53 Ignition of Dust Clouds in Air 531 Introduction 1
A combustible dust cloud will not start to burn unless it becomes ignited by a source of heat of sufficient strength. The most common ignition sources are open flames welding, cutting, matches, etc. hot surfaces hot bearings, dryers, heaters, etc. heat from mechanical impacts electrical discharges and arcs In addition, there are some more sophisticated potential ignition sources including adiabatic compression and shock waves There is considerable variation in the ignition sensitivity of clouds...
84 Analysis of Systems Reliability by Fault Tree Analysis
This method is applied to complex systems, whether the complexity is due to the nature of the process itself or to the instrumentation required for running the process. In the basic technique, the Fault Tree Analysis, the failure modes must first be identified, e.g. by HAZOP. These failure modes are named top events. An example of a top event could be a dust explosion in a milling plant. For each top event. the analyst must then identify all those events or combinations of events that could...
342 Ignition by ElectricElectrostatic SparksDischarges
Explosive sprays mist can be ignited by electric spark discharges in the same way as premixed gaseous fuel air mixtures can. In principle, therefore, the concepts of Minimum Ignition Energy MIE and Quenching Distance QD are equally valid for sprays mists as for premixed gases. However, in the case of spray mists the experimental determination is considerably more difficult. Figure 3-7 gives a set of data showing the influence of spark gap length on minimum ignition energy of a suspension of...
543 Three Grain Dust Explosions in Norway 19701988
5.4.3.1 Wheat Grain Dust, Stavanger Port Silo, June 1970 The explosion occurred in Norway's largest and newly built import grain silo in Stavanger on a hot and dry summer day. Fortunately, no persons were killed, but some workers suffered first degree burns. Although the extent of flame propagation was considerable, the material damage was moderate due to the comparatively strong reinforced concrete structure of the buildings and the venting through existing openings. The entire event lasted...
212 Laminar Burning of Premixed GasVapor and Air
Figure 2-3 gives experimentally determined relationships between the so-called laminar burning velocity and the concentration of combustible gas in the mixture with air for four common combustible gases. The ideal laminar burning velocity is the lowest velocity at which a flame front can propagate through a given gas mixture given ratio of gas to air, 60 80 loo 120 140 160 Fuel conc. in of stoichiom. conc.
144 Migration of Dust Particles and Liquid Droplets through Narrow Holes and
Because dust particles and liquid droplets are so much bigger than gas molecules, they will not travel through narrow holes and slots of the order of 1 mm diameter and smaller in the same way as gas molecules will do. In principle, dust particles and liquid droplets may be carried through narrow passages by the air flow generated by a moderate pressure difference across the passage. However, both dust particles and liquid droplets will easily adhere to the area around the passage entrance and...