Piping and Instrumentation Diagram

on 18 January 2016. Posted in Design Engineering

In the design process, a piping and instrumentation diagram, abbreviated as P&ID, is created following the Block Flow Diagram and Process Flow Diagram. The P&ID contains all the piping, valves and instrumentation in a process. The P&ID also shows relationships between control mechanisms such as control valves and level control switches or valve position related to the temperature of a process. Essentially, the P&ID is a roadmap on how the process will function.

P&IDs contain a great amount of detail. The instrumentation tags, line numbers, primary and secondary lines, control mechanisms etc. should all be included on on the P&ID.

P&IDs should	P&IDs should not
The information found on a Process Flow Diagram with the exceptions of what is shown on the right. Instrumentation, designations, types, ranges where applicable, etc All valves, sizes and their identifications Flanges including break out spools for maintenance, spectacle blinds, blind flanges, as appropriate, to define how the process works. All process piping, sizes and identification including all bypass and recirculation lines. Miscellaneous lines and items including vents, drains, special fittings, sampling lines, reducers, and swages Permanent start-up and flush lines Interconnecting references to other systems Control inputs and outputs, interlocks Interfaces for class changes clearly marked Annunciation inputs and outputs Computer control system input Vendor and contractor interfaces (eg skid limits) Identification of components and subsystems delivered by others Intended physical sequence of the equipment Major equipment symbols, names and identification numbers Flow directions	System ratings and operational values as minimum, normal and maximum flow, temperature and pressure Composition of Fluids Show geographical elements of the piping unless the process requires a specific piping orientation as an example, meter runs Instrument root valves control relays manual switches with the exception of HOA or JOA type switches. primary instrument tubing and valves extensive explanatory notes

P&IDs should

P&IDs should not

The information found on a Process Flow Diagram with the exceptions of what is shown on the right.
Instrumentation, designations, types, ranges where applicable, etc
All valves, sizes and their identifications
Flanges including break out spools for maintenance, spectacle blinds, blind flanges, as appropriate, to define how the process works.
All process piping, sizes and identification including all bypass and recirculation lines.
Miscellaneous lines and items including vents, drains, special fittings, sampling lines, reducers, and swages
Permanent start-up and flush lines
Interconnecting references to other systems
Control inputs and outputs, interlocks
Interfaces for class changes clearly marked
Annunciation inputs and outputs
Computer control system input
Vendor and contractor interfaces (eg skid limits)
Identification of components and subsystems delivered by others
Intended physical sequence of the equipment
Major equipment symbols, names and identification numbers
Flow directions

System ratings and operational values as minimum, normal and maximum flow, temperature and pressure
Composition of Fluids
Show geographical elements of the piping unless the process requires a specific piping orientation as an example, meter runs
Instrument root valves
control relays
manual switches with the exception of HOA or JOA type switches.
primary instrument tubing and valves
extensive explanatory notes

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