What Is a Line List? Piping Index

A line list (also called a piping line index, line schedule, or piping summary) is a master register of every piping line in a project. Each row represents one piping line and records its identification number, pipe class, design conditions, test requirements, insulation type, and tracing needs. The line list is the central reference document that connects P&IDs to piping design, material procurement, and construction.

When the Line List Is Used

The line list is developed during the FEED (Front-End Engineering Design) phase and progressively updated through detailed engineering. It is used by:

• Process engineers: To define design pressure, temperature, and fluid for each line
• Piping engineers: To assign pipe classes and design parameters for isometric drawings
• Stress engineers: To identify critical lines requiring stress analysis
• Materials/procurement: To understand the total line count and material scope
• Construction: To plan fabrication, erection, and testing sequences
• Commissioning: To verify completeness and prepare test packages

A typical large oil and gas project may have 5,000-30,000+ piping lines in the line list.

Line List Field	Description	Example
Line number	Unique identifier (encoded format)	6”-P-HC-10001-A1A-I
From / To	Origin and destination equipment	V-1001 to P-1001A
P&ID reference	Source P&ID drawing number	PID-100-001
Pipe class	Material class code	A1A
Nominal size	Pipe diameter	6” (DN 150)
Design pressure	Maximum allowable pressure	15 barg
Design temperature	Max/min design temperature	-29°C to 150°C
Operating pressure	Normal operating pressure	10 barg
Operating temperature	Normal operating temperature	85°C
Fluid	Service fluid description	Hydrocarbon (HC)
Insulation type	Heat conservation, personnel protection, etc.	Hot insulation (H), Cold insulation (C)
Insulation thickness	Insulation layer thickness	50 mm
Tracing	Steam or electric heat tracing	Steam trace (ST)
Test medium	Hydrostatic, pneumatic, or service test	Hydrotest (HT)
Test pressure	Required test pressure	22.5 barg
PWHT	Post-weld heat treatment required	Yes / No
Stress critical	Requires formal stress analysis	Yes / No
NDT level	Non-destructive examination percentage	10% RT / 100% RT

Line Numbering Convention

Line numbers encode key information about the line. A typical format:

[Size]-[Sequence]-[Fluid Code]-[Area]-[Pipe Class]-[Insulation Code]

Example: 6”-HC-10001-A1A-I = 6-inch, hydrocarbon service, sequence 10001, pipe class A1A, insulated.

The exact format varies by project and company standard, but the line number always includes the size and pipe class as a minimum. These two parameters allow any engineer to immediately understand the material specification and pressure rating of the line.

Pro Tip

The line list is a living document that changes throughout the project. Establish a formal revision control process (typically managed in a database or controlled spreadsheet) and issue updated line lists at defined engineering milestones (30%, 60%, 90%, IFC). Uncontrolled line list changes after material procurement cause costly rework: wrong pipe classes ordered, incorrect insulation installed, or test packages assembled with outdated parameters. Lock the line list at IFC (Issued for Construction) status with a formal change management procedure for any post-IFC modifications.

The line list works in conjunction with the pipe class specification to define the complete technical requirements for each piping line.

Read the full guide to piping engineering