ASTM A213 T9/T11/T22/T91 Alloy and Stainless Tubing for Boilers and Heat Exchangers

Where These Tubes Work Best (and Why Stainless Often Wins)

Power boilers, HRSGs, petrochemical heaters, and compact heat exchangers all rely on ASTM A213/SA213 seamless tubes. When chloride-bearing condensate, frequent wet–dry cycles, or tight cleanliness demands are on the table, austenitic stainless grades (TP series) tend to outperform chrome-moly ferritic grades thanks to superior general corrosion and pitting resistance, smoother internal finish, and easier cleaning. High-temperature, dry service with strict creep margins still keeps T-grades in play-especially for superheater and reheater banks.

Typical use cases:

Stainless (TP304/304H, TP316L/316H, TP321/321H, TP347/347H): heat exchangers, condenser bundles, feed-water heaters, corrosive or cyclic-wet service.

Alloy ferritic (T9, T11, T22, T91): hotter superheater/reheater sections and headers where long-term creep strength dominates.

astm a213 sa213 seamless tubing bundles t11 t22 t91-octal pipe chrome moly boiler tubing sa213 t22 t91 packed for shipment-octal pipe

Choosing Stainless vs. Chrome-Moly: A Practical Path

A simple way to frame the decision is to map medium + temperature + life target to a grade family.

Table 1 – Quick selection cues

Service cue	Stainless TP family (typical)	Ferritic T family (typical)
Chlorides / wet–dry cycles / cleanliness	TP316L/316H; TP304/304H if low chlorides	Not preferred
Sensitization control at high temp	TP321/321H (Ti-stabilized); TP347/347H	-
Highest creep margin (dry, very hot gas)	TP347H/321H in select cases	T91 > T22 > T11 ≈ T9
Lowest risk of pitting in seawater service	TP316L (Mo-bearing)	-
Cost-efficiency at moderate hot service	TP304/304H	T11/T22 (when corrosion is mild)

Project specs always prevail; the table is a shortcut for early screening.

Stainless Grades at a Glance (TP Series)

Table 2 – Common stainless tubing choices under A213

Grade	Core chemistry highlights	What it's good at	Typical applications
TP304 / 304H	~18Cr-8Ni (H = high-temp carbon range)	Broad utility; clean surfaces; good fabricability	Condenser/heat-exchanger bundles, heaters
TP316L / 316H	Adds ~2–3% Mo; L = low C; H = high-temp	Better pitting/crevice resistance vs 304/304H	Seawater-adjacent cooling, chloride media
TP321 / 321H	Ti-stabilized	Sensitization control at elevated temperature	Superheater coils, high-temp exchangers
TP347 / 347H	Nb-stabilized	Similar to 321; stronger stabilization window	Furnace/boiler coils with thermal cyclingH-grades target elevated-temperature strength; L-grades target weldability and resistance to sensitization in aqueous service.

Ferritic Alloy "T" Grades in Context

Table 3 – Where T9, T11, T22, T91 typically fit

Grade	Concept (nominal)	Strength outlook (hot)	Typical role
T11	~1.25Cr-0.5Mo	Baseline	Moderate-temp boiler/heat-exchanger tubes
T22	~2.25Cr-1Mo	↑ vs T11	Hotter banks; cost-efficient creep margin
T9	~9Cr-1Mo (ferritic)	Similar band to T22	Select hot services and transition zones
T91	9Cr-1Mo-V-Nb (tempered martensite)	Highest of group	Very hot superheater/reheater sections

Chemistry Snapshots (Reference Ranges)

Table 4 – Austenitic stainless (TP series, wt.%)

Grade	C (L/H)	Cr	Ni	Mo	Stabilizer
TP304/304H	≤0.035 / 0.04–0.10	~18–20	~8–11	-	-
TP316L/316H	≤0.035 / 0.04–0.10	~16–18	~10–14	~2.0–3.0	-
TP321/321H	≤0.035 / 0.04–0.10	~17–19	~9–13	-	Ti
TP347/347H	≤0.035 / 0.04–0.10	~17–19	~9–13	-	Nb/Ta

Table 5 – Ferritic alloy (T series, wt.%)

Grade	C (typ.)	Cr (typ.)	Mo (typ.)	V/Nb/N (when applicable)
T11	≤0.12	~1.0–1.5	~0.44–0.65	-
T22	≤0.15	~1.9–2.6	~0.87–1.13	-
T9	≤0.15	~8–10	~0.9–1.1	-
T91	0.08–0.12	~8–9.5	~0.85–1.05	V, Nb, N small additions

Consult the latest ASTM A213/SA213 for governing limits and product analysis tolerances.

Mechanical & High-Temperature Benchmarks (Minimums at Room Temp)

Table 6 – Indicative minimums (check current code/standard)

Family / Grade	Tensile min	Yield min	Elongation min
Austenitic (e.g., TP304/316L)	≈ 515 MPa (75 ksi)	≈ 205 MPa (30 ksi)	≈ 35%
TP321/347 (H grades)	≈ 515 MPa	≈ 205 MPa	≈ 30–35%
T11/T22	≈ 415 MPa	≈ 205 MPa	≈ 20%
T91	≈ 585 MPa	≈ 415 MPa	≈ 20%

Manufacturing Notes - Seamless Only (A213 Scope)

Routes: hot-finished then cold-finished to size; stainless often solution-annealed and pickled/passivated for a clean ID.
Heat treatment: austenitic stainless-solution anneal + rapid cool; T91-normalize & temper (per spec); T11/T22-normalizing or subcritical treatments as specified.
Surface & cleanliness: stainless tubing routinely supplied with low-roughness ID for efficient heat transfer and clean-in-place routines.
Geometry: tight OD/thickness tolerances and straightness help bundle assembly and tube-to-tubesheet welding.
U-bends: commonly supplied for stainless heat-exchanger bundles with controlled bend radii and stress relief when required.

Testing & Inspection You Should Specify

Table 7 – Common requirements under A213 (project-dependent)

Item	Stainless TP series	T-series (T11/T22/T91)
Hydrostatic or NDE electric test	Mandatory (one or the other)	Mandatory (one or the other)
Eddy current / ultrasonic (NDE)	Often specified for 100% coverage	Often specified for 100% coverage
Flattening / flare / flange tests	As specified by A213	As specified by A213
Grain size (austenitic)	Required where applicable	-
Intergranular corrosion test (IGC)	By order (e.g., ASTM A262 methods)	-
Hardness control	Usually informational	Critical for T91 per procedure
PMI & documentation	PMI on bundles; full MTC package	PMI on bundles; full MTC package

Dimensional Availability (Octal Pipe Reference)

Table 8 – Typical supply envelope (project-specific)

Parameter	Stainless TP series	T-series (T11/T22/T91)
Outside diameter	~12.7–114.3 mm (½ in–4½ in)	Similar range
Wall thickness	~1.24–12.7 mm (per schedule/draw)	~2–16 mm (heavy walls avail.)
Lengths	Up to 12 m typical; cut-to-length	Up to 12 m typical
Finishing	Pickled/passivated, polished on req	Normalized/tempered finish
Tube ends	Plain ends; tube-to-tubesheet prep	Plain ends; beveled if req

Ordering Checklist (What to Put in the Datasheet)

Grade and condition: TP304/316L/321/347 (L/H as needed) or T11/T22/T91 with required heat treatment.
Dimensions: OD, wall, cut lengths; U-bend radii and leg tolerance if applicable.
Heat treatment & surface: solution anneal + pickling/passivation (stainless); normalize/temper (as applicable).
NDE plan: hydrostatic or electric test; 100% eddy current/UT if required; acceptance criteria.
Corrosion control: IGC test for stabilized grades if specified; chloride limits; cleaning protocol.
Documentation: MTC per EN 10204 (e.g., 3.1), traceability, packing, marking.
Third-party: witnessing/inspection available on request (BV, SGS, etc.).

FAQ

Q1: How do I choose between stainless TP grades and chrome-moly T grades under ASTM A213/SA213?
A1: Use TP grades for wet/dirty or chloride service and cleanliness needs; use T grades when dry high-temperature creep strength is the main driver.

Q2: What's the practical difference between SA213 T11, T22, and T91 tubing?
A2: T11 is the baseline for moderate temperature, T22 adds creep margin for hotter sections, and T91 is used for the highest-temperature superheater/reheater duty.

Q3: What inspections and documents should I request for ASTM A213/SA213 tubing?
A3: Ask for hydrotest or NDE electric test, 100% eddy current/UT if required, PMI, and a complete EN 10204 3.1 MTC with heat-treatment records.

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