Stainless Steel Coil Tube (Coiltube) — Oil Field Heater Application Series
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous-length tubular product designed specifically for high-temperature, high-pressure, and corrosive environments encountered in oil and gas field operations. Unlike conventional straight-length stainless steel pipes, coil tubes are produced in continuous helical or spiral wound configurations, enabling seamless installation in compact heat exchanger assemblies, fired heater tubes, and process piping systems where space constraints and thermal cycling demands are critical design considerations.
This product line is particularly distinguished by its compatibility with CNC Pulse Cleaning Technology (Computer Numerical Control Pulse Cleaning Technology), a non-destructive internal cleaning methodology that has been successfully applied to oil field heater coil tube maintenance. This integration ensures long-term operational reliability, extended service life, and minimized downtime in upstream and midstream processing facilities.
Material & Properties
Base Alloy Composition
The coil tubes are fabricated from austenitic stainless steel grades conforming to international standards, with primary options including:
- AISI 304 / 304L (UNS S30400 / S30403) — General-purpose corrosion resistance; low carbon variant (304L) for weldability and intergranular corrosion resistance.
- AISI 316 / 316L (UNS S31600 / S31603) — Enhanced pitting and crevice corrosion resistance due to molybdenum (Mo) addition; preferred for chlorinated environments.
- AISI 321 (UNS S32100) — Titanium-stabilized grade offering superior resistance to intergranular corrosion at elevated temperatures (up to 870°C / 1600°F).
- AISI 347 (UNS S34700) — Niobium-stabilized alternative for high-temperature service with excellent oxidation resistance.
Mechanical Properties
| Property | AISI 304 | AISI 316 | AISI 321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 515 |
| Yield Strength (0.2% Offset) (MPa) | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation at Break (%) | ≥ 40 | ≥ 35 | ≥ 35 |
| Maximum Service Temperature (°C) | 870 | 870 | 980 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 16.3 | 16.3 |
| Density (g/cm³) | 8.0 | 8.0 | 8.0 |
Chemical Composition (Typical, wt%)
| Element | 304/304L | 316/316L | 321 |
|---|---|---|---|
| C (Carbon) | ≤ 0.08 / ≤ 0.03 | ≤ 0.08 / ≤ 0.03 | ≤ 0.08 |
| Cr (Chromium) | 18.0 – 20.0 | 16.0 – 18.0 | 17.0 – 19.0 |
| Ni (Nickel) | 8.0 – 10.5 | 10.0 – 14.0 | 9.0 – 12.0 |
| Mo (Molybdenum) | — | 2.0 – 3.0 | — |
| Ti (Titanium) | — | — | 5 × C – 0.70 |
| P (Phosphorus) | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 |
| S (Sulfur) | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 |
Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) |
| Outer Diameter (OD) | 6.35 mm – 114.3 mm (¼" – 4½") |
| Wall Thickness | 0.50 mm – 6.35 mm (0.020" – ¼") |
| Coil Diameter (Helical) | Standard: 1.5 m – 6.0 m; Custom upon request |
| Tube Length per Coil | 100 m – 2,000 m (continuous) |
| Surface Finish | Pickled & Passivated (P&P); Mirror Polished (Ra ≤ 0.4 μm); Bead Blasted |
| Tolerance on OD | ± 0.10 mm (standard); ± 0.05 mm (precision) |
| Tolerance on Wall Thickness | ± 10% (standard); ± 5% (precision) |
| Applicable Standards | ASTM A269, ASTM A213, ASME SA-213, EN 10216-5, GB/T 12771, JIS G3459 |
| Manufacturing Method | Hot Rolled / Cold Drawn (Cold Worked) |
| Packaging | Wooden pallet with moisture-proof wrapping; export-grade crate for international shipment |
Manufacturing Process
- Raw Material Selection — High-purity stainless steel strip or seamless pipe blank sourced from certified mills, subjected to spectroscopic analysis (OES) and chemical verification to ensure grade compliance.
- Hot Rolling or Cold Forming — For larger diameters, seamless pipe is hot-rolled through a continuous mill. For precision small-diameter tubes, cold drawing is employed through multi-stage die reduction to achieve tight dimensional tolerances and superior surface integrity.
- Heat Treatment (Solution Annealing) — Tubes are annealed in a controlled atmosphere furnace at 1050°C – 1150°C, followed by rapid quenching to dissolve carbides and restore full austenitic microstructure, ensuring maximum corrosion resistance and ductility.
- Pickling & Passivation — Removal of oxide scale through hydrofluoric/nitric acid pickling, followed by passivation treatment to establish a stable chromium oxide passive film on the tube surface.
- Coil Winding — The continuous tube is wound onto precision-machined winding reels using CNC-controlled coil winding machinery to maintain uniform bend radius, prevent tube ovality, and ensure consistent coil geometry.
- Hydrostatic Pressure Testing — Each coil is subjected to hydrostatic testing at 1.5 × maximum design pressure (per ASTM A269) to verify weld integrity and wall uniformity.
- Non-Destructive Testing (NDT) — Eddy current inspection and/or ultrasonic testing performed along the tube length to detect internal defects, wall thinning, or surface discontinuities.
- Final Inspection & Certification — Dimensional verification, surface quality assessment, and compilation of mill test certificates (MTC) in accordance with EN 10204 3.1/3.2 requirements.
Applications
Primary Application: Oil Field Heater Systems
The coil tube is extensively deployed in fired heater (furnace) tube assemblies within oil and gas processing facilities. These include:
- Process heaters — Heating crude oil, natural gas liquids (NGLs), and refinery streams to required process temperatures.
- Reboilers — Providing latent heat input for distillation columns in gas processing plants.
- Vaporizers — Converting subcooled liquid hydrocarbons to vapor phase for downstream processing.
- Convection sections — Recovering waste heat from flue gases in multi-pass heater configurations.
Secondary Applications
- Heat exchangers — Shell-and-tube and double-pipe heat exchanger tubes in petrochemical and chemical processing.
- Boiler tubes — Water-wall tubes and superheater tubes in industrial boiler systems.
- Condensers and coolers — Refrigeration and HVAC systems requiring corrosion-resistant tubing.
- Pharmaceutical and food processing — Sanitary-grade coil tubing for hygienic fluid transfer and pasteurization systems.
- Geothermal energy systems — High-temperature geothermal fluid extraction and heat recovery loops.
CNC Pulse Cleaning Technology Integration
The application of CNC Pulse Cleaning Technology to oil field heater coil tubes represents a paradigm shift in maintenance methodology. Unlike traditional chemical cleaning or mechanical pigging, pulse cleaning utilizes precisely controlled electrochemical or ultrasonic pulse energy to remove scale, coke, and corrosion products from the internal bore without mechanical contact. This non-abrasive approach preserves the tube wall integrity, extends service intervals, and reduces the risk of wall thinning or perforation — critical concerns in high-cycle thermal environments.
Key advantages of CNC pulse cleaning for coil tube applications include:
- Removal of carbonate scale, iron oxide deposits, and hydrocarbon coke without wall loss.
- Restoration of original heat transfer coefficients, improving heater thermal efficiency by 15–30%.
- Elimination of chemical waste disposal requirements associated with acid-based cleaning.
- Reduced turnaround time compared to conventional cleaning methods.
- Compatibility with austenitic stainless steel microstructure without inducing stress corrosion cracking (SCC).
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product conformity and traceability:
- ISO 9001:2015 — Quality Management Systems certification.
- ISO 14001:2015 — Environmental Management Systems certification.
- EN 10204 Type 3.1 / 3.2 — Mill Test Certificates issued per lot, including chemical analysis, mechanical test results, and NDT reports.
- ASTM / ASME Compliance — Products manufactured and tested in accordance with ASTM A269, ASTM A213, and ASME SA-213 specifications.
- NACE MR0175 / ISO 15156 — Available for sour service applications (H₂S-containing environments) with appropriate grade selection.
- API 5CT — Compliance for oil and gas industry tubular applications where applicable.
- Third-Party Inspection (TPI) — Available upon request by SGS, Bureau Veritas, or TÜV for on-site manufacturing surveillance.
Unique Selling Points
- End-to-End Traceability — Each coil tube lot is fully traceable from raw material mill heat number through final delivery, supported by digital documentation and barcode identification.
- Custom Coil Configuration — Flexible coil diameter, tube length, and surface finish customization to match specific heater bundle designs and installation constraints.
- Cleaning-Ready Design — Tube internal surface quality (Ra ≤ 0.8 μm for P&P finish) optimized for compatibility with CNC pulse cleaning technology, ensuring maximum cleaning efficiency and minimal residual deposits.
- Thermal Cycling Resistance — Solution-annealed microstructure with low carbon content minimizes sensitization during repeated thermal cycling, preventing intergranular corrosion failure in fired heater applications.
- Extended Service Life — Superior dimensional consistency and wall uniformity reduce stress concentration points, enhancing resistance to thermal fatigue and creep at operating temperatures up to 870°C.
- Global Compliance — Products meet multiple international standards simultaneously, facilitating seamless integration into global supply chains and compliance with diverse regulatory requirements.
Technical Advisory Notes
For optimal performance in oil field heater applications, the following engineering considerations are recommended:
- Minimum bend radius during coil installation should be ≥ 5 × OD to prevent wall thinning at bend regions.
- Post-installation passivation treatment is advised after welding to restore the passive film at weld heat-affected zones (HAZ).
- For sour service (H₂S > 0.05% by volume), specify 316L grade with NACE MR0175 compliant heat treatment.
- Regular internal inspection using borescopic methods is recommended every 6–12 months, with CNC pulse cleaning scheduled when heat transfer degradation exceeds 10%.
- Storage conditions should maintain relative humidity below 60% to prevent atmospheric corrosion during pre-installation inventory.