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Within the total of over 100,000 non-contact radar devices supplied byVEGA, many have been installed into the steel and metal industries. The benefits of using non-contact microwave radar for process level measurement are many; microwave pulses are unaffected by temperature, pressure and noise, all of these conditions are found in abundance in thesteel industry!
Solutions that have already been provided intothe metals manufacturing industry over the last 12 years include; blast furnace 'burden level' and surface profiling, mould levels, viewingthrough refractory into aluminium smelters, as well as level measurement of raw supply materials - coal (raw and pulverised), coke, ore, and lime. Liquids too: oil, acid, alkali, boiler levels and effluents. There have even been some distance monitoring applications including; over conveyors, gas-holder roof levels, overhead cranes and hot coil positioning.
A non-contact microwave radar's main advantage in the steel industry is that it is virtually unaffected by the process material or temperature. Its non-contact capabilities make it a perfect solution when the temperatures are extreme, and molten metals can be inthe range of 1200-1600º C. Careful monitoring is needed for safety and process control, accidents when handling molten products can be verycostly in all senses of the word. Radar is also unaffected by dust and filling noise and new 70m long range systems have been specially developed for the measurement of solids in silos, which makes them idealfor burden level monitoring as well.
The torpedo ladle
Onedifficult application where radar has been successfully applied is continuous "torpedo ladle" level measurement. This is where the iron, tapped from the blast furnace is poured via a rocking spout into a waiting 'torpedo' shaped, refractory lined vessel, (approximately 10m long and 4m in diameter) mounted on a railway truck some 5m below. The molten iron is then transported to the BOS converter plant to be turned into steel in a separate process. The 'torpedo' rotates on its axis to discharge the molten iron.
Pouring a stream of molten iron into an oval hole approximately 2m x 1m, 7.5m away is a skilled and hazardous operation. Any overfilling or spillage can cause major damage to therail car and track as well as extreme danger to personnel in the area, not forgetting loss of production while clean up and repairs are made. If the vessels are not filled to an optimum level, under utilisingtheir capacity, transport costs increase and furnace output is jeopardised, further adding to the overall costs of production.
A Vegapuls radar now reliably monitors the level of this filling process. Ithas been trialled extensively on a Corus UK site for the last year and has proven its reliability and performance over other frequency modulated continuous wave (FMCW) radar systems installed in the same application, yet at a fraction of the cost.
The successful VEGA radar supplied is a two-wire loop powered device, mounted in the extraction hood approximately 7.5 metres above the top of the torpedo rail car. The transmitter uses high frequency microwaves at 26 GHz to providesharp focusing. The radar is also fitted with a new parabolic antennadesign further narrowing the beamed signal, making it focused enough to reliably look down, alongside the filling stream of metal, and through the vessel hole to monitor the level some 10m away as it is filled.
By using pulsed radar microwaves, the system is able to workunder these extreme conditions. Vega's PACTware set up software program also enables engineers to easily 'see what the radar sees' remotely.In addition, Echofox signal processing gates out unwanted signals andinterference from the filling stream including the clouds of fume generated.
As a result of this, a total of eight more systemsare to be ordered to monitor all the fill points under the blast furnace. "We have monitored the performance of over 500 fills and are verypleased with the reliability, accuracy and performance," said the Corus TCP Engineer.
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