Combustible Dust Testing

Laboratory testing to quantify dust explosion & reactivity hazards

Flammable Gas & Vapor Testing

Laboratory testing to quantify explosion hazards for vapor and gas mixtures

Chemical Reactivity Testing

Laboratory testing to quantify reactive chemical hazards, including the possibility of material incompatibility, instability, and runaway chemical reactions

DIERS Methodology

Design emergency pressure relief systems to mitigate the consequences of unwanted chemical reactivity and account for two-phase flow using the right tools and methods

Deflagrations (Dust/Vapor/Gas)

Properly size pressure relief vents to protect your processes from dust, vapor, and gas explosions

Effluent Handling

Pressure relief sizing is just the first step and it is critical to safety handle the effluent discharge from an overpressure event

Thermal Stability

Safe storage or processing requires an understanding of the possible hazards associated with sensitivity to variations in temperature

UN-DOT

Classification of hazardous materials subject to shipping and storage regulations

Safety Data Sheets

Develop critical safety data for inclusion in SDS documents

Biological

Model transport of airborne virus aerosols to guide safe operations and ventilation upgrades

Radioactive

Model transport of contamination for source term and leak path factor analysis

Fire Analysis

Model transport of heat and smoke for fire analysis

Flammable or Toxic Gas

transport of flammable or toxic gas during a process upset

OSS consulting, adiabatic & reaction calorimetry and consulting

Onsite safety studies can help identify explosibility and chemical reaction hazards so that appropriate testing, simulations, or calculations are identified to support safe scale up

Mechanical, Piping, and Electrical

Engineering and testing to support safe plant operations and develop solutions to problems in heat transfer, fluid flow, electric power systems

Battery Safety

Testing to support safe design of batteries and electrical power backup facilities particularly to satisfy UL9540a ed.4

Hydrogen Safety

Testing and consulting on the explosion risks associated with devices and processes which use or produce hydrogen

Spent Fuel

Safety analysis for packaging, transport, and storage of spent nuclear fuel

Decommissioning, Decontamination and Remediation (DD&R)

Safety analysis to underpin decommissioning process at facilities which have produced or used radioactive nuclear materials

Laboratory Testing & Software Capabilities

Bespoke testing and modeling services to validate analysis of DD&R processes

Nuclear Overview

Our Nuclear Services Group is recognized for comprehensive evaluations to help commercial nuclear power plants operate efficiently and stay compliant.

Severe Accident Analysis and Risk Assessment

Expert analysis of possible risk and consequences from nuclear plant accidents

Thermal Hydraulics

Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions

Environmental Qualification (EQ) and Equipment Survivability (ES)

Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions

Laboratory Testing & Software Capabilities

Testing and modeling services to support resolution of emergent safety issues at a power plant

Adiabatic safety calorimeters (ARSST and VSP2)

Low thermal inertial adiabatic calorimeters specially designed to provide directly scalable data that are critical to safe process design

Other Lab Equipment (DSC/ARC supplies, CPA, C80, Super Stirrer)

Products and equipment for the process safety or process development laboratory

FERST

Software for emergency relief system design to ensure safe processing of reactive chemicals, including consideration of two-phase flow and runaway chemical reactions

FATE

Facility modeling software mechanistically tracks transport of heat, gasses, vapors, and aerosols for safety analysis of multi-room facilities

Blog

Our highly experienced team keeps you up-to-date on the latest process safety developments.

Process Safety Newsletter

Stay informed with our quarterly Process Safety Newsletters sharing topical articles and practical advice.

Resources

With over 40 years of industry expertise, we have a wealth of process safety knowledge to share.

Recent Posts

PrEVent Practical Emergency Vent Sizing Software: Safer Chemical Reactions

Posted by The Fauske Team on 03.11.15

Per James Burelbach, PhD, Manager, Waste Technology & Post-Fukushima Services, Fauske & Associates (FAI), LLC, “The key parameters in relief vent sizing are the reaction rates at relief conditions, specifically the rate of temperature rise (dT/dt) and the rate of pressure rise (dP/dt).  Safe process design requires knowledge of these adiabatic chemical reaction rates, and also an understanding of the system character (gassy or vapor pressure driven, foamy or not-foamy).”

The AIChE Design Institute for Emergency Relief Systems (DIERS) provided the necessary laboratory tools to gather such data (Fauske & Leung, 1985).  A primary purpose of DIERS was evaluation of emergency relief vent requirements, including energy and gas release rates for systems under actual upset conditions, and the effects of two-phase flow on the discharge process.  DIERS methodology suggested a vent sizing approach utilizing two-phase flow whether the material being vented behaves as a vapor pressure (tempered), gassy, or hybrid (combined gas/vapor pressure) system.  Given the difficulty of predicting two-phase flow regimes, the original DIERS technology recommended the use of the classical homogeneous equilibrium model (HEM) for calculating the two-phase discharge through relief devices.  The widely recognized omega method of Leung (1986a,b) was introduced to quickly calculate critical and subcritical discharge of such two-phase flu

Later DIERS developments by Leung (1987) considered alternate level swell models (churn-turbulent or bubbly flow) to better represent the vessel discharge flow regime for vapor pressure systems.  However, in order to take full advantage of the Leung omega techniques it is necessary to evaluate vapor/liquid disengagement characteristics for the reacting chemical system.  Leung’s methods are well suited for use with adiabatic calorimetry data derived from the VSP2, or Vent Sizing Package (Askonas et. al, 2000).  The VSP2 (originally called the DIERS Bench Scale Apparatus) measures the pressure/temperature (P/T) relationship and reaction rates dT/dt and dP/dt in an adiabatic runaway system (directly scalable to process conditions due to the low thermal inertia i.e. low f-factor design); it can also be used to characterize vessel flow regime by experimental simulation of “blowdown” venting.  Note that for gassy and hybrid systems the Leung approach remains consistent with the traditional DIERS assumption of homogeneous vessel conditions.

Practical DIERS Extensions

The assumption of homogeneous vessel venting has since been criticized as overly conservative in some cases, particularly for gassy systems, and later articles by Fauske (1998, 2000) cite large-scale experimental data for several reactive systems that support a gas/vapor venting approach.  Fauske has gone on to develop a practical emergency vent sizing method, based on vapor/gas venting, which makes direct use of relevant low f-factor adiabatic data.  Such data are readily obtained with the VSP2 or the easy-to-use ARSST, or Advanced Reactive System Screening Tool (Burelbach, 2000). 

Note also that in Fauske’s recent vapor/gas venting methods it is not necessary to resolve uncertainties in the two-phase flow regime; rather it is sufficient to distinguish between “foamy” and “non-foamy” systems.  For vapor pressure systems that exhibit foamy behavior (detectable in the ARSST) an adequate vent size may be obtained using twice the vapor venting relief area and allowing for modest overpressure above the relief set pressure (about 40% on an absolute basis).  This does not mean that two-phase flow does not occur, but just that in many cases a practical emergency vent size can be determined without taking a two-phase flow penalty.  

Fauske (2006) has further simplified the vapor/gas venting equations to eliminate the need for any physical properties whatsoever.  The result is the Fauske General Screening Equation which compares favorably with the available large scale data (Fig. 1).  Kinetic modeling and detailed thermophysical properties - information that is expensive to generate and often not available - are not required.  

PreventFigure1

Fig. 1.  Fauske (2006) General Screening Equation and comparison with benchmark data.

PrEVent Software

The above practical emergency vent sizing methods are easily implemented using Fauske’s PrEVent Sizing Software.  The main Calculation window for PrEVent is illustrated in Fig. 2.  This new application retains the most popular features of previous Fauske vent sizing software programs (VSSP, VSSPH, and RMS) including the Leung omega method, Fauske Gas/Vapor method, and Fauske General Screening method.  The modern User Interface features clear navigation, logical tabs, and intuitive drop down menus that take advantage of cutting edge Windows programming techniques for a crisp seamless user experience.  The streamlined interface allows users to make changes to input values “on the fly” and see the results updated immediately.  This is convenient for parametric studies, such as varying the batch size to see how much reactant will “fit” within a particular vessel/relief installation.  Input parameters, including vessel geometry, reactant properties and adiabatic reaction rates at venting, are conveniently entered using simple drop down windows and saved for later use.

PreventFigure2

Fig. 2.  Calculations page of software showing styrene runaway reaction case.  (For this illustration results are shown for all flow regime options including both Leung and Fauske methods.)

PrEVent is available as a standalone Windows application, or as a Silverlight 4 based web application supporting a wide-range of platforms including all major browsers on both Mac OS X and Windows – Internet Explorer 6, 7 8, Firefox2 and 3, Safari 3 and 4, and Google Chrome.  

For technical information on PrEVent (including full article with references), please contact Jim Burelbach a 630-887-5221 burelbach@fauske.com

Managing Chemical Reactivity - Minimum Best Practice

Subscribe to FAI's Quarterly "Process Safety News"

relief system design, reactive chemical, flammable gas, reactive system, reactive vapor systems

 

Topics: runaway reactions, ARSST, VSP2, chemical reaction, adiabatic calorimetry, PREvent

cta-bg.jpg

Is My Dust Combustible?

A Flowchart To Help You Decide
Download Now