Stainless Steel Spiral Coil Tube (Coil Tube) — Mine Air Cooler Series
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product No.: 579
1. Product Overview
The Stainless Steel Spiral Coil Tube (hereinafter referred to as "Coil Tube") is a precision-engineered heat exchanger component designed primarily for mining ventilation air cooling systems. This product adopts a helical coil configuration that maximizes heat transfer surface area within a compact volumetric envelope, making it an optimal solution for mine spiral coil air coolers (Spiral Coil Air Coolers, SCAC). The Coil Tube is manufactured from high-grade austenitic stainless steel, providing exceptional resistance to corrosion, oxidation, and abrasive wear under the harsh environmental conditions encountered in underground mining operations, including high humidity, sulfur-containing gases, and particulate-laden airstreams.
The spiral coil geometry facilitates a continuous, uninterrupted fluid path that minimizes pressure drop while maximizing thermal efficiency. This design principle, as detailed in engineering literature on simple design methodologies for mine spiral coil air coolers, allows for predictable thermal performance with reduced computational complexity in system-level design.
2. Material & Properties
2.1 Base Material
- Primary Grade: AISI 304 / 304L (UNS S30400 / S30403) — austenitic chromium-nickel stainless steel
- Alternative Grades: AISI 316L (UNS S31603), AISI 321 (UNS S32100), and 2205 Duplex Stainless Steel (UNS S31803) available upon request
- Compliance Standards: ASTM A269 / A270, EN 10216-5, GB/T 12771
2.2 Key Mechanical & Physical Properties (AISI 304)
| Property | Specification | Unit |
|---|---|---|
| Tensile Strength (Rm) | ≥ 515 | MPa |
| Yield Strength (Rp0.2) | ≥ 205 | MPa |
| Elongation (A) | ≥ 40 | % |
| Hardness (HBW) | ≤ 200 | HBW |
| Density | 8.0 | g/cm³ |
| Thermal Conductivity (at 20°C) | 16.3 | W/(m·K) |
| Thermal Expansion Coefficient (20–100°C) | 17.3 | ×10⁻⁶ /K |
| Maximum Service Temperature | 870 | °C |
| Corrosion Resistance (Molten Sulfuric Acid) | Excellent up to 15% | — |
| Surface Finish | 2B / No. 4 / Mirror (#8) — selectable | — |
2.3 Chemical Composition (AISI 304, wt%)
| C | Si | Mn | P | S | Cr | Ni | N |
|---|---|---|---|---|---|---|---|
| ≤ 0.08 | ≤ 1.00 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | 18.0–20.0 | 8.0–10.5 | ≤ 0.10 |
3. Specifications
3.1 Geometric & Dimensional Parameters
| Parameter | Range / Option | Notes |
|---|---|---|
| Outer Diameter (OD) | Ø 6 – Ø 51 mm | Custom sizes available |
| Wall Thickness (WT) | 0.3 – 3.0 mm | Optimized for pressure & heat transfer |
| Coil Pitch (P) | 10 – 80 mm | Adjustable per thermal requirement |
| Coil Mean Diameter | Ø 50 – Ø 600 mm | Determined by heat exchanger shell ID |
| Coil Length (Unwound) | 5 – 120 m | Continuous seamless coil |
| Number of Turns | 20 – 500 | Calculated from heat duty |
| End Connections | Flanged / Threaded / Welded / Grooved | Per ASME B16.5 or custom |
| Surface Treatment | Pickled & Passivated / Electropolished | ASTM A967 compliant |
| Maximum Working Pressure | Up to 1.6 MPa (16 bar) | Dependent on OD, WT, and temperature |
| Tolerance (OD) | ± 0.05 mm (precision) / ± 0.10 mm (standard) | Per ASTM A269 |
| Tolerance (WT) | ± 10% of nominal | Per ASTM A269 |
3.2 Performance Characteristics
- Heat Transfer Coefficient: 800 – 2,500 W/(m²·K) depending on flow regime and fluid properties
- Pressure Drop (per turn): Typically 150 – 800 Pa, optimized for laminar-to-transitional flow
- Reynolds Number Range: Re = 2,000 – 50,000 (design envelope)
- Thermal Efficiency: ≥ 85% relative to equivalent straight-tube heat exchangers
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection & Inspection: Hot-rolled stainless steel strip or seamless tube stock conforming to ASTM A269/A270 specifications. Incoming material undergoes spectroscopic analysis (PMI — Positive Material Identification), dimensional verification, and visual surface inspection.
- Forming & Cold-Rolling: Flat strip is cold-formed into seamless tube using a roll-forming process, or pre-manufactured seamless tube is selected. Cold rolling ensures tight dimensional tolerances and enhanced mechanical properties through strain hardening.
- Spiral Coiling (Helical Winding): The tube is wound onto precision mandrels using CNC-controlled coiling machines. The winding parameters — pitch, diameter, and tension — are programmatically controlled to ensure uniform coil geometry. Tension-controlled winding prevents ovalization and maintains circular cross-section throughout the coil.
- Heat Treatment (if required): Solution annealing at 1,050 – 1,100°C followed by rapid quenching (water or air) to restore full austenitic structure and maximize corrosion resistance. This step is particularly critical for 304L and 316L grades.
- Pickling & Passivation: The finished coil is immersed in a nitric-hydrofluoric acid bath to remove oxide scale and form a protective chromium oxide passive film. This conforms to ASTM A967 and ASTM A380 standards.
- Non-Destructive Testing (NDT): 100% eddy current testing (ECT) for wall thickness and surface defect detection; hydrostatic pressure testing at 1.5× maximum working pressure for leak integrity verification.
- Dimensional & Final Inspection: Verification of coil pitch uniformity, mean diameter tolerance, end connection integrity, and overall geometric compliance with engineering drawings.
- Packaging & Dispatch: Coils are individually wrapped in VCI (Vapor Corrosion Inhibitor) film, secured on wooden pallets, and labeled with material certificates and traceability documentation.
4.2 Key Manufacturing Technologies
- NC (Numerical Control) Coiling: Computer-controlled winding ensures repeatability and minimizes geometric deviation across production batches.
- Continuous Annealing: For high-volume production, continuous belt furnace annealing maintains consistent microstructure.
- Hydroforming (for custom geometries): Available for applications requiring variable-diameter coil sections or integrated fittings.
5. Applications
5.1 Primary Application — Mining Ventilation Air Cooling
The Spiral Coil Tube is the core heat exchange element in mine spiral coil air coolers (SCAC), which are used to pre-cool ambient air before it enters underground mining galleries. By reducing air temperature, the system decreases the thermodynamic load on subsequent refrigeration or dehumidification equipment, improving overall mine ventilation efficiency by 20–35%.
5.2 Additional Application Domains
- Industrial Process Cooling: Oil coolers, hydraulic fluid coolers, and chemical process heat exchangers in petrochemical and pharmaceutical plants.
- Food & Beverage Industry: Milk coolers, juice pasteurization coils, and beer fermentation temperature control systems (AISI 316L recommended).
- Marine & Offshore: Seawater heat exchangers, ballast water treatment systems, and shipboard HVAC coils (AISI 316L or 2205 Duplex).
- Power Generation: Condenser tubes, feedwater heaters, and waste heat recovery systems in thermal and nuclear power plants.
- Automotive & Aerospace: Intercoolers, oil coolers, and heat management systems in high-performance vehicles and aircraft.
- Building Services (HVAC): Chilled water coils, condenser coils, and radiant cooling systems in commercial and industrial buildings.
6. Quality Certifications & Standards Compliance
6.1 Quality Management System
- ISO 9001:2015 — Quality Management System (QMS) certification for consistent manufacturing quality
- ISO 14001:2015 — Environmental Management System (EMS) certification
- ISO 45001:2018 — Occupational Health and Safety Management System (OHSMS) certification
6.2 Product & Material Certifications
- EN 10204 3.1 Certificates: Third-party material test certificates provided with every shipment
- EN 10204 3.2 Certificates: Available upon request with independent inspection body verification
- Mill Test Reports (MTR): Full chemical analysis, mechanical property data, and heat traceability for each coil batch
- ASME Stamp: Available for pressure vessel applications (U-Stamp or R-Stamp as applicable)
- PED (Pressure Equipment Directive 2014/68/EU): CE marking for European market compliance
- NACE MR0175 / ISO 15156: Compliance for sour service environments (H₂S-containing atmospheres)
- ASTM E165: Eddy current testing standard compliance
- ASTM A967: Pickling and passivation standard compliance
6.3 Inspection & Testing Protocols
| Test Method | Standard | Frequency |
|---|---|---|
| Positive Material Identification (PMI) | ASTM E1473 / E1877 | 100% per heat |
| Eddy Current Testing (ECT) | ASTM E165 | 100% continuous |
| Hydrostatic Pressure Test | ASTM A269 | 100% per coil |
| Dimensional Measurement | ASTM A269 / A270 | 100% per coil |
| Surface Finish Verification | ASTM A479 | Per batch |
| Impact Testing (Charpy V-Notch) | ASTM A370 | Per heat |
| Intergranular Corrosion Test | ASTM A262 Practice E | For L-grade materials |
| Pitting Resistance (PREN) | ASTM G48 | For 316L / Duplex grades |
7. Unique Selling Points
The Wenzhou Jixing Metal Materials Spiral Coil Tube distinguishes itself in the global mining ventilation and industrial heat exchange market through the following competitive advantages:
- Optimized Helical Geometry for Mine Air Cooling: The coil pitch and mean diameter are engineered specifically for mine spiral coil air cooler configurations, achieving superior heat transfer performance per unit volume compared to conventional straight-tube or finned-tube alternatives. The simple design methodology approach enables rapid prototyping and customization for varying mine ventilation conditions.
- Full Traceability & Quality Assurance: Every coil is produced under a fully traceable system from raw material heat number through to final dispatch, with comprehensive EN 10204 3.1/3.2 certification documentation.
- Multi-Grade Material Flexibility: Availability of AISI 304, 304L, 316L, 321, and 2205 Duplex grades allows engineers to select the optimal material for specific corrosion environments — from standard mine ventilation to aggressive sour gas or marine applications.
- Precision CNC Manufacturing: Numer