welded construction, india

			BENEFITS OF ALL WELDED CONSTRUCTION
Higher % age of Open Area			Improvement in the quality of Coal with regard to Ash content is the focus area and gaining concern amongst the Coal producers and buyers due to environmental and other factors. While talking about ash content, one must also look at moisture content in coal. Because for reducing the ash content, the coal is to be washed and once it is washed the moisture must be properly removed to acceptable limits. This task is accomplished in Washeries through various screening machines like Vibratory Flat Screen Machine, Sieve Bends, and Centrifuges etc. In all these machines the Wedge Wire Screens Panels, Sieve Bends and Centrifuges Baskets – are the key elements affecting the screening efficiency and maintenance cost. In India, the looped construction wedge wire screens are being used which is an almost obsolete technology world over. All the mines in countries like - USA, Australia have long back switched over to a better concept – All Welded Wedge Wire Screens – which has certain distinctive advantages and gives better screening efficiencies and lesser maintenance cost as explained in detail in following explanation:- 1.Higher % age Open Area : All welded construction has no loop and hence the entire continous slot are exposed to material for processing. These continous slots provides approx 29% higher % age open area as compared to any loop construction. Following example clarifies this point: Panel size 1310 x 410 mm. Length in slot direction – 1310 mm. Wedge wire width – 3 mm. Height 6 mm, cross bar dia. 8 mm. Slot opening 0.5 mm No of Cross Bars – 19. Open area of each slot without considering blockage by loop = 1310 x 0.5 = 655 mm² Loop dia. = 8 + 2 x 6 = 20 mm. Area blocked per cross bar per slot = 20 x 0.5 = 10 mm² No of Cross bars = 19 \ Area blocked per slot = 19 x 10 = 190 mm² \ Nett open area = 655 – 190 = 465 mm² \ % loss of open area due to loop = (190/655) x 100 = 29% 2.Better Rigidity & Flexibility In Design : In case of looped wire panel only round crossbars can be used and there is a limitation on the size. Hence, it is required to use additional supports to give strength to panel. Whereas in case of all welded panel, various shapes of support rods and fins can be used to impart better strength to panel with much longer unsupported length and without blocking the screening area significantly. This also gives flexibility in designing optimum panel. 3.Better Strength : In case of all welded panel, each intersection of support rod with wedge wire is fusion welded to make them one metal. This joint is much stronger than a loop tied around support rod. The loops are more susceptible to breakage under vibration. In case of all welded panel, the support rods can be placed at closer center distance since they do not block the open area and due to flexibility in selecting the shape do not increase the weight appreciably. This reduces the unsupported span of wedge wire between two support rods giving much better load carrying strength to panel Wedge wire with more height can be easily used in case of all welded panel to get better strength. Whereas in looped wire more height of wedge wire means bigger loops, lesser open area and bulkier panel 4.Longer Service Life : Life of all welded panels is longer because of better strength. Wedge wire with less side angle and more height can be used in case of all welded panels which gives Longer Wear Life. In case of looped wire panels, the slot opens up when the loop is worn out. Due to lesser strength, the looped wire panels have to be used as crowned panels with bucker up bar. This results into channeling of feed and higher wear rate. Whereas due to better strength, the all welded panels can be used as flat decks without the need for bucker up bar. This simplifies the installation and better distribution of feed material. 5. Ease Of Installation : Due to better strength and wider choices of support rod shapes, the all welded panel does not require much additional support systems like bucker up bars, J-bolts, additional plate supports etc. which simplifies the installation and reduces overall mass compared to looped construction panels.
Flexibility In Design & Rigidity
Better Strength
Longer Service Life

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