Stainless Steel Spiral Coil Tube — Technical Specification
1. Product Overview
The Stainless Steel Spiral Coil Tube (also referred to as coil tube or coiled pipe) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is characterized by its continuous helical geometry, formed through advanced coiling technology that enables the production of long, seamless tubular sections wound into a compact spiral configuration. The spiral coil tube is widely recognized in industrial applications for its superior heat transfer efficiency, space-saving geometry, and resistance to thermal fatigue.
Based on the principles outlined in "Spiral Coil Tube Manufacturing Device Construction Technology", the production of high-quality coil tubes demands strict control over metallurgical composition, dimensional tolerances, and forming parameters. The resulting product combines the corrosion resistance inherent to stainless steel alloys with the structural advantages of a continuous coil form, making it ideal for applications in chemical processing, power generation, HVAC systems, and thermal exchangers.
2. Material & Properties
2.1 Base Material
The primary material grade employed is Stainless Steel conforming to international standards including ASTM A213/A213M (Standard Specification for Stainless Steel Tubing, Ferritic, Austenitic, and Ferritic-Austenitic (Duplex) for Heat-Transfer and Similar Applications) and EN 10217-7 (Technical Delivery Conditions for Heat-Resistant Stainless Steel Tubes for Heat Exchangers).
2.2 Common Alloy Grades
- 304 (UNS S30400) — Austenitic stainless steel with 18% Cr, 8% Ni; general-purpose corrosion resistance
- 316 (UNS S31600) — Austenitic stainless steel with 16–18% Cr, 10–14% Ni, 2–3% Mo; enhanced pitting and crevice corrosion resistance
- 321 (UNS S32100) — Stabilized austenitic grade with titanium addition; resistance to intergranular corrosion at elevated temperatures
- 316L (UNS S31603) — Low-carbon variant of 316; improved weldability and resistance to sensitization
- 904L (UNS N08904) — High-alloy austenitic grade; exceptional resistance to aggressive chemical environments
2.3 Mechanical Properties
| Property | Grade 304 | Grade 316 | Grade 321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 515 | ≥ 485 | ≥ 515 |
| Yield Strength (MPa) | ≥ 205 | ≥ 170 | ≥ 205 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 40 |
| Density (g/cm³) | 8.00 | 8.03 | 8.00 |
| Thermal Conductivity (W/m·K at 100°C) | 16.3 | 16.3 | 16.3 |
| Maximum Service Temperature (°C) | 870 | 870 | 900 |
2.4 Corrosion Resistance
The passive chromium oxide film (Cr₂O₃) formed on the surface provides exceptional resistance against atmospheric corrosion, aqueous environments, and a wide range of chemical agents. The addition of molybdenum in grades such as 316 and 904L further enhances resistance to chloride-induced pitting and stress corrosion cracking (SCC).
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6 mm – 159 mm (customizable) |
| Wall Thickness (WT) | 0.5 mm – 8.0 mm |
| Coil Diameter | 300 mm – 2,000 mm |
| Coil Length (per coil) | 10 m – 200 m |
| Helix Pitch | 3 mm – 25 mm |
| Surface Finish | No. 1 Annealed, 2B, BA (Bright Annealed), or Custom |
| End Condition | Plain end, Beveled, or Threaded |
| Dimensional Tolerance (OD) | ±0.10 mm (per ASTM A213) |
| Dimensional Tolerance (WT) | ±10% of nominal |
| Manufacturing Standard | ASTM A213, EN 10217-7, GB/T 12771 |
4. Manufacturing Process
4.1 Raw Material Preparation
High-purity stainless steel billets or strip stock are selected based on the target alloy grade. Incoming materials undergo spectroscopic analysis to verify chemical composition and ensure conformance to specified standards. Any deviation in alloying elements (Cr, Ni, Mo, Ti, C, etc.) is rejected at this stage.
4.2 Seamless Tube Forming
The tube blank is produced via either the hot-rolling and piercing method or the cold-drawn process:
- Hot Rolling & Piercing: Steel billets are heated to 1,150–1,250°C and pierced through a mandrel to produce seamless tube blanks. This method is preferred for larger diameters.
- Cold Drawing: For smaller diameters and tighter tolerances, seamless tube blanks are cold-drawn through progressively smaller dies to achieve the final dimensions with superior surface finish and mechanical properties.
4.3 Heat Treatment & Annealing
Following forming, the tube undergoes solution annealing at 1,050–1,150°C followed by controlled air or water quenching. This process dissolves carbides, restores full austenitic microstructure, and ensures optimal corrosion resistance and ductility.
4.4 Coil Winding (Coiling)
The straight tube is then fed into a precision coiling machine that winds the tube into a continuous helical or spiral coil. Key process parameters include:
- Bend radius control — maintained at a minimum of 3× the tube OD to prevent ovality and wall thinning
- Tension control — regulated to prevent kinking or residual stress accumulation
- Helix pitch uniformity — critical for consistent heat transfer performance in downstream applications
4.5 Post-Coil Treatment
After coiling, the product may undergo:
- Pickling and Passivation — removal of surface scale and restoration of the passive oxide layer using nitric acid/hydrofluoric acid solutions
- Stress Relief Annealing — low-temperature annealing (450–650°C) to relieve residual stresses introduced during coiling
- Surface Polishing — mechanical or electrochemical polishing for mirror-finish applications
4.6 Quality Inspection
Every production batch is subjected to rigorous quality control, including:
- Visual Inspection — surface defects, weld lines, and dimensional irregularities
- Dimensional Measurement — OD, WT, coil diameter, and helix pitch verification
- Hydrostatic Testing — pressure testing at 1.5× maximum working pressure for leak detection
- Non-Destructive Testing (NDT) — eddy current or ultrasonic testing for internal defects
- Chemical Analysis — spectrometric verification of alloy composition
- Mechanical Testing — tensile, hardness, and impact tests on sample coupons
5. Applications
5.1 Heat Exchangers & Thermal Systems
The spiral coil geometry provides an exceptionally high surface-area-to-volume ratio, making coil tubes ideal for compact heat exchangers, air-to-water heat exchangers, and evaporator coils. The helical configuration induces secondary flow patterns (Dean vortices) that enhance convective heat transfer coefficients by 20–40% compared to straight tubes of equivalent diameter.
5.2 Chemical & Petrochemical Processing
Stainless steel coil tubes are employed in chemical reactors, condensers, and distillation columns where resistance to aggressive media (acids, alkalis, chlorides) is paramount. Grades such as 316L and 904L provide extended service life in highly corrosive environments.
5.3 Food & Pharmaceutical Industry
Compliant with 3-A Sanitary Standards and EHEDG guidelines, BA-finish coil tubes are used in pasteurization systems, sterilization equipment, and fluid transfer lines where hygienic conditions are mandatory.
5.4 Power Generation
In boiler systems, superheaters, and economizers, stainless steel coil tubes withstand extreme thermal cycling and high-temperature oxidation. Grade 321 and 310S are preferred for high-temperature service exceeding 800°C.
5.5 HVAC & Refrigeration
Compact coil assemblies manufactured from stainless steel coil tubes are integral to air conditioning evaporators, condenser coils, and refrigeration systems, providing efficient heat exchange in space-constrained installations.
6. Quality Certifications
| Certification | Description |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health & Safety Management System |
| EN 10204 | Inspection Documents — Type 3.1 (Third-Party Test Reports) |
| NACE MR0175 / ISO 15156 | Materials for Use in H₂S-Containing Environments |
| PED 2014/68/EU | Pressure Equipment Directive Compliance |
| CE Marking | European Conformity |
7. Unique Selling Points
- Superior Heat Transfer Performance: The helical coil geometry generates Dean vortices that enhance turbulent mixing, improving heat transfer efficiency by up to 40% over conventional straight-tube designs.
- Compact Footprint: Coiled configuration maximizes heat exchange area within minimal installation space, reducing capital costs and floor space requirements.
- Thermal Fatigue Resistance: The continuous coil form accommodates thermal expansion without stress concentration, extending service life in cyclic-temperature applications.
- Customizable Geometry: Coil diameter, helix pitch, tube OD, and wall thickness are adjustable to meet specific engineering requirements.
- Full Traceability: Each coil tube batch is accompanied by a mill test certificate (MTC) with full chemical and mechanical property documentation, ensuring complete supply chain traceability.
- Corrosion Durability: The austenitic stainless steel microstructure, combined with surface passivation treatment, provides decades of reliable service in aggressive chemical and marine environments.
8. Conclusion
The Stainless Steel Spiral Coil Tube produced by Wenzhou Jixing Metal Materials Co., Ltd represents a convergence of advanced metallurgical science and precision manufacturing engineering. By adhering to international standards and implementing rigorous quality assurance protocols throughout the manufacturing chain — from raw material selection through final inspection — the product delivers exceptional performance in demanding industrial applications. The integration of spiral coil geometry with the inherent advantages of stainless steel alloys yields a product that is not only functionally superior but also economically advantageous over its service lifecycle.