Stainless Steel Coil Tube for Organic Heat Carrier Boiler Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous-length tubing product designed for high-temperature thermal fluid circulation systems, particularly organic heat carrier (OHC) boiler applications. Unlike conventional straight-length piping, coil tubes are supplied in continuous helical or spiral-wound configurations that eliminate the need for field welding at intermediate joints, thereby significantly reducing potential leak points and enhancing overall system integrity.
Based on extensive engineering analysis of organic heat carrier boiler coil tube failure modes — including thermal fatigue cracking, oxidation-induced wall thinning, vibration fatigue, and corrosive attack from degraded thermal oil — Wenzhou Jixing has developed coil tubes optimized for long service life under sustained high-temperature cyclic loading conditions.
Material & Properties
The coil tubes are fabricated from austenitic stainless steel grades selected for their superior resistance to thermal oxidation, thermal fatigue, and chemical degradation at elevated operating temperatures (up to 400°C / 752°F for standard thermal oil systems).
Key Material Grades
- ASTM A213 TP304 / TP316L — General-purpose austenitic grades offering excellent corrosion resistance and formability
- ASTM A213 TP321 / TP347 — Stabilized grades (Ti/Cb stabilized) for enhanced resistance to intergranular corrosion at elevated temperatures
- ASTM A213 TP310 / TP310S — High-chromium high-nickel grades for extreme thermal oxidation resistance at temperatures exceeding 300°C
- ASTM A269 TP316L — Low-carbon grade for improved weldability and resistance to pitting corrosion from acidic thermal oil degradation products
Mechanical Properties (Typical)
| Property | 304/304L | 316L | 321 | 310S |
|---|---|---|---|---|
| Tensile Strength (MPa) | ≥485 | ≥485 | ≥485 | ≥515 |
| Yield Strength (MPa, 0.2% offset) | ≥205 | ≥205 | ≥205 | ≥205 | Elongation (%) | ≥40 | ≥40 | ≥40 | ≥40 |
| Maximum Operating Temperature (°C) | 350 | 350 | 400 | 1100 |
| Thermal Oxidation Resistance (10,000 h @ 800°C) | Moderate | Moderate | Good | Excellent |
| Thermal Fatigue Cycles (to failure, ΔT=200°C) | ~1,500 | ~1,800 | ~2,500 | ~4,000+ |
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Applicable Standards | ASTM A213, ASTM A269, EN 10216-5, GB/T 14976 |
| Outer Diameter (OD) | 6.0 mm – 159.0 mm (customizable) |
| Wall Thickness | 0.5 mm – 12.0 mm |
| Coil Length (Continuous) | 50 m – 500 m per coil (no field joints) |
| Coil Diameter | 600 mm – 2,000 mm (shipping coil) |
| Surface Finish | 2B, BA (Bright Annealed), Electropolished (Ra ≤ 0.4 μm) |
| Tolerance (OD) | ±0.05 mm – ±0.15 mm (precision cold-rolled) |
| Tolerance (Wall Thickness) | ±0.03 mm – ±0.10 mm |
| End Condition | Plain ends, beveled ends, or threaded connections |
| Heat Treatment | Solution annealed and water quenched |
| Operating Pressure Rating | Up to 1.6 MPa (standard); 6.4 MPa (heavy-wall) |
| Operating Temperature Range | -50°C to +400°C (standard thermal oil systems) |
| Non-Destructive Testing | 100% Eddy Current (ET), 100% Hydrostatic Pressure Test |
Manufacturing Process
The production of high-performance stainless steel coil tubes at Wenzhou Jixing follows a rigorously controlled multi-stage process:
- Raw Material Selection & Inspection — Ingot certification, spectrographic analysis (PMI), and visual inspection of coil stock to ensure compliance with specified chemical composition.
- Cold Drawing / Cold Rolling — Precision cold-working of tube blanks through calibrated die sets to achieve exact dimensional tolerances and enhanced mechanical properties through work hardening.
- Intermediate Annealing — Recrystallization annealing at 1050°C – 1100°C in controlled atmosphere (N₂ + H₂) to relieve cold-work stresses and restore ductility for continued forming.
- Final Dimensional Forming — Final cold-drawing pass to achieve target OD and wall thickness with tight tolerance control.
- Final Annealing & Pickling — Solution annealing followed by acid pickling and passivation to remove scale, restore corrosion resistance, and achieve specified surface finish.
- Helical Coiling — Continuous coiling onto precision-wound shipping coils using tension-controlled winding equipment to prevent ovality and kinking.
- Non-Destructive Testing (NDT) — 100% inline eddy current testing for detection of internal/external defects, followed by 100% hydrostatic pressure testing at 1.5× design pressure.
- Final Inspection & Packaging — Dimensional verification, surface quality assessment, material traceability documentation, and protective packaging with coil saddles and moisture barriers.
Applications
- Organic Heat Carrier (OHC) Boiler Systems — Primary heat transfer coils in thermal oil furnaces, heaters, and dryers operating at 250°C – 400°C
- Industrial Process Heating — Continuous heating elements in polymer extrusion lines, rubber vulcanization, textile drying, and food processing
- Chemical Processing — Reactor coils, heat exchanger bundles, and distillation column internals where corrosion resistance and temperature cycling resistance are critical
- Power Generation — Auxiliary heating coils in combined heat and power (CHP) systems
- Pharmaceutical & Food Industry — Sanitary-grade coil tubes for CIP-compatible heating systems requiring smooth surface finishes
- Refinery & Petrochemical — Fired heater tube bundles and preheater coils
Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System certification
- EN 10204 3.1 — Material test certificates per European standard
- ASTM A213 / A269 — Full compliance with American Society for Testing and Materials specifications
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes
- Mill Test Reports (MTR) — Full chemical analysis and mechanical test data traceable to heat number
- NDT Reports — Eddy current and hydrostatic test reports for every coil produced
- PED (Pressure Equipment Directive) 2014/68/EU — Available for European market applications
- NACE MR0175 — Available for sour service applications requiring resistance to sulfide stress cracking
Unique Selling Points & Engineering Advantages
Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through deep engineering expertise in thermal oil system reliability:
- Zero-Field-Joint Configuration — Continuous coil supply eliminates the primary failure mechanism identified in organic heat carrier boiler leak analyses: welded joint degradation under thermal cycling.
- Failure-Mode-Informed Material Selection — Material grades are selected based on documented failure analysis of thermal oil coil tubes, prioritizing thermal fatigue resistance and oxidation stability over conventional cost-driven selection.
- Precision Dimensional Control — Tight tolerance manufacturing ensures uniform heat transfer coefficients and consistent flow dynamics throughout the entire coil length, preventing localized hot spots that accelerate degradation.
- Extended Service Life — Optimized wall thickness and material selection extend operational life by 30–50% compared to standard coil tubes in thermal oil service.
- Full Traceability — Every coil is traceable from raw material ingot through final delivery, supporting compliance audits and failure investigations.
- Custom Engineering Support — Technical consultation available for coil configuration, material selection, and system integration specific to customer thermal oil operating conditions.