Contents
Consequence Modeling Source Models I: Liquids & Gases
Sponsor: Jan Wagner (Oklahoma State University)
This module was developed to help introduce issues of safety and loss prevention in undergraduate engineering courses. Each of the five major sections can be used independently, depending on the student's backgrounds.
- Section 1 is an introduction to the role of source models in the risk assessment process.
- Section 2 introduces the basic information required to select or develop an appropriate source model for a given release scenario.
- The fundamental concepts of the 1st Law of Thermodynamics, the mechanical energy balance, and friction losses in pipes and fittings are reviewed briefly in Section 3.
- Section 4 deals with flow of liquids in pipes and orifices. The example problems are intended to introduce loss prevention issues, and they can be used in any fluid mechanics class.
- Section 5 presents the flow of ideal gas in orifices and pipes. This material may be appropriate in fluid mechanics or thermodynamics classes. The derivations of equations for compressible flow are intended to show the relationships between physical phenomena and the mathematical model; the fundamental concepts apply to ideal and real gases.
The module resources include text, accompanying PowerPoint presentations, student homework problems, and an instructor's solution manual.
Compressible and Two-Phase Flow with Applications Including Pressure Relief System Sizing
Sponsors: J. Wagner and R. Whiteley (Oklahoma State University)
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.
Emergency Relief System Design for Single and Two-Phase Flow
Sponsor: Ron Darby (Texas A&M University)
This Design Module covers the principles and procedures for sizing emergency relief systems for both single-phase (gas or liquid) and two-phase flow, including relief devices as well as inlet and discharge piping. The Homogeneous Direct Integration method for two-phase flow described herein is simpler, more general, and more rigorous than methods previously presented. The material is in a form which could be incorporated into courses on applied fluid mechanics, process safety, or process design, or it could be presented separately as a "stand alone" topic. It is assumed that the student has a familiarity and working knowledge of the macroscopic conservation laws for mass, energy, and momentum, and Newtonian fluid flow through pipes and fittings, including incompressible as well as compressible flow up to and including choked flow. Several worked examples are included which serve to illustrate applications of the procedures and equations, or which can be used for student exercises. A Power Point presentation is included, as are the spreadsheet calculations for the example problem solutions.
Safety Valves: Practical Design Practices for Relief Valve Sizing
Sponsors: Eric N. Parvin and Arthur M. Sterling (Louisiana State University)
The goal of this module is to inform and educate inexperienced engineers about process safety management in general, and about safety valve sizing and the application of engineering principles to safe process design in particular. We also hope to encourage logical thinking patterns in an overview of process design for inherently safer process systems. The target audience will normally be college engineering students, but may also be entry-level engineers (0-3 years) who have not yet been exposed to this subject matter, or as a refresher for more experienced engineers.
Contained within this package are two software files (one MS PowerPoint presentation and one MS Excel file).
- The PowerPoint presentation is intended for educational purposes to gain knowledge and a general understanding of Process Safety Management. It is intended to take about one hour to present the material, but can be shortened (see "instruction" slide for further details).
- The Excel file contains several practical exercises for the students to work in a recitation-type environment, preferably in groups of two or three students. The Excel file contains the problems, solutions, and instructions to prepare the handouts for the class. The recitation is expected to take at least one and a half hours.
Understanding Atmospheric Dispersion of Accidental Releases
Sponsor: R. Schneider (CCPS Staff)
This SACHE product is a relatively short CCPS concept book that includes a basic description of the processes involved in accidental releases of chemicals and the resulting downwind concentrations of gases, vapors, and aerosols. It describes the complex physics of neutrally buoyant vapors, dense-vapors, high-momentum releases, boiling and evaporating liquids, multiphase flow, and aerosol releases.
The focus of this document is not on the calculation methods, but on the physical problem descriptions. This information will give the reader an excellent background to understand the assumptions and results of dispersion analysis useful in developing emergency response plans or as a part of a process hazard analysis. The document is also a useful tool to assess methods to prevent or mitigate releases.
The material is intended only as a basic introduction to dispersion modeling and the interested reader is encouraged to consult the cited references for further information.
Simplified Relief System Design Package
Sponsor: Ed Kitchen (Digital Solutions Technology, Inc.)
The Mach II system is unique to any other relief system design software because it is custom designed specifically for speed, user-friendliness, flexibility, compatibility, API/ASME single-phase sizing, and DIERS two-phase methodology. In short the Mach II is easy to learn simple to use yet it is very comprehensive. The Mach II program will calculate the required capacity of each relief scenario not already input by the user, and will then calculate the required and standard orifice size and standard relief capacity. The program will then select the worst-case scenario, largest required orifice, as the basis for the design of the relief system to include the associated piping. The program also has a built-in piping program where the user can choose the number and type of fitting for both inlet and outlet piping. Mach II then calculates the piping resistance and pressure drop for this piping arrangement. Mach II is intuitive to use and the results are produced instantaneously by just clicking on the Generate Report tab after all input data has been entered. Mach II was designed based on the requirements as set forth in OSHA 29 CFR 1910.119a whereby relief system design and design-based calculations must be compiled and maintained for all processes involving highly hazardous chemicals.
Solutions to Student Problem Set Volume 2
Sponsors:
R. Willey (Northeastern University)
D. Crowl (Michigan Tech University)
R. Welker (University of Arkansas)
R. Darby (Texas A&M University)
"Safety, Health, and Loss Prevention in Chemical Processes - Volume 2" was originally published by CCPS in 2002 and distributed to SACHE University Members. This was a very popular and valued product that is now out of print. R. Willey recently put this volume in electronic form for distribution here.
Like the Volume 1 problems, the 218 problems teach safety, health, and loss prevention. This solution set represents problems and solutions produced by SACHE in the period 1990 to 2000.
The problems were designed for use in existing engineering courses, such as: Stoichiometry, Thermodynamics, Fluid Mechanics, Kinetics, Heat Transfer, Process Dynamics and Control, Computer Solutions, and Mass Transfer. The authors believe that including these problems in a required undergraduate course helps engineering students develop a safety culture and mind set that will benefit them throughout their careers.
Student AIChE 2002 Design Problem Solution
Sponsors:
S. Horsch and J. Louvar (Wayne State University)
J. Wehman (BASF Corporation, retired)
This product includes a solution to the 2002 AIChE Design Problem that was developed by a student (S. Horsch) with significant assistance from very knowledgeable design professionals; these are the professionals who developed this design problem, and they have worked on this design in an industrial environment.
This product includes concepts, calculations, and drawings that can be used in future AIChE design solutions, for example:
- Relief valve calculations for gases, liquids, and two phase flows;
- Safety review including hazards and resulting safety measures to prevent accidents and inherent safety concepts and features;
- The process flow diagram (PFD) and process and instrument diagram (P&ID); and
- MathCad programs for making the design calculations.
All of the MathCad programs and Visio drawings can be copied for using in future design problem solutions. Additionally, the safety review and inherent safety discussions will be an excellent aid in the development of safety and inherent design concepts for all future AIChE design problems. The AIChE Student Chapters Committee that administers the annual AIChE Design competition approved posting of this example problem.