11-3842 psv jump start

8/13/2019 11-3842 PSV Jump Start

1/20

2013 Aspen Technology, Inc. AspenTech, aspenONE, the Aspen leaf logo, the aspenONE logo, and OPTIMIZE are trademarks of Aspen Technology, Inc. All rights reserved.11-3842-0813

Jump Start: Pressure Safety Valve Sizingin Aspen HYSYS

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

Nicholas Brownrigg, Product Marketing, Aspen Technology, Inc.

Wilfried Mofor, Product Management, Aspen Technology, Inc.

8/13/2019 11-3842 PSV Jump Start

2/20


Jump Start: Pressure Safety Valve Sizing in Aspen HYSYS

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

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

Designing and Sizing a Pressure Safety Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Valve Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Scenario Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Sizing Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Multiple Valve Sizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

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

Documentation Builder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Additional Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8/13/2019 11-3842 PSV Jump Start

3/20



1

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 occurs frequently 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 vastly 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 V8.3 has a pressure safety valve sizing feature, which uses data from a process

simulation to help automate PSV calculations.

Aspen HYSYS uses common valve design standards, most notably API 520, 521, to determine pressure relief valve sizing

information and values. 25 common overpressure scenarios are included in the program and can be analyzed and sized for.

Aspen HYSYS 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 Aspen HYSYS 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 normally requiring manual incorporation.

This Jump Start guide will walk the reader through the process of using pressure relief valve features in Aspen HYSYS

towards designing 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. These may include:

AspenTech support website (support.aspentech.com) contains 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 V8.3. It assumes that the user has Aspen

HYSYS V8.3 or higher installed on her or his computer and a functional process design completed.

8/13/2019 11-3842 PSV Jump Start

4/20


2


Adding a Pressure Relieving Device to a HYSYS SimulationIn order to add a pressure safety valve to a HYSYS 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 and converging the simulation, click on Pressure Relief in the Home ribbon of

the HYSYS Simulation environment to enter the Safety Analysis environment. Alternatively, the Safety Analysis button,

located on the bottom left of the Aspen HYSYS program, can be used. Both options are shown below in Figures 1 and 2.

Figure 1. Pressure Relief Button on Home Tab

Figure 2. Safety Analysis Option in Aspen HYSYS

After opening the Safety Analysis viewing window, select the Unit Operations option in the navigation pane on the left 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 option, in which floating/dangling

streams with no connections to process models are located (Figure 3).

Figure 3. Location of Unit Operations and Unattached Streams Menus in Safety Analysis Panel

To add a PSV to a simulation, click the Add PSV option on the ribbon in the Safety Analysis environment. This switches

the cursor into attach mode. Move the mouse to hover over the arrow of a stream on which a PSV is necessary. A blue

box appears as the target for unit operation exit streams. Click on the blue box to attach a relief valve to that location.

8/13/2019 11-3842 PSV Jump Start

5/20



3

Figure 4. Add PSV Option in Safety Analysis Environment

A PSV can also be added using the navigation pane. Open the Unit Operations or Unattached Streams node and right

click the desired block or stream. Scroll to highlight the Create PSV option. When prompted, select which stream the

valve should be located on. An example of this PSV addition method is shown in Figure 5.

Figure 5. Adding a Pressure Safety Valve and Selecting the Appropriate Stream

A PSV will be placed on the flowsheet in the Safety Analysis environment after following one of the methods described

above. Figure 6 shows an example flowsheet with a PSV attached to a stream connected to a process unit, while Figure 7

shows a PSV attached to a single stream unaffiliated with any unit operations.

8/13/2019 11-3842 PSV Jump Start

6/20


4


Figure 6. Process Stream with PSV

Figure 7. Unattached Stream with PSV

Designing and Sizing a Pressure Safety ValveAdding a pressure safety valve to a unit operation in a simulation allows the user to open tabs in which the pressure safety

valve can be designed and sized to meet relief specifications and requirements.

Valve Design

Double-clicking on a pressure safety valve on the flowsheet opens the Valve Design tab, shown in Figure 8. In this tab,general valve design details are input.

8/13/2019 11-3842 PSV Jump Start

7/20



5

Figure 8. Valve Design Tab

First, choose the appropriate options from the dropdown menus to define the valve material of construction, valve type,

and valve discharge. Next, the valve design temperature and the set pressure at which the valve opens should be specified.

After doing so, set a value for the superimposed backpressure present in the valve, according to design calculations.

If the valve will have a rupture disk, ensure that the Rupture Disk Factor entry has a value of 0.9. If there will be no rupture

disk, this value should be 1.

Click the Create Scenario button above the scenario list table to evaluate multiple relief scenarios for which a relief valve

is necessary and obtain PSV sizing for each scenario. The Create Scenario button and a populated scenario list table are

shown in Figure 9.

Figure 9. Creating a Scenario in the Valve Design Tab

8/13/2019 11-3842 PSV Jump Start

8/20


6


After clicking the Create Scenario option, a new pressure relief scenario is created in the scenario list table. To open the

Scenario Setup tab and obtain a relief load and PSV size, simply click the emergency scenario name on the scenario list

table.

Another method of opening the Scenario Setup tab is to return to the Unit Operations tree in the navigation pane (Figure

10). Click the PSV option under its corresponding unit block to open the scenario listing. Then, choose the applicablescenario to open the Scenario Setup tab.

Figure 10. Opening Scenario Setup Tab from Unit Operations Tree

Scenario Setup

After clicking on a scenario or choosing a scenario from the navigation pane, the Scenario Setup tab, shown in Figure 11,

appears.

Figure 11. Scenario Setup Tab

8/13/2019 11-3842 PSV Jump Start

9/20



7

Included in Aspen HYSYS are four different design codes. The four codes are API 520 & 521, ASME VIII, PD 5500, and EN

13445. Select the pertinent design code from the dropdown menu before continuing.

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

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

12.

Figure 12. Relieving Pressure Calculation Window

In the Relieving Pressure Calculation window, input the allowable overpressure percentage, which determines the amount

of pressure that can build up beyond the set pressure before the valve opens. After finishing, verify that the relieving

pressure is correct, and select OK to continue.

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

window displayed in Figure 13. Set the parameters describing the backpressure and click OK to continue.

Figure 13. Backpressure Calculation Window

8/13/2019 11-3842 PSV Jump Start

10/20


8


Enter the valve discharge coefficient if the value differs from the default value of 0.9750. Then, choose the failure scenario

type under the Relief Load grouping. To obtain a relieving flow load, a manually calculated value can be entered or the

reference flow value from the HYSYS process stream that the PSV is attached to can be used. Additionally, if a relief

scenario that is highlighted in blue on the scenario list (Fire, Control Valve Failure, Exchanger Tube Rupture, Fan Failure, or

Reflux Failure) is chosen, the relief load can be calculated in Aspen HYSYS by selecting the Calculated radio button and

by providing more parameters surrounding the scenario where prompted. Figure 14 shows the scenarios available in the

Scenario Type list, while Figure 15 shows a sample relieving load calculation for a Fire relief scenario..

Figure 14. Relief Load Scenarios Available

Figure 15. Sample Calculation of Relieving Flow for Fire Relief Scenario

8/13/2019 11-3842 PSV Jump Start

11/20

8/13/2019 11-3842 PSV Jump Start

12/20


10


Figure 17. 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 theScenario Name input box. Then, return to the Valve Design tab to proceed to line sizing for the relief valve.

Multiple Valve Sizing

If the computed relief load is too large to be relieved using just one pressure safety valve, it is necessary to pass the

relieving flow through multiple pressure valves. Successful sizing of multiple valves for a stream in Aspen HYSYS requires

returning to the Simulation environment and using a tee splitter block to divide the relief load stream into multiple streams

equal to the number of relief valves necessary. Figure 18 shows an example flowsheet with a tee splitter for the Vap

Outlet stream in the process split into two separate relief load streams.

Figure 18. Tee Block to Size Multiple Valves for Vap Outlet Stream

Double-click the stream entering the tee block, and define its conditions, properties, and composition by selecting the

Define from Other Stream button that appears in the material stream window (Figure 19), and then select the

appropriate stream to be relieved by multiple valves.

8/13/2019 11-3842 PSV Jump Start

13/20



11

Figure 19. Define from Other Stream Option in Relief Load Material Stream Window

Return to the flowsheet, double-click the tee block, go to the parameters section, and input the appropriate flow ratio for

each stream exiting the splitter to define how the flow of the relief load will be split amongst the valves (Figure 20).

Figure 20. Defining the Flow Ratio for the Relief Load Splitter

After setting up the tee block to split the relief load flow, return to the Safety Analysis environment. Add a PSV to each

stream exiting the tee block, such that the streams exiting the tee block look similar to the ones shown in the flowsheet in

Figure 21.

8/13/2019 11-3842 PSV Jump Start

14/20


12


Figure 21. Safety Analysis Environment Flowsheet with PSVs Attached

Proceed to size the safety valves as previously described in this guide, except use a 16% allowable overpressure when

determining the relieving pressure for the valve with the highest flow rate and an 11% allowable overpressure for allsubsequent valves with lesser flowrates.

Line SizingReturn to the Valve Design tab after creating and sizing all scenarios requiring a pressure relief valve. 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 22, to choose which failure scenario the valve will be sized for.

Figure 22. 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 23, to begin

line sizing for the pressure safety valve.

Figure 23. 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,

Aspen HYSYS 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.

8/13/2019 11-3842 PSV Jump Start

15/20

8/13/2019 11-3842 PSV Jump Start

16/20


14


Figure 26. Example Built-in HYSYS PSV Calculation Report

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 builders home screen, shown below

in Figure 27, a list of relief devices sized in Aspen HYSYS 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 27. Microsoft Access Documentation Builder Selection Screen

8/13/2019 11-3842 PSV Jump Start

17/20



15

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 Aspen HYSYS. These are denoted in grey. The spaces in white require user input to be completed. A sample

edit page for a mechanical data sheet is shown in Figure 28.

Figure 28. 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 29 shows a completed sample mechanical data

sheet, given the input information from the edit page shown in Figure 28.

8/13/2019 11-3842 PSV Jump Start

18/20


16


Figure 29. Completed Example Mechanical Data Sheet

Completing documentation using the documentation builder in Aspen HYSYS reduces the time needed to complete safety

valve paperwork to submit to regulatory agencies and valve vendors.

8/13/2019 11-3842 PSV Jump Start

19/20



17

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

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

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

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

implemented sooner. All processes need to have proper safety precautions to avoid disaster and Aspen HYSYS continues

to help 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 Resources

Public Website:

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

Online Training:

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

AspenTech YouTube Channel:

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

8/13/2019 11-3842 PSV Jump Start

20/20

Worldwide Headquarters

Aspen Technology, Inc.

200 Wheeler Road

Burlington, MA 01803

United States

phone: +17812216400

fax: +17812216410

[email protected]

Regional Headquarters

Houston, TX | USA

phone: +12815841000

So Paulo | Brazil

phone: +551134436261

Reading | United Kingdom

phone: +44(0)1189226400

Singapore | Republic of Singapore

phone: +6563953900

Manama | Bahrain

phone: +97317503000

For a complete list of offices, please vis 2013 Aspen Technology Inc AspenTech aspenONE the Aspen leaf logo the aspenONE logo and OPTIMIZE are trademarks of Aspen

About AspenTech

AspenTech is a leading supplier of software that optimizes process manufacturingfor 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 worlds leading process manufacturers rely on AspenTech to

achieve their operational excellence goals, visit www.aspentech.com.
http://localhost/var/www/apps/conversion/tmp/scratch_7/[email protected]://localhost/var/www/apps/conversion/tmp/scratch_7/[email protected]

11-3842 psv jump start

Documents