Stainless Steel Coil Tube — Natural Gas Dehydration Unit Heat Exchanger Application
Product Overview
The Stainless Steel Coil Tube (Product No. 923) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled tubing solution specifically designed for use in natural gas dehydration unit heat exchangers. This product is engineered to withstand the extreme corrosive environments encountered in natural gas processing facilities, where exposure to acidic condensates, hydrogen sulfide (H₂S), carbon dioxide (CO₂), and water-based glycol solvents (e.g., monoethylene glycol — MEG, triethylene glycol — TEG) poses significant challenges to conventional metallic heat exchange surfaces.
The coil tube is supplied in continuous spiral or helical coil configurations, optimized for maximum heat transfer efficiency within compact heat exchanger bundles. The product represents a critical component in the upstream and midstream natural gas processing chain, ensuring reliable thermal management during the dehydration and purification stages of gas treatment.
Material & Properties
The coil tube is fabricated from high-performance austenitic and super-austenitic stainless steel grades, selected specifically to address the corrosion prevention requirements of natural gas dehydration environments. The following materials are available:
- AISI 304 (UNS S30408) — General-purpose austenitic stainless steel with excellent resistance to atmospheric and mild corrosive environments. Suitable for non-sulfidic natural gas dehydration service.
- AISI 316L (UNS S31603) — Low-carbon, molybdenum-bearing austenitic stainless steel offering superior resistance to pitting and crevice corrosion caused by chlorides and sulfides. Preferred for environments with elevated H₂S and CO₂ concentrations.
- AISI 321 (UNS S32100) — Titanium-stabilized austenitic stainless steel with enhanced resistance to intergranular corrosion, suitable for high-temperature dehydration applications.
- Super Duplex Stainless Steel (UNS S32750) — High-strength, high-corrosion-resistance alloy for the most aggressive sour gas environments, offering a combination of mechanical strength and resistance to sulfide stress cracking (SSC).
Key Mechanical and Physical Properties
| Property | AISI 304 | AISI 316L | AISI 321 | Super Duplex S32750 |
|---|---|---|---|---|
| Tensile Strength (MPa, min.) | 515 | 485 | 515 | 800 |
| Yield Strength (MPa, min.) | 205 | 170 | 205 | 550 |
| Elongation (% , min.) | 40 | 40 | 40 | 25 |
| Density (g/cm³) | 8.0 | 8.0 | 8.0 | 7.8 |
| Thermal Conductivity (W/m·K @ 20°C) | 16.3 | 16.3 | 16.3 | 15.0 |
| Corrosion Resistance (H₂S/CO₂) | Moderate | High | High | Very High |
| Maximum Service Temperature (°C) | 870 | 870 | 900 | 300 |
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管) |
| Product No. | 923 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Coil Configuration | Helical / Spiral / U-tube / Serpentine |
| Outer Diameter (OD) | 12 mm – 114.3 mm (½" – 4½") |
| Wall Thickness | 0.5 mm – 8.0 mm |
| Coil Diameter | 300 mm – 2000 mm (customizable) |
| Coil Length | Up to 500 m per continuous coil |
| Surface Finish | 2B, BA (Bright Annealed), No. 4 Polish, Mirror Finish |
| End Treatment | Plain, Beveled, Flanged, Threaded, or Custom Fittings |
| Operating Pressure | Up to 40 MPa (design-dependent) |
| Operating Temperature | −196 °C to +870 °C (material-dependent) |
| Standards Compliance | ASTM A269, ASTM A312, ASME B36.19M, EN 10216-5, GB/T 12771 |
Manufacturing Process
The production of high-quality stainless steel coil tubes for natural gas dehydration heat exchanger applications follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and corrosion resistance:
- Material Selection & Inspection: Raw material (hot-rolled coil or seamless tube stock) is procured from certified mills and subjected to spectroscopic analysis to verify chemical composition compliance with the specified grade.
- Hot Rolling & Annealing: Tube stock is hot-rolled to approximate dimensions and subsequently annealed to relieve residual stresses and refine grain structure.
- Cold Drawing / Cold Rolling: The tube is cold-drawn or cold-rolled to achieve precise final dimensions (OD and wall thickness), producing a uniform microstructure and enhanced mechanical properties.
- Precision Coiling: Using advanced CNC-controlled coiling machinery, the drawn tube is formed into the required helical, spiral, or serpentine configuration with tight tolerance control on coil diameter, pitch, and bend radius.
- Solution Heat Treatment: The coiled tube is solution-annealed at temperatures between 1050 °C and 1100 °C, followed by rapid water quenching, to dissolve carbides and restore full austenitic corrosion resistance.
- Pickling & Passivation: The tube surface is pickled using a mixed acid bath (nitric acid + hydrofluoric acid) to remove mill scale and oxide films, followed by passivation to establish a protective chromium oxide layer.
- Non-Destructive Testing (NDT): Every coil tube undergoes 100% eddy current testing (ECT) and hydrostatic pressure testing to detect internal defects, wall thinning, or penetration flaws.
- Final Dimensional Inspection: OD, wall thickness, coil diameter, and length are verified using calibrated instruments, with results documented for traceability.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. is specifically engineered for the following critical applications in the natural gas processing industry:
- Natural Gas Dehydration Unit Heat Exchangers: Serves as the primary heat transfer element in glycol (MEG/TEG) contactor and regenerator systems, where resistance to glycol degradation products and acidic contaminants is paramount.
- Sour Gas Processing: Deployed in facilities handling hydrogen sulfide (H₂S)-containing natural gas, providing resistance to sulfide stress cracking (SSC) and corrosion under deposit (CUD).
- Gas Condensate Recovery Systems: Utilized in heat exchangers that cool and condense light hydrocarbons from natural gas streams, withstanding hydrocarbon-induced stress corrosion cracking (HIC).
- Amine Treating Systems: Applied in acid gas removal (AGR) unit heat exchangers where exposure to alkanolamine solutions (MEA, MDEA, DEA) requires exceptional corrosion resistance.
- Offshore Platform Heat Exchangers: Suitable for offshore natural gas processing platforms where space constraints demand compact, high-efficiency coil configurations and where resistance to chloride-induced pitting is essential.
- LNG (Liquefied Natural Gas) Pre-Cooling Systems: Used in cryogenic heat exchangers for natural gas liquefaction trains, where low-temperature toughness and thermal cycling resistance are required.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and compliance designations:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification demonstrating environmental responsibility in manufacturing operations.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- ASME "U" Stamp / "S" Stamp — Authorization to manufacture pressure vessels and heat exchanger components in compliance with the ASME Boiler and Pressure Vessel Code.
- NACE MR0175 / ISO 15156 — Compliance with materials requirements for equipment in H₂S-containing environments in oil and gas production.
- API 5L / API 5CT — Compliance with American Petroleum Institute standards for line pipe and casing/tubing materials.
- EN 10204 3.1 / 3.2 — Third-party inspection and certification of material compliance available upon request.
Unique Selling Points
1. Corrosion Prevention Expertise for Natural Gas Dehydration Service: This product is specifically developed based on in-depth technical study of corrosion mechanisms in natural gas dehydration unit heat exchangers, including pitting corrosion, intergranular corrosion, stress corrosion cracking (SCC), and sulfide stress cracking (SSC). The material selection and manufacturing process are optimized to mitigate each identified corrosion failure mode.
2. Continuous Coil Configuration: The seamless continuous coil design eliminates weld joints within the heat transfer path, significantly reducing potential leak points and improving long-term reliability in high-pressure natural gas service.
3. Precision Coiling Tolerances: CNC-controlled coiling ensures consistent bend radius and pitch throughout the coil length, guaranteeing uniform heat transfer performance and preventing flow maldistribution within heat exchanger bundles.
4. Full Traceability: Each coil tube is accompanied by a complete material traceability package including mill test certificates (MTC), heat number records, NDT reports, and dimensional inspection data, enabling full supply chain traceability.
5. Custom Engineering Support: Wenzhou Jixing Metal Materials Co., Ltd. provides engineering consultation for coil configuration design, material selection, and corrosion assessment tailored to specific natural gas processing conditions, including sour gas composition, operating temperature, and pressure parameters.
Corrosion Prevention Measures — Technical Summary
Based on the technical study of corrosion prevention measures for natural gas dehydration unit heat exchanger coil tubes, the following engineering controls are recommended and implemented in this product:
- Material Upgrade: Selection of molybdenum-bearing (316L) or super-duplex stainless steel grades to enhance resistance to pitting and crevice corrosion from chlorides and sulfides.
- Stress Relief: Post-forming solution heat treatment to eliminate residual stresses introduced during cold coiling, thereby reducing susceptibility to stress corrosion cracking.
- Surface Passivation: Complete removal of free carbon and iron contamination from the surface through acid pickling and passivation, ensuring a stable chromium oxide protective film.
- Carbide Precipitation Control: Use of low-carbon grades (304L, 316L) or stabilized grades (321) to prevent intergranular sensitization during welding or high-temperature service.
- Regular Inspection Protocol: Implementation of periodic eddy current testing and thickness measurement programs to monitor coil tube condition throughout the service life of the dehydration unit.