Titanium Tube 25 mm, ASTM B338 — Heat-Exchanger Grade Tube Cut to Length

Published by Engineering Team, Shaanxi Qianyi Tuoda Technology Co., Ltd on 2026-11-04

Titanium heat exchanger tube · 25 mm OD · ASTM B338 · stock

The 25 mm outside-diameter titanium tube to ASTM B338 is the standard size for shell-and-tube heat exchangers in seawater, desalination and acid duty — the metric match to the 1 in tube. SXQYTD stocks Grade 2 / Grade 7 / Grade 12 tube in 25 mm OD, cut to length, eddy-current tested, with MTC and PMI. Below is the procurement detail that decides grade, wall and length before you issue a PO.

Material	Gr2 / Gr7 / Gr12 (R50400 / R52400 / R53400)	Principle	Thin-wall tube, chloride-proof heat transfer
Size & stock	25 mm OD, wall 0.5–2.0 mm; in stock	Industry	Desalination, power, chemical, marine
Standard	ASTM B338 / ASME SB-338	Lead time	1–3 days stock; 3–5 days cut / U-bend

1. What this tube is — by grade and by standard

By grade, the heat-exchanger grades are Gr2 (commercial purity, the default), Gr7 (Gr2 + 0.15 % Pd) and Gr12 (Gr2 + Mo/Ni) for hotter or crevice-prone chloride. By standard, ASTM B338 is the spec written for condenser and heat-exchanger tubes — thin wall, close tolerance, 100 % non-destructive tested. Do not confuse it with B861 (seamless pipe for pressure service) or B862 (welded pipe); those are thicker-wall and not the right call for a tube bundle. The 25 mm OD is the metric standard exchanger size, matching the 1 in (25.4 mm) tube used across MSF/MED desalination and surface condensers.

2. Why titanium tube — material vs. medium vs. corrosion

Titanium's TiO₂ film survives chlorides that destroy copper-nickel and 316L tubes. The selection logic:

Medium	Recommended grade	Why
Seawater, desalination	Gr2	Ambient chloride; 20–30 yr life.
Hot chloride (>70°C)	Gr7 / Gr12	Resists crevice attack at temperature.
Acid condenser	Gr2 / Gr7	Oxidizing acid; Gr7 if reducing.
High-purity water	Gr1 / Gr2	Low metal pick-up.

Three limits that decide the design: (1) titanium's thermal conductivity is only ~17 W/m·K — about half of steel — so we recover heat transfer with a 0.5 mm wall and zero corrosion allowance, not by thickening; (2) the tube-to-tubesheet joint is the #1 leak source, so every tube is expanded and then GTAW-welded, never just rolled; and (3) above ~315°C titanium oxidizes and embrittles, so it is a low/medium-temperature exchanger tube. We design the wall and joint to these limits from the start.

3. Technical standards we supply to

• Tube spec: ASTM B338 / ASME SB-338, seamless or welded as ordered; MTC EN 10204 3.1.
• Distinction: B338 = exchanger/condenser tube (thin wall); B861 = seamless pressure pipe; B862 = welded pipe — do not substitute on a tube bundle.
• Chemistry (B338 Gr2): Fe ≤ 0.30 %, O ≤ 0.25 %, C ≤ 0.10 %, N ≤ 0.03 %, H ≤ 0.015 %.
• Mechanical (annealed): tensile ≥ 345 MPa, yield ≥ 275 MPa, elongation ≥ 20 %.
• Test: 100 % eddy-current (or hydrostatic) per B338; PMI on the heat.

4. Manufacturing flow — from billet to your length

1) Titanium sponge + VAR melt → 2) Billet → 3) Extrusion / piercing → 4) Cold drawing or cold pilgering to 25 mm OD → 5) Vacuum anneal → 6) Pickling / descaling → 7) Straightening → 8) Cut to length → 9) Eddy-current / hydrostatic test → 10) PMI and export packing. Seamless is preferred for exchanger bundles; the thin 0.5–0.7 mm wall is reached by cold pilgering, not by machining.

5. Key performance

Item	Control value	Note
Outside diameter	25 mm (± 0.10 mm typical)	Metric 1 in equivalent.
Wall thickness	0.5–2.0 mm	0.5–0.7 for transfer, 1.0–2.0 for erosion.
Straightness	≤ 1 mm / m	Needed for tube-pulling.
NDT	100 % eddy current / hydrostatic	Per B338.
Density	4.51 g/cm³	Light bundle, easy handling.

6. Application industries

Industry	Medium	Why titanium tube
Desalination (MSF/MED)	Seawater, brine	Cu-Ni tubed units fail; Ti lasts decades.
Power condensers	Cooling water	No fouling, no plug-in loss.
Chemical HX	Acid, chloride	Gr7/Gr12 for hot duty.
Marine	Seawater cooling	Zero crevice failure.
Pharma / pure water	WFI, clean fluid	Gr1/Gr2, no ion pick-up.

7. Selection guide

By medium: seawater / desalination → Gr2; hot chloride above ~70°C or crevice-prone → Gr7/Gr12; high-purity → Gr1. By wall: 0.5–0.7 mm maximizes heat transfer (thin wall, no corrosion allowance); 1.0–2.0 mm for erosive slurry or mechanical load. By standard: for a tube bundle always specify B338, not B861/B862. Send medium, temperature, length, wall and quantity; we confirm grade and cut in one reply.

8. Customizable items & accessories

• Cut to length; both ends square-cut or chamfered for tube-sheet welding.
• Wall thickness from 0.5 to 2.0 mm; seamless or welded as required.
• U-bending (U-tube) service with stress relief and radius control.
• Surface: pickled or bright-annealed; PMI and eddy-current report.
• Small quantity / zero-cut from stock; third-party inspection (SGS / TUV).

9. Lead time, test reports & warranty

Item	Commitment
Lead time	1–3 days from stock; 3–5 days cut / U-bend.
Test reports	MTC 3.1, eddy current / hydrostatic, PMI, dimensional.
Warranty	12 months against material and workmanship defects from shipment.

10. FAQ

Is ASTM B338 the same as B861?

No. B338 is written for condenser and heat-exchanger tubes — thin wall, close tolerance, 100 % NDT. B861 is seamless pipe for pressure service and B862 is welded pipe. For a tube bundle always specify B338; using a pipe spec will give you the wrong wall tolerance and test basis.

What does 25 mm mean in inches?

25 mm OD is the metric standard exchanger size, matching the 1 in (25.4 mm) tube used in MSF/MED desalination and surface condensers. If your drawing is in inches, 25.4 mm is the direct equivalent; we can supply either.

Grade 2 or Grade 7 for seawater?

Grade 2 is correct for ambient seawater and most desalination. Use Grade 7 or Grade 12 only when the service is above ~70°C or has tight crevices where Gr2 could crevice-corrode. Send the temperature and we confirm the grade.