This paper describes the design and development of a very simple low-cost online system for measuring the length of moving billets in the steel industry. Few photosensors, digital logic gates, and light-emitting diodes are used to track and display the wide variation in billet length. Not a single amplifier or comparator is used in photosensor circuit. The comparative study shows its superiority over other costly dimension-measuring systems, viz., shaft encoder, laser Doppler meter, and charge-coupled-device camera. Before, an operator had a risk of an accident while crossing the hot-cobble-prone area for measuring the billet length. However, today, the length of each billet is displayed in a pulpit, thereby increasing the safety. The measuring error in the billet length, ranging from +100 to -100 mm, is reduced to +50 mm. The fluctuation in linear velocity of an incoming billet to a flying shear causes wide variation in its cut lengths. To overcome this severe problem, the speed of the flying shear is adjusted during the tail end of each billet. The benefit of the system is in the tune of Rs 49.5 times 106 (approximately U.S. $1.26 times 106) per annum, whereas the payback period is less than 15 days. Apart from the different steel products like the slab, bloom, and rail, the developed system is also useful in the dimensional measurement of the products in nonferrous industries.
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