Defining the third scenario: toxic vapour from pipework

The vapour release is the rupture of a two-inch pipe attached to the top of the sphere. The line runs 3.4 m horizontally, then vertically downwards, and the rupture is assumed to occur 1 m from the ground.

Create the Scenario as a copy of the Line rupture, liquid Scenario, rename the copy to Line rupture, vapour, and change the input data as follows:

The release rate from the two-inch vapour line is similar to that from the one-inch liquid line, and the two pipework releases give very similar effect distances.

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.

Setting the input data for the fire modelling

If you move to the Fireball, Jet fire or Pool fire tab sections, you will see that three levels of radiation intensity are specified, but that the calculations for radiation dose, probit and lethality are all unselected. These calculations are not selected by default because they can be time-consuming, so you would normally only select them if you know that you need them for a particular analysis or a particular Equipment item or Scenario.

For this tutorial you will set the lethality calculations to selected and specify five levels of lethality.

In the Fireball tab, take the following steps to specify the lethality levels:

1.Check the Calculate lethality box.

2.Set the value for Number of input radiation levels to 5, and then press [Tab] to commit this changed value so that so that the number of rows in the Radiation levels table changes from 3 to 5.

3.If you cannot see the Lethality levels column in the table, drag the triangle made of six dots at the bottom right of the table in order to resize the table until you can see the column and also the rows for all five levels.

4.Set values of 0.01, 0.1, 0.2, 0.5 and 1, as shown below. After typing each value, make sure to press [Enter] to commit the value.

Next, repeat these steps in the Jet fire tab section and then in the Pool fire tab section.

The values for radiation lethality levels that you set for the Propane Pressure Vessel will be used in the calculations for all of the Scenarios under the vessel. If you want to set values that will be used for all flammable Scenarios in the analysis, you should set them in the Parameters tab section of the Study Tree instead of in the data for individual Equipment items or Scenarios. In this situation you would need to perform the steps above in the dialogs for three different Parameter nodes: Fireball and BLEVE Blast parameters, Jet fire parameters, and Pool fire parameters.

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.