Carbon Steel Pipe (A53, A106, API 5L)

What it is

ASTM A53 covers black and hot-dip galvanized welded and seamless steel pipe for general mechanical, pressure and plumbing uses. ASTM A106 covers seamless carbon steel pipe for high-temperature service, common in process plants and power piping. API 5L covers line pipe for oil and gas pipelines. Dimensions and schedules for all three follow ASME B36.10M, so a given NPS and schedule has the same OD and wall thickness no matter which spec it is made to.

How to read it

The stencil on the pipe lists the maker, the specification and grade, the type (welded or seamless), the size and schedule or wall, the heat number and the hydrostatic test or nondestructive test marking the spec requires. Pipe marked "A53/A106/API 5L Gr B" is multi-certified. It meets the chemistry, testing and marking rules of each listed spec, so one stock item can be sold against any of them.

Specification comparison

Key points

• A53 Type F (butt welded) is common in small sizes for low-pressure service. Many codes and engineers do not allow it for higher duty. Check the job spec.
• A106 is seamless only. If the job calls for A106, welded A53 Type E is not an approved substitute even in the same grade.
• Grade B is the most stocked grade in all three specs. Grade affects strength, not size.
• Check the local code before using galvanized pipe in any system. Welding or cutting galvanized pipe gives off zinc fumes and needs fume controls.
• Allowable pressures depend on the piping code (such as ASME B31.1, B31.3 or B31.9), wall thickness, temperature and joint type. Do not quote pressure ratings from the spec alone.

Common mistakes

• Treating "schedule 40 black pipe" as one product without knowing the spec the customer needs.
• Substituting A53 for A106 on a high-temperature process line.
• Cutting the stencil off and losing traceability to the mill test report.
• Assuming API 5L X grades are interchangeable with A106 grades.

Governing standards: ASTM A53; ASTM A106; API 5L; ASME B36.10M (welded and seamless wrought steel pipe dimensions); the governing piping code.

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.