Stainless Steel Coil Tube — Fan Coil Unit Grade
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered coiled tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for use in fan coil units (FCU) and heat exchange applications. This product combines the superior corrosion resistance and mechanical integrity of stainless steel with the compact, high-efficiency geometry of a continuous coil form, enabling optimal heat transfer performance in HVAC (Heating, Ventilation, and Air Conditioning) systems, refrigeration circuits, and industrial thermal management installations.
The coil tube is supplied in continuous coil form to facilitate seamless integration into manufacturing lines, minimizing waste and maximizing production efficiency for downstream fabricators and system integrators.
2. Material & Properties
The coil tube is fabricated from high-quality austenitic stainless steel, primarily AISI 304 (UNS S30400) and AISI 316L (UNS S31603), selected for their outstanding resistance to intergranular corrosion, pitting, and stress corrosion cracking in aqueous and chemical environments.
Key Material Properties
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and mild chemical environments; 316L grade provides enhanced resistance to chlorides and marine atmospheres.
- Mechanical Strength: Tensile strength of 515–720 MPa (depending on grade and condition); elongation of ≥30% in annealed condition.
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, suitable for efficient heat exchange applications.
- Operating Temperature Range: −196°C to +870°C (continuous service).
- Hygienic Surface: Internal surface roughness (Ra) ≤ 0.4 μm available upon request, meeting sanitary-grade requirements.
- Non-Magnetic: Austenitic microstructure ensures non-magnetic properties in annealed condition.
3. Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Material Grade | AISI 304 / 304L / 316L / 321 (custom available) |
| Outer Diameter (OD) | 6.0 mm – 50.0 mm (custom dimensions available) |
| Wall Thickness | 0.3 mm – 3.0 mm (custom tolerances available) |
| Coil Diameter (CD) | Standard coil diameters from 200 mm to 1000 mm |
| Coil Length | Continuous coil; typical lengths 100 m – 1000 m per coil |
| Surface Finish | 2B (cold rolled & annealed), No.4 (brushed), BA (bright annealed), mirror polish (600#–1500#) |
| Internal Surface Roughness (Ra) | ≤ 0.8 μm (standard); ≤ 0.4 μm (electropolished); ≤ 0.2 μm (custom) |
| Tolerance (OD) | ±0.05 mm to ±0.1 mm (per ISO 1307 / ASTM A269) |
| Tolerance (Wall Thickness) | ±10% of nominal thickness |
| Standard Reference | ASTM A269 / A270, EN 10217, GB/T 12771, JIS G3459 |
| Heat Treatment | Solution annealed (1050°C – 1100°C, water quench) |
| Coil Weight | Typically 200 kg – 800 kg per coil (customizable) |
| End Treatment | Plain ends, chamfered, or beveled per customer specification |
4. Manufacturing Process
The coil tube production at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: Ingot or hot-rolled coil stock is sourced from certified mills with full traceability documentation (Mill Test Certificates, MTC) conforming to ISO 3760-1.
- Hot Rolling & Annealing: Billets are hot-rolled into seamless tube blanks and solution-annealed to achieve a fully austenitic microstructure with residual stresses relieved.
- Pilger Milling / Cross-Rolling: The tube blanks are cold-worked through precision pilger or cross-rolling mills to achieve the target outer diameter and wall thickness with tight tolerances.
- Cold Drawing: For thinner wall sections, cold drawing through calibrated dies ensures uniform wall thickness and superior surface finish.
- Solution Annealing & Pickling: Tubes are re-annealed at 1050°C–1100°C with rapid water quenching, followed by acid pickling and passivation to remove surface contaminants and restore the protective chromium oxide layer.
- Coiling: Annealed tubes are fed through precision coiling heads to form continuous coils of the specified coil diameter. The coiling process is controlled to prevent surface damage, kinking, or ovality.
- Quality Inspection: Every coil undergoes ultrasonic testing (UT) for internal defects, eddy current testing for surface discontinuities, dimensional verification, and chemical composition analysis via optical emission spectrometry (OES).
- Packaging & Dispatch: Coils are wrapped with moisture-resistant protective film, sleeved with wooden or steel end caps, and secured on export-grade pallets for safe transportation.
5. Applications
The stainless steel coil tube is engineered for demanding thermal and fluid handling applications, including but not limited to:
- Fan Coil Units (FCU): Primary application — used as heat exchange coils in commercial and residential HVAC systems for efficient air conditioning and heating. The coil geometry maximizes surface area-to-volume ratio for superior heat transfer while the stainless steel construction ensures long-term resistance to corrosion from circulating water and condensate.
- Heat Exchangers & Condensers: Double-pipe and shell-and-tube heat exchangers in industrial processes, refrigeration systems, and cryogenic applications.
- Refrigeration & Air Conditioning: Evaporator and condenser coils for chillers, air handlers, and rooftop units.
- Food & Beverage Industry: Sanitary-grade coil tubes for pasteurization, brewing, dairy processing, and CIP (Clean-in-Place) systems where hygienic internal surfaces are critical.
- Pharmaceutical & Biotechnology: Process coils for clean steam generation, condensate return, and utility loops in GMP (Good Manufacturing Practice) facilities.
- Chemical & Petrochemical: Corrosion-resistant heat transfer coils for aggressive chemical environments, particularly with 316L grade in chloride-containing media.
- Marine & Offshore: Heat exchange coils in ballast water treatment systems, cooling loops, and HVAC installations on vessels and offshore platforms.
- Automotive & Aerospace: Precision coil tubes for fuel cell systems, thermal management, and lightweight heat exchanger cores.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications to ensure product reliability and international market acceptance:
- ISO 9001:2015 — Quality Management System certification for consistent product quality and continuous improvement.
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices.
- ISO/TS 22163 — Quality management systems for the automotive industry (IATF 16949 aligned).
- EN 10204 3.1 — Third-party certified material test documentation for every production lot.
- CE Marking — Conformity with European Union directives for pressure equipment and machinery safety.
- PED (Pressure Equipment Directive) 2014/68/EU — Compliance for pressure-containing applications.
- NSF/ANSI 61 — Drinking water system components certification (available for sanitary grades).
- WRAS (Water Regulations Advisory Scheme) — UK drinking water approval for potable water applications.
- Food Grade Certification — Compliance with FDA 21 CFR and EU 1935/2004 for food contact materials.
7. Unique Selling Points
- Integrated Coil Form Factor: Supplied in ready-to-use continuous coil form, reducing downstream processing time, eliminating butt-weld joints, and minimizing material waste — delivering a seamless, leak-free heat exchange circuit.
- Precision Dimensional Control: Tight tolerance manufacturing (OD ±0.05 mm) ensures reliable crimping, brazing, and mechanical fitting into fan coil unit headers and manifolds.
- Superior Corrosion Performance: 316L grade option with molybdenum alloying provides outstanding resistance to chloride-induced pitting and crevice corrosion, extending service life in humid, coastal, and chemically aggressive environments.
- Hygienic Internal Surface: Electropolished and passivated interiors (Ra ≤ 0.4 μm) prevent biofilm formation and facilitate easy cleaning — critical for food, beverage, and pharmaceutical applications.
- Full Traceability: Every coil is accompanied by a mill test certificate (MTC) with chemical composition, mechanical properties, heat treatment records, and non-destructive testing results — ensuring complete supply chain traceability.
- Customization Capability: Flexible production parameters (OD, wall thickness, coil diameter, surface finish, length) allow tailored solutions for specific engineering requirements and OEM specifications.
- Cost-Effective Lifecycle: The combination of long service life, low maintenance requirements, and recyclability of stainless steel delivers a superior total cost of ownership (TCO) compared to carbon steel or copper alternatives.
8. Technical Notes & Recommendations
Installation Guidance: When deploying the coil tube in fan coil unit assemblies, ensure proper support and vibration isolation to prevent fatigue failure at coil bends. Maintain a minimum bend radius of 3× the outer diameter to avoid wall thinning and ovality. For brazed joints, use silver-based filler alloys (e.g., BAg-7) compatible with austenitic stainless steel. For welded connections, employ inert gas shielding (argon or argon-helium mix) and post-weld solution annealing to restore corrosion resistance.
Storage: Store coils in a dry, well-ventilated warehouse away from direct sunlight and aggressive chemicals. Ensure wooden pallets are treated against moisture. Avoid stacking coils of different diameters to prevent surface marking.
Maintenance: For fan coil unit applications, periodic inspection of coil surfaces for fouling, scaling, or corrosion is recommended. Descaling with mild acid solutions (citric acid or phosphoric acid) is acceptable; avoid hydrochloric acid which may cause pitting in 304 grade. Flushing with deionized water and biocide treatment is advised for long-term operation in closed-loop systems.
9. Product Identification
- Product Catalog No.: 1162
- Product Category: Technical Literature & Learning Resources — Fan Coil Unit Fault Analysis and Troubleshooting
- Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
- Origin: Wenzhou, Zhejiang Province, People's Republic of China