How Is Each Tube Made?
| Aspect | Seamless Tube | Welded Tube |
|---|---|---|
| Starting Material | Solid titanium billet | Titanium strip/coil |
| Process | Piercing, extrusion, rolling | Roll forming + welding |
| Seam | None (one-piece construction) | Longitudinal weld seam |
| Minimum Wall Thickness | Limited by piercing process | Can be very thin |
| Maximum Diameter | Limited by mill capacity | Virtually unlimited |
| Typical OD Range | 3.18 - 114.3 mm | 6.0 - 219 mm+ |
Which One Has Tighter Tolerances?
Welded tube typically holds tighter dimensional tolerances than seamless tube, because the starting strip can be rolled to precise thickness before forming.
| Tolerance | Seamless Tube | Welded Tube | Why |
|---|---|---|---|
| OD Tolerance | ±0.08 - 0.15 mm | ±0.05 - 0.10 mm | Welded starts with precise strip. |
| Wall Thickness Tolerance | ±10-12% | ±8-10% | Strip thickness is tightly controlled. |
| Roundness (Ovality) | Up to 2% of OD | ≤1.5% of OD | Welded is more consistent. |
| Straightness | ≤1.5 mm/m | ≤1.5 mm/m | Comparable. |
For heat exchanger tube bundles, tight OD and wall tolerances matter. They ensure proper fit-up in the tube sheet and consistent expansion. Welded tube's tighter tolerances are actually an advantage here.
Which One Handles Higher Pressure?
Seamless tube has higher burst pressure ratings for the same wall thickness, because it has no weld seam that could be a weak point. But for most heat exchanger pressures, both are more than adequate.
This is the one area where seamless has a clear technical advantage. Without a weld seam, seamless tube has uniform properties in all directions.
| Property | Seamless Tube | Welded Tube |
|---|---|---|
| Burst Pressure | Higher (uniform wall) | Slightly lower (weld factor) |
| Weld Factor | 1.0 (no weld) | 0.85 - 0.95 (ASME design factor) |
| Typical Max Pressure | Higher | Slightly lower |
| Suitability for High Pressure | Excellent | Good |
Which One Costs More?
Seamless tube typically costs 15-30% more than welded tube for the same size and grade. The price difference comes from the manufacturing process - seamless production is slower and has higher scrap rates.
| Cost Factor | Seamless Tube | Welded Tube |
|---|---|---|
| Base Material | Billet (more expensive) | Strip/coil (less expensive) |
| Production Speed | Slower | Faster |
| Scrap Rate | Higher | Lower |
| Tooling Cost | Higher | Lower |
| Energy Consumption | Higher | Lower |
| Typical Price | 15-30% higher | Baseline |
On a typical heat exchanger bundle with 1,000 tubes, upgrading from welded to seamless can add 15-30% to the tube cost. For a large project, that difference can be substantial.
Which One Ships Faster?
Welded tube generally ships faster than seamless tube, because the starting material (titanium strip) is more readily available and the production process is faster.
| Availability Factor | Seamless Tube | Welded Tube |
|---|---|---|
| Raw Material Availability | Limited (billet supply) | Better (strip supply) |
| Production Lead Time | 4-8 weeks | 2-4 weeks |
| Stock Availability | Limited for standard sizes | Better for standard sizes |
| Minimum Order Quantity | Higher | Lower |
For urgent projects, welded tube is often the only practical choice. Standard sizes of welded Grade 2 tube are frequently available from stock, while seamless typically requires a mill run.
Seamless or Welded
| Operating Condition | Recommended Type | Why |
|---|---|---|
| Standard heat exchanger, < 5 MPa | Welded | Lower cost, tighter tolerances, readily available. |
| Power plant condenser | Welded | Industry standard for most condenser applications. |
| Seawater cooling system | Welded | Fully corrosion-resistant. No need for seamless. |
| Small diameter (< 6 mm OD) | Seamless | Welded is not available in very small sizes. |
| Large diameter (> 114 mm OD) | Welded | Seamless is not practical at large sizes. |
| High pressure (> 10 MPa) | Seamless | No weld seam = higher burst rating. |
| Very thin wall (< 0.5 mm) | Welded | Seamless cannot reliably make very thin walls. |
| High-integrity pressure vessel | Seamless | Some codes require seamless for certain services. |
| Tight budget | Welded | 15-30% cheaper. |
| Tight schedule | Welded | Faster production and better stock availability. |
Welded tube is the right choice for the majority of heat exchanger applications. Seamless is only necessary when size constraints, extreme pressure, or code requirements demand it.
Our Manufacturing Equipment
| Equipment | Function |
|---|---|
| Vacuum Arc Remelting (VAR) Furnace | Produces high-purity titanium ingots |
| Hot Extrusion Press | Forms billets into tube hollows |
| Cold Rolling Mill | Reduces wall thickness with precision |
| Cold Drawing Bench | Finishes OD and surface quality |
| Bright Annealing Furnace | Controlled-atmosphere heat treatment |
| Straightening Machine | Corrects tube bow and twist |
| CNC Cutting Machine | Accurate length cutting |
| U-Bend Bending Machine | Precision cold bending |
| Strip Rolling Mill | Prepares strip for welded tube (welded line) |
| TIG Welding Line | Welds seam with full penetration (welded line) |
| Inline Annealing Furnace | Heat treats weld zone (welded line) |
| Weld Seam Planishing | Cold works weld flush (welded line) |
Testing and inspection
| Test / Inspection | Method | What We Check |
|---|---|---|
| Chemical Composition | Spectrographic / PMI | Verify UNS R50400 compliance. |
| Tensile Testing | Destructive | Yield, tensile, elongation. |
| Eddy Current Testing (ECT) | NDT, 100% | Surface and near-surface flaws. For welded tubes, 100% of weld seam. |
| Ultrasonic Testing (UT) | NDT (optional) | Internal defects. |
| Hydrostatic Testing | Water pressure | Leak-tightness. |
| Flattening Test | Mechanical | Ductility and weld quality. |
| Flaring Test | Mechanical | Tube expansion capability. |
| Reverse Bend Test | Mechanical | Weld seam ductility (welded tubes). |
| Dimensional Inspection | Micrometer, gauge | OD, WT, length, ovality, straightness. |
| Visual Inspection | 100% | Surface defects. |
Packaging
| Packaging Step | Method |
|---|---|
| End Caps | Plastic caps on both ends |
| Waterproof Wrap | PE film wrapping per bundle |
| Bundle Strapping | Steel straps with edge protectors |
| Crating | Export-grade plywood cases |
| Labeling | Heat number, grade, size, bundle ID |
FAQ
1. What is the difference between seamless and welded titanium tube?
Seamless tube is formed from a solid billet with no weld seam. Welded tube starts as a flat strip that is roll-formed and welded along the seam. Seamless is one-piece construction; welded has a longitudinal weld joint.
2. Which is stronger, seamless or welded titanium tube?
Seamless has a slight edge in burst pressure ratings because there is no weld seam. But for most heat exchanger applications under 5 MPa, both are more than strong enough.
3. Does welded titanium tube have a corrosion risk at the seam?
No. Properly welded and annealed Grade 2 tube has the same corrosion resistance at the weld as the base metal. The weld area is fully annealed and repassivated.
4. Which one costs more - seamless or welded?
Seamless typically costs 15-30% more than welded tube for the same size and grade. The difference comes from slower production and higher scrap rates.
5. Can welded tube be used in heat exchangers?
Yes. Welded Grade 2 tube is the industry standard for most shell-and-tube heat exchangers and condensers. It is widely used in power plants, desalination, and chemical processing.
6. What are the size limits for seamless vs welded tube?
Seamless is typically available from 3.18 mm to 114.3 mm OD. Welded covers 6.0 mm to 219 mm and larger. Welded is the only option for very large diameters.
7. Which one has tighter tolerances?
Welded tube typically holds tighter OD and wall tolerances because the starting strip is precisely rolled before forming. This is an advantage for tube sheet fit-up.
8. Is seamless tube always better than welded?
No. Welded is better for many applications - lower cost, tighter tolerances, and faster delivery. Seamless is only needed for very small diameters, very high pressure, or code requirements.
9. Which one ships faster?
Welded tube generally ships faster. Strip material is more readily available, production is faster, and standard sizes are often in stock. Seamless typically requires a mill run.
10. Can welded tube be bent into U-bends?
Yes. Welded Grade 2 tube bends reliably into U-bends with proper tooling. The weld seam orientation must be controlled during bending to minimize stress on the weld.
11. What standard covers both seamless and welded titanium tube?
ASTM B338 / ASME SB338 covers both seamless and welded titanium tubes for heat exchanger, condenser, and corrosion-resistant service.
12. How is the weld seam inspected?
100% Eddy Current Testing (ECT) is performed on every welded tube. This detects surface and near-surface flaws in the weld seam. Hydrostatic testing is also available.
13. Which one has thinner walls available?
Welded tube can be made with thinner walls because strip rolling is more precise than billet piercing. Seamless has practical minimum wall thickness limits.
14. Which type is more common in power plant condensers?
Welded Grade 2 tube is the industry standard for most power plant condensers due to its combination of low cost, good tolerances, and reliable performance.
15. What is the weld factor for pressure design?
ASME design codes use a weld factor of 0.85 - 0.95 for welded tube, depending on the inspection level. Seamless has a factor of 1.0. This affects pressure rating calculations.
16. What certifications do you provide?
EN 10204 3.1 Mill Test Certificate with full chemical and mechanical test reports. 3.2 certification is available with third-party witness (SGS, BV, or TUV).
