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VEGA Controls has revealed that its non-contact VEGApuls level radars have been selected by Tata Steel in Scunthorpe for use in freeboard measurement, delivering productivity and safety benefits.

The steel works produces steel slab, billets, structural sections, rail, and wire rod for the UK and world markets, with a focus on plant efficiencies and process improvement strategies.

Once the iron is manufactured in the blast furnaces, it is transported in a rail-mounted ’torpedo’ vessel to the basic oxygen steelmaking (BOS) plant for conversion to steel.

When it arrives at the BOS plant, 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 is referred to as ’freeboard’ – in a steel works this is the difference between the top edge of the ladle and the surface of molten metal level inside.

This parameter is 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.

There are challenges, even for experienced operators, with the very high radiated temperatures, glare, molten steel and sparks during a tapping operation.

The operators normally pick a point on the ladle and watch it carefully as the molten steel fills to the required freeboard.

But eyes and ladles vary, so getting an accurate, safe level of molten steel can be challenging and the levels always correctly err on the safe, low side.

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 is significant.

Tata selected non-contact Vegapuls radars to assist with this application.

VEGA has experience of applying level measurement across the steel industry, including blast furnace burden level, off-gas duct build-up monitoring, torpedo and ladle level, as well as bulk solids level measurement of raw materials such as ore, coke, coal and lime in both bulk and day bunkers.

VEGApuls radars work using low-power microwave pulses that are reflected from the surface to measure the level – in this case the molten steel in the ladle.

They are largely unaffected by temperature, pressure, dust or vapours.

The technical manager of VEGA attended the site to test a temporary setup system – the results were encouraging and as a result of the report provided Tata ordered a permanent system.

For this application, 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.

A purging system is also installed should build-up of dust occur in the antenna over time; it can also be used for cooling on some applications, however, to date neither function has been required on this application.

The VEGApuls radar is mounted approximately 8m above the low level point, but still capable of measuring the level to a repeatability of 2mm.

With a narrow focused beam and signal processing software, it reads the level in real time, even during filling.

By enabling a safer, more accurate measured fill each time, Tata is achieving an average of 100mm extra in each vessel, equating to an extra 10 tonnes per ladle.

This improvement on all three transfer stations will contribute towards GBP12m/yr efficiencies on the plant.

VEGA has also provided after-sales engineering support, commissioning and training for technicians on the site, underwritten by its standard three-year UK warranty, even in this harsh environment.

VEGA Level measurement, Level switches and Pressure Transmitters – world leading manufacturer of control and switching instrumentation and measurement solutions for Liquids, Solids and Gases for storage, processing and control of products.

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