Stainless Steel Coil Tube — Floating Roof Tank Heating Coil (Ref. No. 1484)
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Category: Technical Literature & Application Reference
Product Designation: Coiltube — Heating Coil for Floating Roof Tanks with Ring Angle Steel Fixture
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) product, catalog reference No. 1484, is a precision-engineered heating coil system designed specifically for floating roof tank applications in the petroleum, chemical, and energy storage industries. This product line draws upon validated engineering practice documented in the technical study titled "Self-Made Floating Roof Tank Heating Coil Tubes and Ring Angle Steel Fixtures", which provides comprehensive guidance on the fabrication, installation, and operational optimization of heating coil assemblies integrated into large-diameter floating roof storage tanks.
The coil tube assembly functions as a thermal transfer medium within floating roof tank interiors, maintaining product temperature within specified operating ranges to prevent viscosity increase, crystallization, or phase separation of stored hydrocarbons and petrochemical products. The system employs a serpentine coil geometry wrapped around ring angle steel fixtures that provide structural support and uniform spacing, ensuring consistent thermal distribution across the tank cross-section while accommodating the vertical movement of the floating roof.
2. Material & Properties
2.1 Base Material
The coil tubes are manufactured from austenitic stainless steel, selected for its exceptional corrosion resistance, thermal stability, and mechanical durability in aggressive hydrocarbon environments. The primary grades utilized include:
- AISI 304 (UNS S30408): Standard austenitic stainless steel with 18% Chromium and 8% Nickel, suitable for general hydrocarbon heating applications.
- AISI 316L (UNS S31603): Low-carbon, molybdenum-bearing austenitic stainless steel offering superior resistance to pitting and crevice corrosion in chloride-containing environments.
- AISI 321 (UNS S32100): Titanium-stabilized austenitic stainless steel providing enhanced resistance to intergranular corrosion at elevated temperatures.
2.2 Mechanical Properties (Typical — AISI 304 Annealed)
| Property | Specification | Standard Reference |
|---|---|---|
| Tensile Strength (Rm) | ≥ 515 MPa | ASTM A269 / ASME SA-269 |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ASTM A269 / ASME SA-269 |
| Elongation (A50mm) | ≥ 40% | ASTM A269 / ASME SA-269 |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) | ASME BPV Code |
| Thermal Expansion Coefficient | 17.3 × 10⁻⁶ /°C | ASME BPV Code |
| Density | 7.93 g/cm³ | ASTM A269 |
| Maximum Operating Temperature | 870°C (non-oxidizing) | ASME BPV Code |
2.3 Corrosion Resistance
The selected stainless steel grades demonstrate excellent resistance to:
- Atmospheric corrosion in marine and industrial environments
- Hydrocarbon and petroleum product immersion
- Acidic condensate attack from sulfur-containing feedstocks
- Intergranular corrosion following welding operations (304L and 316L grades)
- Stress corrosion cracking in chloride environments (316L grade)
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Tube Outer Diameter (OD) | φ19 mm, φ22 mm, φ25 mm, φ32 mm, φ38 mm, φ50 mm (customizable) |
| Tube Wall Thickness | 1.0 mm – 3.0 mm (typical: 1.5 mm – 2.0 mm) |
| Tube Length (per coil) | Up to 12,000 mm (spooled configuration) |
| Bending Radius (Minimum) | ≥ 5D (where D = tube outer diameter) |
| Surface Finish | 2B (Cold Rolled and Annealed) or No. 4 Brushed |
| Surface Roughness (Ra) | ≤ 0.8 μm (internal), ≤ 1.6 μm (external) |
| Coil Pitch / Spacing | 50 mm – 150 mm (adjustable per thermal design) |
| Ring Angle Steel Fixture | ∠50×5 mm to ∠100×10 mm (hot-dip galvanized or stainless steel) |
| Fixture Ring Diameter | Customized to tank internal diameter (typically 10 m – 50 m) |
| Heating Medium | Hot water (80°C – 120°C) or low-pressure steam (0.2 MPa – 0.6 MPa) |
| Operating Pressure (Tube) | ≤ 1.0 MPa (typical design: 0.6 MPa) |
| Design Pressure (Fixture) | Structural load rating per GB 50017 |
| Applicable Tank Capacity | 1,000 m³ – 100,000 m³ |
| Standard Compliance | ASTM A269, ASME SA-269, GB/T 14976, EN 10216-5 |
4. Manufacturing Process
4.1 Tube Fabrication
- Raw Material Procurement: Cold-rolled stainless steel strip or seamless pipe stock conforming to ASTM A269 / ASME SA-269 chemical and mechanical specifications. Incoming material is verified through mill test certificates (MTC) and spectrographic analysis.
- Cutting: Precision shearing or plasma cutting of tube stock to required lengths, with dimensional tolerance of ±0.5 mm.
- End Preparation: Deburring, chamfering, and internal/external surface cleaning to achieve specified roughness values.
- Cold Bending: Spiral winding of tubes onto mandrels of controlled radius, ensuring uniform bend geometry without wall thinning exceeding 10% of original thickness. Bending is performed at ambient temperature using hydraulic mandrel bending equipment.
- Coil Assembly: Sequential layering of bent tube segments into serpentine coil configurations, with controlled pitch spacing maintained through fixture guides.
4.2 Ring Angle Steel Fixture Fabrication
- Pattern Development: Engineering drawings define the ring circumference based on tank internal diameter, accounting for thermal expansion and floating roof clearance requirements.
- Angle Steel Cutting & Notching: Precision cutting of angle steel segments with miter joints for seamless ring assembly.
- Welding: Continuous fillet welds joining angle steel segments into complete rings, followed by weld inspection (visual + magnetic particle testing per ASME Section V).
- Surface Treatment: Hot-dip galvanizing (minimum 85 μm coating thickness per ISO 1461) or stainless steel fabrication for corrosion protection.
- Coil Support Bracket Integration: Welding of tube support brackets at calculated intervals (typically every 1.5 m – 3.0 m) to distribute coil weight and maintain pitch uniformity.
4.3 Assembly & Installation
- Field Assembly: Pre-fabricated coil sections and ring fixtures are assembled on-site within the tank shell.
- Vertical Mounting: Ring fixtures are bolted or welded to the tank shell at designated elevation levels, with expansion joints accommodating differential thermal movement between the fixed tank shell and the moving floating roof.
- Hydraulic Connection: Inlet and outlet manifolds connect the coil circuit to the external heating medium supply system via flexible bellows or expansion loops.
- Pressure Testing: Hydrostatic pressure test at 1.5× design pressure, held for a minimum of 30 minutes with zero leakage tolerance.
- Final Inspection: Dimensional verification, weld quality assessment, and functional testing prior to commissioning.
5. Applications
5.1 Primary Applications
- Petroleum Storage Tanks: Heating of heavy crude oils, bitumen, and viscous petroleum products in floating roof storage tanks to maintain pumpability and flow characteristics.
- Petrochemical Storage: Temperature maintenance of wax-containing products (paraffin, micro-crystalline wax) and high-viscosity chemical intermediates.
- Refinery Intermediate Storage: Pre-heating of feedstocks prior to distillation or cracking processes.
- Waste Oil Recovery: Thermal management of waste oil and sludge storage tanks to facilitate phase separation and recovery operations.
- Food-Grade Storage: Temperature-controlled storage of edible oils and fats in sanitary-grade floating roof tanks.
5.2 Environmental Conditions
- Operating ambient temperature: −30°C to +60°C
- Seismic zone compatibility: Designed per GB 50011 (up to intensity 8)
- Corrosion category: C4 (moderate) to CX (extreme) per ISO 9223
- Explosion-proof classification: Suitable for Zone 1 and Zone 2 hazardous areas
6. Quality Certifications & Standards Compliance
6.1 Product Standards
| Standard | Description | Applicability |
|---|---|---|
| ASTM A269 / ASME SA-269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tube | Tube material specification |
| GB/T 14976 | Seamless Stainless Steel Tubes for Fluid Transport (Chinese National Standard) | Domestic market compliance |
| EN 10216-5 | Non-alloy and Alloy Steel Tubes — Technical Delivery Conditions — Part 5: Seamless Tubes of Austenitic Steels | European market compliance |
| ASME BPV Section I & VIII | Boiler and Pressure Vessel Code | Pressure-containing components |
| API 650 | Welded Tanks for Oil Storage | Tank integration requirements |
6.2 Quality Assurance Certifications
- ISO 9001:2015 — Quality Management System certification for manufacturing processes
- ISO 14001:2015 — Environmental Management System certification
- ASME "U" Stamp — Authorization for pressure-containing component fabrication
- Mill Test Certificates (MTC) — EN 10204 Type 3.1 for each production batch
- Third-Party Inspection (TPI) — Available upon request (SGS, Bureau Veritas, DNV)
- NACE MR0175 / ISO 15156 — Compliance for sour service applications (H₂S-containing environments)
6.3 Testing & Inspection Protocol
- Chemical composition analysis (spectrographic) — per ASTM A269
- Mechanical property verification (tensile test, hardness test) — per ASTM A269
- Hydrostatic pressure test at 1.5× design pressure
- Dimensional inspection (OD, wall thickness, length tolerance)
- Weld quality inspection: Visual examination + Magnetic Particle Testing (MT) or Dye Penetrant Testing (PT) — per ASME Section V, Article 4 & 7
- Surface finish verification (roughness profile measurement)
- Coil geometry verification (pitch uniformity, bend radius consistency)
- Final pressure test and leak tightness verification
7. Unique Selling Points
Engineering-Validated Design: This product line is informed by documented engineering practice and field-tested fabrication methodologies for floating roof tank heating systems, ensuring proven reliability in demanding industrial applications.
- Integrated Coil-and-Fixture System: The combination of precision-wound stainless steel coil tubes with robust ring angle steel fixtures provides a complete, modular heating solution that simplifies field installation and reduces total project lead time.
- Thermal Uniformity: The serpentine coil geometry with controlled