TA2 Seamless Titanium Tube B338 for Heat Exchangers

Опубликовано Engineering Team, Shaanxi Qianyi Tuoda Technology Co., Ltd от 2026-11-12

TA2 seamless titanium tube to ASTM B338 is stocked in OD 6–114 mm with cut-to-length service, but "in stock" does not mean "ready for the tube sheet". Three specifications decide whether a retubing job lasts fifteen years or fails in eight months: minimum wall thickness (B338 defaults to average wall), the seamless or welded route, and the NDT level beyond the standard's default. On a typical 25.4 x 0.7 mm order, an average-wall delivery can legally contain a 0.56 mm thin point, and that thin point is exactly where an expanded joint or a turbulent inlet will find it first.

This article is for buyers who have already settled on TA2 / Gr2 heat exchanger tube and need to write a purchase order that survives contact with a real condenser. It covers the scope of ASTM B338, the seamless-versus-welded decision, the wall-thickness basis, the tube-to-tubesheet joint, NDT upgrades, the difference between B338 and B861/B862 pressure pipe, the service limits of TA2, the economics of retubing, and the eight fields that belong on the RFQ. If you are still choosing between grades, our Gr2 vs Gr7 seawater selection guide and the titanium tube buyer's guide are the better starting points.

Standards	ASTM B338 (heat exchanger and condenser tube); B861/B862 (seamless/welded pressure pipe); ASME SB338
Grades	TA2 / Gr2 / UNS R50400 baseline; Gr7, Gr12, Gr16 for hot crevice service
Service	Chemical heat exchangers, surface condensers, reboilers, MSF/MED desalination, cooling water
Core distinction	B338 is a heat exchanger tube standard with average-wall default. Minimum wall, route and NDT must be added by the buyer.

The "In Stock" Trap: 34 Leaking Tubes in Eight Months

A refinery surface condenser on a coastal site in the Middle East was retubed in 2021 with approximately 12,000 TA2 titanium tubes. The purchase order read "ASTM B338 Gr2 25.4 x 0.7 mm, 6 m, seawater service". The tubes arrived on time, the certificates were valid, and the bundle was back in service within the planned shutdown window. Eight months later, 34 tubes had leaked and the unit was opened again.

The investigation found three things, all of them permitted by the PO as written. The tube mill had supplied welded tube. ASTM B338 permits both seamless and welded product, and a PO that does not name the route gets whichever the mill has available. The internal weld bead on those tubes had not been fully planished, leaving a ridge of roughly 0.1–0.15 mm around the full circumference. That ridge tripped the boundary layer at the inlet of every tube and created a persistent turbulence ring. Third, the wall was supplied to an average-wall basis, so while the mean measured 0.7 mm, the thinnest points were around 0.56 mm. Turbulence plus a thin wall plus seawater is a short path to erosion-corrosion pinholes, and the first failures appeared at the inlet end, exactly where the flow disturbance was highest.

The rule: a tube that is in stock is a logistics fact. A tube that is ready for a tube sheet is an engineering fact. The gap between them is three PO lines — minimum wall, manufacturing route, and NDT level.

Nothing was counterfeit and nothing was out of standard. That is what makes this failure mode expensive: there is nobody to blame, and the retube has to be done twice. We have documented the same pattern across several real bundles in our heat exchanger tube bundle failure cases, and the weld-protection side in the TA2 tube early-failure analysis.

What ASTM B338 Actually Covers

ASTM B338 is the standard specification for seamless and welded titanium and titanium alloy tubes for condensers and heat exchangers. It defines the permitted grades, chemical composition, tensile properties, flattening and flaring requirements, dimensional tolerances, hydrostatic or non-destructive electric testing, and the surface condition. It is written for the tube as a mill product, and it assumes the buyer will select from the options inside the standard rather than simply naming it.

The most consequential option is the wall basis. B338 tube is conventionally supplied to a nominal or average wall with a percentage tolerance, which means local thin points below the nominal are acceptable as long as the average and the tolerance band are met. By contrast, pressure pipe standards such as B861 and B862 work on a minimum-wall basis. A buyer who writes "0.7 mm wall" on a B338 order has purchased an average; a buyer who writes "0.7 mm minimum wall, no minus tolerance at any point, UT survey supplied" has purchased a floor. Those are different products at nearly the same price, and the second one is what a high-velocity or cyclic-service exchanger usually needs.

The second option is the manufacturing route. Seamless tube is produced by extrusion or pilgering from a billet and has no weld. Welded tube is formed from strip, autogenously welded and then cold worked and annealed; in a well-run mill the weld is fully recrystallised and the internal bead is planished smooth. Both are legitimate B338 products. Good welded tube performs well in clean, steady, low-to-moderate temperature service and costs meaningfully less. It is not a lower-grade material; it is a different process with different sensitivities, which is the point most purchasing arguments get wrong.

The third option is NDT. B338 requires a non-destructive electric test — commonly eddy current — or a hydrostatic test, at the standard's default sensitivity. That default is a floor designed to catch gross discontinuities. It is not calibrated to find the small near-surface inclusions, the incomplete weld penetration or the localised wall thinning that matter in a twenty-year seawater condenser. Upgrading the test is a purchase decision, not a mill favour.

Seamless vs Welded: A Service Decision, Not a Quality Ranking

Choose seamless when the service involves pressure cycling, vibration, mechanical expansion into a tube sheet, high-velocity two-phase flow, or any condition where a longitudinal weld line is a preferential weakness. Choose welded and planished tube when the fluid is clean, the temperature is moderate and the duty is steady. The premium for seamless commonly falls in the 25–60% range depending on OD, wall and quantity; that is an approximate planning figure, not a quotation, and it varies with mill loading.

Condition	Preferred route	Why
Roller-expanded tube-to-tubesheet joints	Seamless	Radial expansion strain has no weld line to open
Vibration, flow-induced fretting, cyclic pressure	Seamless	Fatigue initiates preferentially at weld or bead geometry
Clean cooling water, steady duty, below roughly 60 C	Welded, internal bead planished	Lowest total cost with no meaningful service penalty
Seawater above 60 C, chlorides, sour service	Seamless, upgraded NDT, consider Gr7 at the joint	Crevice and erosion margins matter more than tube price

The bead is the detail that separates good welded tube from bad welded tube. A properly planished internal weld is nearly indistinguishable from the parent wall; an unplanished ridge of even 0.1 mm creates a permanent turbulence ring and a site for deposit accumulation. If you accept welded tube, write "internal weld bead planished flush, maximum residual height 0.05 mm" into the PO and ask for a borescope image from the first lot. Our Gr2 seamless tube stock page lists the OD range and the inspection package we supply as standard.

The 0.56 mm Problem: Why Average Wall Is Not Enough

On a 25.4 x 0.7 mm tube supplied to a ±10% or ±12.5% wall tolerance on an average basis, a measured thin point of roughly 0.56–0.63 mm is entirely normal. That is a 10–20% reduction in wall at the exact location where the designer had the least margin. In a condenser the highest risk is not usually the middle of the tube; it is the inlet end, the expanded joint, the support plate contact line and any area under a deposit. All four are places where local wall loss and local flow disturbance coincide.

Writing a minimum-wall clause changes the mill's inspection behaviour, not just the number on the certificate. It requires the mill to measure and reject, or to select tube from a tighter part of the production distribution. On a small retubing order that may add a little lead time. On a 12,000-tube order it is the difference between a bundle that lasts and a bundle that is opened in eight months.

There is a second dimensional field that is routinely omitted: length and end condition. Retubing orders need exact length because tubes must sit flush with, or protrude a defined amount from, the tube sheet face. Ask for square, deburred, oxide-free ends and confirm whether the ends will be expanded, seal-welded or both. A tube that is 3 mm long at one end can be trimmed on site; a tube that is 3 mm short cannot be recovered. Our seamless B338 tube notes cover the dimensional classes we normally ship.

The Tube Sheet Joint Nobody Specifies

The tube-to-tubesheet joint is where most titanium condensers actually fail, and it is almost never described in the tube PO. The joint is a crevice by construction. Oxygen inside the annular gap is consumed, the local chemistry acidifies, and above roughly 60–70 C in chloride service the passive film on TA2 can break down in that gap even while the open tube surface remains perfectly sound.

Three design responses are available. First, eliminate or minimise the crevice by full-depth expansion plus seal welding, or by welding the tube to the tube sheet face. Second, use a graded approach: TA2 for 90–95% of the tube length and a more crevice-resistant grade such as Gr7/TA9 for a short tube-sheet sleeve or for the tube sheet cladding itself. Third, control the water chemistry and the temperature so the crevice never reaches the critical range. The second option is often the most economical because it puts the palladium-bearing alloy only in the 5–10% of the surface that needs it; the incremental material cost becomes a fraction of a full Gr7 bundle. That zoning logic is set out in more detail in our Gr2 vs Gr7 seawater guide.

Do not overlook the tube sheet material. A carbon steel tube sheet paired with titanium tubes is a galvanic couple with a large cathode and a small anode, made worse by any stray current or cathodic protection system. Titanium is the cathode in most couples, so the risk is hydrogen pickup and embrittlement on the titanium side plus accelerated corrosion of the steel. Clad tube sheets, insulated joints and controlled CP potentials are all standard solutions, but they have to be designed, not assumed.

NDT Is a Floor, Not a Ceiling

The default B338 electric test is intended to reject gross defects. For clean cooling water at ambient temperature, that is often sufficient. For seawater above 60 C, chloride-bearing process streams, cyclic pressure, or a bundle that will be difficult to access for repair, specify an upgrade: eddy current to an agreed calibration standard with defined notch size and orientation, plus a hydrostatic test at a stated pressure, plus ultrasonic wall-thickness mapping on a defined sample or on 100% of tubes for minimum-wall deliveries. For welded tube, add a weld-line-specific examination.

Ask for the calibration record, not just a pass statement. An eddy current report that does not say what reference standard was used, what notch depth, and what scanning speed tells you very little. Ask also how rejects are handled and whether the reported results are for the tubes actually allocated to your order. On export orders, a third-party witnessing requirement should be stated at enquiry so it can be scheduled.

PMI deserves its own line. TA2, Gr7, Gr12 and Gr16 tube look identical, weigh the same to within a fraction, and are indistinguishable after installation. On any order containing a palladium- or ruthenium-bearing grade, require positive material identification on every bundle, not a sample. A single Gr2 bundle mixed into a Gr7 retube is a failure that will not be discovered until the crevice corrodes. Our B338 heat exchanger tube overview lists the documentation package that accompanies these orders.

B338 vs B861 vs B862: Three Standards, Three Jobs

Confusing these three is the single most common cause of a technically nonconforming tube delivery. B338 covers heat exchanger and condenser tubes, where the design driver is heat transfer, thin walls, tight OD tolerance for tube sheet fit, and large quantities of relatively small-diameter tube. B861 covers seamless titanium pipe for pressure service and general corrosive service; B862 covers the welded equivalent. Pipe standards work in nominal pipe sizes and schedules, with a minimum-wall basis and more demanding pressure-related testing.

A buyer who orders B338 tube for a pressurised process line has purchased a product designed for a different job. A buyer who orders B861 pipe for a condenser has purchased something too thick, too expensive and dimensionally wrong for the tube sheet holes. Both happen, usually because a purchasing system has one field called "titanium tube/pipe" and somebody typed the wrong standard. Put the application on the PO — "for shell-and-tube heat exchanger, expanded and seal-welded joints" — so the supplier can challenge a mismatch before it ships.

Where TA2 DOES Fail: Read This Before You Approve the Grade

Hot chloride crevices at the tube sheet

Described above: geometry-driven crevice corrosion above roughly 60–70 C at expanded joints, under deposits and at support plate contact lines. Fix the joint design or zone the grade. Do not solve it by buying thicker tube.

Reducing acids and hydrogen uptake

In hot concentrated HCl or H2SO4, or in systems with cathodic protection and galvanic coupling to steel, TA2 can absorb hydrogen and form brittle hydrides. Once hydride platelets precipitate, ductility is lost and vibration or a pressure cycle can crack the tube. If the process side is a reducing acid, TA2 is the wrong starting point; see the grade discussion in our chlor-alkali grade comparison.

Deposit-covered and stagnant surfaces

A tube that is clean and flowing is a different material system from a tube under a layer of silt, biofilm or scale. Deposits create a crevice, trap heat and can support under-deposit pitting. In seawater service, specify a minimum velocity and a cleaning regime, not only a corrosion-resistant alloy. Biofouling control is part of the material specification in practice, even if it does not appear on the MTR.

High inlet velocity and two-phase flow

Titanium is resistant to erosion in clean single-phase seawater at reasonable velocities, but inlet-end turbulence, entrained sand, flashing and two-phase flow remove the passive film faster than it can reform. Above a project-specific threshold velocity the result is a polished, thinned inlet end followed by perforation. This is where the 0.56 mm thin point from an average-wall delivery becomes fatal. Consider inlet ferrules, flow distributors and a minimum-wall specification together.

Dry chlorine, fluoride and anhydrous organics

As with plate, fluoride attacks the oxide film directly, dry chlorine and water-free organics prevent repassivation, and titanium can react violently in genuinely dry chlorine. These are absolute exclusions, not grade-selection questions. Check the upset cases and the cleaning chemicals, not only normal operation.

Do not retube a hot seawater condenser with average-wall welded tube and default NDT, and do not assume that a material certificate covers the tube-to-tubesheet crevice. Those two assumptions account for most early titanium bundle failures we are asked to investigate.

Cost Economics: What a Second Retube Actually Costs

Tube is rarely the dominant cost in a retubing project. The shutdown window, the removal of the old bundle, tube sheet preparation, expansion and seal welding, hydrotest, and lost production are. On a large condenser, the tube supply might be a modest fraction of the total project cost, while an unplanned second outage can be several times the entire first bill. That asymmetry is the whole argument for paying a little more for minimum wall, upgraded NDT and the correct route.

Consider the arithmetic on a 12,000-tube bundle. A seamless upgrade at an approximate 25–60% premium on the tube line raises the tube cost by a fraction of the project total. An upgraded eddy current and hydrotest package adds a small per-tube charge. A minimum-wall clause may add a little lead time. Together these are typically far below the cost of reopening the exchanger, even before lost throughput is counted. This is why experienced operators treat the tube PO as an insurance document rather than a commodity purchase.

The one place where the premium is not justified is clean, cool, steady cooling water in an accessible exchanger. There, welded planished tube with standard NDT is a rational choice and the saving is real. The error is not buying welded tube; it is buying welded tube for a hot seawater cyclic duty because it was in stock. For current base material pricing see the titanium price index and our latest daily price report; all multiples above are approximate planning figures.

Seven Procurement Mistakes That Show Up at Retube

1. Not naming the route. B338 allows both. Silence means the mill decides.
2. Buying average wall. State minimum wall, the tolerance basis and the survey method.
3. Accepting default NDT for a severe service. Upgrade calibration, add hydrotest and UT for critical bundles.
4. Omitting the joint description. Expanded, seal-welded, or both; tube sheet material and cladding; crevice strategy.
5. Mixing up B338 and B861/B862. Heat exchanger tube and pressure pipe are different products.
6. No PMI on alloyed grades. Gr2, Gr7 and Gr12 are visually identical after installation.
7. Ignoring length and end condition. Short tubes cannot be recovered; deburred oxide-free ends are a line on the PO.

Stock, Cut-to-Length and Lead Time

We hold TA2 seamless tube in the common heat exchanger diameters, with OD 6–114 mm as the routine range and a range of wall thicknesses; the exact sizes and quantities are published on our inventory page and in the Baoji stock and dispatch note. Please confirm live availability when you enquire, because common diameters move quickly during retubing season.

Cut-to-length is done to your tube sheet drawing, including square deburred ends and any required protrusion allowance. Small-batch orders are normal: a 40-tube repair bundle for a single exchanger is as valid as a full 12,000-tube retube. This is where a stock-and-cut supplier has a structural advantage over a mill, whose minimum order quantity may be several tonnes. We can also supply the short Gr7 or Gr12 sleeves used in a zoned bundle, and the matching pipe fittings for the associated piping.

Lead time depends on whether the OD and wall are in stock, whether the route is seamless, and what NDT and third-party witnessing are required. Rather than publish a number that may be wrong next month, we quote a firm date with the offer. Our inquiry response procedure lists the inputs we need to respond within 24 hours. For export orders, specify at enquiry the certificate language, any third-party inspection, and the packing: long thin tubes need fully supported crates with end caps, because a dented end is a rejected tube.

Supplier Verification: What to Ask Before the PO

Ask which heat each bundle comes from and request the chemistry and mechanical results before shipment. Ask for the wall-thickness survey method and the actual minimum measured, not the nominal. Ask whether the tube is seamless or welded and, if welded, what internal bead height is guaranteed and how it is measured. Ask which eddy current calibration standard and notch size will be used, and whether a hydrostatic test is included. Ask how each bundle carries its heat number and whether PMI is performed after cutting. Ask what happens to out-of-specification tubes.

Then ask the question that separates a stockholder from a mill partner: can you supply the same grade in a short sleeve for the tube sheet zone and in plate for the tube sheet itself? A supplier who can assemble the whole zoned material package understands the failure mode you are trying to prevent. Our certification page and materials overview set out the document set and the grades available for that package.

Frequently Asked Questions

Q1: Does ASTM B338 allow welded tube?

Yes. B338 covers both seamless and welded titanium condenser and heat exchanger tubes. If your service needs seamless, you must say so on the purchase order — naming the standard alone does not select the route. For welded tube, also specify that the internal weld bead must be planished flush, with a maximum residual height.

Q2: Is average wall or minimum wall the default?

Average or nominal wall with a percentage tolerance is the conventional B338 basis, which means local thin points below nominal are acceptable. If the design depends on a guaranteed wall — high velocity, cyclic duty, expanded joints — specify "minimum wall, no minus tolerance at any point" and require a thickness survey report. Pressure pipe standards B861/B862 work on a minimum-wall basis by contrast.

Q3: When should I upgrade eddy current testing?

Upgrade for seawater above roughly 60 C, chloride-bearing or sour streams, cyclic pressure, vibration, or any bundle that is expensive to access for repair. Specify the calibration standard, notch size and orientation, add a hydrostatic test, and consider 100% ultrasonic wall mapping for minimum-wall orders. For welded tube, add a weld-line-specific examination.

Q4: Can B338 tube be used as pressure pipe?

No, not without an engineering review. B338 is written for heat exchanger and condenser tube: thin walls, tight OD tolerance for tube sheet fit, different wall basis and different test regime. Pressurised process lines should use B861 (seamless) or B862 (welded) pipe in nominal pipe sizes and schedules. State the application on the PO so a mismatch is caught before shipment.

Q5: What causes early leaks at expanded joints?

Usually a combination of crevice corrosion in the tube-to-tubesheet gap at elevated chloride temperature, local wall thinning from an average-wall delivery, residual stress from expansion, and inlet turbulence. Full-depth expansion plus seal welding, a zoned Gr7 sleeve at the tube sheet, and a minimum-wall clause address the three controllable parts.

Q6: Do you supply cut-to-length tube for retubing?

Yes. We cut to the tube sheet drawing with square deburred ends and the required protrusion allowance, and we accept small-batch and single-bundle repair orders. Send the drawing, quantity, grade, route, wall basis and inspection requirements, and we will confirm the size against live stock with the quotation.

Q7: What is the lead time for stocked OD?

Stocked diameters with standard inspection are the quickest; seamless upgrades, minimum-wall selection, dual certification and third-party witnessing add time. We quote a firm date with the offer rather than a generic estimate. Check current availability on the inventory page and send the full specification to the quotation desk.

Choose TA2 Seamless B338 if / Choose Something Else if

Choose TA2 seamless B338 tube if you are retubing a chemical heat exchanger, condenser or reboiler; the medium is cooling water, seawater below roughly 60 C or an oxidising / mildly reducing process stream; you can specify minimum wall, seamless route and upgraded NDT; and the tube sheet crevice is controlled by joint design or by a zoned Gr7 sleeve. It is also the right choice for small-batch retubing where mill minimum quantities are impractical.

Choose something else if the process side is a hot concentrated reducing acid or contains fluoride (consider a different alloy system or zirconium); if hot chloride crevices cannot be designed out (zone Gr7 or Gr12 at the joint, or clad the tube sheet); if the line is a pressurised process pipe rather than an exchanger (use B861/B862); or if the duty is clean cool steady water and an accessible exchanger makes welded planished tube a rational saving.

Summary: The Eight Fields That Belong on the RFQ

1. Standard and application: ASTM B338 / ASME SB338, "for shell-and-tube heat exchanger", with the joint type named.
2. Grade and UNS: TA2 / Gr2 / UNS R50400; add Gr7 or Gr12 sleeves if the joint is zoned.
3. Dimensions: OD, minimum wall with no minus tolerance, exact cut length, end condition and protrusion allowance.
4. Route: seamless, or welded with internal bead planished flush and a stated maximum residual height.
5. NDT: eddy current calibration standard and notch, hydrostatic test, UT wall mapping, and weld-line examination if welded.
6. Joint strategy: full-depth expansion and/or seal weld, tube sheet material and cladding, crevice control, galvanic isolation.
7. Documentation: MTR with heat number, thickness survey, NDT records, PMI on every bundle, third-party witnessing if required.
8. Commercial terms: quantity (small batches accepted), packing with end caps and full support, target date, incoterms.

Send those eight items with your tube sheet drawing and process conditions — chemistry, temperature, velocity, upset cases and cleaning regime — to our quotation desk. If the conditions sit near any of the limits above, tell us; we would rather propose a zoned bundle or a different grade than ship tube that has to be pulled in eight months. Related reading: the titanium tube category, the tube buyer's guide and the full product range.