Stainless Steel Spiral Coil Tube (Coiltube) — Product Technical Specification

Product Overview

The Stainless Steel Spiral Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. through cold-drawing, coiling, and forming processes. This product is designed primarily for use in spiral coil heat exchangers and related process equipment where fluid circulation, thermal exchange, and mechanical durability are critical performance parameters. The coil geometry provides a high surface-area-to-volume ratio, enabling efficient heat transfer in compact installations.

This specification draws upon advanced research into spiral coil heat exchangers handling solid-particle-laden water media (slurry service), addressing unique challenges such as particle-induced erosion, sedimentation, and fouling that distinguish slurry applications from conventional clean-fluid service.

Material & Properties

The Coiltube is fabricated from austenitic stainless steel grades selected for their superior combination of corrosion resistance, mechanical strength, and thermal conductivity. The primary material grades include:

• AISI 304 (UNS S30408) — General-purpose grade with excellent resistance to atmospheric and mild chemical corrosion. Chromium (Cr) content of 18–20% and Nickel (Ni) content of 8–10.5% provide robust passive film formation.
• AISI 316 (UNS S31608) — Enhanced grade with Molybdenum (Mo) addition (2–3%) for superior resistance to chlorides, acids, and marine environments. Preferred for slurry and chemical processing applications.
• AISI 321 (UNS S32108) — Stabilized with Titanium (Ti) to prevent intergranular corrosion during welding and high-temperature service (up to 870 °C).
• AISI 316L (UNS S31603) — Low-carbon variant (C ≤ 0.03%) offering enhanced weldability and resistance to sensitization.

Key Mechanical Properties (AISI 316, Reference Values):

• Tensile Strength: ≥ 515 MPa
• Yield Strength: ≥ 205 MPa
• Elongation: ≥ 40%
• Hardness: ≤ 253 HB (annealed condition)
• Thermal Conductivity: 16.3 W/(m·K) at 100 °C
• Operating Temperature Range: −196 °C to +650 °C

Specifications

Parameter	Specification	Unit	Notes
Outer Diameter (OD)	6.0 – 50.8	mm	Custom diameters available upon request
Wall Thickness	0.5 – 3.0	mm	±10% tolerance
Coil Diameter (Pitch)	100 – 2000	mm	Adjustable per heat exchanger design
Coil Length (Unwound)	1 – 200	m	Determined by application requirements
Number of Turns	5 – 500	—	Dependent on coil diameter and length
Surface Finish	2B / BA / Pickled & Passivated	—	Ra ≤ 0.8 μm for sanitary applications
End Condition	Plain / Threaded / Flanged / Beveled	—	Custom end preparation available
Material Grade	304 / 304L / 316 / 316L / 321	—	Equivalent: 06Cr19Ni10 / 06Cr17Ni12Mo2
Pressure Rating	Up to 4.0	MPa	Hydrostatic test at 1.5× working pressure
Standard Reference	ASTM A269 / ASTM A270 / GB/T 12771 / EN 10216-5	—	Manufactured per applicable international standards

Manufacturing Process

The production of stainless steel Coiltube follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:

1. Raw Material Inspection — Incoming stainless steel seamless tubes or welded pipes undergo 100% material verification, including spectrographic analysis (OES) for chemical composition and visual/ultrasonic inspection for surface defects.
2. Cold Drawing (Optional) — Tubes requiring tight dimensional tolerances are cold-drawn through calibrated dies to achieve precise outer diameter and wall thickness specifications while enhancing mechanical properties.
3. Coil Forming — Straight tubes are fed into a computer-controlled coil bending machine. The bending process employs a hydraulic system with programmable die sets to produce uniform helical geometry with controlled pitch, avoiding material thinning, wrinkling, or cross-sectional distortion.
4. Heat Treatment (if applicable) — For grades requiring stress relief or solution annealing, coils are subjected to controlled thermal cycles (typically 1050–1150 °C followed by water quenching) to restore full austenitic microstructure and optimize corrosion resistance.
5. Pickling & Passivation — A chemical treatment using a mixed acid solution (nitric acid + hydrofluoric acid) removes surface scale and contaminants, followed by a passivation step to re-establish a stable chromium oxide (Cr₂O₃) passive film on the surface.
6. Quality Inspection — Final products undergo dimensional verification (OD, wall thickness, coil pitch, length), hydrostatic pressure testing, and visual inspection. Non-destructive testing (NDT) methods such as eddy current testing may be applied for wall thickness verification.
7. Packaging & Dispatch — Coils are wrapped in protective film, secured with steel strapping, and packed in wooden crates or on export-grade pallets to prevent mechanical damage during transit.

Applications

The stainless steel Coiltube finds extensive application across multiple industrial sectors, particularly where thermal management of fluids — including solid-particle-laden media — is required:

• Spiral Coil Heat Exchangers — Primary application domain. The helical geometry promotes turbulent flow, enhancing heat transfer coefficients (U-values) by 2–3× compared to straight-tube configurations. Particularly effective in slurry cooling systems where solid particles suspended in water media (e.g., mineral slurries, cement pastes, wastewater with sediment) require efficient heat removal while resisting erosion.
• Chemical Processing — Reactor cooling coils, condenser coils, and heat recovery units in processes involving aggressive chemicals, acids, and caustic solutions.
• Pharmaceutical & Food Industry — Sanitary-grade coils (BA finish, Ra ≤ 0.4 μm) for pasteurization, sterilization (SIP/CIP), and thermal processing of food and pharmaceutical products.
• Power Generation — Condenser tubes and feedwater heaters in thermal power plants and nuclear facilities.
• Oil & Gas — Subsea heat exchangers, process fluid cooling, and gas conditioning systems requiring resistance to chloride-induced stress corrosion cracking (SCC).
• Marine & Offshore — Seawater cooling coils, ballast water management systems, and shipboard thermal management.
• Mining & Mineral Processing — Slurry heat exchangers for cooling ore slurries, tailings processing, and leaching circuits where solid particle concentrations are high.
• Waste Water Treatment — Heat recovery from industrial effluents containing suspended solids.

Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring product conformity with international standards:

• ISO 9001:2015 — Quality Management System certification
• ISO 14001:2015 — Environmental Management System certification
• ASME BPV Code — Boiler and Pressure Vessel Code compliance (where applicable for pressure-rated applications)
• CE Marking — European Conformity for machinery directive compliance
• ASTM / ASME — Material and fabrication standards compliance (ASTM A269, A270; ASME B31.3)
• GB/T 12771 — Chinese national standard for stainless steel seamless and welded tubes
• EN 10216-5 — European standard for austenitic stainless steel tubes
• Mill Test Certificates (MTC/EN 10204 3.1) — Provided with each shipment, documenting chemical composition, mechanical properties, and heat treatment records
• Third-Party Inspection — Available upon request (SGS, Bureau Veritas, DNV, Lloyd's Register)

Unique Selling Points

The Coiltube product line from Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through the following competitive advantages:

• Slurry-Service Optimized Design — Informed by research into solid-particle water media heat exchange, the coil geometry and material selection are specifically optimized to mitigate particle-induced erosion and sedimentation effects. Increased wall thickness options and enhanced surface finishes reduce wear rates in abrasive slurry environments.
• Superior Heat Transfer Performance — The helical coil geometry induces secondary flow (Dean vortices) within the tube, significantly enhancing turbulence and convective heat transfer coefficients. This results in compact, high-efficiency heat exchanger designs with reduced footprint.
• Full Material Spectrum — Availability across AISI 304, 304L, 316, 316L, and 321 grades allows customers to select the optimal material for their specific corrosion, mechanical, and thermal requirements.
• Customization Capability — Flexible manufacturing capacity accommodates custom outer diameters, wall thicknesses, coil pitches, and lengths tailored to specific heat exchanger designs and process requirements.
• End-to-End Quality Assurance — From raw material verification through final inspection and certification, a documented quality chain ensures traceability and compliance with international standards.
• Cost-Effective Solution — Cold-forming processes minimize material waste and energy consumption compared to hot-forming alternatives, delivering high-performance products at competitive price points.

Technical Notes on Slurry Media Applications

Research into spiral coil heat exchangers containing solid-particle water media has identified several critical design considerations that inform the Coiltube product specifications:

• Erosion Resistance — Solid particles (typically 50–500 μm in diameter) suspended in the water medium impinge upon the tube inner surface, causing abrasive wear. The selection of higher-hardness austenitic grades (e.g., 316L with work-hardened surface) and adequate wall thickness (≥ 1.0 mm for high-concentration slurries) is recommended.
• Fouling Management — Particle deposition on tube surfaces increases thermal resistance and reduces heat transfer efficiency. The curved geometry of the coil generates centrifugal forces that partially counteract sedimentation, but periodic cleaning intervals must be established based on particle concentration and fluid velocity.
• Flow Velocity Considerations — Minimum fluid velocities of 1.5–2.5 m/s are recommended to maintain particle suspension and prevent settling within the coil passages. Higher velocities increase erosion rates, necessitating a balance between flow-induced cleaning and material wear.
• Pressure Drop — The helical geometry introduces additional frictional pressure losses compared to straight tubes. Design calculations must account for Dean number effects (De = Re × √(d/D), where d is tube diameter and D is coil diameter) to ensure adequate pump capacity.

For detailed engineering consultation, material selection guidance, or custom Coiltube specifications, contact Wenzhou Jixing Metal Materials Co., Ltd. technical sales team.