Stainless Steel Coil Tube for Horizontal Floating Coil Heat Exchangers
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous helical tube designed specifically for integration into horizontal floating coil heat exchangers within district heating systems, building HVAC (Heating, Ventilation, and Air Conditioning) applications, and industrial thermal management processes. The coil tube serves as the primary heat transfer element, facilitating efficient thermal exchange between a circulating heating medium (typically hot water or steam) and the ambient air or secondary fluid stream.
Unlike conventional straight-tube heat exchangers, the floating coil configuration allows the stainless steel coil tube to expand and contract freely within the heat exchanger shell, accommodating thermal cycling without inducing mechanical stress, thereby significantly extending service life in demanding heating system environments.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel, offering superior corrosion resistance, thermal conductivity, and mechanical integrity across a wide temperature range.
- Base Material: Austenitic stainless steel conforming to ASTM A213 / ASME SA-213 specifications
- Common Grades:
- 304 (UNS S30400): General-purpose corrosion resistance; ideal for potable water and standard heating circuits
- 316 (UNS S31600): Enhanced chloride and acid resistance; suitable for aggressive or marine-adjacent environments
- 316L (UNS S31603): Low-carbon variant for improved weldability and resistance to sensitization
- 321 (UNS S32100): Titanium-stabilized grade for elevated-temperature service above 425°C (800°F)
- Surface Finish: Mill finish or electropolished (Ra ≤ 0.4 μm) for reduced fouling and enhanced heat transfer coefficients
- Temperature Range: Continuous service from −196°C to +870°C (depending on grade)
- Pressure Rating: Up to 1.6 MPa (PN16) for standard coil configurations; custom ratings available upon request
Specifications
| Parameter | Specification |
|---|---|
| Tube Outer Diameter (OD) | Φ6 mm – Φ22 mm (standard range) |
| Tube Wall Thickness | 0.5 mm – 1.5 mm |
| Coil Diameter (CD) | Φ50 mm – Φ150 mm |
| Coil Length (Uncoiled) | 5 m – 60 m (configurable) |
| Tightness / Pitch | 1.5×OD to 3×OD (adjustable for flow rate optimization) |
| End Preparation | Plain end, flared end, or threaded connection |
| Surface Treatment | Pickled and passivated (PP finish); optional electropolish |
| Heat Transfer Efficiency | U-value: 180 – 350 W/(m²·K) (air-side dependent) |
| Operating Pressure | PN10 / PN16 (standard); PN25 available on request |
| Design Standards | GB/T 14976, ASTM A213, ASME SA-213, EN 10216-5 |
| Inspection Method | 100% ultrasonic testing (UT); hydrostatic pressure test |
Manufacturing Process
The production of high-quality stainless steel coil tubes for floating coil heat exchanger applications follows a rigorous multi-stage process:
- Raw Material Selection: Annealed stainless steel wire or seamless tube stock is procured from certified mills with full mill test certificates (MTC) verifying chemical composition and mechanical properties.
- Coil Forming (Cold Bending): The straight tube is mechanically coiled using precision CNC-controlled coil forming equipment. The bending process is executed at controlled speeds to prevent work hardening, ovality, or wall thinning. Minimum bend radius is maintained at ≥ 3×OD to ensure structural integrity.
- End Forming: Tube ends are prepared through flare forming, threading, or butt-welding of connection fittings, depending on the intended heat exchanger assembly method.
- Surface Cleaning: The formed coil undergoes pickling and passivation (PP treatment) to remove oxide scale, embedded iron particles, and surface contaminants, restoring the passive chromium oxide layer essential for corrosion resistance.
- Quality Inspection:
- 100% ultrasonic wall thickness testing to verify uniformity
- Hydrostatic pressure testing at 1.5× working pressure for a minimum of 30 seconds
- Dimensional verification (OD, wall thickness, coil diameter, pitch) using calibrated gauges
- Visual inspection for surface defects, kinks, or deformation
- Packaging: Each coil is individually wrapped in protective film, placed in a wooden crate or steel frame, and labeled with a unique batch traceability tag for full supply chain accountability.
Applications
The stainless steel coil tube is integral to a broad spectrum of thermal engineering applications:
- Horizontal Floating Coil Heat Exchangers: Primary application — the coil tube acts as the core heat transfer element within sealed vessel-type heat exchangers used in district heating networks, providing space heating, domestic hot water (DHW) generation, and underfloor radiant heating.
- Building HVAC Systems: Integration into air-handling units (AHUs), fan coil units (FCUs), and chiller coils for commercial and residential climate control.
- Industrial Process Heating: Utilization in chemical processing, food and beverage pasteurization, pharmaceutical manufacturing, and textile dyeing systems where sanitary-grade stainless steel is mandated.
- Marine and Offshore Platforms: Deployment in shipboard heating systems and offshore facility thermal loops, leveraging the superior chloride resistance of 316/316L grades.
- Geothermal Energy Systems: Application in closed-loop geothermal heat exchangers where long-term thermal cycling and ground-contact corrosion resistance are critical.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring compliance with international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- CE Marking — Conformity with European Union directives for pressure equipment (PED 2014/68/EU)
- EN 10204 3.1 — Manufacturer's test report for material traceability
- NB Certification — National Supervision Administration of China for pressure vessel components
- Material Certification: Each batch accompanied by EN 10204 3.1 MTC with full chemical analysis (C, Si, Mn, P, S, Cr, Ni, Mo) and mechanical test results (tensile strength, yield strength, elongation, hardness)
Unique Selling Points
1. Floating Design Compatibility: The coil tube is engineered with precise dimensional tolerances to enable true "floating" installation within heat exchanger shells, eliminating thermal stress and enabling maintenance-free operation for extended service intervals exceeding 20 years.
2. Custom Configurability: Full customization of coil diameter, pitch, tube length, and end preparation allows seamless integration with existing heat exchanger designs from any OEM, reducing retrofit costs and commissioning time.
3. Superior Corrosion Resistance: The austenitic stainless steel construction provides inherent resistance to scaling, pitting, and intergranular corrosion, ensuring consistent heat transfer performance throughout the design life without degradation.
4. End-to-End Traceability: Every coil tube carries a unique identification code linked to its raw material batch, manufacturing parameters, and inspection records, enabling full supply chain traceability for critical infrastructure applications.