Line List.
A line list is the master register of every numbered process pipe in a facility, with metadata including line number, size, pipe spec, service, design temperature and pressure, insulation, and the from-and-to equipment tags. It is the piping engineering peer to the I/O list and the instrument index.
Three drawings included on a new account.
What Line List means.
A line list is the piping discipline's master register, one row for every numbered process pipe in a facility, and it is the structural peer of the I/O list and the instrument index. Each row carries the line number in whatever convention the project uses, a form like 6-PG-101-A1 that already encodes size, service, sequence, and pipe spec, the nominal size, the pipe spec that bundles material, schedule, end connection, gasket, and bolting, the fluid service, the design and operating temperature and pressure, insulation and tracing, the from-and-to equipment tags, and the P&ID reference. The reason its accuracy matters is that the pipe spec drives procurement and construction. A carbon-steel line and a stainless line of the same size want different valves, gaskets, and welding procedures, and an error on the list propagates straight into the material take-off and the field. The most error-prone elements are spec breaks, the points, usually at a flange where one line transitions from one spec to another, and the list records the break and the drawing page that shows it. Unlike the cable schedule or the datasheet, this is data the P&ID genuinely carries. The line number, size, spec, service, and routing between equipment are drawn on the sheet, including the break notation, so a careful reading of the set produces the line list directly rather than as a downstream document that needs other sources to complete.
What columns appear on a line list
Line number, per the project numbering convention, often size-service-sequence-spec like 6"-PG-101-A1. Nominal size. Pipe spec, which encapsulates material, schedule, end-connection, gasket, bolt material. Service, the fluid service class and process medium. Design and operating temperature and pressure. Insulation type and thickness if applicable. Heat tracing and steam-tracing requirements. From and to equipment tags. P&ID reference. Test pressure and inspection class. Material balance reference.
Why pipe-spec accuracy matters downstream
Pipe spec drives material procurement. A 6"-CS-A106B line wants different material, different valves, different gaskets, different welding procedures than a 6"-SS316-A312 line. Errors on the line list cascade into the procurement package and into construction. Spec breaks, where one section of a line transitions from one spec to another, often at a flange are the most error-prone elements. The line list captures the break location and references the relevant P&ID page where the break is shown. Tagsight extracts line specs as drawn including the break notation.
Worked example, decomposing a line number.
Take the line number 6"-P-1204-A1A-H. The project line numbering philosophy is the only authority on which field is which, and it will name them in that document, but on this common pattern the fields read as follows. The 6 inch is the nominal bore, which decides which row of the piping class table applies and drives the isometric take-off. P is the service or fluid code, here process, which drives material selection and tells you what hazard the line carries. 1204 is the sequence number, unique within that service and unit, and it is the field that makes the line number a key. A1A is the piping class, which fixes material, pressure rating, corrosion allowance, examination percentage and test pressure in one token, and which is why a class change anywhere along the run needs a spec break drawn on the P&ID. H is the insulation code, here heat conservation, which drives the insulation take-off and often the tracing requirement with it. The reason this decomposition matters on a line list is that most of the columns are derived from these fields rather than entered independently, so a line number that is wrong in one field produces a row that is wrong in five columns.
Line list columns and the document each value comes from
The line list is a joining register. Almost every column is owned elsewhere, which is why it is the first document to drift after a P&ID revision.
| Column | What it records | Document that owns the value |
|---|---|---|
| Line number | The full tagged identifier of the pipe run | The P&ID |
| Nominal size | The bore of the line | The line number on the P&ID |
| Piping class or spec | The material, rating and construction class the line is built to | The piping material specification |
| Service or fluid code | What the line carries | The line number and the process description |
| From and to | The origin and destination equipment, nozzle or line | The P&ID |
| Design pressure and temperature | The conditions the line is designed for | Process datasheets and the piping class |
| Operating pressure and temperature | Normal running conditions | The heat and material balance |
| Test pressure and test medium | Hydrotest or pneumatic test condition | The piping class and the code of construction |
| Insulation type and thickness | Heat conservation, cold service, personnel protection or acoustic | The insulation specification |
| Heat tracing | Steam or electric tracing, and the temperature to maintain | The tracing design |
| Paint or coating system | External protection system | The coating specification |
| Examination requirement | The percentage and method of non-destructive examination | The piping class and the code of construction |
| Post weld heat treatment | Whether welds must be heat treated | The piping class |
| Stress analysis flag | Whether the line needs a formal flexibility analysis | Piping stress engineering |
| P&ID number | The drawing the line appears on | The P&ID set |
| Isometric number | The fabrication drawing for the run | Piping design |
| Revision and status | Current issue state of the record | Document control |
How a line number decomposes
Almost every project uses the same four to six fields in a different order with different separators. The project's own line numbering philosophy is the only authority on which field is which.
| Field | What it carries | What it controls downstream |
|---|---|---|
| Nominal size | The bore, in inches or millimetres | Which piping class table applies, and the isometric take-off |
| Service or fluid code | An abbreviation for what flows in the line | Insulation, tracing, material selection and the hazard it carries |
| Sequence number | A unique serial within the service and unit | Uniqueness across the plant |
| Piping class | The material, rating and corrosion allowance package | Valve and fitting selection, examination, test pressure |
| Unit or area | Which process unit the line belongs to | Which drawing set and which turnaround owns it |
| Insulation code | Sometimes carried in the line number rather than as a separate column | Insulation take-off |
Common questions
Is the line list the same as the line schedule.
Does the line list show every pipe in the plant.
Who is responsible for the line list and when is it issued.
Get the line list template.
Line number, service, spec, size, design conditions and insulation, laid out the way a piping register is issued. Plain .xlsx.