3 PERFORMING THE CONSEQUENCE ANALYSIS

Defining the pressure vessel that contains a toxic material

Move to the Models tab section. You will start by defining the Pressure Vessel Equipment item that contains a toxic material.

The vessel is a sphere with a radius of 3.37 m and volume of 120 m3 and a maximum fill-level of 85%, containing chlorine at saturation conditions and ambient temperature. The sphere is located near the centre of the site and is elevated 4 m above the ground. There is no bund surrounding the sphere.

Turn on the option to insert Equipment on the GIS

In the Settings tab of the Ribbon Bar, check the option to Insert Equipment on GIS. By default this option is turned off, and when you insert an Equipment item the icon will appear immediately in the Study Tree. If you turn the option on, then the Equipment icon will not appear in the Study Tree until you have clicked on the GIS Input View to set the location for the Equipment item.

In this tutorial you will insert the Equipment items on the GIS View in approximately the correct location, and then correct the location as necessary in the input dialog.

Insert a Pressure Vessel Equipment item

In the Models tab of the Study Tree, select the Study, then insert a Pressure vessel using either the right-click menu or the Insert gallery in the Home tab of the Ribbon Bar. The GIS Input View will become selected, the cursor will turn to crosshairs, and you should click at a point near the centre of the site as shown to place the Pressure Vessel.

After you have clicked, an icon will be added to the Study Tree, and a dot will appear in the GIS View to show the location of the Pressure Vessel. The icon

will be shown as greyed out in the tree, since there are not yet any Scenarios defined underneath it, which means that it has no Scenarios that are selected in the Models Playlist for the active Run Row.

In the Study Tree, rename the node to Chlorine, Saturated 10 degC.

Setting the input data for the vessel

The Pressure Vessel node will have a red error icon at the top left, indicating that it does not have a full set of input data. You will not be able to run the consequence calculations for any Scenarios under the Pressure Vessel until you have supplied values for all of the mandatory input fields, as described below.

Double-click on the icon for the Pressure Vessel to open the input dialog.

Most of the fields in the first tab section will be blank, and those that are enabled will have red borders and error icons. A field with a red border is a mandatory field: you must supply a value for such a field if it is enabled, and you will not be able to run the calculations for Equipment items or Scenarios that have any mandatory fields unset.

This section describes each tab section in turn, including those that are not relevant to this particular hazardous event. Click on the Help button in the dialog to open the online Help if you want further information at any point.

The Material tab section

To set the Material, select CHLORINE from the dropdown list of all of the materials that are defined in the System Materials.

The vessel is a sphere with a volume of 120 m3. This Equipment item will represent the vessel with the maximum degree of filling, which is 85%. Check the Specify volume inventory? box to select this method of specifying the inventory instead of giving the mass and enter a value of 102 m3 in the

Volume inventory field.

The chlorine is held under saturation conditions at atmospheric temperature. The temperature will vary depending on the season and time of day, but for this Equipment item a value of 10oC will be used as representative. To set these process conditions, set the Specified condition to Temperature/bubble point and set the Temperature to 10 degC, as shown below. When you move the cursor away from the Temperature field the program will calculate the saturation pressure for this temperature and display it in the Pressure field.

To define the process conditions for a material that is not held under saturation conditions (e.g. a gas or a padded liquid), you must set the Specified condition to Pressure/temperature and give values for both.

The Geometry tab section

Set the East co-ordinate to 198492 m, and the North co-ordinate to 435063 m.