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| The Berthold mould level gauge is designed to measure the level of molten metal during the continuous casting of billets, blooms or slabs, primarily for the steel industry. The Berthold system detects actual molten metal level in the mold, over a measuring range of approximately 10 to 20 cm. |  |
Automatic control of the caster is also possible, in conjunction with controllers and actuators that adjust stopper rods, slidegates or withdrawal speed. In addition, automatic caster start-up or shutdown is facilitated using the signals provided by the Berthold system. |
Advantages Worldwide, more than 3000 continuous casting strands have been equipped with the Berthold mold level control system. Such wide usage stems from the following advantages: Reliability Berthold Gauges employ non-contacting measurement principles, unaffected by heat, dust, smoke, surface properties, or operator actions during slag removal. Ruggedness Components are installed below the mould cover, giving the operator full access during his cast and protecting the instrument in the event of overflow. Due to its small size, the detector can be easily protected against thermal, electromagnetic and mechanical influences. Ease of Calibration Automatic two-point calibration is a standard feature of the digital microprocessor amplifier used in the LB352. Berthold provides the user with a linear signal across the full measuring range through the use of rod sources with a special activity distribution. Safety Very low levels of radiation are present during operation. Radioactive sources are typically in the activity range of 40 to 700MBq (1 to 20mCi). Such low levels are made possible by the use of Berthold's highly efficient scintillation detector. Operators and maintenance workers require no special training, radiation badging or protective equipment when working around the LB 352.
Principles of Operation A radioactive source irradiates the mould. The molten steel rises, the radiation field is attenuated so that the scintillation detector, located on the opposite side of the mould, senses a different field strength. Within the detector crystal, the radiation generates flashes of light which are converted to electrical pulses through a photomultiplier tube. Finally, the detector pre-amplifier creates and generates standard electronic pulses.
The high-voltage generator is contained within the detector housing, allowing the connecting cable to carry only the low-voltage power supply and the electronic pulses to the remotely located Berthold amplifier. The Berthold microprocessor amplifier LB 352 evaluates the electronic pulses. The operator communicates with the amplifier via six pushbuttons on the front panel. Essential parameters may be input within wide ranges and the 5-digit display shows either percent of measuring range or actual mould level. Automatic calibration is provided by push button. The resultant 0/4 - 20 mA analog output signal is then available for integration with the mould level control systems.
Three approaches to System Engineering The LB352 has been successfully engineered for a wide variety of caster installation and operational requirements. New mould construction and retrofit installations, different cast sizes and shapes, varying mould changes, electromagnetic (EMS) stirrers and numerous other requirements have been met. Depending on the mould construction, Berthold offers three different arrangements for mould level measuring systems to ensure that the full range of customer engineering requirements are met.
| The External Arrangement Billet casters typically incorporate an externally mounted source with a shielding which is located outside the water cooling jacket directly beside the mould. The shield is lockable and can be opened or closed manually from the outside of the mould cover. The scintillation detector is located on the opposite side outside the water jacket or by using a protection tube partly inside the water jacket. |  |
| The Internal Arrangement This arrangement is requested generally for slab casters and for bloom casters. The lockable shield is installed in a protection pocket inside the water jacket.The scintillation detector on the opposite side is arranged partly inside the water jacket using a protection tube. |  |
| The Insertion Source System The requirements of retrofits to continuous casters and systems with electromagnetic stirrers, namely limited housing modifications and small component size, are met by the Berthold Insertion Source System. The rod source within a protection tube is inserted directly into the water jacket through the mould top flange. A portable transport and handling shield is provided, and this is placed atop the mould top cover for insertion and withdrawal of the source. |  |
Details Required for Custom Engineering For each of the three systems above, identical engineering issues must be addressed. Berthold aims to provide the minimum level of radioactivity in the rod source. This basic approach provides the expected accuracy, lowest price and optimum safety. To achieve this, the rod source and scintillation detector need to be placed as close as is practical to the mould walls. Thicknesses of copper, steel, water and other materials should be minimized where practical. Our engineers are available to recommend solutions for these issues.
In particular we require side and plane view mould drawings. All relevant dimensions of copper and steel thicknesses, water jacket size, location of adjacent moulds and structural limitations are needed. For caster operations, we need the desired measuring range and other operational information.
for more information, email
SE Asia and Australasia: industrial@berthold.com.au
North America: usinfo@berthold.com.au
Europe: euroinfo@berthold.com.au
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