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Reference Manual

Aspen Flare System Analyzer

Version: V8.0December 2012

Copyright (c) 1981-2012 by Aspen Technology, Inc. All rights reserved.Aspen Flare System Analyzer, Aspen Flarenet, Aspen Plus, Aspen HYSYS, Aspen Plus Dynamics, andthe aspen leaf logo are trademarks or registered trademarks of Aspen Technology, Inc., Burlington,MA. All other brand and product names are trademarks or registered trademarks of their respectivecompanies.

This document is intended as a guide to using AspenTech's software. This documentation containsAspenTech proprietary and confidential information and may not be disclosed, used, or copied withoutthe prior consent of AspenTech or as set forth in the applicable license agreement. Users are solelyresponsible for the proper use of the software and the application of the results obtained.

Although AspenTech has tested the software and reviewed the documentation, the sole warranty forthe software may be found in the applicable license agreement between AspenTech and the user.ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITHRESPECT TO THIS DOCUMENTATION, ITS QUALITY, PERFORMANCE, MERCHANTABILITY, OR FITNESSFOR A PARTICULAR PURPOSE.

Aspen Technology, Inc.200 Wheeler RoadBurlington, MA 01803-5501USAPhone: (781) 221-6400Toll free: (888) 996-7001Website http://www.aspentech.com

Contents i

Contents1 Introduction.........................................................................................................1

About this document.........................................................................................1Audience.........................................................................................................1Related Documentation.....................................................................................1Technical Support ............................................................................................1

2 Components .........................................................................................................3

Overview.........................................................................................................3Selecting Components ......................................................................................4

Component Types ..................................................................................4Component List......................................................................................4Matching the Name String .......................................................................5Removing Selected Components ..............................................................5

Adding/Editing Components...............................................................................6Adding Hypothetical Component/Edit Component .......................................6Identification Tab ...................................................................................6Critical Tab............................................................................................7Other Tab..............................................................................................9Editing Database Components .................................................................9Estimating Unknown Properties.............................................................. 10

Organizing the Component List ........................................................................ 10Changing the Components .................................................................... 11Combining Components ........................................................................ 11

Binary Interaction Parameters ......................................................................... 11

3 Scenarios ...........................................................................................................15

Overview....................................................................................................... 15Scenario Manager .......................................................................................... 16Adding/Editing Scenarios................................................................................. 17

General Tab......................................................................................... 18Constraints Tab.................................................................................... 18Sources Tab ........................................................................................ 20Estimates Tab...................................................................................... 21

Scenario Tools ............................................................................................... 23Adding Single Source Scenarios ............................................................. 23

4 Pipe Network......................................................................................................25

Overview....................................................................................................... 25Pipe Manager................................................................................................. 25Ignoring/Restoring Pipes ................................................................................. 26

Connections Tab .................................................................................. 27Dimensions Tab ................................................................................... 29

ii Contents

Fittings Tab ......................................................................................... 30Heat Transfer Tab ................................................................................ 32Methods Tab........................................................................................ 33Summary Tab ...................................................................................... 37Multiple Editing .................................................................................... 38Pipe Class Editor .................................................................................. 39

5 Nodes.................................................................................................................41

Overview....................................................................................................... 41Node Manager ............................................................................................... 41Ignoring/Restoring Nodes................................................................................ 42Connection Nodes .......................................................................................... 43

Connector ........................................................................................... 43Flow Bleed........................................................................................... 47Horizontal Separator............................................................................. 50Orifice Plate......................................................................................... 56Tee .................................................................................................... 60Vertical Separator ................................................................................ 65

Boundary Nodes............................................................................................. 70Control Valve....................................................................................... 71Relief Valve ......................................................................................... 79Source Tools........................................................................................ 92Flare Tip ............................................................................................. 93

6 Calculations........................................................................................................98

Starting the Calculations ................................................................................. 98Efficient Modeling Techniques .......................................................................... 99

Data Entry........................................................................................... 99Calculation Speed............................................................................... 100Sizing Calculations ............................................................................. 101

7 Databases ........................................................................................................105

Overview..................................................................................................... 105Database Features ....................................................................................... 106

Grid Controls ..................................................................................... 106Maneuvering Through the Table ........................................................... 107Printing............................................................................................. 107Adding/Deleting Data.......................................................................... 107

Setting The Password ................................................................................... 108Pipe Schedule Database Editor....................................................................... 108Fittings Database Editor ................................................................................ 109Component Database Editor .......................................................................... 110

Importing Component Data ................................................................. 111

8 Automation ......................................................................................................113

Overview..................................................................................................... 113Objects ....................................................................................................... 113

Object Hierarchy ................................................................................ 114The Aspen Flare System Analyzer Type Library ...................................... 115Object Browser .................................................................................. 115Automation Syntax............................................................................. 118

Contents iii

Examples: Accessing Aspen Flare System Analyzer Object Properties ....... 121Aspen Flare System Analyzer Object Reference................................................ 124

Application ........................................................................................ 125Bleed................................................................................................ 126Bleeds .............................................................................................. 126Component........................................................................................ 127Components ...................................................................................... 128Connector ......................................................................................... 128Connectors........................................................................................ 129ControlValve...................................................................................... 130ControlValves .................................................................................... 131HorizontalSeparator............................................................................ 131HorizontalSeparators .......................................................................... 132Nodes ............................................................................................... 132OrificePlate........................................................................................ 133OrificePlates ...................................................................................... 133Pipe.................................................................................................. 134Pipes ................................................................................................ 136ReliefValve ........................................................................................ 137ReliefValves....................................................................................... 139Scenario ........................................................................................... 139Scenarios .......................................................................................... 140Solver............................................................................................... 140Tee .................................................................................................. 141Tees ................................................................................................. 142Tip ................................................................................................... 143Tips.................................................................................................. 144VerticalSeparator ............................................................................... 144VerticalSeparators.............................................................................. 145

Example Automation In Visual Basic ............................................................ 145Updating Automation Files From Previous Versions ........................................... 152

9 Theoretical Basis ..............................................................................................154

Pressure Drop.............................................................................................. 154Pipe Pressure Drop Method.................................................................. 154Fittings Pressure Change Methods ........................................................ 161

Vapor-Liquid Equilibrium ............................................................................... 170Compressible Gas............................................................................... 170Vapor Pressure .................................................................................. 170Soave Redlich Kwong.......................................................................... 171Peng Robinson ................................................................................... 172

Physical Properties ....................................................................................... 173Vapor Density .................................................................................... 173Liquid Density.................................................................................... 173Vapor Viscosity .................................................................................. 173Liquid Viscosity .................................................................................. 174Liquid Phase Mixing Rules for Viscosity.................................................. 175Thermal Conductivity.......................................................................... 176Enthalpy ........................................................................................... 177

Noise .......................................................................................................... 179

iv Contents

A File Format.......................................................................................................183

Import/Export Details ................................................................................... 183Process Descriptions........................................................................... 183Definition File Formats ........................................................................ 186Recognized Objects and Items ............................................................. 191

Report File Formats ...................................................................................... 209

B References .......................................................................................................215

C Glossary of Terms ............................................................................................217

Adiabatic Flow ............................................................................................. 217Choked Flow................................................................................................ 217Critical Pressure ........................................................................................... 217Critical Temperature ..................................................................................... 217Dongle........................................................................................................ 217Equivalent Length ........................................................................................ 217Isothermal Flow ........................................................................................... 218MABP.......................................................................................................... 218Mach Number .............................................................................................. 218Node .......................................................................................................... 218Reduced Pressure......................................................................................... 218Reduced Temperature................................................................................... 218Scenario ..................................................................................................... 218Schedule..................................................................................................... 219Security Device............................................................................................ 219Source ........................................................................................................ 219Static Pressure............................................................................................. 219Tailpipe....................................................................................................... 219Total Pressure.............................................................................................. 219Velocity Pressure.......................................................................................... 219

Index ..................................................................................................................220

1 Introduction 1

1 Introduction

This section provides information on the following topics: About this Document Audience Related Documentation Technical Support

About this documentThe guide provides a detailed description of all the features and functionalitywithin Aspen Flare System Analyzer (previously called Aspen FLARENET).

AudienceThis guide is intended for process and process systems engineers.

Related DocumentationTitle Content

Aspen Flare System AnalyzerGetting Started Guide

Tutorials covering the basic use of AspenFlare System Analyzer

Technical SupportAspenTech customers with a valid license and software maintenanceagreement can register to access the online AspenTech Support Center at:

http://support.aspentech.com

This Web support site allows you to: Access current product documentation Search for tech tips, solutions and frequently asked questions (FAQs) Search for and download application examples

2 1 Introduction

Search for and download service packs and product updates Submit and track technical issues Send suggestions Report product defects Review lists of known deficiencies and defects

Registered users can also subscribe to our Technical Support e-Bulletins.These e-Bulletins are used to alert users to important technical supportinformation such as:

Technical advisories Product updates and releases

Customer support is also available by phone, fax, and email. The most up-to-date contact information is available at the AspenTech Support Center athttp://support.aspentech.com.

2 Components 3

2 Components

This section provides information on the following topics: Overview Selecting Components Adding/Editing Components Organizing the Component List Binary Interaction Parameters

OverviewData for all components that will be used in the simulation must be selectedbefore the sources are defined. These components may be taken from thestandard component library, or you may define your own components, knownas hypothetical components.

You may select components from Component Manager, which can beaccessed by clicking Components in the Build group on the Home tab of theRibbon.

The Component Manager window will be displayed:

4 2 Components

Fig 2.1

This view displays all of the Available Components and SelectedComponents, and provides various tools which you can use to add and editdatabase and hypothetical components.

Selecting Components

Component TypesYou may filter the list of available components to include only those belongingto a specific family. All and None turn all of the filters on and off,respectively, Invert toggles the status of each check box individually. As anexample, if only Hydrocarbons (HC) and Misc were selected, and you clickedInvert, then these two check boxes would be cleared, while the remainingcheck boxes would be selected.

Component ListComponents can be chosen from the Available Components list, and addedto the Selected Components list, using one of the following methods:1 Arrow Keys Use the arrow keys to move the highlight up or down one

component.2 PageUp/PageDown - Press these keyboard keys to advance an entire

page forward or backward.

2 Components 5

3 Home/End - Press Home to move to the start of the list and End tomove to the end of the list.

4 Scroll Bar - Use the scroll bar to move up and down through the list.

Note: You can select multiple components by using the SHIFT or CTRL keys asyou select components.5 Enter the component name from keyboard - When you type a letter

or number, you will move to the next component in the list which startswith that character. If you repeatedly enter the same character, you willcycle through all of the components which start with that character.

To add a component, you must first highlight it (by moving through the listuntil that component is highlighted) and click to select, then transfer it bydouble-clicking it or clicking Add.

Matching the Name StringThe interpretation of your input is limited to the Component Types whichare checked.

Another way to add components is through the Selection Filter feature. TheSelection Filter box accepts keyboard input, and is used to locate thecomponent(s) in the current list that best matches your input.

You may use wildcard characters as follows:? - Represents a single character.* - Represents a group of characters of undefined length.Any filter string has an implied * character at the end.

Some examples are shown here:

Filter Result

methan methanol, methane, etc.*anol methanol, ethanol, propanol, etc.?-propanol 1-propanol, 2-propanol*ane methane, ethane, propane, i-butane, etc.

As you are typing into the Selection Filter box, the component list isupdated, matching what you have presently typed. You may not have to enterthe complete name or formula before it appears in the component list.

Removing Selected ComponentsYou can remove any component from the Selected Components list:1 Highlight the component(s) you want to delete.2 Click Remove.

You can select multiple components using Shift-click and Ctrl-click to removethem all. Once the components are removed from the list, any sourcecompositions that used this component will be normalized.

6 2 Components

Adding/Editing ComponentsTo create a new component (hypothetical), click Hypothetical. Hypotheticalcomponents are set up in the same manner as database components.Previously defined hypothetical components can be changed by selectingthem in the Selected Components list and clicking Edit.

Adding Hypothetical Component/EditComponentUpon clicking either Hypothetical or Edit, the Component Editor opens up.

Identification TabThe minimum data requirements for creating a component are specified here:

Fig 2.2

Component Types: Hydrocarbon (HC) Miscellaneous (Misc) Amine

2 Components 7

Alcohol Ketone Aldehyde Ester Carboxylic Acid (Carbacid) Halogen Nitrile Phenol Ether

The following fields are available on this tab:

Input Field Description

Name An alphanumeric name for the component (e.g. - Hypo -1).Type The type of component (or family) can be selected from the list

provided. There is a wide selection of families to choose from, whichallows better estimation methods to be chosen for that component.

ID The ID number is provided automatically for new components andcannot be edited.

Mol. Wt. The molecular weight of the component.NBP The normal boiling point of the component.Std. Density The density of the component as liquid at 1 atm and 60 F.Watson K The Watson characterization factor.

Critical TabCritical properties are specified here.

8 2 Components

Fig 2.3



Critical Pres. The critical pressure of the component. If the componentrepresents more than a single real component, the pseudocritical pressure should be used.

Critical Temp. The critical temperature of the component. If the componentrepresents more than a single real component, the pseudocritical temperature should be used.

Critical Volume The critical volume of the component. If the componentrepresents more than a single real component, the pseudocritical volume should be used.

Char. Volume The characteristic volume of the component. If the componentrepresents more than a single real component, the pseudocharacteristic volume should be used.

Acentric Factor The acentric factor of the component.Acent. Fact. (SRK) The Soave-Redlich-Kwong acentric factor of the component

(also called the COSTALD Acentricity).

2 Components 9

Other TabCoefficients for the polynomial equations for the prediction of Ideal Gasthermodynamic properties and parameters for the viscosity calculations arespecified here:

Fig 2.4



Hi A, Hi B, Hi C, Hi D, Hi E, andHi F

The coefficients for the ideal gas specific enthalpyequation:

Entropy Coef. The coefficient for the entropy equation.Viscosity A and Viscosity B Viscosity coefficients used in the NBS Method (Ely

and Hanley, 1983).

Editing Database ComponentsIf you want to change the data for one of the database components, e.g.Methane, you will find that opening the Component Editor for thiscomponent will display read-only values that cannot be changed.

Hi

A BT CT2 DT3 ET4 FT5+ + + + +=

10 2 Components

Fig 2.5

In order to update the data for a database component it must first bechanged to a hypothetical component.

At the very minimum, you need to specify the Molecular Weight. However, itis a good practice to specify at least two of the following properties:

Molecular Weight (Mol. Wt.)

Normal Boiling Point (NBP)

Standard Density (Std. Density)

This is done by clicking Hypothetical in the Component Editor.

Estimating Unknown PropertiesIf any of the above data is unknown, click Estimate to fill-in the unknownproperties. Supply as many properties as are known, so that the estimationcan be as accurate as possible.

Organizing the Component ListThe Selected Components list can be organized in the following differentways.

2 Components 11

Changing the ComponentsYou can switch the components in the Selected Components list with theones in the Available Components list while maintaining the source molefractions.

In Component Manager, select the components in both the SelectedComponents and the Available Components lists. Click Switch to switchthe two components.

Combining ComponentsMultiple components can be combined and represented by a single componentto reduce the number of components in the model.

To combine multiple components:1 Select the components you want to combine by Ctrl-clicking them in the

Selected Components list.2 Click Combine.

The Component Combination window will be displayed, and ask you toselect which basis should be used. The highlighted component in the boxat the upper part of the window is the target component to combine yourselected components into. Once the basis has been selected the combinedcomponents will update each source in the model by summing thecomposition of all of the combined components and assigning it to thetarget component.

Reducing the number of components in this way is useful since it can greatlyspeed the calculations. This is especially true where a model contains sourcesdefined with a long list of hypothetical components.

For example, consider a model containing the hypothetical componentsBP200, BP225, BP250, BP275, BP300 boiling at 200C, 225C, 250C, 275Cand 300C respectively. Since these components are likely to stay in theliquid phase throughout the flare system, they may be combined into a singlecomponent, BP250 without significant loss of accuracy. As another example,in a purely gas phase flare system it is possible to combine isomers such as i-Butane and n-Butane into a single component n-Butane withoutcompromising results.

Binary Interaction ParametersBinary Interaction Coefficients, often known as KIJs, are factors that are usedin equations of state to better fit the interaction between pairs of componentsand hence improve the accuracy of VLE calculations. You are allowed tospecify binary interaction parameters for the Peng Robinson and SoaveRedlich Kwong VLE methods or to estimate them through the Binary Coeffstab of the Component Manager as shown here.

12 2 Components

Fig 2.6

To define binary interaction coefficients, first select either the PengRobinson or Soave Redlich Kwong VLE method from the VLE Method listat the top of the window.

Note: Binary interaction coefficients are not used by either theCompressible Gas or Vapor Pressure VLE methods at present.

Individual binary interaction parameters are set by selecting the requiredentry in the matrix and typing in the new value.

Note: The matrix is symmetrical i.e. KJI is the same value as KJI, and updatingan entry will also update the corresponding entry in the table. E.g. updatingthe entry in the Methane column, Propane row will also update the entry inthe Propane column, Methane row.

Individual binary interaction parameters may be estimated by selecting therequired entry in the matrix and clicking Estimate HC. The estimationmethod is based on the components' boiling point, standard liquid density andcritical volume.

It is possible to set several binary interaction parameters at the same timeeither by Ctrl-clicking the two corners of a rectangular area in the matrix. Theselected entries can then be estimated by clicking Estimate HC or set to 0.0by clicking Zero HC-HC.

Clicking Reset All causes all interaction parameters to be set to their defaultvalues. Generally this is 0.0 for hydrocarbon components with non zerovalues being supplied only for common polar components.

2 Components 13

If the Auto Estimate check box is selected, then the interaction parametersfor new components are automatically estimated as they are added to themodel.

14 2 Components

3 Scenarios 15

3 Scenarios

This section provides information on the following topics: Overview Scenario Manager Adding/Editing Scenarios Scenario Tools

OverviewA scenario defines a set of source conditions (flows, compositions, pressuresand temperatures) for the entire network. The design of a typical flare headersystem will be comprised of many scenarios for each of which the headersystem must have adequate hydraulic capacity. Typical scenarios mightcorrespond to:

Plant wide power failure Plant wide cooling medium or instrument air failure Localized control valve failure Localized fire or Depressurization

The scenario management allows you to simultaneously design and rate theheader system for all of the possible relief scenarios.

Note: Although the major relief scenarios will normally constrain the size ofthe main headers, care should be taken in the evaluation of velocities in theindividual relief valve tailpipes and sub headers. When looking at relief valveswhich might operate alone, lower back pressures in the main headers maylead to localized high velocities and consequently choked flow in the tail pipes.

As well as having different source conditions, each scenario can have uniquedesign limitations that will be used either to size the pipes or to highlightproblems when an existing flare system is being rated. For example, a Machnumber limit of 0.30 might be applied for normal flaring compared to a Machnumber limit of 0.50 or greater at the peak flows encountered during plantblowdown.

16 3 Scenarios

Scenario ManagerScenarios can also be selected by selecting the scenario from the list in Rungroup on the Home tab of the Ribbon.

Fig 3.1

Scenarios are managed via the Scenario Manager. This window allows youto add, edit or delete scenarios as well as to select the current scenario forwhich scenario specific data is displayed. All cases have at least one scenario.

To access the Scenario ManagerOn the Home tab, in Build, click Scenarios.

Scenario Manager will be displayed:

3 Scenarios 17

Fig 3.2

The Scenario Manager displays all scenarios in the case, and indicates thecurrent scenario. Several buttons are available:

Button Description

Clone Clones the highlighted scenario and adds a new scenario tothe Scenarios list.

Edit Edits the highlighted scenario.Delete Removes the currently highlighted scenario. There must

always be at least one scenario in the case.Current To make a scenario the current one, highlight the appropriate

scenario, and then click Current.Close Closes the Scenario Manager.

Adding/Editing ScenariosAspen Flare System Analyzer has no pre-programmed limits on the number ofscenarios which can be defined within a single case.

To add a scenario, highlight a existing scenario in the Scenarios list, andthen click Clone in the Scenario Manager.

To edit a scenario, highlight it, and then click Edit.

The Scenario Editor will be displayed.

18 3 Scenarios

General TabYou may provide the following information on the General tab:

Fig 3.3

Data Description

Name An alphanumeric description of the scenario (e.g. PowerFailure).

System Back Pres. The system back pressure at the Flare Tip exit. This willnormally be atmospheric pressure, but can be set to representsystem design conditions at the exit point. If left empty, thevalue on the Calculation Options Editor will be used. Theminimum value is 0.01 bar (absolute pressure).

Constraints TabThis tab requires the following information for both headers and tailpipes.

3 Scenarios 19

Fig 3.4

Tailpipes are indicated by the Tailpipe field on the Connections box of thePipe Editor. You may provide different design information (Mach Number,Noise at 1 m, Vapor Velocity, Liquid Velocity) for the Headers andTailpipes. Any boxes may be left empty, in which case they will be ignored.

Data Description

Mach Number The maximum allowable Mach number for all pipe segments.Calculated values that exceed this number will be highlighted in theresults.

Vapor Velocity The maximum allowable vapor velocity. Calculated velocities thatexceed this value will be indicated in the results.

Liquid Velocity The maximum allowable liquid velocity. Calculated velocities thatexceed this value will be indicated in the results.

Rho V2 The density times the velocity square. This value is normally usedas a limiting factor to prevent erosion.

Noise The maximum allowable sound pressure level at a distance of 1meter for all pipe segments. This is an average value over thelength of the pipe. Calculated values that exceed this specificationwill be highlighted in the results.

20 3 Scenarios

Data Description

Check Vel.Constraint

Specify either Mixture Velocity or Phase Superficial Velocity isused while checking the velocity constraints for design in ascenario.

Note: Whilst rating the network you may define a Mach number constraint of1.00, in order to highlight only choked flow conditions. This is notrecommended for design calculations where a more reasonable value such as0.5 or 0.7 will lead to a more rapid solution towards the maximum allowableback pressure constraints.

Sources TabIf a source is ignored, the MABP constraint is ignored by sizing calculations.

When you select the Sources tab, you will see that all sources are displayedon this tab.

Note: If you are setting up a new case, the Sources tab will not show anysources.

3 Scenarios 21

Fig 3.5

This tab is useful in that you can easily toggle whether or not individualsources are to be included in the current scenario, without having to eitherunnecessarily delete sources or set the flow of a source to zero.

Estimates TabThe Estimates tab allows some control over the selection and initialization offlowrates for pipes which are to be used as tears in the solution of loopedsystems. The use to which each field is put is dependent upon the StructureAnalyzer setting on the Solver tab of Calculation Options Editor.

The check boxes in the No Tear column of the table allow you to preventpipes from being used as tears - select the check box to prevent a pipe frombeing used as a tear or clear it to allow it. This setting has no effect if theSimultaneous structural analyzer is used.

When the Convergent structural analyzer is used, the Molar Flow columnrecommends a tear location and initial value for the flow at the tear location.If the structural analyzer does find that the pipe may be a valid tear location,then this value is ignored.

When the Simultaneous structural analyzer is used, the Molar Flow columnis used to seed the analyzer. This value will always impact the initialization aslong as the structural analysis succeeds but the pipe will not necessarily beselected as a tear pipe. In the event that the structural analysis fails with anyMolar Flow estimates, the model will be initialized by the default values.

22 3 Scenarios

Fig 3.6

Since the Simultaneous structural analyzer generally offers betterperformance than the Convergent analyzer it will rarely be necessary tospecify information on the Estimates tab other than for the purpose ofimproving the speed of convergence of the model. In the event that a modelproves problematic to converge, a number of additional columns are availableto tune the convergence algorithms. These may be exposed by stretching theview horizontally.

The Max. Step column defines the maximum change to the flow in a tearpipe over a single iteration whilst the Max. Flow and Min. Flow columnsconstrain the flow in a tear pipe. Not all these values are used by all the LoopSolver algorithms.

Max. Step Max. Flow Min. Flow

Newton-Raphson 3 3 3Broyden 3 3 3Force ConvergentConjugate Gradient MinimisationQuasi-Newton Minimization

3 Scenarios 23

Scenario ToolsThe complete analysis of a flare system should ideally include analysis of thesystem for the scenarios in which each source relieves on its own. For a largenetwork with many sources, it can become tedious to define each of thesescenarios. These can automatically be added to your model as follows.

Adding Single Source ScenariosClick Source Tools from the Tools group on the Home tab of the Ribbon,then select Add Single Source Scenarios or use the hot key combinationAlt, H, U, A. Click OK for the message that pops up.

This will analyze your model and add a scenario for each source that has anon-zero flow rate defined in at least one scenario. Source data will be copiedfrom the scenario in which it has the highest flow rate.

24 3 Scenarios

4 Pipe Network 25

4 Pipe Network

This section provides information on the following topics: Overview Pipe Manager Ignoring/Restoring Pipes Multiple Editing

OverviewThe pipe network comprises a series of interconnected pipes. These pipes canbe added, edited and deleted from the Pipe Manager.

Pipe ManagerTo access the Pipe Manager, click Pipes in the Build group on the Hometab of the Ribbon.

26 4 Pipe Network

Fig 4.1

The following buttons are available:

Button Description

Add Adds a new pipe segment. This new pipe will be named with a numberdepending upon the number of pipes already added.

Edit Edits the currently highlighted pipe segment.Delete Removes the currently highlighted pipe segment.Close Closes the Pipe Manager.

Ignoring/Restoring PipesWhen you ignore a single pipe, all upstream pipes are automatically ignored.

You can ignore single or multiple pipes within the model. When you ignore asingle pipe, all upstream nodes are automatically ignored. This enables you todo what if type calculations, where part of the network can be excluded fromthe calculation without the need for deletion and reinstallation of theappropriate nodes.

To ignore a pipe:1 Open the Pipe Editor window of the pipe that you want to ignore.2 On the Connections tab, select the Ignore check box.

4 Pipe Network 27

Fig 4.2

To restore a pipe that has previously been ignored:1 Open the Pipe Editor window of the pipe that you want to restore.2 On the Connections tab, clear the Ignore check box.

Connections TabThe name of the pipe segment and connectivity information is specified here.

28 4 Pipe Network

Fig 4.3


Input Data Description

Name An alphanumeric description of the pipe segment.Location An alphanumeric description of the location within the plant for the

segment.UpstreamNode

This is the name of the node upstream of the pipe. The list allowsyou to select from a list of existing unconnected nodes in the model.

DownstreamNode

This is the name of the node upstream of the pipe. The list allowsyou to select from a list of existing unconnected nodes in the model.

Tailpipe This list allows you to select whether the pipe should be treated as atailpipe. If set to Yes and the Rated Flow for Tailpipes calculationoption is selected in the Calculation Options dialog box, thepressure drop for this pipe will be calculated using the rated flow inplace of the relieving flow rate.

Ignore This check box may be selected to remove the pipe fromcalculations temporarily. When selected the pipe and all upstreamnodes and pipes will be ignored during calculations.

Fitting Loss The fitting loss for the pipe segment. You cannot change the valueshown in this box. Instead, calculated value on the Fittings tab canbe updated by clicking Link or Paste.

4 Pipe Network 29

You have the option of modeling a pipe segment as a main header or atailpipe. The ability to classify a pipe as either a tailpipe or a header allowsyou to perform calculations in which the pressure drop for tailpipes isdetermined by the rated flow and that for headers is determined by thenominal flow. This is in accordance with API-RP-521.

In the Scenario Editor, you can set design limits for the Mach Number,Vapor and Liquid Velocities, Rho V2 and Noise separately for the mainheaders and the tailpipes.

Dimensions TabThe physical dimensions and characteristics of the pipe segment are specifiedhere.

Fig 4.4



Length The physical length of the pipe segment. This length is used inassociation with the fittings loss coefficients to calculate theequivalent length of the pipe. If you have equivalent length datafor your network, enter this data here as the sum of the actuallength plus the equivalent length of the fittings and enter zero forthe fittings loss coefficients.

30 4 Pipe Network


Elevation Change A positive elevation indicates that the outlet is higher than theinlet.

Material The pipe material, either Carbon Steel or Stainless Steel.Roughness The surface roughness of the pipe segment. Whenever a material

is selected, the absolute roughness is initialized to the defaultvalue for the material as defined on the Preferences view.

ThermalConductivity

The thermal conductivity of the pipe wall. This is used by theheat transfer calculations when these are enabled.

NominalDiameter

The nominal pipe diameter used to describe the pipe size. Forpipes with a nominal diameter of 14 inches or more, this will bethe same as the outside diameter of the pipe. If you select "-",you can specify your own data for the Internal Diameter andWall Thickness; otherwise, it is not necessary to specify thesevalues for the pipe.

Schedule Select a schedule number from the list, you will be able to selecta nominal pipe diameter from the pipe databases. It will not benecessary to specify the Internal Diameter or the WallThickness for the pipe if you have not specified "-" as theNominal Diameter.

InternalDiameter

The pipe diameter used for the pressure drop calculations.

Wall Thickness The thickness of the pipe wall. Valid values are any positivenumber or zero.

Use Class Select Yes to restrict the pipe sizes to those defined by the PipeClass.

Sizeable If you wish the pipe segment to be resized by sizing calculations,Yes should be selected. For example, a model of a networkcontaining a representation of the knockout drum, as a pipesegment would normally leave this unchecked such that sizingcalculations for the pipes would not change the knockout drumsize.

Schedule Numbers: Carbon Steel: 10, 20, 30, 40, 60, 80, 100, 120, 140, 160, STD, XS,

XXS, User Stainless Steel: 5S, 10S, 40S, 80S

Fittings TabA list of pipe fittings may be added to the pipe segment. These fittings will bemodeled as an additional equivalent length applied linearly over the physicallength of the pipe segment.

4 Pipe Network 31

Fig 4.5



LengthMultiplier

The length of the pipe is multiplied by this value to determine theequivalent length used for the pressure drop calculation. If leftblank then the value on the Calculation Options Editor is used.This option is useful for making an allowance for bends and otherfittings if these are not known.

Fittings Loss The fittings "K" factor is calculated from the following equation inwhich Ft is the friction factor for fully developed turbulent flow:K = A + BFt

From the Database Fittings list, select the appropriate type of fitting, andthen click Add to move the selection to the Selected Fittings list. You canselect as many fittings as required. The final fitting loss equation, which willbe a sum of all the selected fittings, will appear in a display field underneaththe Selected Fittings list.

Click Link to transfer the coefficients for this equation into theFittings Loss field on the Connections tab, while maintaining the listof fittings.

Click Paste to transfer the coefficients for the fitting equation into theFittings Loss field. The selected list of fittings will not be retained.

32 4 Pipe Network

To remove the selected fitting individually, select the fitting and clickDelete.

Note: The network cannot be sized correctly if you specify equivalent lengthdata to model fittings losses, since the equivalent length of any pipe fitting isa function of the pipe diameter and will therefore be incorrect when thediameters change.

Heat Transfer TabThe pipe segment may perform calculations taking into account heat transferwith the external air.

Fig 4.6



External Conditions GroupExternal Medium Select the external medium. Two options are

currently available: Air or Sea Water.Temperature Enter the temperature of the external air. If this field

is left blank, the global value set via the CalculationOptions Editor is used.

4 Pipe Network 33


External Medium Velocity Enter the velocity of the external medium. If this fieldis left blank, the global value set via the CalculationOptions Editor is used.

Heat Transfer Enabled This list selects whether heat transfer calculations areto be performed for the pipe. Furthermore, settingonly enables heat transfer calculations if the EnableHeat Transfer option is also selected in theCalculation Options Editor.

External Radiative HTC This list selects whether or not the external radiativeheat transfer coefficient is included within the heattransfer calculations.

Emissivity Enter the fractional Emissivity to be used forradiative heat transfer calculations.

Multiple Element Calculation This list selects whether the heat transfer calculationis done using a single element or the same number ofelements as the pressure drop calculation. If Yes isselected, the heat transfer calculation sues the samenumber of elements as the pressure drop calculation

Insulation GroupDescription A brief description to identify the type of pipe

insulation.Thickness Supply the insulation thickness.Thermal Conductivity Enter the insulation thermal conductivity.Heating GroupOutlet Temp You can explicitly set an outlet temperature for this

segment, or leave it blank. A heater in a flareknockout drum is an example of process equipmentthat may require a fixed outlet temperature.

Duty Enter the heating duty and the outlet temperaturewill be calculated based on the inlet temperature andthe defined duty.

Methods TabCalculation methods are specified here.

34 4 Pipe Network

Fig 4.7



VLE Method GroupVLE Method The options for the Vapor-Liquid Equilibrium calculations are as

follows (see Chapter 9 Theoretical Basis for more details): Compressible Gas - Real Gas relationship. This is only

available when the Enthalpy Method on the CalculationOptions Editor is Ideal Gas.

Peng Robinson - Peng Robinson Equation of State. This isavailable when the Enthalpy Method on the CalculationOptions Editor is NOT Ideal Gas.

Soave Redlich Kwong - Soave Redlich Kwong Equation ofState. This is available when the Enthalpy Method on theCalculation Options Editor is NOT Ideal Gas.

Vapor Pressure - Vapor Pressure method as described in APITechnical Data Book Volume 113. This is available when theEnthalpy Method on the Calculation Options Editor isNOT Ideal Gas.

Model Default - If this is selected, the Default method for theVLE method (as defined on the Calculation Options Editor)will be used.

Pressure Drop Group

4 Pipe Network 35


Horizontaland InclinedPipes

The Horizontal/Inclined methods apply only when you haveselected Two-Phase pressure drop. The options are:

Isothermal Gas - This is a compressible gas method thatassumes isothermal expansion of the gas as it passes alongthe pipe. Aspen Flare System Analyzer uses averagedproperties of the fluid over the length of the pipe. The outlettemperature from the pipe is calculated by adiabatic heatbalance either with or without heat transfer. Pressure lossesdue to change in elevation are ignored.

Adiabatic Gas - This is a compressible gas method thatassumes adiabatic expansion of the gas as it passes along thepipe. As with the Isothermal Gas method, pressure losses dueto changes in elevation are ignored.

Beggs & Brill - The Beggs and Brill method is based on workdone with an air-water mixture at many different conditions,and is applicable for inclined flow.

Dukler - Dukler breaks the pressure drop in two-phasesystems into three components - friction, elevation andacceleration. Each component is evaluated independently andadded algebraically to determine the overall pressure drop.

Lockhart Martinelli Lockhart Martinelli correlations modelsthe two phase pressure drop in terms of a single phasepressure drop multiplied by a correction factor. Accelerationchanges are not included.

Beggs and Brill (No Acc.) The Beggs and Brill methodswithout the acceleration term.

Beggs and Brill (Homog.) The Beggs and Brill methods witha homogeneous acceleration term.

Dukler (AGA Head) - Uses the AGA equation for thecalculation of the static head term rather than the Eatonequation which can be poor when you have small quantities ofliquid in the system.

Model Default - If this is selected, the Default method for theHorizontal/Inclined method (as defined on the CalculationOptions Editor) will be used.

36 4 Pipe Network


VerticalPipes

The Vertical method applies only when you have selected Two-Phasepressure drop. The options are:

Isothermal Gas - This is a compressible gas method thatassumes isothermal expansion of the gas as it passes alongthe pipe. Aspen Flare System Analyzer uses averagedproperties of the fluid over the length of the pipe. The outlettemperature from the pipe is calculated by adiabatic heatbalance either with or without heat transfer. Pressure lossesdue to change in elevation are ignored.

Adiabatic Gas - This is a compressible gas method thatassumes adiabatic expansion of the gas as it passes along thepipe. As with the Isothermal Gas method, pressure losses dueto changes in elevation are ignored.

Beggs & Brill - Although the Beggs and Brill method was notoriginally intended for use with vertical pipes, it isnevertheless commonly used for this purpose, and istherefore included as an option for vertical pressure dropmethods. For more details, see Chapter 9 Theoretical Basis.

Dukler - Although the Dukler method is not generallyapplicable to vertical pipes, it is included here to allowcomparison with the other methods.

Orkiszewski - This is a pressure drop correlation for vertical,two-phase flow for four different flow regimes - bubble, slug,annular-slug transition and annular mist. For more details,see Appendix A - Theoretical Basis.

Lockhart Martinelli Lockhart Martinelli correlations modelsthe two phase pressure drop in terms of a single phasepressure drop multiplied by a correction factor. Accelerationchanges are not included.

Beggs and Brill (No Acc.) The Beggs and Brill methodswithout the acceleration term.

Beggs and Brill (Homog.) The Beggs and Brill methods witha homogeneous acceleration term.

Model Default - If this is selected, the Default method for theVertical method (as defined on the Calculation OptionsEditor) will be used.

Elements For two-phase calculations, the pipe segment is divided into aspecified number of elements. On each element, energy and materialbalances are solved along with the pressure drop correlation. Insimulations involving high heat transfer rates, many increments maybe necessary, due to the non-linearity of the temperature profile.Obviously, as the number of increments increases, so does thecalculation time; therefore, you should try to select a number ofincrements that reflects the required accuracy.

4 Pipe Network 37


FrictionFactorMethod

The Friction Factor Method applies only when you have entered avalue for friction factor. The options are:

Round - This method has been maintained primarily forhistorical purposes in order for older Aspen Flare SystemAnalyzer calculations to be matched. It tends to over predictthe friction factor by up to 10% in the fully turbulent region.

Chen - It should always be the method of preference since itgives better predictions at the fully turbulent flow conditionsnormally found within flare systems.

Model Default - If this is selected, the Default method for theFriction Factor Method (as defined on the CalculationOptions Editor) will be used.

Static HeadContribution

The following options are available: Include - The static head contribution to total pressure drop in

the pipe segments is included. Ignore Downhill Recovery - The static head recovery term is

ignored for downhill sections of pipe. Ignore - The static head contribution to the pressure drop

calculation for all pipe segments is ignored.Include is applied by default.

Solver GroupDampingFactor

The damping factor used in the iterative solution procedure. If this isleft blank, the value in the Calculation Options Editor is used.

Note: When you are sizing a flare system, the initial pipe diameters mayaffect the solution when there is a liquid phase and the liquid knockout drumis modeled. You should initially size a network using vapor phase methods.

Summary TabThe results of the calculation are displayed.

38 4 Pipe Network

Fig 4.8

Multiple EditingYou can edit multiple pipe segments simultaneously by highlighting them inthe Pipe Manager with the mouse cursor while keeping the Shift keypressed. After you have finished selecting pipe segments, click Edit to openthe common Pipe Editor.

The common pipe editor view differs from that of the single pipe editor viewin the following respects:

Only fields that can be edited in multiple mode are displayed. The input fields have an additional entry, *. This entry indicates

that the value should remain at the pre edit value. In the following figure of the Dimensions tab; we enter * for the

Length and Elevation Change fields to indicate that these mustnot be changed. We specify new values for the Roughness andthe Thermal Conductivity. We select * for the Use Class andSizeable boxes to indicate that these must be changed.

4 Pipe Network 39

Fig 4.9

Pipe Class EditorThe Pipe Class Editor allows you to edit the allowable schedules for eachnominal diameter, for both Carbon Steel and Stainless Steel, during sizingcalculations. It also allows you to restrict the range of pipe sizes that may beselected during design calculations.

To access the Pipe Class Editor, click Pipe Class in Tools, on the Hometab.

40 4 Pipe Network

Fig 4.10

Note: If you have selected Use Pipe Class in the Preference Editor, theseare the schedules which will be used.

5 Nodes 41

5 Nodes

This section provides information on the following topics: Overview Node Manager Ignoring/Restoring Nodes Connection Nodes Boundary Nodes

OverviewPipes are connected via nodes, which can be added, edited and deleted fromthe Node Manager. Sources are also added through the Node Manager.

Node ManagerTo access the Node Manager, click Nodes in Build, on the Home tab.

42 5 Nodes

Fig 5.1

The following buttons are available:

Button Description

Add You will be prompted to select the type of node. This new node will benamed with a number depending upon the number of nodes of thattype already added.

Edit Allows you to edit the currently highlighted node. The form varies,depending on the type of node, as discussed below.

Delete Allows you to remove the currently highlighted node.Close Closes the Node Manager.

Ignoring/Restoring NodesWhen you ignore a single node, all upstream nodes are automatically ignored.

You can ignore single or multiple nodes within the model. When you ignore asingle node, all upstream nodes are automatically ignored. This enables youto do what if type calculations, where part of the network can be excludedfrom the calculation without the need for deletion and reinstallation of theappropriate nodes.

To ignore a node:1 Open the node editor of the node that you want to ignore.2 On the Connections tab, select the Ignore check box. The following

figure shows this for a connector node.

5 Nodes 43

Fig 5.2

To restore a node that has previously been ignored:1 Open the node editor of the node that you want to restore.2 On the Connections tab, clear the Ignore check box.

Connection NodesThe following types of connection nodes are available in Aspen Flare SystemAnalyzer. A connection node is one that links two or more pipe segments.

Connector Flow Bleed Horizontal Separator Orifice Plate Tee Vertical Separator

ConnectorThe Connector is used to model the connection of two pipes. The diametersof the pipes may be different.

Connections TabThe name of the connector and connectivity information is specified here.

44 5 Nodes

Fig 5.3

The location can have an alphanumeric name. This feature is useful for largeflowsheets, because you can provide a different location name to differentsections to make it more comprehensible.


Field Description

Name The alphanumeric description of the Connector (e.g. - HP Connect1).

Location You may want to specify the location of the node in the plant.Upstream/Downstream

Either type in the name of the pipe segment or select from the list.

At You can specify the end of the pipe segment attached to theconnector.

Ignore Select the Ignore check box to ignore this connector in thecalculations. Clear the check box to re-enable it.

Calculations TabCalculation methods are specified here.

5 Nodes 45

Fig 5.4


Field Description

Angle Specify the connector expansion angle. If not defined, it will becalculated from Length.

Length Enter the connector length. If not defined, it will be calculated fromAngle.

Fitting LossMethod

The available options are: Equal Static Pressure Pressure drop calculation is ignored

and static pressure is balanced. Calculated Pressure drop is calculated in accordance with

the Swage method.IsothermalPressure Drop

If this option is set to Yes, the inlet temperatures used for the sizechange calculations in the connector will not update during iterativecalculations for pressure loss i.e. a PT flash will be used to updatethe inlet properties. If the option is set to No, a more rigorous PHflash will be used to update the inlet properties.The connector will do one size change calculation between the inletand outlet diameters selecting expansion or contraction asappropriate.Setting this option to Yes can speed up calculations in some casesat cost of a minor loss of accuracy.

Two PhaseCorrection

If this option is set to Yes, the pressure loss coefficient in two phaseflow will be calculated using properties corrected for liquid slip. If setto No, the homogenous properties of the fluid will be used incalculating the pressure loss coefficient.

46 5 Nodes

Field Description

SwageMethod

The following options are available: Compressible - pressure losses will be calculated assuming

compressible flow through the connector at all times. Incompressible (Crane) - pressure losses will be calculated

assuming incompressible flow through the connector at alltimes. Loss coefficients are calculated using Cranecoefficients.

Transition - pressure losses will be calculated initially usingthe assumption of incompressible flow. If the pressure lossexpressed as a percentage of the inlet pressure is greaterthan the defined compressible transition value then thepressure drop will be recalculated using the compressibleflow method.

Incompressible (HTFS) - pressure losses will be calculatedassuming incompressible flow through the connector at alltimes. Loss coefficients are calculated using HTFScorrelations

The Incompressible method calculations are faster but will beless accurate at higher pressure drops. The Transition methodcan cause instabilities in some cases if the calculated pressuredrop is close to the transition value. Balance Total Pressure Frictional pressure drop is ignored

and total pressure is balanced between upstream &downstream.

CompressibleTransition

This entry defines the pressure drop as a percentage of the inletpressure at which compressible flow pressure drop calculationsshould be used. It applies only when the Transition method isselected.

Summary TabThe result of the calculations at each of the pipe connections is displayed.

5 Nodes 47

Fig 5.5

Flow BleedThe Flow Bleed is a simple calculation block that allows you to:

Specify a fixed pressure drop. Specify a constrained flow offtake where the flow offtake is calculated

from the following equation:Offtake = Multiplier x Inlet Flow + Offset

The calculated Offtake is constrained to maximum and minimum values.

Connections TabThe name of the flow bleed and connectivity information is specified here.

48 5 Nodes

Fig 5.6


Field Description

Name The alphanumeric description of the Flow Bleed (e.g. - HP ConnectXX).

Location You may want to specify the location of the node in the plant.Upstream/Downstream

Either type in the name of the pipe segment or select from the list.

At You can specify the end of the pipe segment attached to the flowbleed.

Ignore Select the Ignore check box to ignore this flow bleed in thecalculations. Clear the check box to re-enable it.


5 Nodes 49

Fig 5.7


Field Description

Offtake Multiplier Specify the Offtake multiplier. The default value is 0.Offtake Offset Specify the Offset for the Offtake to compensate for the changes

in the inlet flow.Offtake Minimum Specify the minimum value for the Offtake.OfftakeMaximum

Specify the maximum value for the Offtake.

Pressure Drop Enter the pressure drop across the Flow Bleed.


50 5 Nodes

Fig 5.8

Horizontal SeparatorHorizontal separators are used to allow liquid to separate from the feedstream so that it can be removed from the flare system. The liquid phase inthe horizontal separator feed is removed from the network. In Aspen FlareSystem Analyzer, the Horizontal Separator has one primary inlet, onesecondary inlet/outlet, and one vapor outlet stream.

Connections TabThe name of the horizontal separator and connectivity information is specifiedhere.

5 Nodes 51

Fig 5.9

You only need to provide 2 of 3 connections to be able to solve the separator.This allows for solution(s) to partially built networks.


Field Description

Name The alphanumeric description of the Horizontal Separator(e.g. - HP KO Drum).

Location You may want to specify the location of the node in the plant.The location can have an alphanumeric name. This feature isuseful for large flowsheets, because you can provide a differentlocation name to different sections to make it morecomprehensible.

(Primary/Secondary)Inlet/Outlet

Either type in the name of the pipe segment or select from thelist.

At You can specify the end of the pipe segment attached to thehorizontal separator.

Ignore Select the Ignore check box to ignore this horizontal separatorin the calculations. Clear the check box to re-enable it.


52 5 Nodes

Fig 5.10


Field Description

Dimensions GroupDiameter The internal diameter of the vessel.Liquid Level The liquid level in the vessel. Pressure drop is calculated based

upon the vapor space above the liquid.Methods GroupFitting LossMethod

The available options are; Equal Static Pressure Pressure drop calculation is ignored

and static pressure is balanced. Calculated_Ignore Vena Contracta Pressure drop is

calculated in accordance with the Swage method butignores the loss due vena contracta.

Calculated Pressure drop is calculated in accordance withthe Swage method including the loss due vena contracta.

5 Nodes 53

Field Description

IsothermalPressure Drop

If this option is set to Yes, the inlet temperatures used for the sizechange calculations in the separator will not update duringiterative calculations for pressure loss i.e. a PT flash will be used toupdate the inlet properties. If the option is set to No, a morerigorous PH flash will be used to update the inlet properties.The horizontal separator does three size change calculations, onebetween each stream connection and the vessel body. Normallythese will be expansion calculations for the primary and secondaryinlets and a contraction calculation for the vapor outlet but theywill automatically change if flows are reversed.Setting this option to Yes can speed up calculations in some casesat cost of a minor loss of accuracy.

Size Change GroupTwo PhaseCorrection

If this option is set to Yes, the pressure loss coefficient in twophase flow will be calculated using properties corrected for liquidslip. If set to No, the homogenous properties of the fluid will beused in calculating the pressure loss coefficient.

Method The following options are available: Compressible - Pressure losses will be calculated assuming

compressible flow through the connector at all times. Incompressible (Crane) - Pressure losses will be calculated


Transition - Pressure losses will be calculated initially usingthe assumption of incompressible flow. If the pressure lossexpressed as a percentage of the inlet pressure is greaterthan the defined compressible transition value then thepressure drop will be recalculated using the compressibleflow method.

Incompressible (HTFS) - Pressure losses will be calculatedassuming incompressible flow through the connector at alltimes. Loss coefficients are calculated using HTFScorrelations

The Incompressible method calculations are faster but will beless accurate at higher pressure drops. The Transition methodcan cause instabilities in some cases if the calculated pressuredrop is close to the transition value.

Balance Total Pressure Frictional pressure drop is ignoredand total pressure is balanced between upstream &downstream.



54 5 Nodes

Field Description

BodyDimension

If this option is set to Full Body Area, the calculation for theprimary inlet/vessel and secondary inlet/vessel size change willuse the whole vessel area. If Partial Body Area on Flow isselected, the vessel area is reduced in proportion to theappropriate flow, i.e. if the secondary inlet volumetric flow is 20%of the total volumetric flow in the tee then 20% of the body areawill be used in the size change calculation. The use of the PartialBody Area on Flow option has the effect of increasing thepressure loss calculated by simple fixed K factors.

Composition TabIf the inlet feed flashes in the separator and as a result of the flash, themixture is converted into liquid fully and the vapor outlet will have no flow.This can cause instability in the pressure solution of the whole network. Toavoid this, Aspen Flare System Analyzer creates an arbitrary vapor phase withvery small vapor fraction for the vapor outlet (

5 Nodes 55

Design Tab

Fig 5.12

Field Description

Min Drop Diameter Enter the diameter of the minimum drop size to beremoved.

Drain Volume Enter the drain volume.Maximum Holdup time Enter maximum holdup time before the horizontal

separator will be drained.Design Length Minimum length of the horizontal separator required to

satisfy design conditions.Settling Velocity Settling velocity of the minimum drop size to be removed.


56 5 Nodes

Fig 5.13

Orifice PlateAn Orifice Plate is a thin plate, which has a clean-cut hole with straight wallsperpendicular to the flat upstream face of the plate placed crossways in thepipe. Orifice plates are generally used to restrict the flow downstream of ablow down valve or restrict the flow from a high pressure section of a flaresystem to a low pressure section. They may also be used to allow flowmeasurement.

Connections TabThe name of the orifice plate and connectivity information is specified here.

5 Nodes 57

Fig 5.14


Field Description

Name The alphanumeric description of the Orifice Plate (e.g. -HP OP).

Location You may want to specify the location of the node in theplant.

Upstream/Downstream Either type in the name of the pipe segment or select fromthe list.

At You can specify the end of the pipe segment attached tothe orifice plate.

Ignore Select the Ignore check box to ignore this orifice plate inthe calculations. Clear the check box to re-enable it.


58 5 Nodes

Fig 5.15

Note: You only need to provide 1 of 3 sizing parameters. For Example, if youentered the Diameter, Aspen Flare System Analyzer will then calculate theUpstream Diameter Ratio and the Downstream Diameter Ratio.


Field Description

Dimensions GroupDiameter The diameter of the orifice hole.UpstreamDiameter Ratio

The ratio of the throat diameter to the upstream pipe diameter.

DownstreamDiameter Ratio

The ratio of the throat diameter to the downstream pipe diameter.

Methods GroupFitting LossMethod

The following options are available: Ignored - If this option is selected, the fitting losses for the

orifice plate would not be calculated. Static pressure isbalanced.

Thin Orifice - The fitting losses for the orifice plate will becalculated using the equations for the thin orifice plate.

Contraction/Expansion - For this method, orifice plates will bemodeled as a sudden contraction from the inlet line size tothe diameter of the hole followed by a sudden expansion fromthe diameter of the hole to the outlet line size.

5 Nodes 59

Field Description

IsothermalPressureDrop

If this option is set to Yes, the inlet temperatures used for the sizechange calculations in the orifice plate will not update during iterativecalculations for pressure loss i.e. a PT flash will be used to update theinlet properties. If the option is set to No, a more rigorous PH flashwill be used to update the inlet properties.The orifice plate will do one contraction calculation and one expansioncalculation if the Fitting Loss Method is set toContraction/Expansion. Setting this option to Yes can speed upcalculations in some cases at cost of a minor loss of accuracy.

Size Change GroupTwo PhaseCorrection

If this option is set to Yes, the pressure loss coefficient in two phaseflow will be calculated using properties corrected for liquid slip. If setto No, the homogeneous properties of the fluid will be used incalculating the pressure loss coefficient.




Transition - Pressure losses will be calculated initially usingthe assumption of incompressible flow. If the pressure lossexpressed as a percentage of the inlet pressure is greaterthan the defined compressible transition value then thepressure drop will be recalculated using the compressible flowmethod.

Incompressible (HTFS) - Pressure losses will be calculatedassuming incompressible flow through the connector at alltimes. Loss coefficients are calculated using HTFScorrelations.

The Incompressible method calculations are faster but will be lessaccurate at higher pressure drops. The Transition method can causeinstabilities in some cases if the calculated pressure drop is close tothe transition value.




60 5 Nodes

Summary Tab

Fig 5.16

The result of the calculations at each of the pipe connections is displayed.

TeeThe Tee is used to model the connection of three pipes. The diameters of thepipes may be different.

Connections TabThe name of the tee and connectivity information is specified here.

5 Nodes 61

Fig 5.17

You only need to provide 2 of 3 connections to be able to solve the tee. Thisallows for solution(s) to partially built networks.


Field Description

Name The alphanumeric description of the Tee (e.g. - HPTee 1).

Location You may want to specify the location of the node inthe plant. The location can have an alphanumericname. This feature is useful for large flowsheets,because you can provide a different location nameto different sections to make it more comprehensible.

Upstream/Downstream/Branch Either type in the name of the pipe segment or selectfrom the list.

At You can specify the end of the pipe segment attachedwith the tee.

Ignore Select the Ignore check box to ignore this tee in thecalculations. Clear the check box to re-enable it.


62 5 Nodes

Fig 5.18


Field Description

Dimensions GroupTheta Specify the angle of the branch to the upstream connection of the

tee.Body Specify the diameter of the body of the tee. Allowable choices are:

Run - The diameter will be that of the inlet pipe. Tail - The diameter will be that of the outlet pipe. Branch - The diameter will be that of the branch pipe. Auto - Set the body diameter to be larger of the inlet and

branch pipe diameters.Methods Group

5 Nodes 63

Field Description

Fitting LossMethod


and static pressure is balanced. Simple - This method uses a constant, flow ration

independent K factor for the loss through the branch andrun.

Miller - This method uses a K factor which is interpolatedusing Miller Curves, which are functions of the flow and arearatios of the branch to the total flow as well as the branchangle. Loss coefficients at low values of the branch are tobody area are extrapolated from the data presented on thecharts.

Miller (Area Ratio Limited) This method uses a K factorwhich is interpolated using Miller Curves, which arefunctions of the flow and area ratios of the branch to thetotal flow as well as the branch angle. The ratio of thebranch area to body area is constrained by the lower limitpresented on the charts.

Equal Static Pressure Pressure drop calculation is ignoredand static pressure is balanced.

Gardel This method calculates the K factor using theanalytical equations of Gardel.

Miller ChartExtrapolation

The available options are: None No extrapolation is used. If the data falls outside the

Miller chart, a fixed value of K (K=8.0) is used. Miller Area Ratio Squared Uses a K factor which is

extrapolated using Miller Curves, assuming that the Kfactors are functions of the flow and area ratio squared, ofthe branch to the total flow as well as the branch angle.

Gardel Uses the Gardel method to calculate K factor if theK factor is out of bounds in miller chart.

Connector IfIncomplete

If this option is set to Yes, Aspen Flare System Analyzer will treatthe Tee as a straight connector, ignoring the effect of the branch onpressure drop.The Tee will do three size change calculations between inlet/body,branch/body and body/outlet selecting expansion or contractioncalculations as appropriate.Setting this option to Yes can speed up calculations in some casesat cost of a minor loss of accuracy.


If this option is set to Yes, the inlet temperatures used for the sizechange calculations in the tee will not update during iterativecalculations for pressure loss, i.e. a PT flash will be used to updatethe inlet properties. If the option is set to No, a more rigorous PHflash will be used to update the inlet properties.

Swage Method GroupTwo PhaseCorrection


64 5 Nodes

Field Description


compressible flow through the tee at all times. Incompressible (Crane) - Pressure losses will be calculated

assuming incompressible flow through the tee at all times.Loss coefficients are calculated using Crane coefficients.


Incompressible (HTFS) - Pressure losses will be calculatedassuming incompressible flow through the tee at all times.Loss coefficients are calculated using HTFS correlations.

The Incompressible method calculations are faster but will be lessaccurate at higher pressure drops. The Transition method cancause instabilities in some cases if the calculated pressure drop isclose to the transition value.




BodyDimension

If this option is set to Full Body Area, the calculation for theinlet/body and branch/body size change will use the whole bodyarea. If Partial Body Area on Flow is selected, the body area isreduced in proportion to the appropriate flow, i.e. if the branchvolumetric flow is 20% of the total volumetric flow in the tee then20% of the body area will be used in the size change calculation.This option is ignored if the fittings loss method is set to Miller. Theuse of the Partial Body Area on Flow option has the effect ofincreasing the pressure loss calculated by simple fixed K factorsbringing the results closer to those calculated by the ore accurateMiller K factors.


5 Nodes 65

Fig 5.19

Vertical SeparatorVertical separators are used to allow liquid to separate from the feed streamso that it can be removed from the flare system. The liquid phase in thevertical separator feed is removed from the network. In Aspen Flare SystemAnalyzer, the Vertical Separator has only one inlet and one vapor outletstream.

Connections TabThe name of the vertical separator and connectivity information is specifiedhere.

66 5 Nodes

Fig 5.20

The location can have an alphanumeric name. This feature is useful for largeflowsheets, because you can provide a different location name to differentsections to make it more comprehensible.


Field Description

Name The alphanumeric description of the Vertical Separator (e.g. - HP KODrum).

Location You may want to specify the location of the node in the plant.Inlet/Outlet Either type in the name of the pipe segment or select from the list.At You can specify the end of the pipe segment attached to the vertical

separator.Ignore Select the Ignore check box to ignore this vertical separator in the

calculations. Clear the check box to re-enable it.


5 Nodes 67

Fig 5.21


Field Description

Diameter The internal diameter of the vessel.Methods GroupFitting LossMethod


and static pressure is balanced. Calculated Ignore Vena Contracta Pressure drop is

calculated in accordance with the Swage method butignores the loss due vena contracta.

Calculated Pressure drop is calculated in accordance withthe Swage method including the loss due vena contracta.


If this option is set to Yes, the inlet temperatures used for the sizechange calculations in the separator will not update during iterativecalculations for pressure loss i.e. a PT flash will be used to updatethe inlet properties. If the option is set to No, a more rigorous PHflash will be used to update the inlet properties.The vertical separator will do one expansion calculation for the inletstream entering the vessel and one contraction calculation for theflow from the vessel to the outlet. These will automatically change ifflows through the vessel are reversed.Setting this option to Yes can speed up calculations in some casesat cost of a minor loss of accuracy.

Size Change Group

68 5 Nodes

Field Description

Two PhaseCorrection






aspenflaresysanalyzerv8 0 ref

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