316L Stainless Steel Heat Exchanger Coiled Tube (Coiltube)
Product Overview
The 316L Stainless Steel Coiled Tube (Coiltube) is a precision-engineered austenitic stainless steel tubing product supplied in continuous coil form, specifically designed for heat exchanger applications. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coiled tube represents the industry standard for low-carbon, high-corrosion-resistance tubular products used in thermal exchange systems. The "L" designation denotes ultra-low carbon content (≤0.03%), which significantly reduces the risk of intergranular corrosion during welding and high-temperature service.
Coiled tubes are supplied as continuous lengths wound into coils, enabling high-speed automatic cutting and fabrication in downstream manufacturing. This format is particularly advantageous for heat exchanger production lines where thousands of tubes must be cut to precise lengths with minimal waste and maximum throughput.
Material & Properties
Chemical Composition (ASTM A213 / ASME SA-213 TP316L)
| Element | Specification | Typical Value |
|---|---|---|
| Carbon (C) | ≤ 0.030% | 0.015–0.025% |
| Manganese (Mn) | ≤ 2.00% | 1.2–1.8% |
| Phosphorus (P) | ≤ 0.045% | 0.020–0.040% |
| Sulfur (S) | ≤ 0.030% | 0.005–0.015% |
| Silicon (Si) | ≤ 1.00% | 0.4–0.8% |
| Chromium (Cr) | 17.0–19.0% | 17.5–18.5% |
| Nickel (Ni) | 10.0–14.0% | 11.0–12.5% |
| Molybdenum (Mo) | 2.0–3.0% | 2.2–2.8% |
| Iron (Fe) | Balance | — |
| Nitrogen (N) | ≤ 0.10% | 0.020–0.050% |
Mechanical Properties
| Property | Specification (Annealed Condition) |
|---|---|
| Tensile Strength (UTS) | ≥ 485 MPa (70 ksi) |
| Yield Strength (0.2% Offset) | ≥ 170 MPa (25 ksi) |
| Elongation (in 2D) | ≥ 35% |
| Hardness (HBW) | ≤ 217 |
| Density | 8.0 g/cm³ |
| Thermal Conductivity (at 100°C) | 16.3 W/(m·K) |
| Specific Heat | 500 J/(kg·K) |
| Thermal Expansion (20–100°C) | 16.0 × 10⁻⁶ /K |
Corrosion Resistance Characteristics
The addition of Molybdenum (Mo) at 2.0–3.0% provides 316L with superior resistance to pitting corrosion and crevice corrosion compared to 304/304L grades. The ultra-low carbon content eliminates the susceptibility to intergranular corrosion (IGC) that occurs in standard 316 when carbide precipitation happens at grain boundaries during welding or high-temperature exposure (425–870°C range).
Key corrosion resistance properties include:
- Excellent resistance to chlorides, sulfides, and acidic environments
- Resistance to stress corrosion cracking (SCC) in moderate chloride environments
- Non-magnetic in annealed condition
- Effective resistance to pitting and crevice corrosion up to approximately 60°C in dilute chloride solutions
- Resistance to a wide range of organic and inorganic chemicals
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6.00 mm – 38.10 mm (¼" – 1½") |
| Wall Thickness (WT) | 0.50 mm – 4.50 mm (0.020" – 0.180") |
| Coil Length | 600 m – 3,000 m (standard); custom lengths available |
| Coil Inner Diameter (ID) | 400 mm – 600 mm |
| Coil Outer Diameter (OD) | 1,200 mm – 1,500 mm |
| Surface Finish | 2B (cold-rolled, annealed, pickled), BA (Bright Annealed), or No. 4 finish |
| Surface Roughness (Ra) | ≤ 0.8 μm (2B finish); ≤ 0.4 μm (BA finish) |
| Roundness Tolerance | ± 0.1% of OD |
| OD Tolerance | ± 0.10 mm or ± 0.5% (whichever is greater) |
| WT Tolerance | ± 10% of nominal wall thickness |
| Helix (Longitudinal Straightness) | ≤ 1.5 mm/m |
| Standards | ASTM A213/A213M, ASME SA-213, EN 10216-5, GB/T 12771 |
| Heat Treatment | Solution annealed (1040–1120°C), followed by controlled cooling |
| Coil Weight | Up to 5,000 kg per coil (standard); custom configurations available |
Manufacturing Process
Process Flow
- Hot Rolling: Continuous casting → Hot rolling to produce seamless pipe/ERW pipe blanks
- Pickling & Descaling: Removal of mill scale and oxide layers through controlled acid pickling
- Cold Drawing / Cold Rolling: Precision sizing to achieve required OD and WT tolerances; multiple passes through reducing dies or rolling mills
- Intermediate Annealing: Periodic solution annealing (typically at 1,050–1,100°C) to relieve cold work stresses and restore ductility between reduction passes
- Final Cold Sizing: Precision calibration to achieve final dimensional accuracy
- Final Annealing & Pickling: Solution annealing at 1,040–1,120°C followed by rapid quench; subsequent acid pickling to produce clean, passive surface
- Straightening & Coiling: Controlled coiling on precision winding equipment to maintain dimensional integrity and avoid work hardening
- Quality Inspection: Non-destructive testing (NDT), dimensional verification, and chemical analysis
- Coil Packaging: Protective wrapping, strapping, and labeling for shipment
Critical Process Controls for Heat Exchanger Applications
Based on extensive field experience with heat exchanger coiled tube perforation incidents, the following process controls are essential:
- Surface Quality Control: Elimination of surface inclusions, scratches, and oxide defects that serve as initiation sites for pitting corrosion
- Residual Stress Management: Controlled coiling forces to prevent localized stress concentrations that may contribute to stress corrosion cracking (SCC)
- Material Homogeneity: Verification of uniform Mo and Cr distribution to prevent localized corrosion resistance variations
- Passivation Quality: Ensuring complete and uniform passive film formation to maximize corrosion resistance from the point of delivery
- Low Carbon Verification: Strict control of carbon content to prevent sensitization during downstream welding operations
Applications
Primary Applications
- Shell-and-Tube Heat Exchangers: Primary application for 316L coiled tubes; used in both tubeside and shellside configurations
- Plate Heat Exchangers: Fabrication of gasketed and brazed plate heat exchanger channels
- Condensers & Evaporators: Refrigeration and HVAC systems handling corrosive media
- Process Heat Exchangers: Chemical processing, petrochemical, and refining applications
- Sea Water Coolers: Marine and offshore cooling applications requiring chloride resistance
- Pharmaceutical Heat Exchangers: Clean-in-place (CIP) compatible heat exchange systems
- Food & Beverage Processing: Sanitary heat exchangers for dairy, brewing, and food processing
- Power Generation: Feedwater heaters, economizers, and condenser tubes
Perforation Failure Analysis — Critical Design Considerations
Field experience with 316L heat exchanger coiled tube perforation has identified the following primary failure mechanisms:
| Failure Mode | Cause | Mitigation Strategy |
|---|---|---|
| Pitting Corrosion | Chloride-induced breakdown of passive film; surface defects; crevice formation | Surface quality control; velocity management; periodic inspection |
| Crevice Corrosion | Stagnant zones at tube supports, gaskets, and deposits | Proper tube support spacing; smooth transitions; deposit prevention |
| Intergranular Corrosion (IGC) | Chromium carbide precipitation at grain boundaries during welding | Use of 316L (low carbon); post-weld annealing where feasible |
| Stress Corrosion Cracking (SCC) | Combined action of tensile stress, chlorides, and elevated temperature | Stress relief; temperature control; material upgrade to duplex if severe |
| Fretting Corrosion | Micro-motion between tube and tube sheet or support plates | Proper expansion fit; flexible support design |
| Erosion-Corrosion | High-velocity flow removing passive film faster than repassivation | Velocity limits (typically < 2.5 m/s); flow distribution optimization |
Quality Certifications
Applicable Standards & Certifications
- ASTM A213/A213M: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for High Temperature and High Pressure Boiler-Fired Heaters and Similar Applications
- ASME SA-213: Material Standard for Seamless and Welded Austenitic Stainless Steel Tubing for High Temperature and High Pressure Boiler-Fired Heaters
- EN 10216-5: Non-ferrous metal tubes for heat exchangers and similar applications — Part 5: Technical delivery conditions for austenitic stainless steel tubes
- GB/T 12771: Chinese National Standard for Stainless Steel Tubes for General Purposes
- ISO 9001:2015: Quality Management System certification for manufacturing processes
- EN 10204 3.1: Material test certificates with independent inspection
- API Monogram: Available for pressure-containing applications where applicable
- PED (Pressure Equipment Directive) 2014/68/EU: Compliance for EU market pressure equipment applications
- WRAS / NSF-61: Available for potable water contact applications
Testing & Inspection
- Hydrostatic testing at 1.5× working pressure (ASTM A213)
- Positive Material Identification (PMI) via optical emission spectrometry (OES)
- Eddy current testing (ECT) for wall thickness and defect detection
- Visual surface inspection at 2× magnification
- Chemical composition verification (spectrometric analysis)
- Dimensional inspection (OD, WT, roundness, straightness)
- Mechanical property verification (tensile testing, hardness testing)
- Corrosion resistance testing (ASTM A262 Practice E — intergranular corrosion; ASTM G48 — pitting corrosion)
Unique Selling Points
- Ultra-Low Carbon (316L) Grade: Carbon content ≤ 0.030% provides superior resistance to sensitization during welding, extending service life in heat exchanger applications where tube-to-tubesheet welding is critical
- Molybdenum Enhancement: 2.0–3.0% Mo content delivers significantly improved pitting and crevice corrosion resistance over standard 304L, making it suitable for chloride-containing process streams
- Continuous Coil Supply: Enables high-speed automated cutting and fabrication, reducing production time by up to 40% compared to individual tube lengths
- Minimal Material Waste: Coil format eliminates end-trim losses associated with cut-length delivery, providing material savings of 3–8% per order
- Precision Dimensional Accuracy: Tight OD and WT tolerances ensure proper fit in tube sheets and minimize fretting corrosion risk at tube-to-support interfaces
- Surface Quality Excellence: Premium cold-rolled and annealed surface finish minimizes initiation sites for pitting corrosion, directly addressing the primary failure mechanism observed in field perforation studies
- Full Traceability: Complete material certification from melt to coil, enabling root cause analysis and quality assurance throughout the supply chain
- Weldability: Excellent weldability in all positions with minimal distortion, enabling reliable tube-to-tubesheet and tube-to-baffle welding critical for heat exchanger integrity
Ordering Information
| Parameter | Details |
|---|---|
| Material Grade | ASTM A213 TP316L / SA-213 TP316L / EN 1.4404 |
| Supply Condition | <