Miller Magazine Issue: 135 March 2021

77 ARTICLE MILLER / march 2021 the milling industry, where dusts of various character- istics and sizes are widespread, it is a must to evaluate the machinery, systems and components both in the already established facilities and the ones that are still in the process of production and to carry out their de- sign and operation safely within the framework of the legislation in force in Turkey. 3. Applications in the milling industry The explosion in the WASTERBURN "A" Mill flour mill in Minneapolis, USA in 1878 was the first known mill plant explosion in the world and 22 people died in this incident. As known, the milling sector forms a whole sys- tem consisting of many machinery and components in the process of raw material becoming final prod- uct. These can be listed as conveying systems, stor- age systems, sorting machines, milling machinery and packaging machinery. The sub-components of the systems specified are demonstrated in Table 5. When the specified system and sub-components are examined, it is seen that ATEX assessment can Figure – 6 Wasterburn A Mill mill plant [19] Table 1. Reasons of dust explosions [12] Reason Rate (%) Mechanical sparks 30 Weld environment 9 Static electricity 9 Friction 9 Direct fire 8 Hot surfaces 6,5 Self-ignition 6 Weld 5 Unknown reasons 11,5 Electrical equipment 3,5 Other 2,5 Table 2. Sectors most affected by dust explosions [12] Sector Rate (%) Woodworking industry 34 Grain industry 24 Synthetic chemical 14 Coal industry 10 Metal industry 10 Other industries 6 Paper industry 2 Table 4. Properties of various explosive dusts [20] Flour Corn flour Sugar Corn starch Milk powder Grain dust Min. Ignition en. (mJ) 50 40 30 30 50 30 Min. Cloud Ig- nition. temp. (°C) 380 380 370 290 490 490 Layer ignition temp. (°C) 360 330 400 330 200 300 Max. Exp. pressure (Bar) 9,8 10,3 9,5 10,3 9,8 9,3 Explosion spe- ed (Bar.m/s) 70 125 138 202 12,5 240 Min. Exp. conc. (g/m3) 125 60 60 110 60 150 Min. Oxygen cons. (%) 11 9 - - - - Table 3. Facilities where dust explosions occur [13] Facility Explosive dust Facility Explosive dust Power plants Coal dust Textile industry Product dust Foundry Resin powder PVC production PVC dust Grain mill Grain dust Pharmaceutical pro- duction Vitamin dust Aluminum coating Aluminum powder Woodworking Wood dust Paper production Paper dust Grain production Grain dust Fiberglass Resin powder Bakery Baking residues Tire Rubber dust Rubber processing Polyethylene dust Plastic production Resin powder Bicycle assembly Aluminum dust Livestock feed plant Seed Powder metallurgy Aluminum dust