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P&ID Training


To improve understanding of pipe and valves to help operating the plant better and safer.

Pipe Codes

Provide comprehensive information for specific piping systems including:

  • Design Conditions
  • Testing / Inspection / Qualifications
  • Gaskets / Bolting
  • Pipe Schedule / Materials of construction
  • Fittings
  • Valves

What is a P&ID?

It is the most important mechanical description of the process operating facilities/units should have

  • Combination of an instrument control diagram and a piping flow diagram
  • Schematic drawings or a set of drawings that join pieces of equipment, instrumentation, and piping
  • Enables one to see processes in a schematic format
  • Contains the detailed pipe, insulation, painting mechanical design for the process
  • Some of the information contained includes:
    • Title Block
    • Revision Block
    • Border
    • Equipment Tabulation
    • Line Legend
    • Line Numbering

P&ID Title Block

Contains several items to identify the drawing such as

  • Drawing Number
  • Revision Number
  • Approvals
  • Building, Project, Design Area, and Drawing Type
  • Drawing Name
    • Site
    • Unit
    • Process Description

Border and Revision Block

  • Provides a grid system to identify the location of items.
  • Used to quickly locate information on the P&ID
  • Documents and provides approvals for changes to the P&ID
  • Provides grid information for locating revision on the drawing

The Equipment Tab denotes the common names and unique Identification Numbers of all equipment on the P&ID.

Equipment Numbering Example

Connected equipment such as a pump and motor will have the same Area and Unit ID, but different item and part number identifications.

  • Pump #1 is 0805-0200-0400
  • Pump #1 Motor is 0805-0200-0460


Revision Triangle

Line Legend

  • Line legend indicates the types of lines and their respective uses on the drawing
  • Not always complete, as is the case with this example drawing


Line Numbering

Pipelines will have the following information:

  • Description and/or number of equipment or line
  • Reference drawing number the line originated from or continues on
  • Nominal pipe size
  • Line number



Insulation Specification

Comprehensive code providing information concerning the type, thickness, and options of the required insulation.


Protective Coating Specification

  • Defines coating specification for the equipment or piping.
  • Contains general information on the coating system as well as specifics on:
    • Type of Coating System
    • Surface Preparation
    • Application
    • Inspection

Automatic Valves

Many symbols are in use to represent different types of automatic valves.

Oval contains indicator for valve failure mode:

  • A/O – Air pressure required to open valve
  • A/C – Air pressure required to close valve


Pipe and Flange Leaks

A review of 800+ Process Incidents found:

  • A large percentage of the incidents involved leaks (big surprise)
  • The most common source of these leaks was flanges!



  • The most common source of leaks leading to incident is flanges. We should aim to change that.
  • Flanges should not be expected to leak. Do not accept flange leaks! Investigate and Improve.
  • Gasket selection is not just about chemical compatibility. Different gasket styles, materials, thicknesses have widely varying mechanical properties.
  • Need have well-founded target bolt load for assembly based on engineering review of the entire flange assembly (including gasket and fasteners). It cannot be based on a rule-of-thumb regarding fastener stress level. Optimized assembly minimizes leakage and increases tolerance for relaxation.
  • To achieve the specified Target Bolt Load you must:
    • First understand the fastener specifications, fastener condition and lubrication to be used so that the nut factor (a measure of friction) can be estimated.
    • Then specify a torque value that will develop the target bolt load based on the estimated nut factor. 
    • Torque and friction must always be considered together, and instructions pertinent to both issues provided. Just specifying a torque value isn’t good enough.
  • For critical and problematic flanged joints special provisions are warranted to reduce variability in assembly and risk.
  • Fastener tightening steps and patterns are geared towards bringing the flanges together squarely and resulting in evenly compressed gasket and evenly loaded fasteners.



Tags: Training P&ID