Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
Stainless Steel Coil Tube, commonly referred to as Coiltube or Coiled Stainless Steel Pipe, is a continuous-length tubular product manufactured in a helical coil configuration rather than discrete straight lengths. This product category encompasses seamless and welded stainless steel tubing formed onto large-diameter spools for storage, transport, and field deployment. The coil form factor eliminates the need for field welding at joints, significantly reducing installation labor, minimizing leak risk, and enabling rapid deployment in remote or challenging environments.
Wenzhou Jixing Metal Materials Co., Ltd. supplies high-grade stainless steel coil tubes designed for demanding industrial applications including fluid transportation, structural piping systems, hydropower infrastructure, oil and gas conveyance, and civil engineering projects. The product has been validated through large-scale pumping tests in international projects, demonstrating exceptional mechanical integrity and dimensional stability under sustained operational loads.
2. Material Composition & Properties
2.1 Commonly Available Grades
| Grade Designation | UNS Number | Cr (%) | Ni (%) | Mo (%) | Typical Application |
|---|---|---|---|---|---|
| 304 / 304L | S30400 / S30403 | 18.0–20.0 | 8.0–10.5 | — | General corrosion resistance, food processing |
| 316 / 316L | S31600 / S31603 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | Chloride environments, chemical processing |
| 321 | S32100 | 17.0–19.0 | 9.0–12.0 | — | High-temperature service, heat exchangers |
| 310S | S31008 | 19.0–22.0 | 24.0–26.0 | — | Extreme oxidation resistance, furnace applications |
| 2205 (Duplex) | S31803 | 22.0–23.0 | 4.5–6.5 | 2.5–3.5 | High strength, offshore, desalination |
2.2 Mechanical Properties (Representative Values for Grade 316L)
| Property | Unit | Minimum Value |
|---|---|---|
| Tensile Strength (Ultimate) | MPa | ≥ 485 |
| Yield Strength (0.2% Offset) | MPa | ≥ 170 |
| Elongation (at Break) | % | ≥ 40 |
| Hardness (Brinell) | HBW | ≤ 217 |
| Density | g/cm³ | 8.00 |
| Thermal Conductivity (25°C) | W/(m·K) | 16.3 |
| Thermal Expansion Coefficient | ×10⁻⁶/K | 17.3 |
2.3 Key Material Characteristics
- Corrosion Resistance: The chromium oxide passive film (Cr₂O₃) provides superior resistance to atmospheric, chemical, and intergranular corrosion. Molybdenum addition in 316L grades enhances pitting and crevice corrosion resistance in chloride-containing environments.
- Weldability: Low-carbon (L) grades maintain excellent weldability with minimal sensitization risk. Post-weld annealing is generally unnecessary for L-grade coil tubes.
- Formability: The austenitic crystal structure permits extensive cold deformation without cracking, enabling tight bending radii and complex coil configurations.
- Temperature Range: Operable from cryogenic temperatures (−196°C) to approximately 870°C (oxidation-limited), with no ductile-to-brittle transition.
3. Product Specifications
3.1 Dimensional Parameters
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 219.0 mm (¼" – 8") | ASTM A312 / ASTM A269 |
| Wall Thickness (WT) | 0.5 mm – 12.0 mm | ASTM A312 / EN 10216-5 |
| Coil Inner Diameter (CID) | 300 mm – 1,200 mm (adjustable) | Manufacturer specification |
| Coil Length | Continuous; typical 100 m – 500 m per coil | Project-specific |
| OD Tolerance | ±0.15 mm (precision) / ±0.30 mm (standard) | ASTM A312 |
| Wall Thickness Tolerance | ±10% (standard) / ±5% (precision) | ASTM A312 |
| Surface Finish | 2B, No. 4 Brushed, Polished (Ra ≤ 0.4 μm) | ASTM A480 |
3.2 Applicable Standards
- ASTM A312 / A312M: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for High-Pressure Piping and Other High-Pressure Service
- ASTM A269 / A269M: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Other Similar Uses
- EN 10216-5: Tubes and pipes for mechanical and thermal uses — Non-ferrous metallic tubes and pipes — Part 5: Seamless austenitic stainless steel tubes
- ISO 13922: Tubes and pipes for mechanical and thermal uses — Non-ferrous metallic tubes and pipes
- ASME B31.3: Process Piping
4. Manufacturing Process
4.1 Production Flow
- Raw Material Preparation: Vacuum Arc Remelting (VAR) or Argon Oxygen Decarburization (AOD) metallurgy produces ingots or slabs with tightly controlled chemistry. Low-carbon L-grades are produced by ultra-low carbon (C ≤ 0.03%) casting to prevent chromium carbide precipitation at grain boundaries.
- Hot Rolling: Billets are reheated to 1,150–1,250°C and hot-rolled into hollow rounds or flat strips depending on the downstream forming route.
- Piercing / Extrusion (Seamless Route): The hot-rolled round is pierced via Mannesmann piercing mills or extruded through a die to produce a seamless hollow tube with uniform wall thickness.
- Cold Drawing / Cold Pilgering: The hot-finished tube is cold-worked through dies to achieve precise dimensional tolerances, improved mechanical properties (work hardening increases yield strength by 40–60%), and enhanced surface finish.
- Heat Treatment (Solution Annealing): Tubes are solution-annealed at 1,010–1,150°C followed by rapid water quenching to dissolve carbides, restore full ductility, and establish the passive corrosion-resistant microstructure.
- Pickle and Passivate: Hydrofluoric-nitric acid pickling removes scale; subsequent passivation establishes a chromium-rich oxide layer (10–50 nm) for immediate corrosion protection.
- Coil Winding: The finished tube is wound onto a large-diameter coil spool using a precision winding head that controls tension, maintains concentricity, and prevents kinking or ovality.
- Quality Inspection & Packaging: Each coil undergoes non-destructive testing (NDT) and is packaged with moisture-absorbing desiccants, protective end caps, and shrink-wrap for shipment.
4.2 Welded Coil Tube Alternative
For larger diameters or thicker walls, a welded route is employed: cold-rolled stainless steel strip is precision-wound and helically welded using Automatic Orbital TIG (Tungsten Inert Gas) welding or resistance welding. The weld seam undergoes in-line eddy current testing (ECT) and radiographic inspection (RT) for volumetric defect detection.
5. Quality Certifications & Testing
5.1 Certification Standards
| Certification | Scope | Validity |
|---|---|---|
| ISO 9001:2015 | Quality Management System | Annual surveillance |
| ISO 14001:2015 | Environmental Management System | Annual surveillance |
| ISO 45001:2018 | Occupational Health & Safety | Annual surveillance |
| EN 10204 3.1 / 3.2 | Material Test Reports / Inspection Certificates | Per-shipment |
| Mill Test Certificate (MTC) | Chemical composition & mechanical properties | Per-heat / per-coil |
5.2 Non-Destructive Testing (NDT) Protocol
- Eddy Current Testing (ECT): 100% in-line inspection of weld seams and tube body for surface and near-surface discontinuities (cracks, pores, inclusions). Sensitivity: ≥ 0.2 mm defect depth.
- Magnetic Particle Inspection (MPI): Applied to ferritic and duplex grades for surface crack detection.
- Ultrasonic Testing (UT): Wall thickness verification and volumetric defect detection. Minimum detectable flaw: 0.5 mm equivalent flat bottom reflector.
- Hydrostatic Pressure Test: Each coil section is pressure-tested at 1.5× design pressure to verify leak tightness and structural integrity.
5.3 Destructive Testing (Per-Batch)
- Tensile testing per ASTM A370
- Flattening test per ASTM A312
- Impact testing (Charpy V-Notch) for cryogenic applications
- Corrosion testing: Pitting (ASTM G48), Intergranular corrosion (ASTM A240), Stress corrosion cracking (ASTM G109)
- Chemical analysis via Optical Emission Spectroscopy (OES) and Inductively Coupled Plasma (ICP)
6. Applications
6.1 Industrial Piping Systems
Stainless steel coil tubes are extensively used in process piping for chemical plants, pharmaceutical manufacturing, food and beverage processing, and semiconductor fabrication. The continuous coil format enables rapid installation of long pipeline runs with minimal field joints, reducing the probability of contamination ingress and system leaks.
6.2 Oil & Gas Industry
Coiled tubing technology (CT) is widely deployed for well intervention operations including acidizing, fracturing, scale removal, and continuous flow production. Stainless steel coil tubes with 2205 duplex grades offer the combination of high yield strength (≥ 450 MPa) and superior chloride stress corrosion cracking (SCC) resistance required for subsea and offshore applications.
6.3 Civil Engineering & Infrastructure
In large-scale civil engineering projects — including the Algeria pump delivery project referenced in industry literature — stainless steel coil tubing has been validated for long-distance slurry and concrete pumping applications. The flexibility of coil configuration allows routing through complex geometries without the need for intermediate supports or welded transitions, while the material's fatigue resistance ensures long service life under cyclic pressure loading.
6.4 Heat Exchangers & Boilers
Coil tubes serve as heat transfer elements in shell-and-tube heat exchangers, air coolers, and boiler fire tubes. The coil geometry maximizes heat transfer surface area within a compact envelope, and stainless steel grades resist scaling and fouling in high-temperature service.
6.5 Aerospace & Defense
Precision-drawn stainless steel coil tubes find application in hydraulic systems, fuel lines, and instrumentation tubing where weight efficiency, corrosion resistance, and dimensional accuracy are critical.
7. Unique Selling Points
Wenzhou Jixing Metal Materials Co., Ltd. differentiates its stainless steel coil tube offering through the following value propositions:
- Proven Large-Scale Deployment: Products validated through international mega-project testing, including the longest coiled pipe pumping test in Algeria, demonstrating reliability under extreme operational conditions.
- Full Traceability: Each coil is traceable from raw material heat number through every manufacturing stage, with complete Mill Test Certificates (MTCs) conforming to EN 10204 3.1/3.2.
- Custom Coil Configuration: Coil inner diameter, length, and winding density are adjustable to meet specific deployment requirements, reducing on-site handling complexity.
- Multi-Grade Availability: Comprehensive grade portfolio from standard austenitic (304L, 316L) to high-performance duplex (2205, 2507) and super-austenitic (904L) alloys.
- Integrated Quality Assurance: In-line NDT with 100% coverage, supplemented by destructive testing per batch, ensuring zero-defect delivery