Chemical Process Safety | Process Hazard Analysis Method Selection
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1. Overview
There are many ways to analyze process hazards, and all methods encourage brainstorming. Among the various methods, there is no one method that is "better" than the other method, the only difference being that the characteristics of the analysis method are different. The more systematic the analytical method, the more it can compensate for the lack of experience of the analytical team (eg, hazard and operability analysis). The lower the degree of systematization of the analytical method, the more experienced analytical teams need to complete the established tasks (eg, “what-if analysisâ€).
2. Analysis method selection
There are many methods for process hazard analysis, which can be summarized into three levels: qualitative analysis, semi-quantitative analysis and quantitative analysis. In practical applications, it is necessary to select an appropriate analysis method depending on the purpose of the analysis. The effectiveness of the control method is assessed based on the priority of the improvement measures, generally from qualitative to quantitative, from simple to complex (see Figure 2-2 ).
( 1 ) Qualitative analysis
Qualitative analysis is often used to identify hazards and accident scenarios, and to qualitatively determine whether the risk is tolerable. Such as accident case analysis, safety checklist ( Checklist ), active chemical / process hazard analysis ( RC-PHA ), hazard and operability analysis ( HAZOP ), fault hypothesis analysis ( What-if ), accident tree (or failure) Tree) analysis method, failure mode and effect analysis ( FMEA ), fault hypothesis and safety checklist method, etc.:
HAZOP analysis should be adopted for the risk identification, control and management of hazardous chemical process plants and their new, modified and expanded projects . For process units that require in-depth analysis of the factors affecting fire and explosion accidents, the accident tree (or fault tree) can be reused. ) analysis; for process control systems that are complex, with a variety of processes for various types of instrumentation , HAZOP analysis can be performed after failure type and impact analysis ( FMEA ) ; safety checklists can be selected for less dangerous chemical processes , hazard analysis, pre-risk analysis, etc.; if the node has many instruments, after the FMEA analysis, the HAZOP method can be used ; for special research (eg, site selection, human factors, solid processing systems, screening, etc.), A “ hypothetical analysis †checklist can be used ; for nodes without hazardous materials (eg, water pipes, air mains, nitrogen lines), a “ what-if analysis †can be used .
(2) Semi-quantitative analysis
Semi-quantitative analysis can be used to assess the magnitude of risk, such as fire and explosion risk index ( F&EI ), chemical exposure index ( CEI ), protective layer analysis ( LOPA ), and instrument safety integrity level ( SIL ) assessment.
The Fire and Explosion Hazard Index ( F&EI ) and Chemical Exposure Index ( CEI ) analysis methods are process hazard analysis tools developed by Dao Chemical Company. They are commonly used in initial project hazard analysis, general layout assessment and hazardous area prediction for new projects.
LOPA is a semi-quantitative risk assessment technique that typically uses initial event consequences.
The SIL rating is based on LOPA analysis and is often applied to the safety integrity level determination of interlocking systems.
(3) Quantitative analysis
Quantitative analysis can analyze more complex scenarios, quantitatively assess risks, and use the results for risk comparison and risk decision making. Quantitative analysis eliminates and reduces the hazards in the process based on hazard identification and risk assessment, mitigates the consequences of accidents, and proposes risk control measures and complete solutions to control the risks of the company within an acceptable range. Analytical methods mainly include SIL level assessment and quantitative risk assessment.
(Source: China Chemical Safety Association)
[Editor: Chen Guofang]
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