Inserting a Short pipe Scenario and set up the equivalent input data

The Short pipe Scenario models the same type of hazardous event as the Time-varying short pipe release Scenario, but it calculates the initial discharge rate, without performing any time-varying discharge modelling. Inserting this Scenario involves repeating some of the data-input, but this is the approach taken in this tutorial as it will make the analysis clearer and easier to maintain: if you need to change some aspect of the input data you can edit the Scenario and rerun the calculations, whereas if you used a User-defined release Scenario you would have to edit and rerun the Time-varying Scenario first, then create a new User-defined release Scenario, and delete the previous User-defined release Scenario.

Before you insert the Short pipe Scenario, rename the Time varying Scenario to add “- time-varying not needed” at the end of the name.

Next, insert a Short pipe Scenario, name it Line rupture, liquid, and then edit it and set the values as follows:

The Release height from vessel bottom field is not included in the input data for a Short pipe Scenario, which means that the program is not able to calculate the release phase, and you must use the Phase to be released field to specify whether you want to model a release from the liquid side or the vapour side.

You will see that there is no Risk tab in the dialog. This is because the Mode is set to Discharge instead of Risk. When the Mode is set to either Discharge or Consequence, the input dialogs only include the fields that are used in the consequence calculations, and the fields that are specific to the risk calculations do not appear.

To complete the full data for the Scenario, change the Mode to Risk, and then open the dialog again, move to the Risk tab, and set the Event frequency to 1E-5 /AvgeYear.

Run the consequence calculations for the Short pipe and view the results

Select the short pipe Scenario and select Run. When the calculations are complete, view the graphs for all of the Weathers.

You will see that there is a Pool Vaporisation tab in the Graphs View, which means that the liquid in the release did rain out. If you view the reports and look at the Commentary Report, you will see that rainout fraction is about 0.7 for all three Weathers, and the formation and behaviour of the pool will have an effect on the dispersion and on the toxic effects.