Stainless Steel Coil Tube (Coiltube) — Wenzhou Jixing Metal Materials Co., Ltd
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd supplies high-performance Stainless Steel Coil Tubes (also referred to as coiltube or continuous coil tubing) engineered for demanding industrial applications including once-through waste heat boilers, heat exchangers, and high-temperature process systems. These coil tubes are manufactured from austenitic and duplex stainless steel grades, offering superior corrosion resistance, thermal stability, and mechanical integrity under continuous cyclic thermal loading. The product is specifically designed to meet the rigorous demands of waste heat recovery systems, where coil tubes undergo repeated thermal expansion and contraction, making material selection and manufacturing precision critical to long-term service reliability.
Material & Properties
Coil tubes supplied by Wenzhou Jixing Metal Materials are fabricated from the following primary stainless steel grades, each selected based on the specific operating environment:
- SAE 304 / AISI 304 (UNS S30400) — General-purpose austenitic stainless steel offering excellent corrosion resistance in oxidizing environments; suitable for moderate-temperature waste heat applications.
- SAE 316 / AISI 316 (UNS S31600) — Molybdenum-enhanced austenitic grade providing enhanced resistance to pitting and crevice corrosion; recommended for chloride-containing flue gas environments.
- SAE 321 / AISI 321 (UNS S32100) — Titanium-stabilized austenitic grade with superior resistance to intergranular corrosion; ideal for sustained high-temperature service above 450°C.
- SAE 316L / AISI 316L (UNS S31603) — Low-carbon variant of 316 with improved weldability and resistance to sensitization during welding operations.
- SAE 310S / AISI 310S (UNS S31008) — High-temperature austenitic grade with excellent oxidation resistance up to 1150°C; used in extreme-temperature waste heat recovery sections.
- SAE 347H (UNS S34709) — Niobium-stabilized, high-carbon austenitic grade engineered for high-temperature strength and resistance to thermal cycling fatigue.
Key mechanical properties (typical values for cold-drawn coil tubes):
- Tensile Strength (Rm): 520–720 MPa (depending on grade and condition)
- Yield Strength (Rp0.2): 205–350 MPa
- Elongation (A50): ≥ 35%
- Operating Temperature Range: −196°C to 1150°C (grade-dependent)
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | Φ 3.0 mm – Φ 50.8 mm (1/8" – 2") |
| Wall Thickness | 0.25 mm – 5.0 mm |
| Coil Diameter | Φ 200 mm – Φ 1500 mm (adjustable per customer requirement) |
| Coil Length | 5 m – 500 m (continuous coil) |
| Surface Finish | Pickled & Passivated (P&P), 2B, or Custom (Ra ≤ 0.8 μm) |
| Tolerance — OD | ± 0.05 mm (tight tolerance available: ± 0.02 mm) |
| Tolerance — Wall Thickness | ± 10% of nominal |
| Tolerance — Coil Diameter | ± 25 mm |
| Applicable Standards | ASTM A213/A213M, ASME SA-213, EN 10216-5, GB/T 14976 |
| Available Grades | 304, 304L, 316, 316L, 321, 310S, 347H, Duplex 2205 |
| Heat Treatment | Solution Annealed (1050–1150°C) + Water Quenched |
| End Condition | Plain ends, threaded ends, or custom-fabricated connections |
| Winding Mode | Continuous spiral winding (single or double helix) |
Manufacturing Process
The coil tube manufacturing process at Wenzhou Jixing Metal Materials follows a rigorous multi-stage procedure to ensure dimensional accuracy, metallurgical integrity, and corrosion performance:
- Material Selection & Incoming Inspection: Stainless steel strip or seamless pipe stock is sourced from certified mills and subjected to spectroscopic analysis (OES), chemical composition verification, and mechanical property testing prior to processing.
- Forming & Winding: Seamless stainless steel pipe or precision-formed strip is continuously wound onto precision tooling mandrels using CNC-controlled winding machines. The winding parameters (tension, speed, and helix angle) are optimized to prevent work hardening, ovality, and coil spring-back.
- Welding (for strip-formed coil tubes): Where applicable, longitudinal seams are welded using TIG (Gas Tungsten Arc Welding) with inert gas backing (argon or helium) to maintain a fully protected weld root and prevent oxidation.
- Solution Annealing: The formed coil tube is solution-annealed at 1050–1150°C followed by rapid water quenching to dissolve carbides, restore full austenitic microstructure, and maximize corrosion resistance.
- Pickling & Passivation: The annealed coil tube undergoes acid pickling (nitric/hydrofluoric acid blend) to remove oxide scale, followed by passivation treatment to form a protective chromium oxide film on the surface.
- Non-Destructive Testing (NDT): 100% eddy current testing (ECT) and/or ultrasonic testing (UT) is performed to detect internal and surface defects. Helium leak testing or hydrostatic pressure testing is available upon request.
- Final Dimensional Inspection: Outer diameter, wall thickness, coil diameter, and straightness are verified using laser micrometers and coordinate measuring machines (CMM).
- Coiling & Packaging: Finished coil tubes are coiled onto wooden or steel spools, wrapped with protective film or VCI (Volatile Corrosion Inhibitor) paper, and palletized for shipment.
Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials are deployed across a wide range of industrial sectors:
- Waste Heat Boiler Systems (Once-Through Boilers): Coil tubes serve as critical heat transfer surfaces in once-through waste heat recovery boilers, where they absorb high-temperature flue gas energy to generate superheated steam. The continuous coil configuration maximizes heat exchange surface area within compact spatial footprints while accommodating significant thermal expansion through inherent flexibility.
- Process Heat Exchangers: Used in shell-and-coil heat exchangers for chemical, petrochemical, and pharmaceutical processing where precise temperature control and corrosion resistance are essential.
- Industrial Furnace Heating Elements: Deployed as heating coils in industrial furnaces, kilns, and drying ovens operating at elevated temperatures.
- Automotive & Aerospace Systems: Applied in turbocharger exhaust manifolds, hydraulic lines, and fuel delivery systems requiring high-temperature and high-pressure resistance.
- Food & Beverage Processing: Utilized in sanitary-grade heat exchangers and pasteurization systems where hygienic surface finish and corrosion resistance are mandatory.
- Power Generation: Installed in waste heat recovery units (WHRU) for combined cycle power plants, recovering exhaust energy from gas turbines to improve overall plant thermal efficiency.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications to ensure product reliability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and quality assurance processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health & Safety Management System certification.
- NADCAP (Special Process Certification) — Available for aerospace-grade coil tube production involving welding and heat treatment processes.
- Mill Test Reports (MTR) / EN 10204 3.1 Certificates — Provided with every shipment, documenting chemical composition, mechanical properties, and NDT results.
- ASME "U" Stamp Certification — Available for pressure vessel and boiler applications requiring ASME code compliance.
- Third-Party Inspection (TPI) — SGS, BV (Bureau Veritas), and TÜV inspection services available upon customer request for on-site manufacturing surveillance.
Unique Selling Points
1. Specialized Waste Heat Boiler Expertise: Wenzhou Jixing Metal Materials possesses deep technical experience in coil tube design and modification for once-through waste heat boilers, with documented case studies demonstrating improved thermal efficiency and extended service life following coil tube retrofitting programs.
2. Custom Coil Geometry: The company offers fully customizable coil tube geometries — including variable helix pitch, multi-helix configurations, and transition sections — to optimize heat transfer performance and fit within constrained installation envelopes.
3. Full Traceability: Every coil tube batch is traceable from raw material mill certificate through final shipment, with digital records maintained for quality assurance and regulatory audit purposes.
4. Rapid Prototyping & Modification Services: Leveraging CNC winding capabilities and rapid turnaround production lines, the company supports fast prototyping cycles and in-service coil tube modification/replacement programs for existing waste heat boiler installations.
5. Grade Flexibility: A broad portfolio of stainless steel grades — from standard austenitic (304/316) to high-temperature (310S/347H) and duplex (2205) grades — enables optimal material selection tailored to specific operating conditions, maximizing both performance and cost-effectiveness.
Technical Notes on Coil Tube Modification in Once-Through Waste Heat Boilers
Based on engineering studies conducted and documented by Wenzhou Jixing Metal Materials, coil tube modification in once-through waste heat boilers addresses several critical performance challenges:
- Thermal Stress Mitigation: Optimized coil geometry (helix pitch, coil diameter, and transition curvature) distributes thermal expansion stresses more uniformly, reducing localized fatigue failure points at tube supports and bends.
- Flow Distribution Optimization: Modified coil tube configurations improve fluid distribution across heat transfer surfaces, preventing flow maldistribution that leads to localized overheating and accelerated oxidation.
- Material Upgrading: Replacement of legacy carbon steel or low-alloy coil tubes with austenitic stainless steel (321/347H) extends service intervals from 6–12 months to 3–5 years in aggressive flue gas environments.
- Heat Transfer Enhancement: Advanced coil tube surface treatments and geometric modifications (e.g., internal helical inserts or external fins) can improve heat transfer coefficients by 15–30% without increasing pumping power.
These modification strategies represent a cost-effective alternative to full boiler replacement, with typical return on investment (ROI) achieved within 12–18 months through improved thermal efficiency and reduced unplanned downtime.