The latest versions of RISKCURVES

Dispersion scenarios: In EFFECTS, by default the “wind speed reference height” is 10m which describes the height at which the provided wind speed is measured. This is because meteorological data is by default provided at this measurement height.

When performing validation work and comparing simulations against experimental data, the wind speed may need to be defined at a different reference height. That is the reason why an additional (expert) input has been incorporated in the dispersion model. This input parameter was available within the algorithm internally but wasn’t enabled in EFFECTS’ commercial version. This new parameter now allows the specification of wind speed at a different measurement height than the default of 10 m. Nevertheless, we strongly advise users to apply the default 10 m reference height for calculations, referring to standard meteorological data.

Dispersion scenarios: During the verification procedure of the EFFECTS v12 Dispersion model, an inconsistency in the used wind velocity profiles was discovered. The issue was that the same wind profile could not be reproduced when entering corresponding wind velocities at different heights. A modification of the given Pasquil stability class (or Monin Obukhov length) based on the reference input (wind speed and reference height of the wind speed) might have led to slightly different wind velocity profiles and dispersion behaviour. This inconsistent behaviour has been fixed, potentially leading to a different wind velocity vs height behaviour compared to the previous version. Calculated concentrations may be different for this software release, in particular for stable atmospheric classes. Small differences have been observed for Pasquill stability classes A-C, neglectable difference has been observed for Pasquill stability class D, and noticeable differences have been observed for Pasquill stability classes E-F. The modifications in this software release result into a better agreement with experimental data ranging from heavy gas releases to passive dispersion.

Dispersion scenarios: The parameters offset X direction and offset Y direction have been abandoned, because potential offset due to the jet region is already included in the results. The existing offset of 1 m in x direction, which was used for vertical jets, has been removed.

Dispersion scenarios: jet release mode: If the concentration of interest (LFL for flammable, LC1% for toxics) did not reach outside the jet expansion region, this contour might be hidden, while its flammable mass and toxicity footprints were correctly reported. This behaviour has been corrected. Furthermore, contours which reflect "reporting height Zd" will no longer be extended with the jet contour if Zd is not at the centre of the jet.

Neutral gas dispersion scenarios: jet release mode The side view contour presented by the neutral dispersion model could be influenced by preceding jet expansion phase, leading to an inconsistent initial offset. This behaviour has been fixed.

Neutral gas dispersion Toxic Dose: The model now allows to plot contours for user defined dosage levels below 10-12 s*(kg/m3)^n, which were previously skipped as being irrelevant.

Combined LOC release in 10 min (G2) scenarios: These scenarios have been converted to "LOC Continuous Leak" (for all phases), which now includes a "Type of vessel outflow" choice "Vessel empty in specified time" that replaces the former 10 minutes (G2) scenarios. When loading a Combined LOC G2 scenario (the previous version 10 minutes scenario), these will automatically be translated into a "Continuous Leak" type scenario. We abandoned the (G1) and (G3) name additions in the combined models and simply refer to "LOC Instantaneous release", representing the catastrophic failure of a vessel, and the "LOC Continuous Leak" for any big or small leak-rate situation.

Overpressure damage calculation: The translation from overpressure towards lethality has been improved, avoiding some initial lethality levels between 0 and 1 m distance if the associated threshold pressure was never reached.

User interface: Potential error messages when using unrealistic ambient pressure or ambient temperature values are avoided.

User interface: A potential access violation error when exporting a graph with an empty dataset has been caught.

User interface: The ordering of input parameters has been made more consistent in all (combined) models.

User interface: The help desk contact option, previously only accessible in the Help..about box, has also been added to the main menu under "Help".

User interface: Several minor issues in the footprint import wizard were solved.

User interface: The reported area of a population polygon was reported in the wrong units, without conversion to m2 reflecting the projection system. Although this wrong unit did not influence societal risk results, this report value issue has been corrected.

User interface

Project tree: An issue has been resolved that could freeze the application upon pasting invalid data.

Installer

Fixed signature mismatch in a third-party dll.

University edition version

A project loading issue has been solved.

User interface

• Chemical editor: The icon for a "user-defined" chemical has been adapted, creating a more clear difference between official DIPPR data and modified user substances.
  
• Measurement ruler: The behaviour of the measurement tool is now more intuitive. It now immediately shows the distance between the first selected coordinate and the (moving) cursor and does not wait until a second point is selected.
• Map view: The positioning of the North Arrow and the Scale bar relative to the map has been improved. Furthermore, the responsiveness in refreshing a tile server and showing the equipment locations has been improved. If the background map fails to load, a more adequate error message will be shown. A surrounding contour (dotted surrounding circle) can now also be shown if the map does not have the equipment location.
• Graph view: A scaling issue when changing axis units in a comparison set has been solved; all selected graphs will now react to selected axis units. When using the graph expert editor, removing series no longer creates an error, although we strongly advise to un-tick a line in the legend to hide a specific graph.

Dispersion scenarios

• A potential fluctuation in the graph "max. concentration vs distance at Zd", rarely occurring at very short distances, has been solved.
• The trajectory calculation of vertical jets has been improved. This may influence calculated concentrations for this typical release situation, especially at short distances where vertical jet plume rise influence is expected.
• When using a (horizontal or vertical) jet release calculation, the dispersion model performs a phase detection check to either ask for "expanded diameter" and "liquid fraction" for 2 phase releases, or "hole dimensions" and "exit pressure" for gases. In case of gases, these inputs would trigger the integrated turbulent jet calculation. This phase detection mechanism has been improved, now using pressure + temperature to distinguish the substances phase. Additionally, when using chemical mixtures, the model is now less restrictive and accepts potential multiphase mixtures.
  

Toxic dispersion scenarios

The concentration time behaviour for semi-continuous releases has been improved. This change tends to lead to larger lethality fractions at shorter distances, because the rapid concentration decay after end of release is now more smooth.

Vulnerable area calculation

A potential underestimating of toxic victims in a vulnerable area, occurring for small area's (compared to the toxic grid cell size) has been fixed.

Combined LoC model liquefied gas G2 G3 scenarios

• When combining a jet release source rate (airborne fraction) with a pool evaporation rate (rain-out fraction), the model will now select either "horizontal jet", "vertical jet" or "pool evaporation" for the dispersion, based on selected outflow angle and most dominating source rate.
• Internal spray release calculation: The spray release model has been improved to be able to deal with situations where all liquid droplets flash out, which could previously lead to misleading answers in top venting situations. Moreover, the model now correctly applies a contraction coefficient, which should be included to obtain effective outflow area. This modification may lead to slightly altered calculated liquid fractions in the aerosol but does not influence rain-out behaviour.

Combine liquid scenarios

When switching from land to water in the evaporation model or vice versa, the subsurface roughness types will now be adapted accordingly. This avoids misusing associated minimum pool thickness heights, which are specific for land or water.

Footprint scenario importer

The footprint scenario importer has now been extended to support transport equipment. This implies that a list of route points can now also be imported from a spreadsheet (as specific projection system coordinates or as Lat/Long angles). Furthermore, the export to a spreadsheet can now be applied on equipment or scenario sub-levels. If an imported toxic consequence footprint cannot find the associated listed chemical (or multiple matches are possible), the user can now interfere and select the intended chemical.

Licensing

The software now supports cloud licensing, offering the flexibility of a network license without the need for setting up a company license server. For more information, contact
riskcurves@gexcon.com.

Installation

The installation of the driver for the license system is now optional.

User interface

• We have redesigned the user interface, not only changing the main icon, but also adapting button images and several interface elements, creating a more fresh and clear user experience. The main screen layout and position of interface elements has hardly changed, so the way of working with the software remains identical. Several specific GUI elements have been improved, such as menu structure, the side bar panel and map legend panel, which can now be unpinned, allowing more space for the map. The new user interface fully supports high resolution displays and scaling options.
• The assignment of "normal" and "expert" parameters has been adapted. Most parameters will now already be shown in "normal" mode, while only a few parameters can be considered to be real "expert" parameters, which rarely need to be adjusted. Simple mode remains the same, showing a limited list of inputs, while "expert mode" will now only be required in dedicated situations.
• Grid smoothing: The grid smoothing, which uses an interpolation method to show grid based results on the map, is no longer activated for population grids and societal risk map grids because this would make these "population cell" based results more difficult to understand.
• Risk contour colours: An issue with a the colour scale for risk contours, resulting from a non-expected order in risk levels in presentation settings, was solved.

Risk calculations

• Meteorological definition: The editor will no longer accept wind speeds lower than 0.5 m/s, avoiding errors when trying to calculate with unrealistic low wind-speeds.
• Footprint scenario spreadsheet importer: We have included a possibility to import "Footprint definition" scenario's from a spreadsheet. These type of scenario's are highly useful, because they allow the use of consequence results from potential third party tools, while avoiding the time consuming consequence calculation. Unfortunately they were also difficult to use, because they required extensive user input: every weather condition needs its own table with footprint dimensions. This new footprint importer allows to prepare a full list of pre-calculated consequence results in an Excel spreadsheet, and import them all at once as footprint scenario's, including assignment to specific equipment locations. An import wizard will guide users through the import process.
• Footprint scenario spreadsheet export: Existing footprint scenario's can also be exported to a spreadsheet, providing convenient template table's which can be edited in Excel and imported back with modifications and additions.
• Imported calculations: When combining results using the project importer, the analysis point results (risk ranking at a specific coordinate) will now also be imported and potentially combined in the report. An obvious requirement is that the imported projects use identical analysis point coordinates, but this feature allows a complete evaluation of risk ranking results when combined projects using imported calculations.
• Calculation reports: an issue with the reporting of pool fire scenario distances was solved. This issue did not affect any risk results but showed misleading "max. scenario distances" IF direct flame contact was dominating. The reported maximum distance to lethality level was using the pool diameter as 100%(direct flame contact) lethality level. This distance is now corrected to "distance to the contour of the flame area (top view)", so actually using projected flame surface, similar to applied for the jet fire consequence distances.
• ·Event probabilities: The default BLEVE fraction for combined LoC models is now 1, implying that the direct ignition (of an instantaneous two phase flammable release scenario) will always lead to a BLEVE fireball (and potential overpressure). The previous lower fraction was based on old guidelines, but is now considered non-conservative. The BLEVE fraction can still be changed to comply with local regulatory guidelines, but it is advised to apply a value of 1.
• Consequence risk: Version 11 had an issue with a flammable cloud consequence risk, IF the flammable cloud was limited within the turbulent jet expansion zone. This consequence risk calculation now always includes the jet zone, which is now an integral part of the LFL contour.
• Footprint scenarios: The explosion footprint definition will now allow to enter an offset for the overpressure effects, which implies the explosion overpressure circle centre does not have to be in the middle of the LFL cloud. This option might be used to prescribe a specific ignition location relative to the LFL cloud, but will currently be used in all directions.
• Footprint scenarios: Although the "Local Cloudfire" footprint is no longer available and was replaced by a "BLEVE or Gas Fireball" footprint scenario in version 11.4, older project files might still contain these type of scenario's. These old "Local Cloudfire" footprint scenarios are now correctly included within the risk calculation.

Dispersion modelling

• The emphasis of this important major release is on dispersion modelling. The improved dispersion model supports and correctly predicts the rising behaviour of "lighter than air" releases from grounded over transitional to fully lifted-off. Obviously, this was done to comply with the growing demand to predict hydrogen releases. However, these modifications also affect substances like ammonia (which is lighter than air as pure ambient temperature dry gas) and methane, because the prediction of potential rising gasses has changed considerably. The full potential transition from heavy to neutral to lighter than air (triggered by heat exchange) is now modelled adequately by ONE model.
• The use of hydrogen also introduces much higher storage pressures, for which the influence of the turbulent mixing (high speed jets) is of great importance. To deal with this impulse driven dilution phase, the turbulent jet model is now an integral part of the dispersion models. The turbulent jet model itself has also undergone major improvements resulting in more accurate results in the full velocity range from sub-to supersonic flow. For highly under-expanded jets, the results are less conservative compared with version 11.
• The flammable cloud and concentration dispersion model now shows "surrounding" contours which follow the cloud centreline height, and additionally present contours at specified reporting height Zd. The "Dynamic concentration" cloud presentation will always represent concentrations at this reporting height. Additionally, the calculation of flammable cloud contents (mass, area and volume) had to be adapted, now following the potential rising cloud centreline height.
• Because the new dispersion model model also features the previous heavy gas model and has been extended for "non heavy" (including lighter than air) behaviour, we no longer require a choice between "heavy" an "neutral gas" dispersion. The "neutral gas dispersion" model is still available for dedicated real passive situations, but the advice is to use the new generic "dispersion model" for standard situations. Therefore, this model has is now called "Dispersion model" and replaces the "Heavy gas dispersion model".
• The modelling of vertical jets has been improved and made more consistent. In the past, a special treatment of the release terms with source term densities close to the one of ambient air was applied. In this case, a representative jet source term was located at a specific height starting in horizontal direction. In the new dispersion model this behaviour is removed and all release term densities from heavy over neutral to light are treated by one consistent model. In addition, the dispersion model for vertical jets is modified and shows improved results for light and heavy gas releases compared with experimental data.

Combined LoC scenarios

• Because the improved dispersion model is the preferred and most realistic model, the combined LoC models no longer runs the neutral gas dispersion model for "non heavy" situations. We have concluded that this neutral model might be too conservative for specific situations, and excludes correction for several potential relevant physical phenomena (such as ground effects, entrainment due to influences of velocity and density influences, and turbulence introduced by the release itself). Therefore the new dispersion model is used as standard for the LOC models.
• The "outflow angle in XZ plane", which is important for the potential jet fire flame orientation, is also being used to determine the dispersion type. Angles smaller than 45 degrees will be modelled as "horizontal jet", any angle above 45 degrees is considered to be a "vertical jet release" for dispersion.

Neutral gas scenarios

The neutral gas "Jet release" mode already combined "turbulent jet" with a fully passive dispersion. In version 11 a discontinuity in concentration level when switching from jet to passive dispersion could occur. This behaviour (basically a too high velocity at the interface from "turbulent jet" to "passive" dispersion) has been improved, leading to smooth transitions and considerable smaller distances for jet releases. Note that we now advise to use the new generic dispersion model for gaseous jet releases, this model also includes more detailed physics like the potential buoyant behaviour of the plume. The fully passive jet modelled distances, as predicted by neutral gas for non or low-buoyant conditions, are now more similar to those predicted by the new dispersion model, but still might differ for non-passive releases.

More technical documentation, describing detailed mathematical background and showing verification and validation of the adapted methods will be provided in the documents section of our download portal.

BLEVE fireball scenarios

The experiments, conducted during the SH2IFT program, showed that a LH2
(liquefied hydrogen) BLEVE actually can occur, but that its heat radiation is very low. According to experimental values we have reduced the SEP (Surface Emissive Power) for a hydrogen BLEVE fireball to 70 kW/m2. This low SEP value was already applied for then hydrogen jet fire and LH2 pool fire.

Project file versions

We have been able to keep the same file format (a compressed XML type) and version 11 files can be opened directly in version 12. Unfortunately, we cannot guarantee downward compatibility. For this reason, we advise to keep project files separated and distinguishable by file or folder naming. The support for version 9 and 10 has been skipped, version 12 no longer reads old ".Riskcurves" extension-type projects. Users should apply version 11 to convert version 9 or 10 files to the current .RSX format.

University edition version

Resolved an issue where loading a university edition project could cause errors depending on the computer configuration.

Several stability improvements for handling large projects.

User interface

Log messages: A transport equipment could provide a misleading log message, which was a warning that the equipment was skipped from calculation whereas all results were available. This warning message is no longer showing.

Consequence risk calculation

When performing a consequence risk calculation to obtain risk for an overpressure threshold level, combined LoC scenarios now correctly adapt the location of the overpressure contours using the potential offset of a vapour cloud explosion. In some cases, this overpressure risk calculation could be using the BLEVE blast or Gas blast offset, which would result in a wrong offset of the contour. This adaptation might provide significantly larger overpressure consequence risk contours for vapour cloud explosion phenomenon in combined LoC scenarios.

User interface

• Project file opening: Opening a project file by double-clicking could trigger errors as a result of the recently introduced asynchronous method of loading and activating the user interface. This potential problem, occurring on very fast PCs, has been fixed.
• Multi language support: The EFFECTS user interface can now also be switched to Spanish (see Edit-Options,Language). The translations (Chinese and Spanish) in the chemical editor have been extended with translated names of chemical properties.
• Calculate from here: When using the option to just calculate one specific node of the project tree, the project file will no longer be backed up before calculation. This improves responsiveness of the program when working with large projects, but should be used with caution. When the user has made considerable changes to the project, it is advised to use the "Calculate" button, which will create a full back-up of the project before initiating the calculation.
• Loading older version projects: When loading projects from earlier editions (version 9 or 10), recently introduced or modified parameters will also be automatically adjusted to defaults.

Flammable dispersion scenarios

The determination of flammable mass and flammable volume of a cloud, requiring a volumetric integration of concentrations, has been converted into a multi-threaded calculation, speeding up these specific calculations (both dense gas and neutral gas flammable cloud). The graph of the flammable cloud volume vs time has been corrected, the volume will now always reduce to exactly zero after the LFL cloud has passed. This change will not affect any risk result.

Combined LoC scenarios

• G2: The "release within 10 minutes" scenario no longer accepts modelling a pipeline connected to a vessel. This release mode, intended to represent a high impact non instantaneous scenario, should model a large release directly from a vessel, applying the associated hole in the vessel.
• G3: When using the "fixed flow rate" method in a G3 (leak) calculation, reloading the project could trigger an "Out of date" warning, requiring to recalculate this scenario. This inconstancy has been fixed.

Liquid LoC and PLG LoC without rainout

The pool evaporation model for boiling (cryogenic) pools from water has been adapted. When using the boiling pool from water while using a confined water surface, the model would assume there was ice formation, and switch to another heat transfer regime. This behaviour might occur only at small-scale (like experimental) releases and is now abandoned. The model will now show similar heat transfer behaviour as with unconfined (free spreading) boiling pool from water. Furthermore, both the "confined boiling from water" and "instantaneous boiling from water" situations will now also fulfil minimum pool thickness requirements and no longer lead to an infinitely thin pool layer thickness. This modification may lead to significantly lower evaporation rates and longer durations for confined or instantaneous Propane or LNG on water situations.

Gas and BLEVE fireball scenarios

The heat radiation side-view graph has been improved, and will show contour dimensions that can differ from the top view shown on the map, which is reporting at a specified height Zd. This adaptation does affect any risk result.

Toxic dispersion scenarios

A potential issue with a "frozen" calculation while searching for an extremely high dosage or very low concentration (toxicity indoors) has been fixed. Furthermore, a "grid spacing error" that might occur when dealing with negligible releases (never reaching lethal levels) has been solved.

User interface

Meteo distribution: Resolved an issue where the meteo distribution graph was no longer visible.

Export wizard

In large projects, a situation could occur where the “Export consequences as CSV” and “Export contour dimensions” wizards would crash. This has been solved.

Toxic dispersion models

For very small releases an issue could occur presenting the contours. This issue has been identified and resolved.

User interface

• Multiple language support: The RISKCURVES user interface can now be completely switched to Chinese language. Other languages will be made available in the near future by providing additional language packs.
  
• Shifted release location on copy: Some users experienced an annoying shift of the release location when performing a “copy to clipboard” of the map view. This issue has been fixed in version 11.4.
• Responsiveness while loading and saving. When loading and saving large projects the application could appear to be “frozen”. This no longer happens and additionally loading- and saving times have been greatly reduced.

Vulnerability

Toxic exposure indoors: The calculation of indoor toxicity can now potentially include a limited exposure duration. This requires an additional “Vulnerability setting” input “Use exposure duration limited indoors toxicity (Yes/No)”, which is only needed when activating the indoor toxicity calculation. In previous versions, we would simply assume that the indoors location would be the escape location, implying that people would continuously be there. This previous method (=selecting “No”) would mean that if a concentration would build up inside, it would also decrease slowly after the cloud passed, potentially still leading to substantial lethality indoors due to long lasting concentration exposure. By selecting “Yes” the inside concentration time graph, which is determining the accumulated dosage, will also be limited to the user defined exposure duration (default 1800 sec). This situation would represent total evacuation of the population after exposure duration. This choice obviously has an important influence on the inside lethality result.

Toxic dispersion scenarios

The toxic dose dispersion scenario (Neutral and Dense gas) will now also report indoors toxicity contours, when indoor toxic calculation is activated in vulnerability settings. Furthermore, the cut-off distance of a toxic calculation will no longer be influenced by a potential “user defined dosage”, which could previously lead to a different calculation domain and thus calculation accuracy.

Pool fire scenario

When applying very short duration continuous release scenario’s, where pool spreading is not finished when the release stops, the pool fire would switch to instantaneous mode. In those situations, the pool area would be set to the defined max. pool area. The improved model will now also check for minimum pool thickness and potentially apply a smaller pool size if the amount of liquid cannot cover this max. area.

Unified LoC scenario

This combined LoC scenario, capable of modelling gas, liquid and two phase releases, could still ask for an input pressure, while the user actually selected “fixed flowrate” requiring a calculation of this associated pressure. These unnecessary inputs are no longer required.

Consequence risk using AEGL3 scenario duration

This specific toxic concentration threshold risk requires calculation of a threshold level based on scenario results (its duration). In case of instantaneous LoC scenario’s, the procedure will now potentially apply pool evaporation source duration if this determines the source duration.

Analysis point reporting

The reporting of risk ranking of consequence risk is now independent of individual risk ranking. In previous version the risk ranking report of consequence risk could be incomplete (no % contribution) if individual risk at the coordinate was zero.

Storage format

The project files are considerably smaller but are not backward compatible. Therefore projects saved with version 11.4 cannot be read with previous versions.

User interface

Multiple language support: The Chinese translations have been improved.

Reading old formats

The conversion of old style “damage definition” scenario’s as used in version 9 and 10.0 has been enabled.

NEW: Imported calculations

Based on feedback from users we have extended the functionality of RISKCURVES with the possibility to import previous calculation results and aggregate this into a combined risk result (cumulating both Individual Risk, Consequence Risk and Societal Risk results). This is specifically intended to avoid huge and calculation intensive projects with hundreds of scenarios, and allows to split full site studies into separate unit studies, providing the possibility to combine them later into a full and complete site study. The imported calculation is shown as a separate branch in the project tree and can be combined with any other part of a project by creating a selection in a “cumulation set”. See the user manual and instruction videos for more information on this new and very convenient feature.

Combined LoC scenarios for two-phase releases

These models are now capable of dealing with pure vapour outflows from top vent PLG releases.

Heavy gas and Neutral gas explosive mass scenarios

Apart from footprint area and mass in the flammable cloud the models now also report volume of the flammable cloud (also versus time).

Jet fire scenario

When using the jet fire model with pure Hydrogen, the model will now apply a reduced Surface Emissive Power, which reflects the low radiation flux of this material.

Importing issues solved

Reading in a version 10.1.4 combined LoC scenario in version 11 could trigger an unexpected error. This issue has been solved. As of version 11.2 the “Outcome” phenomenon
“BLEVE fireball” will now correctly be translated into “Gas or BLEVE fireball”.