Venting, explosions

Protection against explosions is typically provided by explosion-venting, using panels or membranes which vent an incipient explosion before it can develop dangerous pressures (11,60). Protection from explosions can be provided by isolation, either by distance or barricades. Because of the destmctive effects of explosions, improvement in explosion-prevention instmmentation, control systems, or overpressure protection should receive high priority. 

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. 

The vessel cover is free of drive components, allowing space for additional process nozzles, manholes, explosion venting, etc., as well as a temperatrrre lance for direct, continrrorrs prodrrct-temperatrrre... 

Explosion prevention by inerting has several advantages over explosion protection techniques, such as explosion venting. For example, with successful inerting, fires or business interruptions cannot occur. Nevertheless, beware of the potential of asphyxiation with inerting proper vessel entry procedures must be implemented and occasionally it may be prudent to monitor for oxygen in workplaces. 

Locate explosion vents as close as possible to the most likely ignition sources. 

Do not discharge explosion vents within buildings serious fires and explosions have occurred by such venting. 

TABLE 26-17 Explosion Venting Equation for Quiescent Gases... 

Capable of withstanding an explosion overpressure reduced by explosion suppression or explosion venting... 

Explosion venting is always accompanied by flame propagation plus pressure consequences in the surrounding areas. Tne flame length will be larger with a lesser static activation pressure and smaller vent area. Depending on the volume of the protected equipment, it can reach up to 50 m. The pressure effect in the vicinity of the vent area is... 

TABLE 26-22 Explosion Venting System Design Parameters... 

Comparison of E] q)losion Protection Design Measures In Table 26-24, comparison is made of the explosion protection design measures of containment, explosion venting, and explosion suppression. Regarding the effectiveness of the different explosion design measures, all three techniques are equal if the design of these measures is performed properly. 

The loss of material hy using containment and explosion venting is always much greater than that hy using explosion suppression. 

Consider need for inerting, flame arresters, pressure relief valves, explosion vents (venting to safe location)... 

Mitigation System Resmnses Dikes and drainage. Hares, Fire protection systems (active and passive). Explosion vents. Toxic gas absorption... 

Schofield, C. Guide to Duct Explosion Venting. London Institution of Chemical i-n incenrii . (1984). 

After three months of operation mild explosion vent panel lifted. 

After three months c f operation mild explosion vent panel lifted. Three weeks later another explosion roof blown off tank. 

Hoses and ducts used for conveying explosive powders should be made from conducting material and be grounded throughout. Alternatively (or additionally) the atmosphere can be inerted with nitrogen, the ducts can be made strong enough to withstand the explosion, or an explosion vent can be provided. 

Lapp, K. 1982. Detonation Flame Arresters and Protected Side Explosion Venting. Paper presented at the 1992 ILTA Conference, June 23, 1992. 

Bakke, J. R., and B. H. Hjertager. 1986b. The effect of explosion venting in obstructed channels. In Modeling and Simulation in Engineering. New York Elsevier, pp. 237-241. 

Buildings erected must be adequate witli respect to explosion venting and ventilation, firewalls, exits, drainage, and electrical wiring. The safety of the equipment and the structures is often a function of tlieir age. Tlie degree of "adequacy" must be evaluated based on tliis as well as the factors above. 

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