VisualPiper. User Guide

Transcription

1 VisualPiper User Guide

2 VisualPiper User Guide NOTICE The information in this document is subject to change without notice and should not be construed as a commitment by ABB. ABB assumes no responsibility for any errors that may appear in this document. In no event shall ABB be liable for direct, indirect, special, incidental or consequential damages of any nature or kind arising from the use of this document, nor shall ABB be liable for incidental or consequential damages arising from use of any software or hardware described in this document. This document and parts thereof must not be reproduced or copied without written permission from ABB, and the contents thereof must not be imparted to a third party nor used for any unauthorized purpose. The software described in this document is furnished under a license and may be used, copied, or disclosed only in accordance with the terms of such license. TRADEMARKS Microsoft, Windows, Excel and Visio are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. All other trademarks are the property of their respective owners. COPYRIGHT Copyright ABB Limited. All Rights Reserved. Document: VisualPiper User Guide Revision: 1.1 Published: December 2012 Software: VisualPiper Version: SUPPORT INFORMATION This program is developed, maintained and supported by PEL Support Services, ABB. We run a Hotline telephone and service to answer any queries about VisualPiper. Please let us have any suggestions on how you feel we could improve VisualPiper. You can contact us by any of the following routes: By Telephone: By Fax: +44 (0) (0) By Post: PEL Support Services ABB Limited. Daresbury Park By pel.support@gb.abb.com Daresbury Warrington Cheshire WA4 4BT United Kingdom. ii

3 Contents Preface... 1 About this guide... 1 Who should read this guide... 1 What is in this guide... 1 How this guide is structured... 1 Conventions... 2 Chapter 1 Introduction... 3 Introduction to VisualPiper... 3 VisualPiper piping system... 4 VisualPiper calculation assumptions... 4 Overview of PEL... 4 Programs for fluid flow... 5 Chapter 2 Getting started... 7 Starting VisualPiper... 7 Starting VisualPiper with a Visio drawing file... 7 Quitting VisualPiper... 7 User interface... 8 Accessing VisualPiper features in Visio Editor (data entry) dialogs... 9 Standard calculator dialogs User assistance Online help Online documentation PEL Support Services Chapter 3 VisualPiper Quick Tour Chapter 4 VisualPiper basics Calculation overview Loading a CAD drawing Loading a drawing as a template Showing or hiding the CAD drawing layer Creating a VisualPiper piping diagram Removing fittings from your diagram Entering and editing data fields Entering data fields Converting units and values Saving your VisualPiper diagram Chapter 5 Running a calculation Entering conditions data Entering data for the pipe Entering data for all the fittings in the system Entering data for an individual straight Entering data for an enlargement or contraction iii

4 VisualPiper User Guide Entering data for a bend Entering data for an orifice Entering data for an valve Entering physical properties data Specifying the VLE method Specifying the LLE method Saving the current stream Running the calculation and viewing the results Viewing physical properties results Viewing a graph of the results Viewing the results manually Saving and printing your results Printing results Saving results Generating VisualPiper reports Exporting the data to Piper Chapter 6 Standard calculators Pipe inner diameter calculator Pipe roughness calculator K-value calculator Adding tee junctions Adding bends Adding valves Adding expansions/contractions Adding User Defined (Process Equipment) items Chapter 7 VisualPiper options Describing the model Changing units Creating your own set of units Changing decimal places Changing default values Changing calculation options Changing iteration limits Quick reference Glossary Index iv

5 Preface About this guide Welcome to VisualPiper, the calculation tool for two-phase fluid flow. One of a suite of fluid flow programs for process engineers, VisualPiper calculates the pressure change or flowrate of a liquid, two-phase mixture, or gas through an unbranched closed conduit system. This guide is designed to assist you in becoming quickly familiar with the capabilities of VisualPiper, its interface and how the program is used. Who should read this guide This guide is written for users of VisualPiper to help you take full advantage of its calculation tools. If you are new to this product, we recommend that you first read The 60 Second Guide to VisualPiper. The guide assumes you are familiar with the Windows operating system. If you are new to Windows, you can find help, tutorials and support information by clicking Start > Help and Support. What is in this guide The guide contains descriptions and step-by-step instructions for all the tasks involved in using VisualPiper. How this guide is structured The chapters are organised as follows: 1. Introduction Introduces the product, outlining the database. 2. Getting started Shows how to start VisualPiper, introducing the user interface for the application. 3. VisualPiper Quick Tour Tutorial for a typical session using VisualPiper, emphasising the commonly used features. 4. VisualPiper basics Describes the overall process for running a calculation, shows how to create a basic piping diagram and how to enter data. 5. Running a calculation Shows how to enter data and calculate results for your piping diagram in VisualPiper. 6. Standard Calculators Describes the standard PEL piping calculators. 1

6 VisualPiper User Guide 7. VisualPiper options Describes the various option settings in VisualPiper. The guide also includes a quick reference section and a glossary. Conventions The following typographical conventions are used in this guide: Convention Description Bold Italic Monospace Monospace oblique To help with procedures, items that you click, select, or view may appear with the bold format (buttons, options, and window titles, for example). Proper names (software products, for example) and titles appear in the italic format. Represents any text that appears on the computer screen or text that you should type. It is also used for filenames, functions, and examples. Represents variable text where you would type in a specific value. > The chevron indicates a menu option in a procedure. For example, click File > Open, means on the File menu, click Open. 2

7 Chapter 1 Introduction Introduction to VisualPiper VisualPiper is used to calculate the pressure change or flow of a liquid, two-phase mixture or gas through an unbranched closed piping system. VisualPiper lets you: Specify the inlet & outlet pressures, or the inlet pressure and the required flowrate. Predict the point at which choking occurs, at multiple points if necessary, and calculate the maximum flowrate. Predict the change from liquid to vapour or two-phase flow. Harness the power of PhysPack using rigorous physical property calculations; Summarise key results graphically allowing you to see rapidly the changes in pressure and phase within the pipe. The pipe is drawn with Microsoft Visio using a specially designed template for inserting fittings into pipes in the correct orientation. There are purpose built forms for adding the process data with full unit conversion, pipe inner diameter calculations and roughness calculators. Changes in diameter are propagated up and down the pipe where appropriate. Tailor made reports are generated using Microsoft Word giving a complete record of the calculation input and output specific to your own requirements. VisualPiper has two modes of operation: Specify flowrate and inlet pressure. Pressure drop is calculated. If choked, the maximum non-choked flowrate is calculated. Specify inlet and exit pressures. Flow rate is calculated. If choked, all pressure discontinuities are modelled. 3

8 VisualPiper User Guide VisualPiper piping system The piping system for VisualPiper must be a single unbranched pipe. This can be made up of various sections, such as straights, bends, enlargements and contractions. Using these different sections lets you fully show the three dimensional geometry of your piping system. Overview of PEL In the VisualPiper stencil, the section types are represented by red circles. As you add various different shapes to the drawing grid, straight sections appear as the connecting lines between them. VisualPiper calculation assumptions The following assumptions are made in VisualPiper calculations: 1) Equilibrium is assumed between phases, that is, no allowance is made for heat/mass transfer limitations within a phase, between phases or between the fluid and its surrounding. 2) A homogenous model for the two phase flow is implemented. This means that no allowance is made for slip between phases. PEL is a collection of tools to enable process engineers to carry out their day-to-day tasks more quickly and reliably. The software includes purpose built programs to generate datasheets, perform engineering calculations of liquid and / or gas flow, investigate physical properties and create fault tree diagrams. Designed by engineers for engineers, the tools are intuitive and easy to use. They can be used to work out every day calculations, for troubleshooting issues such as bottlenecks, or when making plant modifications. This low cost solution will enable engineers to design processes more quickly and reliably with up-to-date and permanently available design data. Benefits Allows engineers to be more efficient and productive. With fewer manual calculations to do, tasks are carried out quicker; Improves QA and standardises procedures, through everyone using same set of data and calculations; Human errors in calculations are reduced; 4

9 Chapter 1 Introduction Improves production as bottlenecks can be identified quickly so a solution can be sought; Allows operators to get the best out of their existing assets by carrying out modifications rather than designing new ones. Programs for fluid flow VisualPiper is one of a suite of fluid flow applications built on the drawing functionality of Microsoft Visio. Together with the calculations provided by PEW, these Visual applications allow you to quickly and reliably calculate the correct size of every part of pipelines, equipment and pressure relief systems. VisualFlonet for fluid flow in networks VisualFlonet calculates the flows and pressure drops throughout your gas or liquid network. VisualAdrian for pressure relief VisualAdrian calculates flows and pressures for high velocity, compressible gases allowing the capacity of relief streams and sizing of associated equipment to be assessed. VisualPiper for two-phase fluid flow VisualPiper calculates the pressure change or flowrate of a liquid, two-phase mixture, or gas through an unbranched closed conduit system. PEW PEW is a collection of validated chemical engineering calculations relating to fluid flow, heat transfer, mixing, and vessel calibration. 5

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11 Chapter 2 Getting started This chapter shows you how to start VisualPiper and introduces the user interface for the application. Starting VisualPiper The most common way of starting VisualPiper is from the Windows Start menu, but you can also run it from a desktop shortcut. VisualPiper uses Microsoft Visio as a drawing tool to create a diagram of your piping system. To start VisualPiper from the Start menu: Click Start > All Programs > PEL > VisualPiper > VisualPiper. If using the classic Start menu or earlier versions of Windows, click Start > Programs... The application launches Microsoft Visio using the VisualPiper template. Starting VisualPiper with a Visio drawing file Once you have saved your piping system diagram as a Visio drawing file, you can start VisualPiper by double-clicking the drawing file in Windows Explorer, or in the most recent versions of Windows from the Documents Library. To start VisualPiper with a Visio drawing file: Double-click your Visio drawing file in Windows Explorer or your Documents Library. Note In more recent versions of Windows if you point at VisualPiper in the Start menu, you can select your drawing file from the list of recent files. You can also open a recent file from the File menu in Visio. Quitting VisualPiper To quit VisualPiper: 1) Do one of: On the File menu, click Exit. Click the Close (X) button. If you haven't saved any data on the current drawing, a message asks if you want to save your changes. 2) Click Save. 7

12 VisualPiper User Guide User interface Once you have started VisualPiper and Microsoft Visio has opened, you see the following, or similar, user interface. As VisualPiper is installed as an Add-In for Microsoft Visio, the look of the user interface will depend on which version of Visio is installed on your computer. This is how it looks in Visio 2007 (or earlier). The following main features are apparent: Menu bar. The standard Microsoft Visio menu contains an added menu for VisualPiper. Tool bar. Under the Visio toolbar (or toolbars) you see an added toolbar containing buttons for accessing the VisualPiper tools. Move the mouse pointer over a button to see its name. Shapes window. This standard Microsoft Visio feature shows the loaded VisualPiper stencil, which contains the various shapes you can drag onto the drawing page. Visio drawing page. The main area of the screen contains your piping system diagram. You can view this either as a floating window or maximised (as shown above). 8

13 Chapter 2 Getting started Accessing VisualPiper features in Visio 2010 If you have Microsoft Office Visio 2010 installed on your computer, this uses the ribbon interface introduced for most of the other Office applications in Microsoft Office VisualPiper opens Visio with an extra Add-Ins tab on the ribbon. This contains the VisualPiper menu and the VisualPiper toolbar. The functions are the same whether accessed from the ribbon or from the menu and toolbar. Editor (data entry) dialogs The various editor dialogs let you add or change the modelling data for your piping system diagram. The dialogs are called up from either the commands on the VisualPiper menu, by clicking the buttons on the toolbar, or by double-clicking individual components. The topological data (that is the various pipes and fittings) are automatically picked up from the Visio diagram. You use the forms to enter physical data, such as pipe lengths, and conditions, such as temperature and pressures. Many of the dialogs let you enter values for all the pipes and fittings on your diagram: other dialogs let you enter or change values for a single component. These are called either by the Edit command on the right-click context menu or by double-clicking the component. 9

14 VisualPiper User Guide Standard calculator dialogs Secondary to the editor dialogs are a number of standard piping calculator dialogs. These are standard tools provided in all the PEL programs to complete various piping parameters. The dialogs are generally called by right-clicking the field that will contain the value in the editor dialog. The editor dialogs for individual components have one or more buttons for calling the calculator next to the appropriate field. The calculator then returns a single resultant value to the field. User assistance There are standard calculators for pipe inner diameters, pipe roughness and for calculating the fittings loss (k-value). VisualPiper has the following forms of user assistance: Online help Online documentation PEL Support Services Online help VisualPiper has an integrated online help system, which provides clear reference information and step-by-step instructions for tasks. This is an online help version of this guide. To open the help system: On the VisualPiper menu, click Help User Guide. The help opens in a separate window. 10

15 Chapter 2 Getting started Online documentation Documentation is provided for PEL products on the website. The documents are provided as PDF files for you to download and print. These include: 60 second guides Online user guides PEL Support Services This program is developed, maintained and supported by PEL Support Services, ABB. We run a Hotline telephone and service to answer any queries about VisualPiper. Please let us have any suggestions on how you feel we could improve VisualPiper. You can contact us by any of the following routes: By Telephone: +44 (0) By Fax: +44 (0) By By Post: pel.support@gb.abb.com PEL Support Services ABB Limited. Daresbury Park Daresbury Warrington Cheshire WA4 4BT United Kingdom. 11

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17 Chapter 3 VisualPiper Quick Tour This short self-paced tutorial will show you how to use VisualPiper to calculate pressure drops and flow rates for a two-phase mixture in an unbranched pipe. Within 60 seconds from now you will have learned how to use VisualPiper to find out if the system below could cope with a required relief rate of 4 kg/s. Starting VisualPiper 1) Click Start > Programs > PEL > VisualPiper > VisualPiper. Click Enable Macros and the VisualPiper splash screen appears briefly on the screen. First we shall load a sketch to help us draw the pipe model. 2) On the VisualPiper menu, click Load CAD Drawing, and browse for the file C:\Program Files\PEL\Examples\VisualPiper\VisualPiper.jpg. Select the file and click Open. (Note you may have installed PEL to a different folder). Now we need to draw the pipe. 3) Drag the Contraction from the Shapes window onto the sketch at the exit of the vessel at the bottom of the pipe. 4) Drag a Bend onto the sketch at the first bend. The two are automatically connected by a straight fitting. Repeat this step for each bend in the sketch. 5) Finally drag the Enlargement onto the sketch at the end of the pipe. Now we need to specify the pipe data. 6) Click the Edit Pipe button on the toolbar. The Edit Pipe dialog opens. In the first row, specify a nominal value of 1000mm for the Diameter In for the contraction from the vessel to the pipe. Right-click the Diameter Out cell and click Pipe Inner Diameter Calculator. In the calculator dialog select 2 and schedule 40/STD/40S and click OK. You will see the diameter of 52.5mm propagate through the pipe fittings. Right-click the Roughness Out cell and select Roughness Calculator. In the calculator dialog select Mild Steel (slightly corroded) and click OK to return a value of 0.05mm. 13

18 VisualPiper User Guide Right-click the Roughness Out cell again and click Copy. Select all of the cells in the Roughness In column, right-click and click Paste. For the final Enlargement fitting, specify a Roughness Out of 0.05 mm and a Diameter Out of 1000 mm. For each bend, specify a Bend Radius of 52.5mm. Click OK. 7) In the drawing, double-click each straight section in turn and on the Edit Straight dialog, specify the Pipe length as indicated on the drawing ( 0.5m, 8m, 0.5m, 4m, 5m, 2m ), and for the vertical sections specify the Angle to Horizontal as 90 deg. Let s specify the type of calculation. We want to calculate the flow given the inlet and exit pressures. 8) Click the Conditions button on the toolbar. The Conditions dialog opens. Click Inlet & exit pressure. In the Flowrate (estimate 1) box, enter 1 kg/s; for Inlet Pressure, enter 3 barg; and for System Back Pressure, enter 1 atm. In each case, VisualPiper will convert to the correct units. Now we need to specify the Inlet Conditions. Click Inlet Temperature and then enter 120 C for the temperature. Click OK. Next, we need to define the physical properties. 9) Click the Physical Properties button on the toolbar. The dialog opens. First we need to select the components. Click Add Component and in the Search for Name box, type W. Four components are found beginning with the letter W. Select Water and click Add to Stream. In the Search for Name box, type ETHANOL and press Enter to add Ethanol to the stream. Click Close. Notice that if you click on the VLE tab, VisualPiper automatically switched the VLE Method to select Ideal Gas/NRTL. This is because mixture of water and ethanol is highly non-ideal and contains an azeotrope so the VLE method must be capable of correctly representing this non-ideality. This model will treat the vapour phase as an Ideal Gas but will use NRTL to model the non-ideality in the liquid phase. For more information on selecting the best VLE Methods click Start > Programs > PEL > Documentation > Reference Guides > Physical Properties and then select Phase Equilibrium Models. The last thing we need to do for the physical properties is to specify the composition. You can use the spreadsheet on the Feeds tab to specify the stream composition, both in terms of moles or mass, and as quantities or fractions. 10) Click on the spreadsheet to give it focus. Enter 0.5 in the Mass Fraction boxes for both Ethanol and Water. VisualPiper updates the spreadsheet. If you wish, VisualPiper will also normalise the values if they do not add up to 1. Click OK. 14

19 Chapter 3 VisualPiper Quick Tour That s it for the input. Now we re ready to run the calculations 11) Click the Calculate button on the toolbar. The word Calculating. Please wait will appear in the window. When the calculations are complete, the results appear. 12) You will see that the calculated flowrate is kg/s so the system would cope with the required relief rate. You will also see that the flow is choked, and that this is the maximum non-choking flow. There are two phases at the outlet. The graphs and tables allow you to understand the results more clearly: And that s it! How s the time doing? Did you beat the clock? If you still have time, try changing the pipe diameter to 3 Schedule 40 to see what effect this has on the relief rate. 15

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21 Chapter 4 VisualPiper basics This chapter describes the overall process in running a calculation, shows you how to create a basic piping system diagram and tells you how to enter data in VisualPiper. Calculation overview The overall process in running a VisualPiper calculation involves creating a piping diagram in Visio, entering data using the various editor dialogs and then clicking the Calculate button on the VisualPiper toolbar to generate the results. The main steps in the process are as follows: Create the Visio diagram. Drag the various shapes from the stencil to form your piping diagram. See Creating a VisualPiper piping diagram on page 18. Enter conditions. Enter the inlet flowrate and pressure, or the inlet and outlet pressures. Add the inlet temperature or mass quality. See Entering conditions data on page 23. Enter data for pipe. Enter physical data for each pipe or fitting, such as pipe length, inner diameter, roughness and fittings loss coefficient. The parameters vary for the different fittings. Use the standard piping calculators to enter many of these values. See Entering data for the pipe on page 24. Enter physical properties data. Use the Physical Properties dialog to define the composition of the two-phase mixture. Further tabs on the dialog let you define the thermodynamic model used for defining vapour-liquid equilibrium (for a liquid/gas two phase fluid) or liquid-liquid equilibrium (for a two-liquid mixture). See Entering physical properties data on page 29. Calculate. Click the Calculate button on the toolbar to generate the results for the system. On completion, the results dialog opens automatically. See Running the calculation and viewing the results on page 33. View the results. You can also open the results dialog manually. The dialog shows the summary flow rate for the pipe system. The detailed Conditions tab let you see values (such as static pressure, pressure drop and temperature) along each section of pipe or fitting. The physical properties tab shows calculated values (such as liquid and vapour molecular weight, density, viscosity and enthalpy). Commands on the dialog let you view graphs of static pressure and mass quality along the pipe. You can also 17

22 VisualPiper User Guide print the results or save them as a tab delimited text file that can be input into any spreadsheet program. Loading a CAD drawing VisualPiper lets you import a sketch or an engineering drawing to use as a template for creating your piping network diagram. The loaded image is held as a separate CAD drawing layer that you can show or hide as needed. Loading a drawing as a template To load a drawing as a template: 1) In the VisualPiper menu, click Load CAD drawing. 2) Navigate to select the file and click Open. The image appears behind the Visio drawing layer. To replace the drawing image: 1) In the VisualPiper menu, click Load CAD drawing. A prompt asks you if you want to replace the current CAD layer. 2) Click Yes. 3) Navigate to select the file and click Open. The image appears behind the Visio drawing layer. Showing or hiding the CAD drawing layer To hide the CAD drawing layer: In the VisualPiper menu, click Toggle CAD layer. The image no longer appears. To show the CAD drawing layer: In the VisualPiper menu, click Toggle CAD layer again. The image reappears behind the Visio drawing layer. Creating a VisualPiper piping diagram Basic VisualPiper diagrams show the primary pieces of your piping system and how those pieces are connected. This article describes how to quickly create a basic VisualPiper diagram in Microsoft Office Visio. For full information on creating diagrams, press F1 to open the standard Visio Help. To create a piping system diagram: 1) In Visio open a new drawing file. (In Visio 2007, click File > New > New Drawing.) 18

23 Chapter 4 VisualPiper basics 2) Ensure that AutoConnect feature is enabled. On the VisualPiper menu, point to Behavior. If a check mark is in front of the Auto Connect option then it is enabled. Otherwise click Auto Connect. 3) Drag the first shape you want from the VisualPiper stencil onto your drawing page. The shape will be selected in the drawing with selection handles around it. 4) With the shape still selected, drag a second shape onto your drawing page. The second shape is automatically connected to the first shape. 5) Continue to add shapes to complete your diagram. Removing fittings from your diagram When you amend a VisualPiper diagram in Visio you may need to remove a fitting from a section between nodes or junctions. If you set the behavior to auto healing, the program will join the shapes either side of the deleted shape. To remove a fitting from your diagram: 1) Ensure that AutoHealing feature is enabled. On the VisualPiper menu, point to Behavior. If a check mark is in front of the Auto Healing option then it is enabled. Otherwise click Auto Healing. 2) Select the shape you want to remove from your drawing page. The shape will be selected in the drawing with selection handles around it. 3) Press the Delete key. 19

24 VisualPiper User Guide The two shapes either side of the deleted fitting are automatically connected. Entering and editing data fields The Editor dialogs contain a grid of small data fields. A few of these will be text fields, but most are for entering numeric values, with or without units. Entering data fields To enter text or a value: 1) Double-click the field you want to change. Type the new text or number and then click on another cell. An alert appears if numeric data is not entered in the correct format. Click OK and correct the entry. 2) Repeat for other fields as required. 3) When you have finished, click OK. Converting units and values The units for any field appear on the dialog. These are defined on the VisualPiper options dialog. Sometimes the source data to be entered may be in different units. For example, if a pressure is shown in bar, while the source data is in psi. Rather than have to convert the value in another application, you can enter the value with the units and VisualPiper will do the conversion inline. To convert a value inline: Enter the data in the format: Value <space> units and then press Enter (or click another field). The value is converted to the units shown on the dialog. Example: For a pressure in bar, entering 50 psi converts to Saving your VisualPiper diagram When you have completed your VisualPiper diagram, you will need to save your diagram as a Visio file. When you have added data to the diagram, you will need to save the file again to save the data. 20

25 Chapter 4 VisualPiper basics To save your diagram in Visio 2007 or earlier: Do one of: Click the Save button on the toolbar. On the File menu, click Save. Press Ctrl+S. To save your diagram in Visio 2010: Do one of: Click the Save button on the Quick Access toolbar. On the File ribbon, click Save. Press Ctrl+S. 21

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27 Chapter 5 Running a calculation When you have created your piping system diagram in VisualPiper, you are ready to enter modelling data to calculate pressure and flow data. This chapter shows you how to enter data and calculate the results. It also shows you how to view graphs of the data, how to save and print the results and how to run reports. Entering conditions data The Conditions dialog lets you enter the conditions for the calculation. You can enter either flowrate and inlet pressures or inlet and exit pressures. To enter inlet and exit pressure as conditions: 1) Do one of: In the VisualPiper menu, click Conditions. On the VisualPiper toolbar click the Conditions button. The Conditions dialog opens. 2) Click Inlet & exit pressure. This is set by default. 3) Enter the following fields: Inlet Pressure, System Back Pressure, Flowrate (estimate 1/2), if required. 4) Under Inlet Conditions, click either Inlet Mass Quality or Inlet Temperature and enter the value in the associated field. 5) Click OK. 23

28 VisualPiper User Guide To enter flowrate and inlet pressure as conditions: 1) Do one of: In the VisualPiper menu, click Conditions. On the VisualPiper toolbar click the Conditions button. The Conditions dialog opens. 2) Click Flowrate & inlet pressure. 3) Enter the following fields: Actual Flowrate, Inlet Pressure. 4) Under Inlet Conditions, click either Inlet Mass Quality or Inlet Temperature and enter the value in the associated field. 5) Click OK. Entering data for the pipe Once you have entered the conditions data you have to enter the physical data for all the sections of the pipe. You can do this in two ways: use a single dialog to define all the sections in the pipe, or double-click each section to define in turn. Entering data for all the fittings in the system The Edit Pipe dialog lets you enter physical data for each pipe or fitting, such as pipe length, inner diameter, roughness and fittings loss coefficient. The parameters vary for the different fittings. Use the standard piping calculators to enter many of these values. 24

29 Chapter 5 Running a calculation To enter pipe data: 1) Do one of: In the VisualPiper menu, click Edit pipe. On the VisualPiper toolbar click the Edit pipe button. The Edit pipe dialog opens. 2) To specify the (upstream) Roughness In, right-click the field and click Roughness Calculator to open the calculator. See Pipe roughness calculator on page 40. 3) For a enlargement or contraction, repeat for the (downstream) Roughness Out. 4) To specify the (upstream) Diameter In, right-click the field and click Pipe Inner Diameter Calculator to open the calculator. See Pipe inner diameter calculator on page 39. 5) For a contraction or enlargement, repeat for the (downstream) Diameter Out. 6) For a straight, enter the fields: Pipe length, Angle to horizontal. 7) For a bend, enter the fields: Bend Angle, Bend Radius, Change in elevation. 8) For a straight or bend, enter the field: Heat flux (through pipe wall). 9) To specify a friction loss coefficient (K value) for a bend, orifice or valve, rightclick the field and click KValue Calculator to open the calculator. See K-value calculator on page ) For an orifice, enter the fields: Orifice Diameter; and, if required, the optional fields: Orifice length, Edge radius. 11) For a valve, enter the fields: Valve seat diameter, Degree of valve opening, Min. flow area. 12) Click OK. Entering data for an individual straight The Edit Straight dialog lets you enter or change values for an individual straight section of pipe. The number in the bottom corner is the item number for the straight when viewed in the Edit Pipe dialog. 25

30 VisualPiper User Guide To enter or change pipe data: 1) Do one of: Double-click the connecting line in the diagram. Right-click the connecting line in the diagram and click Edit. The Edit Straight dialog dialog opens. 2) To specify the pipe inner diameter, click the button on the right to open the calculator. See Pipe inner diameter calculator on page 39. 3) Enter or change the following fields, as required: Pipe length Angle to horizontal Heat flux through pipe wall 4) To specify the pipe roughness, click the button on the right to open the calculator. See Pipe roughness calculator on page 40. 5) Click OK. Entering data for an enlargement or contraction These similar dialogs let you enter or change values for an individual enlargement or contraction. To enter or change enlargement or contraction data: 1) Do one of: Double-click the enlargement shape in the diagram. Right-click the shape in the diagram and click Edit. 2) To specify the upstream pipe diameter, click the button on the right to open the calculator. See Pipe inner diameter calculator on page 39. 3) Repeat for the downstream pipe diameter. 4) To specify the upstream pipe roughness, click the button on the right to open the calculator. See Pipe roughness calculator on page 40. 5) Repeat for the downstream pipe roughness. 6) For a contraction, enter or change the optional coefficient of contraction, if required. 26

31 Chapter 5 Running a calculation 7) Click OK. Entering data for a bend The Bend dialog lets you enter or change values for an individual bend. To enter or change bend data: 1) Do one of: Double-click the bend shape in the diagram. Right-click the shape in the diagram and click Edit. 2) To specify the Pipe Diameter, click the button on the right to open the calculator. See Pipe inner diameter calculator on page 39. 3) Enter or change the following fields, as required: Bend radius Change in elevation Heat flux through pipe wall 4) To specify the Pipe Roughness, click the button on the right to open the calculator. See Pipe roughness calculator on page 40. 5) Enter or change the Bend Angle, as required. 6) To specify a friction loss coefficient (K value), click the button on the right to open the calculator. See K-value calculator on page 40. 7) Click OK. 27

32 VisualPiper User Guide Entering data for an orifice The Orifice dialog lets you enter or change values for an individual orifice. To enter or change orifice data: 1) Do one of: Double-click the orifice shape in the diagram. Right-click the shape in the diagram and click Edit. 2) To specify the Upstream pipe diameter, click the button on the right to open the calculator. See Pipe inner diameter calculator on page 39. 3) Enter or change the Orifice diameter, as required. 4) Either, enter or change the following fields, as required: Orifice length Edge radius Or, to specify a friction loss coefficient (K value), click the button on the right to open the calculator. See K-value calculator on page 40. 5) Click OK. Entering data for an valve The Valve dialog lets you enter or change values for an individual valve. 28

33 Chapter 5 Running a calculation To enter or change valve data: 1) Do one of: Double-click the valve shape in the diagram. Right-click the shape in the diagram and click Edit. 2) Select the valve type in the list. 3) To specify the Upstream pipe diameter, click the button on the right to open the calculator. See Pipe inner diameter calculator on page 39. 4) Enter or change the following fields, as required: Valve seat diameter Degree of valve opening Minimum available area for flow 5) To specify a friction loss coefficient (K value), click the button on the right to open the calculator. See K-value calculator on page 40. 6) Click OK. Entering physical properties data The Physical Properties dialog lets you define the composition of the two-phase mixture. Further tabs on the dialog let you define the thermodynamic model used for defining vapour-liquid equilibrium (for a liquid/gas two phase fluid) or liquid-liquid equilibrium (for a two-liquid mixture). The Feeds tab provides a stream composition worksheet, which lets you define the constituent parts of the process stream. Whenever you open the dialog the table always contains the last values used. This lets you run multiple calculations on the same fluid without having to specify or load the stream each time. You can add components to the stream and then specify the molar and/or mass quantities in the stream. 29

34 VisualPiper User Guide To enter physical properties data: 1) Do one of: In the VisualPiper menu, click Physical Properties. On the VisualPiper toolbar click the Physical Properties button. The Physical Properties dialog opens. 2) Add the various components, as described in Adding Components on page 30. The molecular weight of each component and the average molecular weight for the stream appear in the Mol Wt column on the worksheet. If you want to remove a component from the worksheet, click the component name to select the whole row, right-click the row and click Remove Selected Components. 3) Specify the quantities or realtive amounts of each component in one of the other four columns: Molar the molar quantity of each component. Mol Fraction the mole fraction of each component. Mass the mass of each component Mass Fraction the mass fraction of each component The worksheet calculates the values in the other three columns and the totals. If you enter fraction values, you must ensure that they total to 1. If you need to restart the calculation, right-click the worksheet and click Zero All Cells. 4) Click OK. To clear all components: On the Feeds tab, click Clear Worksheet. All of the components are removed from the table. Adding Components To add a component: 1) On the Feeds tab, click Add Component. The Select Components dialog opens. 30

35 Chapter 5 Running a calculation 2) Click the Databank in the list and start typing a search string. Matching entries appear in the Search Results pane as you type. 3) Select the component you want and click Add to Stream. 4) Add all the components you want and then click Close. Specifying the VLE method The VLE tab lets you specify the thermodynamic model used to calculate the vapourliquid equilibrium and the physical properties of the stream. VLE Method. You can either select the method in the list, or let the program choose based on the components in the stream. The chosen method is used to evaluate the phase equilibrium, i.e. the number of phases, the phase split and the equilibrium compositions of the individual components. Calculation Mode. Physical properties can either be calculated using the thermodynamic model ('consistent') or evaluated from the databank ('accurate'). Only certain properties can use consistent mode, e.g. fugacity, density, compressibility, enthalpy, entropy and Gibbs free energy. Properties such as heat capacity, viscosity and thermal conductivity always use accurate mode. In VisualPiper, enthalpies are always calculated using the thermodynamic model: only density and compressibility can use either mode. If you select Consistent mode, the thermodynamic model is used to calculate density and compressibility. This gives a consistent approach but the results for some properties can be significantly in error, e.g % in liquid density values. 31

36 VisualPiper User Guide If you select Accurate mode, density and compressibility are evaluated where possible from stored coefficients in the pure component databank. For the vapour phase, the Lee-Kessler method is used for the pressure corrections. Binary interaction parameters Some thermodynamic VLE models can make allowances for interactions between the components in the mixture. This feature, which is included for consistency with the PhysPack application, is intended for advanced users and is beyond the scope of this user guide. Specifying the LLE method The LLE tab lets you specify the thermodynamic model used to calculate the liquidliquid equilibrium and the physical properties of the stream. LLE Method. You can either select the method in the list, or let the program choose based on the components in the stream. The chosen method is used to evaluate the phase equilibrium, i.e. the number of phases, the phase split and the equilibrium compositions of the individual components. Saving the current stream The Files tab lets you save the current stream on the Feeds tab as a file or recall a previously saved stream file. The saved file (.psm) contains the components and the calculated molar/mass quantities, fractions and totals. To save the current stream: 1) Click the Files tab. 2) Click Save. 3) Change the file name and location, if required, and click Save. To open a saved stream: 1) Click the Files tab. 2) Click Open. 3) Browse to select the stream file and click Open. The recalled stream now appears on the Feeds tab. 32

37 Chapter 5 Running a calculation Running the calculation and viewing the results When you have entered all the data for your calculation you are ready to run the calculation and view your results. To run the calculation: Do one of: On the VisualPiper toolbar, click the Calculate button. On the VisualPiper menu, click Calculate. When the calculations are complete, the results appear in the Results of Calculation dialog. The dialog shows the overall success of the calculation, together with any warnings and the summary flow rate for the pipe system. The lower part of the dialog contains two tabs showing detailed data for each pipe section in your system. The Conditions tab let you see values, such as static pressure, pressure drop and temperature. The physical properties tab shows calculated values, such as liquid and vapour molecular weight, density, viscosity and enthalpy. The toolbar at the top provides options for saving and printing the results and for viewing graphs of the static pressure and mass quality changes along the pipe. 33

38 VisualPiper User Guide Viewing physical properties results The Physical Properties tab shows calculated values (such as liquid and vapour molecular weight, density, viscosity and enthalpy). Viewing a graph of the results In-built graphs let you see how the static pressure or mass quality changes through the sequence of sections along the pipe. Various commands on the context (right-click) menu let you print the graph or copy the image to the clipboard, so that you can paste the image into a report. You can also change the formatting of the axes, title and legends or even the chart type, if you wish. To view a graph of static pressure changes along the pipe: On the Detailed Results dialog, click the Static Pressure button. The Pressure Graph opens in a pop-up window. The graph plots static pressure (y-axis) against the sections along the pipe (xaxis). 34

39 Chapter 5 Running a calculation To view a graph of mass quality changes along the pipe: On the Detailed Results dialog, click the Mass Quality button. The Mass Quality Graph opens in a pop-up window. The graph plots mass quality (y-axis) against the pipe sections (x-axis). To print the graph: 1) Right-click the graph background and click Print. The Print dialog opens. 2) The Print Setup tab let you select a printer. Your default is already selected. Click the tab to select a different printer. 3) The Page Setup tab lets you fit the graph to the page and set margins. Click the tab if you need to change the settings. 4) On the Print tab, change the layout option, if required, and click Print. Viewing the results manually You can also open the results dialog without running the calculation. This opens the Results of Calculation dialog, showing the last set of calculated results. To view results (without running the calculation): Do one of: On the VisualPiper toolbar, click the Results button. On the VisualPiper menu, click Results. The Results of Calculation dialog opens showing the last run results. 35

40 VisualPiper User Guide Saving and printing your results The Results of Calculation dialog contains command options to let you print the results or export the results data to a tab delimited text file that can be imported into an Excel spreadsheet. Printing results You can print the results of your calculation on the Results of Calculation dialog. The full results are sent to the printer, that is the summary information, the conditions for each pipe section and the detailed physical properties of each pipe section. To print the results: 1) On the Results of Calculation dialog, click the Print button. 2) Choose you printer and click OK. The results are sent to the printer. Saving results You can save the results of your calculation on the Results of Calculation dialog. The full results are saved, that is the summary information, the conditions for each pipe section and the detailed physical properties of each pipe section. By default, you save the results as a tab delimited file. You can also save the results as an Excel spreadsheet or as an XML or HTML file. To save the results: 1) On the Results of Calculation dialog, click the Save button. 2) Enter a name for the file, browse to where you want to save the file and click Save. A message tells you the file has been sucessfully saved. 3) Click OK. Generating VisualPiper reports The reports facility lets you output information on your VisualPiper calculation to a Word document. The report can include your piping system diagram, the entry data and the results. 36

41 Chapter 5 Running a calculation To generate a report: 1) Do one of: In the VisualPiper menu, click Reports. On the VisualPiper toolbar click the Reports button. The Report Options dialog opens. 2) Select one or more of the check boxes and then click Generate. The report is generated as a Word document containing the selected items. 3) Click the Save button on the toolbar, browse to where you want to save the file and click Save. Exporting the data to Piper The Export to Piper feature lets you export your data entered in VisualPiper as an scd file so that it can be opened in the original Piper application. To export the data to Piper: 1) If you haven t already done so, save the drawing and data to a Visio file. 2) In the VisualPiper menu, click Export to Piper. A message appears telling you that the file has been saved to the same folder as the Vision file. 3) Click OK. 37

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43 Chapter 6 Standard calculators VisualPiper contains a number of calculators that are used to complete various process values for you. The standard piping calculators provide physical data and calculations for standard pipes and fittings. This chapter shows you how to use these calculators. They are common to all of the PEL applications. Pipe inner diameter calculator This calculator returns a pipe s inner diameter (in mm) based on the standard pipe size and the available pipe schedules for that pipe size. The calculator supports both the American (ANSI/ASME/API) pipe sizes standard, which is in imperial units, and the European (DIN) system which uses metric units. The calculator also derives the external diameter and the wall thickness. The American standard pipe sizes range from 1/8 inch up to 36 inch. The schedules, which give the pipe thickness, range from 5S up to XXS (Double Extra Strong). To calculate a pipe internal diameter: 1) Do one of: On the Edit Pipe dialog, click the field that is to contain the pipe inner diameter. Right-click the field and click Pipe Inner Diameter. On a component editor dialog, click the button next to the field. 2) Click the required standard in the drop-down list, select the required pipe size in the left pane and then select the schedule in the right pane. The calculated values appear in the three boxes at the bottom of the dialog, with the inner diameter selected for return. 3) Click OK. The inner diameter value is returned to the datasheet field. 39

44 VisualPiper User Guide Pipe roughness calculator This calculator is used to return an absolute roughness value for a pipe s internal surface. A smooth surface such as glass or plastic has a low roughness value, while badly corroded metal or brick has a high roughness. The values are in millimeters. To calculate a pipe roughness: 1) Do one of: K-value calculator On the Edit Pipe dialog, click the field that is to contain the absolute roughness. Right-click the field and click Pipe Roughness. On a component editor dialog, click the button next to the field. 2) Select the required Surface Type in the list and click OK. The absolute roughness value is returned to the datasheet field. The Fittings Loss (K-value) calculator is a multi-stage tool that enables a process engineer to enter details of all the various fittings, such as bends, valves and t- junctions, that contribute to pressure drop in a piping system. The total loss calculation appears on the Summary tab, which is the default view when you call the calculator. 40

45 Chapter 6 Standard calculators To calculate the fittings loss (K-value): 1) Do one of: On the Edit Pipe dialog, click the field that is to contain the fittings loss. Right-click the field and click K Value Calculator. On a component editor dialog, click the button next to the field. 2) Add the various fittings on the other tabs as defined in the following sections. As you add details on a tab, the total loss for that tab appears on the summary tab. 3) If you need to enter any Manual Adjustment, enter the value and add a reason for the adjustment (optional). The manual adjustment field is for entering miscellaneous fittings not covered on the other tabs. You can also use it to manually adjust the model in the validation stage or for studying the effect of changes, such as a control valve position. 4) When you have completed the calculation click OK. The total loss value is returned to the datasheet field. Note As the calculator retains the values last used, you can click OK to save the calculation at any stage and then restart the calculator to continue. Adding tee junctions The Tee Junctions calculation takes into account any blanked off junctions. This can also be a line where the dead leg is isolated at a valve further downstream. To add tee junctions: 1) On the Fittings Loss Calculator dialog, click the Tee Junctions tab. 2) Click the Tee Junction Type in the list, enter the Quantity and click Add. The items are added to the table at the bottom of the tab, with the loss shown for each addition. The total for all junctions appears on the Summary tab. To delete tee junctions: Select the entry in the table and click Delete. The entry is removed from the calculation. 41

46 VisualPiper User Guide Adding bends Bends are added in a similar way to tee-junctions. To add bends: 1) On the Fittings Loss Calculator dialog, click the Bends tab. 2) Click the Bend Type in the list, enter the Radius (of the bend) and the Diameter (of the pipe), enter the Quantity and click Add. Note You can enter any two of the radius, the diameter and the ratio of the two. If you enter the radius and the diameter, the ratio is calculated. If you enter the ratio and one other parameter, the omitted parameter appears as unspecified. The items are added to the table at the bottom of the tab, with the loss shown for each addition. The total for all bends appears on the Summary tab. To delete bends: Select the entry in the table and click Delete. The entry is removed from the calculation. Adding valves Valves are defined by type and by one or more categories within the type. For example, the Globe Valve type has two categories cast valves and forged valves. 42

47 Chapter 6 Standard calculators To add valves: 1) On the Fittings Loss Calculator dialog, click the Valves tab. 2) Double-click the Valve Type in the list and select the category you want. 3) Click the Pipe Size in the list, enter the Quantity and click Add. The items are added to the table at the bottom of the tab, with the loss shown for each addition. The total for all valves appears on the Summary tab. To delete valves: Select the entry in the table and click Delete. The entry is removed from the calculation. Adding expansions/contractions This tab is for adding expansion and contraction joints to the calculation. For exit losses: Select an expansion with a small/large area ratio of zero. For entry losses: Select a contraction with a small/large area ratio of zero. To add expansions or contractions: 1) On the Fittings Loss Calculator dialog, click the Expansions/contractions tab. 2) Click Contraction or Expansion, as appropriate, enter the Large Area, the Small Area, enter the Quantity and click Add. Note You can enter any two of the large area, the small area and the ratio of the two. If you enter the two areas, the ratio is calculated. If you enter the ratio and one other parameter, the omitted parameter appears as unspecified. You can also edit the calculated ratio for entry and exit losses. The items are added to the table at the bottom of the tab, with the loss shown for each addition. The total for all expansions appears on the Summary tab. To delete expansions or contractions: Select the entry in the table and click Delete. The entry is removed from the calculation. 43

48 VisualPiper User Guide Adding User Defined (Process Equipment) items The easiest way to model process equipment (for example, heat exchangers and filters) is as a section of pipe with a fitting loss coefficient. The pipe length needs to be short so that the pressure drop is solely due to the fittings 1m is generally used. The values for mass flow, pressure drop etc. can be obtained from the process data sheet. Static head changes between inlet and outlet should not be taken into account as the node information deals with this. To add process equipment: 1) On the Fittings Loss Calculator dialog, click the User Defined tab. 2) Enter a name for the item and specify the following items: Pipe Inner Diameter Flow Rate Density Pressure drop 3) Enter the Quantity and click Add. The items are added to the table at the bottom of the tab, with the loss shown for each addition. The total for all process equipment appears on the Summary tab. To delete a process equipment item: Select the entry in the table and click Delete. The entry is removed from the calculation. 44

49 Chapter 7 VisualPiper options This chapter describes how you can change the various options settings that determine how VisualPiper works. Describing the model The Model tab on the VisualPiper Options dialog lets you enter a detalied description of the model used for the VisualPiper calculation. To add a model description: 1) Do one of: On the VisualPiper toolbar click the Options button. In the VisualPiper menu, click Options. The VisualPiper Options dialog opens. 2) Enter a title for the model. 3) In the Comments field, add a detailed description. 4) Click OK to save the changes. 45

50 VisualPiper User Guide Changing units The Units tab on the VisualPiper Options dialog lets you select the units for process values to appear in all the editor and results dialogs. Three predefined set of units are provided: Engineering units the units most commonly used in the chemical process industries. They are mostly SI units, but with a few variants, such as Parameter SI unit Engineering unit Temperature K (Kelvin) C (Celcius) Pressure N/m2 bar Dynamic viscosity N.s/m2 cp (centipoise) Other units differ just by degree, such as mm for short length (instead of m). SI units the international system of units, the standard metric system British units standard UK (Imperial) or US units Engineering units are the default set when you install VisualPiper.You can set one of the other predefined sets as the default or compile your own set. To change the units to a predefined set: 1) Do one of: On the VisualPiper toolbar click the Options button. In the VisualPiper menu, click Options. The VisualPiper Options dialog opens. 2) Click the Units tab. 3) Click the button for the set you want to use, such as SI. 46

51 Chapter 7 VisualPiper options A prompt asks you if you want to select these units as the default so that the set is loaded next time you start VisualPiper. 4) Click Yes. The selected set appears in the dialog. 5) Click OK to save the changes. Creating your own set of units The Units tab on the VisualPiper Options dialog lets you compile your own set of units. You can save these changes to a file and reload as you need. The units file is saved by default to the PEL/Apps folder where VisualPiper is installed. You can save the file elsewhere. To create a new set of units: 1) On the Units tab on the VisualPiper Options dialog, click the unit you want to change to select the cell in the table. 2) Right-click the cell and click one of the alternative units in the context menu. 3) Repeat for other units as required to complete your set. 4) Click Save units to file, enter a name for file (the default is UserUnits.uns), browse to where you want to save the file (optional) and click Save. To load an existing set of units: 1) On the Units tab on the VisualPiper Options dialog, click Get units from file. 2) Browse to where the file is saved (if not the PEL/Apps folder) and click Open. A prompt asks you if you want to select these units as the default so that the set is loaded next time you start VisualPiper. 3) Click Yes. The selected set appears in the dialog. 4) Click OK to save the changes. 47

52 VisualPiper User Guide Changing decimal places The Decimal Places tab on the VisualPiper Options dialog lets you select the number of decimal places to be shown for various process values on all the editor and results dialogs. To change the settings: 1) Do one of: On the VisualPiper toolbar click the Options button. In the VisualPiper menu, click Options. The VisualPiper Options dialog opens. 2) Click the Decimal Places tab. 3) Change the number of decimal places for a particular parameter as required. 4) If you want to save the changes so that they are reloaded next time you start VisualPiper, click Save As Defaults. Otherwise the changes will just apply to this session. 5) Click OK to save the changes. 48

53 Changing default values Chapter 7 VisualPiper options The Default Values tab on the VisualPiper Options dialog lets you set default values for common pipe parameter, such as diameter and roughness. To change the settings: 1) Do one of: On the VisualPiper toolbar click the Options button. In the VisualPiper menu, click Options. The VisualPiper Options dialog opens. 2) Click the Default Values tab. 3) To change the default for Diameter, click the button on the right to open the calculator. See Pipe inner diameter calculator on page 39. 4) To change the default for Roughness, click the button on the right to open the calculator. See Pipe roughness calculator. on page 40 5) To change the default for Valve: seat diameter, click the button on the right as before. 6) To change any of the remaining defaults, double-click the value to select and type the new default. 7) If you want to save the changes so that they are reloaded next time you start VisualPiper, click Save As Defaults. Otherwise the changes will just apply to this session. 8) Click OK to save the changes. 49

54 VisualPiper User Guide Changing calculation options The upper part of the Calculation tab on the VisualPiper Options dialog lets you set various control parameters that determine how the calculations are run. To change the settings: 1) Do one of: On the VisualPiper toolbar click the Options button. In the VisualPiper menu, click Options. The VisualPiper Options dialog opens. 2) Click the Calculation tab. 3) Change the values, as required: Convergence tolerance. Enter a percentage. You can save considerable time by relaxing this tolerance and avoiding unnecessary iterations of the program when calculating flowrates, especially if these are close to choked. Physical properties diagnostic level. Select one of the levels from the list: Terminal errors only. Displays an output message only if a terminal error occurs (default setting). All errors. Displays an output message if any terminal or non-terminal error occurs. This also provides a summary of violations of temperature and pressure ranges for physical properties. All errors, with details. Displays an output message if any terminal or non-terminal error occurs. This also provides a table of temperature and pressure ranges for physical properties together with details of all violations of the ranges. Piper diagnostic level. None. Select one of the levels from the list: No diagnostic information displayed (default setting). Summary. Provides a summary of the calculation through the system at each flowrate. Detailed. Provides a summary of the calculation through the system at each flowrate plus the inlet and outlet conditions for each section at each flowrate. Diagnostics Level 3,4. Provides a summary of the calculation through the system at each flowrate plus the inlet and outlet conditions for each section 50

55 Chapter 7 VisualPiper options at each flowrate. Details of the course of the iterations in each section are shown as they proceed. Individual conduit diagnostics level. Select one of the levels from the list. The levels are as above. Executive diagnostic level. as above. Select one of the levels from the list. The levels are Display inlet stream and conduit level. Click Yes or No. 4) Click Save as default. 5) Click OK to save the changes. To reset to the saved default settings: Click Reset to Default. To reset to the system settings: Click Reset to System Default. Changing iteration limits The lower part of the Calculation tab on the VisualPiper Options dialog lets you set various control parameters that determine how the calculations are run. These settings affect the solvers that perform the calculations. Contact the PEL support desk on the Hotline telephone service if you want to make changes. 51