Hysy 8.8-Overpressure D FINAL

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2015 Aspen Technology, Inc. AspenTech, aspenONE, the Aspen leaf logo, the aspenONE logo, and OPTIMIZE are trademarks of Aspen Technology, Inc. Al l rights reserved.11-7608-0615

Jump Start: Fire Overpressure Analysisin Aspen HYSYSand Aspen Plus

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

Anum Qassam, Product Management, Aspen Technology, Inc.

Katherine Hird, Product Marketing, Aspen Technology, Inc.


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2015 Aspen Technology, Inc. AspenTech, aspenONE, the Aspen leaf logo, the aspenONE logo, and OPTIMIZE are trademarks of Aspen Technology, Inc. All rights reserved.11-7627-0715

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Jump Start: Fire Overpressure Analysis in Aspen HYSYS and Aspen Plus

Table of Contents

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

Unwetted (API) Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Supercritical Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Wetted (API) Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

Semi-Dynamic Flash Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Additional Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25


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IntroductionAPI Standard 521 recommends that all pressure vessels under 25 feet in elevation be protected against overpressure

resulting from an external pool fire. A plant fire is a dangerous situation where flammable fluid gets trapped inside a

high pressure vessel with heat continually added to the system. For two-phase separators, the trapped liquid inventorys

composition, temperature, and pressure are constantly in flux. For a vessel with no liquid inventory, ideal gas expansion

can ease the difficulty of the calculation, but the complexity of the relief load calculation increases substantially at non-

ideal conditions. The Safety Analysis Environment within Aspen HYSYS and Aspen Plus offers a variety of calculation

methodologies to quickly calculate the orifice area required to protect a vessel against overpressure due to the fire

contingency.

This is not meant to be used as a stand-alone reference document. AspenTech recommends that a range of other

resources be referenced to give the new user a comprehensive view of how to use Aspen HYSYS and Aspen Plus. These

may include:

Jump Start: Pressure Safety Valve Sizing in Aspen HYSYS and Aspen Plus

Additional Resourcesavailable on the AspenTech Pressure Relief Sizing webpage

AspenTech support website

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

AspenTech business consultants

This document provides a detailed overview of the steps required to calculate the required relief load for the fire

overpressure contingency within the Safety Environment of Aspen Plus and Aspen HYSYS, with a detailed overview of

calculation assumptions and nuances for both the new and experienced safety engineers.

This document will assume the user is familiar with all the basic functionalities of the Safety Analysis Environmentincluding, but not limited to:

(1) Adding a relief device

(2) Designing and sizing a Pressure Safety Valve

(3) Multi-valve sizing

(4) Line sizing

(5) Reports

Please refer to the previously published Jump Start: Pressure Safety Valve Sizing in Aspen HYSYS and Aspen Plusfor

additional details on any of the aforementioned topics.

Either Aspen Plus or Aspen HYSYS can be used to follow this jump start guide. Following the jump start guide with the

example file PRESSURE RELIEF STARTER.hsc in Aspen HYSYS or the example file Safety Analysis without PRD.bkp

in Aspen Plus is strongly recommended. Both files are available on aspenONEExchange. This document was created

using the most recent version of Aspen HYSYS and Aspen Plus. Some of the user interface differs and more advanced

functionalities showcased in the screenshots provided of this jump start guide were not introduced in earlier versions.
http://www.aspentech.com/jump-start-guide/relief-sizing-aspen-plus-hysys/http://www.aspentech.com/products/engineering/pressure-relief-analysis/http://support.aspentech.com/http://www.aspentech.com/jump-start-guide/relief-sizing-aspen-plus-hysys/http://www.aspentech.com/jump-start-guide/relief-sizing-aspen-plus-hysys/http://support.aspentech.com/http://www.aspentech.com/products/engineering/pressure-relief-analysis/http://www.aspentech.com/jump-start-guide/relief-sizing-aspen-plus-hysys/


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Jump Start: Fire Overpressure Analysis in Aspen HYSYSand Aspen Plus

Initial SetupAll 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 when prompted. For consistency throughout this document,

screenshots were taken from the Aspen HYSYS V8.8, therefore please note that values from the Aspen Plus file may

not match the Aspen HYSYS screenshots, as they are different simulation cases.

To begin, the user should:

(1) Open the file PRESSURE RELIEF STARTER.hsc or Safety Analysis without PRD.bkp

(2) Enter the Safety Analysis environment

(3) Add a PSV to stream vapOut

(4) Open the PSV system tab by double clicking the PSV icon on the flowsheet

(5) Set the Design Temperature to Reference

(6) Set the Design Pressure to 35 psiG

Figure 1: Initial Setup of Flowsheet and PSV System Tab for Aspen HYSYS

For more detailed explanations on any of the aforementioned steps, please refer to the Jump Start: Pressure Safety Valve

Sizing in Aspen HYSYS and Aspen Plus.

TIP:Are you ready to enter the safety environment?

Before you enter the safety environment, you must confirm that the simulation flowsheet contains a stream that

best reflects the contents of the vessel (e.g. the feed stream to the protected unit operation). For help with the

Aspen Plus or Aspen HYSYS simulation environment, refer to the respective simulation manuals available at

http://support.aspentech.com.
http://www.aspentech.com/jump-start-guide/relief-sizing-aspen-plus-hysys/http://www.aspentech.com/jump-start-guide/relief-sizing-aspen-plus-hysys/http://www.aspentech.com/jump-start-guide/relief-sizing-aspen-plus-hysys/http://www.aspentech.com/jump-start-guide/relief-sizing-aspen-plus-hysys/http://www.aspentech.com/jump-start-guide/relief-sizing-aspen-plus-hysys/


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Unwetted (API) CalculationThis section describes how you can calculate the required relief load for a vessel with all-vapor in accordance with API 521

Section 5.15.2.2.2. The Unwetted (API) method is generally applicable for ideal-like systems with vapor compressibility

between 0.8 and 1.1.

Getting Started

Select the Scenarios tab and click the Create Scenario button.

Figure 2: Scenario Tab

Double click on the newly-created scenario to open up the Scenario Setup screen. You can also click on the scenario row

then click the Open Scenario button.

Figure 3: Scenario Setup

Next, select Fire from the Scenario Type dropdown menu.


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Figure 4: Scenario Selector

You can confirm the fluid properties by selecting the Fluid Properties tab. The property specifically of interest in the fire

calculation is the Operating Phase of the Reference Stream (vapOut @ Main).

Figure 5: Operating Phase on Fluid Properties Tab

Since the Reference stream is all-vapor at the operating conditions specified on the Equipment Tab, only the Unwetted

(API) and Supercritical Calculation Methods are available in the dropdown list on the Scenario Setup tab.


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Figure 6: Calculation Method Dropdown

You should confirm that the Unwetted (API) method is selected.

Calculation Parameters

The Max Wall Temp is the required input for the Unwetted (API) calculation, and it is defaulted to the API-recommended

593.3 C (1100 F) for carbon-steel. You can change this value for the specific equipment metallurgy.

Figure 7: Unwetted (API) Calculation Parameter

With version 8.8, you can select one of two methodologies to determine the relieving temperature for an unwetted vessel

by using the Relief Temperature Calculation Option.

Figure 8: Relief Temperature Calculation Option

Ideal Gas Assumption (API 521)

Per API 521 6e Section 4.4.13.2.4.3, the relieving temperature can be determined using Equation 11, which

assumes the Reference Stream fluid behaves like an ideal gas.

Ref Stream Equation of State

The relieving temperature can alternatively be calculated by flashing the Reference Stream fluid from normal

operating pressure to relieving pressure at constant density. This methodology will use the density of the

Reference Stream at the normal operating conditions specified on the Equipment Tab in the Safety Analysis

Environment.

Note that in version 8.8, the Relieving Temperature is calculated based on the radio button selected for the Relieving

Temperature Calculation Option. Figure 9 compares the Relieving Temperature calculated with the two options.


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Figure 9: Relieving Temperature Comparison for Unwetted Fire

To follow along with this document, select Ideal Gas Assumption (API 521) for the Relieving Temperature Calculation

Option.

Vessel Parameters

This section will detail how you can specify or calculate the exposed area value for up to three vessels in the same system.

Specify Exposed Area

If you have a value for the exposed area, you must select No for the Specify Equipment Dimensions? input. The

Exposed Area input box will turn blue, and you can type in the exposed area.

Figure 10: Unwetted (API) Specify Exposed Area

Calculate Exposed Area

If you would like to calculate the exposed area, you must select Yes for the Specify Equipment Dimensions? input.

You can then enter the Vessel Type, Head Type, Diameter, Vessel Tan/Tan, Elevation, Maximum Flame Height, and

Additional Area % in order to calculate the exposed fire area per API 521.


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Figure 11: Unwetted (API) Calculate Exposed Area

Number of Vessels Selection

You can also calculate the exposed area as the sum of up to three vessels. From the number of vessels dropdown,

select 3.

Figure 12: Number of Vessels Dropdown

You can enter any of the equipment specific parameters for three vessels. To follow along with this document, confirm

that the vessel parameters table from Aspen HYSYS matches Figure 13.


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Figure 13: Unwetted (API) Exposed Area Calculation for Three Vessels

Results

The Unwetted (API) calculation methodology determines the Required Relieving Flow based on Equation (12) in Section

4.4.13.2.4.3 of API 521 6th edition. Please note that, for consistency, all screenshots are taken from Aspen HYSYS by

following the Aspen HYSYS example file. Aspen Plus results may differ.

Figure 14: Unwetted (API) Required Relieving Flow


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Supercritical CalculationThis section of the document will detail the steps required to calculate the required relief load for a vessel that contains a

supercritical fluid at relieving conditions. Note that the methodology can also be applied to non-ideal vapor systems.

The implementation is based on the algorithm developed by Ryan Ouderkirk in the article Rigorously Size Relief Valves

for Supercritical Fluids, which uses the specific volume change of the fluid over time to determine the required relieving

flow at a series of time steps.

Getting Started

In order to use the supercritical calculation method, you must ensure that the Reference Stream Operating Phase is Vapor

(verify on Fluid Properties tab) and that the Number of Vessels is 1. Confirm that the Reference Stream is still vapOut.

Figure 15: Preconditions to Use Supercritical Calculation

Select Supercritical from the Calculation Method dropdown of the Scenario Setup tab.

Figure 16: Supercritical Calculation Method Selector


Next, you will specify the calculation-specific inputs for this methodology.

You can select whether adequate drainage or firefighting is present near the vessel. The selection will affect the constant

in the fire heat flux equation (from API 6e Section 4.4.13.2.4.2).

You can also specify the Gas Correction Factor, which will reduce the heat flux to the vessel. The Centers for Chemical

Process Safety in Guidelines for Pressure Relief and Effluent Handling Systems in Section 3.3.2.2 mentions that for

gas filled vessels, the heat input to the vessel can be modeled by using the heat flux equation for liquid filled vessels,

and multiplying the result by the gas correction factor of 0.3. Depending on the behavior of the supercritical fluid being

analyzed, you can adjust the heat flux equation by using the gas correction factor.
http://people.clarkson.edu/~wwilcox/Design/reliefv2.pdfhttp://people.clarkson.edu/~wwilcox/Design/reliefv2.pdfhttp://people.clarkson.edu/~wwilcox/Design/reliefv2.pdfhttp://people.clarkson.edu/~wwilcox/Design/reliefv2.pdf


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Confirm that the vessel dimensions match Figure 18 below.

Figure 18: Supercritical Vessel Parameters

Environmental F Factor

You can also calculate or specify the environmental factor F, which is used to account for any insulation that may be

protecting the vessel. You can calculate the environmental factor F based on the insulation conductivity and insulation

thickness on each vessel. An F factor of 1 means there is no insulation or heat input reduction. Traditional values for

insulation thickness and conductivity are available in the F1 help.

Specify F Factor

If you would like to specify the exposed area, select No for Calculate F Factor? input. The Environment Factor F input

will turn blue, and you can manually enter the value in the box.

Figure 19: Specify F Factor


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Calculate F Factor

If you would like to calculate the exposed area, select Yes for Calculate F Factor? input. The Insulation k and Insulation

Thickness values will turn blue. You can then enter the numbers as appropriate for the insulation on the vessel, and the

Environment Factor F will be calculated.

Figure 20: Calculate F Factor

Confirm that the insulation parameters match Figure 20 above for the Aspen HYSYS case.

Edit Flash Table

You can also view and edit the flash details by clicking the Edit Flash Table link.

Figure 21: Edit Flash Table


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You can then proceed to edit the number of Flashes and Max Iteration Temperature for better accuracy (with a longer

calculation time). As a rule of thumb, if increasing the number of Flashes or Max Iteration Temperature results in a

negligible change to the calculated orifice area, then there is no benefit to the additional number of flash steps.

Get acquainted with this methodology by adjusting the number of Flashes and Max Iteration Temperature and by viewing

the subsequent results. Before you continue, confirm that the Stepwise Flash Data dialog box matches Figure 22 below forthe Aspen HYSYS case.

Figure 22: Supercritical Flash Data

Results

The Required Relieving Flow is determined by the Mass Flow Rate that results in the greatest Required Orifice Area from

the iterative flash calculation (see Edit Flash Table dialog box).

Figure 23: Supercritical Required Relieving Flow


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The relieving temperature is based on the Temperature that corresponds to the greatest Required Orifice Area from the

iterative flash calculation (see Edit Flash Table dialog box).

Figure 24: Supercritical Relieving Temp

Note that the supercritical calculation methodology uses the Direct Integration (HEM) methodology to determine the

Calculated Orifice. Therefore, the user cannot select an alternative sizing method; the dropdown is deactivated.

Wetted (API) CalculationThis section of the document will detail the steps required to calculate the required relief load for a vessel that contains

liquid at relieving conditions.

The implementation is based on Section 4.4.13.2.4 from API 521 6e.

Getting Started

Confirm that the Scenario Setup tab for Scenario100 of 100 PSV 001 is open (see Figure 3). To select a 2-phase stream

for this example, check the Override checkbox to select an alternate stream for the scenario analysis.

Figure 25: Override Stream

The Select Reference Stream dialog box should open. Select stream FeedStream in Aspen HYSYS or FEEDIN stream in

Aspen Plus.


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Figure 26: Reference Stream Selector

You can confirm that the reference stream operating phase is two-phase by checking the fluid properties tab.

Figure 27: Verify Operating Phase (Wetted Vessel)


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The Calculation Method drop down for fire is based on the operating phase of the Reference Stream fluid. For a two-

phase Reference Stream, Wetted (API) and Semi-Dynamic Flash should be available in the drop down.

Please confirm that Fire is the selected Scenario Type, Vapor is the selected Orifice Sizing Method, and Wetted (API) is

the selected Calculation Method.

Figure 28: Wetted (API) Calculation Initial Setup


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This section details the selection of the calculation parameters specific to the Wetted (API) calculation methodology.


in the fire heat flux equation (see Section 4.4.13.2.4 from API 521 6e).

Figure 29: Wetted (API) Drainage Parameter

Next, you can enter the latent heat of vaporization, or use the simulation engine to estimate the latent heat of

vaporization. The Required Relieving Flow is indirectly proportional to the value of the latent heat of vaporization,

therefore use a reasonably conservative value in the calculation.

Specify the Latent Heat of Vaporization

To specify the latent heat of vaporization, select No for the Estimate Latent Heat? dropdown; the Latent Heat input

box will turn blue, and the user can enter the desired value.

Figure 30: Specify Latent Heat of Vaporization

Estimate the Latent Heat of Vaporization

To use the tool to estimate the latent heat of vaporization, select Yes for the Estimate Latent Heat? dropdown; the

Initial % Vaporized and Final % Vaporized input boxes will turn blue, and you can enter those values.

Confirm that the calculation parameters are specified according to Figure 31.

Figure 31: Estimate Latent Heat of Vaporization


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The latent heat of vaporization is based on the energy required to vaporize the Reference Stream from the Initial %

Vaporized to the Final % Vaporized. You can include or exclude the sensible heat absorbed by the liquid from the initial

% vaporized to the final % vaporized (mCp T) in this calculation methodology. Excluding the sensible heat will always be

more conservative.

Vessel Parameters

This section will detail how you can determine the Exposed Area and Environmental Factor for the Wetted (API)

calculation methodology.

Exposed Area

You can specify or calculate the exposed wetted surface area for up to 3 vessels by changing the Number of Vessel drop

down. You can either specify or calculate the exposed wetted surface area for each vessel.

Specify Exposed Area

To specify the exposed area for the vessel, you must select No for the Specify Equipment Dimensions? input. The

Exposed Area box will turn blue, and you can proceed to type in the exposed area.

Figure 32: Wetted (API) Specify Exposed Area

Calculate Exposed Area

To use the tool to calculate the exposed area, you must select Yes for the Specify Equipment Dimensions? input. You

can then specify the Vessel Type, Head Type, Diameter, Vessel Tan/Tan, Liquid Level, Elevation, Maximum Flame Height,

and Additional Area % in order to calculate the exposed fire area.


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Before you continue, confirm that the vessel parameters in Aspen HYSYS are specified according to Figure 33.

Figure 33: Wetted (API) Calculate Exposed Area

Environmental Factor





Specify F Factor

If you would like to specify the exposed area, select No for Calculate F Factor? input. The Environment Factor F input

will turn blue, and you can manually enter the value in the box.

Figure 34: Specify F Factor


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Calculate F Factor

If you would like to calculate the exposed area, select Yes for Calculate F Factor? input. The Insulation k and Insulation

Thickness values will turn blue. You can then enter the numbers as appropriate for the insulation on the vessel, and the

Environment Factor F will be calculated.

Figure 35: Calculate F Factor

Confirm that the insulation parameters match Figure 35 above for the Aspen HYSYS case.

Results

The Required Relieving Flow is calculated using the Wetted (API) calculation methodology.

Figure 36: Wetted (API) Required Relieving Flow

The Relieving Temperature is determined by a bubble-point flash of the Reference Stream liquid to the relieving pressure.

Figure 37: Wetted (API) Relieving Temperature


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Semi-Dynamic Flash CalculationThis section of the document will detail the steps required to calculate the required relief load for a vessel that contains

liquid at relieving conditions.

The Center for Chemical Process Safety in Guidelines for Pressure Relief and Effluent Handling Systems Section 3.3.2.1.4

recommends using a batch vaporization methodology to more accurately assess the Required Relieving Flow for a vessel

that contains liquid inventory. This is the methodology implemented in the Semi-Dynamic Flash calculation.

Getting Started

In order to use the Semi-Dynamic Flash calculation method, you must ensure that the Reference Stream Operating Phase

is liquid or two-phase (see the Getting Started section for the Wetted (API) Calculation for more details). Next, confirm

that the Number of Vessels is 1. Finally, confirm that FeedStream is the selected Reference Stream.

Figure 38: Semi-Dynamic Flash, Confirm Operating Phase

Select Semi-Dynamic Flash from the Calculation Method dropdown.

Figure 39: Semi-Dynamic Flash Calculation Method Drop-down



in the fire heat flux equation (see Section 4.4.13.2.4 from API 521 6e).

Figure 40: Semi-Dynamic Flash Drainage Drop-down


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Next, specify the vessel dimensions.

Vessel Parameters

For the Semi-Dynamic Flash Calculation Method, you must specify the Vessel Type, Head Type, Diameter, Vessel Tan/

Tan, Liquid Level, Elevation, Maximum Flame Height, and Additional Area % in order to calculate the exposed fire area.

Note that since the calculation method is based on a series of batch vaporizations of the liquid inventory, the liquid level

will change over the course of the flashes. If the Vary wetted area with time checkbox is checked, the simulator will

adjust the heat flux to the vessel at each time step based on the predicted liquid level for that time step. Confirm that the

vessel parameters are specified according to Figure 42 for the Aspen HYSYS case.

Figure 41: Semi-Dynamic Flash Vessel Inputs

Note that you need to provide the initial liquid level at the onset of the fire; the simulator will determine how the liquid

level will change from normal operating conditions to relieving conditions based on a constant density flash to relief

pressure.

Environmental Factor






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Specify F Factor

Select No for Calculate F Factor? input. The Environment Factor F input will turn blue, and you can enter the value in

the box.

Figure 42: Semi Dynamic Flash Specify F Factor

Calculate F Factor

Select Yes for Calculate F Factor? input. The Insulation k and Insulation Thickness values will become blue. You can

enter the numbers as appropriate for the insulation on the vessel, and the Environment Factor F will be calculated.

Figure 43: Semi Dynamic Flash Calculate F Factor

Edit Flash Table

You can also view and edit the flash details by clicking the Edit Flash Table link.

Figure 44: Edit Flash Table Link

If the liquid inventory vaporizes fully before the Max Iteration Temperature is reached, then we recommend that you

adjust the number of Flashes and Max Iteration Temperature for better convergence. Here again you must balance the

level of accuracy you are gaining with the performance sacrifice. You want to ensure that the calculated orifice area has

converged such that adjusting the number of Flashes and Max Iteration Temperature does not result in a significant

change to the calculated orifice area.


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Play around with this functionality by adjusting the number of Flashes and the Max Iteration Temperature. Before you

continue, confirm that the Stepwise Flash Data dialog box matches Figure 45 below.

Figure 45: Semi-Dynamic Flash Edit Flash Table

Results

The Required Relieving Flow is determined by the maximum Vapor Volumetric Flow generated during the step-wise batch

vaporization.

Figure 46: Semi-Dynamic Flash Required Relieving Flow

The relieving temperature is based on the temperature that resulted in the maximum generated Vapor Volumetric Flow.

Figure 47: Semi-Dynamic Flash Relieving Temperature


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ConclusionsAPI 521 recommends that all vessels under 25 ft. in elevation be protected for the fire overpressure scenario. Depending

on the protected system, varying levels of rigor may be required in determining the required relieving load. The Safety

Environment in Aspen HYSYS and Aspen Plus now provides rigorous determination of the required fire relief load. With

this tool, you can quickly and easily size relief devices for the fire overpressure scenario.

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.

2. American Petroleum Inst., Pressure-relieving and Depressuring Systems, ANSI/API Standard 521, Fifth Ed., Jan. 2007.

3. Center for Chemical Process Safety, Guidelines for Engineering Design for Process Safety, 2nd Ed., April 2012.

4. Ouderkirk, Ryan. Rigorously Size Relief Valves for Supercritical Fluids, in Chemical Engineering Process, August 2002.

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
http://www.aspentech.com/products/aspen-hysys.aspxhttp://www.aspentech.com/products/aspen-online-traininghttp://www.youtube.com/user/aspentechnologyinchttp://www.youtube.com/user/aspentechnologyinchttp://www.aspentech.com/products/aspen-online-traininghttp://www.aspentech.com/products/aspen-hysys.aspx


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Hysy 8.8-Overpressure D FINAL