Stainless Steel Coil Tube (Coiltube) — Industrial Heat-Exchange Application
Produced by Wenzhou Jixing Metal Materials Co., Ltd., the Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product designed for demanding industrial heat-transfer environments, particularly in high-temperature roasting furnaces, calcination chambers, and continuous thermal processing systems. This product series addresses critical challenges such as tube wall thinning, thermal fatigue cracking, and premature leakage failure observed in conventional cooling coil assemblies.
1. Product Overview
The Coil Tube is manufactured as a continuous, cold-formed stainless steel tube wound into a compact spiral configuration. Unlike straight pipe sections that require field welding and bending, coil tubes are delivered in pre-formed coil geometry, enabling rapid installation and superior structural integrity. The product is specifically engineered to withstand cyclic thermal loading, corrosive flue gas environments, and mechanical vibration inherent in roasting furnace cooling systems.
Based on extensive field research and technical studies — including investigations into 109 m² roasting furnace cooling coil leakage failures — this product incorporates material selection, dimensional tolerances, and surface treatment strategies optimized to extend service life and reduce unplanned downtime.
2. Material & Properties
2.1 Base Alloy Options
- SUS 304 (UNS S30408) — General-purpose austenitic stainless steel; excellent formability and moderate corrosion resistance. Suitable for temperatures up to 870 °C.
- SUS 321 (UNS S32108) — Ti-stabilized austenitic grade; superior resistance to intergranular corrosion and thermal cycling. Recommended for furnace cooling duty above 600 °C.
- SUS 310S (UNS S31008) — High-temperature austenitic grade with elevated Cr (25%) and Ni (19%); sustained service capability up to 1150 °C. Preferred for extreme thermal environments.
- SUS 316L (UNS S31603) — Low-carbon Mo-bearing grade; enhanced resistance to pitting and crevice corrosion in halide-containing flue gas atmospheres.
2.2 Key Mechanical & Physical Properties (Typical — Annealed Condition)
| Property | SUS 304 | SUS 321 | SUS 310S | SUS 316L |
|---|---|---|---|---|
| Tensile Strength (MPa, min.) | 515 | 515 | 515 | 485 |
| Yield Strength (MPa, min.) | 205 | 205 | 205 | 170 | Elongation (% min.) | 40 | 40 | 40 | 40 |
| Maximum Service Temperature (°C) | 870 | 900 | 1150 | 870 |
| Thermal Conductivity (W/m·K @ 100°C) | 16.3 | 16.3 | 16.3 | 16.3 |
| Density (g/cm³) | 8.0 | 8.0 | 8.0 | 8.0 |
2.3 Corrosion Resistance
All grades exhibit a passive chromium oxide film (Cr₂O₃) that self-heals in oxidizing environments. SUS 321 and SUS 310S demonstrate superior resistance to scaling and oxidation at elevated temperatures, directly contributing to extended coil tube service life in roasting furnace applications. The low-carbon variants (316L) minimize sensitization risk during welding operations.
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Outer Diameter (OD) | Φ 8 mm – Φ 60 mm (custom sizes available) |
| Wall Thickness (WT) | 0.5 mm – 3.0 mm |
| Coil Diameter (CD) | Φ 100 mm – Φ 1500 mm |
| Coil Length (per coil) | Up to 300 m (continuous) |
| Coil Weight | Up to 2,000 kg per coil |
| Surface Finish | Ba&W (Bright & Wavy), 2B, No.4, or custom |
| Inner Surface Roughness (Ra) | ≤ 0.8 μm (standard); ≤ 0.4 μm (polished) |
| Pressure Rating | Up to 4.0 MPa (PN40), depending on dimensions |
| Temperature Range | −196 °C to +1150 °C (grade-dependent) |
| Standards Compliance | ASTM A213, ASTM A269, EN 10216-5, GB/T 12771 |
| End Treatment | Plain end, beveled, or threaded (upon request) |
| Material Form | Seamless (cold-drawn) or welded (ERW/SAW) |
4. Manufacturing Process
- Material Selection & Inspection — Ingot certification and spectral analysis (PMI) to confirm alloy composition per ASTM/EN specifications.
- Hot Rolling & Annealing — Billet or bar stock is hot-rolled to near-final dimensions, followed by controlled furnace annealing to achieve full solution treatment and grain homogeneity.
- Acid Pickling & Descaling — Immersion in mixed acid baths (HNO₃ + HF) to remove oxide scale and restore passive film integrity.
- Cold Drawing / Cold Bending — Tube blank is cold-drawn through precision dies to achieve final OD and WT tolerances (±0.05 mm OD; ±10% WT).
- Coil Winding — Continuous tube is wound onto precision mandrels using CNC-controlled coil winding machines, maintaining consistent bend radius (minimum 3× OD) and inter-pass spacing.
- Stress Relief Annealing — Post-forming annealing at 1050–1150 °C (air or vacuum) to relieve residual cold-work stresses and prevent stress-corrosion cracking.
- Final Surface Treatment — Optional electropolishing, passivation, or mechanical polishing to achieve required surface roughness and corrosion resistance.
- Non-Destructive Testing (NDT) — 100% eddy current testing (ECT) and hydrostatic pressure testing (1.5× working pressure) to detect wall thinning, cracks, or weld defects.
- Packaging & Dispatch — Coils are wrapped in VCI (Vapor Corrosion Inhibitor) film, secured on wooden pallets, and labeled with material traceability data.
5. Applications
- Roasting Furnace Cooling Systems — Primary application; coil tubes serve as heat-exchange elements in copper, zinc, and lead roasting furnaces, absorbing excess heat from flue gas to protect furnace linings and recover thermal energy.
- Calcination & Sintering Kilns — Cooling gas channels in rotary kilns and shaft kilns for cement, lime, and mineral processing.
- Chemical Reactor Cooling — Internal coil heat exchangers in high-temperature polymerization and hydrogenation reactors.
- Petrochemical Reformer Furnaces — Coil tubes in catalytic reforming units operating at 500–900 °C with hydrocarbon-rich atmospheres.
- Power Generation — Boiler economizer and superheater coil assemblies in waste-heat recovery systems.
- Food & Pharmaceutical Processing — Sanitary-grade coil heat exchangers for pasteurization and sterilization equipment (316L grade, electropolished finish).
- Heat Recovery Steam Generators (HRSG) — Coil elements in combined-cycle power plant waste-heat recovery systems.
6. Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System certification for manufacturing processes.
- ISO 14001:2015 — Environmental Management System compliance.
- CE Marking — Conformity with European Pressure Equipment Directive (PED 2014/68/EU) for pressure-rated applications.
- EN 10204 3.1 / 3.2 — Material test certificates per European standard.
- ASTM A213 / A269 — Full compliance with American Society for Testing and Materials standards for stainless steel tubing.
- Mill Test Reports (MTR) — Each coil shipment includes certified chemical analysis, mechanical test data, and heat number traceability.
- NACE MR0175 / ISO 15156 — Available for oil and gas applications requiring resistance to sulfide stress cracking.
7. Unique Selling Points
Based on documented engineering studies addressing cooling coil leakage failures in large-scale roasting furnaces (109 m² effective heat-transfer area), this product line incorporates the following performance enhancements:
- Extended Service Life — Optimized alloy selection (SUS 321/310S) and wall thickness engineering reduce thermal fatigue crack initiation rates by up to 60% compared to conventional 304 coil assemblies.
- Leakage Prevention — 100% eddy current inspection and hydrostatic testing eliminate sub-surface defects that lead to catastrophic tube rupture under thermal cycling.
- Superior Formability — Cold-drawn coil geometry with controlled minimum bend radius prevents ovalization and wall thinning at coil turns, maintaining uniform heat-transfer efficiency across the full coil length.
- Custom Engineering Support — Wenzhou Jixing provides application-specific coil design, including heat-load calculations, bend radius optimization, and support bracket configuration for specific furnace geometries.
- Full Traceability — Each coil is heat-number traceable from raw material ingot through final dispatch, enabling root-cause analysis in the event of field performance issues.
8. Technical Advisory
For roasting furnace cooling coil applications, the following design recommendations are provided based on field experience:
- Minimum wall thickness of 1.5 mm is recommended for furnace outlet temperatures exceeding 700 °C to resist hot oxidation and thermal erosion.
- Inter-pass coil spacing should not exceed 25 mm to ensure uniform gas flow distribution and prevent localized overheating.
- Regular inspection intervals of 6–12 months with ultrasonic wall thickness measurement are advised for continuous duty operation.
- Flue gas velocity through coil passages should be maintained between 3–8 m/s to balance heat-transfer efficiency against erosive wear.
For detailed quotations, custom coil design engineering, or material specification consultation, contact Wenzhou Jixing Metal Materials Co., Ltd. directly. All products are manufactured to order with lead times of 15–30 calendar days depending on specification complexity and quantity.