Effects of dietary n-3 polyunsaturated fatty acids and ... - FINS

1 st WorkshopXIII International Feed Technology Symposium3 %. Up to 80 % consist of organic grain content [3]. Dusts are defined to be solidparticles with particle sizes of 1 – 500 µm in gases which sediment caused by their ownweight. However, they remain as air-dust mix in the atmosphere for some time [4, 5, 6].Explosive areas are characterised by dust concentrations within the lower explosion limit– for grain and feed dusts respectively > 30 g/m³ – and the upper explosion limit(normally 2 – 4 kg/m³).For avoiding cases of damage as a result of dust explosions, operators of plants in whichexplosive dust-air mixes can occur are obligated to implement the contents of ATEXDirective 1999/92/EC and the national legislation respectively. If there are any areas at aplant where the occurrence of explosive dust-air mixes cannot be excluded, a systematicassessment of explosion risks must be carried out. The assessment of explosions risksinitially focuses on:likelihood that explosive atmosphere will occur and their persistence,likelihood that ignition sources, including electrostatic discharge will be presentand become active and effective,the scale of the anticipated effects.Adequate measures must be taken to attain the aims of the Directive [1].The generation of explosive atmosphere has to be prevented with priority, for exampleby replacing explosive materials or applying inerting measures. If this is not reliablypossible the risk of an explosion has to be minimised by absence of ignition sources aswell as further technological measures for explosion protection [1].At the processing of grain to feed and food, an avoidance or prevention of the generationof explosive dust-air atmosphere is possible with limits only. Therefore the likelihood oftheir occurrence has to be evaluated as basis for protection measures meeting therequirements.In accordance with the Directive 1999/92/EC a classification to zones of places whereexplosive atmosphere may occur has to be carried as following:Zone 20 a place in which an explosive atmosphere in form of a cloud ofcombustible dust in air is present continuously, or for long periods,Zone 21 a place in which an explosive atmosphere in form of a cloud ofcombustible dust in air is likely to occur in normal operation occasionally andZone 22 a place in which an explosive atmosphere in form of a cloud ofcombustible dust in air is not likely to occur in normal operation but, if it doesoccur, will persist for a short period only.If the occurrence of hazardous explosive atmosphere can be reliably excluded for aplace, so this is free of zones [1].On the basis of classification of zones, the requirements for equipment have to befulfilled according to the prescriptions of the ATEX Directive 94/9/EC [2]. Inaccordance with the three zones, three device categories are defined which aresubdivided according to the relevant ignition-source reliability or absence:Category 1: Ignition sources are avoided by two independent protectionmeasures or safety despite two independent errors also at rare breakdowns14