Tube Material Selection: When Titanium or Duplex Makes Sense (EPC Case-Based)
By Qiangbin Chu · Sales Manager & Operations Lead, Suzhou Lmart Energy Equipment
Key Takeaways
- Use titanium tubes for seawater or high-chloride cooling duties where corrosion risk dominates lifecycle cost.
- Use duplex stainless when chloride stress corrosion cracking (SCC) is a concern and you need a balance between corrosion performance and cost.
- An EPC "ask-first" checklist covering media chemistry, temperature envelope, and tube-to-tubesheet joint preference prevents late material changes.
- Material decisions should be locked early in FEED to avoid redesign costs that can exceed 15% of equipment value.
- Lmart fabricates heat exchangers with titanium (Gr.2/Gr.7), duplex (UNS S31803), and super duplex (UNS S32750) tubes per ASME VIII and TEMA standards.
Why Tube Material Selection Is a Lifetime Risk Decision
Tube material decisions are rarely "just materials." They are lifetime risk decisions encompassing corrosion, fouling, maintenance downtime, and replacement strategy. For EPC procurement teams, getting the tube material wrong can mean unplanned shutdowns, re-tubing costs, and project delays that ripple through the entire schedule.
This guide helps EPC teams quickly decide when titanium or duplex stainless steel makes sense for shell-and-tube heat exchangers, plus a practical checklist to avoid late material changes during fabrication.
When Titanium Often Makes Sense
Titanium (typically Grade 2 or Grade 7) is the go-to choice when the operating environment is dominated by seawater or high-chloride media. TIMET's corrosion reference manual confirms that titanium exhibits excellent resistance in seawater applications, though biofouling mitigation strategies (e.g., chlorination approach) must be defined upfront.
- Seawater or high-chloride cooling duties where corrosion risk dominates lifecycle cost
- Projects expecting long service life (20+ years) with fewer tube failures
- Services where biofouling is expected and a chlorination or anti-fouling strategy is defined
- Offshore or coastal installations where replacement access is limited and costly
Titanium can be the right answer for seawater or severe chloride environments, but the best EPC approach is to decide based on media chemistry and lifecycle risk — then lock it early to avoid late redesign.
When Duplex Stainless Often Makes Sense
Duplex stainless steels (UNS S31803 / 2205, or super duplex UNS S32750 / 2507) offer a compelling middle ground. The Nickel Institute notes that duplex grades are highly resistant to chloride stress corrosion cracking and typically deliver higher strength than common austenitic grades like 316L — often allowing thinner tube walls and reduced weight.
- Chloride SCC risk where austenitic stainless steels (304/316) become sensitive
- You need higher mechanical strength and good corrosion performance in chloride environments
- You want a balance between corrosion performance and cost versus titanium
- Process temperatures remain within the duplex operating window (typically −50°C to +300°C, depending on grade and environment)
| Parameter | Titanium (Gr.2 / Gr.7) | Duplex (2205 / 2507) |
|---|---|---|
| Seawater resistance | Excellent — virtually immune | Good to very good (super duplex better) |
| Chloride SCC resistance | Immune | High (far superior to 316L) |
| Strength (yield) | ~275 MPa (Gr.2) | ~450 MPa (2205) / ~550 MPa (2507) |
| Relative tube cost | High (3–5× vs CS) | Moderate (1.5–2.5× vs CS) |
| Fabrication complexity | Requires inert gas shielding | Standard but controlled heat input |
| Typical application | Seawater coolers, condensers | Process exchangers, chloride services |
| ASME material spec | SB-338 (Gr.2 / Gr.7) | SA-789 (UNS S31803 / S32750) |
EPC "Ask-First" Checklist for Tube Material
Before finalizing tube material on a purchase order, EPC procurement and process engineering teams should confirm the following parameters with the licensor or process engineer. Locking these early prevents late-stage material changes that cascade into re-design, re-procurement, and schedule slippage.
- Water/media chemistry: chloride concentration, sulfides, pH range, presence of oxidizers
- Operating temperature envelope and upset conditions (max temperature excursions)
- Flow velocity limits and erosion/fouling risk assessment
- Cleaning method: chemical cleaning vs mechanical cleaning (impacts internal surface finish requirements)
- Tube-to-tubesheet joint preference: rolled, welded, or rolled-and-welded — and the associated inspection plan
- Corrosion allowance philosophy — especially important for titanium where zero corrosion allowance is common
- Avoid selecting titanium "just to be safe" without confirming media chemistry — it adds cost and may not address the actual failure mode.
- Duplex grades require controlled welding heat input; confirm your fabricator has qualified WPS for the selected grade before committing.
Per ASME Section VIII Div.1 and TEMA RCB standards, tube material must be specified on the equipment data sheet and reflected in the Manufacturer's Data Report (MDR). Any material change after PO issuance typically requires formal deviation approval from the EPC project engineer.
Need tube material recommendations for your heat exchanger project?
Our engineering team provides technical proposals with GA drawings and budget pricing within 48 hours.
Lmart Experience: Titanium & Duplex Heat Exchangers
Lmart has fabricated shell-and-tube heat exchangers with titanium tubes (Gr.2, Gr.7) for seawater cooling duties in Middle East and Southeast Asian petrochemical plants, as well as duplex 2205 tube bundles for chloride-containing process services in LNG and refinery applications. All units are built per ASME VIII Div.1 with TEMA type designation, and can be supplied with third-party inspection by any of our six approved classification societies (DNV, BV, CCS, ABS, LR, NK).
Our 38,000 m² workshop in Zhangjiagang is equipped with dedicated clean rooms for titanium welding, orbital TIG welding machines for tube-to-tubesheet joints, and in-house helium leak testing capability — ensuring consistent quality for exotic tube materials.
Summary
Tube material selection for shell-and-tube heat exchangers is a lifecycle decision, not just a line item on a material requisition. For seawater and severe chloride environments, titanium delivers near-immunity to corrosion at a higher upfront cost. Duplex stainless steels offer excellent chloride SCC resistance with superior strength at a more moderate price point. The key for EPC teams is to lock material early based on confirmed process data — and to verify that the fabricator has qualified welding procedures for the selected grade.
Lmart holds ASME U-Stamp, PED/CE, and 6 classification society approvals (DNV, BV, CCS, ABS, LR, NK).
103-mu campus in Zhangjiagang · 38,000 m² workshop · 300+ staff · 15,000 T/year capacity
Last reviewed: December 20, 2025 · Technical accuracy verified by Lmart Engineering Dept.
Frequently Asked Questions
Should we choose titanium "just to be safe"?
Not always. Titanium is the right answer for seawater or severe chloride environments, but the best EPC approach is to decide based on confirmed media chemistry and lifecycle risk analysis. Choosing titanium without proper justification adds significant cost (3–5× vs carbon steel) and may not address the actual failure mode. Lock the decision early based on process data to avoid late redesign.
What is the cost difference between titanium and duplex tubes?
Titanium tubes (Gr.2) typically cost 3–5 times more than carbon steel, while duplex 2205 tubes are roughly 1.5–2.5 times the cost of carbon steel. However, lifecycle cost analysis often favors the higher-grade material in corrosive services due to reduced maintenance, fewer unplanned shutdowns, and extended service intervals. Your fabricator should provide a total installed cost comparison including welding and inspection requirements.
Can Lmart fabricate heat exchangers with titanium or duplex tubes?
Yes. Lmart holds ASME U-Stamp and has qualified welding procedures (WPS) for titanium Gr.2/Gr.7 and duplex 2205/2507 tube-to-tubesheet joints. Our facility includes dedicated clean rooms for titanium welding, orbital TIG welding machines, and in-house helium leak testing. All units include full MTR traceability and can be supplied with third-party inspection by DNV, BV, CCS, ABS, LR, or NK.
What welding challenges exist for duplex stainless steel tubes?
Duplex grades require controlled heat input during welding to maintain the correct austenite-ferrite balance (typically 30–70% ferrite). Excessive heat input can form sigma phase, reducing corrosion resistance and toughness. Interpass temperature must be limited (typically ≤150°C for 2205). Confirm your fabricator has qualified WPS with ferrite measurement per ASTM E562 or equivalent before placing the order.
How do I specify tube material on the equipment data sheet?
Per TEMA and ASME VIII requirements, specify the UNS number (e.g., UNS R50400 for Ti Gr.2, UNS S31803 for 2205 duplex), tube OD and wall thickness, ASME material specification (SB-338 or SA-789), and any supplementary requirements such as solution annealing or specific corrosion testing (e.g., ASTM G48 for duplex). Include the corrosion allowance — typically zero for titanium, 1.5 mm for duplex in moderate services.
Ready to Discuss Your Project?
Our engineering team delivers technical proposals with GA drawings and budget pricing within 48 hours. 300+ staff, 18 international certifications, equipment exported to 50+ countries.