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DS 7-76 Prevention and Mitigation of Combustible Dust ... - FM Global

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7-<strong>76</strong> <strong>Combustible</strong> <strong>Dust</strong> Explosion<br />

Page 16 <strong>FM</strong> <strong>Global</strong> Property Loss <strong>Prevention</strong> Data Sheets<br />

2.3.3.3.6 Flame Front Diverter or Explosion Diverter<br />

a) Do not install this device upstream <strong>of</strong> an air-moving fan because an explosion originating upstream<br />

<strong>of</strong> the diverter will propagate past the diverter.<br />

b) Do not use explosion diverters in air streams that have a significant loading <strong>of</strong> abrasive dust that would<br />

eventually erode through the pressure-relieving diverter cover.<br />

c) Do not use explosion diverters for hybrid mixtures where the flammable vapors exceed the LEL.<br />

d) Flame-front diverters built commercially or inhouse according to design guidelines in Figure 6 are<br />

acceptable.<br />

e) Ensure a prefabricated rupture disk used for the pressure-venting opening has a release pressure equal<br />

to or less than 0.1 barg (1.5 psig).<br />

f) Where the diverter is constructed in house <strong>and</strong> a prefabricated rupture disk is not used, ensure the<br />

device meets the following criteria:<br />

1. When providing a solid cover, ensure it will quickly <strong>and</strong> easily release during an explosion.<br />

2. When providing a rupture membrane, use a weak weather-resistant material, such as aluminum<br />

foil or tar paper.<br />

3. Confirm the rupture pressure is at or below 0.1 barg (1.5 psig) by calculations or pressure testing.<br />

Base this calculation on the ultimate tensile strength <strong>of</strong> the material.<br />

2.3.3.3.7 High Speed Abort Gate<br />

Fig. 6. Acceptable design parameters for explosion diverters<br />

a) Actuate the high-speed abort gate by either pressure detection or infrared explosion detection in the<br />

upstream vessel expected to experience the explosion.<br />

b) Ensure the detection system <strong>and</strong> abort-gate responses are fast enough to completely close the abort<br />

gate before the dust flame front reaches it. (See Section 3.1.15 for how to estimate the flame front travel<br />

time.)<br />

©2008 Factory Mutual Insurance Company. All rights reserved.

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