P&K 3783Dispersion areas types I-XXVDispersion areasIndex Dispersion area types I to V Dispersion area types VI to IX Dispersion area types X to XVIII Dispersion area types X to XII Dispersion area types XIII to XV Dispersion area types XVI to XVIII Dispersion area types XIX to XXI Area maps for types XXIII to XXV Table of input data for instantaneous release Dispersion area types I to VDispersion area type IThis type of dispersion area can be used for accidental releases in flat terrain without obstacles. Furthermore, it can replace all the dispersion areas with obstacles which lead to a reduction of the concentration if no special diagrams are available. Dispersion area type IIThis type of dispersion area can be used for accidental releases in which the dispersion is limited by an obstacle to a hemisphere. The obstacle can consist of a row of buildings, a dam, a dock or similar objects near the source. This type of dispersion area may also be used for shorter obstacles or other heights at larger distances, if no other special diagrams are available. If the distance of the obstacle amounts to more than 5 Lei (for instantaneous release) or 30 Lee (for continuous release), the effect of the obstacle on the heavy gas dispersion can be disregarded. Dispersion area type IIIThis type of dispersion area can be used for accidental releases for which the dispersion is limited by an uninterrupted canyon of orthogonal walls which is parallel to the wind. This type of dispersion area can also be used for canyons of other geometries if no other special diagrams are available therefore. Deeper canyons lead to similar concentrations. For lower, broader or interrupted canyons, it will yield conservative estimations. For single, interrupted buildings, the (*UZD) lower flammability distances are considerably overestimated if the diagram of dispersion area type III is used. Dispersion area type IVFor this type of dispersion area, a hemispherical, impermeable protective wall is located at such a distance leeward of the source that a distinct protection is obtained for those locations which are situated beyond the wall. On the bases of the results, the potential protection effect of such a measure can be estimated. Dispersion area type VIn contrast to dispersion area type IV, the protective wall is placed nearer to the source for this type of dispersion area, and the protecting effect decreases. Area maps for types I to VArea map for dispersion area type IFlat terrain without obstacles. ![]() Area map for dispersion area type IIFlat terrain. This dispersion is limited to a hemisphere by a wall located near the source and parallel to the wind (Fig. 2). The wall is located at a distance of 1 Lei (for instantaneous release) or 5.6 Lee (for continuous release) from the gas source. The wall is to be regarded as infinitely long and, during the heavy gas spread phase, as infinitely high (1Lei or 5.6 Lee). ![]() Area map for dispersion area type IIIFlat terrain. This dispersion takes place in a canyon of orthogonal walls. This canyon has a height of 1 Lei (for instantaneous release) or 7 Lee (for continuous release), and a breadth of 2 Lei or 28 Lee, respectively. ![]() Area map for dispersion area type IVFlat terrain. Semi-circular, massive wall leeward of the source. The height of the wall is 0.4 Lei (for instantaneous release) or 2.24 Lee (for continuous release). The distance between the source and the obstacle amounts to 4 Lei or 22.4 Lee, respectively. ![]() Area map for dispersion area type VFlat terrain. Semi-circular, massive wall leeward of the source. The height of the wall is 0.4 Lei (for instantaneous release) or 2.24 Lee (for continuous release). The distance between the source and the obstacle amounts to 2.5 Lei or 14 Lee, respectively. ![]() Dispersion area types VI to IXDispersion area type VIIn this dispersion area the wall, already used in dispersion area V, was placed in winward of the source. In contrast with the wall leeward of the source, in the dispersion area V no distinct protection is visible. The concentrations, however, are below those concentrations measured in the area without obstacles. As a reason for this, the shade of the area near the source is to be mentioned. This causes a stronger lateral dispersion of the gas cloud. Dispersion area type VIIThe wall used in this dispersion area corresponds to the obstacle used in the dispersion area IV. Just as in the dispersion area VI, the wall was placed here winward of the source. Although the concentrations are lower here than in the dispersion area without obstacles, not a significant protection is obtained by this obstacle. Dispersion area type VIIIThe obstacle in this dispersion area is in principle a combination of the obstacles used in the dispersion area types V and VI. The circular, impermeable protective wall with the source in the center used here, shows a great distinctive protection for all the locations situated downstream of the source leeward of the protection wall. The position of the protective wall is clearly the cause of the strong concentration gradient. As on the basis of the shade within the protective wall, the gas can spread stronger laterally than in the dispersion area type V, the concentration in the dispersion area VII is generally lower than in the dispersion area type V. Dispersion area type IXThe circular, impermeable protective wall in this dispersion area corresponds to a combination of the obstacles in the dispersion area IV an VII. Also, as in the dispersion area type VIII, a great distinct protection for locations situated downstream of the source leeward of the protection wall is visible. Area maps for types VI to IXArea map for dispersion area type VIFlat terrain. Semi-circular, massive wall windward of the source. The height of the wall is 0.4 Lei (for instantaneous release) or 2.24 Lee (for continuous release). The distance between the source and the obstacle amounts to 2.5 Lei or 14 Lcc, respectively. ![]() Area map for dispersion area type VIIFlat terrain. Hemispherical, massive wall in luv of the source. The height of the wall is 0.4 Lei (for instantaneous release) or 2.24 Lee (for continuous release). The distance between the obstacle and the source amounts to 4Lei or 22.4 Lcc, respectively. ![]() Area map for dispersion area type VIIIFlat terrain. Circular, massive wall around the source. The height of the wall is 0.4 Lei (for instantaneous release) or 2.24 Lee (for continuous release). The distance between the source and the obstacle (radius of the obstacle) amounts to 2.5 Lei or 14 Lcc, respectively. ![]() Area map for dispersion area type IXFlat terrain. Circular, massive wall around the source. The height of the wall is 0,4 Lei (for instantaneous release) or 2,24 Lee (for continuous release). The distance between the source and the obstacle (radius of the obstacle) amounts to 4 Lei or 22,4 Lcc, respectively. ![]() Dispersion area types X to XVIIIThe dispersion area types X to XVIII can be used for accidental releases in which the dispersion is limited by an interrupted canyon of orthogonal walls which is parallel to the wind. Dispersion area types X to XIIIn case of an instantaneous release the measured mean UZD are generally lower in these dispersion areas than the UZD measured in an uninterrupted canyon (dispersion area type III). In the dispersion area type X (in continuous release) after 50 Lee distance from the source, lower UZD than in the dispersion area type III are visible, while the UZD in the dispersion area types XI and XII are generally lower than the values measured in the dispersion area type III. As it is evident from the concentration courses, a widening of the canyon and the building gaps leads to a reduction of the UZD values. Area maps for types X to XIIArea map for dispersion area type XFlat terrain. The dispersion takes place within a canyon of orthogonal walls interrupted by lateral gaps. It is 1.5 Lei (for instantaneous release) or 11 Lee (for continuous release) high and 2 Lei or 14 Lee wide. ![]() Area map for dispersion area type XIFlat terrain. The dispersion takes place within a canyon of orthogonal walls interrupted by lateral gaps. It is 1.5 Lei (for instantaneous release) or 11 Lee (for continuous release) high and 3 Lei or 21 Lee wide. ![]() Area map for dispersion area type XIIFlat terrain. The dispersion takes place within a canyon of orthogonal walls interrupted by lateral gaps. It is 1.5 Lei (for instantaneous release) or 11 Lee (for continuous release) high and 4 Lei or 28 Lee wide. ![]() Dispersion area types XIII to XVThis dispersion area types can be used in principle for the same canyons as the dispersion area types X, XI and XXII, though with a source of different location. As well as in the area types X to XII, a widening of the canyon and the building gaps lead to a reduction of the UZD values. In case of an instantaneous release the mean UZD values of the area types XIII to XV are generally lower than the UZD measured in the dispersion area type III. In the dispersion area types XIII, XIV and XV (in instantaneous release) the mean concentration values after a source distance of a maximum of15 to 20 Lei are already lower than in an area without obstacles. In case of a continuous release, the measured mean UZD values in the range of 50 to 200 Lee in the area types XIII to XV drop below the values measured in the area type III. However, during the entire heavy gas spread phase, those values are greater than the values measured in the area without obstacles. Area maps for types XIII to XVArea map for dispersion area type XIIIFlat terrain. The dispersion takes place in a canyon of orthogonal walls interrupted by lateral gaps. It is 1.5 Lei (for instantaneous release) or 11 Lee (for continuous release) high and 2 Lei or 14 Lee wide. ![]() Area map for dispersion area type XIVFlat terrain. The dispersion takes place within a canyon of orthogonal walls interrupted by lateral gaps. It is 1.5 Lei (for instantaneous release) or 11 Lee (for continuous release) high and 3 Lei or 21 Lee wide. ![]() Area map for dispersion area type XVFlat terrain. The dispersion takes place within a canyon of orthogonal wall interrupted by lateral gaps . It is 1.5 Lei (for instantaneous release) or 11 Lee (for continuous release) high and 4 Lei or 28 Lee wide. ![]() Dispersion area types XVI to XVIIIThese dispersion areas can be used in principle for the same canyons as the dispersion area types X, XI and XII. However, the location of the source is moved upstream to the beginning of the building gap. A widening of the canyon and the building gaps leads to a reduction of the UZD values. In instantaneous releases as well as in continuous releases, the mean UZD values measured in these areas are generally lower than the values measured in the dispersion area type III. In the dispersion area types XVI and XIII in instantaneous release, the mean UZD values are generally lower when there are no obstacles. This is also valid in case of continuous release for the dispersion area type XIII. Area maps for types XVI to XVIIIArea map for dispersion area type XVIFlat terrain. The dispersion takes place within a canyon of orthogonal walls interrupted by lateral gaps. It is 1.5 Lei (for instantaneous release) or 11 Lee (for continuous release) high and 2 Lei or 14 Lee wide. ![]() Area map for dispersion area type XVIIFlat terrain. The dispersion takes place within a canyon of orthogonal walls interrupted by lateral gaps. It is 1.5 Lei (for instantaneous release) or 11 Lee (for continuous release) high and 3 Lei or 21 Lee wide. ![]() Area map for dispersion area type XVIIIFlat terrain. The dispersion takes place within a canyon of orthogonal walls interrupted by lateral gaps. It is 1,5 Lei (for instantaneous release) or 11 Lee (for continuous release) high and 4 Lei or 21 Lee wide. ![]() Dispersion area types XIX to XXIThe dispersion area types XIX to XXI can be used for accidental releases, in which the dispersion takes place within an area of interrupted uniform buildings. In instantaneous as well as in continuous release, the mean UZD values measured in these dispersion area types are lower than the values measured in the area without obstacles (area type I). The greater dilution is traced back to the greater mixing with ambient air caused by the buildings. Area maps for types XIX to XXIIArea map for dispersion area type XIXFlat terrain. The dispersion takes place within an area of uniform buildings. The height of the buildings is 1 Lei (for instantaneous release) or 11 Lee (for continuous release). The lateral measurements of the buildings elements amount to 1 Lei or 11 Lee. The distance from each other is 2 Lei or 21 Lee, respectively. ![]() Area map for dispersion area type XXFlat terrain. The dispersion takes place within an area of uniform buildings. The height of the buildings is 1 Lei (for instantaneous release) or 11 Lee (for continuous release). The lateral measurements of the buildings elements amount to 1 Lei or 11 Lee. The distance from each other is 2,5 Lei or 27 Lee, respectively. ![]() Area map for dispersion areas type XXI and XXIIFlat terrain. The dispersion takes place within an area of uniform buildings. The height of the buildings is 1 Lei (for instantaneous release) or 11 Lee (for continuous release). The lateral measurements of the buildings elements amount to 1 Lei or 11 Lee. The distance from each other is 3 Lei or 32 Lee, respectively. XXI![]() XXII![]() Area maps for types XXIII to XVArea map for dispersion area type XXIIIFlat terrain. The dispersion takes place within an area of uniform buildings. The height of the buildings is 1 Lei (for instantaneous release) or 11 Lee (for continuous release). The lateral measurements of the buildings elements amount to 1 Lei or 11 Lee. The distance from each other is 5 Lei or 53 Lee, respectively. ![]() Area map for dispersion area type XXIVFlat terrain. The dispersion takes place within an area of uniform buildings. The height of the buildings is 2 Lei (for instantaneous release) or 21 Lee (for continuous release). The lateral measurements of the buildings elements amount to 1 Lei or 11 Lee. The distance from each other is 3 Lei or 32 Lee, respectively. ![]() Area map for dispersion area type XXVFlat terrain. The dispersion takes places within an area of uniform buildings. The height of the buildings is 2 Lei (for instantaneous release) or 21 Lee (for continuous release). The lateral measurements of the building elements amount to 1 Lei or 11 Lee. The distance from each other is 4 Lei or 43 Lee, respectively. ![]() Definition of the input data for instantaneous release for the numerical model in Guideline VDI 3783 Part 1
Definition of the input data for continuous release for the numerical model in Guideline VDI 3783 Part 1
* UZD (untere Zünddistanz) = lower flammability distance | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||