FAULT TREE ANALYSIS - FTA
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EVENT TREE ANALYSIS -ETA
 
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The aim of the Seveso III/COMAH Regulations is to both prevent major accidents involving hazardous substances in the workplace and limit the consequences of such accidents on people and the environment. There are legally binding requirements for all businesses affected by the regulation.

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In order to prevent hazards, a process Safety Management System (MS) is established to prevent, control and reduce the effects of major accidents. If the facility is a high-level establishment; The organization must prepare a safety report, major accident scenario document and emergency plan. If it is a lower level organization; The organization must prepare a major accident scenario policy and major accident scenario document. These plans are to mitigate the effects of a major accident.

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Creating Scenarios:

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General data of similar facilities, Process Hazard Analysis techniques and Event tree analysis, Fault tree analysis, Hazard and operability analysis are used to define major accident scenarios. The results of other risk analyzes and experience gained from the analysis of accidents involving hazardous substances are also taken into account. Based on the main parameters that define the possible consequences of malfunctions, the root causes of accident scenarios that are likely to occur under normal operating conditions, are credible, and can lead to the worst consequences are determined.

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Major accident scenarios are created on each dangerous equipment. The created scenarios are defined and described. The major accident scenario is created starting from the root causes determined according to the detected hazards, including all possible spread, fire or explosion events. In scenarios to be created using a single root cause and effect pair, each of the possible spread, fire and explosion events are taken into account.

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IEC 61025 - Fault Tree Analysis (FTA)

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Fault tree analysis analyzes the errors that pose a danger at each level and shows, through a logic diagram, all possible combinations of errors and problems that create the greatest loss. In FTA, by going down to the root cause of the undesirable event, other possible undesirable errors and their causes are revealed.

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Event Tree Analysis (ETA)

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Event tree is a quantitative technique that involves  inductive analysis of systems. An event tree consists of a chain of sequential events that form the starting event or peak event that occurs as a result of various reasons and the independent events that follow it. The analysis begins with examining the initial event, that is, the cause of the system error, and then continues by tracing the error chains that occur depending on whether the subsystems or components are faulty or faulty.

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Calculation of Frequency:

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The created scenarios are analyzed with methods that can produce results suitable for comparison with the limit value of the major industrial accident frequency in Article 9 of the Regulation, and the frequency of occurrence of major industrial accidents is calculated.

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Safety measures such as ethics, availability and understanding of information, certification, procedures, plans, instructions, periodic tests and controls, maintenance, communication and signs cannot be directly used in calculating the occurrence frequencies of selected major accident scenarios.

In calculating the frequency of occurrence of scenarios, the principle of independence, the effect of common cause errors and the principle of effectiveness are also taken into account.

Deciding and Implementing Measures:

In case the frequency of occurrence of each major industrial accident scenario is greater than the limit value of the major industrial accident frequency, the necessary measures are decided and these measures are implemented.

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Within the scope of SEVESO Directive;

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We work at your workplace with our expert staff for Quantitative Risk Assessment service.

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Your Major Accident Scenario Documents  we are preparing.

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If you wish, we can also draw the Layouts and P&IDs of the entire facility and deliver them to you for use in the quantitative risk assessment phase.

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Major accident scenario document

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ARTICLE 8 –  (1) Major accident scenario document is prepared or has it prepared by the operator of the lower and higher level establishments within the scope of this Regulation in order to determine the dangers of major industrial accidents and to evaluate the risks that may arise from these hazards.

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(2) Major accident scenario document, after the identification and classification of dangerous goods in accordance with the definition of dangerous goods in Article 5 of this Regulation, by using one or more of the methods in the national or international standards and generally accepted scientific literature, The major accident scenario document to be issued within the scope of the project is prepared in accordance with the criteria specified in the communiqué and by following the steps below:

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a) Identification of hazardous equipment.

b) Identification of internal hazards through identified hazardous equipment.

c) Identification of external hazards that may originate from outside the organization that may affect hazardous equipment.

ç) Establishing major accident scenarios on dangerous equipment with methods that can produce results suitable for comparison with the major industrial accident frequency value in Article 9 of this Regulation.

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(3) During the determination of internal and external hazards, past accidents, near misses and accessible records in accident data banks are also taken into account.

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(4) Major accident scenario is formed in a way to include all possible spread, fire or explosion events, starting from the root causes determined according to the hazards determined according to the second paragraph. However, in scenarios to be created using a single root cause and effect pair, each of the possible spread, fire and explosion events is taken into account.

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(5) The operator shall provide detailed information about the reliability data and probability data used in the major accident scenario document from which data banks or sources.

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(6) In case the operator becomes a lower or higher level organization due to the change in the type and/or amount of dangerous goods, this document shall be prepared within one year following the date it is included in the scope.

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(7) The operator keeps the prepared major accident scenario document in the establishment.

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(8) The Ministry of Family, Labor and Social Services publishes a communiqué containing the procedures and principles regarding the major accident scenario document.

Limit value of major industrial accident frequency

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ARTICLE 9 –  (1) The operator reduces the frequency of occurrence of each major industrial accident scenario to 1x10-4/year or less, for dangerous equipment that may cause major accidents.

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Major accident scenario document, “ Regulation on Preventing Major Industrial Accidents and Reducing Their Effects ”  After the identification and classification of dangerous goods in accordance with the definition of dangerous goods in Article 5, one or more of the methods in the national or international standards and generally accepted scientific literature are used, and the major accident scenario document to be issued within the scope of the relevant regulation is specified in the communiqué. It is prepared in accordance with the criteria and following the steps below:

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a) Identification of hazardous equipment.
b) Identification of internal hazards through identified hazardous equipment.
c) Identification of external hazards that may originate from outside the organization that may affect hazardous equipment.
ç) Establishing major accident scenarios on dangerous equipment with methods that can produce results suitable for comparison with the major industrial accident frequency value in Article 9 of the Regulation.

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In order to have a detailed idea about Quantitative Risk Assessment and GYS, please review the Article and Blog section.

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