Stainless Steel Spiral Coil Tube — Coiltube (Model: JX-CT Series)
1. Product Overview
The Stainless Steel Spiral Coil Tube (commonly referred to as Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous-length tubular product formed in a helical or spiral configuration. This product category encompasses both spiral wound coil tubes and coiled straight tubes produced from austenitic and ferritic stainless steel grades, designed for high-temperature process heat exchange, fluid conveyance, and structural applications in the petrochemical, power generation, and industrial heating sectors.
The spiral coil geometry is integral to the product's function in Spiral Coil Water Jacket Furnaces (螺旋盘管水套炉), where the coil tube serves as a critical heat transfer element within the combustion chamber wall. The continuous helical winding enables uniform thermal distribution, efficient heat absorption, and mechanical resilience under cyclic thermal loading conditions.
Unique Selling Points
- Continuous Helical Geometry: Eliminates weld joints along the tube length, significantly reducing leakage risk and enhancing structural integrity under high-temperature and high-pressure operating conditions.
- Optimized Thermal Performance: The spiral configuration maximizes the surface-area-to-volume ratio, facilitating superior convective and radiative heat transfer within water jacket furnace systems.
- Full-Length Traceability: Each coil is individually batch-traced from raw material mill certificates through final inspection, ensuring complete material pedigree documentation.
- Multi-Grade Availability: Compatible with a broad spectrum of stainless steel grades including 304, 304L, 316, 316L, 321, 347, and 904L, accommodating diverse corrosion and temperature environments.
2. Material & Properties
2.1 Applicable Material Grades
The Coiltube product line is manufactured from the following primary stainless steel grades, conforming to international standards:
- Austenitic Grades: AISI 304 / 304L (UNS S30400 / S30403), AISI 316 / 316L (UNS S31600 / S31603), AISI 321 (UNS S32100), AISI 347 (UNS S34700)
- Super-Austenitic Grades: AISI 904L (UNS N08904), Alloy 20 (UNS N08200)
- Ferritic Grades: AISI 430 (UNS S43000), AISI 441 (UNS S44100)
- Duplex Grades: UNS S31803 (2205), UNS S32750 (2507)
2.2 Mechanical Properties (Typical — Austenitic Grade 304/316)
| Property | Unit | Minimum Value | Test Standard |
|---|---|---|---|
| Tensile Strength (Rm) | MPa | ≥ 520 | ASTM A269 / EN 10216-5 |
| Yield Strength (Rp0.2) | MPa | ≥ 205 | ASTM A269 / EN 10216-5 |
| Elongation (A5) | % | ≥ 40 | ASTM A269 / EN 10216-5 |
| Hardness (HV) | — | ≤ 210 | ASTM A269 |
| Impact Energy (20°C) | J | ≥ 300 | ISO 148-1 |
| Impact Energy (−196°C / LN₂) | J | ≥ 270 | ASTM A370 |
2.3 Physical Properties
- Density: 7.93 g/cm³ (typical for austenitic grades)
- Thermal Conductivity (25°C): 16.3 W/(m·K) — Grade 304
- Thermal Conductivity (500°C): 26.7 W/(m·K) — Grade 304
- Coefficient of Thermal Expansion (20–800°C): 17.2 × 10⁻⁶ /K
- Specific Heat (25–800°C): 0.50 kJ/(kg·K)
- Maximum Service Temperature: 870°C (Grade 304), 870°C (Grade 316), 1093°C (Grade 321/347)
2.4 Corrosion Resistance
The selected material grades provide exceptional resistance to:
- General Corrosion: Atmospheric, freshwater, and dilute acid environments
- Pitting and Crevice Corrosion: Chloride-containing environments (particularly Grades 316, 316L, 904L)
- Intergranular Corrosion (IGC): Resistant after welding, especially low-carbon grades (304L, 316L)
- Stress Corrosion Cracking (SCC): Austenitic grades with ≤ 0.03% carbon demonstrate superior SCC resistance in chloride media
- Oxidation Resistance: Continuous service up to 870°C with minimal scale formation
3. Specifications
3.1 Dimensional Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 219.1 mm (¼" – 8") | ASTM A269 / EN 10216-5 |
| Wall Thickness (WT) | 0.5 mm – 12.0 mm | ASTM A269 |
| Coil Inner Diameter (CID) | 150 mm – 1,200 mm (adjustable per order) | Customer specification |
| Coil Length per Spool | 50 m – 500 m (continuous) | — |
| Helix Pitch (for spiral coil) | 50 mm – 300 mm | Customer specification |
| Spiral Diameter | 200 mm – 2,500 mm | Customer specification |
| Tolerance — OD | ± 0.05 mm (precision), ± 0.10 mm (standard) | ASTM A269 |
| Tolerance — WT | ± 10% of nominal | ASTM A269 |
| Surface Finish | Bright annealed (BA), No. 4 brushed, 2B, matte | ASTM A480 |
| End Form | Plain, beveled, threaded, or cut-to-length | Customer specification |
3.2 Applicable Standards
- ASTM A269 / A269M: Standard Specification for Seamless Austenitic Stainless Steel Tubing for Chemical and Heat-Transfer Service
- ASTM A778 / A778M: Standard Specification for Seamless Ferritic and Martensitic Stainless Steel Tubing
- EN 10216-5: Metallic Heat-Exchanger Tubes and Heat-Transfer Tubes — Non-ferrous metallic tubes — Part 5: Austenitic stainless steel tubes
- ISO 11431: Metallic Heat-Exchanger Tubes and Heat-Transfer Tubes — Non-ferrous metallic tubes
- GB/T 12771: Chinese National Standard for Stainless Steel Tubes for General Purposes
- ASME B36.19M: Welded and Seamless Wrought Stainless Steel Pipe
4. Manufacturing Process
4.1 Process Flow
- Raw Material Procurement: Seamless stainless steel tube blanks sourced from certified mills (e.g., Outokumpu, Sandvik, POSCO, Tsingshan) with full mill test certificates (MTC) conforming to EN 10204 Type 3.1.
- Incoming Inspection: Visual examination, dimensional verification, chemical composition analysis (OES — Optical Emission Spectroscopy), and mechanical property testing on sample coupons.
- Coil Forming (Straight Coiltube): The straight tube is fed through a precision coil former with controlled bending radius (minimum R ≥ 5D, where D = outer diameter) to prevent wall thinning and ovality exceeding 1% of OD.
- Spiral Winding (Spiral Coil): For spiral coil configurations, the tube is helically wound around a mandrel with controlled pitch and diameter using CNC-guided winding equipment. The winding angle is maintained within ± 1° of the design specification.
- Post-Forming Annealing (if required): Tubes exhibiting cold work exceeding 5% may undergo solution annealing at 1050–1150°C followed by rapid water quenching to restore full austenitic microstructure and corrosion resistance.
- Surface Treatment: Pickling and passivation (acid pickling with HNO₃/HF mixture followed by passivation treatment) to remove scale and form a protective chromium oxide layer (≥ 1000 ppm FeCl₃ test compliance).
- Final Inspection: Dimensional verification (OD, WT, coil diameter, pitch), surface quality inspection, hydrostatic or pneumatic pressure testing, and magnetic particle testing (MT) or eddy current testing (ET) for surface defect detection.
- Packaging and Dispatch: Coils are wrapped with moisture-proof protective film, secured with steel strapping, and loaded onto wooden or steel pallets for export or domestic delivery.
4.2 Key Process Controls
- Bending Radius Control: Minimum bending radius of 5D ensures wall thickness reduction does not exceed 8% of nominal WT.
- Ovality Control: Maximum allowable ovality is 1.5% of OD for standard applications and ≤ 1.0% for precision applications.
- Springback Compensation: CNC controllers compensate for elastic springback during coil forming to maintain dimensional accuracy within specified tolerances.
- Thermal Cycling Simulation: Spiral coils for water jacket furnace applications undergo thermal cycling tests (10–50 cycles between 20°C and operating temperature) to verify fatigue resistance.
5. Applications
5.1 Primary Application Domains
- Spiral Coil Water Jacket Furnaces (螺旋盘管水套炉): The primary application domain. The stainless steel coil tube forms the heat-absorbing element within the furnace water jacket, converting combustion energy into process steam or hot water. The spiral geometry ensures uniform heat distribution and prevents localized overheating.
- Industrial Boilers and Heat Exchangers: Used as tube elements in shell-and-tube heat exchangers, steam generators, and waste heat recovery systems.
- Petrochemical Processing: Heat transfer coils in distillation columns, reforming furnaces, and catalytic cracking units where resistance to sulfidation and carburization is required.
- Power Generation: Superheater and reheater coils in coal-fired and gas-fired power plants, operating at temperatures up to 600°C.
- Food and Pharmaceutical Processing: Sanitary-grade heat transfer coils in pasteurization, sterilization, and cooking systems (Grade 316L with electropolished finish).
- Marine and Offshore Engineering: Seawater cooling coils and ballast water treatment heat exchangers requiring resistance to chloride-induced pitting corrosion.
- Chemical Processing: Reactor jacket coils, distillation column internals, and process heating/cooling systems handling aggressive chemical media.
5.2 Performance in Water Jacket Furnace Systems
In a Spiral Coil Water Jacket Furnace, the stainless steel coil tube serves as the primary heat exchange surface. Combustion gases at temperatures ranging from 800°C to 1,200°C flow across the exterior of the spiral coil, while water or steam flows through the tube interior. The continuous helical winding provides:
- Uniform heat flux distribution along the furnace height
- Reduced thermal stress concentration compared to straight tube configurations
- Self-supporting structural geometry requiring minimal external supports
- Facilitated maintenance through modular coil spool replacement
6. Quality Certifications
6.1 Company-Level Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
- EN 10204 Type 3.1 — Inspection Documents (Material Test Certificates)
- CE Marking — Conformity with European Pressure Equipment Directive (PED 2014/68/EU)
6.2 Product-Level Certifications and Testing
- Mill Test Certificates (MTC): Each batch accompanied by EN 10204 3.1 certified material documentation including chemical analysis, mechanical test results, and heat treatment records.
- Non-Destructive Testing (NDT): Eddy Current Testing (ECT) per ASTM E309 for surface defect detection; Magnetic Particle Testing (MT) per ASTM E709