Tubular Heating Elements

Regarded as the most versatile of all electric heating elements, tubular heating elements offer a wide range of ratings, sheath materials and forms that can be applied to almost any temperature requirement, whether for heating of solids, liquids, or gases. The structure of the tubular heating elements allows forming in various shapes, offering the advantages of improved heat distribution, greater compactness, and simple installation in many industrial applications.

Tubular heating elements are constructed from a metal tubular sheath of material selected to suit a given application. This sheath, surrounds a helical coil of nickel-chrome resistance wire, centred and tightly compacted by an electrical insulator and heat transfer medium of magnesium oxide (MgO). This gives a resistance spiral that can be varied in heat concentration and cold length sections, protected from atmospheric corrosion and mechanical abuse. Mounting bushes, header bosses, flanges etc. can be fitted to suit all installation situations.

Common Tubular Heating Element Applications

Water Heating (Liquid Immersion)

Hot water and steam are required for numerous industrial and commercial applications. For a good percentage of these, an immersed tubular heating element is the most efficient, inexpensive and robust solution.

  • Corrosive solutions for plating baths and acid tanks
  • Fresh and salt water for aquaculture and sterilising equipment
  • Waxes and other substances which require a higher temperature to become workable.
  • Oils and like liquids which need to be heated gently.

Air Heating

In this type of process the system of heating relies on the tubular heating elements to heat the air surrounding them. The watts density is dependant on the temperature and the velocity (if any) of the air or gases passing over the element. Elements can be teamed up in banks for higher energy output.

  • High temperature sealed ovens
  • Low temperature drying / warming Ovens
  • Hot zone sealed chambers on conveyor systems
  • Incubators and other warming cabinets

Radiant Heating (Infrared)

Radiant or Infra-red heat is utilised best in open applications where sealing the area is not possible or practical. In this case, the tubular heating elements effectively heat solid masses which fall in the path of the radiant heat. For this reason it is more efficient to utilise radiant heat to heat a mass or object in an open environment.

  • Curing ovens
  • Open Conveyor systems
  • Powder Coating / Paint drying processes

Metal Heating

These elements are essentially designed to transfer energy (heat) onto or into a solid mass of metal. Tubular heating elements can be either clamped on - or better still, cemented into a machined groove. Hotco are leaders in this field and should you require advice, please don't hesitate to contact us.

  • Clamped onto solid mass for heat transfer
  • Cemented into machined grooves for direct mass heating - Hotrunner Manifolds

Bending Recommendations

Tubular elements are formed in their cold state by means of bending rollers. The connections between the terminal stud and the resistance wire must not lie on a bend. The bending diameter (Min Bend ID) should not be less than indicated in the table below 'Tubular Element Properties'.

Sheath Materials Available Tubular Element Properties ..
. Inches Millimeters Minimum Bend
Stainless Steel - 316, 321 & 304 0.250 6.35 20 mm
Incoloy - 800 & 825 0.315 8.00 20 mm
Inconel 0.420 10.67 32 mm
Titanium 0.520 13.21 35 mm

Tubular Heating Elements in Hot Runner Manifolds

Machining Data for Hotco Cemented Tubulars . ..
Nominal Rolled Diameter Bottom Radius Track Width Track Depth
6.4 3.3 6.66 8.0
7.94 4.18 8.36 10.0
10.6 5.56 11.11 13.0
13.23 6.87 13.74 16.0


Hotco Manifold Precision Bending Recommendations . ...
Diameter Kg/m Bend ID (min) Length (max).
0.250 6.35 0.16 20 3660
0.315 8.00 0.24 25 4270
0.420 10.67 0.44 30 7000
0.520 13.21 0.59 35 7000

Power Calculations

Kw = (Mass in Kg) x (Kj°C) x (Temperature Rise °C) = RESULT ÷ 3600 + LOSSES

Considerations

  • HOTCO manufactures it's standard tubular heating elements at 40W/in² = 6W/cm²
  • Manifolds operating at temperatures above 250°C should consider seeking specialist advise from HOTCO technicians
  • Aim to track the tubular as close to a central position as possible in order to avoid excessive heat losses from the outer edge of the manifold.
  • locate the temperature sensors ideally somewhere between the heat source and the colder outer zone.
  • Take into account any large masses attached to the manifold that could absorb and drag energy from the manifold.
  • To minimise potential heat losses, consider insulating the manifold where possible.
  • Ensure the terminal exit does not lie on a bend.

Hotco has an extensive range of stock tubular heating elements and also custom-make heaters to specific requirements. As always, If you need assistance in designing or selecting the right industrial heater for your application our team of technicians are available to assist.