Stainless Steel Coil Tube (Coiltube) for Ice Storage Tank Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed for use in pre-fabricated ice storage tank systems. These coil tubes are formed into helical or serpentine configurations to maximize heat exchange surface area within a compact volume, serving as the core thermal transfer element in ice storage (Thermal Energy Storage, TES) applications. The product leverages the superior corrosion resistance, hygienic properties, and mechanical durability of austenitic stainless steel to deliver long-term reliability in demanding refrigeration and HVAC environments.
Material & Properties
- Material Grade: Primarily SUS304 (UNS S30400) and SUS316L (UNS S31603) austenitic stainless steels, selected for their exceptional resistance to chloride-induced pitting and general corrosion in aqueous glycol and brine environments.
- Corrosion Resistance: The high chromium (Cr ≥ 18%) and nickel (Ni ≥ 8%) composition provides a stable passive oxide layer, ensuring resistance against deicing salts, calcium chloride brines, and ethylene glycol solutions commonly used in ice storage systems.
- Mechanical Properties: Tensile strength of ≥ 515 MPa (SUS304) and ≥ 515 MPa (SUS316L); elongation ≥ 40%, providing excellent formability during coiling operations without risk of cracking or fracture.
- Thermal Conductivity: Approximately 16.3 W/(m·K) for SUS304, offering a favorable balance between thermal transfer efficiency and structural integrity under cryogenic cycling conditions (−25°C to +5°C).
- Surface Finish: 2B (cold-rolled and annealed) or electropolished finish with surface roughness Ra ≤ 0.8 μm, minimizing fluid resistance and preventing ice adhesion.
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Material | SUS304 / SUS316L / SUS321 (optional) |
| Outer Diameter (OD) | φ8 mm – φ25 mm (customizable) |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Diameter | φ100 mm – φ600 mm (helical pitch 15–40 mm) |
| Coil Length (per spool) | 3 m – 15 m (configurable to tank geometry) |
| Operating Temperature | −25°C to +60°C (continuous cycling) |
| Working Pressure | ≤ 1.6 MPa (PN16) |
| Heat Transfer Medium | Cold water, calcium chloride brine, ethylene glycol solution |
| Ice Storage Rate | 0.8 – 1.5 kWh/L (system-dependent) |
| Design Life | ≥ 25 years under normal operating conditions |
| Standards Compliance | GB/T 14976, ASTM A213/A269, EN 10217-7 |
Manufacturing Process
- Raw Material Selection: Certified stainless steel seamless or welded tube blanks are procured in compliance with GB/T 14976 or ASTM A213 specifications. Incoming material undergoes spectrographic analysis (PMI — Positive Material Identification) to verify alloy composition.
- Precision Cutting: Tube blanks are cut to specified lengths using automated plasma or laser cutting systems, with end-face squareness tolerance of ±0.5°.
- End Preparation: Tube ends are deburred, chamfered, and (where required) expanded or threaded to facilitate brazing or mechanical connection to manifold headers.
- Coiling Forming: A programmable coiling machine (CNC-guided) winds the straight tube into the required helical or serpentine geometry. The forming process is performed at ambient temperature to avoid work-hardening beyond acceptable limits. Tension and bending radius are precisely controlled to prevent ovality exceeding 2% and to avoid micro-cracking on the outer bend surface.
- Welding & Brazing: Inlet and outlet connections are brazed (using silver-based filler alloy, e.g., Ag-Cu eutectic) or TIG-welded (GTAW — Gas Tungsten Arc Welding) to stainless steel headers. All welds undergo 100% visual inspection; critical joints are subject to helium leak testing at a sensitivity of 1×10⁻⁹ Pa·m³/s.
- Hydrostatic Pressure Testing: Each coil assembly is pressure-tested at 1.5× the maximum working pressure for a minimum of 30 minutes to verify structural integrity and weld soundness.
- Passivation & Cleaning: All exposed surfaces are acid-pickled and passivated (nitric acid/hydrofluoric acid treatment) to restore the chromium oxide passive film after fabrication. The interior is flushed with deionized water to a conductivity of ≤ 5 μS/cm.
- Final Inspection & Packaging: Dimensional verification (OD, wall thickness, coil diameter, pitch), surface quality assessment, and material traceability documentation are completed prior to protective packaging for shipment.
Applications
- Ice Storage HVAC Systems: Primary application in pre-fabricated ice storage tanks (蓄冰槽) for peak-shaving and load-shifting in commercial and industrial HVAC systems. The coil tube configuration enables efficient heat extraction from the storage medium, forming a layer of ice around the tube surface.
- Commercial Refrigeration: Used in blast freezers, refrigerated warehouses, and cold chain logistics facilities where rapid ice formation and reliable thermal buffering are required.
- Process Cooling: Applied in pharmaceutical, food processing, and chemical manufacturing facilities requiring precise temperature control and hygienic-grade piping.
- Geothermal & District Cooling: Deployed in ground-source heat exchange systems and district cooling networks where long-term corrosion resistance and thermal cycling durability are critical.
Quality Certifications & Standards Compliance
- ISO 9001:2015 — Quality Management System certification covering the entire manufacturing and quality assurance process.
- ISO 14001:2015 — Environmental Management System, demonstrating commitment to sustainable manufacturing practices.
- NADCAP / AS9100 (where applicable for aerospace-adjacent applications) — Ensuring process control and traceability for critical manufacturing steps.
- Material Certifications: Each batch is accompanied by an EN 10204 3.1 Certificate of Conformity, including full chemical analysis, mechanical test data, and heat number traceability.
- Pressure Vessel Compliance: Fabrication processes align with ASME Section VIII Div. 1 and GB/T 150 (Chinese Pressure Vessel Code) requirements for components used in pressure-retaining systems.
- Hygienic Certification: For food-grade and pharmaceutical applications, surface finish and welding practices comply with 3-A Sanitary Standards and EHEDG (European Hygienic Engineering Design Group) guidelines.
Unique Selling Points
The Coiltube product line from Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through the following key advantages:
- Optimized Heat Transfer Geometry: The precisely controlled helical coil configuration maximizes the surface-area-to-volume ratio, achieving ice formation rates up to 1.5 kWh/L — significantly outperforming conventional plate or finned-tube alternatives in compact installations.
- Superior Cryogenic Durability: Austenitic stainless steel retains full ductility at sub-zero temperatures, eliminating the risk of brittle fracture during repeated freeze-thaw cycling over a 25+ year design life.
- Integrated Prefabrication: The coil assemblies are pre-manufactured and pressure-tested at the factory, reducing on-site installation time by up to 60% compared to field-fabricated alternatives and ensuring consistent quality.
- Full Traceability: Every coil tube assembly is traceable to the original steel heat number through a digital quality record system, supporting compliance audits and lifecycle maintenance planning.
- Customizability: Coil diameter, pitch, tube dimensions, and connection configurations are tailored to specific tank geometry and thermal load requirements, enabling optimal system integration.