INTRODUCTION
A tubular heating element is more than a metal tube with a resistance wire inside.
Its performance depends on electrical resistance, magnesium oxide insulation, sheath material, tube diameter, compaction, active heated length, cold zones, bending geometry, terminal structure and manufacturing condition.
1. Basic Internal Structure
A typical tubular heating element includes:
- resistance wire
- high-purity magnesium oxide (MgO) insulation
- metal sheath
- terminal pins or leads
- end seal
- cold zones
- mounting or threaded fittings where required
2. Tube Diameter
Tube diameter affects:
- resistance-wire arrangement space
- MgO insulation thickness
- external surface area
- mechanical strength
- forming capability
- installation clearance
- surface watt density
3. Active Heated Length and Cold Zone
Cold zones are used near terminals or mounting points to:
- protect seals
- reduce terminal temperature
- protect lead wire
- reduce heat near flange or threaded connection
- keep heat away from temperature-sensitive equipment areas
A drawing should clearly distinguish:
- overall length
- active heated length
- cold-zone length
- bend position
- terminal length
4. Resistance, Power and Voltage
P = V² / RR = V² / PFor three-phase assemblies, the branch resistance must be calculated from the final star/delta connection and circuit arrangement.
Do not assume that the resistance measured across the complete assembly is equal to the resistance of one electrical branch.
5. Bend Radius
Possible forms:
- U-shape
- W-shape
- ring
- serpentine
- spiral
- custom geometry
Minimum bend radius depends on:
- tube diameter
- sheath material
- manufacturing condition
- internal construction
- bend location
- whether the element has been annealed or otherwise prepared for forming
Do not publish one universal bend-radius multiplier for all products unless it has been confirmed for the exact manufacturing process.
6. Terminal and Lead Design
Options may include threaded terminal pin, screw terminal, lead wire, ceramic terminal block, threaded fitting, flange mounting and custom sealing.
Review current, terminal temperature, moisture, vibration, installation space, electrical clearance and maintenance access.
7. MgO Insulation and Compaction
High-purity magnesium oxide (MgO) provides electrical insulation while conducting heat from the resistance wire to the sheath.
Important factors include:
- MgO purity
- fill uniformity
- compaction
- moisture control
- end sealing
8. Custom Replacement From Drawings or Samples
Useful data include complete dimensions, tube diameter, overall length, active heated length, cold zones, bend geometry, voltage, power, branch or element resistance if known, sheath material, terminal structure, mounting dimensions and quantity.
Related Xiangyuan Products
U-Shaped Tubular Heating Element
Stainless Steel Electric Heater Rod
Custom-Shaped Tubular Heating Element
FAQ
Can a tubular element be bent after production?
Why are cold zones needed?
Can resistance identify an unknown heater?
Can Xiangyuan manufacture from a customer drawing or sample?
Engineering Note
The formulas, examples and values in this guide are for technical explanation and preliminary engineering reference only. They do not constitute a final heater selection, guaranteed performance value or project commitment. Final design must be confirmed from the actual medium, temperature, pressure, surface watt density, material compatibility, manufacturing feasibility, applicable standards and agreed supply scope.
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