Text version of the page

15 Classification According to Housekeeping of Working Place

Table8: Housekeeping and Explosion Hazard Level of Thickness ofDuration of PresenceFire or HousekeepingDust Layerof a Dust LayerExplosion Riskgoodzero ornot presentnonenegligible fairnot negligibleshorter than thenonelength of 1 shiftpoor not negligiblelonger than the fire hazard and length of 1 shiftZone 22 if cloudsare created

High cleanliness of working area is very importantin dust explosion protection, as in contrast to gasesa series of releases that are individually under the explosion limit can lead to a hazardous accumulation of dust (see also 4.1,Preventive (Primary) Explosion Protection).The Directive 99/92/EC and specially the Guide ofthis Directive, paragraph 3.1.4.1 refer to obligatory cleanliness standards.In the new version of the Standard “Classificationof areas where combustibledustsareormay be present” accordingto IEC 61241-10and EN 50281-3, the degree of housekeeping is quantified and included in the classification of the areas (Table8).

Figure6: Example of the Classification into Dust Explosion Hazardous Areas According to IEC 61241-10

The basics of dust-explosion protection - 9224 222120

Zone 20Inside the hopper of a bag emptying stationZone 21Immediate surround-ings (radius of 1m) around the manholeZone 22Area outside Zone 21due to accumulatios of dust R.STAHL Explosion protection