Additionaly, to assign blank Spool id's.
Please follow the steps below.
1. Go to 'Piping > Piping Tools > Assign Spool ID's...'.
2.Remove the value from 'Starting SpoolID' (i.e., it's blank), then check 'Reassign Existing Spool IDs' and press 'Ok'.
3. Select all the components and complete the process. All spool IDs will be unassigned.
Hope this helps !