The introduction of Knowledge Management (KM) processes is suggested herein for bridging knowledge gaps observed during long-term and high complexity engineering projects, like the Natural Gas Project (NGP) of Greece, with a view to deploying a dedicated KM system in engineering companies. The model of three essential knowledge management processes (acquisition, maintenance and sharing) is demonstrated, applying the IDEF0 method of functional analysis and design. The functionality of the introduced KM processes has been proved by a case study referring to a pipeline river crossing sub-project.