ASME SA-240 vs ASTM A240: Key Differences Explained

Quick Answer

The confusion between ASME SA-240 and ASTM A240 is one of the most common documentation issues in pressure equipment fabrication. The short answer is: they cover the same material, but they live in different regulatory ecosystems and carry different legal implications depending on what you are building.

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Background: How ASME Adopts ASTM Standards

The ASME Boiler and Pressure Vessel Code (BPVC) does not independently develop most material standards. Instead, ASME's Committee on Materials (BPV II) periodically reviews and adopts ASTM material specifications into BPVC Section II, Parts A (ferrous) and B (non-ferrous).

When ASME adopts an ASTM standard:

1. The ASTM designation is prefixed with "S" (A240 → SA-240).
2. The full ASTM text is incorporated by reference, sometimes with modifications or additional requirements.
3. The ASME version is frozen until ASME formally adopts the next ASTM revision — meaning the SA-240 in a given code edition may correspond to an earlier ASTM revision year.

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Side-by-Side Comparison

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When You Must Use SA-240

SA-240 is mandatory when the fabricated component falls under any of the following:

• ASME BPVC Section VIII, Division 1 or 2 — unfired pressure vessels
• ASME BPVC Section I — power boilers
• ASME B31.3 — process piping (when the owning specification requires it)
• National Board inspection — any jurisdiction requiring ASME code compliance

In these contexts, presenting an MTC citing only ASTM A240 without the ASME SA-240 dual citation is a non-conformance. The Authorized Inspector (AI) will require corrective action before the vessel can be code-stamped.

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When ASTM A240 Alone Is Sufficient

A240 without the ASME SA designation is fully acceptable for:

• Non-pressure structural applications
• Food and pharmaceutical equipment not subject to ASME jurisdiction
• Architectural cladding and decorative panels
• Storage tanks designed to API 650 or similar non-BPVC codes
• Projects governed by EN, IS, or other national standards

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Dual Certification: The Practical Solution

Many mills routinely produce material that meets both A240 and SA-240 requirements simultaneously and will certify to both on the same MTC. A dual-certified MTC reads:

Material manufactured and tested in accordance with:
ASTM A240 / ASME SA-240, Type 316L

This is the preferred approach for service centers and distributors holding inventory that may be sold into either pressure or non-pressure applications. Dual certification does not cost more and maximizes material flexibility.

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Supplementary Requirements: Where SA-240 Diverges

ASME BPVC Section II introduces mandatory supplementary requirements (marked "S" in the ASME text) that do not exist in ASTM A240. The most important for fabricators:

Heat Treatment Documentation

SA-240 requires that the heat treatment method (furnace type, temperature, quench medium) be documented on the MTC for certain grades. ASTM A240 requires the condition to be stated but is less prescriptive about furnace documentation.

Charpy Impact Testing

For low-temperature service, BPVC may require Charpy V-notch impact testing at specified temperatures, which must be documented on the MTC. ASTM A240 only requires this when specified on the purchase order.

Pressure Test (when invoked)

SA-240 supplementary requirement S6 mandates a specific hydrostatic test regime not present in the base ASTM standard.

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MTC Review: Checklist for Pressure Vessel Applications

When reviewing an MTC for material going into a code-stamped vessel, verify:

• Both ASTM A240 and ASME SA-240 are cited (or SA-240 alone)
• Grade and UNS number are specified
• Heat number is present and matches physical marking
• Chemical analysis values are within A240/SA-240 limits for the grade
• Tensile, yield, elongation values meet minimums
• Hardness value is within limits
• Heat treatment condition and temperature are stated
• Certificate is signed by an authorized mill representative
• Any BPVC supplementary requirements invoked on the PO are addressed

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Edition Mismatch Risk

Because ASME adopts ASTM at a lag, there can be a difference between the current ASTM edition and the edition incorporated into the active BPVC code year. For example, if a project is built to the 2021 ASME BPVC, the adopted SA-240 may correspond to A240-19 even though A240-22 is the current ASTM edition.

Best practice: specify the BPVC code year on the purchase order, not just "ASME SA-240," so the mill can certify to the correct edition.

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Frequently Asked Questions