How to Read Pipe Markings and Heat Numbers

What it is

ASTM pipe specifications require each length to be marked. Marking may be rolled, stamped or stenciled. A typical stencil runs along the pipe and shows, in order set by the specification:

• Maker's name or brand
• Specification and grade, such as ASTM A53 Grade B or A106 Grade B
• Type or process, such as seamless or ERW
• Size and schedule or wall thickness
• Hydrostatic test pressure or "NH" if not tested, where the spec requires it
• Heat number
• Other marks, such as NDE, country of origin, or a dual certification

How to read it

1. Find the stencil on the outside, along the length. Small sizes may be marked on a tag on the bundle.
2. Read the spec and grade. A53 is general-purpose pipe. A106 is seamless pipe for high-temperature service. API 5L is line pipe.
3. Read the type. A53 uses S for seamless, E for electric-resistance welded and F for furnace-butt welded.
4. Read the size and wall. Size is NPS. Wall may be a schedule (40, 80) or a weight class (STD, XS, XXS).
5. Read the heat number. It identifies the batch of steel. The mill test report (MTR) for that heat lists chemistry and test results.
6. Look for dual or triple certification, such as "A53/A106/API 5L." The pipe meets each listed spec.

Common stencil items

Key points

• Keep the heat number traceable when pipe is cut. Transfer the marks to each piece if the job needs traceability.
• Paint, coating and cutting can remove the stencil. Mark cut pieces before they are separated.
• See Carbon Steel Pipe — A53, A106 and API 5L and Master Guide to Pipe Sizes, Schedules and Wall Thickness.

Common mistakes

• Selling A53 Type F where the job specifies seamless.
• Losing heat traceability on cut lengths.
• Reading the heat number as a part number.

Governing standards: ASTM A53 and ASTM A106 (marking sections); ASTM A530 (general requirements for carbon and alloy steel pipe); API 5L for line pipe.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.