Piping and instrumentation diagram

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Piping and instrumentation diagram of pump with storage tank. Symbols according to EN ISO 10628 and EN 62424.

A piping and instrumentation diagram/drawing (P&ID) is a diagram in the process industry which shows the piping of the process flow together with the installed equipment and instrumentation.

Contents and Function[edit]

An example of a P&ID.

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

  1. A diagram which shows the interconnection of process equipment and the instrumentation used to control the process. In the process industry, a standard set of symbols is used to prepare drawings of processes. The instrument symbols used in these drawings are generally based on International Society of Automation (ISA) Standard S5. 1.
  2. The primary schematic drawing used for laying out a process control installation.

P&IDs play a significant role in the maintenance and modification of the process that it describes. It is critical to demonstrate the physical sequence of equipment and systems, as well as how these systems connect. 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 commonly pronounced as HAZOP.

For processing facilities, it is a pictorial representation of

  • Key piping and instrument details
  • Control and shutdown schemes
  • Safety and regulatory requirements
  • Basic start up and operational information

List of P&ID items[edit]

  • Instrumentation and designations
  • 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 swaggers
  • Permanent start-up and flush lines
  • Flow directions
  • Interconnections references
  • Control inputs and outputs, interlocks
  • Interfaces for class changes
  • Computer control system input
  • Identification of components and subsystems delivered by others

Identification and Reference Designation[edit]

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.

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 Safety 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 Actuator, driver or unclassified final control element

For reference designation of any equipment in industrial systems the standard IEC 61346 (Industrial systems, installations and equipment and industrial products — Structuring principles and reference designations) can be applied. For the function Measurement the reference designator B is used, followed by the above listed letter for the measured variable.

For reference designation of any equipment in a power station the KKS Power Plant Classification System can be applied.

Symbols of chemical apparatus and equipment[edit]

Below are listed some symbols of chemical apparatus and equipment normally used in a P&ID, according to ISO 10628 and ISO 14617.

Symbols of chemical apparatus and equipment
Pipe.svg
Pipe
Insulated pipe.svg
Thermally insulated pipe
Jacketed pipe.svg
Jacketed pipe
Cooled or heated pipe.svg
Cooled or heated pipe
Autoclave.svg
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
Pump.svg
Pump
Vacuum Pump or Compressor.svg
Vacuum pump or compressor
Bag.svg
Bag
Gas bottle.svg
Gas bottle
Fan.svg
Fan
Axial fan.svg
Axial fan
Radial fan.svg
Radial fan
Dryer.svg
Dryer
Fluid contacting column.svg
Packed column
Tray column.svg
Tray column
Furnace.svg
Furnace
Cooling tower.svg
Cooling tower
Heat exchanger no cross.svg
Heat exchanger
Heat exchanger with cross.svg
Heat exchanger
Cooler-symbol.svg
Cooler
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
Funnel.svg
Funnel
Steam trap.svg
Steam trap
Viewing glass.svg
Viewing glass
Pressure reducing valve.svg
Pressure reducing valve
Flexible pipe.svg
Flexible pipe
Valve.svg
Valve
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

See also[edit]

External links[edit]