Robust sensors help to precisely monitor a continuous casting process
Published: 22 March 2012 - Rachael Morling
Sensors from Penny + Giles have been supplied to Sarclad to provide critical measurements for its In-Chain Strand Condition Monitor (In-Chain SCM), an online measurement system designed to monitor continuous casting machine rolls used in the steel making process.
Permanently installed, the monitor enables automatic fixed-roll alignment and roll-gap measurements to be performed at the beginning of every casting, without affecting production activities – a benefit as continuous cast systems can produce in excess of $1million worth of steel in a day.
For this, Penny + Giles supplied STT280 tilt sensors and SRH280DP rotary sensors. The tilt sensors are fitted to the In-Chain SCM to measure the fixed-roll alignment of the casting machine using spring-loaded blades that tangent pairs of rolls to measure the angles between them. The data is then processed to identify rolls and segments that are out of position relative to other rolls within each segment. Compact and robust, the tilt sensors feature 3D-MEMS technology which provides a naturally-damped response that is unaffected by knocking or vibration to ensure accurate measurement. This is essential in the continuous steelmaking operation which involves pouring molten steel into a caster mould and oscillating the mould to prevent the liquid steel sticking to the sides while it solidifies.
The caster operates from 90° vertical to 0° horizontal, so in order to accurately measure between the two angles it is necessary to measure beyond them. Penny + Giles customised the STT280 sensor to measure between 92° and –2°, providing the calibration points needed outside the measuring range.
The STT280 tilt sensor features a choice of measurement ranges from ±10°, ±20°, ±30° and ±60°, with an output range from 0.5 to 4.5Vdc over the full inclination angle and a nominal 2.5Vdc at 0° tilt. It can also operate from a 5Vdc regulated or eight to 30Vdc unregulated supply and uses solid state 3D-MEMS (Micro-Electro-Mechanical Systems) technology to measure its inclination relative to earth’s gravity.
SRH280DP rotary Hall effect sensors are being used to measure gap displacement on the In-Chain SCM system, replacing the rotary inductive position sensor (RIPS) used in the original design. When Penny + Giles introduced the SRH280 to provide uniform feedback, Sarclad immediately realised its benefits even though it was only initially launched as a single channel sensor. The range was programmable, which allowed the company to get the maximum resolution from the 30° rotation output required. Sarclad now uses the recently developed SRH280DP two channel version, which can be configured with both channel outputs increasing with clockwise or anti-clockwise shaft rotation, or one clockwise with one anti-clockwise. The sensor is fitted as part of a gap transducer, which has a spring-loaded rotary arm that extends out to contact the caster rolls to provide an absolute measurement for the distance between the pair of opposing rolls. Suitable for use where shock and vibration can occur, the IP68-rated SRH280DP sensor operates from either a 5Vdc regulated or 9-30Vdc unregulated power supply and is available with analogue (0.5 to 4.5Vdc) or digital (PWM) output signals. Factory programmable, this also has a 12 bit resolution (0.025%) over the selected measuring range, and operates from -40 to +140°C when powered at 5Vdc.
Penny + Giles
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