Thickness Measuring Systems. Thickness Measuring Systems

Transcription

1 Thickness Measuring Systems Thickness Measuring Systems

2 Exactly how reliable are your Gauging Systems? Thickness measuring systems in various production lines Thickness and profile measurement Increasing automation and continual improvements in production out-put in the ferrous and non-ferrous industries have raised the demands placed on the gauging systems used in the production process. In addition to the material qualities of formability and strength, other criteria of high interest are dimensional accuracy, flatness and surface quality. Innovative development in the field of thickness and profile measurement technology has enabled IMS to face this challenge and contribute greatly to ensuring compliance with industry quality standards. IMS thickness gauging systems are used in cold and hot-mill applica tions in the steel, aluminium and other nonferrous industries. They usually consist of a front-end measur ing position, a computer system for measuring signal processing and external peripherals. They are normally also equipped with data archiving systems for statistical analysis and evaluation for quality control purposes. Strip thickness is measured on-line to a very high accuracy (< ± 0.1%) at measuring time constants in the order of 1 ms. All measurement is non-contact and the strip quality is not degraded by the measuring process. IMS gauging systems are designed and engineered for long-term use in industrial applications. Users may be assured of long gauge life in the prevailing plant conditions and of convenient and easy operation. New gauging systems are developed and engineered with full regard to the technical requirements of the customer. The main criteria used by IMS in this respect are high opera tional reliability and quality of measurement. The variety of gauge types available in the IMS product range enables a customised solution to be found for every task in the field of non-contact thickness measurement. IMS is able to meet the demand for increasingly high measuring accuracy and lower time constant measurement with simultaneous reductions in the signal-to-noise ratio. System configuration The standard configuration of an IMS thickness gauging system (see fig. top right) consists of a front-end measuring position with a radiation source (x-ray tube or radioisotope) and an electronics cubicle housing an integrated computer system for measuring signal processing. Additional operator stations and external peripherals such as printers, chart recorders and display devices can be integrated into the gauging system. All types of interface are provided for data communication between the customer s host computer and the IMS gauge computer. The modular design of the gauge hardware and software offers numerous possibilities for extension. A standard Windows operating system allows the operator to work in a familiar environment. Gauge operation and service & maintenance functions are supported by user-friendly monitor screens. Gauging system performance can be analysed and problems diagnosed remotely from our main plant in Germany to any location in the world through interroga tion of gauge operation via built-in communication interfaces. Depending on the particular application, thickness and profile gauging systems can be supple mented by additional measurements from the IMS product range.

3 MMI PDA Detector C-frame MU Ethernet Ethernet Costumer network FW X-ray tube HSG HSG= High voltage generator MU = Measuring transducer FW = Remote maintenance/diagnostics MMI = Operation and visualisation interfaces PDA = Product data archive Typical thickness gauge layout They include: Flatness measurement Width measurement Temperature and temperature profile measurement Speed and length measurement All gauging systems are equipped with manual and automatic performance monitoring facilities for the determination of repeatability and correct gauge operation. The gauges are optimised during system calibration by mathematical calculation. The calibration data from every calibration cycle is logged and can be archived for future reference if required. Front-end measuring position The large variety of C-frame designs means that IMS gauging systems can be applied individually through - out the plant for all the different types of measurement. The following examples give a brief overview of the types of front-end measuring equipment available and of the possibilities for strip thickness measurement: Thickness gauge measuring at the center of the strip (length profile) X-ray control unit Multi-channel gauge measuring cross-profile and center-line thickness (length profile) Multi-channel gauge measuring edge-drop profiles and the center-line thickness Multi-channel gauge measuring cross-profile, edge-drop profiles and center-line thickness including width measure ments The IMS multi-channel profile gauge provides a measurement of the thickness profile across the full width of the strip (or plate). The top arm of the C-frame is equipped with a number of x-ray tubes or radioisotope sources depending on the application. In profile gauges with two radiation sources the two radiation beams view the complete width of the strip stereoscopically. For gauges equipped with four radiation sources the sources are arranged into two pairs in such a way that one pair of radiation beams views say the drive side half of the strip and the other pair the operator side half of the strip. Again, all measurement is per formed stereoscopically. The bottom arm of the C-frame is equipped with a number of ionisation chamber detectors. During profile measurement the complete Ethernet C-frame oscillates at a frequency of 1.5 Hz to 2 Hz through an amplitude of ± 20 mm. Each profile channel views a strip width of 8 mm. The oscillation function of the C-frame ensures continuous and complete measurement of the cross-strip profile. In order to obtain optimum measuring results the radiation beam exit and entrance windows after the radiation sources and before the detectors must remain clean. In IMS gauges either an air blower or compressed air is used to perform this duty. The C-frame is supplied with an adequate quantity of clean air via plastic hoses and/or metal pipes. The electrical supplies to the blower motor and the gauging system are kept separate. Cooling The cooling medium for the x-ray tubes can be either water or mill coolant. In hot-mill applications the C-frames are also cooled with water (clean and oil-free). The cooling medium is cooled in a closed-circuit cooling system developed by IMS. This system is dimensioned for the particular application, thereby ensur-

4 ing optimum heat exchange. All cooling circuits are monitored for pressure, temperature and flow. Measuring principle IMS thickness gauges operate on the principle of transmission radiation. X-ray or isotope radiation emitted from a radiation source passes through the object being measured (e.g. the strip). A detector located at the other side of the strip measures radiation intensity. In IMS gauges this detector always takes the form of an ionisation chamber, designed specifically for the application. As the radiation passes through the strip some of it is absorbed by the strip material. The remaining, i.e. non-absorbed radiation arrives at the detector. The detector measures the intensity of this radiation and produces an ionisation current Im (the measuring signal), which is proportional to the thickness of the strip. The ionisation current is converted into a digital signal in a measuring transducer, which is located in the C-frame. It is then transmitted to the gauge signal processing com puter via an Ethernet TCP/IP link. The output signal from the gauge computer represents the strip thickness. Today s gauging systems are equipped with modern x-ray technology. The main advantage of x- ray radiation is that the signal noise is very much smaller than that from an isotope gauge. The x-ray energy level is optimised for each particular application by careful selection of the high voltage supply to the x-ray tube. As a result of this optimisation a very high measuring accuracy is achieved at very low measuring time constants. Another advantage of x-ray gauges over isotope gauges is that x-ray radiation can be switched off during production breaks and downtimes. This is normally of particular interests to the mill operator. Multi-channel profile gauge X-ray high voltage generator and measuring transducer built into C-frame Thickness gauge measuring principle Signal processing electronics Detector Absorber Thickness s I 0 I m I m = I 0 e -μ s l o l m s μ Detector signal without absorber Detector signal with absorber Thickness of absorber Attenuation coefficient Radioisotope or x-ray radiation source X s s

5 Safety IMS gauging systems are equipped with safety features that go beyond normal legal requirements. Safety switches, emergency shut-off devices, component identifica tion and hazard warnings are self-explanatory and clearly marked. Gauging systems using x-ray or isotope radiation are subject to especially strict regulations. Radia tion status light boxes and built-in redundant alarms are used to indicate the open/ closed status of the shutter(s) and the possible presence of radiation. Heavy duty cabling is used for the electrical connection of all components performing safety functions. The statuses of safety devices are monitored continually by the gau ge computer. All irregularities are logged and warnings signalled. The shutter unit(s) is opened pneumatically and closes automatically by the operation of a return spring in the event of a drop in air pressure. The safety aspects of IMS gauges are described in detail in our system documentation, which is available as a written manual and on DVD. All system documentation is supplied in German or English. Other languages can be accommodated on request. Technical specifications The main IMS gauge specifications and gauge performance figures: Product data Measuring range: maximum 180 mm C-frame air gap Thickness measurement: 50 mm to 3,000 mm Profile measurement: 100 mm to 2,600 mm C-frame throat depth Thickness measurement: 350 mm to 6,000 mm Profile measurement: 500 mm to 4,000 mm Measuring dynamics Measuring time constant: 1 to 10 ms, adjustable Measured value processing cycle time: 1 to 10 ms Measured value output cycle time: 1 to 10 ms Gauge performance Measuring accuracy (repeatability + linearity): ± 0.1%, not better than ± 0.2 μm Statistical noise 2σ: < ± 0.1% at T = 1 to 5 ms (T = integration time) Availability: 99.5 % Detectors Number of measuring channels: 1 to 200 Detectors: Ionisation chamber, efficiency maximum 98 % Type of radiation X-ray radiation: 10 to 160 kv Radioisotope radiation: Caesium Cs 137 Shutter unit: Pneumatic: air pressure to open (auto-close by return spring) General specifications Construction: Industry standard Measured value processing: Powerful computer with multi-processor technology C-frame drive: Electric or pneumatic Oscillation drive: Electric / frequency converter (only for profile measurement) Measuring position air wipe: High performance blower 400 V, 21 kw, or compressed air Power supply: 230/400 V AC, 50/60 Hz, maximum 5 kva Weight: Maximum ca 10 t From top to bottom: Center-line thickness gauge (strip length profile) Multi-channel cross-profile gauge with center-line measurement Multi-channel edge-drop gauge with center-line measurement Multi-channel profile and edge-drop gauge with width and flatness measurements

6 You can also find brochures on other products in the download section of our internet site at IMS Messsysteme GmbH Dieselstraße Heiligenhaus Postfach Heiligenhaus Germany phone: fax: internet: IMS Messsysteme GmbH, Heiligenhaus All rights reserved. This publication is protected in all parts by copyright. Distribution and reproduction without the prior written consent of IMS Messsysteme GmbH is strictly prohibited. All company and product names used in this documentation may be registered trademarks AN /04.12