PK_3783

Preliminary Note

Extract of VDI 3783 published by

VEREIN DEUTSCHER INGENIEURE

Dispersion of Pollutants in the Atmosphere
Dispersion of (Heavy Gas) Emissions by Accidental Releases - Safety Studies

Preliminary Note


Extract of VDI 3783 Part 1 Dispersion of Emissions by Accidental Releases - Safety Study

This guideline presents a computation method to estimate the dispersion of emissions by accidental releases on the basis of the Gaussian dispersion equation; this method is part of the safety study according to the administrative regulation for the ordinance of industrial accidents [1]. Thereby the meteorological input parameters have been selected such that a mean dispersion situation as well as the worst possible dispersion within the frame of this model are covered. This means that the computation method must not be used for calculating acute industrial accidents or for reconstructing suspected ones.

Specifications on the type and the spatial as well as temporal course of the pollutant release, danger areas, damages and possible effects are not dealt with in this guideline.

The second general administrative regulation for the ordinance on industrial accidents [1] prescribes specific data on the effects of industrial accidents (Paragraph 3.2.7). The following quotation of the second administrative regulation [1] contains terms which are printed in italics; these terms represent either input parameters for the calculation or the results of the calculation.

The data of the effects of the industrial accidents, "should, as far as they are not descriptive in nature, be expressed in numerical values; they must be made plausible (e.g. by calculations, estimations, or from experience). Assumptions which are made in this connection must be substantiated; in the case of estimations on the basis of models, the assumptions and presuppositions under which the result have been determined must be specified. Depending on the type of substance, the following data are needed:

a) Data on the release of material or energy, such as

  • type, quantity, and state of the pollutant,
  • effects of the pollutant released, as far as they are known (short-term, medium-term, long-term effects; acute toxicity, chronic toxicity),
  • site of release (e.g. part of the plant, height above ground),
  • duration of the release.

b) Data on the dispersion, such as

  • type and path of dispersion, especially material transport (plume, cloud, flow of liquid), energy transport (blast wave, heat radiation),
  • operational and accidental boundary conditions (thermal buoyancy, turbulence),
  • buildings in the vicinity (type, heigth, size of buildings)
  • orography of the surrounding area (rising grounds, vegetation, streams, lakes, etc.),
  • other obstacles (type, height, size),
  • chemical and physical transformations (chemical reaction, condensation, sorption).

c) Data on the effects, such as

  • type and temporal course of the pollutant concentration (atmosphere, soil of waters, precipitation), in the case of airborne emission for the worst and the mean weather situation1), as well as pressure and temperature, ...".

Extract of VDI 3783 Part 2 - Dispersion of Heavy Gas Emissions by Accidental Releases - Safety Note

The ordinate of industrial accidents [2] issued by the Federal Government on the basis of the Federal Ambient Air Control Act [1] aims at protecting the population from public danger which may be caused by operation failures in plants requiring licenses. Apart from other safety duties which have been established for the avoidance of accidental releases, the operator of a plant is obliged to carry out a safety study which must be in correspondence with the requirements given in the second general administrative regulation for the ordinance on industrial accidents [3]. Among others, the safety study must contain data on the effects of industrial accidents which are described in the following quotation taken from the second administrative regulation for the ordinance on industrial accidents (No. 3.2.7):

The data of the effects of the industrial accidents, "should, as far as they are not descriptive in nature, be expressed in numerical values; they must be made plausible (e.g. by calculations, estimations, or from experience). Assumptions which are made in this connection must be substantiated; in the case of estimations on the basis of models, the assumptions and presuppositions under which the result have been determined must be specified. Depending on the type of substance, the following data are needed:

a) Data on the release of material or energy, such as

  • type, quantity, and state of the pollutant,
  • effects of the pollutant released, as far as they are known (short-term, medium-term, long-term effects; acute toxicity, chronic toxicity),
  • site of release (e.g. part of the plant, height above ground),
  • duration of the release.

b) Data on the dispersion, such as

  • type and path of dispersion, especially material transport (plume, cloud, flow of liquid), energy transport (blast wave, heat radiation),
  • operational and accidental boundary conditions (thermal buoyancy, turbulence),
  • buildings in the vicinity (type, heigth, size of buildings)
  • orography of the surrounding area (rising grounds, vegetation, streams, lakes, etc.),
  • other obstacles (type, height, size),
  • chemical and physical transformations (chemical reaction, condensation, sorption).

c) Data on the effects, such as

  • type and temporal course of the pollutant concentration (atmosphere, soil of waters, precipitation), in the case of airborne emission for the worst and the mean weather situation1), as well as pressure and temperature, ...".

In the Guideline VDI 3783 Part 1 [4] which has been passed in 1987, a calculation method for the dispersion of emissions by accidental releases within the range of the safety study for buoyancy-influenced and density-neutral gases has been given. The present Part 2 of this Guideline aims at filling in the gap of heavy gases.


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