Miller Magazine Issue: 155 November 2022

92 MILLER / NOVEMBER 2022 the system suppliers. Below you will see several commonly used explosion prevention and protection examples used in the feed and grain handling processes. Spark Detection Systems (prevention) – the goal is to identify sparks, hot particles or ambers within a pneumatic conveying system or within a chute, and extinguish it via at- omized water extinguishers before ignition source reaches a combus- tible volume thus reducing the risk of fires and explosions. Typical applications in the feed and grain industries includes dust collector/ aspiration duct spark detection and extinguishment, mill outlet spark de- tection and extinguishment, bucket elevator inlet / outlet chute spark detection and extinguishment. Example 1 – Dust collector inlet pipe spark detection and extinguishment application. Main components are 1 : pair of IR detectors (for detecting sparks and hot particles), 2: water extinguisher at high pressure,3 : signal router/local controller,4: control panel, 5: alarm and flash light, 6: pro- grammable relay, 7: linear heat detector, 8: pressure boost- er controller, 9: pressure booster. Example 2 – Animal feed manufactur- ing plant spark detector and extinguish- ment. The goal here is to detect sparks and hot particles created after the mill, elevator and pellet press and extinguish it before these ignition sources reaches an explosible zone (process vessel). Explosion Venting and Isolation (protection)- The goal is to relieve the Material Auto ignition Temp., AIT [ o C] Min Ignition Energy, MIE [mJ] Min Explosible Dust Cloud Conc., MEC [g/m 3 ] Max Explosion Pressure, P max [bar] K st [bar.m/s] Dust Class Malt 420 - 60 7.5 170 I Corn 400 40 45 6.6 1 37 I Corn husk 400 40 30 7.6 115 I Corn starch 380 20 40 7.9 206 II Grain, mixed 430 30 55 7.9 126 I Rice 440 40 45 6.4 82 I Wheat 480 60 55 7.1 82 I Table 2 – Reference explosibility and ignitability values for grain dusts. Values taken from NFPA 61 and 68. These values are for indicative purposes only. The actual values change with the moisture content and particle size of the material thus needs to be tested. Table 3 – Ignition sources found in the combustible dust handling facilities 4 ARTICLE