June 2010 Dear Phast User,

About Phast v6.6 We are pleased to announce the release of Phast v6.6 containing updates in a number of areas of the program and a new extension containing more advanced methods for calculating the risks from vapour cloud explosions. Many of the new features and enhancements are described briefly below. For a full detailed description, please refer to the release notes.

Major New Features and Enhancements - For Consequence and Risk

Droplet Modelling enhancements As well publicised over the last few years, DNV Software has initiated a number of Joint Industry Projects (JIP) to improve the modelling of rainout. The most recent of these, JIP Phase 3, on flashing and sub-cooled liquid releases, has provided improved correlations to characterise droplet size and size distribution. This new correlation is included in Phast v6.6 as a non-default option. Although validated against droplet size measurements, it may require further refinement before it can be successfully validated against rainout measurements. In the meantime the default remains the CCPS correlation included in previous releases.

Improved Unified Dispersion Model There are two versions of the Unified Dispersion Model (UDM) available in Phast v6.6. The UDM Version 1 (default) model is the one currently available in v6.54 and earlier versions, whilst the UDM Version 2 model is an enhanced model introduced in v6.6. UDM 2 has improved modelling of droplets inside the cloud, and of evaporation and dispersion following rainout. It also gives greater control over the time-steps at which dispersion results are reported. In addition, UDM 2 includes improved CO2 modelling as described below.

CO2 Modelling

Solid Effects This new feature has been described in detail in recent Status Notes and there is a Technical Datasheet available should you require more information. To use the improved CO2 modelling you must select UDM Version 2 as described above. In v6.54 solid CO2 phase was never allowed for a released component, only liquid or vapour. Liquid properties would be applied resulting in post-expansion temperature being too low, liquid fraction being too high or a failure of the UDM to converge. In v6.6 using UDM Version 2, upstream of the orifice the release phase is still presumed to be either liquid or vapour but post-atmospheric expansion and during UDM dispersion, solid properties can be applied rather than liquid properties.

Non-Ideal Gas Effects For discharge of supercritical CO2 from long pipelines v6.54 assumed the gas to be ideal while v6.6 includes non-ideal (compressibility) effects. At very large pressures, non-ideal effects are important and may therefore significantly increase the expelled mass.

Toxic Effects In order to asses the possible toxic effects of CO2 it is necessary to define it as a toxic material and specify the appropriate probit function. Furthermore, we recommended you set the core averaging time equal to the toxic averaging time of 600 seconds. This will only affect the results following transition to passive dispersion, and for most scenarios the cloud is no longer hazardous at this distance.

In v6.6 several warnings have been added to indicate when less accurate results might be expected due to solid effects not being handled. We therefore recommend that you switch on warnings using the menu Options->Preferences->General and check Display Warning Messages on the Miscellaneous tab. A detailed description of CO2 modelling can be found in the HSE C02 paper available on HSE's web site at: www.hse.gov.uk/seveso/co2-hazardous-substance.pdf

Major New Features and Enhancements - For Risk Extended Risk Reporting

The Extended Risk Reporting, which is available in Phast Risk only, is built around a SQL Server database and uses Risk Framework technology to provide powerful graphing and data drill-down capabilities for detailed analysis of risk results. The Extended Risk Reporting provides many different charts and reports which are described in more detail in the Release Notes. When you first run the Extended Reporting, the first report displayed is the Risk Dashboard. This includes a default selection of risk metrics intended to give you an immediate overview of the key risk contributors in your study. In addition, the Extended Reporting allows you to explore risk results more transparently. All results can be filtered and grouped by event, outcome, weather and direction, population category and area.

In addition you can: Drill-down on the FN Curve to find the outcomes contributing to the risk at any point, view

FAR, N, RI values by area and population category

Contour risk to any effect level (eg overpressure) or combination of effects If you have licensed the Extended Explosion Modelling you can also:

Filter and group all results by building type Produce Exceedence Curves for Overpressures or impulse at ranking points

The Extended Reporting uses Filter Sets to help you organise and analyse results. These are managed using the Filter Set Manager which is described in more detail in the Release Notes. Three Filter Set types are available; societal, risk contour and risk ranking point. The program allows you to edit existing or create new Filter Sets and then select any of these from the Filter Set list. The options available then change depending on the type of Filter Set selected. Once a Filter set is created, you can generate the relevant reports or charts using the appropriate Results Processor buttons. A typical screen image highlighting the Filter Set Manager and Results Processor panes is shown below. More information is provided in the Release Notes.

Extended Explosion Modelling (chargeable extension)

Extended Explosion Modelling is available only for Phast Risk users who purchase a separate license for the extension. It relies on the Extended Risk Reporting functionality for presentation of results. If you have licensed the extended explosion modelling, then you have the option to use a different method for modelling explosions in the risk calculations. The standard explosion modelling does not consider the nature of the confinement or obstructions in the area affected by the dispersing cloud, and it does not calculate overpressure or impulse. The new method allows you to define regions of congestion and confinement within your model. The calculations will then consider the interaction between the dispersing cloud and these regions and calculate the overpressure and impulse generated if the cloud is ignited within an obstructed region or regions.

You can also define any number of sets of explosion vulnerability parameters, defining the relationship between overpressure and impulse to fatality-probability for different groups of people (e.g. for people in different types of building), and for different types of risk-presentation (e.g. for societal risk or individual risk). Phast Risk v6.6 with the Extended Explosion modelling is able to provide much more accurate predictions of the probable explosion damage and resulting lethality.

The Multi-Energy Method and Baker-Strehlow-Tang Model have been implemented within the extension, both of which are widely accepted for calculating effects from gas explosions. The risk calculations also take into account buildings and occupant vulnerability. Using this extension provides increased accuracy and transparency when calculating risks from vapour cloud explosions.

Results Processor

Filter Set Manager

The workflow for creating a model using the new functionality is as follows:

Define appropriate Obstructed Regions on your map - these are used to define levels of congestion and confinement and thus assess maximum expected overpressure and overpressure decay if an explosion occurs

Define Building Types an empty Building Set is provided for you where you can define all the different buildings you require.. An example Building set is available for download from the support website.

Provide data for vulnerability characteristics for Toxic, Explosion Overpressure, Radiation and Flash Fires effects for each Building Type you have defined

Define Buildings on your map - each building belongs to a specific Building Type and you can insert population from a range of Categories within each building

Associate buildings with areas if desired This is useful when performing risk assessment and mitigation (e.g. reporting separately on risks to those onsite and offsite or personnel in storage, production and admin areas)

A more detailed and comprehensive description of the new modelling is available in the V6.6 Release Notes and Theory Documents provided with the release.

For more information about licensing this extension, please contact your local DNV Software Sales Manager.

Other New Features and Enhancements

Below we provide brief descriptions of a number of the other enhancements provided in v6.6 which we believe may be of general interest to you.

For Consequence and Risk

Time Varying Discharge The robustness of the thermodynamic calculations has been improved and the calculations now include the ability to model systems containing vacuum relief valves. The documentation has been consolidated and updated to reflect these enhancements.

Long Pipeline Model The model has been enhanced to handle non-ideal gas and two new valve types have been added; an excess flow valve and a non-return valve.

New Report Export to Excel This new feature allows you to export a wide range of consequence results to Excel. This can be useful for exporting results for multiple concentrations of interest to a spreadsheet for graphing and results comparison, for example.

Excel Import and Export Improvements All new objects and several previously unhandled objects can be exported to and imported from Excel. For Phast this includes Jet Fire, Pool Vaporisation, TNT Explosion, ME Explosion, BST Explosion, BLEVE Blast, External Connection, Feature Class and Raster Image. As with 6.54, Caselist, Effect Model & Parameters are not included.

Pool Vapourisation When using the Version 2 UDM, the standalone pool source model now gives results which are consistent with those from rained out pools in the linked modelling. When using the pool source model in v6.54, creating a user-defined source from a standalone pool could give very different results to an equivalent case with 100% rainout of liquid spill. This inconsistency has been largely removed. The 'trailing pool' model used in v6.54 when initiating dispersion from a pool which has been left behind by a dispersing vapour cloud is now also used for the standalone pool source model. The link between the cloud and the pool has also been improved.

Convert Case List to Model You can convert multiple or single case lists, or individual cases within lists, to equivalent models using this new feature. This can prove extremely useful when you are re-structuring studies or using spreadsheet import/export.

For Risk only Excel import and Export improvements All new objects and several previously unhandled objects can be exported to and imported from Excel. For Phast Risk, this includes: Jet Fire, Pool Vaporisation, TNT Explosion, ME Explosion, BST Explosion, BLEVE Blast, External Connection, Feature Class, Raster Image, Building Type, Building, Defined Strength Obstruction Group, Defined Strength Obstruction, Calculated Strength Obstruction Group, Calculated Strength Obstruction, Defined Flame Speed Group, Defined Flame Speed, Calculated Flame Speed Group, Calculated Flame Speed, Population Set, Risk Ranking Point and Risk Transect. As with 6.54, Run Row Set, Run Row, Caselist, Effect Model, Parameters & Vulnerabilities are not included.

Risk Transect improvements Risk Transects are now defined by adding them to a Risk Transect Set on the Risk Tab. Only one Risk Transect Set is allowed but this may contain any number of transects. In addition, you can now define a Risk Transect as a Polyline as well as a Line.

Changes to results With each new version of the product, you are likely to see some changes to results in existing studies. This version is no exception and the release notes go into the details, with more technical description in the theory documents. A brief summary of areas where you are likely to see changes is given below. full description can be downloaded from the support website.

UDM Version 1 (Default) Using this dispersion model, most results will be the same. However, there have been some bug fixes in the atmospheric property calculations which could result in some differences.

New UDM Version 2 and Droplet Correlations The new UDM and Droplet Correlations described above will have a significant effect on results. However, the existing v6.54 options have been retained as the default in v6.6, so you will not see any impact on results from these enhancements unless you select the new options.

Time Varying Discharge and Long Pipelines Significant improvements have been made to the time varying discharge model and these will have an unavoidable effect on the results. The Long Pipeline model for gases now considers compressibility by default. This will typically lead to more mass being released than for an equivalent release treated as an incompressible gas. The 6.54 method is retained as a non-default parameter (Ideal gas modelling). Additionally, improved models for choked flow and time interpolation have been implemented for the long pipeline model for gases which will generally lead to larger flow rates.

Jet Fire Duration Adjustment In 6.54 and earlier versions, jet fires were assumed to have a duration corresponding to the jet fire maximum exposure time parameter which defaulted to 20s. The lethality calculations will now use the actual duration if shorter than this parameter. Therefore, for release durations less than 20s, Jet fire lethality ellipses will get smaller.

There are other smaller changes, including bug fixes, which will also affect results and these are described in more detail in the release notes.

Thank you for your continued support of DNV Software products and we look forward to serving your software needs now and in the years to come.

Kind regards,

Dr Nic Cavanagh Head of Safeti Business Development DNV Software