Stainless Steel Coil Tube — Steam Superheater Coiltube (Product No. 636)
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a specialized heat-exchange component manufactured by Wenzhou Jixing Metal Materials Co., Ltd., engineered for deployment in high-temperature, high-pressure environments such as steam superheaters, economizers, and reheaters within power generation and process heating systems. This product is supplied in continuous coiled form, enabling efficient on-site installation, reduced joint count, and superior thermal performance in convective heat transfer applications. The coil tube design eliminates the need for extensive field welding, significantly reducing installation time and the risk of leak points in critical boiler and process equipment.
Material & Properties
The Coil Tube is fabricated from high-grade stainless steel grades selected for exceptional resistance to thermal fatigue, oxidation, and corrosion under sustained superheat conditions. The primary material grades include:
- AISI 304 (UNS S30400) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability, suitable for moderate-temperature superheater services.
- AISI 321 (UNS S32100) — Titanium-stabilized austenitic stainless steel offering superior resistance to intergranular corrosion and thermal cycling, ideal for higher-temperature superheater applications.
- AISI 310S (UNS S31008) — High-chromium, high-nickel austenitic stainless steel providing outstanding resistance to oxidation and carburization at temperatures exceeding 1100°C.
Key mechanical and physical properties of the base material are summarized below:
| Property | 304 Grade | 321 Grade | 310S Grade |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 515 |
| Yield Strength (MPa) | ≥ 205 | ≥ 205 | ≥ 205 |
| Maximum Service Temperature (°C) | 870 | 925 | 1150 |
| Thermal Expansion Coefficient (×10⁻⁶/°C) | 16.0 – 17.3 | 16.5 – 17.7 | 18.0 – 20.0 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 16.3 | 26.2 |
| Chromium Content (%) | 18.0 – 20.0 | 17.0 – 19.0 | 24.0 – 26.0 |
| Nickel Content (%) | 8.0 – 10.5 | 9.0 – 12.0 | 19.0 – 22.0 |
Specifications
The Coil Tube is supplied in accordance with applicable international standards including ASTM A213, ASTM A269, ASME SA-213, EN 10216-5, and GB/T 12771. The following table outlines the standard dimensional and performance specifications:
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 12.7 mm – 168.3 mm (½" – 6") |
| Wall Thickness (WT) | 0.5 mm – 6.0 mm (0.020" – 0.236") |
| Coil Diameter (Coiling Diameter) | 1.2 m – 3.0 m (adjustable per project requirement) |
| Tube Length per Coil | 60 m – 300 m (continuous) |
| End Form | Plain end, beveled end, or threaded end |
| Surface Finish | Pickled & Passivated (P&P), Mirror Polished (Ra ≤ 0.2 μm), or As-rolled |
| Maximum Operating Pressure | Up to 40 MPa (6,000 psi), grade-dependent |
| Maximum Operating Temperature | Up to 1150°C (grade-dependent) |
| Heat Treatment Condition | Solution Annealed (SA), Annealed & Pickled |
| Applicable Standards | ASTM A213 / ASME SA-213 / EN 10216-5 / GB/T 12771 |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and long-term service reliability:
- Hot Rolling (Hot Rolled Coil Production) — Continuous casting billets are reheated to 1200–1250°C and hot-rolled into seamless tube blanks on a piercer mill and rolling mill. The hot-rolled coil achieves the required outer diameter and wall thickness tolerances.
- Cold Drawing / Cold Rolling (Optional) — For applications requiring tighter dimensional tolerances and improved surface finish, the hot-rolled coil is subjected to cold drawing or cold rolling. This process enhances mechanical properties (up to 30% increase in tensile strength) and produces near-net-shape dimensions.
- Coiling (Coil Forming) — The formed tube is coiled around a mandrel using a precision coiling machine. The coiling process employs controlled bending stress to prevent plastic deformation, cracking, or ovality beyond acceptable limits (ovality ≤ 0.5% of OD).
- Solution Annealing — The coiled tube is heat-treated at 1050–1150°C followed by controlled cooling (air cooling or furnace cooling) to dissolve carbides, restore full austenitic microstructure, and relieve residual stresses from forming.
- Pickling & Passivation — The annealed coil is immersed in a mixed acid bath (nitric acid + hydrofluoric acid) to remove scale, oxide, and surface contaminants. Subsequent passivation establishes a uniform chromium oxide film (Cr₂O₃) that provides a protective barrier against corrosion.
- Quality Inspection & Testing — Each coil undergoes comprehensive inspection including hydrostatic pressure testing, dimensional verification, chemical composition analysis (spectrometry), and non-destructive testing (eddy current or ultrasonic inspection).
Applications
The Stainless Steel Coil Tube is purpose-engineered for demanding thermal and chemical processing environments. Primary application domains include:
- Steam Superheaters in Power Plants — Coil tubes are deployed in convective and radiant superheater sections of utility boilers and industrial steam generators, where they raise saturated steam temperature to 400–600°C under pressures of 10–40 MPa. The continuous coil design facilitates replacement during maintenance outages without extensive field welding.
- Reboilers and Evaporators in Petrochemical Processing — Used in distillation columns, crude oil fractionation units, and refinery process heaters where resistance to sour gas (H₂S) and thermal cycling is critical.
- Heat Exchangers in Chemical Processing — Applied in reactors, condensers, and heat recovery steam generators (HRSG) in chemical plants handling aggressive media including acids, halides, and organic solvents.
- Industrial Boiler Economizers and Air Preheaters — Coil tubes serve as heat-absorbing elements in waste heat recovery systems, improving overall thermal efficiency of combustion systems.
- Food and Pharmaceutical Processing — Mirror-polished coil tubes are utilized in sanitary heat exchangers for pasteurization, sterilization, and pharmaceutical formulation processes requiring compliance with FDA and EHEDG standards.
- Marine and Offshore Applications — Deployed in marine boiler superheaters and offshore platform process heating systems where resistance to saltwater corrosion and cyclic loading is essential.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring traceability and conformance to international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and quality assurance processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to environmentally responsible production practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- EN 10204 3.1 / 3.2 — Material Test Certificates (MTC) issued per European standard, providing full traceability of chemical composition, mechanical properties, and heat treatment records.
- ASME "S" Stamp — Certification for components intended for use in pressure vessels and piping systems governed by ASME Boiler and Pressure Vessel Code.
- NACE MR0175 / ISO 15156 — Compliance for sour service applications where resistance to sulfide stress cracking is required.
Unique Selling Points
- Continuous Coil Supply — Eliminates the need for field butt-welding of individual tube segments, reducing installation time by up to 60% and minimizing potential leak points in critical high-pressure systems.
- Thermal Fatigue Resistance — The selected austenitic stainless steel grades provide superior resistance to thermal cycling and fatigue cracking, extending service life in superheater applications where repeated heating and cooling cycles are routine.
- Full Traceability — Every coil is accompanied by a complete material test certificate with heat number traceability, chemical analysis, mechanical test results, and heat treatment documentation, ensuring full supply chain accountability.
- Customizable Specifications — Wenzhou Jixing Metal Materials Co., Ltd. offers tailored coil diameters, tube dimensions, surface finishes, and end forms to meet project-specific engineering requirements, enabling optimized integration into existing superheater and heat exchange systems.