Process Flow Diagrams (PFDs) - PDF

Plant Diagrams and Drawings • Chapter 2 Objective 2 Explain the use of process flow diagrams (PFDs). Process Flow Diagram (PFD) The process flow diagram (PFD) is a simplified schematic of a plant, or portion of a plant. It uses graphic symbols to show the major equipment items, and the major proce...

Plant Diagrams and Drawings • Chapter 2 Objective 2 Explain the use of process flow diagrams (PFDs). Process Flow Diagram (PFD) The process flow diagram (PFD) is a simplified schematic of a plant, or portion of a plant. It uses graphic symbols to show the major equipment items, and the major process flow between the equipment. The components of the PFDs are not drawn to scale, only the inter-relationships between the equipment in the process are shown, but not in exact orientation. PFDs provide valuable information for plant operating and engineering staff. They help with general understanding of the process flows and control strategy. PFDs are good resources for the purpose of training new personnel. Layout of the PFD A separate PFD may be prepared for each plant process. If a single sheet is too crowded, more sheets may be used. For simple processes, more than one process may be shown on a sheet. Process lines should have the flow rate, direction of flow, and other required data, such as pressures and temperatures. Main process flows should go from the left to the right of the sheet. Line sizes are not shown on a PFD. With PFDs, simplicity in presentation is important. Typical details shown on PFDs include: a) Major process equipment with process line orientation, including proper name and numbering. b) Main piping, including major bypass and recirculation lines, and direction of flow. c) System ratings and operating values including flows and rates, pressure, and temperature values (often at the major vessels or control points). d) General configuration and process orientation of equipment. e) Major instrumentation, such as major control valve locations (excluding isolating and shut-off valves), and basic instrumentation orientation. f ) Make up of fluids in the process. 4th Class Edition 3 • Part A 2-7 Unit A-10 • Fundamental Industrial Communication Skills Process Flow Schematic Diagram Examples Typical process flow schematic diagrams are shown in Figure 3. Figure 3(a) shows the main process flows of a heating ventilation and air conditioning (HVAC) system. Figure 3 – Process Flow Schematic Diagram Examples (a) HVAC Process Flow Schematic Diagram Return Air from Building Axial Fan Exhaust Air R/A Louvres R/A Filters Outdoor Air Supply Air To Building C H S/A C C Steam to Humidifier Glycol to Coil Motorized Dampers Chilled Water to Coil (b) Steam System Process Flow Diagram SG-301A BOILER 122-C HP HEATER 104-J BFW PUMPS 101-U DEAERATOR PI 6200 Kpa 420°C S/H Outlet Header PT PI Super Heater T 115-J CONDENSATE PUMPS C-101 E-117 TURBINE CONDENSER 106-C LP HEATER FT To ATM PI T Press CV T T TI Condensate Lever CV FT 50 mm Hg Abs Boiler TI Feed Reg. LP HTR Bled STM Press CV PI PI FT TI 122-C TI 138 KPa 227°C PI TI HP HTR Bled STM Press CV E-117 FT 101-U PI FT FT © PI 106-C PI PI T 30°C FT ECON. SG301A PT T D/A Bled STM Press CV FT PI Air Ejector C-101 277°C TI NC TI 115-J PI TI T T PS PS TI 2-8 PI PI Boiler Feed Pump TI 4th Class Edition 3 • Part A STEAM PLANT PFD CW Supply