Defining three flammable releases

There is a propane sphere at the far north of the site. The propane sphere has the same dimensions as the chlorine sphere and the same design of pipework, and is also operating under saturation conditions at atmospheric temperature.

Setting the input data for the propane Equipment item

You can define the propane sphere Equipment item and all of the Scenarios by copying the chlorine Equipment item and its Scenarios and simply changing the selection of discharge material and the geographical co-ordinates for the vessel.

Copying the Equipment item

Select the Chlorine Pressure Vessel, copy and paste it, and name the copy Propane, Saturated 10 degC.

Changing the Material selection

Open the input dialog for the propane Pressure Vessel, and change the selection for the Material field from CHLORINE to PROPANE. After you make the selection there will be a brief pause while the program calculates the saturation pressure at 10oC and the mass for the inventory, and then displays the changed values in the dialog.

Changing the coordinates

In the Geometry tab, set the new location as shown in the illustration. After changing each value you should press [Enter] to

“commit” the changed value.

This completes the work on the input data, and you can OK the dialog.

You do not need to make any changes to the input data for the Scenarios, as the values that are set in the Scenario dialogs are appropriate for the propane vessel. However, you can delete the Time varying Scenario, as you will not be performing the investigation of the time-varying behaviour for the propane vessel.

Running the consequence calculations and viewing the results

Select the Propane Equipment node and run the calculations for all three Scenarios.

You can view the results for all three Scenarios at the same time, as long as you view the results for the same single Weather for all Scenarios. To do this, move to the Weathers tab of the Study Tree, select the Category 1.5/D Weather, and then click on the Graphs option in the Home tab of the Ribbon Bar.

In the Results selection dialog that appears, check the box next to the propane Equipment item to select all of the propane Scenarios for plotting, click on the right arrow to move the items to the Selected items list, and then click Finish to view the Graphs.

The Graph View will contains tab sections for Concentration graphs, as with the toxic Models, but it will contain Jet fire, Fireball, Pool Fire, Explosions and Flash Fire tab sections instead of the Toxic tab section.

The main features of the graphs are described below.

Jet Fire Graphs

The Jet Fire tab section contains three graphs, which are presenting results for the two pipework failures. The first graph shows radiation level versus distance, the second shows Intensity Radii to the lowest of the three default radiation levels set in the input data (4 kW/m2), and the third graph shows Lethality Radii to a lethality level of 1%. The maximum downwind effect distance shown in these graphs is around 33 m, which is the distance for 4 kW/m2 for the liquid line rupture release.

If a given Fire Radii graph is showing results for more than one Scenario or more than one Weather, then it will initially only be displaying results for a single level, which will be the lowest level set for that type of result (e.g. the lowest intensity level, or the lowest lethality level). This is different from a graph for a single Scenario and Weather, which will initially always display results for all available levels.

To see results for additional Fire Radii levels, click on Series… in the Configuration tab of the Ribbon Bar to open the Edit Series Properties dialog as shown. This dialog lists each of the available level-results for each Scenario, and you can check the boxes for additional levels to include them in the graph.

Pool Fire Graphs

There are two sets of Pool Fire Graphs: a set for the early pool fire, which is modelled for a continuous release only and occurs at the beginning of the release, at the time when the spill rate into the pool equals the fire burn rate, and a set for the late pool fire, which occurs at a time when the pool has reached its maximum radius. Each set contains three graphs, as with the jet fire graphs.

The early pool fire graphs are showing results the liquid line rupture release, as this is the only continuous Scenario that gives rainout, and this means that the two Radii graphs will initially be showing the results for more than one level. The maximum downwind effect distance is about 16 m, to a radiation level of 4 kW/m2 for late pool fire, and the distance to a.lethality level of 1% is about 13 m. The late pool fire graphs show results for both the liquid line rupture and the catastrophic rupture, so they initially show results for only one level.

Fireball Graphs

The Fireball tab section contains five graphs, with graphs of the time-dependent geometry and surface emissive power in addition to the three graphs of radiation results. The graphs show results only for the rupture, and this means that the two Radii graphs will initially be showing the results for more than one level. The maximum downwind effect distance is about 660 m, to a radiation level of 4 kW/m2, and the distance to a .lethality level of 1% is about 260 m.