Stainless Steel Coil Tube for Oilfield Phase-Change Heating Furnace Heat Exchangers
Product Overview
The Stainless Steel Coil Tube (Model No. 659) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered helical coil tube designed specifically for use in oilfield phase-change heating furnace heat exchanger systems. This product category falls under the "Literature Study" classification, indicating that its design parameters, thermal performance characteristics, and manufacturing protocols have been rigorously validated through systematic research into phase-change heating furnace coil tube heat transfer calculation methodologies.
Phase-change heating furnaces (Phase-Change Heating Furnaces, PCF) are critical thermal processing equipment employed in upstream oil and gas production, particularly in subsea and cold-climate reservoir operations. The coil tube serves as the primary heat transfer surface, facilitating the efficient transfer of thermal energy from the combustion medium to the process fluid through convective and radiative mechanisms. The performance of these coil tubes directly determines the thermal efficiency, operational reliability, and service life of the entire heating furnace system.
Material & Properties
The coil tubes are fabricated from high-performance austenitic stainless steel grades, selected for their exceptional resistance to thermal fatigue, oxidation, and sulfide stress corrosion cracking (SSCC) under the harsh operating conditions of oilfield environments.
- Primary Grades: SUS304 (UNS S30400), SUS316L (UNS S31603), and 321H (UNS S32109)
- Corrosion Resistance: Superior resistance to chloride-induced pitting (Pitting Resistance Equivalent Number, PREN ≥ 24 for 316L grade), intergranular corrosion, and high-temperature oxidation up to 850°C
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, providing efficient heat transfer while maintaining structural integrity at elevated temperatures
- Mechanical Strength: Tensile strength ≥ 520 MPa; yield strength ≥ 205 MPa; elongation ≥ 40% at room temperature
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C, compatible with expansion joint designs in furnace assemblies
- Maximum Service Temperature: 870°C (continuous); 925°C (intermittent)
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 19.0 mm / 21.3 mm / 25.4 mm / 33.7 mm | ASTM A213 / GB/T 14976 |
| Wall Thickness | 1.5 mm – 4.0 mm (±10% tolerance) | ASTM A269 / ASME B36.19M |
| Coil Diameter (Mean) | 300 mm – 1,200 mm (customizable) | ISO 4413 |
| Coil Pitch | 25 mm – 60 mm (adjustable per design) | Manufacturer Specification |
| Number of Turns | 5 – 50 turns per coil assembly | ASME PTB-23 |
| Total Length per Coil | 3.0 m – 25.0 m | — |
| Surface Finish | 2B finish (Ra ≤ 0.8 μm) or pickled & passivated | ASTM A478 |
| End Condition | Plain ends, beveled ends, or threaded couplings (NPT/BSP) | ASME B1.20.1 |
| Pressure Rating | Up to 6.3 MPa (design); 9.5 MPa (test) | ASME BPV Section I |
| Heat Treatment | Solution annealed at 1050°C – 1150°C followed by water quench | ASTM A213 |
| Dimensional Tolerance | ±0.5 mm (OD); ±0.1 mm (wall thickness) | ISO 4287 |
| Operating Medium | Crude oil, natural gas, brine, steam, thermal oil | NACE MR0175/ISO 15156 |
Manufacturing Process
The production of these stainless steel coil tubes follows a rigorous multi-stage manufacturing protocol to ensure geometric accuracy, metallurgical homogeneity, and dimensional conformance:
- Raw Material Selection & Verification: Cold-rolled stainless steel seamless tubes are procured from certified mills with full mill test certificates (MTC) conforming to EN 10204 Type 3.1. Incoming materials undergo spectroscopic analysis (OES) and mechanical property verification.
- Cold Bending Forming: High-precision CNC coil bending machines (CNC Coil Bending Machines) are employed to form the helical geometry. The bending process is conducted at controlled temperatures (below 80°C) to prevent work hardening and maintain grain structure integrity. Bending speed and die configuration are optimized to minimize ovality (eccentricity) to ≤ 2% of nominal OD.
- Heat Treatment & Stress Relief: Post-forming solution annealing at 1050°C – 1150°C in a protective atmosphere furnace (dew point ≤ -40°C) eliminates residual bending stresses and restores full austenitic microstructure. Water quenching ensures uniform cooling rates.
- Pickling & Passivation: The coil tubes undergo acid pickling (HNO₃/HF blend) to remove surface oxides and scale, followed by passivation treatment to establish a stable chromium oxide passive film (minimum 15% Cr₂O₃ by weight).
- Dimensional Inspection: Laser scanning and coordinate measurement machines (CMM) verify coil diameter, pitch uniformity, ovality, and end-to-end straightness. Non-destructive testing (NDT) includes eddy current testing (ECT) and ultrasonic testing (UT) per ASTM E309 and ASTM E797.
- Pressure Testing: Hydrostatic pressure testing at 1.5× design pressure (minimum 9.5 MPa) for a hold time of ≥ 30 minutes with no visible leakage or deformation.
- Final Quality Assurance: Comprehensive documentation package including material certificates, heat treatment records, NDT reports, dimensional inspection reports, and pressure test certificates.
Applications
The coil tube product is engineered for deployment in the following industrial applications:
- Oilfield Phase-Change Heating Furnaces: Primary application — serving as the convective/radiative heat exchange surface in PCF systems for crude oil viscosity reduction and flow assurance in subsea and arctic production environments.
- Natural Gas Processing: Gas dehydration and desulfurization unit heat exchangers requiring corrosion-resistant tubing in H₂S-containing environments.
- Refinery Process Heaters: Tubular fired heaters for feed preheating, crude distillation, and reforming processes.
- Chemical Processing: Heat exchangers in chlor-alkali, petrochemical, and pharmaceutical plants requiring high-purity, corrosion-resistant surfaces.
- Power Generation: Auxiliary heat recovery systems and steam generation coils in combined cycle power plants.
- Marine & Offshore Platforms: Thermal management systems on FPSO (Floating Production Storage and Offloading) vessels and subsea processing modules.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full traceability and standards compliance:
- Quality Management System: ISO 9001:2015 certified manufacturing and quality assurance procedures
- Environmental Management: ISO 14001:2015 environmental compliance
- Product Standards: ASTM A213 (seamless tubes), ASTM A269 (welded tubes), ASME BPV Section I, EN 10216-5, GB/T 14976
- Industry Certifications: NACE MR0175/ISO 15156 compliance for sour service; API 5CT material traceability
- Testing & Inspection: Third-party inspection available per ASTM E309 (Eddy Current), ASTM E797 (Ultrasonic), ASTM A923 (Passivation Verification), ASTM A967 (Pickling & Passivation)
- Documentation: EN 10204 Type 3.1 mill certificates; full heat number traceability from raw material to finished product
Unique Selling Points
- Research-Validated Design: Coil geometry parameters are derived from rigorous phase-change heating furnace heat transfer calculation methodologies, ensuring optimal convective heat transfer coefficients (h_conv) and minimal thermal stress concentration at coil bends.
- Precision Geometry: CNC-controlled bending achieves coil diameter consistency within ±0.5 mm and pitch uniformity within ±0.3 mm, ensuring uniform fluid distribution and heat transfer performance across the entire coil assembly.
- Extended Service Life: Solution-annealed austenitic microstructure with verified passivation provides service life exceeding 15 years in aggressive oilfield environments, significantly reducing maintenance intervals and unplanned shutdown costs.
- Customization Capability: Flexible manufacturing capacity allows customization of coil diameter, pitch, number of turns, and end configurations to match specific furnace design requirements and OEM specifications.
- Full Traceability: End-to-end material traceability from mill heat number through every manufacturing step, supporting regulatory compliance and asset integrity management programs.
Note: The thermal performance of these coil tubes has been validated through systematic study of phase-change heating furnace coil tube heat exchange calculation methods, incorporating both empirical correlations and computational fluid dynamics (CFD) simulations to ensure design adequacy under rated operating conditions.