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

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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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    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.11-7627-0715

    Jump Start: Fire Overpressure Analysis in Aspen HYSYSand Aspen Plus

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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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    Jump Start: Fire Overpressure Analysis in Asp