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SAChE Products can be used and adopted to learning environments including students in many different fields (such as chemical and mechanical engineering as well as chemistry and materials science) and practicing engineers (such as in safety training programs). We attempt to put the materials in an easy to use format, and modifications can be made to the materials to fit the circumstances.



Case History: A Batch Polystyrene Reactor Runaway

Sponsors

Ron Willey (Northeastern University)

Description

This case history describes a runaway reaction that occurred in a batch reactor manufacturing polystyrene. Companies now use semi-batch reactors (or stepwise addition of reactants) for such highly exothermic reactions. This case history emphasizes the importance of carefully analyzing and controlling exothermic reactions. When control is lost, the consequences can be catastrophic – for this case, a large fire due to an uncontrolled release of a flammable material, or to large reactor explosions (a nitroaniline reactor explosion case history in another SACHE product).

In this case study, lessons learned include:

  • use of redundant process control equipment with audible alarms,
  • use of semi-automated discharge systems,
  • maintenance of critical process control equipment,
  • develop, manage, and test emergency procedures,
  • understand the hazardous characteristics of exothermic reactions,
  • understand that semi-batch reactors should be used for highly exothermic reactions, and
  • use of the Dow Fire and Explosion Index to identify and eliminate potential design and operating problems.

This case history is in a PowerPoint format that includes notes. The presentation can be used in reactor kinetics or design courses.

Student access: The PowerPoint presentation is available to students through the site.

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Compressible and Two-Phase Flow with Applications Including Pressure Relief System Sizing

Sponsors

J. Wagner and R. Whiteley (Oklahoma State University)

Description

This SACHE product introduces mass, momentum, and energy balances for fluid flow in pipes and orifices. A brief review of incompressible fluid flow reinforces fundamentals and illustrates problem-solving techniques using spreadsheets to introduce concepts of compressible flow in pipes and orifices. These materials can be used in several courses; e.g., fluid mechanics, heat transfer, and senior design courses.

The differential momentum balance for real gases is used to describe vapor flow in pipes including limitations of sonic velocity (choked flow) on mass flow rates (illustrated with examples). The material on two-phase flow is limited to friction losses and slip. Friction factor and void fraction correlations based on both separated flow and homogeneous flow models are presented (illustrated with examples of flashing and non-flashing systems). Important for sizing emergency relief systems, flashing liquid flows modeled as non-equilibrium flow in short pipes and nozzles are discussed along with the effect of sub-cooled liquid at the relief inlet.

The Pipe Flow.xls and Pipe Flow 3-Point.xls applications each contain over three thousand lines of Visual Basic(c) code to solve the mass, momentum, and energy balances for single-phase liquid, single-phase vapor, or vapor-liquid two-phase flow in pipes of constant diameter. Users can select the type of flow problem (calculate flow, inlet pressure, or outlet pressure) and correlations for two-phase friction factor and void-fraction. Both applications accommodate single and multi-component systems.

Pipe Flow 3-Point.xls fits property expansion models to user input results for three adiabatic flash calculations. These models are used to calculate the physical and transport properties and vapor quality required for the numerical integration of the differential momentum balance.

Pipe Flow.xls uses Chemstations’ Chemcad(c) process simulator as a VBA server to perform flash calculations and to calculate the physical and transport properties, as well as the vapor and liquid phase compositions.

Nozzle Flow.xls and Nozzle Flow 3-Point.xls are Visual Basic(c) applications for sizing or rating relief valves or flow through orifices. Nozzle Flow 3-Point.xls uses property expansion models based on the results of user input isentropic flash calculations, while Nozzle Flow.xls uses Chemcad(c) to directly perform flash calculations.

This SACHE product is a companion to several previously published SACHE products by Darby (2005), Grossel and Louvar (2006), Parvin and Sterling (2003), and Wagner (2004).

This product was updated January 2011, and an errata from the first printing is available.

Student access: All files are available to students logged into the site.

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Dow Fire and Explosion Index (F&EI) and Chemical Exposure Index (CEI) Software

Sponsors

S. Mannan (Mary Kay O’Connor Process Safety Center)
W. Smades (Dow Chemical Company)

Description

This SACHE product covers The Dow Fire and Explosion Index Hazards Classification Guide 7th edition and Chemical Exposure Index Guide developed by The Dow Chemical Company and published by AIChE. The program was developed as a collaborative effort between the Mary Kay O'Connor Process Safety Center, The Dow Chemical Company and the American Institute of Chemical Engineers (AIChE).

F&EI is a quantitative hazard index. It is based on historical data as well as the energy potential of the materials under evaluation and the extent to which loss prevention practices are applied. F&EI helps engineers to be aware of the hazards in each process unit and facilitates decisions to reduce the severity and/or the probability of the potential incident.

The Chemical Exposure Index (CEI) provides a simple method of rating the acute health hazard to people in neighboring plants or communities due to chemical release incidents. The CEI system provides a method of ranking one hazard relative to another. The CEI is used:

  • For conducting an initial Process Hazard Analysis (PHA),
  • To identify recommendations to mitigate risks, and
  • In Emergency Response Planning.

This product includes the programmed calculations for the Fire and Explosion Index and Dow Chemical Exposure Index. User input determines the penalties and credits used to calculate the Fire and Explosion Index. Dow CEI lets the user simulate six different and independent release scenarios (gas, liquid overfill, etc) simultaneously. The results include the airborne quantity, Chemical Exposure Index, and Hazard Distance.

Instructions for installing the software are included in the startup file.

Student access: All files are available to students logged into the site.

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Jeopardy Contests for Process Safety

Sponsors

Jon Bernardi (Lubrizol Corp.)

Description

This SACHE product contains some important elementary concepts in chemical process safety. The understanding of these concepts is assessed and reinforced with two class Jeopardy Games. For the game, it is recommended to divide the class into teams of four or five students. Topics include process descriptions, process safety management, process control, flammability, corrosion, relief device basics, and Design Institute for Emergency Relief Systems (DIERS).

This SACHE product includes:

  • Background resources for some questions (student resources to study)
  • Two PowerPoint case history presentations (student resources to study)
  • Jeopardy Game instructions for the game facilitator, and
  • Two Jeopardy Games

Student access: The Background resources and the two PowerPoint presentations are available to students through the site.

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Layer of Protection Analysis - Introduction

Sponsors

Art M. Dowell (Chemical Process Safety Consultant and Rohm and Haas, retired)

Description

Layer of Protection Analysis (LOPA) is a semi-quantitative tool for analyzing and assessing risk that has gained acceptance in the Chemical Processing Industries (CPI) and has risen to be one of the leading risk assessment techniques used for process safety studies. LOPA generally employs more rigor and science than what is encountered with qualitative risk assessments but is less demanding than a detailed Quantitative Risk Assessments (QRA).

LOPA uses simplified methods to characterize the consequences and estimate the frequencies in the risk assessment process. To lower the frequency of the undesired consequences, layers of protection can be added to a process including: inherent process safety; the basic process control system; safety instrumented functions; passive devices, such as dikes or blast walls; active devices such as relief valves; and human intervention. The primary purpose of LOPA is to determine whether there are sufficient layers of protection against a specific accident scenario.

This product discusses important LOPA concepts, such as, a) rules for independent protection layers (IPL), b) basic process control systems (BPCS), c) safety integrity levels (SIL), d) methods for calculating mitigated consequences, and e) advantages of LOPA. An example using LOPA on a distillation column is included. This product assumes that students are familiar with process hazards analysis (PHA) techniques such as HAZOP and is intended for undergraduate students (especially in design courses) and practicing engineers interested in using LOPA.

Student access: An introduction and references are available to students through the site.

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Safety Guidance for Design Projects

Sponsors

Bruce K. Vaughen (Cabot Corporation)

Description

This SACHE Product provides guidance for engineering design teams to help them meet the process safety requirements of academe and industry. A design project road map is included to help design teams incorporate the elements of Process Safety Management (PSM) used in industry. Specific SACHE products and SACHE Safety Certificates are referred to in this road map.

This product includes a description of the T2 accident that was the genesis of an important CSB recommendation that AICHE and ABET work together to add reactive hazard awareness to undergraduate chemical engineering curricula. This product includes:

  • An overview,
  • A PowerPoint presentation discussing: background including T2; project design process (road map); available SACHE resources; and a summary that gives a historical perspective of this product, and
  • Handouts that are used with the PowerPoint presentation.

The Powerpoint presentation in this product was updated in January 2011.

Student access: All files are available to students logged into the site.

Downloads (336)

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