(100a) Application of a Short Cut Risk Analysis Methodology for Analyzing Dust Explosion Hazards

The hazards of dust explosions prevailing in plants are dependent on a large variety of factors that include process parameters, such as pressure and temperature, as well as equipment properties, such as the presence of moving elements, dust explosion characteristics and mitigating measures. In this paper a semi-quantitative short-cut risk analysis method (SCRAM) is presented, allowing for the assessment of such hazards. The method is first described and two application examples are presented.

SCRAM is based on semi-quantitative descriptions of both the likelihood of dust explosions occurring and the consequences of such explosions. The likelihood of dust explosions occurring is based on the ignition probability and the probability of flammable dust clouds arising. While all possible ignition sources are reviewed, the most important ones include open flames, mechanical sparks, hot surfaces, electric equipment, smoldering combustion (self-ignition) and electrostatic sparks and discharges. Apart from the machinery, the ignitibility and explosibility of the dust will also play an important role.

The consequences of dust explosions are described as consequences for personnel and consequences for equipment. The method reviews the consequences of both primary and secondary events. Factors determining the consequences of dust explosions include the how frequently personnel are present, the equipment strength, housekeeping and implemented consequence-reducing measures. Both the likelihood of dust explosions and consequences are described by classes ranging from low probabilities and limited local damage, to high probability of occurrence and catastrophic damage. Acceptance criteria are based on the likelihood and consequence of the events.

The method has been applied to a milk powder production facility and a metal alloy crushing and sieving facility. After an initial risk evaluation, preventive and protective measures were proposed both individually and in combination for the two facilities. The impact that these measures have on the risk was also evaluated. The two applications demonstrate the strength of the method and, in fact, demonstrate the support it offers to the user for choosing the appropriate risk mitigating measures.