Ladle radars help Tata Steel to £12m savings
15 Apr 2011
Scunthorpe, UK – Tata Steel in Scunthorpe is running at full capacity again producing steel slab, billets, structural sections, rail and wire rod for the UK and world markets now recovering from the global downturn.
Iron is manufactured in the blast furnaces is transported in a rail mounted ’torpedo’ vessel to the basic oxygen steelmaking (BOS) plant for conversion to steel. There, it is discharged into large 300-ton capacity ladles used for both charging the converters and receiving the finished steel once the process is complete.
The level in a steel-pouring ladle, known as ’freeboard’, is the difference between the top edge of the ladle and the surface of molten metal level inside. This important parameter in a steelmaking plants is very difficult to determine accurately and repeatably, especially while the steel is being ’tapped’ from the converter.
After it is filled, it is often also mixed with an argon lance to prevent stratification and homogenise any additives, if the steel level is too high, the turbulence could cause dangerous spills.
However, ensuring the capacity of the ladles is also maximised for every fill plays a key part in efficiency on the plant, where a few centimetres represents tonnes of steel. So there are challenges, even for the most experienced operator, with the very high radiated temperatures, glare, molten steel and sparks during a tapping operation.
The operators are skilled and careful, they normally pick a point on the ladle and watch it carefully as the molten steel fills to the required ’freeboard’. But all eyes and ladles vary slightly, so getting an accurate, safe level of molten steel can be challenging and the levels always correctly err on the safe, low side.
So, if the freeboard measurement could be augmented to be more reliable and consistent then, with the increased productivity and safer handling of the product over the thousands of fills per year, the potential for efficiencies are huge.
These issues led Tata to install VEGA non-contact Vegapuls radars. These devices use low power microwave pulses which are reflected from the surface to measure the level of molten metal in the ladle, and are largely unaffected by temperature, pressure, dust or vapours.
VEGA supplied units fitted with an extended, right angled wave guide tube to keep the electronics away from the hot area where the antenna is mounted.
The radar device is mounted about 8m above the low level point, but still capable of measuring the level to a repeatability of 2mm, said VEGA. With a narrow focussed beam and signal processing software, it reads the level real-time, even during filling.
By enabling a safer, more accurate measured fill each time, Tata is now achieving an average of just 100mm extra level in each vessel – equivalent to an extra 10 tonnes per ladle.
“This improvement on all three transfer stations, will contribute towards £12million a-year efficiencies on the plant,” according to a VEGA statement.
