Service BOM - Usage

Dear SAP Gurus,

I have created Service BOM for several Materials in the system but when I am trying to use this BOM in the Structural List in Service order I get the error saying "Enter Valid object carrrying structural List".

Eg:- For the Pump I am repairing the BOM contains : 1. O-Ring Seal 2. Shaft Seal 3.Rotary Kit

Now when I create a service Order for Pump , I would like to pick Sub-items 1 and 3 as the spares consumables for the order.

But actually, in SAP Order am not able to do so..........

Please let me know if any setting w.r.t BOM is needed at the background.

Thanks

Prasad Subramanya