Size Pressure Safety Valves and Design Flare Systems using Aspen HYSYS and Aspen Flare System Analyzer Webinar Q&A This document summarizes the responses to questions posed before and during the webinar. Q: Is Aspen Flare System Analyzer the same as Flarenet? A: Yes, Flarenet was a former name used for Aspen Flare System Analyzer. Q: Do you have to use Aspen HYSYS V8.3 to be able to use the pressure relief valve sizing capability? A: Yes, relief valve sizing is available only in Aspen HYSYS V8.3 or higher. In addition, V8.4 contains the mapping of Aspen HYSYS PSVs and scenarios to Aspen Flare System Analyzer. Q: In what version is the linkage between Aspen HYSYS and Aspen Flare System Analyzer available? A: The linkage between these two products is only available in V8.4 or higher. _ Q: Will relief valve sizing capabilities be available in Aspen Plus in the near future? A: This is a project we are actively working on. _ Q: Is the calculation of latent heats going to be available at some point? A: This is a concern that we are addressing. _ Q: Are there similar tools available in aspenone? A: Here at AspenTech, we continue to build upon the aspenone web and mobile interface, and are looking at future additions. Please contact Wilfried Mofor, Product Manager for PSV sizing in Aspen HYSYS, if you would like your input to be heard on how to best integrate this feature into aspenone web and mobile. Q: How is the design temperature for a fire case decided? A: A design temperature can either be referenced from the stream that a PSV is attached to, or manually entered by the user. Q: Can the in/out flange sizes or orifice sizes be directly entered? A: Orifice sizes and names can be customized, but in/out flange sizes cannot.
Q: Is there any way to evaluate an existing PSV for a given relief scenario? A: Yes, it would involve setting up a simulation in Aspen HYSYS to model the stream that the PSV is attached to, and then evaluating according to the relief valve sizing in the Aspen HYSYS workflow. Q: Please differentiate the flow for pressure drop calculation. Is it the relief load or the rated capacity? A: Aspen HYSYS uses the rated flow for most cases, but allows the user to use the relief load for certain contingencies, so it is up to the user. Aspen HYSYS automatically uses the relief load for certain cases. Please see the F1 help in the product for more information. Q: Is the flow transferred to Aspen Flare System Analyzer required? Is the flow used in Aspen HYSYS relief valve sizing the rated capacity? A: Aspen Flare System Analyzer gets the required flow rate and composition from Aspen HYSYS and then re-calculates the rated flow. Q: Would any changes made to the Aspen HYSYS case be propagated to Aspen Flare System Analyzer automatically or do we need to re-map the system? A: The system will have to be re-imported. Q: Is it possible to use the new PSV sizing tool with a dynamic simulation? A: Yes, PSV sizing in Aspen HYSYS can be used with Aspen HYSYS Dynamics. There was a webinar conducted in October on this topic, as well as a section in the Jump Start Guide. Download the Jump Start Guide or replay the PSV and Dynamics Webinar. Q: Can Aspen HYSYS cope with sizing of PSVs when the contained fluid is supercritical? A: Yes, Aspen HYSYS can handle PSV sizing for supercritical fluid by using the Direct Integration Method as described in API 520 8e. Q: Does the fire case account for liquid holdup? A: No, this is the API 521 fire calculation method which assumes a steady-state vaporization of the liquid content to create the vapor relief load. Q: Does depressuring use the same utility as before? A: Yes, you can still use the depressuring utility used in Aspen HYSYS. Q: There is a sonic velocity criteria for PSV outlet line sizing. Is there a momentum (ρv 2 ) criteria? A: No, but the value is listed on the line sizing results table for reference. Q: Can the relief valve documentation be saved in a format external to Aspen HYSYS so that it can be sent to other people? A: Yes, documentation can be exported to a PDF, Microsoft Excel sheet, or Word document and can then be passed to other people.
Q: Does the 3% rule on inlet piping pressure drop apply only to irreversible losses as defined in API? A: Yes, that is correct. Q: What happens when you choose vapor sizing and the stream from Aspen HYSYS is liquid? Does the software estimate the heat? A: If the vapor sizing method is chosen and the Aspen HYSYS stream is liquid, a warning message is displayed indicating this. Since the method is inconsistent with the fluid, the orifice size is not calculated either. Q: Does Aspen Flare System Analyzer use the required flowrate or the rated capacity of the valve? A: You have the option in Aspen Flare System Analyzer to use either one by checking the rated flow for tail-pipes option. Q: Can this tool be used for sizing three-way relief valves? A: Multiple valves can be sized for a stream using a splitter, as described in the Jump Start Guide. At this time, however, line sizing for multiple valves is unavailable. Q: In sizing valves for tube rupture, is there a way to calculate how much is going to the valve and how much is going to the process pipe? A: No, not at this time. Q: What is the basis for latent heat? Is it based on 1%, 5%, or can we adjust? A: The latent heat is a user input in this calculation. Various analyses can be performed to compute this value. _ Q: Does Aspen Flare System Analyzer estimate height and diameter of stack in order to avoid radiation problems? A: No, it does not. _ Q: Is Aspen HYSYS PSV capable of conducting dynamic simulation for column systems? A: Aspen HYSYS is the host simulator for the relief valve sizing and it is capable of performing dynamic simulations for most equipment in the process industry, including towers/columns. Q: Does Aspen Flare System Analyzer come with V8.4 or is it additional? A: When a user purchases the aspenone Engineering suite of products, both Aspen HYSYS and Aspen Flare System Analyzer are included, since they are bundled in the Engineering Suite. Q: Are the orifice sizes in Aspen HYSYS according to API 526 only? A: Yes, the default selectable orifice sizes are from API 526, but the list is customizable and users can add in information as needed to the selectable orifice list.
Q: Can Aspen HYSYS handle a system that enters as a vapor and flashes to a two-phase system as it passes through the relief valve? A: Yes, mixed-phase calculations, including the Omega method and the HEM Direct Integration method, are available in Aspen HYSYS. Q: In some projects we have, different simulations may be a controlling case. Can we recall different simulations to flare net system, simultaneously? A: Yes, Aspen Flare System Analyzer can pick up information from multiple simulation cases, simultaneously. _ Q: Will ideal, semi-ideal, or real Cp/Cv values be used for sizing PSVs? A: The ideal Cp/Cv value is used (Cp/(Cp-R)). Q: Is it possible to design PSV for a batch reactor or storage tank? A: Yes, you can for a batch reactor, but for storage tanks, it s as per API 2000 in this version. Q: Does AspenTech use the enthalpy balance method for PSV sizing on columns? A: The column is not simulated by Aspen HYSYS. The user will have to perform the simulation and include the results in PSV to size the relief valves for various simulated scenarios. Q: Can we use PSV plus without connecting to the simulation? A: PSVs can be sized for unattached streams that have defined fluid properties. Unattached streams do not have to be included in a completed simulation. Q: Can we design PSVs for atmospherin LNG tanks? A: No, you cannot. Q: What method is used by Aspen HYSYS to size PSVs? A: API 520 and 521 standards are programmed into Aspen HYSYS for valve and scenario sizing, while orifice sizes are based on API 526. Q: Can Aspen Flare System Analyzer allow the flowrate in the PSV tailpiece equal the rated capacity of the PSV and the main flare line given the required rate relief load? A: Yes, in Aspen Flare System Analyzer you can set the tailpipes to be sized using the rated capacity and all other piping is sized using the relief load (required flow).
Q: When you choose vapor sizing and the stream from Aspen HYSYS is liquid, which heat of vaporization does Aspen HYSYS use if the stream is a mixture? Can we get the value of heat required? A: Aspen HYSYS will not perform that analysis for PSV sizing since there are many ways of performing that analysis. The user is supposed to perform the analysis and pass the information to the relief valve for sizing. Q: Can Aspen HYSYS V8.3 size flare tips? A: No, it cannot.