Process flow diagram

Process Topology: Symbols for PFD

Process and Instrument Symbols

Information Provided in a Flow Summary Required InformationOptional Information Stream Number Temperature (°C) Pressure (bar) Vapor Fraction Total Mass Flowrate (kg/h) Total Mole Flowrate (kmol/h) Individual Component Flowrates (kmol/h) Component Mole Fractions Component Mass Fractions Individual Component Flowrates (kg/h) Volumetric Flowrates (m 3 /h) Significant Physical Properties Density Viscosity Other Thermodynamic Data Heat Capacity Stream Enthalpy K-values Stream Name

Meanings of Identification Letters O Orifice PPressure or VacuumPoint QQuantity or Event RRadioactivity or RatioRecord or print SSpeed or FrequencySwitch TTemperatureTransmit VViscosityValve, Damper, or Louver WWeightWell Y Relay or Compute ZPositionDrive First Letter (X)Second or Third Letter (Y) AAnalysisAlarm BBurner Flame CConductivityControl DDensity or Specific Gravity EVoltageElement FFlowrate HHand (Manually Initiated)High ICurrentIndicate JPower KTime or Time ScheduleControl Station LLevelLight or Low MMoisture or HumidityMiddle or Intermediate level transmitter (LT) level indicator and controller (LIC)

Equipment Descriptions for PFD and PIDs Description of Equipment Towers Size (height and diameter), Pressure, Temperature Number and Type of Trays Height and Type of Packing Materials of Construction Heat Exchangers Type: Gas-Gas, Gas-Liquid, Liquid-Liquid, Condenser, Vaporizer Process: Duty, Area, Temperature, and Pressure for both streams Number of Shell and Tube Passes Materials of Construction: Tubes and Shell Tanks and Vessels Height, Diameter, Orientation, Pressure, Temperature, Materials of Construction Pumps Flow, Discharge Pressure, Temperature, ΔP, Driver Type, Shaft Power, Materials of Construction Compressors Actual Inlet Flowrate, Temperature, Pressure, Driver Type, Shaft Power, Materials of Construction Heaters (Fired) Type, Tube Pressure, Tube Temperature, Duty, Fuel, Material of Construction Other Provide Critical Information

Symbols for Stream Identification [View full size image] Benzene Process Flow Diagram (PFD) for the Production of Benzene via the Hydrodealkylation of Toluene

Electrical drawing

Electrical drawing - Example

Reasons for Elevating Equipment Equipment to Be ElevatedReason for Elevation Columns or vesselsWhen the NPSH available is too low to avoid cavitation in the discharge pump, equipment must be elevated. ColumnsTo provide driving head for thermosiphon reboilers. Any equipment containing suspended solids or slurriesTo provide gravity flow of liquids containing solids that avoids the use of problematic slurry pumps. Contact barometric condensersThis equipment is used to produce vacuum by expanding high- pressure steam through an ejector. The condensables in the vapor are removed by direct contact with a cold-water spray. The tail pipe of such a condenser is sealed with a 34-foot leg of water. Critical fire-water tank (or cooling water holding tank)In some instances, flow of water is absolutely critical, for example, in firefighting or critical cooling operations. The main water supply tank for these operations may be elevated to provide enough water pressure to eliminate the need for feed pumps.