Guidelines for the Investigation of Grain Dust Explosions Report (1983) / Chapter Skim
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INVESTIGATIVE METHODOLOGY
INVESTIGATIVE METHODOLOGY
Pages 5-12
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From page 5... ...
Dust explosions occur when structures rupture due to the pressure generated by the very rapid combustion of suspended dust in air after ignition by a source with energy sufficient to ignite dust. In most cases ignition sources with energies of at least 10 to 20 millijoules are required, but, upon investigation, one finds that the primary ignition sources have generally many times the minimum energy required.
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From page 6... ...
The interior design of headhouses varies from some in which the bucket elevators are in steel enclosures in open areas to those in which the elevation equipment is inside hollow concrete wells or shafts. All elevators contain storage bins, either for primary storage or for use as "working bins," that are generally within the framework of the headhouse.
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From page 7... ...
Hence, it is fairly important that the investigator have a mental picture of what the physics of the explosion process were in order to help locate the origin and identify the directions of propagation. METHODOLOGY The purpose of the investigation is to identify the original source of ignition and couple this with information concerning the available dust loading (i.e., quantity of layered dust per unit volume)
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From page 8... ...
Some of the important clues include the direction rubble is thrown and the extent of damage of various structural elements such as I-beams, concrete walls, reinforcing bars, or other items. In locations such as tunnels or galleries, where there may be light construction items such as spouting, particular attention should be paid to the extent of deformation and indications of the direction of the pressure wave.
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From page 9... ...
Damage exterior to the main structure may also provide clues in some cases. Differences in damage adjacent to various openings in the main elevator structure can provide clues to the intensity of the pressure wave coming from the various apertures.
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From page 10... ...
The elevator, primarily of wood, was burned to the ground leaving no evidence of blast effects that may have occurred due to an initial dust explosion. However, from later examination and information provided by people associated with the operation, it was determined that there was an initial leakage of propane -- from a line recently installed to provide fuel for a dryer -- into an adjacent structure where ignition occurred during grain loading and unloading operations.
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From page 11... ...
Laboratory tests may be necessary to determine fracture mechanisms, burn sequence, etc. It is important that appropriate laboratory facilities be available to the investigating team.
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