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Modelování a hodnocení mimořádné události v průmyslovém podniku s využitím multikriteriální analýzy
Petra Suchardová1, Oldřich Sucharda2
1 VŠB – Technical University of Ostrava, Faculty of Safety Engineering, email@example.com
2 VŠB – Technical University of Ostrava, Faculty of Civil Engineering, firstname.lastname@example.org
The submitted paper applies theoretical approaches for the modelling of the extraordinary events such as the fire and explosion’s creation to a practical case study in the industrial area where it models the potential release of the dangerous chemical substances from a device. For targets of this article the release of the gas from the pipeline is modelled, and there are assessed the consequences after the release on the surrounding buildings where are the employees of the company, by means of the multi – criteria analysis.
Keywords: multi – criteria analysis, gas, threat zone
Předkládaný příspěvek aplikuje teoretické přístupy k modelování mimořádných událostí jako je vznik požáru a výbuchu do praktické případové studie v průmyslovém areálu, kdy modeluje potenciální únik nebezpečných látek ze zařízení. Pro účely článku je simulován únik plynu z potrubí, kde jsou hodnoceny následky po tomto úniku na okolní budovy, kde se vyskytují zaměstnanci podniku, pomocí multi – kriteriální analýzy.
Klíčová slova: multikriteriální analýza, plyn, zóna ohrožení
In compliance with a development of technological and technical devices also an amount of dangerous chemical substances and chemical agents increases. These are used in technologies, warehouses, in a transport between the industrial companies. Due to the fact that a lot of accidents from a historical point of view happened, many enterprises have an interest to increase a level of safety within a handling, storage and transport of the chemical substances .
Generally due to consequences of major accidents caused by failures in technological devices, pipelines, and warehouses, it is necessary and important to manage all safety risks which can have a serious impact and caused the following :
As per the national legislations, the employers have to prevent the risks and remove them or minimize the residual risks .
The goal of the paper is to assess the real case study in the industrial company connected with the storage and the transport of the chemical substances and the chemical agents. In the company there is considered and chosen a critical area with a big movement of internal end external employees.
As the chosen area, the article focuses on the gases transport in the production cycle. The company products by own technologies, uses, stores, transports the waste metallurgical gases like blast furnace gas, coking gas, mixed gas and the technical gases like acetylene, oxygen and nitrogen.
The evaluation of the risk which results from the extraordinary accident is calculated by means of multi – criteria analysis. This analysis can be divided into particular steps. The procedure of it is described below:
In the article there are used the methods of risk management. These, which are considered here for the modelling of the extraordinary releases, are in the following Table 1.
|Type of substance behaviour||Applicable model|
|Dispersion of gases||Gaussian model|
|Jet fire||Chamberlain model|
|Vapour cloud explosion||Multienergy model|
Table 1 List of models used within extraordinary accident’ simulation 
The models are not described in detail due to the length of the paper. These are described in the [2, 6].
The following Figure 1 reflects a situation in the company which is chosen for the modelling of the extraordinary situations. In the figure, there is a particular place in the company where two buildings are situated, the Storage of the engines and the Maintenance of the blast furnaces. The yellow line represents natural gas, the green line acetylene and the blue line coking gas. The distance between the Maintenance of the blast furnaces and the pipeline of natural gas is 0.5 m and the distance between the Storage of the engines and the pipelines of acetylene and coking gas is 15 m.
The Maintenance of blast furnace is operated in the continuous running system and in every shift there are 10 employees. Maximum two employees are in the building where the engines are stored. The operation mode is as necessary here.
Figure 1: Real situation in company for purposes of modelling 
The first and the second step of the multi – criteria analysis are not considered in the paper because of its length. The content of the first step is to determine the coefficients of the particular factors. This results from the company strategy and from the implementation of the Enterprise risk management. The determination and the description of the coefficients for this type of the industrial company are included in  and it results from the procedure in . The total average coefficient (T.A..C.) is 17,5. The detailed description of the factors is included in Table 8 below.
This chapter deals with the third step of the multi – criteria analysis.
After the assessment of the particular technological devices with a higher probability of risk, the system of pipelines which transports natural gas in the closed-off circle is chosen here.
The case study is elaborated under the real outside conditions.
The mentioned natural gas entails a certain level of risk for other technologies which arises from its physical-chemical properties and technical safety parameters. The properties of the natural gas which have an important influence in terms of loss prevention are shown in Table 2. Input data on the system of the pipeline are shown in Table 3.
|Gas||Compounds||Dangerous properties||LEL[%]||UEL[%]||Heating value[kJ.m-3]|
|Natural gas||CO2, CH4, N2||F+||5||14.9||34158|
Table 2 Physical-chemical properties, technical safety parameters 
|Natural gas||6 km||DN 50||5 bar||20 °C|
Table 3 Input data for computational simulations
The risk assessment is carried out using two programs, ALOHA and EFFECTSGIS, which are especially designed for use by people responding to the chemical releases, as well as for the emergency planning and the training [3, 8]. The programs model the key hazards such as the toxicity, the flammability, the thermal radiation and the overpressure related to the chemical releases that result in the toxic gas dispersions, the fires or the explosions.
The program ALOHA implements models described in  where uses the toxic gas dispersion, the fires and the explosions. The program employs several different models, including an air dispersion model that it uses to estimate the movement and dispersion of chemical gas clouds. The program is able to estimate the toxic gas dispersion, the overpressure values from a vapour cloud explosion, or the flammable areas of a vapour cloud.
The program EFFECTSGIS performs calculations to predict the physical effects such as the gas concentrations, the heat radiation levels, the peak overpressures of the escape of the hazardous materials. Models are based upon the . It can also model the complex releases by linking individual models in such a way that they describe all physical phenomena that may occur during that release .
The particular scenarios were stipulated by the expert. The scenarios are carried out within the different conditions. The weather conditions are taken as the average in the location. An important circumstance in the accident simulation is the definition of the wind speed which is within the range of 1,7 and 5 m.s-1 and north – east direction, the atmospheric stability covers the interval D to F, and the ambient air temperature is 20 ^(o)C. No inversion is considered. The gas pipeline is considered with its parameters.
Gaussian model, Chamberlain model and Multienergy model are used within the conditions of catastrophic and continuous releases. The list of simulated scenarios is included in the table 4. Scenarios with A are calculated in program ALOHA and with B in program EFFECTSGIS.
|Scenario no.||Wind speed||Stability class||Situation||Model||Type of release|
|1A.||5 m.s-1||D||Release without ignition||Gaussian model||Catastrophic|
|2A.||5 m.s-1||D||Release with ignition||Chamberlain model||Catastrophic|
|4A.||5 m.s-1||D||2 cm hole|
|5A.||1.7 m.s-1||F||2 cm hole|
|1B.||5 m.s-1||D||Release with ignition||Chamberlain model||Catastrophic|
|2B.||5 m.s-1||D||Release with ignition||Chamberlain model||2 cm hole|
|3B.||5 m.s-1||D||Release with creation of explosive mixture||Multi energy explosion model||Catastrophic|
Table 4 List of scenarios
For the chosen scenarios there are shown the results below after the computational simulations of explosions and fires. The tables 5, 6 and 7 show the results.
|Scenario no.||Max flame length (burn duration 1 hour)||Max burn rate||Total amount burned/ released||Release rate||Fatal zone||Threat at evaluated point (in 0,5 m in west, 2 m in north)|
|1A.||-||-||31.5 kg||2.5 kg. min-1||< 10 m||insignificant|
|2A.||4 m||82.8 kg.min-1||31.5 kg||-||10 m||5.18 kW.m-2|
|3A.||4 m||82.8 kg.min-1||31.5 kg||-||10 m||4.48 kW.m-2|
|4A.||2 m||13.2 kg.min-1||31.5 kg||-||< 10 m||8.1 kW.m-2|
|5A.||2 m||13.2 kg.min-1||31.5 kg||-||< 10 m||10.3 kW.m-2|
Table 5 List of results after modelling in ALOHA
|Scenario no.||Average mass flow rate (in 40 s)||Heat radiation||Length of frustum||Mortality||Safe distance||View factor|
|1B.||0.12 kg.s-1||21.65 kW.m-2||12.58 m||64 %||23.8 m||27 %|
|2B.||0.05 kg.s-1||0.13 kW.m-2||2.49 m||0 %||3.9 m||0,2 %|
Table 6 List of results after modelling in EFFECTSGIS
|Scenario no.||Peak overpressure||Positive phase duration||Damages||Damages to brick houses||Damages to structures|
|3B.||0.081 Bar||33 ms||Minor||habitable after repairs||minor|
Table 7 List of results after modelling in EFFECTSGIS
Figures 2 and 3 show the fatal zone, the zone of second degree burns and the zone of pain including the threat at point of 0,5 m on the west and 2 m on the north from the puncture in the pipeline, within the catastrophic releasing as it considered in the scenario no. 2A.
Figure 2: Threat zones within catastrophic natural gas releasing (scenario no. 2A)
Figure 3: Threat at evaluated point (scenario no. 2A)
The fourth step of the multi – criteria analysis is the evaluation of the factors by the gas pipeline with the natural gas carried out by the team of the experts. This step results from the modelling of the scenarios. Results from that are usable for the purposes of the risk analysis and the emergency planning. Results are placed to the particular factors. These are described below.
The table 8 shows the separate evaluated factors with the coefficient, the evaluated aspects and the scale. The scale presented here is considered from FERMA standard . This represents a possible approach of the risk management which uses the terminology for risk set out by the International Organization for Standardization in its recent document ISO/IEC Guide 73 for use in standards. The scale is transferred to the numerical one where 0 means no risk value, 1 means very low and 5 means very high. The other values in the scale are being interpolated.
|T.A.C||Evaluated factor||Evaluated aspect||Property of factor||Scale|
|5||Human factor||Fatal zone, heat radiation, pressure zones, flame length, toxicity||Comprises the fatal, serious and other injuries||very low|
|2,5||Environment||Heat radiation, toxicity||Comprises the consequences on surrounding environment including water, costs for recultivation of land.||very low|
|3||Building structures||Heat radiation, peak overpressure, positive phase duration||Comprises damages on buildings, costs for the restoration||very low|
|4||Technical infrastructure||Heat radiation, peak overpressure, positive phase duration||Comprises possible damages on the surrounding infrastructures, following technological process breakdowns are considered||very low|
|3||Technology||Heat radiation, peak overpressure, positive phase duration||Comprises damages on particular technologies, cost of the technology||very low|
Table 8 Risk factors and their properties 
The table 9 shows the calculation of the element risk factor. The experts assessed the consequences of the scenarios shown in chapter 5 including the real conditions in the company such as the number of the employees, importance of the technical infrastructure and the buildings as it results from the evaluated factors.
|Factors||Evaluation of experts||Total evaluation||T. A. C.||Element risk factor|
|Expert 1||Expert 2|
Table 9 Evaluation of risk in the case study
The element risk factor is 39,5. The total risk factor is calculated by division of element risk factor by total average coefficient, i.e. 39,5 / 17, 5 = 2,26.
In the case study the risk factor of the extraordinary accident is 2,26. The risk is low – middle.
The obtained risk factor of this extraordinary accident will be used for the evaluation of the total vulnerability of the considered company together with the other risks (the financial, the operational and the hazard risks).
Nowadays, the risk management is one of the most important elements of the modern company strategy. The enterprise risk management should comprise all spheres which influence the company (internal and external factors). The evaluated spheres can be for instance the financial, the strategic, the operational and the hazard risks. The important factor by the risk management is the release of the dangerous chemical substances in the industrial enterprises. The biggest force of this hazard can be found in the chemical, the metallurgical and the similar industries.
The paper deals with the evaluation and the determination of the risk factor of the release of the dangerous chemical substance. For the evaluation, the multi – criteria with the coefficients is used here.
The part of the risk management is carrying out of the countermeasures and thereby the elimination of the risk. The obtained results can be used for the emergency planning, as the important circumstance for the industrial insurance (strategic management, the cooperation of the top management and the consultant companies of the insurances companies).
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