Process engineering involves translating the needs of the customer into (typically) production facilities that convert "raw materials" into value-added components that are transported to the next stage of the supply chain, typically "packaging engineering".
Prior to construction, the design work of process engineering begins with a "block diagram" showing raw materials and the transformations/unit operations desired. The design work then progresses to a process flow diagram where material flow paths, storage equipment (such as tanks and silos), transformations/Unit Operations (such as pasteurisation, mixing, separations, sterilization, etc.) and e.g. flowrates are specified. Additionally a list of all pipes are defined together with their contents and material properties such as density, viscosity, particle size distribution, flow rates, pressures, temperatures and specific materials of construction for the piping and unit operations.
The process flow diagram is then used to develop a process and instrumentation diagram (P&ID) which includes sizing information to address the desired flowrates, process controls (such as tank level indications, material flow meters, weighing devices, motor speed controls, temperature and pressure indicators/ controllers, etc.). The P&ID is then used as a basis of design for developing the "functional design specification" which outlines the operation of the process. From the "P&ID", a proposed layout (general arrangement) and other engineering disciplines are involved such as civil engineers, IT, , etc.). Prior to finalize the design an HAZOP study is advisable. In this phase the design will be challenged against process safety point of view.
All previous work is directed toward defining the scope of the project, then developing a cost estimate to get the design installed, and a schedule to communicate the timing needs for engineering, procurement, fabrication, installation, commissioning, startup, and ongoing production of the process. Depending on the needed accuracy of the cost estimate and schedule that is required, several iterations of designs are defined and generally provided to customers or stakeholders. The process engineer incorporates their feedback, additional requirements and wants (scope revisions) into the overall design and additional cost estimates and schedules are developed for funding approval. For larger projects a Value Engineering is advisable. This is concept review by a multidisciplinary team (teammembers + non project related people) and the purpose is to challenge the concept to see if the current concept is the best value for money.
Projects are validated according the V-model: