Stainless Steel Spiral Coil Tube (Coiltube) — Technical Product Specification
1. Product Overview
The Stainless Steel Spiral Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is produced through a controlled hydraulic bending process that forms straight stainless steel tubes into helical (spiral) configurations while maintaining dimensional accuracy, metallurgical integrity, and surface finish quality. The Coiltube is classified under the industrial product category of "Documentary Learning Materials" (文献学习), reflecting its dual role as both a finished industrial component and a reference standard for manufacturing process documentation and quality benchmarking.
The spiral coil tube represents a specialized form of stainless steel tubing where the helical geometry is achieved through progressive hydraulic bending rather than extrusion or seamless drawing. This manufacturing approach enables the production of large-diameter coils with tight pitch tolerances and minimal wall-thickness variation, making it suitable for applications demanding both mechanical resilience and corrosion resistance.
2. Material & Properties
2.1 Base Material Grades
- ASTM A269 / A270 Series — Commonly employed grades include 304 (UNS S30400), 304L (UNS S30403), 316 (UNS S31600), 316L (UNS S31603), 321 (UNS S32100), and 310S (UNS S31008).
- Equivalent Standards — EN 1.4301 (304), EN 1.4401 (316L), JIS SUS304, JIS SUS316L.
2.2 Mechanical Properties
| Property | 304 / 304L | 316 / 316L | 321 | 310S |
|---|---|---|---|---|
| Tensile Strength (MPa) | ≥ 515 | ≥ 515 | ≥ 515 | ≥ 515 |
| Yield Strength (MPa, 0.2% offset) | ≥ 205 | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation (% min.) | ≥ 40 | ≥ 40 | ≥ 40 | ≥ 35 |
| Density (g/cm³) | 8.00 | 8.00 | 8.00 | 8.00 |
| Thermal Conductivity (W/m·K, at 100°C) | 16.3 | 14.6 | 16.3 | 15.8 |
| Maximum Service Temperature (°C) | 870 | 870 | 900 | 1150 |
2.3 Corrosion Resistance Characteristics
- Chromium Content: 18–20% minimum, providing passive oxide layer formation for atmospheric and mild chemical environments.
- Nickel Content: 8–12%, enhancing ductility and stabilizing the austenitic microstructure.
- Molybdenum Content (316/316L grades): 2–3%, conferring superior resistance to pitting and crevice corrosion in chloride-rich environments.
- Titanium Stabilization (321 grade): Ti ≥ 5×C, preventing intergranular corrosion during welding and high-temperature service.
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Product Designation | Stainless Steel Spiral Coil Tube (Coiltube) |
| Product Catalog No. | 1532 |
| Tube Outer Diameter (OD) | 6 mm – 219 mm (adjustable per hydraulic press capacity) |
| Wall Thickness | 0.5 mm – 12 mm |
| Coil Outer Diameter | 100 mm – 2,000 mm |
| Helix Pitch (mm/turn) | 5 mm – 150 mm (customizable) |
| Number of Turns | 3 – 50+ (per coil unit) |
| Tube Length (straight, pre-bending) | Up to 12,000 mm |
| Surface Finish | BA (Bright Annealed), Pickled & Polished (PP), or 2B Mill Finish |
| End Condition | Plain cut, beveled, or thread-protected |
| Tolerance — OD | ±0.05 mm (precision grades); ±0.1 mm (standard) |
| Tolerance — Wall Thickness | ±10% (standard); ±5% (tight tolerance) |
| Bending Radius (minimum) | ≥ 2.5× OD (hydraulic cold bending); ≥ 1.5× OD (with internal mandrel) |
| Applicable Standards | ASTM A269, ASTM A270, ASME SA-269, EN 10216-5, GB/T 12771 |
| Coating / Treatment | Passivation, electropolishing, or PTFE internal coating (on request) |
4. Manufacturing Process
4.1 Raw Material Preparation
Manufacturing commences with the selection of certified stainless steel round tubes or seamless pipes conforming to ASTM A269 or equivalent standards. Incoming materials undergo spectral analysis (PMI — Positive Material Identification) to verify chemical composition, followed by dimensional inspection and surface quality assessment.
4.2 Hydraulic Spiral Bending Process
The core fabrication step involves the hydraulic press-based bending of straight stainless steel tubes into helical (spiral) coil configurations. This process is governed by the following procedural sequence:
- Tooling Setup: Selection and installation of bending dies and guide mandrels calibrated to the target coil diameter, pitch, and tube geometry.
- Hydraulic Press Configuration: Setting of tonnage, stroke rate, and bending angle increments on the hydraulic press to ensure uniform curvature distribution along the tube length.
- Progressive Bending: The tube is advanced incrementally through the bending station while the hydraulic actuator applies controlled radial force, forming each successive turn of the helix.
- Pitch Control: Feed rate synchronization between the tube advancement mechanism and the bending arm rotation ensures precise helix pitch accuracy.
- Spring-Back Compensation: Real-time adjustment of bending angle to account for elastic recovery (spring-back) inherent in austenitic stainless steel, typically 3°–8° depending on grade and wall thickness.
4.3 Post-Bending Operations
- Dimensional Verification: Laser scanning or coordinate measuring machine (CMM) inspection of coil diameter, pitch uniformity, and overall geometry.
- Heat Treatment (if required): Solution annealing at 1010–1150°C followed by controlled cooling to restore full austenitic microstructure and relieve bending-induced residual stresses.
- Surface Treatment: Passivation via nitric acid or citric acid immersion to enhance corrosion resistance; optional electropolishing for hygienic-grade applications.
- End Finishing: Deburring, chamfering, and protective capping of tube ends.
4.4 Process Quality Controls
Key Learning Insight (from "Bending Spiral Coil Tubes on Hydraulic Presses" — 在液压机上弯螺旋盘管): The hydraulic bending process for spiral coil tubes requires meticulous attention to the interplay between bending force, tube geometry, and material properties. Over-bending leads to wall thinning and potential cracking at the outer diameter, while under-bending results in excessive spring-back and dimensional deviation. Optimal process parameters are determined through iterative trial bending and finite element simulation (FEA) of the deformation zone.
5. Applications
5.1 Industrial Applications
- Heat Exchangers & Radiators: Spiral coil tubes serve as efficient heat transfer elements in shell-and-coil heat exchangers, automotive radiators, and industrial process cooling systems.
- Spring & Suspension Systems: Large-diameter coil tubes function as mechanical springs, shock absorbers, and suspension components in heavy equipment.
- Heat Tracing & Pipe Insulation: Coiled stainless steel tubing is used in heat tracing systems for maintaining pipeline temperatures in cryogenic and petrochemical environments.
- Fluid & Gas Conveyance: Spiral coils provide compact, high-capacity fluid routing in confined spaces such as marine systems, aerospace fuel lines, and medical equipment.
- Chemical Processing: Resistance to aggressive chemicals makes 316L coil tubes ideal for chemical dosing systems, reactor internals, and process piping loops.
- Food & Pharmaceutical Industry: Hygienic-grade (electropolished, Ra ≤ 0.4 μm) coil tubes are used in CIP (Clean-in-Place) systems, fermentation equipment, and pharmaceutical manufacturing lines.
5.2 Sector-Specific Deployments
| Sector | Typical Application | Recommended Grade |
|---|---|---|
| Oil & Gas | Subsea pipeline risers, heat exchanger coils | 316L, 321 |
| Food & Beverage | Brewing system coils, pasteurization tubing | 304L, 316L |
| Pharmaceutical | Reactor internals, CIP spray coils | 316L (EP finish) |
| Automotive | Radiator coils, brake fluid lines | 304, 321 |
| Petrochemical | Process heat tracing, acid-resistant coils | 316L, 904L |
| Marine & Offshore | Ballast system coils, seawater piping | 316L, Duplex 2205 |
| Aerospace | Fuel system loops, hydraulic line coils | 301, 321 |
6. Quality Certifications & Compliance
6.1 Manufacturer Certifications
- ISO 9001:2015 — Quality Management System certification for manufacturing processes.
- ISO 3834-2 — Quality requirements for welding (applicable to welded coil tube assemblies).
- EN 10204 — Type 3.1 mill test certificates (MTC) provided with every shipment.
- ASME "U" Stamp — Pressure vessel components certification (where applicable).
- NORSOK M-650 — Qualification of vendors for stainless steel products (for oil & gas sector).
6.2 Product Testing & Inspection
- Hydrostatic Pressure Testing: 1.5× working pressure, per ASTM A269 / EN 10216-5.
- Chemical Analysis: Spectrometric verification of Cr, Ni, Mo, C, Ti content per grade specification.
- Dimensional Inspection: OD, wall thickness, coil diameter, and pitch measured per batch.
- Corrosion Testing: ASTM A967 passivation verification; ASTM G48 pitting resistance testing for 316L grades.
- Intergranular Corrosion Testing: ASTM A262 Practice E (for stabilized grades 321, 347).
- Non-Destructive Testing (NDT): Magnetic particle inspection (MPI) or eddy current testing for surface and near-surface defect detection.
- Hardness Testing: Rockwell B or Vickers hardness verification post-manufacturing.
6.3 Traceability & Documentation
Each production batch is assigned a unique heat number and traceability code. Complete documentation includes material test certificates (MTC), dimensional inspection reports, process parameter records (hydraulic press settings, bending temperature, feed rates), and final inspection reports. This documentation package supports full supply chain traceability in accordance with ISO 9001 and industry-specific regulatory requirements.
7. Unique Selling Points
- Precision Hydraulic Bending Expertise: Wenzhou Jixing Metal Materials Co., Ltd. possesses documented process knowledge and empirical data for hydraulic press-based spiral coil formation, enabling tight tolerance control (pitch accuracy ±0.5 mm) across a wide range of diameters.
- Custom Geometric Configuration: Coil diameter, pitch, number of turns, and tube cross-section can be customized to meet specific application requirements without tooling redesign.
- Multigrade Availability: Comprehensive range of austenitic stainless steel grades (304, 304L, 316, 316L, 321, 310S) supports diverse environmental and mechanical requirements.
- Integrated Post-Processing: In-house passivation, electropolishing, and heat treatment capabilities eliminate the need for third-party finishing, ensuring quality consistency and reduced lead times.
- Process Documentation & Knowledge Transfer: The company maintains detailed technical documentation of the hydraulic bending process (as reflected in the "Bending Spiral Coil Tubes on Hydraulic Presses" learning materials), providing customers with process transparency and quality assurance confidence.
- Compliance with International Standards: Products conform to ASTM, ASME, EN, and GB standards, facilitating global market acceptance and regulatory compliance.
8. Ordering & Customization