Line List

on . Posted in Design Engineering

A line list (or line schedule) is a database created to communicate between the process and mechanical engineering teams when designing piping in a plant or process unit.  At it’s core, it should help provide justification on why certain decisions were made in the design process.  If the maximum pressure is 200psi but the piping code is an ANSI 600 system, it should be documented on the line list.


  • Process Engineers  -  Specifies the process requirements such as the design and operating pressures & temperatures, flowing medium, piping code, Line ID, reference P&ID numbers etc.
  • Mechanical Engineers  -  Contains line numbers, connections, isometric numbers, and other items that are related to the overall construction of the piping.
  • Mechanical Designers  -  Used to ensure that the lines on the P&ID are accurately reflected in the piping design.


At a minimum, the information on a line schedule is as follows  -

  • Line identifier (line designation, line number)  -  a unique number that identifies the line in the plant or process unit.  The author of this article cannot stress enough the use of the word unique.
  • Start and ending point of the line  -  includes equipment connections or connections to other lines.
  • Service or commodity  -  materials that are flowing through the piping
  • Fluid phase  -  liquid, vapor, two phase, etc.
  • Piping specification and/ or piping code
  • Design and operating pressure and temperature of the service
  • P&ID reference numbers
  • Piping Isometric reference number
  • Corrosion allowance
  • Insulation type and thickness
  • Heat tracing type
  • Special calculation requirements such as pipe stress
  • Special Information & requirements such as post weld heat treatment, pickling, hydrotest requirements, etc.


  • Like the equipment index the line list is an evergreen document that cannot be finalized until the overall design is complete.  Piping isometrics are the last drawings created before the project is issued for construction.
  • Updating the line list to include the isometric ensures that all isometrics are created and can help during the QA/ QC process.
  • It is a good practice to include a key or legend to the line identifier or line designation.  Every company as their own standard.  A legend or key ensures the engineering and design company is using the right designation for their project.
  • The line list can also be used for material expediting and tracking.  Additionally, it can be used to verify that the piping spools are all delivered on site, when they are needed.
  • The line list can also be used to ensure line labeling at the end of a project.  Using the line list is helpful for whoever is making the labels to ensure every line is marked to the organizations labeling requirements.
  • If the piping is connected to a piece of equipment with a lower design pressure than the design pressure of the piping, a pressure relief valve should be installed to protect the equipment.  If no such valve is specified, the design pressure of the piping is equal or less than the maximum pressure of the equipment.


  Line ID Start End Service PhaseDesignOperating Insulation Heat TracingDrawings Notes
 10-6"-WW-4867-A-040-A-2"HC-ST 10-6"-WW-4866-A-040-A-2"HC-ST  10-6"-WW-4868-A-040-A-2"HC-ST  Waste Water Liquid 200 150 250 200 2" Steam PD-25091 ISO-10489  PWHT & Stress Calc Required.
10-6"-WW-4868-A-040-A-2"HC-ST 10-6"-WW-4867-A-040-A-2"HC-ST V-202A Waste Water Liquid 200 150 250 200 1" N/A PD-25091 ISO-10490  


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Tags: Design Pipeline