Yuhong Group Co., Ltd. engineers and fabricates ASME-coded shell-and-tube heat exchangers, pressure vessels, and air coolers for thermal processing industries worldwide. Beyond complete equipment, we supply critical replacement assemblies including tube bundles (straight and U-bend), heat exchanger tubes, finned tubes, and all related components—tubesheets, baffles, channel heads, and tie rods. This product focus covers the S32750 / F53 super duplex stainless steel tube bundle, engineered for aggressive chloride and sour service environments where conventional materials fall short.
This TEMA-standard heat exchanger tube bundle is precision-engineered from ASME SA789 S32750 (UNS S32750) super duplex stainless steel seamless tubes, anchored by a forged ASME SA182 F53 (UNS S32750) tubesheet. The material match between tubes and tubesheet ensures metallurgical homogeneity and reliable, crack-resistant welded joints. Designed for extreme operating conditions—severe corrosion, high pressure, and thermal cycling—the bundle serves offshore platforms, chemical processing plants, oil refineries, and flue gas desulfurization (FGD) systems.
| Parameter | Specification |
|---|---|
| Tube Standard / Grade | ASME SA789 S32750 (UNS S32750) |
| Tubesheet Standard / Grade | ASME SA182 F53 (UNS S32750) |
| Design Code | TEMA (latest edition) |
| ASME Certification | U Stamp |
| NDT Methods | Eddy Current (ET), Ultrasonic (UT), Penetrant (PT), Hydrostatic (HT) |
| Typical Tube Dimensions | 19.05 mm OD × 2.11 mm wall × 6,096 mm length (custom available) |
UNS S32750 (also known as 2507, EN 1.4410) is a super duplex stainless steel with a dual-phase ferritic-austenitic microstructure. Its high chromium (24–26%), molybdenum (3–5%), and nitrogen (0.24–0.32%) content delivers a Pitting Resistance Equivalent Number (PREN) exceeding 40—typically 41–43. This translates to:
Critical Pitting Temperature (CPT) exceeding 50°C
Superior resistance to crevice corrosion in seawater and high-chloride brines
Excellent resistance to chloride stress corrosion cracking (SCC), with service limits extending to approximately 130°C versus ~100°C for standard duplex 2205
Listed in NACE MR0175 / ISO 15156 for sour gas service
| Element | Composition Range |
|---|---|
| Chromium (Cr) | 24.0 – 26.0% |
| Nickel (Ni) | 6.0 – 8.0% |
| Molybdenum (Mo) | 3.0 – 5.0% |
| Nitrogen (N) | 0.24 – 0.32% |
| Carbon (C) | 0.030% max |
| Manganese (Mn) | 1.20% max |
| Property | Value |
|---|---|
| Tensile Strength (min) | ≥ 795 MPa (115 ksi) |
| Yield Strength 0.2% (min) | ≥ 550 MPa (80 ksi) |
| Elongation (min) | ≥ 15% |
| Hardness | ≤ 32 HRC (≤ 310 HBW) |
The yield strength is approximately twice that of standard 316L austenitic stainless steel, enabling thinner tube walls and reduced bundle weight without compromising structural integrity.
Solution Annealing & Quenching: Tubes and tubesheet undergo solution annealing at 1025–1125°C followed by rapid water quenching to achieve the optimal 40–60% ferrite phase balance. This phase balance is critical—deviation leads to selective ferrite corrosion and premature failure.
Corrosion Testing: Per ASTM A923 Method C (ferric chloride test at 50°C) to verify pitting resistance.
Nondestructive Examination: 100% eddy current testing (ET) on tubes, ultrasonic testing (UT) on tubesheet forging, and penetrant testing (PT) on weld joints.
Documentation: Mill Test Certificates per EN 10204 Type 3.1 or 3.2, reporting chemical composition, mechanical properties, ferrite content, and corrosion test results.
Offshore & Marine: Seawater coolers, subsea production systems, platform heat exchangers
Oil & Gas Refining: Sour gas processing, high-pressure/high-temperature (HP/HT) wells, wet H₂S environments
Chemical Processing: Heat exchangers handling chloride-bearing solutions, hot brines, and organic acids
Flue Gas Desulfurization (FGD): Heat exchange equipment in pollution control systems
Pressure Vessels: ASME Section VIII Div. 1 applications
Q: When should S32750 be specified over standard duplex 2205 (F51)?
Specify S32750/F53 for process fluids containing chlorides at temperatures above 40°C, sour service requiring PREN ≥ 40 per NACE MR0175/ISO 15156, or elevated seawater temperatures. F53 provides a PREN of 42–45 (versus 34–36 for F51) and a critical pitting temperature (CPT) of 55–65°C (versus 30–35°C for F51).
Q: What is the maximum service temperature for S32750?
The maximum continuous service temperature is limited to approximately 315°C (600°F). Above this temperature, long-term exposure leads to embrittlement due to the precipitation of deleterious intermetallic and secondary phases (such as σ phases)
Q: Why does the tubesheet need to match the tube material?
A forged SA182 F53 tubesheet offers optimal metallurgical compatibility with SA789 S32750 tubes. Eliminating material mismatches prevents thermal expansion stresses and galvanic action, minimizing the risk of weld cracking and joint corrosion.
Q: What causes premature failure in super duplex tube bundles?
The primary failure modes for super duplex stainless steels are pitting and chloride SCC, often driven by phase imbalance or harmful intermetallics. Incorrect solution annealing or slow cooling rates compromise corrosion resistance by forming brittle sigma phases or pushing ferrite levels out of specification. S32750 tube bundles require strict phase balance validation (40–60% ferrite) and ASTM A923 testing to ensure long-term service integrity.
