Risk assessment and protective measures required for the prevention of dust explosions arising through the silaging and subsequent processing of crystallized sugar

Status:

completed 12/1995

Aims:

Following manufacture, sugar is stored in silos and/or transferred to downstream processes in member companies of the Institution for Statutory Accident Insurance and Prevention in the Sugar Industry. A mixture of finely powdered sugar and air is capable of dust explosion. The formation of explosive dust/air mixtures must therefore be anticipated when sugar is handled. The Institution for Statutory Accident Insurance and Prevention in the Sugar Industry has already drawn up provisions for the avoidance of dust explosion hazards in the past for the whole area of storage and further processing. The objective of this project was the creation of a risk analysis to permit adaptation of explosion protection in this area to the state of the art if required. This necessitated definition of the combustion and explosion characteristics of the sugar dusts in question, estimation of the likelihood of incidence of both hazardous explosive dust/air mixtures and effective sources of ignition, and proposal of suitable protective measures.

Activities/Methods:

The combustion and explosion characteristics of the sugar fractions in question required for hazard evaluation and risk assessment are defined in accordance with the procedure described in VDI 2263, Page 1. Conclusions are to be drawn on the probability of hazardous explosive atmospheres (dust/air mixtures) arising in various parts of a plant, in consideration of the apparatus and procedures employed in each case. Dust concentration measurements were also performed in crystallized sugar silos for this purpose. The influence of various conveyor processes upon the grain size distribution of crystallized sugar (fragmentation) and upon the formation of dust clouds in silos was studied. Finally, measures were defined, in consideration of the apparatus and procedures employed in the case in question (both in existing and planned plants), for the avoidance of explosions (preventive explosion protection) and, where necessary, for limitation of the effects of explosions (engineered explosion protection)

Results:

The project involved inspection of company premises, studies into the combustion and explosion characteristics of sugar dusts, and concentration measurements in dust-handling plants. The results show that insufficient attention has been paid to the dust explosion hazard in some areas. The results of the hazard assessment and the risk analysis and the recommendations derived from them for the required and possible protective measures were discussed by a working group during the course of the project and incorporated into a catalogue of decisions and measures entitled "protective measures for the avoidance of sugar dust explosions". The catalogue is distributed by the Institution for Statutory Accident Insurance and Prevention in the Sugar Industry to the member companies concerned.

Publications:

Entscheidungs- und Maßnahmenkatalog "Schutzmaßnahmen zur Vermeidung von Zuckerstaubexposionen". Hrsg.: Zucker- Berufsgenossenschaft, Mainz 1999

Further informations:

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