Mary Kay onnor Process Safety Center

United States

Mary Kay onnor Process Safety Center

United States
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Chen S.,Texas A&M University | Koirala Y.,Mary Kay onnor Process Safety Center | Mannan M.S.,Mary Kay onnor Process Safety Center
Global Congress on Process Safety 2017 - Topical Conference at the 2017 AIChE Spring Meeting and 13th Global Congress on Process Safety | Year: 2017

As opposed to the petro-chemical and bulk chemical industry, where continuous processes are widely applied, the pharmaceutical industry still primarily relies on traditional batch process due to the complexity of product, multi-step operation and low-volume production. Considering these conditions, the versatile batch process is more appropriate. Nowadays, driven by the contradiction between increasing demand for drugs and inefficient batch production mode, there is a trend in pharmaceutical industry, that is the transformation from traditional batch process to novel continuous process. Related projects and research that is aimed at analyzing this transition are conducted in worldwide, and the scale of these studies ranges from lab-scale reactions to overall arrangement of the factories. Although continuous pharmaceutical process is thriving, the safety issue in this field is not promoted at the same time. Since the continuous pharmaceutical process is a novel technology, little information can be provided to evaluate its safety level. Moreover, process conditions are usually intensified for continuous process comparing to batch process. It also may bring potential risks and make continuous manufacturing inappropriate for some of pharmaceutical productions. This research provides a comprehensive comparison for batch versus continuous pharmaceutical process by application of Dow's Fire and Explosion Index. In addition to this conventional safety evaluation, influences from production efficiency and specialties in pharmaceutical production are integrated into the comparison. Production of 2-methyl benzimidazole and peracetic acid via batch and continuous processes are conducted in this research. Via these integrative and systematic studies, safety levels of batch and continuous processes is analyzed and compared. The ways in which process conditions, production efficiency, and other requirements influence safety level for different production modes are illustrated. Copyright © (2017) by AIChE.

Skjold T.,GexCon AS | Skjold T.,University of Bergen | Castellanos D.,Mary Kay onnor Process Safety Center | Castellanos D.,Texas A&M University | And 3 more authors.
Journal of Loss Prevention in the Process Industries | Year: 2014

This paper describes an experimental investigation of turbulent flame propagation in propane-air mixtures, and in mechanical suspensions of maize starch dispersed in air, in a closed vessel of length 3.6m and internal cross-section 0.27m×0.27m. The primary motivation for the work is to gain improved understanding of turbulent flame propagation in dust clouds, with a view to develop improved models and methods for assessing explosion risks in the process and mining industries. The study includes computational fluid dynamics (CFD) simulations with FLACS and DESC, for gas and dust explosions respectively. For initially quiescent propane-air mixtures, FLACS over-predicts the rate of combustion for fuel-lean mixtures, and under-predicts for fuel-rich mixtures. The simulations tend to be in better agreement with the experimental results for initially turbulent gaseous mixtures. The experimental results for maize starch vary significantly between repeated tests, but the subset of tests that yields the highest explosion pressures are in reasonable agreement with CFD simulations with DESC. © 2014 Elsevier Ltd.

Yang X.,Mary Kay onnor Process Safety Center | Laird C.D.,Texas A&M University | Mannan M.S.,Mary Kay oConnor Process Safety Center
10AIChE - 2010 AIChE Spring Meeting and 6th Global Congress on Process Safety | Year: 2010

A discussion covers component inspection interval optimization of an oil/gas separation system in offshore plants; mathematical modeling developed for assessing the operational risk focusing on overflow scenario in oil/gas separation system; optimizing component inspection interval; a numerical Pareto optimization technique based on an evolutionary algorism and a technique using a scaling factor to represent the weights of trade-off objectives; Pareto optimal solutions generated to represent the optimal inspection budget and scheduling of pump, control valve, and level transmitter in the system; and choice of component inspection interval sets for whatever relative weighting is considered as the most appropriate one for the actual design problem. This is an abstract of a paper presented at the AIChE 2010 Spring National Meeting (San Antonio, TX 3/21-25/2010).

Alfi M.,Texas A&M University | Nasrabadi H.,Texas A&M University | Banerjee D.,Mary Kay onnor Process Safety Center
Fluid Phase Equilibria | Year: 2016

The study of phase behavior of hydrocarbons inside shale rock has garnered significant attention in contemporary literature. The present work focused on experimental techniques for addressing this challenge. To this end, lab-on-a-chip technology was integrated with high-resolution imaging techniques (inverse confocal microscopy equipment) for investigating the phase behavior of hydrocarbons inside nanoscale capillaries (nanochannels). Experiments were performed to measure the bubble point temperature of pure Hexane, Heptane, and Octane inside nanochannels to study the confinement effect. The novel method of employing a nanofluidic chip enabled the visualization of fluid behavior inside nanoscale channels. The method was found to be highly promising for experimental investigation of the phase behavior in nano-scale pores, which has always been one of the biggest research challenges. The experimental results revealed that for nanochannel depth of 50 nm, the confinement effect in the form of wall-molecule interactions is almost negligible. Additionally, the Peng-Robinson equation of state (PR-EOS) with and without capillary pressure was used for modeling the hydrocarbon phase behavior. Experimental validation of numerical predictions obtained from these thermo-physical models describing the effect of phase behavior for confined fluids were performed in this study. © 2016 .

Safitri A.,Mary Kay onnor Process Safety Center | Gao X.,Texas A&M University | Mannan M.S.,Texas A&M University
AIChE Annual Meeting, Conference Proceedings | Year: 2010

Infrared imaging technique is used in industry as a method to detect fugitive leaks from equipment and pipeline systems. Optical imaging is considered as a smart LDAR (Leak Detection and Repair) because it can scan a large number of equipment in relatively short time compared to detection using Total Vapor Analyzer (TVA) or 'gas sniffer'. In addition, the ability of infrared optical imaging system to visualize the gas plume which is not visible to naked eyes offers another advantage. However, this novel technique poses a lot of challenges in its application due to many uncertainties related to the sensitivity of the camera and factors which may affect measurement. Infrared imaging technique has been used in this research to detect methane gas leak from pipelines and monitor LNG plume from LNG spill. In this work, some significant factors affecting measurement such as gas emissivity, atmospheric attenuation, and stimulated radiation from other objects than the target are being evaluated. Furthermore, potential use of infrared imaging technique for methane gas emissions estimation is proposed in this research. This is carried out by assessing the sensitivity of the infrared camera during monitoring the gas release in order to obtain the minimum detectable gas concentration that still can be observed by the camera under real meteorological conditions. From this test, the correlation of mass flow rate and distance to minimum detectable concentration will be withdrawn. Prior to the test, discharge and dispersion simulation of methane gas at various pressures, temperatures and leak sizes is performed to calculate the gas release rate and predict the downwind concentration of methane gas. Several types of infrared imaging technique also have the capability as a non-contact temperature measurement and thus they can provide a spatial temperature distribution of a target object. This facility is used in this research to demonstrate the temperature profile of LNG gas plume in case of accidental spill of LNG on the ground. However, there is a high discrepancy of the cloud temperature measured using infrared camera to the thermocouple reading. This research has been able to identify the most significant uncertainty which comes from unspecified emissivity of the LNG cloud. The methane gas emissivity is not included in the detector's algorithm and therefore the apparent target temperature shows much higher value than the actual one. In this study, the methane gas emissivity as a function of temperature at different optical depth is analyzed using band absorption model.

Harputlu E.,Texas A&M University | Murray S.L.,Missouri University of Science and Technology | Mentzer R.A.,Mary Kay onnor Process Safety Center | Mannan M.S.,Mary Kay onnor Process Safety Center
Global Congress on Process Safety 2012 - Topical Conference at the 2012 AIChE Spring Meeting and 8th Global Congress on Process Safety | Year: 2012

Operators have a crucial role in calse of an emergency in a process facility. When an abnormality occurs in the process, the operator has a limited time to take corrective actions before system safety devices shut down the system. It is crucial that system designers and safety professionals know about this required time / time frame before operations are initiated Specific research goals for this project include the following: • Estimating the standard time data for operators to take corrective actions in emergency situations. • Developing an easy-to-use computer based modeling system, to allow design/process engineers to find the standard time required for the operator(s) to respond in emergency situations. Current standard time data for carrying out tasks cover normal cases. However, the time required to take actions in emergency situations is different than normal cases. Because of the possibility of a process incident and danger, operators make corrective actions faster compared to normal cases. Therefore, current standard time data do not meet the requirement for emergency situations. A shorter standard time data for emergency situations needs to be estimated. Standard time data for emergency situations is estimated by using time studies. Various time study methods were introduced and discussed. MODAPTS is a predetermined time standard method and stands for MODular Arrangement of Predetermined Time Standards, and was used in this project because it is reliable, easy to use and consistent. The methodology adopted for the study required observing several emergency case videos. Then the operations are decomposed into basic motions (such as walking, hand movement, bend and arise, etc.) by using a video player's frame by frame feature. The amount of time required to take these basic motions was estimated. These estimated times were then compared to MODAPTS data, which is a predetermined time standard system. By comparing MODAPTS's standard time intervals with those estimated from emergency situations, coefficients have been estimated for the various basic motions (e.g., factors such as 0.9, 0.75, etc.). The estimated coefficient for emergency situations will be used in developing a user-friendly computer based modeling system. After the modeling system is complete, when the user enters tasks in the software, it will access MODAPTS, and take the necessary basic motion times and multiply them with the coefficients determined in this work. Therefore, the time required to do those tasks in an emergency will be provided to the user.

Ahammad M.,Mary Kay onnor Process Safety Center | Olewski T.,Texas A&M University at Qatar | Vechot L.N.,Texas A&M University at Qatar | Mannan S.,Mary Kay onnor Process Safety Center
Journal of Loss Prevention in the Process Industries | Year: 2016

Following an accidental spill of cryogenic liquid (e.g., LNG) on a solid substrate (e.g., concrete), the vapor generation corresponds to different boiling regimes i.e., film boiling, transition boiling, and nucleate boiling. As film boiling phenomena dictate the vapor generation in the early stage of the spill, it is considered as the most important boiling regime in the context of cryogenic (e.g., LNG) source-term estimations. This paper presents CFD simulations of cryogenic film boiling for liquid nitrogen (LN2) and LNG as pure methane. Different aspects of CFD modeling such as vapor-liquid interface morphology, the behavior of heat flux at the heated surface, the effect of wall superheats on bubbles generation frequency and bubbles departure diameter are presented. Based on the results of CFD simulations, a first principle model is applied to correlate the wall heat flux in the film boiling regime. This model can be used to enable a faster estimation of wall heat flux when CFD simulations and use of empirical correlations are not feasible. © 2016 Elsevier Ltd

Carreto-Vazquez V.H.,Mary Kay onnor Process Safety Center | Hernandez I.,Mary Kay onnor Process Safety Center | Ng D.,Mary Kay onnor Process Safety Center | Rogers W.J.,Mary Kay onnor Process Safety Center | Mannan M.S.,Mary Kay onnor Process Safety Center
Journal of Loss Prevention in the Process Industries | Year: 2010

The lack of awareness in identifying potential hazardous reactions is commonly cited as a cause of accidents. One major problem is the lack of consensus to assign appropriate reactivity hazards ratings. NFPA 704 instability rating system is widely used throughout the chemical industry. However, this system does not take into account pressure hazards. Inclusion of pressure hazards into the NFPA 704 instability rating will provide a more comprehensive rating system, which will characterize hazards that may arise not only from exothermic reactions, but also from endothermic decompositions with gas evolution. In this work we present a proposed method for developing a simple methodology to include pressure and pressure rates into the assignment of instability ratings. The current NFPA 704 instability rating number for the systems studied does not show a trend between the pressures and pressure rates generated with the assigned rating. Therefore, arbitrary threshold values were chosen to rank the substances according to the pressure and pressure rate generated. Results obtained from a variety of systems with endothermic decompositions show that their pressure and pressure rates have magnitudes comparable to systems that decompose exothermically. So far, this method has been applied only to a limited set of data. However, assignment of arbitrary values for normalized maximum pressures generated and pressure rates, taking as reference the values obtained for the thermal decomposition of cumene hydroperoxide and di-terbutyl peroxide appears to give reasonable limits for the rating chemicals based on their relative pressure hazards. © 2009 Elsevier Ltd. All rights reserved.

Licari F.A.,Pipeline and Hazardous Materials Safety Administration | Licari F.A.,Mary Kay onnor Process Safety Center
Journal of Loss Prevention in the Process Industries | Year: 2010

New performance metrics are necessary to quantify the inherent margins of safety. 11In this paper, margin of safety is an occupational safety phrase, and it is expressed as a ratio. in vapor dispersion models for liquefied natural gas (LNG) spills. Currently, vapor dispersion model calculations in the 49 Code of Federal Regulations, Part 193 as well as Standard 59A of the National Fire Protection Association (2001 edition) reduce the lower flammability limit (LFL) of methane in air by a safety factor of two (to 50% LFL) to ensure that flammable vapors do not extend beyond an LNG facility's property line during an LNG spill. Yet, neither document explicitly states the additional distance or the additional confidence level this existing safety standard creates to separate the public from LNG vapors at 100 percent LFL within the facility vs. 50 percent LFL at the facility property line.Although researchers have successfully validated how vapor dispersion models calculate conservative buffer (exclusion) zones, their collective work did not readily explain to the general public the inherent margins of safety in these models. Havens and Spicer developed correlations to demonstrate how well DEGADIS. 22DEGADIS is a dense gas, vapor dispersion model that was developed in collaboration with the Gas Research Institute and the University of Arkansas. The United States Department of Transportation adopted DEGADIS in its LNG facility siting regulations within Part 193 of the 49 Code of Federal Regulations. predictions compared with field testing measurements in the late 80s (Havens & Spicer, 1985). Their research also confirmed that peak gas concentrations exceeded time averaged measurements during some field trials as well as DEGADIS predictions. Then Hanna, Chang, and Strimaitis (1993) explained how several vapor dispersion models could be compared by calculating geometric mean bias and geometric variance and shared these validation results with the public. The works of the Havens and Hanna teams were also influential in explaining why the maximum concentration of methane in air at the property limits of an LNG facility should be 50 percent of its lower flammability limit during an LNG spill. Eleven years later, Chang and Hanna discussed how the relationships between fractional bias, geometric mean bias, geometric variance, and normalized mean square error could explain vapor dispersion model over and under prediction (Chang & Hanna, 2004). Despite these successful efforts, there has been reluctance to embrace vapor dispersion model results, because exclusion zones are not described as creating margins of safety (i.e. additional separation distance) or higher confidence levels (i.e. a likelihood of being correct) that protect the public.This paper proposes an improved performance metric to evaluate the validity of vapor dispersion models and a statistical methodology to determine the confidence level and the inherent margin of safety in calculating vapor dispersion exclusion zones. Descriptions of the new metric and methodology are presented in this document for the DEGADIS vapor dispersion model, together with example calculations. © 2010.

Jiang J.,Mary Kay onnor Process Safety Center | Castellanos D.,Mary Kay onnor Process Safety Center | Carreto V.H.,Mary Kay onnor Process Safety Center | Mannan M.S.,Mary Kay onnor Process Safety Center
12AIChE - 2012 AIChE Spring Meeting and 8th Global Congress on Process Safety, Conference Proceedings | Year: 2012

The explosion features of corn dust in atmosphere of methane at different concentrations of either dust or gas were studied. Experimental measurements of the maximum explosion pressure and maximum rate of pressure rise were performed by 36 L dust explosion equipment though adapted in such hybrid mixtures. The explosion behavior of such hybrid mixtures revealed significant differences with respect to either dust or gas explosions. This is an abstract of a paper presented at the 2012 AIChE Spring National Meeting and 8th Global Congress on Process Safety (Houston, TX 4/1-5/2012).

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