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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.
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|
|Stainless Steel – 316, 321 & 304||0.250||6.35||20 mm|
|Incoloy – 800 & 825||0.315||8.00||20 mm|
Tubular Heating Elements in Hot Runner Manifolds
|Machining Data for Hotco Cemented Tubulars|
|Nominal Rolled Diameter||Bottom Radius||Track Width||Track Depth|
|Hotco Manifold Precision Bending Recommendations|
|Diameter||Kg/m||Bend ID (min)||Length (max)|
Kw = (Mass in Kg) x (Kj°C) x (Temperature Rise °C) = RESULT ÷ 3600 + LOSSES
- 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.