Stainless Steel Coil Tube (Coil Tube) — Boiler & Heat Exchanger Grade
Product Overview
The Stainless Steel Coil Tube, catalogued as product No. 1351 by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered continuous coil-form stainless steel tube specifically designed for high-temperature, high-pressure environments in boiler systems, heat exchangers, condensers, and process heating applications. Unlike straight-length seamless or welded tubes, coil tubes are delivered in continuous helical or spiral-wound configurations, enabling uninterrupted installation in serpentine and coiled heat-transfer geometries without the need for field welding at every bend.
This product line addresses critical operational challenges identified in industrial maintenance literature, particularly the issue of boiler coil tube blockage (阻塞), which arises from internal fouling, scale deposition, corrosion product accumulation, and flow-induced mechanical deformation. The design philosophy of this coil tube integrates anti-fouling surface treatments, optimized wall thickness tolerances, and corrosion-resistant alloy compositions to minimize blockage risk and extend service intervals.
Material & Properties
Wenzhou Jixing Metal Materials Co., Ltd. offers multiple stainless steel grades for coil tube production, each selected based on the thermal, chemical, and mechanical demands of the target application:
- SUS304 (AISI 304 / 06Cr19Ni10) — General-purpose austenitic stainless steel with excellent corrosion resistance in oxidizing environments, suitable for moderate-temperature boiler feedwater systems and condensate recovery loops.
- SUS316L (AISI 316L / 022Cr17Ni12Mo2) — Low-carbon variant with molybdenum addition, providing superior resistance to pitting and crevice corrosion in chloride-containing process waters and marine boiler applications.
- SUS321 (AISI 321 / 06Cr18Ni11Ti) — Titanium-stabilized austenitic grade offering enhanced resistance to intergranular corrosion at elevated temperatures (450–850 °C), ideal for superheater and reheater coil sections.
- SUS310S (AISI 310S / 06Cr25Ni20) — High-temperature grade with outstanding oxidation resistance up to 1150 °C, employed in furnace tubes, radiant coil sections, and waste-heat recovery boilers.
- Duplex 2205 (UNS S31803) — Duplex austenitic-ferritic stainless steel providing approximately twice the yield strength of 304/316 grades, with excellent resistance to stress corrosion cracking (SCC) and erosion-corrosion in aggressive boiler environments.
Key Mechanical Properties (Typical, Annealed Condition):
- Tensile Strength (Rm): 520–720 MPa (depending on grade and wall thickness)
- Yield Strength (Rp0.2): 205–450 MPa
- Elongation (A5): ≥ 40% (SUS304), ≥ 35% (SUS316L)
- Hardness: ≤ 217 HB (annealed, SUS304)
- Maximum Service Temperature: Up to 870 °C (SUS304), 1150 °C (SUS310S)
- Minimum Cryogenic Temperature: −196 °C (all austenitic grades)
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 114.3 mm (¼″ – 4½″) | ASTM A213 / GB/T 12771 |
| Wall Thickness (WT) | 0.5 mm – 6.0 mm | ASTM A213 / GB/T 12771 |
| Coil Winding Diameter (CD) | 100 mm – 1000 mm (customizable) | Manufacturer Specification |
| Coil Length per Spool | 30 m – 500 m (continuous, spooled) | Manufacturer Specification |
| Material Grades | SUS304, SUS316L, SUS321, SUS310S, 2205 Duplex | ASTM A213 / EN 10216-5 |
| Surface Finish | 2B, BA (Bright Annealed), Pickled & Passivated, Electropolished | ASTM A478 / GB/T 4237 |
| End Condition | Plain, Beveled (15°/37°), Threaded (optional) | ASME B16.11 / Manufacturer Spec. |
| Pressure Rating | Up to 42.0 MPa (6075 psi) at 25 °C (grade-dependent) | ASME B31.3 / EN 13480 |
| Temperature Range | −196 °C to +1150 °C (grade-dependent) | ASTM A213 |
| Manufacturing Method | Seamless (Hot/Forged) or Precision-Welded (ERW/ODW) | ASTM A213 / GB/T 14976 |
| Dimensional Tolerance | ± 0.05 mm (OD), ± 5% (WT) — Precision Grade | GB/T 12771 Class 1 |
| Coil Tolerance | ± 2% on coil length; ± 5 mm on winding diameter | Manufacturer Specification |
| Packaging | Wooden spool + protective wrapping + moisture-absorbent desiccant | ISO 4180 / Manufacturer Spec. |
Manufacturing Process
The production of Wenzhou Jixing's stainless steel coil tubes follows a rigorously controlled multi-stage process designed to ensure dimensional accuracy, metallurgical integrity, and corrosion resistance:
- Raw Material Selection & Ingot Casting — Virgin nickel, chromium, and iron are alloyed under vacuum-induction melting (VIM) or arc-furnace conditions. Each heat lot undergoes spectrographic analysis to confirm chemical composition within ASTM/GB tolerance limits.
- Hot Rolling / Billet Forging — For seamless variants, the ingot is reheated to 1150–1200 °C and pierced through a mandrel in an upset-forging press or rotary piercing mill to produce a hollow billet (furnace tube / HT). For welded variants, cold-rolled strip is slit and formed.
- Cold Drawing & Elongation — The hot-forged tube is cold-drawn through a series of dies with tungsten carbide (WC) tooling to achieve the target OD, wall thickness, and surface finish. Multi-pass drawing ensures uniform microstructure and eliminates surface defects.
- Intermediate Annealing & Pickling — Tubes undergoing multiple cold-working passes are intermediately annealed at 1050–1100 °C in a protective atmosphere (endothermic gas or vacuum) to relieve cold-work hardening and restore ductility. Subsequent acid pickling (HNO₃ + HF blend) removes scale and oxide layers.
- Coil Winding (Coiling) — The straight tube is wound onto a precision CNC-controlled coiling head at a constant winding diameter. The winding speed and tension are dynamically adjusted to prevent ovalization, kinking, or inter-coil contact damage. Each coil is verified for dimensional consistency.
- Final Annealing & Passivation — The coiled tube undergoes a final solution anneal and passivation treatment to restore full corrosion resistance. Bright annealing (BA) in a controlled-atmosphere furnace produces a low-roughness (Ra ≤ 0.5 μm) surface suitable for hygienic and fouling-sensitive applications.
- Non-Destructive Testing (NDT) — Every coil is subjected to electromagnetic (Eddy Current, EC) inspection in accordance with ASTM E309 or ASTM E709 to detect internal and external defects. Hydrostatic pressure testing (ASTM A269) verifies weld integrity for welded variants and wall soundness for seamless tubes.
- Final Inspection & Packaging — Dimensional verification, surface quality assessment, and material traceability documentation are completed. Each coil is individually wrapped, placed on a protective wooden spool, and labeled with a heat-number traceability tag.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. is engineered for demanding thermal-fluid processing environments. Primary application domains include:
- Industrial Boiler Systems — Superheater tubes, reheater coils, economizer elements, and radiant heating coils in utility boilers, waste-heat recovery boilers (WHRB), and package boilers. The continuous coil form eliminates field-welded joints that are common failure points for blockage and leakage.
- Heat Exchangers & Condensers — Serpentine coil assemblies in air-cooled heat exchangers, shell-and-coil condensers, and process cooling loops where internal flow geometry demands smooth, continuous bends.
- Power Generation — Feedwater heaters, low-pressure and high-pressure turbine exhaust coolers, and auxiliary heating circuits in thermal and combined-cycle power plants.
- Chemical & Petrochemical Processing — Reaction coil heaters, distillation column reboilers, and heat integration networks in refineries and petrochemical complexes where chloride-resistant grades (316L, 2205) are essential.
- Food & Pharmaceutical Industry — CIP (Clean-In-Place) compatible heating coils in hygienic process equipment, where electropolished BA surfaces minimize product residue and bacterial adhesion.
- Marine & Offshore — Boiler feedwater coils, seawater cooling loops, and exhaust gas economizers on marine vessels and offshore platforms, leveraging the corrosion resistance of duplex and 316L grades.
Addressing Boiler Coil Tube Blockage
Based on field maintenance experience documented in 《锅炉盘管阻塞的检修》 (Boiler Coil Tube Blockage Inspection & Repair), the following engineering measures are incorporated into the design and manufacturing of this product to mitigate blockage risk:
- Optimized Internal Surface Finish — BA (Bright Annealed) or electropolished finishes with Ra ≤ 0.4 μm reduce frictional resistance and inhibit scale adhesion, directly addressing the root cause of flow-restrictive deposits that lead to blockage.
- Tight Wall Thickness Tolerance — Precision drawing to ± 5% wall tolerance ensures uniform flow cross-section, preventing localized flow stagnation zones where particulate accumulation initiates blockage.
- Corrosion-Resistant Alloy Selection — 316L and 2205 grades resist the pitting and intergranular corrosion that generates oxide debris, a primary contributor to progressive coil tube clogging in boiler systems.
- Continuous Coil Form — By eliminating intermediate weld joints, the continuous coil design removes the most common sites of internal weld-metal buildup and crevice corrosion that accelerate blockage formation.
- Passivation Treatment — Final chemical passivation forms a stable Cr₂O₃ passive film, reducing the rate of corrosion-product generation by up to 80% compared to untreated surfaces.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and certification frameworks to assure product conformance:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — Certified for design, manufacturing, and supply of metal products |
| ISO 14001:2015 | Environmental Management System — Covers manufacturing waste, emissions, and sustainable sourcing |
| ISO 45001:2018 | Occupational Health & Safety Management System |
| ASTM A213 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for High-temperature Service |
| GB/T 12771 | Chinese National Standard — Welded Stainless Steel Tubes for General Applications |
| GB/T 14976 | Chinese National Standard — Seamless Stainless Steel Tubes for Fluid Transport |
| EN 10216-5 | European Standard — Non-alloy and Alloy Steel Tubes for Pressure Purposes (Stainless Steel) |
| ASME SA-213 / SA-269 | American Society of Mechanical Engineers — Seamless and Welded Austenitic Tubes for Boilers and Heat Exchangers |
| NACE MR0175 / ISO 15156 | Materials for Use in H₂S-Containing Environments in Oil and Gas Production (applicable to 2205 grade) |
| Mill Test Certificates (MTC) | EN 10204 Type 3.1 — Full material traceability with heat-number-linked chemical and mechanical test data |
Unique Selling Points
- Blockage-Resistant Design Heritage — Product specifications are informed by documented field experience in boiler coil tube blockage inspection and repair, translating real-world failure analysis into preventive design features including superior surface finish, tight dimensional tolerances, and corrosion-resistant alloy selection.
- Continuous Spool Delivery — Delivered as continuous coils (up to 500 m per spool), enabling installation of long, uninterrupted serpentine assemblies without field welding — reducing failure points by up to 90% compared to straight-tube-and-tee-joint configurations.
- Multi-Grade Flexibility — Five stainless steel grades available from a single supplier, covering service temperatures from −196 °C to +1150 °C and corrosion environments from atmospheric to chloride-laden.
- Full Traceability — Every coil is accompanied by EN 10204 Type 3.1 Mill Test Certificates with heat-number-linked chemical composition, mechanical test results, NDT reports, and dimensional inspection records.
- Precision Coiling Technology — CNC-controlled coiling ensures consistent winding diameter (± 5 mm), uniform inter-coil spacing, and zero kinking — critical for downstream automated installation and heat-transfer performance