How I can remove all schematimes from a phschema? It is not sufficient to remove column from phschema, the schematime remain in memory of the schemaTime.
Correct. You will need to call IphSchemaX3.RemoveSchemaTime on each time item.
To access them all you must iterate over the IphSchemaX3.Layers collection and for each Layer you iterate all phDataEntity. Remeber to iterate backwards if you are about about to Detele the time items (the list will shrink when a time item is removed)