Product category:
Metals processing plant and equipment
News Release from: Motor Technology | Subject: Lenord + Bauer's Sensorline GEL 235 encoder
Edited by the Manufacturingtalk Editorial
Team on 06 August 2007
Encoder measures blast furnace plug
rotation
Not many encoders can survive the environment near the base of a blast furnace, but the sensing principle and the vernier disc of an 'ultra tough' encoder works on taphole plugging..
An encoder has to measure the angle of rotation of the plugging machine at the bottom of a blast furnace where hot pig iron emerges at around 1,600 deg C Several times a day plugging machines open tapholes in the blast furnace at the Krupp Mannesmann (HKM) steelworks in Duisburg, Germany, to discharge the hot metal ready for the next stage of its processing
This article was originally published on Manufacturingtalk on 16 Jul 2008 at 8.00am (UK)
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To seal the hole, the taphole gun rotates about its attachment point to drive its stopper head to seal the previously drilled taphole with rapidly hardening plug material.
On no account may the plugging machine apply pressure to the furnace breast.
It has to travel precisely to its end position at the taphole in order to position the plug.
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The Lenord + Bauer's Sensorline GEL 235 encoder's exact measurement of the rotational angle enables the movement to come to a halt at precisely the right moment.
The Sensorline GEL 235 has been successfully used on blast furnaces and has provided reliability and longevity on an application where frequent failure was common, said Motor Technology, UK agent for Lenord + Bauer.
Krupp Mannesmann (HKM) steelworks produce 5.2 million tonnes of pig iron a year.
The reliable operation of machinery and equipment is essential and the plugging machines are the most critical parts of the entire plant.
Motor Technology said that encoders previously performing this function have suffered frequent failures because of the extreme, fluctuating temperatures in the vicinity of the plugging machines.
Optical sensors in particular regularly refused to function as a result of temperature-related material tensions between the steel encoder shaft and the optically transparent plastics or glass code discs.
Absolute rotary encoders in elaborate protective housings also failed to deliver the required reliability and the temperature cycles of the environment accelerated the aging of the always susceptible LED sources.
The rugged nature of the new GEL 235 is based on a contour disk made of ferromagnetic steel.
Optical lithography and chemical etching processes are used to etch three incremental tracks with stepped numbers of ridges into the steel disc.
The tracks are scanned magnetically using giant magneto-resistive sensor elements and the absolute position is determined by ingeniously applying a Vernier scale to the readings.
By these means, the GEL 235 encoder is accurate to 0.1deg and has an overall resolution of 28 bits (16 bit single turn and 12 bit multi-turn).
Its use of a magnetic measuring principle means that the new GEL 235 absolute encoder is immune to ageing effects and is unaffected by wide fluctuations in temperature.
The ferromagnetic steel contour disk is form fixed to the encoder shaft resulting in a highly robust unit.
Unlike optical systems that use transparent glass or plastic code discs it is practically impervious to dirt or vibration and is impervious to condensation.
At HKM the GEL 235 has removed the need to regularly install replacements at the taphole gun and since it was installed there have been no sensor related failures.
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