A complete collection of the most used P&ID symbols for lines, piping, valves, instruments, pumps, compressors, pressure equipment and other mechanical equipment.
Table of Content
- 1 WHAT IS P&ID?
- 2 LINES P&ID SYMBOLS
- 3 PIPING P&ID SYMBOLS
- 4 VALVES P&ID SYMBOLS
- 5 FILTERS P&ID SYMBOLS
- 6 INSTRUMENTS P&ID SYMBOLS
- 7 ISA SYMBOLOGY
- 8 SYMBOLOGY FOR POWER SUPPLY
- 9 SYMBOLOGY FOR INSTRUMENTATION SIGNALS
- 10 PUMPS P&ID SYMBOLS
- 11 COMPRESSORS P&ID SYMBOLS
- 12 VESSELS P&ID SYMBOLS
- 13 MOTORS, GENERATORS, TURBINES P&ID SYMBOLS
- 14 HEAT EXCHANGERS P&ID SYMBOLS
WHAT IS P&ID?
P&ID is the acronym for “Piping and instrumentation diagram”, i.e. a very detailed diagram showing the processes happening within a plant, the involved equipment, and their interconnections.
A set of standardized P&ID symbols is used by process engineers to draft such diagrams. P&ID symbols exist for all major components and lines, such as valves, vessels, instruments, pumps, compressors, and towers. The ISA S5.1, ISO 10628, and BS 5070 cover the standardization of P&ID symbols and guide process engineers in their plant design activities.
The most common P&ID symbols are listed below:
- piping components (pipes, flanges, and fittings)
- instruments and instrumentation
- electrical machines (motors, generators, and turbines)
- heat exchangers
The symbology for the identification of the measurement and control instrumentation on the flow and process diagrams and on the P&ID (Piping & Instrument Diagram), commonly called P&I (Piping & Instrumentation), is generally compliant with the Standard ISA (Instrumentation Society of Automation) identified as S.5, that is composed of identification codes and graphic symbols.
The symbology of the instrument it is placed in a circle of 7/16 “or 12 mm (see below), was in the top there is the functional identification (of the instrument or device) composed with max 5 letters, and in the bottom there is identification of the loop (measurement and/or control) consists of a progressive number of 3 or 4 numbers, followed by a literal suffix to identifies two or more identical instruments inserted in the same chain and therefore having the same functional identification;
The circle that identifies the instrument or device has:
- Continue Line in the center: for an instrument suitable for control room mounting
- The dotted line in the center: for an instrument suitable for technical room mounting
- No line in the center: for an instrument suitable for field application
If an instrument has a circumscribed square means that it is an integrated instrument as a function in a DCS (Distributed Control System) or PLC (Programmable Logic Controller).
|Functional identification||Loop identification|
Graphical representation of a temperature recorder controller of the 101A loop, suitable for control room mounting
The following tables show:
– Table 1 identifying the function of the instruments or devices
– Table 2 the graphic identification of the valves
– Table 3 the graphic identification of the actuators
– Table 4 identifying the safety conditions of the valves and actuators
At the end will also be reported the literal and graphic symbols of the power supplies and signals of the instrumentation.
TABLE 1 – FUNCTIONS OF INSTRUMENTS
|FIRST LETTER||FOLLOWING LETTERS|
|Measured variable||Modified||Passive function||Active function||Modifier|
|C||User (1) choice||Control|
|D||User (1) choise||Differential|
|G||User (1) choice||Glass (2)|
|K||Time schedule||Time rate of change||Control station|
|M||User (1) choise||Momentary||Meddle
|O||User (1) choice||Orifice
|P||Pressure or vacuum||Point test|
|Q||Quantity||Totalize or integrate|
|W||Weight or force||Well|
|Y||Event||Axis Y||Calculation module (5)|
|Z||Position or dimension||Axis Z||Unclassified final element|
|(1) It must be chosen uniquely for each project. For example C – Conductivity; D – Density; etc.
(2) Glass instruments that allow the visualization of process data
(3) Very high or maximum is indicated with HH
(4) Very low or minimum is indicated with LL
(5) To define the Y function on a diagram, add the specific symbol of the relay or convert to a square of 6 mm on the side of the graphical sign of the instrument (in the north-east position).
TABLE 2 – INSTRUMENTATION VALVES SYMBOLS
TABLE 3 – ACTUATORS FOR INSTRUMENTATION VALVE SYMBOLS
TABLE 4 – IDENTIFICATION OF SAFETY CONDITION FOR VALVES AND ACTUATORS (WITHOUT SUPPLY)
SYMBOLOGY FOR POWER SUPPLY
AS – Ais Supply:
IA – Instrument Air
PA- Plant Air
ES – Electrical Supply
GS – Gas Supply
HS – Hydraulic Supply
NS – Nitrogen Supply
SS – Steam Supply
WS – Water Supply
SYMBOLOGY FOR INSTRUMENTATION SIGNALS
The table shows the symbology of control signals for instrumentation