Setting Up a Central ESR for PI - CE Scenarios 
ES Repository is delivered as part of SAP NetWeaver Composition Environment (CE) and SAP NetWeaver Process Integration (PI). If you have an SAP NetWeaver CE installation in your landscape, and want to install SAP NetWeaver PI, then you have two ES Repositories. One ES Repository is delivered with SAP NetWeaver CE and the other with the SAP NetWeaver PI. In such cases, where you have SAP NetWeaver CE and SAP NetWeaver PI installation in your system landscape, SAP recommends that you maintain all your design objects in one ES Repository.
Recommendation
SAP strongly recommends that you use the ES Repository delivered with SAP NetWeaver PI.
You can set up the ES Repository delivered with CE as a central ES Repository. However, this is not recommended. More information: Configuring ES Repository on Composition Environment to be used with PI