Unit System

You can set the units you prefer to use in AFT Fathom in the Unit System section. Once selected as the preferred units, these units appear as the default units in all instances in which empty fields exist in the model input. Any model input existing prior to changing the Preferred Units will maintain the units used when the data was input, regardless of changes made to unit preferences. After saving your preferred units, a window appears asking if you would like the output parameters to be displayed in your preferred units. Choose Yes if you do want the output parameters to be displayed in the preferred units, or No if you want the output parameters to be displayed in the units used prior to making changes to the preferred units.

Preferred Units

To customize the units used by AFT Fathom, first select Preferred Units under the Unit System section in the User Options window under the Tools menu.

AFT Fathom allows you to specify certain units from a large selection to be displayed in the main interface.

The primary selection is the Unit System:

US - Only US units will be available
Metric - Only Metric units will be available
Both with US Defaults - All Units will be available, but US units will be chosen by default
Both with Metric Defaults - All Units will be available, but Metric units will be chosen by default

Additionally, a filter can be applied to limit the selection:

All Units - all units for the Unit System will be displayed
Common Only - only "common" units will be displayed
Common Plus Selected Industries - Units particular to certain industries can be included with the common units

If the selection has been limited to Common Only, there may units common for certain industries no longer present. The Additional Units for Industry section allows the user to append additional sets of units to the Common unit set. For example, barrels/day is a common unit in the petroleum industry but not many others. Checking the Petroleum box adds these units to the main interface.

Preferred Units allows fine grain control over what unit in the above selection is displayed as the default when defining model input. For example, it may be desired to have a particular parameter such as pipe diameter default to inches, while keeping other parameters metric. This area allows the user to define such defaults.

Show/Hide Unit Items

For additional control of the available units, select Show/Hide Unit Items under the Unit System section. From here, you can select which units for each Unit Family Type you would like to be available for the model input and output by checking the box next to each unit you would like to be used. Removing units that you do not wish to use as input or view as output can simplify your modeling and reduce errors associated with incorrect units.

Edit Custom Unit Names

A custom unit name can be assigned to display different names in the interface for units. For example "feet/min2" could be changed to display as "ft/min²".

To assign a custom unit name choose the appropriate Unit Type from the drop-down and enter the Custom Unit Name in the table.

To speed up the process of entering custom unit names, the units can be exported to *.csv and re-imported as follows:

Click "Save Units to CSV" and save the file where it will be easy to locate
Open the *.csv file in a spreadsheet editing software like Excel, and fill in the desired custom unit names in the Custom Name column
Save the *.csv file
In the User Options window click "Load Units from CSV" and select the edited *.csv file

Note: To use units with superscripts, make sure the *.csv file is saved with UTF-8 encoding. This can be done in Excel by choosing Save As and selecting "CSV UTF-8" as the file type.

Note: Regions outside the United States that use commas as the decimal separator may have *.csv files that are delimited with semicolons (this was a change made by Microsoft). AFT software requires true comma delimited files. A workaround for such regional users in Excel is listed below.

Workaround for regional users with alternate decimal separators (e.g. Europe):

In Excel go to File > Options > Advanced
Under the Editing Options heading, uncheck the box for "Use system separators"
Change the "Decimal separator" to a period symbol (.)
Change the "Thousands separator" to a comma (,)
Save the *.csv file
Re-check the "Use system separators" option to revert to the default Excel settings