A system to pressurize barrier fluid of a submersible installation to provide a differential pressure between the ambient pressure surrounding the submersible installation and the pressure of the barrier fluid internally in the submersible installation during submersion of the system, wherein the differential pressure fits within a predetermined differential pressure range. The system comprises a pre-charge arrangement and a pressure intensifier which is adapted to start working at a start-up pressure. The pre-charge arrangement is adapted, during submerging of the system, to provide a differential pressure within the predetermined differential pressure range until the ambient pressure equals the start up pressure of the pressure intensifier, while the pressure intensifier is adapted to provide a differential pressure within the predetermined differential pressure range when the ambient pressure equals the start-up pressure of the pressure intensifier during further submersion of the system.