Venting, dust explosions

Tamanini, F., Turbulence Effects on Dust Explosion Venting, Ibid, p. 52. 

Siwek, R., Dust Explosion Venting for Dusts Pneumatically Conveyed into Vessels, Ibid., p. 129. 

The first alternatives are well docmnented in the relevant technical regulations. Detailed information on the design of dust explosion relief systems can be found in the German VDI-3673, the British guide on dust explosion venting HSE 1977 and the US standard NFPA 68. 

The equipment in which the dust is handled or stored should be designed to contain the pressure resulting from an internal explosion. Most dusts show maximum pressures of ca 345—700 kPa (50—100 psi) however, the rate of pressure rise changes from ca 700 to 70,000 kPa/s (100—10,000 psi/s). Equipment-containment design can be coupled with explosive-venting design for the equipment and the building. 

Proper ventilation and housekeeping minimizes secondary explosions. Dust coUectors of the dry type should be located outside the building, and provided with conduction bags and adequate explosion venting to a safe location. 

Lunn, G.A. (1984) Venting Gas and Dust Explosions - A Review, Instn of Chem. Eng., London. 

Figures 7-65A through H are the venting area requirements for dust explosions. These are based on high energy ignition sources.

Table 7-31 lists the explosibility index that is a relative measure of the potential damage from a dust explosion. A rating of 2 to 4 requires large vent areas. Above 4, for most cases, the explosion cannot be controlled by venting design and therefore requires the use of protection such as inert gas or explosive suppression systems, some of which are commercially available. 

Explosion calculations, 499-504 Estimating destruction, 501 Overpressure, 502 Pressure piling, 501, 504 Relief sizing, 505 Scaled distance, 502, 503 Schock from velocity, 503 TNT equivalent, 499-504 Explosion characteristics of dusts, 515 Explosion suppression, 518 Explosion venting, gases/vapors, 504 Bleves, 504 Explosions, 482 Blast pressure. 496 Combustion, 482 Confined, 482 Damage, 498-501 Deflagration, 482 Detonation, 483... 

Other references include CCPS Guidelines for Engineering Design for Process Safety (Ref. 78) NFPA 68 Venting of Deflagrations (Ref. 79) NFPA 69 Explosion Prevention Systems (Ref. 80) NFPA 654 Prevention of Fire and Dust Explosions in the Chemical Dye, Pharmaceutical, and Plastics Industries (Ref. 81) and VDI 3673 Pressure Release of Dust Explosions (Ref. 82). 

W. Bartknecht, Pressure Venting of Dust Explosions in Large Vessels, Plant/Operations Progress (October 1986), 5(4) 196. 

A further loss-limiting device which is useful where flammable dusts and vapors are used is the explosion vent. It is important to install explosion vents in areas where flammable liquids or dusts are used because of the possibility of great damage due to explosive ignition of such mixtures and air. Therefore, on a practical basis,... 

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