the final product.

INDUSTRIAL APPLICATIONS

  • FORMING MACHINES

  • HEATING MOLDS & PLATENS

  • IMMERSION INTO LIQUIDS

  • RADIANT & CONVECTION HEATING

  • EMBEDDED OR CAST INTO METAL

Tubular Heater Specifications Table

Tubular diameter (inches) Maximum voltage Maximum amps Minimum Ohms per heated length (inches) Maximum Ohms per heated length (inches) Minimum sheath length (inches) Maximum sheath length (inches)
0.260 240 15 0.1 17 11 240
0.315 300 30 0.06 20 11 240
0.375 600 30 0.05 20 11 240
0.430 600 40 0.05 20 11 240
0.475 600 40 0.05 20 11 240

 

 

Overall length (inches) 11-20 21-40 41-70 71-100 101-140 141-170 171-200 201+
Tolerance in sheath length (+/- in) 0.1 0.125 0.16 0.19 0.22 0.25 0.375 0.5
Tolerance in heated length (+/- in) 0.25 0.5 0.9 1.130 1.4 1.65 2 2.38
Min. unheated length (inches) 1 1.25 1.5 1.625 1.75 2.25 2.25 2.5

 

 

 

 

Mounting Accessories and Moisture Proofing for Straight and Formed Tubular Heaters

 

Termination Styles for Straight and Formed Tubular Heaters

Moisture Proofing

The MgO insulating medium inside a tubular heater is highly hygroscopic and can absorb moisture from its terminal ends. Moisture resisting seals are barriers that resist or stop moisture and contamination.

Silicone Resin

This seal is a silicone-based resin that is applied to tubular heater terminal ends. The seal penetrates a short length of the MgO insulation and transforms it into a moisture and contamination resistant medium suitable for temperatures below 200°F.

RTV Seal

This is a silicone room temperature vulcanizing seal that can resist moisture and contamination for up to 350°F.

Epoxy Seal

This is a liquid resin which is thermally cured to reach solid state. This moisture barrier is adequate for temperatures up to 400°F.

The two most critical factors that affect the durability of a tubular heater are:

â–  Sheath material

â–  Watt density

The sheath material type of a tubular heater depends on the operating temperature and the corrosivity of the medium within which the heater will operate. The watt density distribution on the surface of a tubular heater is critical for two reasons. First it determines the temperature that a heating element sheath will attain within the conditions that the heater is subjected to. The second reason is that every material has a specific maximum watt density that it can tolerate during its heating cycle. Table 1 below lists various sheath materials, maximum allowable temperatures and mediums within which they are recommended to operate. Table 2 lists recommended maximum watt densities and maximum operating temperatures for different materials. Graphs 1, 2, 3 and 4 show the relationship between the sheath temperature of a tubular heater and its watt density in different conditions.

 

Sheath Material Maximum Sheath Temperature Applications
Copper 3500 F Immersion into water and non corrosive low viscosity liquids
Steel 7500 F Oil, wax, asphalt, cast in aluminum or iron
Stainless Steel 304-316 12000F Corrosive liquids, food industry, sterilizers
Incoloy 15000 F Air, corrosive liquids, clamped to surfaces

 

 

Maximum Watt Density Ratings for Various Solutions

Solution Maximum Watts/in2 Max Operating Temperature (0 F)
Acetic acid 40 180
Chromic acid 40 180
Citric acid 23 180
Nitric acid 20-25 167
Phosphoric acid 25-28 180
Alkaline solutions 40 212
Asphalt, tar 4-10 200-500
Bunker C fuel oil 10 160
Caustic soda 2% 45 210
Caustic soda 10% 25 210
Caustic soda 75% 10 180
Ethylene glycol 30 300
Fuel oil pre-heating 9 180
Gasoline 20 300
Machine oil, SAE 30 18 250
Mineral oil 16-26 200-400
Molasses 4-5 100
Heat transfer oils 12-20 500-650
Vegetable oil 30-50 400
Degreasing solution 23 275
Hydraulic oil 12-15 100
Sodium phosphate 40 212
Trichlorethylene 23 150
Clean water 55-80 212
Deionized water 60 212
Demineralized water 60 212