Stainless Steel Coil Tube (Coiltube) – Product Technical Specification

Product Overview

The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, designed for high-performance fluid transfer, heat exchange, and structural applications across industrial, commercial, and engineering sectors. Delivered in continuous coil form, the product facilitates downstream processing including straightening, cutting, bending, and welding with minimal material waste and maximum production efficiency.

This specification draws upon engineering experience documented in the "Technical Summary of Centralized Control Systems for Fan Coil Units in Building Engineering", underscoring the critical role of stainless steel coil tubes in hydronic distribution networks, chilled water circulation loops, and integrated HVAC (Heating, Ventilation, and Air Conditioning) system architectures.

Material & Properties

Coiltube products are fabricated from austenitic stainless steel grades conforming to international standards, selected for superior corrosion resistance, mechanical integrity, and thermal conductivity. The primary material grades include:

• SUS304 / AISI 304 – General-purpose austenitic stainless steel with excellent formability and weldability; suitable for non-aggressive environments.
• SUS316 / AISI 316 – Molybdenum-enhanced grade offering superior resistance to pitting and crevice corrosion; ideal for chemical and marine applications.
• SUS321 / AISI 321 – Titanium-stabilized grade with enhanced resistance to intergranular corrosion at elevated temperatures (up to 870 °C / 1598 °F).
• SUS304L / AISI 304L – Low-carbon variant with reduced carbon content (≤ 0.03%) for improved resistance to carbide precipitation during welding.

Key Mechanical Properties (Typical Values)

• Tensile Strength (UTS): 515–730 MPa (75,000–106,000 psi)
• Yield Strength: 205–310 MPa (29,700–45,000 psi)
• Elongation at Break: ≥ 40%
• Hardness (Brinell): 150–220 HB
• Thermal Conductivity: 14.9–16.3 W/(m·K) at 20 °C
• Linear Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100 °C)

Specifications

Parameter	Specification / Range	Standard Reference
Outer Diameter (OD)	6.0 mm – 168.3 mm (¼" – 6")	ASTM A554 / EN 10217
Wall Thickness (WT)	0.3 mm – 6.0 mm (0.012" – 0.236")	ASTM A554 / EN 10217
Inner Diameter (ID)	Calculated: ID = OD − 2 × WT	—
Coil Length	50 m – 300 m (164 ft – 984 ft) per coil	Manufacturer's specification
Coil Inner Diameter (C-ID)	200 mm – 600 mm (7.9" – 23.6")	Customer-specified
Surface Finish	No. 1 (Hot Rolled), 2B, BA (Bright Annealed), Pickled & Passivated	ASTM A480
Roughness (Ra)	0.4 µm – 2.0 µm (depending on finish grade)	ISO 1302
Temperature Range	−196 °C to +870 °C (−321 °F to +1598 °F)	ASTM A554
Maximum Working Pressure	Up to 4.0 MPa (580 psi) – dependent on dimensions and grade	ASME B31.3 / EN 13480
Tolerance – OD	± 0.1 mm to ± 0.5 mm (per DIN 2391 / EN 10217 Class A/B)	EN 10217 / DIN 2391
Tolerance – WT	± 10% of nominal wall thickness	EN 10217 / ASTM A554
Heat Treatment	Annealed and Pickled (AP); Solution Annealed	ASTM A554
End Condition	Open coil ends with protective caps or sealed	Customer requirement
Packaging	Wooden pallet with VCI (Vapor Corrosion Inhibitor) film wrapping	ISO 12040

Manufacturing Process

Step-by-Step Production Workflow

1. Raw Material Selection & Inspection: Stainless steel strip or coil is sourced from certified mills and subjected to incoming quality control including visual inspection, chemical composition analysis (OES – Optical Emission Spectrometry), and mechanical property verification.
2. Slitting & Edge Trimming: The master coil is slit to the required width using precision slitting lines, ensuring clean, burr-free edges suitable for subsequent forming operations.
3. Tube Forming (Roll Forming / Welding): The flat strip is passed through a series of progressive forming rolls to achieve the desired cross-sectional geometry. Seams are welded using either ERW (Electric Resistance Welding), MIG (Metal Inert Gas Welding), or orbital TIG (Tungsten Inert Gas Welding) depending on the application requirements.
4. Heat Treatment & Annealing: Welded tubes undergo controlled solution annealing at temperatures between 1010 °C and 1150 °C, followed by rapid cooling (air or water quench) to restore full austenitic microstructure and relieve residual welding stresses.
5. Pickling & Passivation: Tubes are immersed in mixed acid baths (HNO₃ / H₃PO₄) to remove mill scale, heat treatment discoloration, and surface contaminants. A final passivation step establishes a stable chromium oxide protective film on the surface.
6. Coiling & Sizing: Finished tubes are coiled onto precision-wound cores with controlled tension to prevent deformation, kinking, or ovality. Coil dimensions are verified against order specifications.
7. Final Quality Assurance: Each coil undergoes dimensional inspection (OD, WT, straightness), hydrostatic pressure testing, surface finish verification, and non-destructive testing (NDT) including eddy current or ultrasonic examination as applicable.
8. Packaging & Dispatch: Coils are wrapped with protective film, secured on wooden pallets, and labeled with traceability documentation including heat numbers, mill certificates, and inspection reports.

Applications

Primary Application Domains

• HVAC & Building Services Engineering: Stainless steel coil tubes serve as chilled water supply and return piping, heating medium distribution lines, and hydronic loop components within fan coil unit (FCU) centralized control systems. Their corrosion resistance and long service life make them ideal for concealed building infrastructure where maintenance access is limited.
• Food & Beverage Processing: Used in sanitary piping systems for milk, juice, and pharmaceutical fluid transfer where hygiene compliance (3-A Sanitary Standards, FDA 21 CFR) is mandatory.
• Chemical & Petrochemical Industry: Deployed in process piping, heat exchanger bundles, and reactor internals handling aggressive chemical media, acidic solutions, and high-temperature gases.
• Marine & Offshore Engineering: Utilized in ballast water systems, fuel oil transfer lines, and structural tubing in environments exposed to saltwater corrosion.
• Automotive & Aerospace: Employed in exhaust systems, fuel lines, hydraulic circuits, and structural tubing requiring high strength-to-weight ratios.
• Medical & Laboratory Equipment: Applied in autoclave components, sterilization chambers, and fluid delivery systems requiring biocompatibility and resistance to repeated high-temperature cycling.

Integration with Centralized Control Systems

As documented in engineering case studies of fan coil unit (FCU) centralized control architectures, stainless steel coil tubes provide the foundational hydraulic infrastructure for variable refrigerant flow (VRF) systems, constant volume and variable volume hydronic loops, and smart building management interfaces. The predictable thermal expansion characteristics and dimensional stability of stainless steel coil tubes ensure reliable performance under the cyclic thermal loading inherent in centralized HVAC control strategies.

Quality Certifications & Compliance

International Standards & Certifications

• ISO 9001:2015 – Quality Management System certification ensuring consistent product quality and process control throughout the manufacturing chain.
• ISO 14001:2015 – Environmental Management System certification demonstrating commitment to sustainable manufacturing practices and waste minimization.
• ISO 45001:2018 – Occupational Health and Safety Management System certification.
• ASTM A554 – Standard Specification for Cold-Wrought Austenitic Stainless Steel Seamless Tubing (applied by analogy for welded coil tubing dimensional and material requirements).
• EN 10217 – Technical Delivery Conditions for Ferritic, Martensitic, Austenitic, and Duplex Stainless Steel Tubes for Pressure Purposes.
• DIN 2391 – Stainless Steel Tubes for Technical Purposes – General Technical Delivery Conditions.
• ASME B31.3 – Process Piping Code compliance for industrial applications.
• CE Marking – Conformity with European Union directives for machinery and pressure equipment (PED 2014/68/EU).
• Mill Test Certificates (MTC) – EN 10204 3.1 and 3.2 certificates provided with every shipment, documenting chemical composition, mechanical properties, and heat treatment records.
• Third-Party Inspection – Available upon request through accredited bodies (SGS, BV, TUV, Lloyd's Register).

Unique Selling Points

1. Superior Corrosion Resistance: Austenitic stainless steel matrix with optional molybdenum and titanium alloying provides exceptional resistance to atmospheric, chemical, and electrochemical degradation—eliminating the need for secondary coatings or cathodic protection systems.
2. Continuous Coil Format: Delivered as seamless coils rather than discrete lengths, enabling continuous automated processing, reduced joint counts, lower leakage risk, and minimized material waste in downstream fabrication.
3. Precision Dimensional Tolerances: Tight manufacturing tolerances (± 0.1 mm on OD) ensure reliable fit-up with fittings, flanges, and heat exchanger tubesheets without excessive machining or gasket compensation.
4. Weldability & Formability: Fully annealed and solution-treated condition permits cold forming, welding, and machining without cracking or distortion, accommodating complex geometries in custom fabrication.
5. Wide Temperature & Pressure Envelope: Operational range spanning cryogenic (−196 °C) to high-temperature (870 °C) service with no loss of mechanical properties—unlike carbon steel alternatives.
6. Hygienic Surface Quality: BA (Bright Annealed) and electropolished finishes achieve Ra values below 0.4 µm, facilitating clean-in-place (CIP) and steam-in-place (SIP) sanitization protocols.
7. Full Traceability: Each coil is traceable to its mill heat number with complete documentation of chemical analysis, mechanical testing, and process history—essential for regulated industries.
8. Engineered for Centralized Control Integration: Dimensional consistency and predictable thermal behavior make these coil tubes ideal for integration into automated, sensor-driven centralized control systems where piping geometry directly impacts flow dynamics and control accuracy.

Technical Notes & Handling Recommendations

• Store coils in a dry, ventilated environment at ambient temperature; avoid direct contact with carbon steel to prevent galvanic corrosion.
• Use dedicated stainless steel handling equipment (slings, hooks, roller stands) to avoid surface marking or contamination.
• When welding stainless steel coil tubes, use low-heat-input techniques with inert gas shielding (Ar/He mixture) and maintain interpass temperature below 150 °C to prevent sensitization.
• Post-weld passivation treatment is recommended for welded assemblies exposed to corrosive environments to restore the protective chromium oxide layer.
• For applications involving chloride-containing fluids, verify compatibility with the selected grade (SUS316L recommended for chloride exposure above 50 ppm).

Supplier Information

Wenzhou Jixing Metal Materials Co., Ltd is a specialized manufacturer and distributor of stainless steel tubular products based in Wenzhou, Zhejiang Province, China. The company maintains an integrated production facility capable of supplying custom-dimension coil tubes, straight lengths, and fabricated assemblies to meet diverse engineering requirements across global markets.