Hi Piyush,
Go to OPUV transaction, open the network type
Here you have Collective requisition, see whether you have checked it.
If you do not set this indicator then a separate purchase requisition is created for every externally processed operation or non-stock component
Pl. Note : Mainly if you choose individual PR for each external activity, you might end up with 'n' no of PR's for a shutdown project.
Regards
Terence