To create a class definition (P&ID only)

On the ribbon, click Home tab Project panel Project Manager Project Setup.
In the Project Setup tree view, expand P&ID Class Definitions.
Continue to expand the list until you locate and click the class definition you want to use as the basis for the new class definition.

Note:
Select a class definition that most closely represents the class definition you want to create. The node you select is used as the template for the new class definition.
Right-click the selected class definition. Click New.
In the Create Class dialog box, enter a class name and a display name (if necessary) for the new class definition. For example, customvalve and Custom Valve.
Note:
Use only letters, numbers, and underscores for class names--no spaces. Limit names to 31 characters. Longer class names can cause problems during export and import.

Also, do not start a class name with a number.
Click OK.
In the tree view, expand the node where the new class definition is added, and click the new class definition.
On the Class Settings pane, make the desired changes.
Click OK.