SAFER Systems

Camarillo, CA, United States

SAFER Systems

Camarillo, CA, United States
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Shahraz A.,SAFER Systems | Khajehnajafi S.,SAFER Systems
17th Process Plant Safety Symposium, PPSS 2015 - Topical Conference at the 2015 AIChE Spring Meeting and 11th Global Congress on Process Safety | Year: 2015

Perimeter or fenceline monitoring for emissions of hazardous gases is essential for hazardous waste sites, landfills, and industrial facilities. The fenceline monitoring is intended to protect nearby communities through an early warning system, which allows exposed individuals to take necessary actions such as shelter-in-place or evacuation, while helping site owners to reduce potential liability with respect to site activities. Monitoring, in general, must be infused with new technologies to provide better and more cost-effective coverage. In this study, an optimal cost-effective approach is proposed to find the locations of required sensors on the plant's fenceline with any complex geometry and one or multiple hazard points. A network of sensors for all wind directions is obtained using a defined toxic level of concern (LOC), the geometry of the fenceline and its relative location with respect to identified hazard points. The result is optimized by considering sensors overlapping coverage. Sensor placement results can further be refined by taking into account the population distribution and the wind rose. The proposed approach is applied to real plant sites and the results show a considerable reduction in number of required sensors compared to previous studies [3], which lead to decrease in the capital and maintenance cost.


Khajehnajafi S.,SAFER Systems | Burla S.,SAFER Systems
AIChE Annual Meeting, Conference Proceedings | Year: 2010

Industrial facilities must conduct their business in a way that protects people, the environment and property, and continually seeks ways to enhance that process. The public's expectations for the performance of chemical plants in their communities are becoming increasingly stringent. Tolerance for lesser events, such as nuisance odors in their neighborhoods, is gradually decreasing. Faced with these challenges, chemical companies need to design and implement a sophisticated emergency system to manage and respond to hazardous chemical spills. This system must cover two elements: a network of monitoring devices deployed at a physical or a virtual fenceline at the plant, and a computerized emergency response system equipped with GIS mapping and data acquisition. This computerized system has to integrate the real-time meteorological and gas concentration data with a dispersion model to track the trajectory and impact of the plume and, therefore, improve decision making and resource deployment in emergency conditions. Many companies lack a specific guideline for implementing a cost effective gas detection system on site for an efficient emergency/community response solution. The objective of this paper is to provide a guideline for gas sensor siting. Two methods are proposed, based on whether the objective is to solve an odor complaint or an emergency response issue. A number of factors that affect sensor placement, such as a chemical and its concentration level of concern, sensor lower threshold limits, population distribution, prevailing wind conditions, and several others are discussed. A Gaussian dispersion model is utilized to obtain concentration profiles at the plant fenceline and in the surrounding communities. The results from the two methods are compared to show how a plant's objective affects the number of sensors and their placement.


Khajehnajafi S.,SAFER Systems | Pourdarvish R.,SAFER Systems | Shah H.,SAFER Systems
Process Safety Progress | Year: 2011

Smoke is a mixture of toxic gases and suspended particulate matter of solids and liquids that evolves from a fire of flammable materials. This article presents real-time consequence modeling to track the concentration of individual species in smoke as well as its soot deposition. In the modeling process presented, the burning rate or vapor mass is fed into a combustion model in which the combustion of products has been identified and quantified along with the temperature of the fire. The output of the combustion model is the smoke that will be dispersed into the ambient. The fire geometry, which depends on the type of fire (e.g., pool or flare), is identified. A dispersion model with the capability of determining particulate deposition is then used for tracking the smoke plume. The combustion model provides the composition of the toxic species present in the smoke: carbon monoxide, halogen acids, organic and inorganic irritants, and soot, and their quantities as the air-to fuel ratio is changed. The end product is an excellent what-if analysis tool for responders. For example, it provides the ability to determine whether to ignite or when to ignite a flammable, toxic release by comparing their consequences. © 2011 American Institute of Chemical Engineers.


Khajehnajafi S.,SAFER Systems | Pourdarvish R.,SAFER Systems
Process Safety Progress | Year: 2011

Accurate estimation of mass evaporation from a liquid spill is of great concern in the area of hazard analysis. The chemical properties, especially its boiling point with respect to ambient temperature, play a major role in the result of evaporation rate. Many models have been proposed for estimating evaporation rate from a boiling or evaporating pool. The objective of this article is to apply the proposed correlations to good quality pool evaporation data and compare their accuracy. Based on current analysis, we recommend the use of the Churchill model for pool evaporation. This model applies to the range of flow regimes from laminar to turbulent. The model provides convective mass and heat transfer coefficients for a complete range of Re, Pr, and Sc. We also present the individual heat sources forming the pool heat budget to get a feel for the relative importance of individual components in pool evaporation. © 2011 American Institute of Chemical Engineers.


Khajehnajafi S.,SAFER Systems | Pourdarvish R.,SAFER Systems
11AIChE - 2011 AIChE Spring Meeting and 7th Global Congress on Process Safety, Conference Proceedings | Year: 2011

Accurate estimation of mass evaporation from a liquid spill is of great concern in hazard analysis. A discussion on the use of the Churchill model for pool evaporation covers convective mass and heat transfer coefficients; individual heat sources forming the pool heat budget; individual components of pool evaporation; experimental data and predictions for ethanol evaporation; possible regimes of pool evaporation; cases with low to moderate evaporation rate; and the applicability of Churchill's correlation in all fluid flow regimes. This is an abstract of a paper presented at the 2011 AIChE Spring Meeting & 7th Global Congress on Process Safety (Chicago, IL 3/13-17/2011).


Meel A.,SAFER Systems | Khajehnajafi S.,SAFER Systems
Process Safety Progress | Year: 2012

Prediction of pool evaporation rates in the event of liquid spills is an important topic in the area of emergency response and has been actively studied by many researchers. The modeling of pool evaporation involves the vaporization, spreading, and shrinking of spilled liquids. Even though there are several well-established evaporation models for calculating the evaporation flux from a pool, the dynamics of the pool spreading and shrinking phases is not well established. The challenge with these models is due to an intractable solution to the full conservation equations to establish the pool dynamics. Therefore, the problem has been solved by order-of-magnitude estimates of the forces involved: gravity, drag, viscous, and surface tension. Researchers have recognized three different spreading regimes for the expansion of the pool: (1) gravity-inertia, (2) gravity-viscous, and (3) viscous-surface tension. The main driving force for the pool spreading phase is gravity, which is dominant in the early stages of pool expansion. The issues that have not been addressed satisfactorily in the literature are: (a) the maximum radius a pool can expand to; (b) minimum height it can reach before a homogenous pool breaks up into patches of liquids; and (c) the mechanism for the shrinking phase of the pool. In this article, two separate mechanisms are demonstrated for the spreading phase based on the boiling point of the liquid. A pool consisting of nonboiling or low evaporating liquid is allowed to spread up to a minimum height, which is estimated by minimizing the potential energy of the pool. The boiling liquid pool is allowed to spread up to a minimum height of 1 cm as the liquid may not have enough time to spread to their minimum height estimated by minimizing the potential energy because of the higher evaporation rates. In addition, the shrinking phase of the pool evaporation model for liquid spills on solid surfaces in unconfined settings has been broadly categorized into two approaches: (1) a shrinking radius approach (i.e., shrinking pool area) and (2) a shrinking height approach (i.e., nonshrinking pool area). Shrinking radius approach, for both instantaneous and continuous spills, allows the pool radius to expand as long as the height of the pool is equal to the minimum height. After the pool depth reaches the minimum height, this constraint is maintained and the radius is allowed to shrink until the liquid is completely evaporated. On the other hand, the shrinking height approach maintains the pool radius as a constant as soon as the pool depth is equal to the minimum height. From there, the pool height decreases due to evaporative mass losses, while the pool radius remains constant. Furthermore, we try to present arguments on the merit of the shrinking height approach versus the shrinking radius approach for the shrinking phase of pool evaporation on solid surfaces. The results from the two approaches (shrinking radius and constant height vs. shrinking height and constant radius) are compared for various single and binary component spills of varying boiling point ranges for continuous/instantaneous spill scenarios. In particular, pool evaporation rates, pool temperature, pool radius, and total evaporation time are compared for various spill scenarios. Overall, we found that the proposed shrinking height approach methodology represents a more realistic approach than shrinking radius approach for the pool shrinking phase. © 2012 American Institute of Chemical Engineers.


Meel A.,SAFER Systems | Khajehnajafi S.,SAFER Systems
Global Congress on Process Safety 2012 - Topical Conference at the 2012 AIChE Spring Meeting and 8th Global Congress on Process Safety | Year: 2012

Prediction of pool evaporation rates in the event of liquid spills is an important topic in the area of emergency response and has been actively studied by many researchers. The modeling of pool evaporation involves the vaporization and spreading of spilled liquids. Even though there are several well established evaporation models for calculating the evaporation flux from a pool, the dynamics of the pool spreading and shrinking phases is not well established. The challenge with these models is due to an intractable solution to the full conservation equations to establish the pool dynamics. Therefore, the problem has been solved by Order-of-magnitude estimates of the forces involved; gravity, drag, viscous, and surface tension. Researchers have recognized three different spreading regimes for the expansion of the pool; (i) gravity-inertia, (ii) gravity-viscous, and (iii) viscous-surface tension. The main driving force for the pool spreading phase is gravity, which is dominant in the early stages of pool expansion. The issues that have not been addressed satisfactorily in the literature are: a) the maximum radius a pool can expand to; b) minimum height it can reach before a homogenous pool breaks up into patches of liquids; and c) the criteria for the shrinking phase of the pool. In this paper, the shrinking phase of the pool evaporation model for liquid spills on solid surfaces in unconfined settings has been broadly categorized into two approaches: (1) a shrinking radius approach (i.e., shrinking pool area), and (2) a shrinking height approach (i.e., non-shrinking pool area). Shrinking radius approach, for both instantaneous and continuous spills, allows the pool radius to expand as long as the height of the pool is 1 cm or greater. After the pool depth reaches the height of 1 cm, this constraint is maintained and the radius is allowed to shrink until the liquid is completely evaporated. On the other hand, the shrinking height approach maintains the pool radius as a constant as soon as the pool depth is equal to 1 cm. From there, the pool height decreases due to evaporative mass losses, while the pool radius remains constant. In addition, we try to present arguments on the merit of the shrinking height approach vs. the shrinking radius approach for the shrinking phase of pool evaporation on solid surfaces. The results from the two approaches (shrinking radius and constant height vs. shrinking height and constant radius) are compared for various single and binary components spills of varying boiling point ranges for continuous/instantaneous spill scenarios. In particular, pool evaporation rates, pool temperature, pool radius, and total evaporation time are compared for various spill scenarios. Overall, we found that the proposed shrinking height approach methodology represents a more realistic approach than shrinking radius approach for the pool shrinking phase. © Copyright SAFER Systems LLC 2012.


News Article | February 15, 2017
Site: www.prnewswire.com

WESTLAKE VILLAGE, Calif., Feb. 15, 2017 /PRNewswire/ -- SAFER Systems® announced today the general availability of its new real-time, cloud-based chemical detection and emergency response platform - SAFER One™ - ushering in a new ERA for the company and its customers. "SAFER One™ is a...

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