Stainless Steel Coil Tube for Large Coiled Tank Storage Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube), product reference No. 1272, is a precision-engineered continuous tube wound into a compact coil configuration, designed primarily for integration into large-scale coiled tank storage systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product represents a specialized form of austenitic stainless steel tubing optimized for thermal storage, heat exchange, and fluid containment applications where spatial efficiency, corrosion resistance, and structural integrity are paramount.
Unlike conventional straight-length tubing, coil tubes offer the distinct advantage of being delivered in continuous, pre-wound form, eliminating the need for field welding of multiple segments. This continuous geometry is particularly advantageous in large coiled tank storage configurations, where thousands of meters of tubing are arranged in helical or spiral patterns within a containment vessel to maximize heat transfer surface area within a confined footprint.
Material & Properties
Coil tubes for large tank storage applications are typically fabricated from austenitic stainless steel grades conforming to international standards. The following materials are commonly specified:
- ASTM A213 / EN 10216-5 Grade TP304 (UNS S30400): The baseline austenitic grade offering excellent general corrosion resistance, weldability, and formability. Suitable for non-aggressive aqueous and organic media.
- ASTM A213 / EN 10216-5 Grade TP316L (UNS S31603): Enhanced molybdenum-bearing grade (2.0–2.5% Mo) providing superior resistance to pitting and crevice corrosion in chloride-containing environments. Preferred for marine, chemical, and pharmaceutical applications.
- ASTM A213 Grade TP316Ti (UNS S31635): Titanium-stabilized variant offering improved resistance to intergranular corrosion during welding and high-temperature service (up to 870 °C).
- ASTM A213 / EN 10216-5 Grade TP321 (UNS S32100): Columbium-stabilized grade suitable for elevated-temperature applications up to 900 °C with resistance to intergranular attack.
Key Mechanical and Physical Properties (Typical for 304/316L):
- Tensile Strength: ≥ 515 MPa (304), ≥ 485 MPa (316L)
- Yield Strength (0.2% offset): ≥ 205 MPa (304), ≥ 170 MPa (316L)
- Elongation: ≥ 40% (minimum, per ASTM A213)
- Thermal Conductivity: 14.6 W/(m·K) at 100 °C (304)
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100 °C)
- Maximum Service Temperature: 870 °C (304), 870 °C (316L)
Specifications
| Parameter | Specification | Applicable Standard |
|---|---|---|
| Outer Diameter (OD) | 6.35 mm – 50.80 mm (¼" – 2") | ASTM A213, EN 10216-5 |
| Wall Thickness | 0.50 mm – 3.00 mm (Schedule 10S – 40S) | ASME B36.19M |
| Coil Diameter | 600 mm – 2,400 mm (inner coil diameter) | Manufacturer specification |
| Coil Length | 50 m – 500 m per coil (continuous, seamless) | — |
| Surface Finish | 2B (cold-rolled), No. 4 brushed, or No. 8 mirror | ASTM A480 |
| Tolerance on OD | ±0.05 mm to ±0.15 mm (depending on diameter) | EN 10216-5 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A213 |
| End Condition | Cut square, beveled, or capped with plastic plugs | Customer requirement |
| Material Certification | EN 10204 3.1 / 3.2 Mill Test Certificate | EN 10204 |
Manufacturing Process
The production of stainless steel coil tubes for large coiled tank storage applications follows a rigorous multi-stage process ensuring dimensional accuracy, metallurgical integrity, and surface quality:
- Slab Casting & Hot Rolling: Primary stainless steel ingots are vacuum-arc or EAF (Electric Arc Furnace) cast, then hot-rolled into seamless tube blanks ( billets ) conforming to ASTM A269 or EN 10216-5 composition requirements.
- Piercing & Hot Extrusion: The solid billets are heated to 1,100–1,200 °C and pierced or hot-extruded through a die to form seamless hollow tubes. This ensures a homogenous microstructure without weld seams.
- Pilot Mill & Cold Drawing: Tubes are reduced to near-final dimensions through a series of cold-drawing passes using tungsten carbide or tool steel dies. This cold working imparts strain-hardening, improving tensile strength while achieving tight dimensional tolerances.
- Coil Winding: The continuous drawn tube is wound onto precision-machined mandrels to form the final coil geometry. Winding tension is carefully controlled to prevent ovalization, kinking, or inter-coil contact damage.
- Solution Annealing (Pickling & Passivation): Coils are heat-treated at 1,050–1,150 °C followed by rapid quenching to restore full austenitic structure, eliminate residual stresses from cold working, and achieve maximum corrosion resistance. Subsequent acid pickling (HNO₃/HF blend) and passivation treatment establish a stable chromium oxide passive film.
- Surface Finishing: Mechanical polishing (abrasive belt or buffing) is applied to achieve the specified surface finish grade (2B, No. 4, or No. 8 mirror) as required by the application.
- Quality Inspection & Packaging: Each coil undergoes 100% visual inspection, dimensional verification (OD, wall thickness by ultrasonic or eddy-current gauging), hydrostatic testing per ASTM A213, and chemical composition verification via optical emission spectroscopy (OES). Coils are wrapped in protective film, sleeved in cardboard or wood, and strapped for transport.
Applications
Stainless steel coil tubes in large coiled tank storage configurations serve a diverse range of industrial applications:
- Thermal Energy Storage Systems: Helically wound coil tubes within insulated tanks store thermal energy (hot or cold) for district heating, solar thermal systems, and industrial process heat recovery. The large surface-area-to-volume ratio of coiled configurations enables rapid heat exchange.
- Heat Exchangers (Coil-in-Shell): Immersed coil heat exchangers utilize continuous tube coils as the primary heat transfer surface within a shell-and-coil configuration. Common in chemical processing, food and beverage pasteurization, and pharmaceutical sterilization.
- Process Piping & Fluid Distribution: In plants requiring extensive piping networks within confined spaces, coil tubes reduce the number of fittings and welds, minimizing leak points and installation time.
- Refrigeration & HVAC: Coil tubes are used in evaporators, condensers, and chiller systems where continuous, leak-free tube runs are critical for refrigerant containment.
- Food & Beverage Industry: Sanitary-grade coil tubes (electropolished, No. 8 finish) are employed in milk pasteurization, beer brewing, and pharmaceutical fluid handling where CIP (Clean-in-Place) and SIP (Sterilize-in-Place) capabilities are essential.
- Oil & Gas / Petrochemical: 316L and duplex-grade coil tubes in storage tanks and heat exchangers resist sour gas (H₂S) and chloride-induced stress corrosion cracking.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System certification for manufacturing processes
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management
- EN 10204 Type 3.1 / 3.2 — Material Inspection Certificates with full chemical analysis and mechanical test data
- ASTM A213 / ASME SA-213 — Compliance with seamless austenitic stainless steel tube specifications
- EN 10216-5 — European standard for seamless austenitic stainless steel tubes for heat exchangers
- PED 2014/68/EU — Pressure Equipment Directive compliance for pressure-containing applications
- NSF/ANSI 61 — Drinking water system components certification (where applicable)
- 3-A Sanitary Standards — Dairy and food processing equipment compliance
- CE Marking — Conformity with European health, safety, and environmental protection requirements
Unique Selling Points
- Seamless Continuous Construction: The absence of longitudinal or circumferential welds eliminates the primary failure mode in tubular systems, ensuring superior fatigue resistance and leak-tight performance over extended service life.
- Precision Coil Geometry: Advanced CNC-controlled winding ensures uniform coil pitch, minimal inter-coil interference, and consistent spring-back characteristics, facilitating predictable installation in large tank storage systems.
- Full Traceability: Each coil is traceable to its mill heat number, with complete documentation of chemical composition, mechanical properties, and non-destructive testing results, ensuring compliance with stringent regulatory and customer qualification requirements.
- Multi-Grade Availability: Supply capability across 304, 316L, 316Ti, 321, and specialty grades enables single-source procurement for diverse corrosion and temperature requirements within a single project.
- Custom Coil Configuration: Coil diameter, length, OD, wall thickness, and surface finish are configurable to match specific thermal storage tank or heat exchanger design parameters, reducing fabrication waste and installation complexity.