211576535 PHAST Tutorial Manual

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PHASTTutorial Manual

DNV SOFTWAREPalace House, 3 Cathedral Street, London SE19DE, UK

http://www.dnv.com/software

© Copyright Det Norske Veritas. All Rights Reserved.No reproduction or broadcast of this material is permitted without the express written consent of DNV.

Contact [email protected] for more information.



Contents

Chapter 1 An Introduct ion to PHAST 1

In the first chapter you open an example analysis provided with the program,explore its main features, and run the calculations and view the results –without having to enter or change any input data.

Chapter 2 Setting up your own Analysis 18

The second chapter guides you through the process of setting up a Study

Folder for performing consequence calculations for a range of common typesof hazardous event. The tutorial supplies all of the input values that you willneed to complete the analysis.



Chapter 1: Introduction

Chapter 1 An Introduction to PHAST

What to Expect of this Tutorial

The aim of this tutorial is to make you familiar with the ideas and techniques involvedin performing a consequence analysis with PHAST, and to give you practice indefining a range of common types of hazardous events. By the time you have finishedthe tutorial you should have a firm understanding of the issues involved, and be readyto start work on an analysis of your own.

The tutorial is divided into two chapters. In this first chapter you will open an exampleanalysis provided with the program, explore its main features, and run the calculationsand view the results – without having to enter or change any input data. In the secondchapter you will create a new analysis, defining a range of hazardous events andperforming a consequence analysis for them.

The tutorial should take 1-2 hours to complete. You do not have to complete it in asingle sitting, and can take a break between chapters if you prefer.

Starting the Program Running

When you install the program, the installation process places a DNV Software folderunder Programs in your Start menu, and also adds a PHAST shortcut to your Desktop.You can use either method to start the program running.

The Main Window

When you start the program running, the main window will open as shown.

The Main Window on Startup

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The first line in the Message Log should state that the “Licence is valid”. You musthave a valid license for PHAST set up on your computer in order to be able to enterdata and run the calculations. If the Message Log says that you do not have a validlicense, you should contact product support using the details given under Product

Support in the Help menu.

The window will normally open with no Study Folder loaded – where a “StudyFolder” is a file that contains the definition of a consequence analysis – and you mustopen or create a Study Folder file before you can perform any modelling work with theprogram. If you wish, you can change the Installation Preferences under the Options menu so that the program starts by automatically opening a Study Folder (e.g. theStudy Folder you worked on most recently).

Opening the PHAST Example Study Folder

The program is supplied with an example Study Folder called “PHAST ExampleStudy”, which is used in this chapter to give a quick introduction to the terminologyand approach used in the program.

To open the Study Folder, choose Open

Example… from the File menu. A FileOpen dialog will appear as shown,displaying the contents of the Examples folder installed with the program files.There are several file-formats availablefor Study Folder files, but the defaultformat is the *.psu format, and thePHAST Example Study file is in thisformat. Select the file, and click on

Open.

The appearance of the main window changes when a Study Folder is open: there aremany more toolbars, and there is a pane with five tab sections at the left side of thewindow, as shown. The pane is known as the “Study Tree” pane, and you work in itsvarious tab sections to set up the input data for the analysis.

The Main Window with a Study Folder Open

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The Study Tree Pane

The Study Tree pane allows you to organise and edit the input data for yourconsequence analysis. The pane contains a number of tab sections, each of whichcovers a different type of input data, and these tabsections are described below.

The Models Tab Section

The term “Model” is used in two different ways inPHAST, though these different meanings are unlikelyto cause you confusion.

“Model”: a set of available calculations

The program has several different sets of calculationsavailable, and each of these sets is known as a sModel and has its own icon. For example, there is aModel known as the “Vessel/Pipe Source Model” thhas a blue icon that represents a process vessel; thisModel considers the release of material from itsstorage or process conditions in a vessel or pipe,through all the stages in its dispersion to a harmlconcentration, and it also performs fire, explosiontoxic calculations to obtain representativefor the dispersing cloud. There is another Modelknown as the “Fireball Model” that has a red anyellow icon that represents a fireball flame; this Modelconsiders only the radiation effect zones from afireball, and does not perform any of the release andby the Vessel/Pipe Source Model. There are eleven different types of Model in total.

You define a given hazardous event that you want to analyse by s

eparate

at

essand

effect zones

d

dispersion modelling performed

electing the mosthe

t.

h of

icular type of calculation Model

a given use of a particular

l represents the entire

n

suitable Model from the list of the eleven Models. When you select the Model from tlist, the program will insert an icon for that Model into the Models tab section. The iconrepresents an “instance” of that Model and will have its own set of values for the inputdata, and you can define any number of instances of a given Model in your StudyFolder, each with its own set of input data to represent a particular hazardous even

As shown in the illustration, the PHAST Example Study Study Folder contains teninstances of one Model (the Vessel/Pipe Source Model), and one instance of eaceight other kinds of Model.

“Model”: one instance of a part

In practice, people rarely use the term “instance” to refer toModel, and instead refer to the instance directly as a “Model”, so it would be moretypical to say that the PHAST Example Study Study Folder contains eight Vessel/PipeSource Models, one Pool Fire Model and one Fireball Model.

The Model icons are organised in a tree structure. The top leveStudy Folder, with the name PHAST Example Study, the next level is the Study (namedexample), the third level contains several Folders, and the fourth level contains theModels themselves. You can create any number of Studies or Folders, depending o

how you want to organise your analysis.

3




Inserting a Model

You cannot place a Model icon under the Study Folder itself,but only under a Study or Folder. To add a Model at aparticular point in the structure, select the Study or Folder, andthen select the appropriate Model from the Insert menu asshown. You can also insert a Model by selecting the Model

from the Insert cascade at the top of the right-click menu, or byselecting the icon for the Model from the toolbar.

The Weather Tab Section

The Weather tab section contains a folder named Global Weathers with three definitions of weather conditions. The programperforms a separate run of the consequence calculations foreach separate weather conditions, giving a set of results that arespecific to that Weather.

The Weather tab section also contains a Study icon calledExample Cases. In the Model tab section, all of the Models havebeen placed inside the Example Cases Study, but you create anduse any number of Studies in an analysis.

You can insert Weathers underneath a Study in the Weather tab section. Such Weathersare known as “Local Weathers”, whereas those in the Global Weathers folder are knownas “Global Weathers”. When the program is processing the consequence calculationsfor a given Model, it will perform the calculations for every Global Weather and forany Local Weathers under the Study that contains the Model, i.e. the Local Weathersare specific to the Models in that particular Study.

The Parameters Tab Section

In PHAST, Parameters are background inputs thatare applied to all calculations and are not specificto a particular Model.

As with the Weathers, there is a set of GlobalParameters, and you can also define LocalParameters that are specific to a given Study. Ifyou define a local set of Explosion Parameters, forexample, the values in this set will be used insteadof the values for the global Explosion Parameters

during the calculations for the Models in thatStudy.

Green border to icon: shows use of default values

All of the icons in the Global Parameters folder havegreen borders. The program uses this border to show that all of the Parameters underthat icon are using the default values that are supplied with the program. If you changethe value of any of the Parameters then the green border around the icon willdisappear. This allows you to see at a glance which aspects of an analysis are using all-default values, and which are using changed values.

4




The Materials Tab Section

The program is supplied with a set of SystemMaterials that contains full property data for morethan sixty materials. However, the Materials tabsection does not show icons for all of thesematerials, but only for materials that have been

selected in the input data for the various Models ithe Study Folder, or for materials that you haveadded yourself while working in the Material tabsection.

n

PHAST currently only allows you to define GlobalMaterials, and the same set of Materials data willbe used in the calculations for all Model. Youcannot currently define Local Materials to be usedonly for the Models in a given Study.

There are three types of icon present in the Material tab section of the PHAST Example

Study Study Folder:

Green Icon: a Pure Material

The eight green icons are all pure Materials. Each icon has a green border, which showsthat all of the input fields for the material have the values set for that material in theSystem Materials. You can change the values if you wish - e.g. to enter different probitvalues for a toxic material – and if you make changes the green border will disappear.

All of the icons in the PHAST Example Study Study Folder are for pure materials that aresupplied in the System Parameters, but the program also allows you to add your ownmaterials.

Yellow-and-Red Icon: a Mixture

The yellow-and-red icon is a Mixture, and in the PHAST Example Study Folder itrepresents the plume of hydrogen chloride, nitrogen dioxide and sulphur dioxideproduced by a fire in a pesticide warehouse – which is the situation modelled by theWarehouse Fire Model.

This particular Mixture is generated automatically when you run the Warehouse FireModel, but you can also define your own Mixtures, using any combination of thematerials in PHAST, and select these Mixtures for use in the dispersion, fire andexplosion calculations.

Pink Icon: a Pesticide

The six pink icons are all Pesticides, and are used to describe the contents of thewarehouse for the Warehouse Fire Model. Pesticides are only relevant to theWarehouse Fire Model and cannot be selected for any other type of modelling.

5




The Map Tab Section

The Map tab section allows you to set up map image and geographic data so that youcan view the regions and features affected by consequence results.

The map image is defined by the powerstation raster image, and you view the image byselecting Map from the View menu. The Map Window will open in the area to the right

of the Study Tree pane, and you can use the options in the Map menu, the right-clickmenu and the Map toolbar to zoom in and out, to move around in the Map Window,and to control the display of the features of the window such as the scale bar and thelegend.

The Map tab section and the Map Window

The Models are represented by dots on the Map. These dots can sometimes be difficultto see and to relate to the individual Models, but there are several options that can

make this easier:

Changing the Size and Colour of the Dots

Select Map from the Preferences cascade ofthe Options menu to open the MapPreferences dialog, and then move to theModel tab section.

By default the colour is turquoise andthe Point Size is 7 pixels, but if youchange the colour to blue and the size to10 pixels as shown, then the dots will beeasier to see on the powerstation Map.

Displaying the Model Names on the Map

If you move to the Models tab section, select any Model, and then select Labels from theView menu, the names of all of the Models will be displayed on the Map. To hide thenames, deselect the Labels option.

If there is more than one Model at a given location – as with the Chlorine Models and theButadiene Models – then the names will be superimposed and may be difficult to read,although this will make it clear that there are multiple Models at the location.

6




Pinpointing an Individual Model

If you select a Model in the Study Tree and then select Pinpoint from the View menu (orpress the F4 key), the dot for that Model will become centred in the Map window andwill also be highlighted (i.e. displayed in a light turquoise colour). This allows you tolocate a specific Model, which is useful if you cannot identify the name for that Modelon the Map.

You can close the Map Window by selecting Close All from the Window menu.

Viewing Input Data

The section above introduced the main types of input data and their organisation, andthis section describes how to work on the details of the input data.

Opening the Input Dialog for the Chlor ine Rupture Model

Move to the Models tab section and double-click on the icon for the Model namedChlorine Rupture. The Vessel/Pipe input dialog will open as shown below.

The dialog contains a large number of input fields organised over sixteen tab sections,but many of these fields are relevant only to advanced modelling options (e.g. for asensitivity analysis), and you will typically only need to supply a small set of inputdata when defining a Model for use in an analysis, as you will see in the next chapter.

Input Dialog for the Chlorine Rupture Model

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Getting Help on the Input Data

This tutorial does not attempt to describe every item on input data, but the program issupplied with comprehensive online Help.

Every input dialog contains a Help button at the bottom right. When you click on thisbutton, the online Help will appear in a separate window, as shown.

The Help Window

The Help Window will be displaying a description of the current tab section, but youcan use the links inside the topic and the Contents, Index and Search tabs to reach anytopic in the Help system and gain a full understanding of the way that the input data

will be used in the calculations and the appropriate values that you should set for thehazardous events that you want to model.

Most dialogs also have a “What’s This Help” button inthe form of a question mark at the right of the title bar.

If you click on this button, the cursor willchange to a question mark, showing thatyou are in “What’s This Help” mode, and ifyou then click on a field in the dialog, apopup window will appear over the field,describing the field and giving advice on

setting values, as shown.There are some tab sections that appear in the input dialog for more than one Model.For example, the Material tab section is used for both the Vessel/Pipe Source Model,the User-Defined Source Model and the Bleve Blast Model. The Help is written in orderto give full guidance for either Model, so there may be references in the Help tofeatures that are not currently relevant to you.

After you have finished exploring the input dialog, click on Cancel to close the inputdialog without saving any changes you might have made. If you wish, you can moveto the other tab sections and explore the input dialogs for other types of data.

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Running the Calculations and Viewing the Results

In the Models tab section, select the Example Cases Study, and select the Models optionfrom the Run menu.

The program will process the calculations for each of the eighteen Models in turn,

performing the calculations for each of the three Global Weathers, and showing theprogress through the calculations. When the calculations for a given Model have beencompleted for all three Weathers, the name of that Model will change from black toblue, which is the colour-coding that the program uses to show that a Model has runsuccessfully and has a complete set of results. The calculations will take severalminutes to complete, depending on the speed of your machine.

You do not have to run the calculations for all Models and all Weathers. If you select asingle Model or folder, then you can run the calculations just for that Model or for theModels in that folder, or you can select Batch/Weather Setup from the Run menu to selectModels across different folders or to select only specific Weathers. The selection ofWeathers in the Setup dialog will be used for all calculations, but the selection of

Models will be used only when you select Batch Run from the Run menu.

Viewing the Graphs for the Chlorine and Butadiene Releases

Select the Vessels or Pipe Sources folder andthen select Graph from the View menu, fromthe right-click menu or the toolbars. A dialogwill appear as shown, prompting you tochose the weather conditions whose resultsyou want to view.

If you had selected a single Model rather

than a folder with multiple Models, then thedialog would have checkboxes next to theWeathers instead of radio buttons, and you would be able to compare the results forseveral Weathers for that Model. If you choose a single Weather in this situation, thenthe graphs will have additional features that are not available when you are viewingthe results for multiple Models or Weathers.

For this example, select the F 1.5m/s Weather. This is the weather with the most stableconditions, and is likely to give the longest dispersion distances. When you click on OK there will be a pause of a few seconds, and then the Graph Window will open asshown in the space to the right of the Study Tree pane.

The Graph Window

9




The Graph Window will usually contain many tab sections, each with a different typeof graph. The tab sections included for a particular combination of Model will dependon the type of the Models (e.g. Vessel/Pipe Source Model or Fireball Model), on thetype of the materials (toxic or flammable), and on the details of the dispersion andeffect behaviour (e.g. whether or not liquid rainout occurs). The Chlorine andButadiene Models have graphs for cloud concentration, for pool vaporisation, for toxic

effects, for jet fire, fireball and flash fire effects, and for explosion effects.The Concentration Graphs

The first graph is of centreline concentration. This will be showing the results at thetime at which the cloud footprint covers the greatest area, which occurs at a differenttime for each weather.

The graph will initially be showing results only for the four Chlorine Models. In thedispersion calculations, the program uses an averaging time that takes into accountchanges in wind direction over the course of the release, to give an averageconcentration at a given location, and it uses different averaging times for toxic and forflammable materials, reflecting the different time-scales that are relevant to each type

of release. The concentration graphs always display results calculated with a specificaveraging time, which is displayed in the legend for the graph. The default averagingtime for this set of results is the Toxic averaging time, and the Butadiene Models werenot modelled with that time so have noresults to display.

To view the concentration results for theButadiene Models, you must change theselection of averaging time to display. To dothis, select Properties… from the right-clickmenu or the Graph menu to open the Plot

Properties dialog, and then move to theAveraging Times tab section as shown.

If you change to the Flammable AveragingTime, the graph will display the results forthe four Butadiene Models only.

The User Defined option will also beenabled, which shows that some of theModels have a user-defined averaging time defined in the Location tab section. In fact,all of them have such a time defined, and if you select User Defined as the averagingtime for the graphs, the graph will display results for all eight Models.

Results Displayed on the Map

After the six tab sections that show the results in terms of concentration, the next tabsection is the Map graph, which allows you to view different types of effect zonessuperimposed on the map.

When you first move to the Map tab section, the Map graph will be displaying CloudFootprint results for a concentration of 10,000 ppm for the Toxic averaging time, andthe only results displayed will be for the Chlorine Rupture and Chlorine Liquid Leak Models.The other Chlorine Models don’t produce this concentration level at the default heightof ground level – as you can see from the Sideview graph – but if you open the PlotProperties dialog, move to the Distance tab and set the Height to 10 m, results for the

Chlorine Vapour Leak Model will also appear in the plot.

10




The Footprint concentration results are thedefault form of results for the Map graph,but the Event field in the Display tab sof the Plot Properties dialog allows you tochange to a different form, as shown. Thelist of types of effect will depend on the

types of Models that are covered by theGraph, and will be similar to the range oftab sections in the Graph window.

ection

upture

If you select Toxic effects, then theRadiation/Toxic field will become enabledand you can choose between dose, probitand lethality results.

If you view the Lethalityfootprint on the Map, you willsee that the Chlorine Liquid Leak

gives the greatest downwindeffect distance for lethality. TheRupture Model produces higherpeak concentrations at anygiven downwind location, butthe short duration of the rmeans that the total dosereceived is lower than for theleak.

The Map graph initially showsthe effect zone with a northerlywind, but you can choose Wind

Direction from the Graph menu orthe right-click menu to changethe wind direction.

The Pool Vaporisation graphdoes not show any hazardous effect distances, but the Toxic graph and the various Fireand Explosion graphs all include footprint-results of the form shown on the map, andmost of them also include graphs that show the effect-level along the cloud centre-lineas a function of distance downwind (e.g. radiation level for a jet fire, or lethality for atoxic release).

If you look through the Fire and Explosion graphs, you will see that the greatestdownwind effect distance is reached by the Late Explosion Worst Case for the Butadiene

Rupture Model, which reaches a distance of about 880 m downwind. A late explosion isone that occurs after the cloud has started dispersing away from the release point, andby default the explosion is assumed to be centred at the cloud front, which means thatthe explosion radius will reach beyond the flammable region of the cloud. Theprogram calculates the results for such an explosion at regular intervals, and the WorstCase graph displays the results for the ignition-time that gives the greatest downwindeffect distance.

11




Viewing the Reports for the Butadiene Rupture Model

The program also presents results in the form of reports. If you wish you can view areport that covers multiple Models – e.g. a report for all of the Chlorine and ButadieneModels – but if you want to compare the report-results for different Models it is easierto view separate reports for each Model and compare between two reports.

To view the reports for the Butadiene Rupture Model, select the Model and then selectReport from the View menu or from the right-click menu or the toolbars. After a pause ofa few seconds, the Report Window will open to the right of the Study Tree pane asshown. The Report Window will probably hide the Graph Window, but you can usethe options in the Window menu to move between the windows. You can have anynumber of Graph Windows and Report Windows open at the same time.

The Report Window

As with the Graph Window, the Report Window will normally contain several types ofresults, presented in different tab sections. A given tab section will present the resultsfor all of the weather conditions that have been processed for the Model.

For the Butadiene Rupture Model, the first tab section is the Input tab section, which liststhe input data. The Audit tab section gives version details for the program, forparameters and materials, but all of the other tab sections give details of theconsequence results that you saw summarised in the Graph window:

The Summary ReportThis report summarisesthe maximum downwinddistance to different typesof effects, and gives adirect comparisonbetween the differentweather conditions. Forthe Butadiene Rupture, D 5m/s is the weather that gives the greatest distances, although thedifference between the three weathers is small.

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The Discharge Report

This gives details of the discharge modelling, and the condition of the releaseimmediately after expansion to atmospheric pressure – which is the condition used forthe start of the dispersion calculations.

This report and all the other results-reports give the results for each weather in turn.

The Summary report is the only report which presents a direct comparison between thedifferent weathers.

The Dispersion Report

This report contains a table which describes the location and state of the cloud at aseries of time-steps during the dispersion. You might refer to this report if you wantedto understand a particular aspect of the dispersion behaviour in greater depth.

The Commentary Report

This report highlights themain events in the course ofthe dispersion, and allowsyou to see easily if and whendifferest types of behaviouroccurred, e.g. touch-down onthe ground, or the rainout ofliquid droplets.

The Averaging Times Report

The centreline concentrations given in the Dispersion and Commentary reports are allcalculated using a “core” averaging time that is set in the Dispersion Parameters andthat has a default value of 18.75 s. The Averaging Times report gives the centrelineconcentrations at a series of steps during the dispersion, calculated using alternativeaveraging times.

For the Butadiene Rupture these alternative times are the Flammable Averaging Time(whose value is set in the Flammable Parameters) and the User-Defined AveragingTime (whose value is set in the Location tab section for the Model). In this analysisboth of these times are also set to 18.75 s so for all the Butadiene Models the AveragingTimes report gives the same concentrations as the other reports. However, if youviewed the report for one of the Chlorine Models, you would see results for the ToxicAveraging Time (whose value is set in the Toxic Parameters), and which has thedefault value of 600 s.

The Fireball Report

The Fireball report gives radiation results for a fireball resulting from immediateignition of the released material. The report first gives a description of the fireballflame (emissive power, liftoff height, etc.), then it gives the dimensions of the ellipticaleffect zones for up to five different radiation levels – where the levels are set in theFireball tab section for the Model – and finally gives the radiation levels at a series ofpoints downwind from the centreline of the release.

The Jet Fire and Pool Fire reports have a similar form, giving the same three types ofresults.

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The Early Explosion Report

For Butadiene Rupture, the tab for the Early Explosion report is named Early Expl.(TNT), andthis is because the explosion method selected for this Model is the TNT method. Thereare three methods available, and you select between them in the Flammable tab sectionfor the Model. The TNT method is the simplest, requiring the smallest amount of inputdata, and it is the default method.

The report is similar in form to the Fireball report, giving the dimensions of the circulareffect zones for up to five explosion overpressures – where the overpressures are set inthe Explosion Parameters – and also giving the overpressure levels at a series of pointsdownwind from the centreline of the release.

The Late Explosion Report

This report gives the overpressure effect distances for late explosions occuring at arange of times during the dispersion. For each ignition time, the report gives thelocation of the cloud-centre, the location of the centre of the explosion, the downwinddistance to up to five overpressure levels, and the flammable mass in the cloud at the

time of the explosion. By default the centre of the explosion is taken as the cloud frontto 50% of the LFL, but you can change this setting in the Explosion Parameters.

Results for Two Time-Steps in the Late Explosion Report

The ignition-time that gives the greatest downwind effect distance is the one presentedin the Worst Case Late Explosion graph, as described in the section above.

The range of reports presented for a particular Model will depend on the type of Modeland on the behaviour of a release, and there are additional reports that do not appearfor the Butadiene Rupture Model. For example, if the material is toxic then there will be aToxic report with a table of dose, probit and lethality results as a function ofdownwind distance, and if the liquid in the release rains out to form a pool, then therewill be reports describing the spreading and evaporation of the pool and describing theseries of “dispersion segments” used to represent the vapour produced from the pool.

For most of your work with the program you will probably refer mainly to the graphs,since they present the results in the most direct form and allow easy comparisonbetween different Models and Weathers.

After you have finished examining the results, you can use Close All from the Windowmenu to close the windows.

14




Viewing the Results for the Chimney Release and Long Pipeline Models

The other two Vessel/Pipe Source Models in the PHAST Example Study Study Folderillustrate some of the special modelling features that are available.

The Chimney Release Model

This models a release of methane from a chimney stack on top of a building, and takes

into account the effects of t

If you view the graphsfor the Mod

he building wake on the dispersion.

el for all

p,

ne of lowulls

nce,

not

s that the plumes never approach closer to the ground than

nd

n a

of a 250 m propane pipeline that has a pumped flowrate of 10

the

the graphs for the F 1.5m/s weather. For this analysis the

ab. This contains a

the most important variable.

three Weathers and thenmove to the Sideviewgraph, you will see anoutline of the buildingwith the chimney on toand with the threeplumes emerging from

the chimney.The building wakeproduces a zopressure, and this pthe plumes downwards.The model deals with this by adjusting the height at a specific downwind distawhich is 100 m in this case. In some situations the plume may be pulled down lowenough that all or part of the plume is entrained in the building wake, but that hasoccurred for any of the weathers for this Model.

The Sideview graph show

about 58 m, but if you look at the Explosion graphs and the Flash Fire graph, you willsee Worst Case Late Explosion distances of over 900 m, and Flash Fire distances ofabout 600 m to 50% of the LFL. When performing the modelling of late explosions aflash fires, the program can calculate the flammable footprint of the cloud either at thecloud centreline or at a specific height. The centreline method is selected by default inthe Flammable Parameters since this will give the most conservative results, but youshould check the Sideview graph and make a judgement about whether or not theeffect zone would actually reach the areas of interest for your analysis. A flash fire iplume 60 m in the air would not affect people on the ground, but an explosion in sucha plume might well produce significant overpressures at ground level.

The Long Pipeline Model

This models the rupturekg/s, where the rupture occurs 100 m downstream from the pump. The programperforms discharge modelling for the complex, time-dependent flow regime insideruptured pipeline and then performs dispersion modelling for a representativeaveraged discharge rate.

Select the Model, and viewdischarge calculations are the same for all weather conditions, so you only need toview one weather if you are only interested in the discharge results.

The first tab section in the Graph window will be the Long Pipeline t

large number of sub-tabs, each of which shows the behaviour of a particular dischargevariable against time. Move to the Flowrate sub-tab, since this shows the behaviour of

15




The Flowrate graphappears to show theflowrate d

ropping instantly

wn.lt to

Automatic Scaling and set the Maximum Time to

about 45 s to drop to

of

m lines show the pumped inflow into the section, which isro for Section B, and the two Orifice lines show the flow

e

owever, at 9 s the flash-front reaches the end of section A, and from this

the

roceed to model the depressurisation of the section until it has emptied

from about 230 kg/s toabout 10 kg/s, as shoHowever, it is difficu

tell whether or not the dropis instant because thedefault scale on the timeaxis goes up to nearly amillion seconds. To see theinitial behaviour in moredetail, you must set thescale yourself.

Select Scale and Labels from thdialog, then uncheck the option for60 s.

e right-click menu or the Graph menu to open the Scale

With the changed scale,you can see that the ratetakesa steady rate of 10 kg/s,which is the pump rate.

There are five lines plottedon the graph, and theirmeaning may not beimmediately obvious. Thetwo A lines describe the 100m pipe-section upstreamthe rupture, the two B linesdescribe the 150 m sectiondownstream of the rupture, atwo sections. The two

nd the Total line is the sum of the rate released from theUpstrea

10 kg/s for Section A and zefrom that section at the point of rupture. If you want to hide any of these lines (e.g. thUpstream lines), open the Plot Property dialog and deselect the lines in the Long Pipe tabsection.

For the first nine seconds, the orifice flowrates from both sides are almost identical, as

the flash-front travels along each section at a similar speed, giving a similar flow-regime. Hpoint onwards the pressure profile in that section is maintained at the profile producedby a pumped flowrate of 10 kg/s; the program stops the discharge calculations forSection A at this point which means that there are no results available to display ongraph after 9 s, but the 10 kg/s flow from Section A is added in to the Total, as you cansee.

If you move to the Distance sub-tab, you can see that the flash-front reaches the end ofSection B after 14 s. However, the calculations do not stop for Section B at this point,and pcompletely at 45 s.

16




If you view the Discharge report for the Model, you will see that the average rto represent the beh

ate usedaviour is 10.5 kg/s, taken over a time-scale of one hour. This may

underestimate the hazard produced by the release, and there are options available forrepresenting a time-varying release with more than one “release segment” so that youcan investigate the significance of the type of short-term behaviour seen in this release.These options are described in more detail in the next chapter.

Viewing the Results for the Other Models

The other eight Models in the Study Folder are not Source Models. Each models onespecific type of behaviour and will produce a fixed set of graphs and reports.

The Warehouse Fire Model

This models a fire in a pesticide warehouse and you can define multiple scenarios foreach warehouse, where each fire scenario is defined by the surface area of pesticideinvolved and by the duration of the fire. There are special calculations that determinethe release rate and composition for the toxic plume produced by the fire, and thedispersion and effects of this plume are then modelled in the same way as for the toxic

cloud for the four Chlorine Models.The Three Flammable Models

The Pool Fire, Fireball and Jet Fire Models perform the same type of radiation modelling asthat associated with a Source Model, but they give you more control over the definitionof the flame and they also allow you to specify in more detail the locations for whichyou want to calculation the radiation levels.

The Four Explosion Models

The Baker-Strehlow, Multi-Energy and TNT Models perform the same type of vapour-cloudexplosion modelling as that associated with a Source Model, but they give you morecontrol over the definition of the flammable cloud and of the results-locations.

The BLEVE Blast Model calculates the overpressure levels produced by the rupture of avessel under flame impingement, which is a type of explosion modelling that is notperformed for a Source Model.

The form of the results for all of these Models is similar to the correspondingdispersion, toxic, fire and explosion results for a Source Model, and you should findinterpreting the graphs and reports very straightforward.

You have now seen the main features of PHAST. When you are ready you shouldproceed to Chapter 2, which takes you through the stages in setting up your ownanalysis.

17



Chapter 2:Setting up your own Analysis

Chapter 2Setting up your own Analysis

m of the AnalysisThe For

This chapter will guide you through the process of setting up a Study Folder for

The Models Defined in the Analysis

iquid side of a vessel containing a toxic materialthe gas side of a vessel containing a toxic material

t.

wagon.

efine different events, or change the input values ins

.

Creatin

performing consequence calculations. The tutorial supplies all of the input values thatyou will need to complete the analysis.

The main aim of the analysis is to show you how you can define Models to representthe most common types of hazardous event, and how to take into account the mainvariables. The types of hazardous event that are considered in the analysis are asfollows:

• A rupture of a vessel containing a toxic material

•

A pipework leak from the l• A pipework leak from

• The equivalent three releases for a vessel containing a flammable material

• The rupture of a propane tank wagon under normal operating conditions.

• A fireball or BLEVE of the propane tank wagon as a result of fire impingemen

• A liquid leak from the body of the propane tank

If you wish, you can omit events, dorder to define conditions that are more typical of your facility. However, if you do thiyou will obtain results that are different from those that will be shown in this manual

g a new Study Folder

To create a new Study Folder, select New from the File menu or the Toolbar. Theprogram will close the PHAST Example Study Study Folder and a new Study Folder will

Savin

h a

As… from the File menu. The File Save dialog will appear and

you should locate the DNVuser folder (the default location for savingStudy Folder files), use the Create New Folder option to create a folder withyour name, and then save the new file to this folder with the name Tutorial and thedefault file format of *.psu.

open, with a name shown as “Untitled”.

g the Study Folder

You cannot save the Study Folder with the name “Untitled” and should save it witreal name immediately.

Select Save

18




The Contents of a new Study

New Study data set up:

A Global We

those in the PHAST Example Study Study Folder.

Setting up the Map Dat

Folder

Folder files are not empty but will have some default

ather Folder containing three Weathers

The weathers are the same as

A Set of Default Parameters

As with the PHAST Example Study Study Folder, there is a set of Global Parameters, all ofwhich are using the default values.

a

The tutorial uses a map of an area near two rivers, in a country which has a nationalgrid system. The image for this map is supplied with the program the form of a *.ti

If you haf file.

ve an image file for the area around your facility, you might prefer to use thatinstead.

Insertin h

Ima erima sprodef d

The ropro s deals only with raster

et in the Map tab section

eady contain a Raster Image Set icon, select the Tutorial

de the Set

will appear as

n you firstbrowse to this folder you will not see anyfiles, since the list of File types is not set to*.tif by default.

When you have selected a valid raster image file, the Placement Mode fields willbecome enabled; these are options for specifying the map co-ordinates covered by theimage. Some files contain georeference data or header data that you can use to set the

co-ordinate data for the image, but thetutorial.tif

file does not and the only optionavailable is the Interactive option, which is available for any raster image file.

g t e Raster Image

ge files that contain a description of each pixel in the image are known as rastge , and most common image files are in this form, e.g. *.tif , *.bmp, *.gif files. Thegram can also display map data taken from a GIS Database, where an image isine by describing the lines that form the image.

p cess of inserting a raster image into a Study Folder is very different from theces of inserting a connection to a GIS Database. This tutorial

images, and you should refer to the online Help for details of working with GISDatabases.

The process of inserting the raster images involves several stages.

Ensure that there is a Raster Image S

If the Map tab section does not alricon at the top of the tab section, and use the Insert menu to insert a Set.

The Set is a folder for raster images, and you have to insert raster images inside such afolder.

Insert a Raster Image insi

Select the Set, then select Raster Image fromthe Insert menu. A dialogshown, and you must browse to locate the

image file. The tutorial.tif file is located in theExamples folder for the installation of theprogram (which is typically under Program

Files\DNVS\PHAST_6_5). Whe

19




Selecting a Co-ordinate System for the Map

emg a co-ordinate system for thee Placement Mode is set to

nalysis.teractive Placement Mode and will not be connecting to a

in this tutorial - you can click on Cancel in the

The Wizard dialog contains a button, and this gives you a quick way of viewing anefinition of co-ordinate systems in PHAST.

will then open to the right of the

the image covered by the image; if the menu bar does not include a Map option,e

es for Edit Dialogs

in the national co-ordinate system for theby the map are six-digit numbers. Byificant figures of any number that you are

have entered

ificant figures, select Preferences > General menu and move to the Miscellaneous tab. The first field in the tab

ake

flues

When you click on OK in the Place dialog, a dialog called the “Co-ordinate systwizard” will open; this is the first step in selectinanalysis. It is only essential to select a system if thGeoreferenced or to By Header, or if you want to use a GIS database in the aWhen you are using the In

GIS database – which is the situationWizard dialog and leave the co-ordinate system undefined.

Help

overview of the user and d

Placing the Image in the Map Window

When you click on Cancel in the Wizarddialog, there will be brief pause and the MapWindowStudy Tree pane.

The cursor will be in the form of crosshairs,and you must drag and drop to place theimage in the window. This sets the initialvalues for the map co-ordinates for theimages, which you will set to the correctvalues in the next step.

Setting the Co-ordinates and Size of the Image

Double-click on the tutorial icon to open the input dialog forthe image, move to the Geometry tab section, and set thevalues shown. The origin for a map image is the top-left

corner, and the values are in the national co-ordinate systemfor the country.

When you click on OK the image will probably disappearfrom the Map Window because it has moved to a location beyond the scope of thewindow. Select Fit > All from the Map menu, and the Map Window will change todisplayclick on the Map Window to mak sure it is selected, and the Map menu will appear inthe menu bar.

Setting a Large Number of Significant Figur

The co-ordinate values for the image will becountry, and the values for the area covereddefault, input dialogs display only four signediting, and with this setting you will find it difficult to be sure that youthe co-ordinates.

To change the setting for the number of signfrom the Options

section is the Number of significant figures for edit windows, and you should msure that this is set to six or more.

Click on OK to close the General Preferences dialog and return to the Map tab section. Iyou open the dialog for the raster image again, you will be able to see that the vathat you entered were stored in full.

20




The Location of the Site on the Map

For the tutorial, the facility occupies the long, narrow section of land to the north awest of The Village, between the east bank of the river and the road that runs pato the river, shown shaded yellow in the illustration.

ndrallel

The Location of the Facility on the Map

Definin Ruptureg the First Model: for a Toxic

In the Tutorial.psu Study Folder, move to the Models tab sectiodefine represents the rupture of a vessel containing a toxic material, which is one of

several Models dealing with a toxic material.The vessel is a sphere with a radius of 3.37 m and volume of 1fill-level of 85%,

n.

20 m3 and a maximumcontaining chlorine at saturation conditions and ambient temperature.

ated 4 m above the ground.

Inser

the name “Toxic”. You will place all of the Models that represent toxic

Turn

ked on the Map to set the location for the Model.

The first Model you will

The sphere is located near the centre of the site and is elevThere is no bund surrounding the sphere.

t a Folder to Group Toxic Releases

Select the Study icon, then select Folder from the Insert menu or the toolbar to insert afolder. Use Rename from the Edit menu or the right-click menu (or press the F2 key), andgive the folderreleases in this folder.

on the Option to Insert Models on the Map

In the Options menu, select the option to Insert Models on Map. By default this option isturned off, and when you insert a Model the icon will appear immediately in the StudyTree. If you turn the option on, then the Model icon will not appear in the Study Treeuntil you have clic

In this tutorial you will insert the Models on the Map in approximately the correctlocation, and then correct the location as necessary in the input dialog.

21




Insert a Vessel/Pipe Source Model

already open and the cursor will turn tocrosshairs., and you should click at a point near

the centre of the site as shown to place theModel.

After you have clicked, an icon will be added tothe Study Tree, and a dot will appear on theMap to show the location of the Model. Renamethe icon to Cl2 Rupture.

The icon will have a red border around it, showing that it does not have a full set ofinput data. You will not be able to run the consequence calculations for the Model untilyou have supplied values for all of the mandatory input fields, as will be describedbelow.

You use the Vessel/Pipe Source Model when you want to perform dispersion andeffects calculations for a release from containment and you want to use the program’sin-built discharge calculations to determine the state of the material after expansion toatmospheric pressure, which is the state required for the start of the dispersioncalculations.

d the “User Defined Sources, but instead allows you to

Setti

datory field: you must supply a value forn the calculations for a Model that has any

n at any point.

esent the vessel

Select the Toxic folder, then select Vessel or Pipe

Source from the Insert menu or the right-clickmenu. The Map window will open if it is not

The program contains a second Source Model which is calleModel”. This Model does not perform discharge calculationspecify directly the state of the material after expansion to atmospheric pressure. Youuse it if you want greater control over the inputs to the dispersion and effectcalculations, as will be described later in this chapter.

ng the Input Data

Double-click on the icon for the Model to open the input dialog.

All of the fields in the first tab section are blank, and those that are enabled have redborders . A field with a red border is a mansuch a field, and you will not be able to rumandatory fields unset.

This section describes each tab section in turn, including those that are not relevant tothis particular hazardous event. Click on the Help button to open the online Help if youwant further informatio

The Material Tab Section

To set the Discharge Material, click on the button with three dots to the right of theDischarge Material field, and select CHLORINE from the list that appears. The listcontains all of the materials that are defined in the System Materials.

The vessel is a sphere with a volume of 120 m3. This Model will reprwith the maximum degree of filling, which is 85%. Select Volume as the method ofspecifying the Inventory, and enter a value of 102 m3.

22




23

The chlorine is held under saturation

Saturated Liquid from the first

ropdown list, and set the Temperature cursor away from the Temperature field the

will calculate the saturation pressure for this temperature and display it in the

at is not held under saturationst select both Temperature and Pressure

values for both.

the type of hazardous

one Scenario

insulated

e dispersion calculations will start with thereleased from the ventilation system.

The Vessel Tab Section

All of the fields in this tab section are disabled when the scenario is set to Rupture. Forall of the other scenarios, some of the fields in the tab section will be enabled, with thecombination depending on the scenario as you will see later.

conditions at atmospheric temperature.The temperature will vary depending onthe season and time of day, but for thisModel a value of 10oC will be used asrepresentative. To set these Process Conditions, choose

dropdown list and Temperature from the second dto 10 degC, as shown. When you move theprogramPressure field.

To define the process conditions for a material thconditions (e.g. a gas or a padded liquid), you mufrom the lists and give

The Scenario Tab Section

You use this tab section tospecify

event you want to model. Therange of types available willdepend on the processconditions you have specified.

There is onlyType available for modellingthe rupture of a pressurisedvessel; this is CatastrophicRupture, which is selected bydefault. The other scenarios are

either longer-duration releases,or applicable only totanks.

The vessel is out of doors, soyou can leave the Outdoor /

In-Building fields with thedefault selection of Outdoor. Ifyou select In-BuildingRelease, the program willmodel the build-up ofconcentration inside the building and thstate of the plume as it is

The other fields in the tab section are not relevant to a rupture scenario. You can takethe default settings for all of the fields in this tab section.

The Pipe Tab Section

All of the fields in this tab section are disabled when the scenario is set to Rupture.They are relevant only to the Line Rupture, Disc Rupture, Relief Valve and Long

Pipeline scenarios, as you will see later.




24

at this to 7.37 m, which is the elevation of the

et the East co-ordinate to 198492 m, and the

field below the concentration will acquire a red border, showing that it

e Toxic a00 s.

s you to select additional averaging times for which youou make any selections in the final section of the tab, theveraging Times report, as you saw in the previous

essel and you want to take this into account in theand evaporation, you can check the Bund exists box and

nd. For this sphere there is no bund, so you can leave theues.

on are disabled then the scenario is a catastrophicfields are enabled for the longer-duration scenarios as

e enabled for in-building releases.

are disabled when the material is toxic only. For au to choose between the three models for a vapour

choose between two models for jet fires.

tion

ulations are set to Unselected performed), but for this

outing

tration is lower outdoors than indoors. Byill be taken from the Toxic parameters tab section for the Model,Speed Dependent for the , then the values

The Location Tab Section

First, set the release coordinates. The Elevthe System Parameters, but you should secentre of the sphere above the ground. SNorth co-ordinate to 435063 m.

The program requires a criterion for stopping the dispersion calculations: either amaximum distance, or a minimum concentration. For this tutorial, set theConcentration of interest to 100 ppm. When you set this concentration, the Usesaveraging time

tion has a default value of 1 m, taken from

is mandatory; you must specify the averaging time to be used in the calculations forstopping the dispersion. For a toxic release, the list allows you to choose the Toxic averaging time or the times associated with the ERPG, IDLH or STEL measures of toxicity,or to specify a User-defined time.

For this release, select th veraging time, which is set in the Toxic Parametersand has a default value of 6

The Location tab section allowwant concentration values. If yresults will be appear in the Achapter.

The Bund Data Tab Section

If there is a bund around the vmodelling of pool-spreadingenter a description of the butab section with the default val

The Indoor/Outdoor Tab Section

All of the fields in this tab sectirupture outdoors. Some of theyou will see later, while others ar

Flammable Tab Section

The fields in this tab sectionflammable release, they allow yocloud explosion, and to

The Toxic Parameters Tab Sec

The fields in this tab section are used in

modelling the buildup of toxic concentrationinside a building, and the exposure of a personinside the building.

By default, these calc(i.e. they will not betutorial you should change them to Selected. The calculations require information abthe ventilation-rate for the building and about how long people remain in the buildafter the cloud has passed and the concendefault these values wbut if you choose Wind Ventilation Specification

will be taken from the data for the Weather, which means that the values may bedifferent for each weather.




For this tutorial, leave the Ventilation Specification with the default value of Case

r cloud explosion.

the

ab Section Input Field Value

Specified, and take the default values for the Building exchange rate and the Tail time.

The TNT, Multi Energy and Baker Strehlow Tab Sections

The fields in these tab section are disabled when the material is toxic only. They areused in the modelling of a vapou

The Discharge Parameters Tab Section

The fields in this tab section are always enabled, and take their default values fromSystem Parameters. They are used in the discharge modelling for the Line Rupture,Disc Rupture and Relief Valve scenarios, so are not relevant to this Model.

The Jet Fire, Pool Fire and Fireball Tab Sections

For a flammable release, these tab sections allow you to choose between options formodelling each type of flame.

A Summary of the Input Data

The input process involves examining a large number of input fields, but the numberof values that you have to enter in order to complete the data for this Model is small, asshown in the table below:

T

Discharge Material ChlorineMaterial

Inventory 102 m3

Process Conditions Saturated Liquid at 10oC.

Elevation 7.37 m

East Co-ordi

Location

nate 198492 m

North Co-ordinate 435063 m

Concentration of 100 ppminterest

Uses averaging time Toxic

Toxic Indoor Toxic Selectedparameters Calculations

The default scenario for a Vessel/Pipe Source Model is a catastrophic rupture odoors, so there is no need to change any settings in the Scenario tab section for thisparticular Model.

ut of

tings, the inputshould see that the icon no longer has

nput data.

If you have made all of these set data for the Model are now complete,and you can click on OK to close the dialog. You

a red border, showing that it has a full set of i

25




Run

e weathers.

nswant more information about the

e cloud, you should view either the Commentary

y

ethality graph shows that the greatest

l of 10%. The indoor effects for this weather reach aboutt downwind effect distances are for D 5 m/s

t 1.3 km for a lethality level of 10%.

Definin

the Calculations and View the Results

Select the Model and select Run Model from either the Run menu or the toolbar. When thecalculations are complete, view the graphs for all of th

You will see that there is no Pool Vaporisation tab in the Graph Window, which meathat the liquid in the release did not rain out; if you

behaviour of the liquid droplets in thReport or the Dispersion Report.

The concentration graphs only ever show the outdoor concentration, but if you moveto the Toxic tab section you will see that the Probit, Lethality and Dose graphs displaseparate results for indoor and outdoor effects, and that there are separate Footprintgraphs for outdoor and indoor effects. The Ldownwind effect distance is for the F 1.5 m/s weather outdoors, with a distance ofabout 2.5 km to a lethality leve2.25 km to 10% lethality. The shortesindoors, which reaches abou

g the Second Release: Toxic Liquid from Pipework

The second release is from the same chlorine sphere, but the hazardous event is therupture of a one-inch liquid line attached to the bottom of the sphere, where the initialliquid h be 4.6 m vertically downwards to 10 cm from theground, then 5 m horizontally to an isolation valve; the rupture is assumed to occur just before the isolation v

Copy the First Model

Much of the input data f re is also applicable to the pipework failure,so you can use copy and t menu or the right-click menu to create a

copy of the Rupture Mode folder copy the name Cl2 LiquidPipework.

Setting the Input Data

Open th og an ut data as follows:

he same as for the rupture.

be Released to Liquid.The line rupture scenario models the full-bore rupture of pipework attached to avessel, and the discharge calculations take into account the effect of friction in the flowfrom the vessel to the point of rupture. To model a release from the body of the vessel,with no frictional losses in the discharge, you would choose the Leak scenario.

When the vessel contains saturated liquid, you will be offered a choice of release-phasefor the line rupture scenario: a vapour release from the top of the vessel, or a liquidrelease from the bottom of the vessel. The list of phases includes “two-phase”, but thisis only enabled for the disc rupture and relief valve scenarios, for modelling over-filling of the vessel.

ead will . The line runs 4 m

alve.

or the vessel ruptuEdipaste from the

l, also in the Toxic . Give the

e input dial d set the inp

Material Tab Section

Leave this tab section with the same values as for the rupture, since the material andprocess conditions are t

Scenario Tab Section

Set the Scenario Type to Line Rupture, and the Phase to

26




Pipe Tab Section

The Pipe Length is the length ofpipework between the vesseland the point of rupture, andyou should set it to 9 m asshown.

To set the Internal Diameter to one inch, click on “mm”

ve

d

be enabled

with the initialuration

red to

normally

st supply

resent

heing selected, then examine the results and decide on the most

appropriate way to represent the behaviour for the rest of the consequence analysis.

to the right of the field, and then select “in” from the listof units that appears as shown. You can then enter thediameter directly in inches, rather than having toperform the conversion yourself into the default unit ofmm.

Leave the pipe roughness with the default value taken from the System Parameters.The number of valves is used in the modelling of frictional losses, and you can leathem as zero.

The other fields in the tab section are relevant only to the long pipeline scenario, anare all disabled for the line rupture scenario.

Vessel Tab Section

For the line rupture scenarioand most of the other scenariosthat involve a continuousrelease, the Time Varying

Release option willin the Vessel tab section.

If you do not check this option,

then the release will bemodelledrelease rate, and the dwill be the time requidrain the inventory at thisinitial rate. This willgive conservative results in theconsequence calculations.

If you select the time-varyingoption, then you mu

information about thedimensions of the vessel. Thedischarge calculations willmodel the effect of the releaseon conditions in the vessel andthe way that these conditions and the release rate change over time, and will repthese time-varying results either with a single rate (e.g. an average rate, or a rate at aparticular time) or with a series of rates, depending on your selection for the Rates

versus time.

For this release, you will perform an initial run of the discharge calculations with ttime-varying modell

27




Set the Liquid Head to 4.6 m, select tischarge to zero, and the Diameter to 6.74 m. Leave

Average rate with an averagingo make a final selection after you have viewed the

ab Section

d form a vaporising pool.

pture. In reality, the release- of the sphere but this

ces for chlorine and can bed

hanged, with no bund specified.

rupture you must specify the Direction ose Horizontal

pipework.

cludes a second horizontal option: Horizontal Impingement. Youif the release is in a congested area and the release is likely to

ipment; the program will reduce the momentum of theamount of air mixed into the jet during the initial stages.

Frequency of Bends to

ata for this stage, and you can click on OK to close the input

Runn lations

t Run Discharge from the Run menu, the right-click menudischarge calculations alone, without peforming thens. The calculations may take several minutes,

view the reports and move to the TV Discharge Report.

in two hours of release, so the time-varying behaviourThere are two options for bypassing the time-varying

uation:

sults to Create a User-Defined Source Model

te Source from the Edit menu or the right-

he Time Varying Release option, set the TankType to Spherical, the Height of D

the Rates versus time set to the default selection oftime of 3600 s; you can return tdischarge results.

Location T

Set the Elevation to 0.1 m. With this setting, the liquid drevaporate inside the cloud, and will probably rain out an

Leave the other fields with the same values as for the rulocation would be offset by a few metres from the centredifference is insignificant compared with the effect distanignore

oplets will probably not

Bund Data Tab Section

Leave this unc

Indoor/Outdoor Tab Section

For a continuous release scenario such as lineof the release. Cho from the list, which is the correct setting for this type ofunobstructed rupture of horizontal

The list of directions inshould select this optionimpinge on a wall or other equrelease, which will reduce the

Discharge Parameters

There is one bend in the 9 m of pipework, so you can set the0.11 per m.

This completes the input ddialog.

ing the Discharge Calcu

Select the Model and then selecor the toolbar. This will run thedispersion and effects calculatiodepending on the speed of your machine.

When the results are complete,

The rate drops by less than 3%can be ignored for this release.discharge modelling in this sit

1: Use the Averaged Discharge Re

When you performed the discharge calculations, the program calculated the averagerate over the first 3600 s, and this is the representative rate given in the DischargeReport. If you decide that you want to use this average rate rather than the initial rate,you should select the Model, then select Crea

click menu.

28




The program will show a list of the weather conditionsfor which you performed the discharge calculations andfor which it has results, and when you select one of theseweathers the program will create a User-Defined SourceModel with the name Calculated Discharge, as shown.

urce Model has many of the same tab

r-d

sults

Model and Deselect Time-Varying Release

the time-varying discharge modelling if youentire release, and this is the

r this tutorial. The discharge calculations for this Model will

The User-Defined So

sections as the Vessel/Pipe Model, but instead of theScenario and Vessel tab sections it has a Discharge tabsection in which you specify the discharge rate and conditions directly, since the UseDefined Source Model does not perform any discharge modelling itself. The Calculate

Discharge Model will be created with Discharge data taken from the averaged refrom the Liquid Pipework Model, but you can edit these values if you choose.

2: Edit the

This is the simplest method for bypassingdecide that you want to use the initial rate to represent themethod that will be used fo

run much more quickly with the time-varying option turned off.

After this adjustment, the final set of input data for this Model can be summarised asfollows, not including the values that are the same as those for the rupture model:

Tab Section Input Field Value

Scenario Type Line RuptureScenario

Phase Released Liquid

Pipe Length 9 mPipe

Internal Diameter 1 inch

Time-Varying Release? Not selectedVessel

Tank Head 4.6 mLocation Elevation 0.1 m

Discharge Parameters Frequency of Bends 0.11 per m

The default direction for a line rupture scenario ischange any settings in the Indoor/Ou

Horizontal, so there is no need totdoor tab section for this particular Model.

Run

hen the

ill have little effect on the dispersion or toxic

r

the Consequence Calculations and View the Results

Select the Model and select Run Model from either the Run menu or the toolbar. Wcalculations are complete, view the graphs for all of the weathers.

You will see that there is a Pool Vaporisation tab in the Graph Window, which means

that the liquid in the release did rain out. If you view the reports and look at theCommentary Report, you will see that rainout fraction is only about 1%, so theformation and behaviour of the pool weffects.

In the Toxic Lethality graph, the greatest effect distances are for the F 1.5 m/s weatheoutdoors, with a distance of 900 m to a lethality level of 10%, which is approximately athird of the distance reached by the catastrophic rupture. The least stable night-timecondition, D 5 m/s, reaches only 350 m for 10% lethality outdoors.

29




Defining the Third Model: Toxic Vapour from Pipework

The vapour release is the rupture of a two-inch pipe attachThe line runs 3.4 m horizontally, then vertically downwarassumed to occur 1 m from the ground.

ed to the top of the sphere.ds, and the rupture is

name the copy toCl2

Vapor

Create the Model as a copy of theLiquid Pipework

Model, rePipework, and change the input data as follows:


Scenario Phase Released Vapour

Pipe Length 13 mPipe

Internal Diameter 2 inch

Location Elevation 1 m

Indoor/Outdoor Direction Down – Impinging onthe Ground

Discharge Parameters Frequency of Bends 0.08 per m

When the phase is set to Vapour in the Scenario tab section, the Building Wake Effect

The release similar to that from the one-inchliquid li pipework r ry similar e

Defining Thre lammable Rel

fields will become enabled. The sphere is in an open area so building-wake effects arenot relevant to this release, and you can leave these options unchecked.

rate from the two-inch vapourne, and the two

line iseleases give ve ffect distances.

e F eases

There is a propane sphere at the far The prop here has the samedimens the chlorine sphere a pip s alsooperating under saturation conditio pheric temper

Setting the ta for the Mode

You can d the res by e three toxic-

harge

ngt and then typing “P”, which will take you to the first material with this initial

north of the site. ane spions as nd the same design of ework, and i

ns at atmos ature.

Input Da ls

define the rupture an two pipework failu copying thModels and simply changing the selection of discharge material and the eastern coordinates.

Copying the Models

Select the Toxic folder, copy and paste it, and name the copy Flammable. In the name foreach Model, change Cl2 to C3.

Changing the Material Selection

Open the input dialog, click on the button with three dots to the right of the DiscMaterial field, and change the selection from CHLORINE to PROPANE. The list ofmaterials is arranged alphabetically, and you can move quickly to PROPANE by clickiin the lisletter.

When you return to the Materials tab section you will see that the program hasrecalculated the saturation pressure at 10oC and also the mass for the inventory.

You must make this change for each of the three Models.

30




Changing the Location and Concentration of Interest

When you move to the Location tab section, you will see that the Toxic averaging time is

udedyou to make a different selection for the

want to concentratiovalue as low as 1 since thewill not zard once it hasbelow t er flammable limit o20,000 ppm. You could set thisconcentration yourself, but for aflamma an also leConcentration of interest blank, asshown, auto is culations once the

and

You must make this change for each of the three Models.

ose,

cted by defaulto you would normally only select them if you

– but you will do this in the Parameters instead of in the Model data, sinceant to set values that will be used by all

log for

he values set in the System

for

Finally, open the input dialog for the Fireball and BLEVE Blast Parameters, and set the

same values.

no longer set for Uses averaging time and that this field is now shown as unset andmandatory. The material is flammable only so the Toxic averaging time is not inclin the list, and the program is promptingcalculations of the stopping-concentration.

For a flammable release you would notcalculate the

00 ppm,n to a

clouddilutedpose a ha

he low f 2% or

ble release you c ave the

and the program will matically stop the d persion cal

concentration has reached a given fraction of the LFL as calculated with the Flammableaveraging time. By default the fraction is 50%, but you can change this in theFlammable Parameters if you prefer.

For this tutorial, delete the value for the Concentration of interest, and set the East

North coordinates as shown above.

Setting the Input Data for the Fire Modelling

If you move to the Jet Fire, Pool Fire or Fireball tab sections, you will see that threelevels of radiation intensity are specified, but that the calculations for radiation d

probit and lethality are all unselected. These calculations are not selebecause they can be time-consuming, sknow that you need them for a particular analysis or a particular Model.

For this tutorial you will set the lethality calculations to Selected and specify five levelsof lethalitythis is the most efficient method if you wModels.

Move to the Parameters tab in theStudy Tree, open the input diathe Jet Fire Parameters, and set the

Radiation Lethality data as shown.After you have clicked on OK to closethe dialog you will see that the Jet FireParameters icon no longer has a greenborder, which shows that not it is notusing tParameters for all of the fields.

Next, open the input dialog for the Pool Fire Parameters, and set the same valuesRadiation Lethality.

31




If you move to the Models tab of the Study Tree and look at the Jet Fire, Pool Fire or

Runn

all

eer

ts

gleons

xic

ection. The propane releases do notl Fire tab sections.

d effect distance shown in these graphs is just less than 25 m, which is there

results for more than one Model or more thansingle level, which will be the lowest level set for

ensity level, or the lowest lethality level). If youthen you must view the graphs for a single

lso contains three graphs. These are showing resultseans that the two Radii graphs are able to show the

pse for a lethality level of 100%, because the fireball does not

rameters).

Fireball tab sections for any of the flammable Models, you will see that the lethalitycalculations are now selected, with the five levels set.

ing the Consequence Calculations and viewing the Results

Select the Flammable folder and use the Run Models option to run the calculations for

three Models.You can also view the results for all threModels at once. Select the Flammable foldand then select View Graphs. A Plot Setupdialog will appear, prompting you for theWeather for which you want to view resulWhen you are viewing results for multipleModels you can only choose a sinWeather, so the Weathers have radio buttbeside them, whereas they have check boxesbeside them when you are viewing results for

a single Model. Select the 1.5/F Weather,which should give the greatest effectdistances for dispersion.

.

The Graph Window contains tab sections forConcentration graphs, as with the toModels, but it contains Jet Fire, Fireball andFlash Fire tab sections instead of the Toxic tab sproduce any liquid rainout, so there are no Poo

The main features of the graphs are described below.

Jet Fire GraphsThe Jet Fire tab section contains three graphs, which are presenting results for the twopipework failures. The first graph shows radiation level versus distance, the secondshows Intensity Radii to the lowest of the three radiation levels set in the Parameters (4kW/m2), and the third graph shows Lethality Radii to a lethality level of 1%, which isthe lowest of the five lethality levels that you set in the parameters. The maximumdownwindistance for 4 kW/m2 for the liquid

If a given Fire Radii graph is showingone Weather, then it will only plot a

that type of result (e.g. the lowest intwant to see results for all of the levels,Model and Weather.

Fireball Graphs

The Bleve (or Fireball) tab section aonly for the rupture, and this m

lease.

results for more than one level. The maximum downwind effect distance is about 560m, to a radiation level of 4 kW/m2, and the distance to a.lethality level of 1% is about290 m. There is no elliproduce the necessary radiation dose at the height of interest (set to ground level in the

Flammable Pa

32




Explosion Graphs

The two Early Explosion graphs contain results only for the Rupture, since immediateexplosions are assumed not to occur for continuous rel

eases. However, the Late

e greatest downwind distance for the lowest overpressure set in thegend for the Late Explosion Time graph

ccurs at 11.2 s.

loud at the time that it covers themaximum downwind effect distance ofework releases this gives a distance ofpm is 50% of the LFL, which is the

ters as the boundary of the flash fire

Al ter rly Explosions

e input data for the flammable Models you left thes, which means that the early explosion

t method, which is the TNT method.

Rupture Model that use the other methodse results.

Rupture.

e Model inside this folder and then create two copies of the Model.TNT, name the first copy Multi-Energy, and the second copy

location to

s for the Multi-Energy Explosion Method

Explosion graphs contain results for all three Models.

The Late Explosion Worst Case graph shows the effect radii for the explosion-time

which gives thExplosion Parameters (0.02 bar), and the legives the time at which the worst-case expldistances is 1,100 m, for the

osion occurs. The greatest downwind effectRupture, and it o

Flash Fire Graph

The Flash Fire Graph shows the zone for the cmaximum area. For the rupture, this gives a350 m to 10,000 ppm, whereas for the two pipabout 70 m to the same concentration. 10,000 pfraction set by default in the Flammable Parame

effect zone.native Methods for Modelling Ea

When you were setting thFlammable tab section with the default settingfor Rupture was modelled with the defaul

In this section you will create versions of thefor modelling early explosions, and compare th

Creating the Model Icons

Insert a folder inside the Flammable folder, and name it

Drag the Ruptur

Rename the original ModelBaker-Strehlow.

Setting the Inputs for the TNT Explosion Method

For the TNT Model, move to the TNT tab section to check the input data for themodelling.

You can leave the Explosion Efficiency with the defaultvalue, but for this Model you should set theGround burst, which means that you are assuming that the

explosion is sufficiently close to the ground that there will be reflection effects in thepressure waves.

Click on OK to close the dialog for the TNT Model.

Setting the Input

Open the input dialog for the Multi-Energy Model, move to the Flammable tab section,and choose TNO Multi-Energy as the Explosion Method.

Next, move to the Multi Energy tab section, where you can define up to seven regionsof confinement within the cloud and also specify the strength of an explosion in theunconfined regions of the cloud.

33




By default there are no confined regions selected, which means that there are no

e propane sphere is

section,

option to have theeed of the flame (rather

Flame Expansion

ves off the ground, so you should setof th

hen view the graphs for the 1.5/F

el produces a peak pressure of 1

gion of the cloud, for which the peak overpressure isonly about 0.02 barg.

mandatory fields in the tab section and that the Model will run even if you do not setany values in the tab section – but it also means that by default the Model will notproduce any explosion results.

For this tutorial you will define threeregions of confinement, each occupying

30% of the volume of the cloud, and witha range of confinement strengths between6 and 8, as shown. Values of 8 and 9 aretypically used for process units, but theregion around threlatively open.

The strength of an explosion in theunconfined region of the cloud will be 2,as shown.

Click on OK to close the dialog for the Multi-Energy Model.

Setting the Inputs for the Baker-Strehlow Explosion Method

Open the input dialog for the Baker Strehlow Model, move to the Flammable taband choose Baker Strehlow as the Explosion Method.

Next, move to the Baker-Stehlow tab section. This tab section contains manymandatory fields, and you must complete this tab section before you can run theModel.

For this tutorial, use theprogram calculate the spthan supplying it yourself). For a propane release

you should set the Material Reactivity to Medium,and for this release you should set the number ofdimensions for the to 2, and theObstacle Density to Medium, as shown.

The release is relatively close to the ground andthere is likely to be some reflection of thepressure-wathe Ground Reflection Factor to 1.6. Finally, the volumeinvolved in the explosion is 500 m

e cloud assumed to be3.

Click on OK to close the dialog for the Baker-Strehlow Model.

Running the Calculations and Viewing the Results

Select the Rupture folder, run the calculations, and tWeather.

In the Early Explosion Distance graph, the Baker-Strehlow Model has the highest peakoverpressure, of about 1.02 barg, but the pressure declines rapidly with distance andthere are no effects beyond about 300 m. The TNT Modbarg and the pressure declines less rapidly with distance, so the pressure at 300 m is 0.2barg, and there are effects out to 1,400 m. For the Multi-Energy Model, the graph showsresults only for the unconfined re

34




However, in the Early Explosion Radii graph the results shown for the Multi-Energy

Model are those for the worst case, and in this comparison the Multi-Energy Model givesthe greatest effect distances of the three Models, with a distance of about 2 km to 0.barg.

02

rgy

Early Explosion Distance results for each of

that the over-pressure levels close to thent on the value that you set for the strength of

e default TNT method gives results that areh a medium strength of confinement (i.e. with a

sonable – and simplest - to take the default method as

Flammable Releases from a Rail Tank Wagon

If you view the graphs for the Multi-Ene

Weather, you will be able to see separate

the regions in the cloud. These results showrelease are very strongly dependeconfinement.

This analysis shows that, for this release, thclose to the multi-energy results witstrength of 7). It seems rea

Model on its own and select only the 1.5/F

representative for this analysis.

The propane is delivered to the facility by tank wagon from a marshalling yard 10 kmlving two tank wagons, and

der the same conditions as in theC).

g leaks during the unloading process. This tutorial will consider only theco

pture of a wagon under flamele the wagons are at the unloading

Defin

gon, and then copy the TNT Model from thepoint for defining the release. Name

to the north. The deliveries take place once a week, invoare always during the day and never at night. The wagons are 10.6 m in length, 2.6 min diameter with a volume of 54 m3, are raised 0.5 m above the ground, and aredelivered with a fill-level of 80%. The propane is unsphere: under saturation conditions at atmospheric temperature (taken as 10o

There are many hazardous events that could be modelled for the tank wagons,includinrupture of a wagon under normal operatingwagon, and a fireball produced by catastrophic ruimpingement. All events are assumed to occur whi

point 100 m south of the propane sphere.

ing the Rupture of the Wagon

First, create a folder and name it

nditions, a leak from the liquid side of a

Tank Wa

Rupture folder, which you will use as the startingthe Model Wagon Rupture.

Open the input dialog and set the data as follows:


Material Inventory 43.2 m3

Elevation 1.8 mLocation

North co-ordinate 435581 m

Defin

pture Model and name the copy Wagon Liquid Leak, and then open the input

ing the Leak from the Liquid Side of a Wagon

Copy the Ru

dialog and set the data as follows:


Scenario Type LeakScenario

Hole Diameter 1 inch

Vessel Tank Head 1.95 m

Location Elevation 0.5 m

Indoor/Outdoor Direction Down – Impinging on the Ground

35




For a release from the body of a vessel rather than from attached pipework, you shset the Scenario Type to Leak. This will give a larger discharge rate since there are nofrictional losses during the flow to the leak-location. For the leak scenario, you specifythe lea

ould

k-size in the Scenario tab section.

Defin

llows you to model immediate-ignition effects from fireballs and

select the option to insert a Fireball Model. Name theModel Wagon Fireball, then open the input dialog and set the data as follows:

The leak is assumed to be at the bottom of the tank, which is the most conservativeassumption for the tank head and the duration.

ing the Fireball Failure under Flame Impingement

The program apoolfires on their own, separated from any modelling of dispersion and delayed-ignition effects, and you do this by using the Fireball Model or Poolfire Model ratherthan the Source Models.

Select the Tank Wagon folder, then


Material PROPANE

East Location 197327 m

North Location 435581 m

Material

Burst Pressure 8.57 barg

Released Mass 22.2e3 kgFireball Shape

Mass Vapour Fraction 0.25

Radiation vs Distance Selected

Maximum Distance 500 m

Angle from Wind 0 degrees

Height above Origin 0 m

Radiation Ellipse Selected

Radiation Data

Incident Radiation 4 kW/m2

The Burst Pressure is 60% greater than the normal operating pressure and is used in

n and emissive power, or entering your own values. For this

The dialog also contains a Contour Data tab section ows you to define a planeand up adiation lev ich you want

Running the Calculations and the Results

Run the calculations for the and th e graphs for the 1.5/F.

2 compared with 440 m. This shows the effect of thehigher vesse Model t ameimpingement, whereas the l con a rupture under normal operatingconditions which then has a probability of ig immediately and giving fireballeffects.

calculating the surface emissive power of the fireball.

The Fireball Shape tab section gives you the choice between using a correlation toobtain the radius, duratioModel, you are using the correlation.

that allto three r els for wh contour results.

Viewing

Tank Wagon folder en view thWeather, and then examine the Bleve or fireball results

The Fireball Model gives slightly larger effect distances than the Rupture Model, with adistance of about 460 m to 4 kW/m

l pressure used in the Fireball

Rupture Modo model failure under fl

siderseniting

36




Savin

ethe

ption from the File menu, the Save As r input data. If you selectl be

What Next?

g the Study Folder with the Results

You have now completed the tutorial, and you should save the Study Folder in orderto save the changes you have made.

By default, the program will only save the input data, which means that the next timyou open the Study Folder, you will have to rerun the calculations in order to view

full results. However, if you select the Save As… odialog will contain an option to Save results as well as you

this option, the program will save the full set of consequence results and you wilable to view the results immediately the next time you open the Study Folder –although you should be aware that the file may be large, e.g. 25 MB or more.

This tutorial has not covered every feature of the program, but you should now haveenough of an understanding of the approach and methods used in the program to beable to explore the remaining features yourself, with .

If you need further detai ct of the program, or if you need guidance onhow to model a particular situation for your facility, you should contact productsupport using the details duct Support menu.

the assistance of the online Help

ls on any aspe

given under Pro in the Help

211576535 PHAST Tutorial Manual

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Transcript of 211576535 PHAST Tutorial Manual