Stainless Steel Coil Tube (盘管 Coiltube) — Technical Product Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Catalogue No.: 763
Classification: Literature-Based Product Study
Reference Literature: Performance Study of Ultra-High Gravity Rotating Bed Coil-Tube Liquid Distributor
1. Product Overview
The Stainless Steel Coil Tube (盘管 Coiltube) is a precision-engineered continuous tubular product formed by cold-bending or hot-forming a seamless or welded stainless steel tube into a helical or serpentine coil configuration. This product is manufactured by Wenzhou Jixing Metal Materials Co., Ltd., a leading supplier in the stainless steel pipe and tube industry based in Wenzhou, Zhejiang Province, China.
Coil tubes serve as critical structural and functional components in a wide range of industrial applications, including heat exchangers, chemical reactors, liquid distribution systems, and ultra-high gravity rotating bed equipment. The helical geometry provides a significantly larger surface-area-to-volume ratio compared to straight tubes of equivalent length, making coil tubes highly efficient for mass and heat transfer operations.
This product specification is informed by the academic research documented in the study "Performance Study of Ultra-High Gravity Rotating Bed Coil-Tube Liquid Distributor", which investigates the hydraulic performance, flow distribution uniformity, and mechanical integrity of coil-tube-based liquid distributors under ultra-high gravity (Centrifugal Field, CF) conditions. The findings from this research directly inform the design parameters, material selection, and performance expectations for the coil tubes supplied by Wenzhou Jixing Metal Materials Co., Ltd.
2. Material & Properties
2.1 Base Material Grades
Coil tubes are manufactured from a range of austenitic and duplex stainless steel grades, selected based on the intended service environment and mechanical requirements:
- SAE 304 (UNS S30400 / AISI 304): General-purpose austenitic stainless steel with excellent corrosion resistance, formability, and weldability. Chromium (Cr) content: 18–20%; Nickel (Ni) content: 8–10.5%.
- SAE 304L (UNS S30403): Low-carbon variant of S304 (C ≤ 0.03%) designed to minimize intergranular corrosion (IGC) during welding and heat treatment operations.
- SAE 316 (UNS S31600 / AISI 316): Molybdenum-bearing austenitic stainless steel with superior resistance to pitting corrosion and crevice corrosion. Mo content: 2.0–3.0%.
- SAE 316L (UNS S31603): Low-carbon variant of S316 (C ≤ 0.03%), preferred for welding-intensive applications and chemical processing environments.
- SAE 321 (UNS S32100): Titanium-stabilized austenitic stainless steel with excellent resistance to intergranular corrosion at elevated temperatures (450–850 °C).
- SAE 310S (UNS S31008): High-temperature austenitic stainless steel suitable for sustained service up to 1150 °C.
- SAE 2205 (UNS S31803): Duplex stainless steel (22% Cr, 5% Ni, 3% Mo) offering yield strength approximately double that of austenitic grades, with excellent resistance to chloride stress corrosion cracking (Cl-SCC).
2.2 Mechanical Properties
| Property | SAE 304 / 304L | SAE 316 / 316L | SAE 321 | SAE 310S | SAE 2205 |
|---|---|---|---|---|---|
| Yield Strength (σ0.2) — MPa | ≥ 205 | ≥ 205 | ≥ 205 | ≥ 205 | ≥ 450 |
| Tensile Strength (UTS) — MPa | 515 – 720 | 515 – 720 | 515 – 720 | 515 – 720 | 620 – 880 |
| Elongation (% at Break) | ≥ 40 | ≥ 40 | ≥ 40 | ≥ 40 | ≥ 25 |
| Hardness (HBW) | ≤ 217 | ≤ 217 | ≤ 217 | ≤ 217 | ≤ 350 |
| Maximum Service Temperature — °C | 870 | 870 | 925 | 1150 | 300 |
| Corrosion Resistance (Pitting, PREN) | 18 – 20 | 24 – 26 | 18 – 20 | 19 – 21 | 34 – 38 |
2.3 Physical Properties
- Density: 7.93 – 8.00 g/cm³ (grade-dependent)
- Thermal Conductivity (at 20 °C): 14.6 – 16.3 W/(m·K)
- Thermal Expansion Coefficient (20–100 °C): 16.0 – 18.5 × 10⁻⁶ /°C
- Specific Heat (at 20 °C): 0.50 – 0.53 J/(g·K)
- Electrical Resistivity (at 20 °C): 0.72 – 0.90 × 10⁻⁶ Ω·m
3. Specifications
3.1 Geometric Dimensions
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) — mm | Φ6.0 – Φ325.0 | ASTM A269 / A213 / GB/T 12771 |
| Wall Thickness (WT) — mm | 0.5 – 12.0 (tolerance: ±10% or ±0.1 mm, whichever is greater) | ASTM A269 / EN 10216-5 |
| Coil Diameter (CD) — mm | Φ100 – Φ2000 (customizable per engineering drawing) | Manufacturer-specific / Customer drawing |
| Coil Pitch (P) — mm | 50 – 500 (adjustable based on application) | Manufacturer-specific / Customer drawing |
| Coil Turns | 1 – 500+ (continuous coil or multi-turn helical) | Manufacturer-specific / Customer drawing |
| Tube Length (total developed length) — m | 5 – 5000 (continuous coil) | Per customer requirement |
| Bend Radius (minimum) — mm | ≥ 3 × OD (cold bending); ≥ 2 × OD (hot bending) | ASTM A213 / ASME B31.3 |
| Surface Finish | Ra ≤ 0.8 μm (electropolished); Ra ≤ 1.6 μm (mechanically polished); Ra ≤ 3.2 μm (pickled & passivated) | ASTM A269 / EN 10216-5 |
3.2 Dimensional Tolerances
| Dimension | Tolerance Class | Standard |
|---|---|---|
| Outer Diameter | ±0.10 mm (OD ≤ 50 mm); ±0.15 mm (50 < OD ≤ 150 mm); ±0.20 mm (OD > 150 mm) | ASTM A269 / EN 10216-5 |
| Wall Thickness | ±10% (standard); ±5% (precision / tight tolerance) | ASTM A269 / GB/T 12771 |
| Coil Diameter | ±1.0% of nominal | Customer drawing / ISO 13507 |
| Coil Pitch | ±2.0 mm | Customer drawing |
| Roundness (eccentricity) | ≤ 2% of wall thickness | ASTM A269 |
| Straightness (per straight section) | ≤ 1.0 mm/m | EN 10216-5 |
3.3 Applicable Standards
- ASTM A269 / A269M: Standard Specification for Welded Austenitic Chromium and Chromium-Nickel Stainless Steel Seamless and Welded Tubes and Pipes
- ASTM A213 / A213M: Standard Specification for Heat-Exchanger and Condenser Tubes, Non-Ferrous
- EN 10216-5: Seamless and Welded Stainless Steel Tubes for Technical Uses — Part 5: Non-Heat Resistant Tubes
- GB/T 12771: Stainless Steel Seamless Tubes for General Purposes (Chinese National Standard)
- GB/T 14976: Fluid Transport Stainless Steel Seamless Tubes
- ASME B31.3: Process Piping
- ISO 13507: Tubes and Pipes — Inspection Methods
- GB/T 24511: Pressure Vessel — Seamless Stainless Steel Tubes
4. Manufacturing Process
4.1 Raw Material Procurement and Inspection
The manufacturing process begins with the procurement of stainless steel seamless tubes or welded tubes from certified mills. Incoming material is subjected to rigorous inspection including:
- Spectroscopic chemical analysis (Optical Emission Spectrometry, OES) to verify alloy composition
- Hydrostatic pressure testing to ensure internal integrity
- Visual inspection for surface defects, laminations, and scaling
- Mechanical property verification via tensile testing on coupon samples
4.2 Coil Forming
The coil forming process is the defining manufacturing step for this product. It involves the following stages:
- Pre-Forming Straightening: The incoming straight tube is fed through a precision straightener to achieve a uniform cross-section and eliminate any residual curvature or ovality from the upstream forming process.
- Coil Mandrel Setup: A set of mandrels or guide wheels is configured to the desired coil diameter and pitch. The number of mandrels and their spacing determine the final helical geometry.
- Cold Bending (for OD ≤ Φ25 mm): The tube is mechanically bent around the mandrel set at ambient temperature. This process induces controlled plastic deformation while maintaining material integrity. The bending rate is carefully controlled to prevent work hardening and cross-sectional distortion.
- Hot Bending (for OD > Φ25 mm or high-strength grades): The tube is heated to 800–1100 °C (depending on grade) and then bent around the mandrel set. Hot bending reduces the forming force required and minimizes the risk of cracking or excessive work hardening.
- Stress Relief Annealing (optional): For applications requiring residual stress minimization, the formed coil may undergo solution annealing at 1050–1150 °C followed by controlled cooling. This eliminates bending-induced residual stresses and restores full ductility.
4.3 Surface Treatment
- Pickling: Immersion in a mixed acid solution (HNO₃ + H₂SO₄ or HF + HNO₃) to remove oxide scale, heat tint, and surface contaminants formed during hot forming or welding.
- Passivation: Treatment with dilute nitric acid (HNO₃, 20–30%) or citric acid to form a uniform, protective chromium oxide (Cr₂O₃) passive film on the surface, enhancing corrosion resistance.
- Electropolishing (EP): Electrochemical polishing to achieve a mirror-like surface finish (Ra ≤ 0.4 μm) with enhanced corrosion resistance and hygienic properties. Used for pharmaceutical, food, and semiconductor applications.
- Brushing / Mechanical Polishing: Mechanical surface finishing using abrasive belts or brushes for decorative or functional surface requirements.
4.4 End Treatment and Cutting
- End deburring and chamfering to remove burrs and prepare for welding or mechanical joining
- End capping or plugging for transportation and storage to prevent contamination
- Optional end welding of transition fittings (e.g., flanges, sockets, threaded connections)
4.5 Quality Control and Testing
- Dimensional Inspection: Laser-based diameter gauges, ultrasonic wall thickness gauges, and coordinate measuring machines (CMM) for coil geometry verification
- Hydrostatic / Pneumatic Pressure Testing: Testing at 1.5 × Maximum Allowable Working Pressure (MAWP) for a minimum of 30 seconds to verify internal integrity
- Non-Destructive Testing (NDT):
- Eddy Current Testing (ECT) for surface and near-surface defect detection
- Magnetic Particle Inspection (MPI) for ferromagnetic materials (applicable to martensitic and ferritic grades)
- Ultrasonic Testing (UT) for internal defect detection
- Visual Testing (VT) for surface quality assessment