In BASF chemical engineers use essentially AspenPlus™ and the in-house simulator CHEMASIM for their simulations. CHEMASIM was developed for about thirty years and is tailored to the needs of BASF. With OPEN CHEMASIM™ it is available to the academic community since September 2005 by the University of Stuttgart. The main focus of the thermodynamical calculations in CHEMASIM was the low pressure region. In order to perform calculations also in the high pressure region with modern equations of states the Cape Open Thermo Interface v. 1.0 was implemented in CHEMASIM. As CO compliant Thermo Packages Multiflash™ of InfoChem and AspenPlus™ of AspenTech were used. About the problems during implementation and about operational experiences will be reported.