Process engineers determine the size and quantity of the processing facility and they evaluate the entire facility and integrate each section together to ensure the whole plant functions as designed. Accurate detailed process engineering during the initial stages of the project ensures accurate pricing during the detailed design phase of the project. Process engineering simulates the design and expected conditions of the facility to create heat and material balances (H&MBs). Process engineers also create Process Flow Diagrams (PFDs) which become the basis for the plant design. Using the PFDs, design temperature and pressure diagrams are created to ensure all process conditions are considered in the plant design. From the H&MBs, process data sheets are created for quotations from vendors.