Papers by Seshu Dharmavaram
Process Safety Progress, Sep 20, 2010
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Process Safety Progress, Jun 7, 2012
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Process Safety Progress, May 6, 2012
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Atmospheric Environment, Sep 1, 2004
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Process Safety Progress, Dec 4, 2017
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Process Safety Progress, Dec 1, 2005
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Process Safety Progress, Sep 1, 2008
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Journal of Hazardous Materials, Jun 1, 1994
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Process Safety Progress, Apr 10, 2023
The Red Squirrel ammonia field experiments were conducted at the DNV Spadeadam site in the UK in ... more The Red Squirrel ammonia field experiments were conducted at the DNV Spadeadam site in the UK in 2022. Field test data currently exists for high‐pressure (ambient temperature) two‐phase releases of ammonia from Desert Tortoise (1983) and FLADIS (1996) experiments. No field tests have ever been done for cold (refrigerated) ammonia liquid spills on dry land or into water. The handling of liquified ammonia, during storage/processing and transportation, in a cold (refrigerated) state is inherently safer than in a high‐pressure (ambient temperature) liquified state. The main objective of the Air Products’ Red Squirrel Tests was to determine the source term and dispersion characteristics for high‐pressure (ambient temperature) liquified ammonia and low‐pressure (cold/refrigerated) liquified ammonia in form of two‐phase releases and liquid spills, respectively. Liquid spills on concrete and water were studied, along with the process conditions that led to the transition from liquid spills to two‐phase flow regimes based on discharge pressures for cold liquified ammonia. Details on the equipment, instrumentation, secondary containment, and ammonia sensors and their layout are presented. An initial analysis of the source terms and dispersion behavior for two‐phase releases and contained liquid spills over a range of weather conditions is also provided.
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Process Safety Progress, Jul 13, 2022
With the industry's increasing reliance on computer systems for basic process control and saf... more With the industry's increasing reliance on computer systems for basic process control and safety functions, industrial processes have become more vulnerable to cybersecurity threats. The recently released CCPS book, Managing Cybersecurity in the Process Industries, A Risk‐based Approach, discusses the need for proactive and effective cybersecurity management in the interest of process safety. This paper will share some of the highlights from the book illustrating areas where cybersecurity considerations parallel and complement the key principles of Risk‐Based Process Safety (RBPS) elements. This paper will share some lessons from recent cybersecurity incidents impacting process safety and identify avenues where cyberattacks can gain access to the control or safety instrumented systems to cause harm. Finally, we will discuss a sampling of the RBPS elements in more detail to illustrate how cybersecurity can be integrated into the RBPS program.
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Process Safety Progress, Sep 1, 2008
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Springer eBooks, Jul 22, 2008
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International Journal of Chemical Kinetics, Jan 7, 2014
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Process Safety Progress
With the industry's increasing reliance on computer systems for basic process control and saf... more With the industry's increasing reliance on computer systems for basic process control and safety functions, industrial processes have become more vulnerable to cybersecurity threats. The recently released CCPS book, Managing Cybersecurity in the Process Industries, A Risk‐based Approach, discusses the need for proactive and effective cybersecurity management in the interest of process safety. This paper will share some of the highlights from the book illustrating areas where cybersecurity considerations parallel and complement the key principles of Risk‐Based Process Safety (RBPS) elements. This paper will share some lessons from recent cybersecurity incidents impacting process safety and identify avenues where cyberattacks can gain access to the control or safety instrumented systems to cause harm. Finally, we will discuss a sampling of the RBPS elements in more detail to illustrate how cybersecurity can be integrated into the RBPS program.
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INTRODUCTION AND FLACS MODEL SUMMARY Computational Fluid Dynamics (CFD) models are useful for sim... more INTRODUCTION AND FLACS MODEL SUMMARY Computational Fluid Dynamics (CFD) models are useful for simulating air flow and plume transport and dispersion within arrays of obstacles such as buildings or pipe racks and tanks. The FLACS CFD model (Hansen, O. et al., 1999) is being used by the authors to estimate flow and dispersion in the atmosphere around chemical processing plants. This paper contains the results of recent evaluations of FLACS with extensive field observations involving tracer gas releases in three independent field experiments (Kit Fox, MUST, and Prairie Grass) and wind tunnel data from the EMU L-shaped building.
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Process Safety Progress, 2017
Water spray curtains are often advertised as means to mitigate the consequences of released chemi... more Water spray curtains are often advertised as means to mitigate the consequences of released chemicals from high pressure tanks. Spray curtain effectiveness claims by certain vendors are misleading—a curtain placed at the periphery of a tank will only scrub a puff of a release. A spray curtain that can effectively contain a consequential release will look very different and cost much more. Studies that demonstrate spray curtains to be effective assume low gas velocities. However, calculations show that pressurized liquid NH3 or HF when released from an orifice to the atmosphere comes out at a high velocity and momentum in the form of a two‐phase jet. The jet must travel quite a distance before the velocity drops enough to be effectively scrubbed by a water curtain. The water curtain therefore needs to be at this large distance and consequently the diameter of the water curtain manifold ring needs to be quite large to be effective. This paper presents engineering calculations to estim...
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Process Safety Progress, 2018
When a liquid mixture, such as an aqueous formaldehyde solution, is released into the environment... more When a liquid mixture, such as an aqueous formaldehyde solution, is released into the environment, the rate of evaporation into the atmosphere depends strongly on chemical reactions that regulate the evolution of formaldehyde vapors. Most of the consequence modeling methods and models currently used in the industry usually ignore any reaction phenomena. This article describes a dynamic model developed using the Aspen® Custom Modeling (ACM) tool kit. In the case of formaldehyde solutions, the thermodynamics and reaction kinetics of a mixture of formaldehyde (HCHO), water and methanol (CH3OH) are computed from models available in the open literature. The liquid‐phase, reversible, chemical reactions between water and formaldehyde, as well as methanol and formaldehyde, form oligomers—most of which are nonvolatile. The mass transfer and heat transfer coefficients between the surface of the spill and the atmosphere are computed by established correlations for flow over a semi‐infinite fla...
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When materials such as Oleums and Chlorsulfonic Acid are released into the environment they react... more When materials such as Oleums and Chlorsulfonic Acid are released into the environment they react with all available water to generate heat and form an acid mist. Most of the consequence modeling methods and models currently used in the industry usually ignore the reaction phenomena. This paper describes a dynamic model developed using the Aspen Custom Modeling (ACM) tool kit. The DuPont-ACM model employs various methods for solving simultaneous systems of nonlinear algebraic and ordinary differential equations. This makes it possible, for example, to solve coupled differential mass and energy balances which are implicit in temperature and composition. Also, even though temperature and composition are not state variables, they can be given initial conditions. The algorithms do not always tolerate discontinuities, so smoothing techniques are used where needed. In the case of oleum, the thermodynamic behavior of the mixture is represented by the vapor-liquid equilibrium of the H2O-H2S...
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ACS Symposium Series, 2013
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Process Safety Progress, 2005
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Papers by Seshu Dharmavaram