Aluminum Billet-Test Case
The Customer is Interested in measuring the temperature of an aluminum billet; the requested Range is too large, and it is impossible to Cover With one Pyrometer, Which can Follow After Surface Variations.
For Providing This Function (Main Condition of Accurate Measurements), We Need 2 Pyrometers Working on Multiwavelength Technology.
For the Lowest Temperatures- the recommended model is A5-EX.
For Black Body- T minimum =105˚C, But for Billets (Especially Bright Reflective Billet’s Cut) T minimum ≥160˚C and the maximum, temperature will be T maximum =550˚C
From -15˚C to 150-200˚C, There are Only Very Long Wavelength Pyrometers in the Spectral Range of 8-14mkm. This type of pyrometer is sensitive and Usually Not Intended for Metal Surface Measurements – It has a Very Big Dependency on Surface Emissivity:
It Means That for the Same Billet, it Temperature Possible to Get a Very Different Pyrometer Readouts When the Surface is Dark or Bright; clean or Dirty.
If the customer intends to continuously monitor the billet face temperature (see below the sketch), We recommend locating the pyrometer at a distance of 3500mm from the furnace; thus, it will keep a safe distance from any billet up to a billet length of 2800mm. Please note that the pyrometer’s optics defocusing will produce measurement spots with lightly different diameters for different distances.
Customers must consider the influence of radial temperature distribution on the average pyrometer readout for different diameters.
(we are not experts in this issue, maybe the gradient is slight; thus, they shouldn’t be worried about these spot variations.)
The common practice is measuring the billet skin temperature control on the furnace exit. The pyrometer aims perpendicular to the billet, getting continuous readings along a billet from the furnace.
In this case, the extruder gets information about the heating level for furnace setup correction and billet tapering in case the furnace works with gradient heating.
