• Piping and instrumentation diagram

    Piping and instrumentation diagram

    • A piping and instrumentation diagram/drawing (P&ID) is a diagram in the process industry which shows the piping and vessels in the process flow, together with the instrumentation and control devices.

      A piping and instrumentation diagram/drawing (P&ID) is defined by the Institute of Instrumentation and Control as follows:

      They usually contain the following information:

      P&IDs are originally drawn up at the design stage from a combination of process flow sheet data, the mechanical process equipment design, and the instrumentation engineering design. During the design stage, the diagram also provides the basis for the development of system control schemes, allowing for further safety and operational investigations, such as a Hazard and operability study (HAZOP). To do this, it is critical to demonstrate the physical sequence of equipment and systems, as well as how these systems connect.

      P&IDs also play a significant role in the maintenance and modification of the process after initial build. Modifications are red-penned onto the diagrams and are vital records of the current plant design.

      They are also vital in enabling development of;

      P&IDs form the basis for the live mimic diagrams displayed on graphical user interfaces of large industrial control systems such as SCADA and distributed control systems.

      Based on STANDARD ANSI/ISA S5.1 and ISO 14617-6, the P&ID is used for the identification of measurements within the process. The identifications consist of up to 5 letters. The first identification letter is for the measured value, the second is a modifier, 3rd indicates passive/readout function, 4th - active/output function, and the 5th is the function modifier. This is followed by loop number, which is unique to that loop. For instance FIC045 means it is the Flow Indicating Controller in control loop 045. This is also known as the "tag" identifier of the field device, which is normally given to the location and function of the instrument. The same loop may have FT045 - which is the flow transmitter in the same loop.

      Letter Column 1 (Measured value) Column 2 (Modifier) Column 3 (Readout/passive function) Column 4 (Output/active function) Column 5 (Function modifier)
      A Analysis Alarm
      B Burner, combustion User choice User choice User choice
      C User's choice (usually conductivity) Control Close
      D User's choice (usually density) Difference Deviation
      E Voltage Sensor
      F Flow rate Ratio
      G User's choice (usually gaging/gauging) Gas Glass/gauge/viewing
      H Hand High
      I Current Indicate
      J Power Scan
      K Time, time schedule Time rate of change Control station
      L Level Light Low
      M User's choice Middle / intermediate
      N User's choice (usually torque) User choice User choice User choice
      O User's choice Orifice Open
      P Pressure Point/test connection
      Q Quantity Totalize/integrate Totalize/integrate
      R Radiation Record Run
      S Speed, frequency Switch Stop
      T Temperature Transmit
      U Multivariable Multifunction Multifunction
      V Vibration, mechanical analysis Valve or damper
      W Weight, force Well or probe
      X User's choice (usually on-off valve as XV) X-axis Accessory devices, unclassified Unclassified Unclassified
      Y Event, state, presence Y-axis Auxiliary devices
      Z Position, dimension Z-axis or Safety Actuator, driver or unclassified final control element
      Symbols of chemical apparatus and equipment
      Insulated pipe.svg
      Thermally insulated pipe
      Jacketed pipe.svg
      Jacketed pipe
      Cooled or heated pipe.svg
      Cooled or heated pipe
      Jacketed mixing vessel (autoclave)
      Half pipe reactor.svg
      Half pipe mixing vessel
      Pressurized vessel horizontal.svg
      Pressurized horizontal vessel
      Pressurized vessel vertical.svg
      Pressurized vertical vessel
      Vacuum Pump or Compressor.svg
      Vacuum pump or compressor
      Gas bottle.svg
      Gas bottle
      Axial fan.svg
      Axial fan, ,MK,,,

      Radial fan.svg
      Radial fan
      Fluid contacting column.svg
      Packed column
      Tray column.svg
      Tray column
      Cooling tower.svg
      Cooling tower
      Heat exchanger no cross.svg
      Heat exchanger
      Heat exchanger with cross.svg
      Heat exchanger
      Plate heat exchanger.svg
      Plate & frame heat exchanger
      Double pipe heat exchanger.svg
      Double pipe heat exchanger
      Fixed straight tubes heat exchanger.svg
      Fixed straight tubes heat exchanger
      U shaped tubes heat exchanger.svg
      U shaped tubes heat exchanger
      Spiral heat exchanger symbol.svg
      Spiral heat exchanger
      Covered gas vent.svg
      Covered gas vent
      Curved gas vent.svg
      Curved gas vent
      Dust trap.svg
      (Air) filter
      Steam trap.svg
      Steam trap
      Viewing glass.svg
      Viewing glass
      Pressure reducing valve.svg
      Pressure reducing valve
      Flexible pipe.svg
      Flexible pipe
      Control valve.svg
      Control valve
      Manual valve.svg
      Manual valve
      Back draft damper.svg
      Back draft damper
      Needle valve.svg
      Needle valve
      Butterfly valve.svg
      Butterfly valve
      Diaphragm valve.svg
      Diaphragm valve
      Ball valve.svg
      Ball valve

      • Instrumentation and with unique tag identifiers
      • Mechanical equipment with names and numbers
      • All valves and their identifications
      • Process piping, sizes and identification
      • Miscellanea - vents, drains, special fittings, sampling lines, reducers, increasers and swagers
      • Permanent start-up and flush lines
      • Flow directions
      • Interconnections references
      • Control inputs and outputs, interlocks
      • Interfaces for class changes
      • Computer control system
      • Identification of components and subsystems delivered by others
      • Control and shutdown schemes
      • Safety and regulatory requirements
      • Start-up sequences
      • Operational understanding.
      • - A list of P&ID symbols in SVG format
  • What Else?

    • Piping and instrumentation diagram