ASTM A106 vs A53 pipe: which one to specify

What is the difference between ASTM A106 and ASTM A53?

ASTM A106 vs ASTM A53

A106 is a seamless-only carbon steel pipe specification written for high-temperature service. A53 is a general-purpose pipe specification that allows seamless and welded manufacture and can be supplied black or hot-dip galvanized.

Both specifications are dimensioned to ASME B36.10M, so a Schedule 40 NPS 4 pipe has the same OD and wall in either. See Pipe schedules explained.

Is seamless pipe better than welded pipe?

Seamless pipe has no longitudinal weld, so there is no seam to fail and the wall is uniform around the circumference. Welded pipe is made by forming strip or plate and welding the seam, which makes it cheaper and available in tighter wall tolerances in some sizes.

Piping codes recognise the difference. ASME B31.3 applies a longitudinal weld joint quality factor to pipe: 1.00 for seamless pipe such as A106 and A53 Type S, and 0.85 for electric-resistance welded pipe such as A53 Type E. A lower factor reduces the allowable pressure or forces a thicker wall for the same design.

Furnace-butt welded A53 Type F is the lowest tier. Several codes and owner specifications restrict it to low-hazard utility service, so check the piping class before accepting it.

Seamless is not automatically required. Water, air and low-pressure utility lines are routinely built with welded A53. Process lines that are hot, cyclic or flammable normally call for seamless A106.

What do Grade A, B and C mean?

The grade sets minimum strength. Higher grades carry more carbon and manganese.

Grade B is by far the most ordered. Grade A is sometimes chosen when a pipe must bend or coil easily. Grade C is rarer and is selected for higher strength where the design allows a thinner wall.

Where is each used, and what about temperature?

A106 Grade B is the default pipe for refinery, petrochemical and power-plant process lines, steam and hot hydrocarbon services. A53 Grade B, often welded, is the default for plant utilities, fire water, instrument air and general mechanical use.

The ASTM specification does not set the design temperature. The allowable stress at temperature comes from the piping code, for example the tables of ASME B31.1 or B31.3, and it falls as temperature rises. Carbon steel held for long periods above about 425 °C (800 °F) can lose strength through graphitization, so the designer limits the range.

At the cold end, impact testing rules in the code apply below about −29 °C (−20 °F) for common carbon steel pipe. For lower temperatures, specify a low-temperature seamless grade such as ASTM A333 Grade 6 rather than A106.

For sour service, neither A106 nor A53 is sour-rated by itself. See NACE MR0175 / ISO 15156 for buyers.

Can A53 pipe replace A106, and what is dual certification?

A53 Type E or Type F pipe cannot replace A106, because A106 is seamless-only. Even A53 Type S seamless pipe qualifies as A106 only if it also meets every A106 requirement, including the silicon minimum, and carries an A106 certificate.

That is what dual certification means. A mill makes seamless pipe whose chemistry and tests satisfy both specifications, then issues one material test report listing, for example, ASTM A106 Grade B and ASTM A53 Grade B Type S. Seamless line pipe is sometimes also certified to API 5L Grade B. See API 5L PSL1 vs PSL2.

• If the specification says A106 Grade B, ask for pipe certified to A106 Grade B, with or without A53.
• If it says A53 Grade B, seamless A106 Grade B pipe normally meets it, but get the engineer's approval before offering it.
• Never infer dual certification. Read it on the material test report.

A change of specification is the engineer's decision. Ask for written approval before accepting any substitute. See Material test reports for what to check on the certificate.

What should an RFQ for carbon steel pipe state?

• Specification, grade and, for A53, type (S, E or F), with the edition
• Seamless required, or welded accepted
• Dual certification required, allowed or not wanted
• Size as NPS and schedule, or OD and wall thickness
• Length: single random, double random or cut length
• Ends: plain, beveled or threaded; coating: black, varnished or galvanized
• Testing beyond the specification: hydrostatic test, NDE, impact or hardness
• Certificate: EN 10204 type 3.1 or 3.2, with heat numbers
• Quantity, delivery place and Incoterm

The guide How to write an RFQ covers the commercial fields.

How can JJ Projects help?

JJ Projects sources carbon steel pipe to specifications such as ASTM A106, ASTM A53 and API 5L, and checks certificates against the purchase order. Send grade, NPS, schedule and documents through Request a quote, or see steel and structural products.