A common change that needs to be done to the units of a *.c2 file is to convert it to use OD units for diameter, rather than nominal units.  When designing systems with tubing, the OD is a required variable. By default, the units of CAESAR II are set as Nominals active.  Here are the steps to turn nominal units off. 


Go to create/review units
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Follow these clicks to make a new units file, base it off of whichever existing unit file you want.
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When you edit the new unit file, make sure you set NOMINALS = OFF
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Click OK /Save, then review the new units file you created, to verify you set nominals as off.
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Then go to "change model units".  Follow the dialog prompts to convert your existing file to use the new units file without nominal sizes active.
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After that, open up the file you converted.  You should be able to type in exact values for pipe OD now. 
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