Detailed Product Description
Application & Compliance
ASME SB338 Gr.2 and Gr.7 titanium seamless tubes are specified for shell and tube heat exchangers operating in severely corrosive environments where carbon steel, stainless steel, and copper alloys fail prematurely. In coastal power plant surface condensers using seawater as the cooling medium, titanium tubes resist chloride pitting, crevice corrosion, and erosion-corrosion that destroy Cu-Ni and stainless steel tubes within a few years. In nuclear reactor cooling systems, titanium tubes provide the required combination of corrosion resistance, thermal stability, and long service life under radiation exposure. In seawater desalination plants, titanium tubes withstand continuous exposure to high-chloride brine at elevated temperatures. In chemical processing heat exchangers, they handle oxidizing acids, chlorides, and hypochlorite solutions.
The tubes are manufactured and tested in accordance with ASME SB-338 / ASTM B338, ASME Boiler and Pressure Vessel Code Section II-D for allowable stress basis, and ASME Boiler and Pressure Vessel Code Section VIII Division 1 for pressure boundary applications. Certification is available per EN 10204 Type 3.1 or 3.2.
Problem Solved
Titanium tubes solve the problem of premature heat exchanger failure caused by chloride-induced corrosion. Copper-nickel and stainless steel tubes undergo pitting, crevice corrosion, and stress corrosion cracking in chloride-bearing cooling water, leading to tube wall penetration, cooling water contamination, and unplanned shutdowns. Titanium forms a stable, protective oxide film that regenerates immediately when damaged, providing immunity to chloride attack in seawater and brackish water. Titanium tubes typically provide 20 to 30 years of service life in seawater cooling applications, eliminating the recurring cost of tube bundle replacement every 3 to 5 years associated with copper alloys.
Material Specification – ASME SB338 Gr.2 and Gr.7
ASME SB-338 / ASTM B338 covers 28 grades of seamless and welded titanium and titanium alloy tubes for surface condensers, evaporators, and heat exchangers. Grade 2 is unalloyed titanium with moderate strength and excellent corrosion resistance. Grade 7 is unalloyed titanium plus 0.12 to 0.25% palladium, providing enhanced crevice corrosion resistance in reducing acid and chloride environments.
Grade 2 (UNS R50400)
Grade 2 is the most widely used titanium grade for heat exchanger tubes. It is an unalloyed titanium with excellent corrosion resistance in oxidizing and mildly reducing environments, good weldability, and high ductility.
Grade 7 (UNS R52400)
Grade 7 is identical to Grade 2 with the addition of 0.12 to 0.25% palladium. The palladium addition enhances crevice corrosion resistance in high-chloride and reducing acid environments, extending the range of conditions where titanium can be used.
Chemical Composition (per ASME SB338)
| Element | Gr.2 (%) | Gr.7 (%) |
|---|---|---|
| Titanium (Ti) | Balance | Balance |
| Carbon (C) | 0.1 max | 0.08 max |
| Iron (Fe) | 0.3 max | 0.30 max |
| Hydrogen (H) | 0.015 max | 0.015 max |
| Nitrogen (N) | 0.03 max | 0.03 max |
| Oxygen (O) | 0.25 max | 0.25 max |
| Palladium (Pd) | — | 0.12 – 0.25 |
| Residuals (each / total) | 0.10 / 0.40 max | 0.10 / 0.40 max |
Mechanical Properties (per ASME SB338)
| Property | Gr.2 | Gr.7 |
|---|---|---|
| Tensile Strength, min | 345 MPa (50 ksi) | 345 MPa (50 ksi) |
| Yield Strength (0.2% offset), min | 275 MPa (40 ksi) | 275 MPa (40 ksi) |
| Elongation in 50 mm, min | 20% | 20% |
| Elastic Modulus | 105 GPa | 105 GPa |
| Density | 4.51 g/cm³ | 4.51 g/cm³ |
| Thermal Conductivity | 16.4 W/m·K | 16.4 W/m·K |
| Melting Point | 1660 – 1670°C | 1660 – 1670°C |
Manufacturing Process
Seamless titanium tubes are produced by cold drawing or cold rolling from titanium bar or tube hollows. The manufacturing process includes raw material inspection, piercing or extrusion, cold drawing, degreasing and cleaning, annealing in a controlled atmosphere furnace, straightening, cutting to length, and final inspection. For Grade 7, the palladium addition is made during melting to ensure uniform distribution throughout the tube wall. The finished tube surface is pickled or bright annealed to remove oxide scale and provide a clean, corrosion-resistant surface. Grade 2 tubes are annealed at 600 to 700°C.
Size Range
Outside diameter: 6.0 mm to 219.0 mm.
Wall thickness: 0.5 mm to 12.0 mm.
Length: Up to 26 m (customizable).
Bending radius and leg length: custom-manufactured per customer drawings.
Testing and Quality Control
Each titanium tube is subjected to the following tests in accordance with ASME SB-338:
Hydrostatic Test – Each tube is subjected to hydrostatic testing unless a non-destructive electric test is specified as a substitute by the purchaser.
Eddy Current Testing (ET) – 100% of tubes are tested for surface and subsurface defects.
Ultrasonic Testing (UT) – For detection of internal discontinuities.
Flattening Test – Assesses ductility and detects laminations or seams.
Flaring Test – Evaluates resistance to deformation and wall thickness consistency.
Hardness Testing (HT) – Verifies material condition.
Chemical Composition Analysis – Spectrometric or wet chemical analysis to verify titanium, palladium, and interstitial elements.
Dimensional Inspection – Verification of outside diameter, wall thickness, length, and straightness.
Documentation
Each shipment is supplied with complete documentation including Mill Test Certificates (EN 10204 Type 3.1), heat treatment records, hydrostatic test reports, NDE reports (ET, UT as applicable), dimensional inspection reports, and material traceability records.
Grade Selection Guide
| Service Environment | Recommended Grade | Reason |
|---|---|---|
| Seawater with continuous chlorination | Gr.2 | Sufficient corrosion resistance at lower cost |
| Seawater with intermittent chlorination or high crevice risk | Gr.7 | Palladium enhances crevice corrosion resistance |
| High-temperature brine (>120°C) | Gr.7 | Pd improves resistance to reducing acid attack |
| Dilute hydrochloric or sulfuric acid | Gr.7 | Pd provides corrosion resistance in reducing acids |
| Oxidizing acids, nitric acid | Gr.2 | Native oxide film resistant to oxidizing media |
Applications
ASME SB338 Gr.2 and Gr.7 titanium seamless tubes are used in:
Shell and Tube Heat Exchanger – Tube side or shell side heat transfer in corrosive service
Surface Condensers – Coastal power plant seawater cooling
Nuclear Reactors – Primary and secondary cooling circuits
Seawater Desalination – Multi-stage flash and reverse osmosis preheaters
Chemical Processing – Heat exchangers handling chlorides, acids, and oxidizing media
Evaporators – Falling film and forced circulation evaporators
Heat Exchanger Tubesheet – Tube-to-tubesheet joints in titanium and titanium-clad tubesheets
Marine Engineering – Shipboard cooling systems and offshore platform heat exchangers
For a rapid quotation on ASME SB338 Gr.2 or Gr.7 Titanium Seamless Tube, please provide the following information:
Quantity (number of pieces or weight)
Grade (Gr.2 or Gr.7)
Outside diameter and wall thickness
Length required (straight or U-bend)
Surface finish requirement (Annealed / Pickled / Bright Annealed)
End preparation (plain ends or beveled ends)
Delivery period required
