Which procurement is suitable in MM for this requirement

Dear Experts,

Our client is required to map in SAP as per below, please suggest me which procurement type is suitable for this.

1. Plant A is purchasing material 100 MT from vendor X and that material directly sending to vendor Y for cleaning in various steps without receiving at plant A.
2. After cleaning 100 MT material will become 80 MT at vendor Y.
3. This 80 MT again has to receive at plant A.
4. The initial material value is less while purchasing(100 MT) and after cleaning material value will be high while receiving( 80 MT)

As per me it is not suitable for third party and subcontracting procurement.

Please suggest me how to map in SAP and which procurement is suitable.

Regards,

Hanmanth