Excise liability in case of returnable packing material

Dear Sir(s),
Our company is selling material PP (Polypropylene Compound) which is dispatched in plastics bags of packing size of 25 kgs. and dispatched 25 bags at a time on a wooden pallet (Pallet- a wooden stand to put 25 bags at one time to sent to the supplier). In most of the cases these pallets are returned and hence no separate charges is made for it. But in one case material is sent along with pallet and it is not returnable!!! My question is whether excise duty should be charged on these pallets??????
Our co. purchases these pallets from other supplier and no excise duty is charged on these pallets.

Thanks & Regards'
Vineet k. vaish