Decision support systems for major accident prevention in the chemical process industry: A developers’ survey

Solid major accident prevention management is characterized by efficient and effective risk assessments. As a means of addressing the efficiency aspect, decision support analysis software is becoming increasingly available. This paper discusses the results of a survey of decision support tools for investigating (internal and external) major hazards in the chemical industry. The most significant features, such as the usability and the functionality of the toolkits are discussed. Toolkit characteristics are analyzed in the light of the different major risk decision process stages. Consequently, valuable supportive information for company decision makers purchasing such software is given. Furthermore, conclusions are drawn and recommendations are formulated for establishing priorities for future risk toolkits developments.     

Comparing Landslide Maps: A Case Study in the Upper Tiber River Basin, Central Italy

/ The preparation of landslide maps is an important step in any landslide hazard assessment. Landslides maps are prepared around the world, but little effort is made to assess their reliability, outline their main characteristics, and pinpoint their limitations. In order to redress this imbalance, the results of a long-term research project in the Upper Tiber River basin in central Italy are used to compare reconnaissance and detailed landslide inventory maps, statistical and geomorphologically based density maps, and landslide hazard maps obtained by multivariate statistical modeling. An attempt is made to discuss advantages and limitations of the available maps, outlining possible applications for decision-makers, land developers, and environmental and civil defence agencies. The Tiber experiment has confirmed that landslides can be cost-effectively mapped by interpreting aerial photographs coupled with field surveys and that errors and uncertainties associated with the inventory can be quantified. The experiment has shown that GIS makes it easy to prepare landslide density maps and facilitates the production of statistically based landslide hazard models. The former supply an overview of the distribution of landslides that is easily comprehended but do not provide insight on the causes of instability. The latter, giving insight into the causes of instability, are diagnostically powerful, but are difficult to prepare and exploit.     

Estimated chemical usage by manufacturers in Connecticut

Background

There is little available data on chemical use patterns by companies, with few federal requirements for reporting. This results in difficulties for targeting toxics for possible substitution, assisting employers with complying with newer international regulations, and decreased ability to estimate health and environmental impacts.

Methods

Massachusetts chemical use data for manufacturers required under the Toxics Use Reduction Act (TURA) was acquired, with corresponding information on industrial sector classification and employment levels by sector for both Massachusetts (MA) and Connecticut (CT). The MA chemical data was adjusted based on the ratio of employment levels by sector for CT compared to MA to give estimates of chemical usage by sector in CT.

Results

It was estimated that there was over 660 million pounds of chemicals used in CT, with over 300 million pounds each of carcinogens and reproductive hazards (categories overlap). The most common chemicals estimated to be used were styrene monomer (266 million lbs.), sodium hydroxide (60 million lbs.), and methanol (50 million lbs.). The industrial sub-sectors estimated with the highest chemical usage were chemical manufacturing, plastics and rubber products manufacturing, and fabricated metal product manufacturing.

Conclusion

There is extensive chemical use in CT manufacturing, but little direct information on actual use patterns.     

A critique of the Hazard and Operability (HAZOP) study

Conventional wisdom holds that the Hazard and Operability (HAZOP) study is the most thorough and complete process hazard analysis (PHA) method. Arguably, it is the most commonly-used PHA method in the world today. However, the HAZOP study is not without its weaknesses, many of which are not generally recognized. This article provides a critique of the method to assist study teams in compensating for them to the extent possible and to help guide the development of improved methods.     

An extended HAZOP analysis approach with dynamic fault tree

An extended hazard and operability (HAZOP) analysis approach with dynamic fault tree is proposed to identify potential hazards in chemical plants. First, the conventional HAZOP analysis is used to identify the possible fault causes and consequences of abnormal conditions, which are called deviations. Based on HAZOP analysis results, hazard scenario models are built to explicitly represent the propagation pathway of faults. With the quantitative analysis requirements of HAZOP analysis and the time-dependent behavior of real failure events considered, the dynamic fault tree (DFT) analysis approach is then introduced to extend HAZOP analysis. To simplify the quantitative calculation, the DFT model is solved with modularization approach in which a binary decision diagram (BDD) and Markov chain approach are applied to solve static and dynamic subtrees, respectively. Subsequently, the occurrence probability of the top event and the probability importance of each basic event with respect to the top event are determined. Finally, a case study is performed to verify the effectiveness of the approach. Results indicate that compared with the conventional HAZOP approach, the proposed approach does not only identify effectively possible fault root causes but also quantitatively determines occurrence probability of the top event and the most likely fault causes. The approach can provide a reliable basis to improve process safety.     

智能型城市防洪除涝决策支持系统总体设计研究

智能型城市防洪除涝决策支持系统是城市防洪除涝减灾的一种综合性非工程 措施。本文根据作者的经验总结和研究工作,着重阐述了其总体设计的思路、原 则、特点、及结构设计,并对专家系统、GIS技术、遥感遥测技术等高新科技在 城市防洪除涝减灾辅助决策中的作用,作了专门论述。     

Development of a FRAM-based framework to identify hazards in a complex system

System-based approaches such as Functional Resonance Analysis Model (FRAM) are developed to model the complex interactions of system variables and their performance variabilities that may lead to a hazardous scenario in a complex system. However, they have limitations to be applied in process industries for hazard identification since they are heavily based on qualitative analysis and expert elicitations. To overcome the limitations of the system-based hazard identification, the study developed a FRAM-based framework to integrate a human performance model, an equipment performance model, and a first-principle based chemical process model into a hybrid simulator, which will be able to aid hazard analysis in the process industries. The simulator is capable of simulating the performance variabilities of the functions through the aggregation of mathematical models within a complex system, which can be used to simulate potential hazard situations and identify the corresponding interactions. Interaction analysis is conducted by applying association rule mining to the simulated data. The impact of the interactions among upstream functions on the performance of downstream functions can be identified by interpreting the rules, whose antecedents contain upstream functions and consequents contain downstream functions.     

超高层住宅楼的内天井尺寸对自然排烟影响的数值模拟研究

火灾时超高层住宅楼的内天井会形成"烟囱效应",烟气可能通过面向内天井的开启窗户进入四周住宅。利用FDS数值模拟的方法研究火源位置、火源功率和内天井的高度、长度对超高层住宅楼内天井自然排烟的影响。研究结果表明:火源位于内天井四周某住宅时,若住宅内喷淋系统有效,内天井四周其它住宅不会达到危险状态。火源位于内天井底部时,4.0MW的火灾可能会使内天井四周其它住宅受到火灾烟气影响,达到危险状态,此时内天井四周其它住宅到达危险时间与内天井高度满足二次增长函数,到达危险时间随高度的增加趋于稳定。内天井长度d存在临界值,d≤10m时到达危险时间与内天井长度满足二次增长函数;d10m时到达危险时间接近稳定值。     

The impact of recreational boat traffic on Marbled Murrelets (Brachyramphus marmoratus)

This study evaluated the impact of small boat traffic on reaction distances of Marbled Murrelets (Brachyramphus marmoratus), in the marine waters of Pacific Rim National Park Reserve, British Columbia, Canada. Observers on moving boats recorded the minimum distance the boat came to murrelets on the water, and any disturbance reaction (fly, dive, no reaction). Out of the 7500 interactions 11.7% flew, 30.8% dove and 58.1% exhibited no flushing reaction. Using a product-limit analysis, we developed curves for the proportion of Marbled Murrelets flushing (dive or flight) as a function of reaction distance. Overall, the majority of Marbled Murrelets waited until boats were within 40 m before reacting, with 25% of the population reacting at 29.2m. A stepwise Cox regression indicated that age, boat speed, and boat density (loaded in that order), significantly affected flushing response. More juveniles flushed than adults (70.1 versus 51.7%), but at closer distances. Faster boats caused a greater proportion of birds to flush, and at further distances (25% of birds flushed at 40 m at speeds > 29 kph versus 28m at speeds <12kph). A stepwise logistic regression on diving and flight responses indicated that birds tended to fly completely out of feeding areas at the approach of boats travelling >28.8 kph and later in the season (July and August). Other secondary variables included; boat density and time of day. Discussion focused on possible management actions such as the application of speed limits, set back distances, and exclusion of boat traffic to protect Marbled Murrelets.