Stainless Steel Coil Tube (Coiltube) — Technical Specification
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered seamless or welded tubular product supplied in continuous coil form, designed primarily for heat exchange, fluid conveying, and structural applications in HVAC (Heating, Ventilation, and Air Conditioning) systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this product is specifically optimized for use in Dry Coil Systems (DHC) and New Air Handling Units (NAHU), where the coil tube serves as the core heat transfer element. The coiled configuration enables efficient downstream forming into finned coils, compact heat exchangers, and air handling components with minimal material waste.
Dry Coil Systems represent an advanced ventilation approach in which a dehumidification coil operates at a low supply air temperature to remove latent heat (moisture) from incoming air, followed by a reheat section to restore the air to a comfortable temperature. The coil tube is the critical component in this process, and its material selection, dimensional accuracy, and surface integrity directly influence system efficiency, energy consumption, and operational reliability.
Material & Properties
The Coil Tube is fabricated from high-grade austenitic stainless steels, selected for their superior corrosion resistance, thermal conductivity, and mechanical strength across a wide range of operating conditions.
Available Material Grades
- 304 (UNS S30400 / 1.4301) — General-purpose grade with excellent corrosion resistance in most atmospheric and mild chemical environments; suitable for standard HVAC and dry coil applications.
- 316 (UNS S31600 / 1.4401) — Enhanced molybdenum content provides superior resistance to chlorides and marine atmospheres; recommended for coastal or high-moisture environments.
- 316L (UNS S31603 / 1.4404) — Low-carbon variant of 316 offering improved weldability and resistance to intergranular corrosion after welding operations.
- 321 (UNS S32100 / 1.4541) — Titanium-stabilized grade providing enhanced resistance to sensitization at elevated temperatures (up to 870°C).
Key Mechanical & Physical Properties (Typical for Grade 304)
| Property | Value | Standard Reference |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 MPa | ASTM A269 / GB/T 12771 |
| Yield Strength (屈服强度) | ≥ 205 MPa | ASTM A269 / GB/T 12771 |
| Elongation (延伸率) | ≥ 40% | ASTM A269 / GB/T 12771 |
| Thermal Conductivity (导热系数) | 16.3 W/(m·K) at 20°C | ASTM E1461 |
| Specific Heat (比热容) | 500 J/(kg·K) at 20°C | — |
| Density (密度) | 8.0 g/cm³ | — |
| Operating Temperature Range (工作温度范围) | -196°C to +870°C | — |
| Corrosion Resistance (耐腐蚀性) | Equivalent to 304 stainless steel in standard environments | ASTM G48 / GB/T 4334 |
Specifications
The following table outlines the standard dimensional and performance specifications for the Stainless Steel Coil Tube product line. Custom dimensions are available upon request through Wenzhou Jixing Metal Materials Co., Ltd.
| Specification Parameter | Standard Range / Value | Applicable Standard |
|---|---|---|
| Outer Diameter (OD) (外径) | Φ6.0 mm — Φ50.8 mm (¼" — 2") | ASTM A269 / GB/T 12771 |
| Wall Thickness (壁厚) | 0.30 mm — 3.00 mm | ASTM A269 / GB/T 12771 |
| OD Tolerance (外径公差) | ±0.05 mm (precision grade); ±0.10 mm (standard grade) | ASTM A269 |
| Wall Thickness Tolerance (壁厚公差) | ±10% of nominal (precision grade); ±12.5% (standard grade) | ASTM A269 |
| Coil Length (盘管长度) | 10 m — 100 m per coil (customizable) | — |
| Coil Winding Diameter (盘绕直径) | Φ150 mm — Φ400 mm (adjustable) | — |
| Surface Finish (表面光洁度) | Ba ≤ 0.4 μm (electropolished); Ra ≤ 0.8 μm (mechanically polished); No.4 brushed finish available | ASTM A269 / GB/T 12771 |
| End Condition (端部状态) | Open ends; deburred; optionally capped or sealed | — |
| Heat Treatment (热处理) | Solution annealed (固溶退火); pickled and passivated | ASTM A269 |
| Maximum Working Pressure (最大工作压力) | Up to 1.6 MPa (standard); up to 4.0 MPa (heavy-wall grade) | ASME B31.9 / GB/T 12771 |
| Hydrostatic Test Pressure (水压试验压力) | 1.5× Maximum Working Pressure | ASME B31.9 |
| Coating / Lining (涂层) | None (bare stainless); optional PTFE (聚四氟乙烯) internal coating for chemical service | — |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing process to ensure dimensional precision, metallurgical integrity, and surface quality:
- Raw Material Procurement (原材料采购) — Virgin stainless steel strip or coil sourced from certified mills, accompanied by mill test certificates (MTC) verifying chemical composition and mechanical properties in compliance with ASTM A269 or GB/T 12771.
- Slitting & Annealing (分条与退火) — Wide coils are slit to the required strip width. Stress-relief annealing is performed to ensure uniform material properties and eliminate residual stresses from prior forming operations.
- Tubular Forming (制管成型) — The strip is fed through a series of progressive roll-forming stations that incrementally shape the flat strip into a circular tube cross-section. This cold-forming process maintains the mechanical properties of the stainless steel without requiring subsequent heat treatment.
- Welding (焊接) — For welded coil tube, a high-frequency induction welding (高频感应焊) or automatic orbital TIG welding process is employed to form a seamless longitudinal seam. The weld bead is ground flush to ensure internal smoothness and eliminate turbulence-inducing protrusions.
- Precision Sizing (精整定径) — The formed tube passes through a series of sizing rolls to achieve the exact outer diameter and wall thickness within specified tolerances. This step is critical for ensuring proper fit in downstream heat exchanger assemblies.
- Coiling (盘绕) — The finished tube is wound onto a mandrel at a controlled winding diameter and tension to produce the coil form. The coiling tension is carefully calibrated to prevent ovalization or distortion of the tube cross-section.
- Surface Treatment (表面处理) — The coil tube undergoes pickling and passivation (酸洗钝化) to remove surface contaminants and restore the protective chromium oxide layer. Optional electropolishing (电解抛光) is available for applications requiring ultra-smooth internal surfaces (e.g., food-grade or pharmaceutical HVAC systems).
- Quality Inspection (质量检验) — Each coil is subjected to comprehensive inspection including visual examination, dimensional verification (caliper and micrometer measurements), hydrostatic pressure testing, and spectrometric chemical analysis. Eddy current testing (涡流检测) is available for non-destructive verification of weld integrity.
- Packaging & Shipping (包装与运输) — Coils are wrapped in moisture-resistant protective film, secured with steel strapping, and placed on wooden pallets or in custom export crates to prevent damage during transit.
Applications
The Stainless Steel Coil Tube is engineered for a diverse range of industrial and commercial applications, with particular emphasis on HVAC and thermal management systems:
Primary Applications
- Dry Coil Systems (干盘管系统) — The coil tube serves as the primary heat transfer element in dehumidification coils and reheat coils within dry coil ventilation systems. Its corrosion resistance and thermal efficiency make it ideal for the repeated condensation and re-evaporation cycles inherent in latent heat removal.
- New Air Handling Units (新风机组) — Used in the coil assemblies of NAHU systems, where precise temperature and humidity control is required for fresh air conditioning in commercial buildings, hospitals, and cleanrooms.
- Finned Heat Exchangers (翅片式换热器) — The coil tube is expanded, slotted, or crimped to accept aluminum or copper fins, creating high-efficiency air-to-fluid heat exchangers for chiller condensers, evaporators, and air cooler applications.
- Chilled Water Coils (冷冻水盘管) — Employed in air conditioning coils where chilled water circulates through the tube to cool incoming air streams.
- Reheat Coils (再热盘管) — Used in systems requiring post-dehumidification temperature recovery, particularly in variable air volume (VAV) systems.
Secondary Applications
- Food and beverage processing HVAC systems (食品及饮料加工暖通系统)
- Pharmaceutical and biotechnology cleanroom ventilation (制药及生物技术洁净室通风)
- Marine and offshore HVAC systems (海洋及海上暖通系统)
- Solar thermal collector absorber tubes (太阳能集热器吸热管)
- Chemical processing fluid transport lines (化工流体输送管路)
- Automotive and aerospace thermal management components (汽车及航空航天热管理部件)
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and complies with the following standards:
Certifications
- ISO 9001:2015 — Quality Management System (质量管理体系)
- ISO 14001:2015 — Environmental Management System (环境管理体系)
- ISO 45001:2018 — Occupational Health and Safety Management System (职业健康安全管理体系)
- CE Marking — Conformity with European Union directives for product safety and performance
- SGS Testing — Independent third-party material and dimensional verification
- TÜV Certification — German technical inspection body certification for manufacturing processes
Applicable Standards
| Standard | Description |
|---|---|
| ASTM A269 / A269M | Standard Specification for Seamless and Wrought Stainless Steel Tube, Pipe, and Fittings for Chemical and Allied Uses |
| GB/T 12771 | Chinese National Standard for Stainless Steel Seamless Tubes for Fluid Transport |
| ASTM A312 / A312M | Standard Specification for Austenitic Stainless Steel Seamless Tubing for Chemical and Allied Uses |
| EN 10217-7 | European Standard for Heat Exchanger Tubes — Austenitic Stainless Steel Tubes |
| ASME B31.9 | Pressure Piping — Refrigeration Piping and Heat Transfer Components |
| GB/T 14976 | Chinese National Standard for Seamless Stainless Steel Tubes for Fluid Transport |
| ASTM G48 | Standard Guide for Conducting Pitting and Crevice Corrosion Resistance Testing with Ferric Chloride Solution |
| GB/T 4334 | Chinese National Standard for Electrochemical Testing Methods for Stainless Steel Corrosion Resistance |
Quality Assurance Measures
- Mill Test Certificates (MTC) — Provided for every batch, certifying chemical composition (via optical emission spectrometry, OES) and mechanical properties.
- Third-Party Inspection (第三方检验) — Optional pre-shipment inspection by SGS, Bureau Veritas, or TÜV upon customer request.
- Traceability System (可追溯系统) — Each coil is marked with a unique batch number linking to the full production record, including raw material origin, heat treatment parameters, and inspection results.
- Hydrostatic Testing (水压试验) — 100% of coils undergo hydrostatic pressure testing at 1.5× the maximum working pressure to verify weld integrity and dimensional conformance.
- Non-Destructive Testing (NDT, 无损检测) — Eddy current testing (ECT) and ultrasonic testing (UT) available for weld seam verification on welded coil tube products.
Unique Selling Points
1. Dry Coil System Optimization: The Coil Tube is specifically engineered for the demanding thermal cycling conditions of Dry Coil Systems, where the tube must withstand repeated condensation and re-evaporation without degradation. The precision wall thickness and uniform bore diameter ensure consistent heat transfer coefficients across the entire coil length, directly contributing to improved system COP (Coefficient of Performance) and energy efficiency.
2. Precision Dimensional Control: With outer diameter tolerances as tight as ±0.05 mm, the Coil Tube ensures seamless integration with precision-machined heat exchanger headers, fin tubes, and air handling unit casings, minimizing assembly time and reducing the risk of leakage.
3. Enhanced Surface Integrity: The pickling