Thermal measuring and testing – Temperature measurement – In spaced noncontact relationship to specimen
Patent
1995-04-12
1997-11-18
Bennett, G. Bradley
Thermal measuring and testing
Temperature measurement
In spaced noncontact relationship to specimen
374126, G01J 500
Patent
active
056880510
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with the provision of a radiation pyrometer assembly capable of accurately and quickly sensing the temperature of an elongate body moving longitudinally through a process line. Such apparatus is valuable for controlling process stages such as annealing aluminium strip prior to rolling without having any direct contact between a temperature sensor and the strip.
A problem experienced with conventional use of a radiation pyrometer for sensing the temperature of objects such as metal strip is that the radiation emitted from the surface of the strip is dependent on the emissivity of the surface. So long as the emissivity is constant accurate temperature sensing is possible, however, with materials such as aluminium strip the surface emissivity can vary unpredictably sometimes exacerbated by low radiated energy levels.
Accordingly the present invention aims to provide a radiation pyrometer assembly for sensing the temperature of an elongate body moving longitudinally comprising, having a substantially uniform emissivity and radiation pyrometer means disposed to view coated parts of the body as the body passes a temperature measurement station.
By coating parts of the body with a coating of uniform emissivity the problem of errors in radiation pyrometry temperature measurement is largely eliminated because the coating is at practically the same temperature as the body and because the emissivity of the coating is known the temperature can be accurately calculated. Preferably the coating will be black in order to provide a large radiation signal. The assembly will be used over a wide range of temperatures so that the coating must be selected to remain in intimate contact with the surface of the object even during and after passage through a furnace such as an annealing furnace.
In a preferred form of the assembly a process-control radiation pyrometer is arranged in the usual manner to view one uncoated face of the body as it passes the temperature measurement station, whilst simultaneously a second calibration radiation pyrometer views a coated face on the reverse side of the body. The reading of the second pyrometer is used to correct the reading of the first pyrometer. In the case where the elongate body is a strip of metal it is convenient to apply the coating as a stripe on the reverse side of the body.
The coating may be applied by brush painting or preferably by a spraying apparatus. The coating can be selected to be easily removed downstream of the radiation pyrometer(s) by brushing or washing.
It will be understood that in practice it is not possible to apply the paint to an extensive portion of the body since the presence of the paint, or the means used to remove it subsequently, will be detrimental to the product. Therefore the paint stripe is applied only from time to time to portions of the body which are not intended as finished product and it is assumed that between these portions the emissivity of the body, and the performance of the process control pyrometer, will not vary significantly.
BRIEF DESCRIPTION OF THE DRAWINGS
Radiation pyrometer assemblies embodying the present invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:
FIG. 1 is a diagrammatic view of the apparatus from one side,
FIG. 2 is a diagrammatic view of the apparatus from below.
FIG. 3 is a diagrammatic view of a second radiation pyrometer assembly from one side embodying the invention, and
FIG. 4 is a view of the embodiment of FIG. 3 from below.
The apparatus shown in FIGS. 1 and 2 is part of an aluminium strip thermal treatment line in which the aluminium strip 1 is heated during its passage in the direction of arrow 2 by induction heating elements 3 to a temperature sufficient to anneal the strip 1 to prepare it for rolling or other processes. As the strip 1 approaches the induction heaters 3, which are disposed one each to either side of the strip 1, the strip 1 passes through a painting means at which a spray gun 4 deposits a continuo
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King Roger Ernest
Spurge Graham Peter
Bennett G. Bradley
Davy McKee (Poole) Limited
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