There has been a great deal of investment in development of design criteria and design and construction of heavily reinforced, blast-resistant control rooms. This remains the best option for protective construction against severe blast loading experienced close in to a vapor cloud or other explosion hazard. However, most structures encountered at chemical plants and contemplated for future construction are conventional steel frame, metal clad buildings. In this paper we look closely at the response of such buildings to explosion loads and their ability to undergo large deformations without structural failure. The types of structural elements evaluated include metal decking of various gauge and shape along with a variety of girt and purlin sections. Building frames or bents are also evaluated, although the date base for these is much more limited. The work is based on observations made during investigations of large explosion accidents along with analytical predictions and test measurements. To conclude, we offer specific design criteria and connection recommendations for enhancing the overall strength of a building through the use of conventional components in unconventional construction.
{"title":"Ultimate capacity of blast loaded structures common to chemical plants","authors":"M. Whitney, D. Barker, K. H. Spivey","doi":"10.1002/PRSB.720110407","DOIUrl":"https://doi.org/10.1002/PRSB.720110407","url":null,"abstract":"There has been a great deal of investment in development of design criteria and design and construction of heavily reinforced, blast-resistant control rooms. This remains the best option for protective construction against severe blast loading experienced close in to a vapor cloud or other explosion hazard. However, most structures encountered at chemical plants and contemplated for future construction are conventional steel frame, metal clad buildings. In this paper we look closely at the response of such buildings to explosion loads and their ability to undergo large deformations without structural failure. The types of structural elements evaluated include metal decking of various gauge and shape along with a variety of girt and purlin sections. Building frames or bents are also evaluated, although the date base for these is much more limited. The work is based on observations made during investigations of large explosion accidents along with analytical predictions and test measurements. To conclude, we offer specific design criteria and connection recommendations for enhancing the overall strength of a building through the use of conventional components in unconventional construction.","PeriodicalId":364732,"journal":{"name":"Plant\\/operations Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1992-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123900628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A Hazard Evaluation (HE) study is not finished until the study documentation is complete and all of the issues and recommendations from the HE study have been resolved. While the extent and detail of the HE documentation will vary depending on the HE technique used, and on the stage in the process life cycle at which the study is performed, all studies should include documentation in three categories: 1 Process documentation, defining the design and intended operation of the facility at the time the HE study was performed. 2 HE study documentation, recording the actual performance of the HE study and including, for example, meeting notes or worksheets, logic models, hazard index calculations, etc. 3 Action documentation, summarizing all recommendations, perhaps with prioritization, and listing actions taken in response to the recommendations. Thorough and complete documentation of HE studies is essential for understanding the concerns which give rise to each recommendation, tracking action taken on recommendations to insure that all are resolved, using the HE study as a basis for subsequent HE or quantitative risk analysis studies, using the HE study to assist in the management of change, and periodic updating of the HE study. Modern computer based information storage and retrieval technology also opens the potential for use of HE study documentation as a tool for training and for process troubleshooting.
{"title":"Documentation and utilization of the results of hazard evaluation studies","authors":"D. Hendershot","doi":"10.1002/PRSB.720110414","DOIUrl":"https://doi.org/10.1002/PRSB.720110414","url":null,"abstract":"A Hazard Evaluation (HE) study is not finished until the study documentation is complete and all of the issues and recommendations from the HE study have been resolved. While the extent and detail of the HE documentation will vary depending on the HE technique used, and on the stage in the process life cycle at which the study is performed, all studies should include documentation in three categories: \u0000 \u0000 \u0000 \u00001 \u0000Process documentation, defining the design and intended operation of the facility at the time the HE study was performed. \u0000 \u00002 \u0000HE study documentation, recording the actual performance of the HE study and including, for example, meeting notes or worksheets, logic models, hazard index calculations, etc. \u0000 \u00003 \u0000Action documentation, summarizing all recommendations, perhaps with prioritization, and listing actions taken in response to the recommendations. \u0000 \u0000 \u0000 \u0000 \u0000 \u0000Thorough and complete documentation of HE studies is essential for understanding the concerns which give rise to each recommendation, tracking action taken on recommendations to insure that all are resolved, using the HE study as a basis for subsequent HE or quantitative risk analysis studies, using the HE study to assist in the management of change, and periodic updating of the HE study. Modern computer based information storage and retrieval technology also opens the potential for use of HE study documentation as a tool for training and for process troubleshooting.","PeriodicalId":364732,"journal":{"name":"Plant\\/operations Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1992-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133373825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The reduction of risks associated with chemical processing operations is essential for the safe operation of chemical plants. The reduction of these risks is accomplished through a comprehensive process safety management program. Key elements of this program include Hazard and Operability Studies, Emergency Relief Venting, Process Automation, Management of Change Control Procedures, Process Specific Training, and so forth. Central to many of these elements is a thorough, in-depth understanding of the reactive nature of chemical processing operations. This understanding can only be obtained through intensive laboratory evalutions using “leading edge” process safety testing technologies. To accomplish this goal, a systematic process safety testing program has been established aimed at characterizing the reactive nature of both the desired and undesired chemistry. The information obtained is directly applicable to the development of intrinsically safe processes and for the safe design/operation of chemical processing facilities.
{"title":"Process safety testing program for reducing risks associated with large scale chemical manufacturing operations","authors":"J. Sharkey, R. Cutro, W. J. Fraser, G. Wildman","doi":"10.1002/PRSB.720110412","DOIUrl":"https://doi.org/10.1002/PRSB.720110412","url":null,"abstract":"The reduction of risks associated with chemical processing operations is essential for the safe operation of chemical plants. The reduction of these risks is accomplished through a comprehensive process safety management program. Key elements of this program include Hazard and Operability Studies, Emergency Relief Venting, Process Automation, Management of Change Control Procedures, Process Specific Training, and so forth. Central to many of these elements is a thorough, in-depth understanding of the reactive nature of chemical processing operations. This understanding can only be obtained through intensive laboratory evalutions using “leading edge” process safety testing technologies. To accomplish this goal, a systematic process safety testing program has been established aimed at characterizing the reactive nature of both the desired and undesired chemistry. The information obtained is directly applicable to the development of intrinsically safe processes and for the safe design/operation of chemical processing facilities.","PeriodicalId":364732,"journal":{"name":"Plant\\/operations Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1992-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115018542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper offers an overview of the concept of acceptable risk. Variations in the definition of risk are addressed as well as criteria for measuring and evaluating risk. Risk acceptance depends on many factors, some of which are highlighted. The myth of zero risk is addressed with relevant examples such as dioxin and the U.S. space program. Practical applications of acceptable risk concepts are discussed, featuring the RISK MATRIX from system safety MIL-STD-882. Some sample guidelines and benchmarks are offered.
{"title":"Acceptable risk—an overview","authors":"J. Philley","doi":"10.1002/PRSB.720110409","DOIUrl":"https://doi.org/10.1002/PRSB.720110409","url":null,"abstract":"This paper offers an overview of the concept of acceptable risk. Variations in the definition of risk are addressed as well as criteria for measuring and evaluating risk. Risk acceptance depends on many factors, some of which are highlighted. The myth of zero risk is addressed with relevant examples such as dioxin and the U.S. space program. Practical applications of acceptable risk concepts are discussed, featuring the RISK MATRIX from system safety MIL-STD-882. Some sample guidelines and benchmarks are offered.","PeriodicalId":364732,"journal":{"name":"Plant\\/operations Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1992-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129618305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Le Chatelier's Rule is in wide use for predicting the flammability of mixtures with multiple fuels present. The rule does not conveniently handle multiple inerts or elevated temperatures and pressures. This paper describes an alternate method, developed at Air Products, called FLAMCHEKTM, which conveniently handles these variables. This method for predicting flammability is based upon the commonality of the adiabatic flame temperature of a wide variety of fuels at their upper and lower flammable limits. The method, if PC based, can be extended to automatically control the addition of inerts, fuels, or oxidizers in order to avoid flammable conditions. The concept may be extended to more involved applications, such as within an oil well with fuel gas mixtures containing oxygen. In this case, the location from which a gas sample is obtained for analysis (wellhead) may have a different fuel analysis and flammability condition than the location where an explosion is likely to initiate (bottom of well). Hence a correction of the fuels analysis is required.
{"title":"Predicting and controlling flammability of multiple fuel and multiple inert mixtures","authors":"J. G. Hansel, J. Mitchell, H. Klotz","doi":"10.1002/PRSB.720110408","DOIUrl":"https://doi.org/10.1002/PRSB.720110408","url":null,"abstract":"Le Chatelier's Rule is in wide use for predicting the flammability of mixtures with multiple fuels present. The rule does not conveniently handle multiple inerts or elevated temperatures and pressures. This paper describes an alternate method, developed at Air Products, called FLAMCHEKTM, which conveniently handles these variables. This method for predicting flammability is based upon the commonality of the adiabatic flame temperature of a wide variety of fuels at their upper and lower flammable limits. The method, if PC based, can be extended to automatically control the addition of inerts, fuels, or oxidizers in order to avoid flammable conditions. The concept may be extended to more involved applications, such as within an oil well with fuel gas mixtures containing oxygen. In this case, the location from which a gas sample is obtained for analysis (wellhead) may have a different fuel analysis and flammability condition than the location where an explosion is likely to initiate (bottom of well). Hence a correction of the fuels analysis is required.","PeriodicalId":364732,"journal":{"name":"Plant\\/operations Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1992-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121495113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The behavior of an open system is modeled. Thus, for special cases, the void fraction is predicted as a function of location and time. The open system may be an open vessel or a vessel with an open relief device. A single governing equation is derived based on combining the material and energy balances with the churn-turbulent drift flux relationship and assuming no radial gradients. This partial differential equation is not solved. It is, however, bounded by homogeneous and all vapor venting. These special cases are solved. In homogeneous venting the key variable is time. In all vapor venting under pseudo-steady-state conditions the key variable is location. The solution of the partial differential equation is also discussed. Under pseudo-steady-state and churn-turbulent conditions, the open system is modeled. The minimum void fractions (corresponding to a maximum liquid inventory) with all vapor venting, for vertical, horizontal, and spherical vessels are predicted and compared. Analytical expressions for the local and average void fractions in a vertical vessel and non-unity distribution parameters are presented. Void fraction profiles are compared for three cases: 1. vertical cylinders with distribution parameters (Co values) of unity and 1.5, 2. horizontal and vertical cylinders with varying L/D ratios, and 3. spheres with inscribed vertical cylinders having constant gas production to bubble rise ratio (Ψ′ value). The vertical cylinder average void fraction for non-unity distribution parameters can now be calculated analytically. The horizontal cylinder average void fraction predicted by turning it upright results in an over prediction of at most 4%. The sphere average void fraction predicted via an inscribed vertical cylinder, with the same Ψ′ value, is consistenly high by at most 8%.
{"title":"Disengagement predictions via drift flux correlation vertical, horizontal and spherical vessels","authors":"C. Sheppard","doi":"10.1002/PRSB.720110411","DOIUrl":"https://doi.org/10.1002/PRSB.720110411","url":null,"abstract":"The behavior of an open system is modeled. Thus, for special cases, the void fraction is predicted as a function of location and time. The open system may be an open vessel or a vessel with an open relief device. A single governing equation is derived based on combining the material and energy balances with the churn-turbulent drift flux relationship and assuming no radial gradients. This partial differential equation is not solved. It is, however, bounded by homogeneous and all vapor venting. These special cases are solved. In homogeneous venting the key variable is time. In all vapor venting under pseudo-steady-state conditions the key variable is location. The solution of the partial differential equation is also discussed. \u0000 \u0000Under pseudo-steady-state and churn-turbulent conditions, the open system is modeled. The minimum void fractions (corresponding to a maximum liquid inventory) with all vapor venting, for vertical, horizontal, and spherical vessels are predicted and compared. Analytical expressions for the local and average void fractions in a vertical vessel and non-unity distribution parameters are presented. Void fraction profiles are compared for three cases: 1. vertical cylinders with distribution parameters (Co values) of unity and 1.5, 2. horizontal and vertical cylinders with varying L/D ratios, and 3. spheres with inscribed vertical cylinders having constant gas production to bubble rise ratio (Ψ′ value). The vertical cylinder average void fraction for non-unity distribution parameters can now be calculated analytically. The horizontal cylinder average void fraction predicted by turning it upright results in an over prediction of at most 4%. The sphere average void fraction predicted via an inscribed vertical cylinder, with the same Ψ′ value, is consistenly high by at most 8%.","PeriodicalId":364732,"journal":{"name":"Plant\\/operations Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1992-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128241348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Cashdollar, E. S. Weiss, N. Greninger, K. Chatrathi
This paper describes dust explosibility research in full-scale experimental mines and a 20-L laboratory chamber at the U.S. Bureau of Mines and in a 1-m[sup +3] laboratory chamber at Fike Corporation. The purpose of this research is to improve safety in mining and other industries that manufacture, process, or use combustible dusts. As part of this work, carbonaceous dusts with a wide range of volatilities and various particle size distributions were studied. Laboratory data on the minimum explosible concentrations of predispersed dusts were comparable to mine data for nominal dust loadings that were dispersed by the aerodynamic disturbance from a gas ignition zone. Recommendations are given on the limitations of small-scale testing such as [open quotes]overdriving[close quotes] by too strong an ignitor. The effect of dust particle size on explosibility data is illustrated for coal and aluminum dusts. For both dusts, the finest sizes were the most hazardous. The inerting requirements for preventing explosions were also measured in both laboratory and large-scale systems. All the data show relatively good agreement between the laboratory and the large-scale tests. 50 refs., 14 figs.
{"title":"Laboratory and large-scale dust explosion research","authors":"K. Cashdollar, E. S. Weiss, N. Greninger, K. Chatrathi","doi":"10.1002/PRSB.720110413","DOIUrl":"https://doi.org/10.1002/PRSB.720110413","url":null,"abstract":"This paper describes dust explosibility research in full-scale experimental mines and a 20-L laboratory chamber at the U.S. Bureau of Mines and in a 1-m[sup +3] laboratory chamber at Fike Corporation. The purpose of this research is to improve safety in mining and other industries that manufacture, process, or use combustible dusts. As part of this work, carbonaceous dusts with a wide range of volatilities and various particle size distributions were studied. Laboratory data on the minimum explosible concentrations of predispersed dusts were comparable to mine data for nominal dust loadings that were dispersed by the aerodynamic disturbance from a gas ignition zone. Recommendations are given on the limitations of small-scale testing such as [open quotes]overdriving[close quotes] by too strong an ignitor. The effect of dust particle size on explosibility data is illustrated for coal and aluminum dusts. For both dusts, the finest sizes were the most hazardous. The inerting requirements for preventing explosions were also measured in both laboratory and large-scale systems. All the data show relatively good agreement between the laboratory and the large-scale tests. 50 refs., 14 figs.","PeriodicalId":364732,"journal":{"name":"Plant\\/operations Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1992-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131344000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The CHETAH program has proven to be of great utility in the assessment of reactive chemicals hazards associated with the development of new chemicals and chemical processes. At the Dow Chemical Company, the most frequent use of the program is for the estimation of heats of reaction. Reaction heats are often the single most important parameter in reactive chemicals evaluation since most “worst case” scenarios involve the instantaneous liberation of the reaction energy. Another common use of the program is using CHETAH's unique capability to predict the “explosive” behavior of a material or mixture solely from a knowledge of its molecular structure. Several examples of day-to-day use of the program are presented. Current development activity in the ASTM subcommittee which supports CHETAH are discussed. These include new hazard evaluation criteria, better thermodynamic property estimation techniques, and user friendly versions of the program.
{"title":"Using the ASTM CHETAH program in chemical process hazard evaluation","authors":"D. Frurip","doi":"10.1002/PRSB.720110410","DOIUrl":"https://doi.org/10.1002/PRSB.720110410","url":null,"abstract":"The CHETAH program has proven to be of great utility in the assessment of reactive chemicals hazards associated with the development of new chemicals and chemical processes. At the Dow Chemical Company, the most frequent use of the program is for the estimation of heats of reaction. Reaction heats are often the single most important parameter in reactive chemicals evaluation since most “worst case” scenarios involve the instantaneous liberation of the reaction energy. Another common use of the program is using CHETAH's unique capability to predict the “explosive” behavior of a material or mixture solely from a knowledge of its molecular structure. Several examples of day-to-day use of the program are presented. Current development activity in the ASTM subcommittee which supports CHETAH are discussed. These include new hazard evaluation criteria, better thermodynamic property estimation techniques, and user friendly versions of the program.","PeriodicalId":364732,"journal":{"name":"Plant\\/operations Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1992-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113939315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Halons 1301 and 1211 have been employed widely for over 20 years in a broad array of fire and explosion protection applications. These chemicals, however, have been determined to be environmentally unfriendly due to their high ozone depleting potentials. International treaty, national laws and local ordinances have severely limited the future use of these chemicals. Production in the United States will likely come to an effective halt by 1994. A number of alternative chemicals have been suggested as potential replacements for the halons both in total flooding and streaming agent applications. A comparison of the several viable halon alternatives is made including performance, cost and availability. Areas where new applications data are required are noted.
{"title":"Halon replacement: The law and the options","authors":"J. Senecal","doi":"10.1002/PRSB.720110315","DOIUrl":"https://doi.org/10.1002/PRSB.720110315","url":null,"abstract":"Halons 1301 and 1211 have been employed widely for over 20 years in a broad array of fire and explosion protection applications. These chemicals, however, have been determined to be environmentally unfriendly due to their high ozone depleting potentials. International treaty, national laws and local ordinances have severely limited the future use of these chemicals. Production in the United States will likely come to an effective halt by 1994. A number of alternative chemicals have been suggested as potential replacements for the halons both in total flooding and streaming agent applications. A comparison of the several viable halon alternatives is made including performance, cost and availability. Areas where new applications data are required are noted.","PeriodicalId":364732,"journal":{"name":"Plant\\/operations Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1992-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129201093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Two apparatuses have been developed to characterize the entrainability of dust deposits. The minimum aerodynamic wall shear stress required for dust removal (Critical Shear Stress), measured by the first apparatus, is an indicator of the ease with which dust particles can be removed from a layer. The second apparatus measures the settling velocity distribution of dust clouds, which is an important factor controlling the extent of dispersion as well as the time period during which the entrained dust cloud can remain suspended. Testing has shown that the critical shear stress depends not only on the nature of the dust, but on the way the dust deposit is formed. Therefore, a portable version of this apparatus was developed to allow field testing of dust deposits. This methodology has also been used to evaluate the effect of oil treatment sometimes used in the grain handling industry to reduce dust emission. Simulated explosion tests have demonstrated the importance of critical shear stress on dust entrainability. A simple model calculating unsteady dust concentration in elongated structures has been developed. The model shows that flammable dust concentrations induced in a gallery by a primary explosion exist over a finite length and time period. Therefore, the probability of a secondary explosion depends not only on the dust and layer properties, but on the details of the primary explosion and of the enclosure geometry. A simple criterion for transmission of a primary explosion into an adjoining elongated structure is discussed in the paper.
{"title":"Dust entrainability and its effect on explosion propagation in elongated structures","authors":"E. A. Ural","doi":"10.1002/PRSB.720110314","DOIUrl":"https://doi.org/10.1002/PRSB.720110314","url":null,"abstract":"Two apparatuses have been developed to characterize the entrainability of dust deposits. The minimum aerodynamic wall shear stress required for dust removal (Critical Shear Stress), measured by the first apparatus, is an indicator of the ease with which dust particles can be removed from a layer. The second apparatus measures the settling velocity distribution of dust clouds, which is an important factor controlling the extent of dispersion as well as the time period during which the entrained dust cloud can remain suspended. \u0000 \u0000 \u0000 \u0000Testing has shown that the critical shear stress depends not only on the nature of the dust, but on the way the dust deposit is formed. Therefore, a portable version of this apparatus was developed to allow field testing of dust deposits. This methodology has also been used to evaluate the effect of oil treatment sometimes used in the grain handling industry to reduce dust emission. \u0000 \u0000 \u0000 \u0000Simulated explosion tests have demonstrated the importance of critical shear stress on dust entrainability. A simple model calculating unsteady dust concentration in elongated structures has been developed. The model shows that flammable dust concentrations induced in a gallery by a primary explosion exist over a finite length and time period. Therefore, the probability of a secondary explosion depends not only on the dust and layer properties, but on the details of the primary explosion and of the enclosure geometry. A simple criterion for transmission of a primary explosion into an adjoining elongated structure is discussed in the paper.","PeriodicalId":364732,"journal":{"name":"Plant\\/operations Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1992-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129998934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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