Everything you need to understand piping, from first principles to inspection.
Eight focused, standards-aligned guides that take you from what a pipe actually is, through pipe class, specifications, sizing and schedules, all the way to how pipe is made, marked and tested. Built for engineers, estimators, inspectors and students.
Start here
What is piping?
Quick answer
Piping is the system of pipes, fittings, flanges, valves and supports that carries fluids between equipment in a plant. Each line is built to a piping class — a specification that fixes the material, pressure-temperature rating, wall thickness and approved components — so the whole system stays safe and compatible.
This hub breaks that down into clear, practical guides. Whether you are picking a schedule for a line, decoding a pipe class on a P&ID, or signing off an inspection report, start with the topic you need below — or follow the learning path from the ground up.
The guides
Eight guides that cover piping end to end
Each guide is a standalone deep dive. Together they form a complete piping foundation.
Pipe
The complete starting point: what a pipe is, how it differs from tube, the common materials, and where each type is used across process, power and utility plants.
Read guide →What Is Pipe and Pipe Class?
Understand piping classes (pipe specs): how design pressure, temperature, material and corrosion allowance are bundled into one class that governs every component in a line.
Read guide →Piping Specifications and Components
A field guide to what a piping spec controls: pipe, fittings, flanges, gaskets, bolting, valves and branch connections — and how the spec keeps them all compatible.
Read guide →Pipe Dimensions
Outside diameter, wall thickness and how NPS maps to real dimensions — the geometry behind every pressure, weight and stress calculation you will run.
Read guide →Pipe Sizes and Schedules
How NPS and schedule number (Sch 40, 80, XS, XXS) set wall thickness, and how to read a pipe dimension table with confidence in any unit system.
Read guide →Piping Color Codes and Identification
The pipe marking and color-code standards (such as ASME A13.1) that tell crews what is flowing inside a line at a glance — and keep work sites safe.
Read guide →Seamless Pipe Manufacturing Process
From billet to finished pipe: piercing, elongation, sizing and finishing — and why seamless pipe is chosen for high-pressure and critical service.
Read guide →Pipe Inspection, Testing & Marking
Hydrostatic testing, non-destructive examination, dimensional checks and heat-number traceability that prove a pipe meets its specification before it ships.
Read guide →Suggested order
New to piping? Follow this path
Read in this sequence to build understanding layer by layer.
Pipe
Get the big picture: what pipe is and where it fits.
Pipe and pipe class
Learn how a class ties material and rating together.
Specifications and components
See every component a spec controls and why.
Dimensions
Understand OD, wall and how NPS maps to real numbers.
Sizes and schedules
Pick the right schedule for a given service.
Color codes and identification
Read a line safely on site.
Seamless manufacturing
Know how pipe is actually produced.
Inspection, testing and marking
Confirm a pipe meets its spec before use.
Answers
Piping questions, answered briefly
What is piping in engineering?
What is a pipe class or piping specification?
What is the difference between pipe size and pipe schedule?
What does NPS mean?
Why is seamless pipe used for critical service?
How are pipes identified on site?
Put the theory to work
Once you know your pipe class and schedule, run the numbers. Explore AIEnginear’s free engineering calculators for sizing, pressure and fabrication.
Open the calculators