Why Specify Grade 2 Titanium Tube for Heat Exchangers?
| Advantage | Engineering Benefit | |
|---|---|---|
| Superior Chloride Resistance | Withstands seawater, brine, and cooling tower water without pitting. | Eliminates corrosion allowance, allowing for thinner walls and better heat transfer. |
| High Erosion Resistance | Resists impingement attack from high-velocity fluids. | Enables tube-side velocities up to 4.0 m/s in seawater, reducing fouling and improving heat transfer coefficients. |
| Excellent Ductility (≥20% Elongation) | Enables tight U-bending and reliable tube expansion. | Grade 2 is the preferred grade for U-tube heat exchangers due to its ability to form tight radii without cracking. |
| Moderate Strength | Minimum 275 MPa yield strength provides sufficient pressure containment. | Allows for thin-wall designs that maximize heat transfer surface area within a given shell size. |
| Weldability & Fabricability | Easily welded (TIG) and expanded using standard shop equipment. | Simplifies tube bundle fabrication, tube-to-tubesheet welding, and field repairs. |
Heat Exchanger Types Using ASTM B338 Grade 2 Titanium Tube
| Exchanger Type | Grade 2 Tube Form | Typical Service | Why Grade 2 is Specified |
|---|---|---|---|
| Shell & Tube Heat Exchanger | Straight tube | Process cooling, chemical heating, compressor intercoolers | Standard configuration; Grade 2 provides long-term corrosion protection on both shell and tube sides. |
| U-Tube Heat Exchanger | U-bend tube | High-temperature applications, refinery services, thermal expansion concerns | Grade 2's ductility (≥20% elongation) allows for bending to tight radii without stress cracking. |
| Power Plant Condenser | Straight tube, tube bundle | Surface condensers in thermal and nuclear plants | Grade 2 tubes resist impingement attack from high-velocity steam droplets and cooling water. |
| Seawater Cooler | Straight or coil tube | Marine cooling systems, offshore platforms | ASTM B338 Grade 2 titanium tube is virtually immune to seawater corrosion, ensuring 20+ years of service life. |
| Desalination Evaporator | Coil tube, straight tube | Multi-stage flash (MSF) and multi-effect distillation (MED) plants | Grade 2 withstands hot brine and flashing conditions where copper alloys suffer rapid attack. |
| Fin-Fan Air Cooler | Finned tube | Petrochemical plants, gas processing | Grade 2 finned tubes provide corrosion protection in polluted industrial atmospheres. |
Tube Dimensions and Tolerances for Grade 2 Heat Exchanger Tubes
Standard Size Range for ASTM B338 Grade 2 Titanium Tube
| Parameter | Standard Range | Common Heat Exchanger Sizes |
|---|---|---|
| Outside Diameter (OD) | 6.35 mm to 114.3 mm | 15.88 mm (5/8"), 19.05 mm (3/4"), 25.40 mm (1") |
| Wall Thickness (WT) | 0.3 mm to 5.0 mm | 0.7 mm, 0.9 mm, 1.0 mm, 1.2 mm |
| Tube Length | 1 m to 12 m (custom) | Random or fixed lengths per engineer's drawing |
| Form | Seamless or Welded | Welded & Drawn (W&D) is cost-effective for most condensers; seamless for high-pressure services |
Dimensional Tolerances per ASTM B338 for Grade 2 Titanium Tube
| Parameter | Tolerance | Engineering Significance |
|---|---|---|
| OD (≤25 mm) | ±0.08 mm | Ensures correct clearance for expansion into tubesheet holes. |
| OD (>25 mm) | ±0.10 mm or ±0.4% | Maintains assembly accuracy for larger-diameter condensers. |
| Wall Thickness | ±10% | Guarantees minimum pressure rating and corrosion allowance is preserved. |
| Straightness | ≤1.5 mm per meter | Prevents binding during tube insertion through baffles. |
| Ovality | ≤2% of OD | Ensures uniform expansion and 360° sealing contact. |
Fluid Velocity for Grade 2 Titanium Tubes
Recommended Velocities for ASTM B338 Grade 2 Titanium Tube
| Fluid | Recommended Velocity | Maximum Velocity | Why Grade 2 Excels |
|---|---|---|---|
| Seawater / Brackish Water | 2.0 – 3.5 m/s | 4.0 m/s | Grade 2 withstands impingement attack where Cu-Ni would suffer erosion at >2.5 m/s. |
| Fresh Water / Cooling Tower Water | 1.5 – 3.0 m/s | 3.5 m/s | Higher velocities minimize sedimentation and biofouling. |
| Light Hydrocarbons | 1.0 – 2.5 m/s | 3.0 m/s | Grade 2 resists corrosion from trace chlorides and organic acids. |
| Steam (gas phase) | 20 – 40 m/s | 50 m/s | Grade 2 resists droplet impingement erosion common in condenser inlet sections. |
| Chemicals / Weak Acids | 0.5 – 2.0 m/s | 2.5 m/s | Grade 2's passive film remains stable; consult corrosion data for specific chemicals. |
Temperature Limits for Grade 2 Titanium Tubes in Heat Exchangers
Temperature Guidelines for Grade 2 Titanium Tube
| Temperature Range | Material Behavior | Application Suitability |
|---|---|---|
| Up to 100°C (212°F) | Passive film stable; negligible corrosion in seawater. | Ideal for condensers, seawater coolers, and most industrial heat exchangers. |
| 100 – 200°C (212 – 392°F) | Slight decrease in strength; corrosion resistance remains high. | Suitable for desalination evaporators, process heaters, and hot water systems. |
| 200 – 315°C (392 – 600°F) | Oxidation resistance remains acceptable; avoid strong reducing acids. | Acceptable for high-temperature process streams; Grade 7 or 12 may be considered for reducing acid conditions. |
| Above 315°C (600°F) | Risk of hydrogen absorption and oxidation increases significantly. | Not recommended; consult titanium alloy specialist for higher temperature requirements. |
Tube-to-Tubesheet Joints for Grade 2 Titanium Tubes
Tube-to-Tubesheet Joining Methods for Grade 2 Titanium Tube
| Method | Grade 2 Suitability | Advantages | Key Considerations |
|---|---|---|---|
| Roller Expansion | Excellent | Simple, cost-effective, field-repairable. | Requires precise hole sizing; Grade 2's ductility ensures good sealing without cracking. |
| Hydraulic Expansion | Excellent | Uniform expansion; consistent sealing; reduces tube stress. | Specialized equipment required; ideal for Grade 2 in high-pressure condensers. |
| Roller Expansion + Seal Weld | Recommended | Eliminates crevice corrosion; adds mechanical strength. | Standard practice for seawater-cooled Grade 2 titanium tube bundles. |
| Full Strength Weld | Good | Maximum joint strength. | More expensive; Grade 2 is readily weldable (TIG, with argon shielding). |
Inspection and Testing of Grade 2 Titanium Heat Exchanger Tubes
| Test | Requirement | Why It Matters for Grade 2 Tubes |
|---|---|---|
| Eddy Current Testing (ECT) | 100% for welded tubes; optional for seamless | Detects surface and near-surface defects. Critical for Grade 2 welded tubes to ensure weld integrity. |
| Hydrostatic Test | Required | Verifies pressure integrity; confirms Grade 2 tube can withstand design pressure without leakage. |
| Ultrasonic Testing (UT) | Optional (seamless) | Detects internal defects in seamless Grade 2 tubes. |
| Flaring Test | Required | Confirms Grade 2's ductility for expansion into tubesheet. |
| Flattening Test | Required for welded tubes | Checks weld ductility; Grade 2's >20% elongation ensures passing results. |
| PMI (Positive Material Identification) | Recommended | Confirms Grade 2 (UNS R50400) chemistry; prevents material mix-up. |
| Hydrogen Content Analysis | Recommended for critical services | Ensures H content ≤0.015%, preventing hydrogen embrittlement risk. |
Our Factory
| Equipment | Function | Quality Impact on Grade 2 Tubes |
|---|---|---|
| Cold Rolling Mill | Reduces wall thickness with high precision. | Ensures ±10% wall thickness tolerance per ASTM B338. |
| Cold Drawing Machine | Refines OD and improves surface quality. | Achieves ±0.08 mm OD tolerance for perfect tubesheet fit. |
| Bright Annealing Furnace | Controlled atmosphere heat treatment. | Produces fully annealed Grade 2 tubes with ≥20% elongation for U-bending. |
| Straightening Machine | Corrects tube bending. | Guarantees ≤1.5 mm/m straightness for easy bundle assembly. |
| Eddy Current Tester | 100% NDT inspection. | Ensures weld integrity for welded Grade 2 tubes. |
| PMI Analyzer | Positive Material Identification. | Confirms UNS R50400 chemistry on every production lot. |
Packaging
| Packaging Component | Material / Method | Protection Purpose |
|---|---|---|
| Plastic End Caps | PE or PP caps on both ends | Prevents debris and moisture ingress-critical for Grade 2's clean surface. |
| Waterproof Wrapping | PE film wrapping each bundle | Protects against seawater and humidity during ocean freight. |
| Export Wooden Crates | Plywood or solid wood (ISPM 15 compliant) | Provides impact protection for fragile tube bundles. |
| Steel Strapping | Reinforced steel straps | Prevents tube movement and bending during transit. |
| Traceability Labels | Heat number, grade, size, order number | Ensures full traceability to ASTM B338 certification. |
fAQ
1. What is ASTM B338 Grade 2 titanium tube used for in heat exchangers?
It is used as the heat transfer tube in condensers, coolers, evaporators, and shell-and-tube heat exchangers, especially in seawater, brackish water, and chemical services requiring high corrosion resistance.
2. What is the maximum operating temperature for Grade 2 titanium tube?
Up to 315°C (600°F) in oxidizing and neutral environments. Beyond this, consider Grade 7 or Grade 12 alloys.
3. What fluid velocity can a Grade 2 titanium tube handle in seawater?
Up to 4.0 m/s without erosion damage. This is a key advantage over copper-nickel alloys (limited to ~2.5 m/s).
4. What is the wall thickness tolerance for ASTM B338 Grade 2 tube?
The standard tolerance is ±10% of the specified nominal wall thickness.
5. Can Grade 2 titanium tube be bent into U-shapes?
Yes. Grade 2 has a minimum elongation of ≥20%, making it the preferred grade for U-bend tubes in heat exchangers.
6. Is a seal weld required for Grade 2 titanium tubes in seawater?
Highly recommended. A seal weld (TIG) prevents crevice corrosion at the tube-to-tubesheet joint, which is critical in chloride-rich seawater environments.
7. How does Grade 2 titanium tube compare to 316L stainless steel in seawater?
Grade 2 is far superior. 316L suffers pitting and crevice corrosion in seawater, while Grade 2 is virtually immune. Grade 2 also tolerates higher velocities.
8. What is the minimum yield strength of Grade 2 titanium tube?
The minimum yield strength (0.2% offset) per ASTM B338 is 275 MPa (40,000 psi) .
9. What testing is required for ASTM B338 Grade 2 welded tubes?
100% Eddy Current Testing (ECT) is required, along with hydrostatic testing, flaring, and flattening tests.
10. Can you provide an EN10204 3.1 Mill Test Certificate for Grade 2 tubes?
Yes. We provide a 3.1 MTC with every shipment, confirming chemical composition, mechanical properties, and full traceability to the heat number.
11. What are common stock sizes for Grade 2 heat exchanger tubes?
Common stock sizes include OD 15.88 mm, 19.05 mm, and 25.40 mm with wall thicknesses of 0.7 mm, 0.9 mm, and 1.0 mm.
12. Can Grade 2 titanium tube be used with tube sheets made of other materials?
Yes. However, galvanic corrosion potential must be considered. Grade 2 is noble (cathodic) to carbon steel and most aluminum alloys; insulating coatings or cathodic protection may be needed.
13. What is the typical lead time for ASTM B338 Grade 2 titanium tubes?
Standard sizes in stock: 7–15 days. Custom sizes: 2–4 weeks. Large EPC orders: negotiable.
14. Are third-party inspections (SGS, BV, TUV) supported?
Yes. We fully support and coordinate SGS, BV, TUV, or any recognized third-party inspection per your project requirements.
15. How should Grade 2 titanium tubes be cleaned if fouling occurs?
Use mechanical brushing, high-pressure water jetting (up to 1000 bar), or acid cleaning with inhibited acid. Grade 2's hardness and corrosion resistance make it safe for aggressive cleaning methods.
