Lesson 1: What a Piping Designer Does — Role, Deliverables and Project Phases

PipingDesigners Beginner Training Series · Module 1 · Lesson 1.1

What you will learn

By the end of this lesson you should be able to:

explain, in a sentence or two, what a piping designer is responsible for;
name the main deliverables a piping team produces and who uses each one;
describe how a project moves from early studies to construction, and what piping does at each stage;
explain why today’s piping work is built around a 3D model, a piping specification held as data, and formal review gates.

1. The job in one sentence

A piping designer works out where every pipe goes, what it is made of, and how it will be built, supported, operated and maintained, then records all of that clearly enough that someone else can buy it and put it together.

That sentence hides a lot. The process engineer decides what the plant must do: which fluids flow where, at what pressure and temperature, and how much. The piping designer turns that into physical reality: a route through real space, around equipment, steel, cable trays and people, using components that are allowed for that service.

You are a translator between the people who think in flows and the people who think in steel, bolts and welds.

2. Who you work with

Piping sits in the middle of most plant projects, so you will talk to almost everyone:

Process engineers, who own the P&IDs and line list. They tell you what each line must carry.
Piping materials engineers, who write the piping specifications (the “specs”): the rules for which pipe, fittings, flanges, valves, gaskets and bolts may be used in each service.
Stress engineers, who check that hot, cold, heavy or vibrating lines will not overstress themselves or the equipment they connect to.
Civil, structural, electrical and instrument teams, who share the same space and need their own routes, supports and access.
Equipment and vendor engineers, who give you nozzle locations and loads.
Construction, operations and maintenance, who have to build it, run it and fix it. They are your most important reviewers.

A good designer asks early and often. A route that suits you but blocks a valve handle, a crane lift or an escape route is a bad route.

3. The deliverables

A deliverable is something the project formally issues. These are the ones you will meet most:

Deliverable	What it shows	Main users
3D piping model	Every line, component and support in its real position	Whole project team, reviewers, construction
Plot plan and equipment layout	Where units and equipment sit	Layout, civil, safety
Piping general arrangement (plans and sections)	Lines in context, usually by area	Reviewers, construction
Isometric drawings (“isos”)	One line at a time, with every dimension, component and weld needed to fabricate it	Fabricators, erectors, inspectors
Bill of materials / material take-off (BOM / MTO)	Quantities of every item	Procurement, material control
Support drawings and support list	Type and location of each pipe support	Fabrication, structural, stress
Line list and tie-in list inputs	Line data and connections to existing plant	Process, construction, commissioning

The important modern point is that most of these are outputs of one model, not separate drawings. The plans, sections, isos and BOM are generated from the same 3D model and the same specification data. If the model is right, the drawings agree with each other. If you edit a drawing by hand and not the model, they stop agreeing — and that is how errors reach site.

4. Specs as data

On older projects a spec was a printed booklet and the designer looked things up. Today the piping specification is loaded into the design software as data. When you model a line in, say, a carbon-steel spec for a given pressure class, the software offers only the components that spec allows, already sized and rated.

That changes your job. You spend less time looking up dimensions and more time making sure:

the right spec is assigned to each line;
the line’s size, rating and service match the line list;
anything the spec does not cover is raised as a query, not quietly invented.

You still need to understand the data, because you have to recognise when something looks wrong. That is why the next module of this series covers sizes, schedules, fittings, flanges and valves.

Try it: open the NPS / DN / OD Cross-Reference and look up NPS 2. Note that its outside diameter is 60.3 mm, not 2 inches, and that the metric equivalent is DN 50. Then open Pipe by Schedule and compare the wall thickness of NPS 2 in two different schedules. Notice that the outside diameter stays the same while the bore changes. This is exactly the kind of data your spec holds for you — and exactly the kind of thing you should be able to sanity-check by eye. Lesson 2.1 covers it properly.

5. The project phases

Names vary between companies, but most projects move through similar stages. Here is what piping typically does in each.

Phase	What the project is deciding	What piping does	Indicative LOD for piping
Concept / feasibility	Is this worth doing?	Rough plot space, major line routes, early cost input	LOD 100: space reservations and symbolic routes; no real components
FEED / Basis of Design (BOD)	What exactly are we building?	Plot plan, equipment layout, main racks, critical lines, early model, preliminary MTO	LOD 200: main lines routed at approximate size and position; racks and corridors fixed
Detailed design	How exactly will it be built?	Full model, all lines, supports, isos, final BOM, model reviews	LOD 300 to 350: every line routed with spec components, valves and supports; interfaces with steel, equipment and other disciplines coordinated
Procurement and fabrication	Buy it and make it	Answer queries, check vendor data, manage revisions	LOD 400: fabrication-level detail such as welds, spool breaks and exact vendor dimensions
Construction and commissioning	Install it and start it up	Site queries, as-built changes, punch-list support	LOD 500: model updated to match what was actually installed (as-built)

The term Basis of Design (BOD) is often used for the FEED stage, because its main output is an agreed basis that detailed design builds on.

The LOD column is indicative only. LOD definitions, and the level required at each stage, vary by project; the project’s BIM execution plan or contract sets the actual requirement. For a stage-by-stage look at LOD and process piping, see Project stages, LOD and process piping.

You will often hear model reviews described by percentage, such as 30%, 60% and 90%. Each one is a review gate: the model is checked against agreed criteria before the work moves on. A typical pattern is:

around 30%: layout, equipment positions, main routes and access are agreed;
around 60%: most lines are modelled, supports and stress-critical lines are being worked;
around 90%: the model is essentially complete and checked, ready for final isos.

Then each iso passes its own release check before it goes to the fabricator. The Isometric Release Gate Checklist sets out what that check covers. The idea behind every gate is the same: find problems while they are cheap to fix. Moving a line in the model costs minutes. Cutting and re-welding it on site costs days.

The Piping Design Checklists tool gives you a structured list of things to look for at review stages. Have a look now, even if many of the items are new to you; by the end of this series most of them will make sense. For the 30%, 60% and 90% model reviews themselves, see the Model Review Checklists.

6. Where the model fits, and where software helps

The 3D model is the single source of truth for the physical design. Around it sit:

the P&ID and line list, which say what must be connected;
the specs, which say what it may be built from;
the codes and standards, which set the minimum rules (see the Standards Index for the main ones you will meet);
the reviews, which confirm it all fits together.

Modern software does a lot of checking for you: clash detection, spec checks, automatic isos and BOMs, and increasingly AI-assisted suggestions for routing and checking. These are genuinely useful and worth learning. But a tool can only check what it has been told to check. Whatever produced a route or a report, a competent person reviews it and signs it off, and that person answers for it. Use the tools to go faster and catch more; never use them as a reason to stop looking.

7. What makes a good piping designer

Skills matter, but habits matter more:

Think like the people who come after you. Can it be built? Can the operator reach the valve? Can maintenance get the pump out?
Keep the model honest. Change the model, not just the drawing.
Know your spec. If it isn’t in the spec, ask.
Check your own work before review. A checklist is a tool, not an insult.
Write things down. Queries, assumptions and decisions should be traceable.

Summary

Piping designers turn process requirements into a buildable, operable physical layout.
The main deliverables — model, arrangements, isos, BOM, supports — are views of one model built from spec data.
Projects move through phases, and review gates at each stage catch problems while they are cheap.
Software, including AI-assisted tools, helps a great deal, but a competent person checks and signs off.

Quick quiz

Who normally owns the P&ID and line list?
a) The piping designer b) The process engineer c) The fabricator
On a modern project, where should isos and the BOM come from?
a) Hand-drawn separately b) Generated from the 3D model and spec data c) Copied from a previous project
You need a fitting that the line’s spec does not include. What should you do?
a) Pick something similar b) Raise a query with the piping materials engineer c) Leave it out
NPS 2 pipe has an outside diameter of about:
a) 50.8 mm b) 60.3 mm c) 52.5 mm
What is the main purpose of a 30/60/90% model review?
a) To find problems while they are cheap to fix b) To produce progress photos c) To replace iso checking
A software tool suggests a route for a line. Who is responsible for it?
a) The software vendor b) Nobody, it was automatic c) The competent person who reviews and signs it off

Answers: 1 b, 2 b, 3 b, 4 b, 5 a, 6 c.

Next lesson

Lesson 1.2 — From process to piping: reading the P&ID and line list.

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