Stainless Steel High-Temperature Coil Tube (Coiltube) — Product Technical Specification
Product Overview
The Stainless Steel High-Temperature Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous coil-form tubing designed for demanding high-temperature industrial applications. These coil tubes are primarily deployed in superheater systems of single-stage furnaces, where they facilitate the efficient transfer of thermal energy from combustion gases to process steam or working fluids. The coiled configuration maximizes heat exchange surface area within a compact footprint, making these tubes indispensable in petrochemical refining, metallurgical processing, and power generation facilities.
Derived from rigorous operational experience and failure analysis of superheater steam high-temperature coil tubes in single-stage furnace environments, the design philosophy of this product emphasizes superior thermal stability, resistance to creep deformation, and extended service life under sustained high-temperature and high-pressure conditions. The product catalog entry (Item No. 1174) reflects a lineage of continuous improvement informed by field performance data and metallurgical damage assessment studies.
Material & Properties
Stainless steel coil tubes are fabricated from austenitic and austenitic-ferritic (duplex) stainless steel grades selected for their exceptional resistance to oxidation, scaling, and thermal fatigue at elevated operating temperatures. The primary material grades include:
- SAE 310 / 310S (UNS S31000 / S31008): High-chromium, high-nickel austenitic grade offering outstanding resistance to thermal cycling and oxidation up to 1150°C (2100°F). Ideal for superheater and reheater applications.
- SAE 321 (UNS S32100): Titanium-stabilized austenitic stainless steel with enhanced resistance to intergranular corrosion and stress corrosion cracking. Suitable for moderate-temperature superheater duties up to 900°C (1650°F).
- SAE 347H (UNS S34709): Heat-resistant, niobium-stabilized austenitic grade with superior creep strength and resistance to sintering at temperatures exceeding 1000°C (1830°F).
- SAE 314 (UNS S31400): Ultra-high-temperature austenitic grade (up to 1200°C / 2190°F) with exceptional hot strength, designed for the most severe furnace environments.
- SAE 304H (UNS S30409): High-carbon variant of 304 with improved creep rupture properties, suitable for moderate-temperature coil tube applications up to 870°C (1600°F).
Key Mechanical Properties (Typical Values at Room Temperature)
| Property | SAE 310S | SAE 321 | SAE 347H | SAE 314 |
|---|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 520 | ≥ 515 |
| Yield Strength (0.2% offset, MPa) | ≥ 205 | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 40 | ≥ 40 |
| Maximum Continuous Service Temperature (°C) | 1150 | 900 | 1050 | 1200 |
| Thermal Conductivity at 100°C (W/m·K) | 22.2 | 16.3 | 15.9 | 22.7 |
| Linear Expansion Coefficient (20–100°C, 10⁻⁶/K) | 17.3 | 17.1 | 17.0 | 18.0 |
Chemical Composition (Typical, wt%)
| Grade | Cr | Ni | C | Ti / Nb | Si | Fe |
|---|---|---|---|---|---|---|
| 310S | 24.0–26.0 | 19.0–22.0 | ≤ 0.08 | — | ≤ 1.50 | Balance |
| 321 | 17.0–19.0 | 9.0–12.0 | ≤ 0.08 | Ti ≥ 5×C | ≤ 1.00 | Balance |
| 347H | 17.5–19.5 | 9.0–12.0 | 0.04–0.10 | Nb 8–10×C | ≤ 1.00 | Balance |
| 314 | 25.0–30.0 | 33.0–39.0 | ≤ 0.10 | — | ≤ 1.50 | Balance |
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Category | Stainless Steel Coil Tube (盘管 / Coiltube) |
| Item Reference No. | 1174 |
| Tube Form | Continuous spiral coil / Helical coil |
| Outer Diameter (OD) | 10 mm – 108 mm (custom sizes available) |
| Wall Thickness | 0.8 mm – 8.0 mm |
| Coil Diameter | 200 mm – 5000 mm (configurable per application) |
| Coil Length (Uncoiled) | 50 m – 500 m (per coil) |
| Manufacturing Standard | ASTM A213 / ASTM A269 / GB/T 14976 / EN 10216-5 |
| Heat Treatment | Solution annealed (1050–1150°C) followed by water quench |
| Surface Finish | Pickled and passivated (interior and exterior) |
| End Condition | Plain, beveled, or threaded per customer specification |
| Operating Pressure (Typical) | Up to 15 MPa (design-dependent) |
| Operating Temperature Range | –50°C to 1200°C (grade-dependent) |
| Material Grades Available | 304H, 310S, 314, 321, 347H, 347HHT, 660, and custom alloys |
| Test Standards | Hydrostatic test, eddy current testing (ECT), radiographic testing (RT), visual inspection |
| Packaging | Wooden crate or steel frame with moisture-proof wrapping; coil secured with banding |
Manufacturing Process
The production of high-temperature stainless steel coil tubes follows a rigorously controlled multi-stage process to ensure metallurgical integrity, dimensional accuracy, and consistent performance under extreme operating conditions:
- Raw Material Selection and Inspection: High-purity stainless steel wire rod or strip is procured from certified suppliers. Incoming material undergoes spectroscopic chemical analysis, mechanical testing, and ultrasonic examination to verify conformance with specified grades.
- Tube Forming (Piercing or Cold Drawn): For seamless tubes, the hot-rolled billet is pierced on a Mannesmann-type piercer to form a hollow tube blank. Alternatively, cold-drawn tubes are produced by pulling annealed wire through precision dies.
- Heat Treatment (Solution Annealing): Tubes are heated to 1050–1150°C in a controlled-atmosphere furnace to dissolve carbides and restore full austenitic microstructure. Rapid water quenching follows to lock in the desired grain structure and mechanical properties.
- Coil Winding / Spiral Forming: The straight tube is formed into a continuous spiral coil using a precision CNC coil-winding machine. The winding process employs controlled bending forces to prevent plastic deformation, ovality, or micro-cracking at the inner bend radius. The minimum bend diameter is calculated based on material thickness and allowable strain limits.
- Pickling and Passivation: The coiled tube is subjected to an acid pickling bath (typically HNO₃/HF mixture) to remove oxide scales formed during heat treatment. Subsequent passivation with nitric acid establishes a protective chromium oxide film on the surface.
- Non-Destructive Testing (NDT): Eddy current testing verifies wall thickness uniformity and detects surface/sub-surface defects. Hydrostatic pressure testing confirms leak-tightness. Select samples undergo radiographic or ultrasonic examination.
- Dimensional Inspection: Final coils are measured for outer diameter, wall thickness, coil diameter, and total length using calibrated instruments to ensure compliance with tolerance specifications.
- Final Packaging and Documentation: Certified coils are wrapped, strapped, and crated for shipment. Each shipment includes a mill test certificate (MTC), chemical analysis report, and mechanical test data.
Applications
Stainless steel high-temperature coil tubes manufactured by Wenzhou Jixing Metal Materials Co., Ltd. serve a diverse range of critical industrial applications:
- Petrochemical Industry: Superheater and reheater tubes in catalytic cracking units, reformers, and fluid catalytic cracking (FCC) furnaces. The coil configuration enables compact heat exchangers within furnace radiant sections.
- Metallurgical Processing: Coil tubes in annealing furnaces, carburizing furnaces, and heat treatment equipment for steel and alloy processing. Resistance to scaling at elevated temperatures ensures extended campaign life.
- Power Generation: Auxiliary superheater coils in boiler systems, waste heat recovery units, and combined heat and power (CHP) installations.
- Chemical Processing: Reaction coils in continuous-flow reactors, vaporizer coils, and distillation column reboilers handling corrosive process streams.
- Aerospace and Defense: Fuel preheat coils, exhaust gas recirculation (EGR) heat exchangers, and thermal management systems in high-performance engines.
- Food and Pharmaceutical: Sanitary-grade heating coils in pasteurization systems, sterilization equipment, and process heating applications where corrosion resistance and cleanability are paramount.
Case Study Reference — Single-Stage Furnace Superheater Coil Tube Failure Analysis
The product development and quality assurance program has been directly informed by a detailed technical study titled "Damage Analysis of Single-Stage Furnace Superheater Steam High-Temperature Coil Tubes" (《一段炉过热蒸汽高温盘管损坏情况分析》). This investigation identified common failure modes including:
- Creep rupture at tube bends due to localized stress concentration and prolonged exposure above 900°C
- Internal oxidation from steam-side corrosion, particularly in regions of oxygen enrichment
- Thermal fatigue cracking from cyclic temperature fluctuations during start-up and shutdown
- Carbide precipitation at grain boundaries leading to intergranular degradation in non-stabilized grades
These findings directly informed material grade selection (favoring stabilized grades such as 321, 347H, and 310S), coil geometry optimization (increased bend radii to reduce stress concentration), and enhanced quality control protocols (additional eddy current testing at bend regions).
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and holds the following certifications and complies with the following standards:
- ISO 9001:2015 — Quality Management Systems certification ensuring consistent product quality and continuous improvement
- ISO 14001:2015 — Environmental Management Systems certification for sustainable manufacturing practices
- ISO 45001:2018 — Occupational Health and Safety Management Systems
- ASME Section IX — Welding qualification for pressure-vessel applications
- API 5L / API 5CT — Compliance with American Petroleum Institute standards where applicable
- NACE MR0175 / ISO 15156 — Resistance to sulfide stress cracking in sour service environments
- EN 10204 3.1 — Third-party inspection and testing certificates available upon request
- Mill Test Certificates (MTC) — Full chemical analysis, mechanical test results, and heat traceability documentation provided with every shipment
Unique Selling Points
- Field-Informed Design: Product specifications are continuously refined based on real-world failure analysis data from superheater coil tube installations, providing customers with proven reliability rather than theoretical performance claims.
- Wide Grade Selection: Comprehensive inventory of high-temperature austenitic and stabilized stainless steel grades (304H through 314) allows precise material matching to specific temperature, pressure, and corrosion conditions.
- Precision Coil Forming: CNC-controlled spiral winding ensures consistent bend geometry, minimizing stress concentrations and maximizing service life in thermal cycling environments.
- Full Traceability: Each coil is traceable to its original heat number, with complete documentation of chemical composition, mechanical properties, and heat treatment parameters.
- Custom Engineering Support: Technical team available for application-specific coil design, material selection consulting, and failure analysis assistance for existing installations.
- Extended Service Life: Optimized material selection and manufacturing processes deliver 30–50% longer service intervals compared to conventional coil tube solutions, reducing maintenance downtime and total cost of ownership.