11-5538 JS ReliefSizing Refresh

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Jump Start: Relief Sizing in Aspen HYSYS® and Aspen Plus® V8.6

A Brief Tutorial (and supplement to training and online documentation)

Anum Qassam, Product Management, Aspen Technology, Inc.Jennifer Dyment, Product Marketing, Aspen Technology, Inc.Wilfried Mofor, Product Management, Aspen Technology, Inc.


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Table of ContentsIntroduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Initial Set Up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Adding a Pressure Relieving Device to a Simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Entering the Simulation Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Adding a PRD to the Safety Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Initial PRD Set Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Equipment Tab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

PRD Data Tab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Rating Tab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Creating A Scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Scenarios Tab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Scenario Setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Sizing Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Custom Orifice Sizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Line Sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Equivalent Length Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Documentation Builder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Importing Valve Sizing and Scenarios within Aspen Flare System Analyzer from Aspen HYSYS/Plus . . . . . . . . . . . . . . . . . . . 19

Relief Valve Sizing and Dynamic Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Additional Resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24



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IntroductionWhen designing a chemical process and its equipment, safety is of substantial concern. All possible strategies should be

considered to eliminate the risk of accident and injury when implementing a process design. One safety concern that

frequently occurs in a plant is the over-pressurization of equipment or piping. In order to prevent dangerous bursts,

explosions, and fires, pressure relief valves are designed and installed to bleed out excess liquid or vapor causing pressure

build-up.

Process conditions vary at each location of a pressure relief valve. Because of this, and the strict regulation of safety

equipment, completing a design of a pressure relief valve by hand can be a time-consuming and laborious exercise. To

solve this problem, Aspen HYSYS® and Aspen Plus® have a pressure safety valve sizing feature available within the Safety

Analysis Environment, which uses data from a process simulation to help automate PSV calculations.

The Safety Analysis Environment uses common valve design standards, most notably API 520, 521, to determine pressure

relief valve sizing information and values. Twenty-five common overpressure scenarios are included in the software, which

can be analyzed and sized. The Safety Analysis Environment also features a line sizing functionality, allowing the user to

quickly choose the schedule and diameter according to pressure drop and fluid velocity constraints for piping entering and

leaving the pressure safety valve. Line sizing is completed in the Safety Analysis Environment without having to perform

any fluid flow computations.

The Documentation Builder pulls valve sizing and process variable information directly from simulation to automatically

complete required forms that normally require manual incorporation.

This guide will walk the reader through the process of using the pressure relief valve features within the Safety Analysis

Environment of Aspen HYSYS and Aspen Plus to design a pressure relief valve. AspenTech recommends that a range of

other resources be called upon in conjunction with this document to give the user a comprehensive view of how to use

Aspen HYSYS and Aspen Plus. These may include:

• AspenTech support website (support.aspentech.com) – this website has a wealth of information on the use of

AspenTech products and provides answers to frequently asked questions

• AspenTech courseware available in on-line and in-person versions

• AspenTech business consultants

This document will show how to size pressure safety valves using Aspen HYSYS and Aspen Plus. It assumes that the user

has Aspen HYSYS or Aspen Plus V8.6 or higher installed on her or his computer and a functional process design

completed.

support.aspentech.com


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Initial Set UpAll examples and screenshots in this guide are based on the example file “PRESSURE RELIEF STARTER.hsc” in Aspen

HYSYS. If more familiar with Aspen Plus, users can use the “Safety Analysis without PRD.bkp” file instead. Make sure that

the correct units are selected when specifying parameters.

Adding a Pressure Relieving Device to a SimulationThis section of the document describes how to enter the Safety Analysis Environment and how to add a relieving device to

the flowsheet.

Entering the Simulation Environment

In order to add a pressure safety valve to a process flowsheet, the user must enter the Safety Analysis Environment. This

environment provides a setting for relief scenario setup and PSV sizing and documentation.

After designing a process in Aspen HYSYS or Aspen Plus and converging the simulation, click on ‘Pressure Relief’ in the

Home ribbon of the Simulation Environment to enter the Safety Analysis Environment. Alternatively, the Safety Analysis

button, located on the bottom left of the program, can be used. The various options to enter the Safety Environment are

shown in the figures below.

Figure 1: Pressure Relief Button on Home Tab in Aspen HYSYS

Figure 2: Pressure Relief Button on Home Tab in Aspen Plus

Figure 3: Safety Analysis Button on Navigation Pane



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Adding a PRD to the Safety Environment

After entering the Safety Analysis Environment, select the Unit Operations heading in the navigation pane on the left side

of the screen. This will display all the unit operations and subflowsheets present in the simulation for which a pressure

safety valve can be designed. Also in the navigation pane is the Unattached Streams heading, in which floating/dangling

streams with no connections to process models are listed. The last heading, Storage Tank Protection, lists any additional

low pressure storage tanks created in the Safety Analysis Environment. Storage tank protection is discussed more in detail

in Jump Start: Storage Tank Protection in Aspen HYSYS® and Aspen Plus®.

Figure 4: Location of Unit Operations and Unattached Streams Menus in Safety Analysis Panel

To add a PRD to a simulation, click the Add PSV or Add Rupture Disk button on the Home tab of the ribbon in the Safety

Analysis Environment, shown in Figure 5.

Figure 5: Add PSV Button in Safety Analysis Environment


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This switches the cursor into attach mode. When you hover over attachable objects on the flowsheet, a blue box will

appear to indicate where to click to make the attachment to the stream. Click on the blue box to add the safety valve to

that stream. See Figure 6 for more detail.

Figure 6: Attach Mode in Safety Analysis Environment

A PSV or Rupture Disk can also be added using the navigation pane. Expand the Unit Operations or Unattached Streams

node and right click the desired block or stream. Scroll to highlight either the Create PSV or Create Rupture Disk option.

The user can add either a PSV or a Rupture Disk to any stream exiting a unit operation (Figure 7).

Figure 7: Adding a Pressure Safety Valve From Navigation Pane

For users that are following along with the example file, the flowsheet should now look like the flowsheet in Figure 8.



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Figure 8: Flowsheet with Added PSV in Aspen Plus and Aspen HYSYS

Initial PRD Set UpThis section of the document highlights the Equipment, PRD Data, and Rating tabs. Double click the relief device on the

flowsheet to open the PRD form.

Equipment Tab

The PRD form opens to the Equipment tab. The Equipment tab, shown in Figure 9, allows the user to specify the operating

and design conditions of the limiting unit operation within the PRD system.

Figure 9: PRD Form - Equipment T


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PRD Data Tab

The PRD Data tab, shown in Figure 10, allows you to fully specify PRD-specific parameters. This tab is also used to create

multiple valves to protect the system and is discussed more in detail in Jump Start: Multiple Relief Valve Analysis in Aspen

HYSYS® and Aspen Plus®.

Figure 10: PRD Form - PRD Data Tab

Rating Tab

The Rating tab, shown in Figure 11, allows you to design one or more valves for the sizing case scenario. The Rating tab

further allows you to see the effect of the chosen PRD configuration on all scenarios.

Tip: On the equipment tab, the user can manually specify the operating and design temperatures and pressures by

selecting “Manual” in the dropdown menu. Reference the temperatures and pressures of the stream to which the PRD

is attached by selecting “Reference” in the dropdown menu. If the stream conditions in the flowsheet are changed,

referenced values will automatically update.



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Figure 11: PRD Form - Rating Tab

Creating A ScenarioThis section of the document describes how to create a scenario for analysis.

Scenarios Tab

The Scenarios tab, shown in Figure 12, allows the user to manage multiple overpressure scenarios in the system. In this

tab, the user can also specify which of the scenarios is the sizing case. The sizing case will be used to design the PRDs that

protect the system.

Figure 12: PRD Form - Scenarios Tab

The user can create a scenario by clicking the Create Scenario button, shown in Figure 13. Open the scenario by selecting

it and clicking the Open Scenario button or delete scenarios using the Delete Scenario button. In Aspen HYSYS, the user

can Duplicate a scenario by clicking the Duplicate & Rename button. This capability is not available in Aspen Plus.


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Figure 13: Scenario Tab Options

Click the Create Scenario button to add a scenario to the table as shown in Figure 14.

Figure 14: Newly Created Scenario

Double click the scenario from the table to open the Scenario Setup form.

Scenario Setup

After double-clicking on a scenario from the Scenarios tab or choosing a scenario from the navigation pane, the Scenario

Setup tab, shown below, appears (Figure 15).

Figure 15: Scenario Setup Tab

The user can enter the Scenario Name, which is used for documentation purposes. Next, select the Scenario Type from

the dropdown menu. Scenarios that are highlighted in the dropdown have additional optional associated calculation

methodologies to determine the Required Relieving Flow.

Enter the relieving temperature necessary for the given relief scenario being analyzed before proceeding to the calculation

of the relieving pressure. Click the Edit button next to the Relieving Pressure box to bring up the window shown in Figure

16.



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Figure 16. Relieving Pressure Calculation Window

In the Relieving Pressure Calculation window, you can specify the Allowable Overpressure for the scenario. The Relieving

Pressure is determined from the specified Allowable Overpressure. Verify that the relieving pressure is correct, then click

OK to continue.

Similar to the Relieving Pressure Calculation window, clicking Edit next to the Total Backpressure box opens the window

displayed in Figure 17. In this window, you can specify the Variable Superimposed BP and Built-up Backpressure to

calculate the Total Backpressure. Furthermore, you can specify the Maximum Allowable BP % and the Backpressure (BP)

Factor (Kb). Verify that the parameters are correct, then click OK to continue.

Figure 17. Backpressure Calculation Window

To obtain a relieving flow load, a manually calculated value can be entered or the reference flow value from the Reference

Stream can be used. Figure 18 shows a completed scenario calculation.

Calculating a Required Relief Flow is discussed in more detail in Jump Start: Fire Overpressure Analysis in Aspen HYSYS® and

Aspen Plus®.


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Figure 18: Completed Example of Scenario Calculation

When all scenario input is complete, the PSV Results box will display the valve sizing results in the table on the right-hand

side of the tab, detailed in the next section of this guide.

Sizing ResultsAfter finishing parameter input in the Valve Design and Scenario Setup tabs, the valve sizing results will be displayed in

the Valve Results table (Figure 19), located within the Scenario Setup tab.

Figure 19. Valve Results Table Inside Scenario Setup Tab



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The results table includes important information required to choose an appropriate safety valve for installation. The

calculated orifice area and valve coefficient are given. Also provided is the level of noise, in decibels, that the valve will

make at a given height when in use.

Using the calculated orifice area, the user is prompted to select an actual standardized orifice size for the valve from a

dropdown menu in the Valve Results table. It is recommended to pick the next largest orifice size from the calculated

orifice size in order to ensure correct valve operation. For example, in Figure 20, because the calculated orifice is 9.152 in2,

you should select the 11.050 in2 option from the dropdown menu. After selecting an orifice size, the valve’s rated capacity

and capacity used is displayed, along with orifice design information and in and out flange sizing.

Figure 20. Selected Orifice Dropdown Box with Options

If the scenario being analyzed is the basis case for which the valve is sized, select the “Sizing Case” box, next to the

Scenario Name input box. Then, return to the Valve Design tab to proceed to line sizing for the relief valve.

For Rupture Disk (RD) devices, a list of commonly available disk sizes is used based on common disk sizes as shown

below (Figure 21).

Figure 21. Rupture Disk Device Orifice Selection


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Custom Orifice Sizing

The selectable orifice sizes that come standard in Aspen HYSYS and Aspen Plus are based off of API 526 standards. If

different orifice sizes are necessary, custom orifice sizes can be specified by going to the “Customize” tab on the ribbon in

the Safety Analysis Environment and clicking the “Custom Orifices” option (Figure 22).

Figure 22. Accessing Custom Orifice Editing

Clicking the “Custom Orifices” option opens a window in which the selectable orifice areas and displayed names can be

updated to fit the user’s needs. To edit an orifice, check the box under the “Add Custom” column, and then type the

appropriate name and orifice area. The Custom Orifices window is shown in Figure 23.

Figure 23. Custom Orifice Area Editing

Line Sizing

After the orifice area has been selected for the appropriate sizing scenario, return to the Valve form. The scenario list in

the Valve Design tab will now be populated with sizing information regarding each scenario. If not done before, use the

“Sizing Case” check box on the scenario list (Figure 24) to choose which failure scenario the valve will be sized for.



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Figure 24. Scenario List Table Inside Valve Design Tab with Selected Sizing Case Scenario

Selecting a sizing case enables the “Line Sizing” tab for selection. Click the Line Sizing tab, as shown in Figure 25, to begin

line sizing for the pressure safety valve.

Figure 25. Location of Line Sizing Tab

Under the Line Sizing tab, the piping in and out of the pressure safety valve can be chosen. If the pipe size chosen by the

user is too small to accommodate relief flow or too large such that the pressure gradient will not allow for relief flow, the

Safety Analysis Environment will alert the user using the bar on the bottom of the tab, so that an incorrect design is not

selected. If the bar is green, it means that an appropriate line size has been selected, while yellow means there is either a

fluid pressure or velocity constraint being violated by the chosen line sizing.

Specify the nominal diameter and schedule of the piping for the in and out lines. The Safety Analysis Environment will use

the rated flowrate through the pipes to calculate the change in pressure and velocity (For most cases, rated flowrate is

used. The design/required flow through the PSV is used for liquid or fire scenarios. This value can be changed if the Safety

Analysis Environment defaults do not match.) These results are displayed in the “Line Sizing Results” table. Figure 26

shows the Line Sizing tab layout.

Figure 26. Layout of Line Sizing Tab


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The pressure drop and fluid velocity constraints for line sizing are preset according to API standards. To change these

constraints, click the “Constraint Setting” button in the Line Sizing tab, and the following window (Figure 27) will open

allowing the user to change line sizing constraints as desired.

Figure 27. Line Sizing Constraint Settings

Equivalent Length Calculation

The equivalent length of the piping can be entered in the appropriate field inside the Line Sizing tab. There is also a feature

in the Safety Analysis Environment which calculates the equivalent length of the piping. To access this feature, check the

“Calculate Equivalent Length” box. This will bring up a menu within the Line Sizing tab in which the quantity of the present

pipe fittings can be specified, along with their L/D ratios. After entering the number of fittings, a calculated equivalent

length will appear, as shown in Figure 28.

Figure 28. Calculate Equivalent Length Function



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Documentation BuilderAfter completing all design and sizing for a pressure relief valve, filling out documentation is required in order to meet

regulated safety compliances, and for valve vendor submission. In order to reduce tedium in this area, the simulators have

a Documentation Builder function inside the Safety Analysis Environment, which pulls data from the simulation and valve

sizing to automatically complete required forms. To access the customizable Documentation Builder, click the

“Documentation Builder” option from the home ribbon. Similarly, to obtain a built-in PRD report, choose the desired

option located to the left of the Documentation Builder option, shown in Figure 29.

Figure 29. Documentation Builder and Built-in Simulator Reports Options While in Safety Analysis Environment

The Built-in Safety Analysis Environment Reports feature provides instant documentation of valve parameters and

relieving conditions gathered directly from the Safety Analysis relief scenario being analyzed. Built-in reports are not

editable; the Documentation Builder should be used for more in-depth, editable reporting. Shown in Figure 30 is an

example built-in calculation sheet .

This calculation sheet is the report used for the storage tank analysis and works either in context with the tank protection

system or while on the “Tank Manager” form. For Storage Tanks and Fire Relief Load Calculation reports, the built-in

reports are available in both SI and EN sets.

Figure 30. Example Built-in Safety Analysis Environment PSV Calculation Report (Only Report Available for Storage Tanks)


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Clicking the Documentation Builder option initiates Microsoft Access, which houses the customizable forms to be

completed after designing and sizing a pressure relief valve. From the Documentation Builder’s home screen, shown below

in Figure 31, a list of relief devices sized in the Safety Analysis Environment can be edited or viewed. Additionally, process

data sheets, mechanical data sheets, calculation summary sheets, or relief load summary sheets can be constructed.

Information from the sheets can be exported to Microsoft Excel by selecting any of the respective “Export” options.

Figure 31. Microsoft Access Documentation Builder Selection Screen

Choosing the edit option for any of the forms from the Documentation Builder brings up a screen allowing the user to

change the information that will appear in the final, viewable report. Many entries are already populated by values pulled

directly from the Safety Environement. These are denoted in grey/green. The spaces in white require user input to be

completed. A sample edit page for a mechanical data sheet is shown in Figure 32.



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Figure 32. Edit Page for Mechanical Data Sheet

After entering the pertinent information for a datasheet on its edit page, return to the Documentation Builder home

screen, then select “View” to see a copy of the finalized version of the document chosen. After opening a document using

the “View” option, it can then be saved electronically or printed. Figure 33 shows a completed sample mechanical data

sheet, given the input information from the edit page shown in Figure 32.


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Figure 33. Completed Example Mechanical Data Sheet

Completing documentation using the Documentation Builder reduces the time needed to complete safety valve

paperwork to submit to regulatory agencies and valve vendors.



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Importing Valve Sizing and Scenarios within Aspen Flare SystemAnalyzer from Aspen HYSYS and Aspen PlusWhen using Aspen HYSYS V8.4 and Aspen Plus V8.6 or higher, relief valve sizing and scenarios can be imported within

Aspen Flare System Analyzer V8.6 or higher, in order to assist in the designing and rating of a process’ flare system.

To successfully import relief valve sizing results, the Aspen HYSYS/Plus file must first be saved as either an “Aspen

HYSYS/Plus Compound File” (.hscz/.apwz) (prefered), or as an “Aspen HYSYS/Plus Simulation Cases” (.hsc/.bkp/.apw)

in the same folder as the relief valves Microsoft Database (.mdb) file. To do this, navigate to the “Save As” window from

the File menu in Aspen HYSYS/Plus, and then save the file as a compound file, as depicted in Figure 34. Alternatively, a

saved file message will also be displayed if the simulator is closed before saving.

Figure 34. Saving as a Simulation Case or a Compound File

Once the simulation file is saved in the proper format, open Aspen Flare System Analyzer. When the program is open,

navigate to the File menu, scroll over “Import Sources,” and then click the “Aspen Plus/HYSYS Relief Valve Sources…”

option, shown in Figure 35.


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Figure 35. Importing Aspen Plus/HYSYS Relief Valve Sizing Results

The import window for relief valves sized in Aspen HYSYS/Plus will be queued. Click the “Browse” button, and select the

simulation file in which relief valves were sized. Finally, click the “Upload File” button to bring in the information.

Figure 36. Uploading an Aspen HYSYS/Aspen Plus File for Import

When a simulation file has been uploaded, the window displays the device names for each PSV imported from Aspen

HYSYS/Aspen Plus. Rupture disk devices are ignored for these flare systems. Flare sources should then be specified for



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each valve being used in the flare network. Flare sources can either be selected from blocks present on the flare flowsheet,

or can be created by typing a name in the Flare Source column and hitting enter.

Aspen Flare System Analyzer V8.6 will automatically detect and map PSVs with similar names between the simulators

and the flare. After the mapping is done once, the other flare scenarios will remember the source mapping to simplify the

creation of extra scenario mappings. The user can also decide to rename the flare sources to match the Apen

HYSYS/Aspen Plus names, so that these names are automatically recognized by Aspen Flare System Analyzer for future

importing. The information imported from Aspen HYSYS/Aspen Plus can also be used for multiple flare cases using the

Flare Scenario view on the left. To create a new flare scenario, click the “<Add New>” option and enter a name. A single

import file is used to house all the mappings for multiple flare scenarios from one simulation case.

Figure 37. Entering Flare Sources and Multiple Flare Scenarios

Adding overpressure protection scenarios for each flare source can either be done manually, or through the Auto-Map

Scenarios feature. The Auto-Map Scenarios feature allows for quick search and selection of overpressure protection

scenarios that adhere to a certain criteria. For example, if a flare scenario was being designed to only handle fire relief

contingencies, the Auto-Map tool could be used to look up all fire contingencies imported.

First, after opening the Auto-Mapping form, choose the flare scenario for which overpressure cases are being selected.

Then, choose whether to search Aspen HYSYS or Aspen Plus valves and contingencies by overpressure scenario type or

name. Figure 38 shows a flare scenario being mapped for only fire protection cases.


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Figure 38. Auto-Mapping for Different Scenarios

It is recommended to save the imported set of valve sizes by clicking “Save Import Set” before continuing with subsequent

flare system design and rating. In Aspen Flare Analyzer V8.4 and higher, exiting this form will prompt you to save the file.

After importing and saving the relief valve sizing results from the simulators into Aspen Flare System Analyzer, click “OK”

to continue to flare system design.

Relief Valve Sizing and Dynamic Simulation The Safety Analysis Environment in Aspen HYSYS is compatible with dynamic simulation using Aspen HYSYS Dynamics.

This feature is useful when relieving conditions and fluid properties differ from those at steady-state operation, namely

when a relief scenario is triggered by a disturbance to steady-state operation. Dynamic simulation allows the user to

obtain precise fluid property measurements at a given point that can then be automatically referenced by the relief valve

sizing tool.

In Aspen Plus Dynamics, a relief valve unit operation can also be added, but this analysis is completely independent of the

Safety Analysis Envrionment in Aspen Plus steady-state. In Aspen Plus, the Pressure Relief module is also kept for

alternate Pressure Relief Device (PRD) analysis. This section describes the interaction of the Safety Analysis Environment

with the Aspen HYSYS dynamics mode.

To use Aspen HYSYS Dynamics and relief valve sizing together, a dynamic model must first be set up and run in Aspen

HYSYS Dynamics. For more information on completing this task, please refer to the Aspen HYSYS Dynamics Jump Start

Guide by going to: http://www.aspentech.com/Jump_Start-HYSYS_Dynamics_V8/.

When the dynamic simulation has reached the process conditions at which relief valve sizing is desired, simply stop the

dynamic simulation by selecting the “Stop” option under the Dynamics tab on the Aspen HYSYS ribbon, as shown below

in Figure 39. Strip charts are helpful in showing the progression of a dynamic simulation and can be used to determine

when to stop it.



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Figure 39. Stopping Dynamic Simulation

After dynamic simulation has stopped, proceed to the Safety Analysis Environment using one of the options displayed in

either Figure 1 or Figure 2. Then, the workflow for setting up and completing sizing for pressure relief valves that was

described in the previous sections of this guide, should be followed in order to size a PSV.

Aspen HYSYS Dynamics can also be used to rate relief valves after obtaining a valve size in the Safety Analysis

Environment. After adding a relief valve block to a simulation from the model palette, the set pressure and full open

pressure for the valve should be defined in the Design tab, followed by entering the sizing information under the Rating tab

for the valve, as shown in Figure 40.

Figure 40. Adding and Defining a Relief Valve for Dynamic Simulation

Once the valve is set up, a dynamic simulation can be run to see the valve’s performance when a process’s steady-state

operation is disturbed.


24


ConclusionsPressure relief valve design and sizing can be a tedious, lengthy process. Relief valve sizing in Aspen HYSYS and Aspen

Plus allows the user to design pressure relief valves quickly using a small amount of process information at the location of

the valve. Aspen HYSYS and Aspen Plus now encompasses all facets of the valve design process into one convenient

location. In addition, various scenarios involving multiple valves can be explored to find the most optimal relief schedule

for a unit.

Aspen Plus and Aspen HYSYS can also serve as an accuracy check to ensure that safety equipment has been properly

rated and will perform properly. It helps designers complete their work faster, so that safety equipment can be installed

and implemented sooner. All processes need to have safety precautions to avoid disaster, which is why these solutions

will continue to make all processes as safe as possible—with each use.

References1. American Petroleum Inst., “Sizing Selection, and Installation of Pressure-Relieving Devices in Refineries,” ANSI/API RP

520, 8th Ed., Part 1: Sizing and Selection, Washington D.C., Dec. 2008.

Additional ResourcesPublic Website:

http://www.aspentech.com/products/aspen-hysys.aspx

http://www.aspentech.com/products/aspen-plus.aspx

Online Training:

http://www.aspentech.com/products/aspen-online-training

AspenTech YouTube Channel:

http://www.youtube.com/user/aspentechnologyinc

http://www.youtube.com/user/aspentechnologyinc

http://www.aspentech.com/products/aspen-online-training

http://www.aspentech.com/products/aspen-plus.aspx

http://www.aspentech.com/products/aspen-hysys.aspx

Worldwide Headquarters

Aspen Technology, Inc.20 Crosby DriveBedford, MA 01730United States

phone: +1–781–221–6400fax: +1–781–221–[email protected]

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For a complete list of offices, please visit www.aspentech.com/locations

© 2014 Aspen Technology, Inc. AspenTech®, aspenONE®, the Aspen leaf logo, the aspenONE logo, and OPTIMIZE are trademarks of AspenTechnology, Inc. All rights reserved. 11-5538-0614

About AspenTech

AspenTech is a leading supplier of software that optimizes process manufacturing—for energy, chemicals,

engineering and construction, and other industries that manufacture and produce products from a

chemical process. With integrated aspenONE® solutions, process manufacturers can implement best

practices for optimizing their engineering, manufacturing, and supply chain operations. As a result,

AspenTech customers are better able to increase capacity, improve margins, reduce costs, and become

more energy efficient. To see how the world’s leading process manufacturers rely on AspenTech to

achieve their operational excellence goals, visit www.aspentech.com.

http://www.aspentech.com/locations

[email protected]

Documents

11-5538 JS ReliefSizing Refresh