Stainless Steel Coil Tube for Polar Condensate Oil Ship Heating Systems
Product No.: 620 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular component specifically designed for the heating systems of polar condensate oil carriers. These vessels operate in extreme cryogenic environments where temperatures may descend below −40 °C, demanding exceptional material integrity, weldability, and long-term corrosion resistance. The coil tube product line developed by Wenzhou Jixing Metal Materials Co., Ltd. is engineered to withstand the rigorous thermal cycling, mechanical stress, and chemical exposure inherent in polar maritime operations.
These coil tubes serve as critical heat-exchange elements within the condensate oil heating circuit, ensuring that the cargo maintains its fluidity during transit through arctic and antarctic waters. The design philosophy integrates lessons learned from advanced full-position automatic TIG (Tungsten Inert Gas) welding technology research, enabling the production of seamless, high-integrity coil assemblies capable of withstanding omnidirectional loading conditions.
Material & Properties
The coil tubes are fabricated from austenitic stainless steel grades selected for their superior cryogenic toughness, resistance to chloride-induced stress corrosion cracking, and weldability under automated TIG processes.
- Primary Grades: AISI 304 (UNS S30408), AISI 316L (UNS S31603), and AISI 321 (UNS S32108)
- Low-Temperature Performance: Maintains ≥ 200 J impact energy at −40 °C per ASTM A370
- Corrosion Resistance: Chromium content ≥ 18%, Molybdenum content ≥ 2% (for 316L grade) providing resistance to seawater and condensate oil media
- Weldability: Low carbon interstitial content (≤ 0.03% C for "L" grades) minimizes sensitization and grain-boundary precipitation during welding
- Thermal Conductivity: 14–16 W/(m·K) at 20 °C, ensuring efficient heat transfer in heating applications
- Mechanical Properties: Tensile strength ≥ 515 MPa, Yield strength ≥ 205 MPa (annealed condition)
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 14.0 mm – 159.0 mm | ASTM A269 / EN 10216-5 |
| Wall Thickness | 0.8 mm – 6.0 mm | ISO 1127 |
| Bending Radius | ≥ 3D (3 × Outer Diameter) | Manufacturer standard |
| Coil Diameter | 600 mm – 2,000 mm | Customizable |
| Surface Finish | 2B, BA (Bright Annealed), or Mirror (Ra ≤ 0.2 μm) | ASTM A480 |
| Tolerance (OD) | ± 0.05 mm | ISO 4623 |
| Tolerance (Wall Thickness) | ± 10% of nominal | ASTM A269 |
| Welding Process | Full-position automatic TIG welding | ISO 15614-1 |
| Protective Gas | Pure Argon (99.99%) or Argon-Helium mixture | ASME Section IX |
| Operating Temperature Range | −40 °C to +400 °C | ASME BPV Code Section VIII |
| Design Pressure | Up to 16.0 MPa (customizable) | ASME BPV Code |
| Length (per coil) | 50 m – 500 m (continuous) | Manufacturer standard |
| End Treatment | Beveled, plain, or threaded (BSPP/BSPT/NPT) | ISO 7-1 / ISO 7-2 |
Manufacturing Process
The production of these coil tubes follows a rigorously controlled multi-stage manufacturing sequence that integrates advanced forming, welding, and inspection technologies:
- Material Selection & Incoming Inspection: Stainless steel coils are sourced from certified mill suppliers and subjected to spectroscopic analysis (PMI), visual inspection, and dimensional verification prior to processing.
- Coil Slitting & Straightening: The parent coil is slit to the required width and passed through a multi-stand straightening line to achieve flatness tolerances of ≤ 0.15% of width.
- Roll Forming & Coiling: Precision roll-forming equipment shapes the flat strip into the specified circular cross-section, followed by controlled coiling onto mandrels to maintain dimensional accuracy and prevent residual stress accumulation.
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Full-Position Automatic TIG Welding: The longitudinal seam is welded using a fully automated TIG welding system capable of all-position (6G) operation. Key process parameters include:
- Welding current: 60–180 A (pulse mode)
- Travel speed: 30–150 mm/min
- Shielding gas flow rate: 15–25 L/min
- Back-purge: Active nitrogen or argon to prevent internal oxidation
- Post-Weld Heat Treatment: Solution annealing at 1010–1150 °C followed by rapid water quenching to restore full austenitic microstructure and relieve residual stresses.
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Non-Destructive Testing (NDT): Each coil tube undergoes 100% volumetric and surface inspection:
- Eddy Current Testing (ECT) per ASTM E309
- Penetrant Testing (PT) per ASTM E165
- Hydrostatic pressure testing at 1.5× design pressure
- Final Dimensional Verification & Packaging: Coils are measured, certified, and packaged with desiccant protection and corrosion inhibitors for maritime transport.
Applications
- Polar Condensate Oil Carriers: Primary heating coils for maintaining cargo fluidity in arctic and sub-arctic transit routes
- Cryogenic Storage Systems: Heat-exchange elements in LNG (Liquefied Natural Gas) and LPG (Liquefied Petroleum Gas) processing facilities
- Marine Heating Systems: Boiler feedwater heaters, steam generators, and condensate return systems on offshore platforms
- Chemical Processing: Heat exchangers and process piping in acid, alkali, and organic solvent handling environments
- Food & Pharmaceutical: Sanitary-grade heat-exchange coils requiring high surface finish and full weld integrity
- Offshore & Subsea: High-pressure heating manifolds and thermal management systems for subsea production facilities
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System
- ISO 3834-2 — Quality requirements for fusion welding of metallic materials
- ASME Section IX — Welding and Brazing Qualifications (Welder & WPS certified)
- EN 10204 Type 3.1 — Inspection certificates (third-party verified)
- DNV-GL — Classification society approval for marine applications
- ABS / Lloyd's Register — Marine engineering material certification
- CE Marking — Conformity with European Pressure Equipment Directive (PED 2014/68/EU)
- NACE MR0175 / ISO 15156 — Resistance to sulfide stress cracking in H₂S environments
Unique Selling Points
- Polar-Grade Cryogenic Integrity: Materials and welding processes specifically validated for sustained operation at temperatures as low as −40 °C, with verified Charpy V-notch impact performance exceeding 200 J.
- Full-Position Automatic TIG Welding: Proprietary automated welding technology ensures consistent, repeatable weld quality across all spatial orientations, eliminating the variability associated with manual welding and enabling defect rates below 0.5%.
- 100% Volumetric Inspection: Every coil tube undergoes complete eddy current and hydrostatic testing, providing full-length weld integrity verification — a critical requirement for safety-critical marine applications.
- Full Traceability: Each coil tube is accompanied by a complete material passport including mill certificates, weld procedure specifications (WPS), welder qualification records (WQR), and NDT reports, enabling end-to-end quality traceability.
- Custom Engineering Support: The manufacturer offers bespoke design, sizing, and coiling configurations tailored to specific vessel heating system layouts, reducing installation complexity and on-site fabrication requirements.
- Enhanced Corrosion Resistance: 316L-grade options with controlled interstitial content provide superior resistance to chloride stress corrosion cracking, extending service life in seawater-exposed environments beyond conventional 304-grade alternatives.
"The integration of full-position automatic TIG welding technology with cryogenic-grade stainless steel coil tube manufacturing represents a significant advancement in the reliability and safety of heating systems for polar maritime operations. The resulting products deliver the mechanical integrity, corrosion resistance, and weld quality necessary for the most demanding cryogenic service environments."