Setting the input data for the Scenario

The new Scenario will be shown as incomplete. This type of Scenario has mandatory input data for the consequence calculations, in addition to the mandatory event frequency field.

Open the input dialog and set the input data as follows:

Scenario tab section

Make sure the Scenario type is set to Line rupture (rather than Disc rupture or Relief valve).

Set the Pipe internal diameter to 25.4 mm, the Pipe length to 9 m, the Release height from vessel bottom to 0 m, and the Elevation to 0.1 m. With this value for Elevation, the liquid droplets will probably not evaporate inside the cloud, and will probably rain out and form a vaporising pool.

Note: the Pipe internal diameter is 1 inch, and the easiest way to set this is to type “1 in” in the input field and press [Tab]. The program recognises “in” as a defined unit for length, and will convert it to the default display units of mm when you press [Tab] or click in a different field.

The Scenario tab includes the Outdoor release direction field, which you should leave with the default value of Horizontal, which is the correct setting for this type of unobstructed rupture of horizontal pipework.

The list of directions includes a second horizontal option: Horizontal Impingement. You should select this option if the release is in a congested area and the release is likely to impinge on a wall or other equipment; the program will reduce the momentum of the release, which will reduce the amount of air mixed into the jet during the initial stages.

Risk tab section

Set the Event frequency to 1E-5 /AvgeYear, i.e. the same value as for the rupture. For pipework failures, the frequency represents a specific length of pipework, e.g. the length between the sphere and an isolation value.

Material tab section

The value that you set for Release height from vessel bottom is below the Tank liquid level that the program calculated when you completed the tank shape data. This means that the initial phase released will be liquid, so the Calculated phase to be released is given as Liquid (release below liquid level).

Short pipe tab section

The Short pipe tab section contains details for the modelling of frictional losses. Leave the pipe roughness with the default value taken from the Parameters, and leave the numbers of valves as zero. There is one bend in the 9 m of pipework, so you should set the Frequency of bends in pipe to 0.11 per m.

Time varying releases tab section

For a newly-inserted Time varying Scenario, the Method for calculating the average rate is set to Average between 2 times, with the times set to 0 s and 20 s.

Leave the tab section with these values. You will perform an initial run of the discharge calculations, then examine the results and decide on the most appropriate way to represent the behaviour for the rest of the consequence analysis, which may involve changing these settings.

This completes the input data for this stage, and you can click on OK to close the input dialog.