Stainless Steel Coil Tube — Low-Temperature Hot Water Radiant Heating Bed System
Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubular product designed specifically for low-temperature hot water radiant heating bed systems. This product integrates seamless or welded stainless steel tubing coiled into a continuous, compact configuration that maximizes surface-area-to-volume ratio for efficient thermal transfer. The coil tube serves as the primary heat exchange element within radiant heating applications, where low-pressure hot water circulates through the coiled channels to deliver uniform, gentle thermal energy to the surrounding environment or substrate.
Based on extensive research into the heat dissipation characteristics of low-temperature hot water coil tube heating bed systems, this product has been optimized for thermal conductivity, pressure resistance, and long-term durability under cyclic thermal loading conditions. The design philosophy emphasizes energy efficiency, corrosion resistance, and structural integrity over extended service life.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, typically conforming to the following material grades:
- SUS304 / AISI 304 (UNS S30408): The primary material grade, offering excellent general corrosion resistance, formability, and weldability. Contains 18% Chromium (Cr) and 8% Nickel (Ni) by mass, providing a stable passive oxide layer under most environmental conditions.
- SUS316L / AISI 316L (UNS S31603): An enhanced grade incorporating 2–3% Molybdenum (Mo), recommended for applications involving chlorinated water or aggressive chemical environments. The "L" designation indicates low carbon content (≤0.03%), minimizing intergranular corrosion risk during welding.
- SUS321 / AISI 321 (UNS S32100): Titanium-stabilized grade suitable for higher-temperature applications up to 870°C, with superior resistance to sensitization during thermal cycling.
Key Mechanical and Thermal Properties
| Property | Specification (SUS304) | Specification (SUS316L) |
|---|---|---|
| Tensile Strength (UTS) | ≥ 520 MPa | ≥ 515 MPa |
| Yield Strength (0.2% Offset) | ≥ 205 MPa | ≥ 170 MPa |
| Elongation at Fracture | ≥ 40% | ≥ 40% |
| Thermal Conductivity (at 25°C) | 16.3 W/(m·K) | 14.6 W/(m·K) |
| Thermal Expansion Coefficient (20–100°C) | 17.3 × 10⁻⁶ /°C | 17.1 × 10⁻⁶ /°C |
| Maximum Operating Temperature | 870°C (oxidizing atmosphere) | 870°C (oxidizing atmosphere) |
| Maximum Operating Pressure (typical) | 1.0 – 1.6 MPa (gauge) | 1.0 – 1.6 MPa (gauge) |
| Surface Roughness (Ra) | ≤ 0.8 μm (polished finish) | ≤ 0.8 μm (polished finish) |
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Product Serial No. | 666 |
| Outer Diameter (OD) | Φ6 mm – Φ32 mm (customizable) |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Diameter (Coiling Diameter) | Φ200 mm – Φ1,200 mm |
| Tube Length per Coil | 5 m – 100 m (continuous) |
| Coil Pitch (Spacing between Turns) | 5 mm – 25 mm (configurable) |
| Material Grade | SUS304, SUS316L, SUS321, SUS310S |
| Surface Finish | Pickled & Passivated (2B), Mirror Polished (8K), Satin (HL) |
| Connection Type | Flared End, Threaded (BSP/NPT), Flanged, or Butt Weld |
| Operating Water Temperature | 35°C – 65°C (low-temperature radiant heating) |
| Operating Pressure | 0.2 MPa – 1.6 MPa (gauge) |
| Hydrostatic Test Pressure | 1.5 × Working Pressure (minimum 2.4 MPa) |
| Applicable Standards | GB/T 12771, GB/T 21832, ASTM A269/A270, EN 10217, JIS G3459 |
Manufacturing Process
The production of stainless steel coil tubes for radiant heating applications follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: Cold-rolled stainless steel strip or seamless tube blanks are sourced from certified mills with full chemical composition traceability. Incoming materials undergo spectrometric verification (OES — Optical Emission Spectroscopy) to confirm grade compliance.
- Tubing Formation: For welded tubes, precision cold-rolled strip is fed through a roll-forming die set to create a helical tube blank, which is then longitudinally welded using Tungsten Inert Gas (TIG) or Automatic Pulse Arc welding. For seamless tubes, hot-rolled billets are pierced and cold-drawn to final dimensions.
- Heat Treatment: Welded tubes undergo Solution Annealing at 1050°C – 1100°C followed by rapid quenching (air or water) to restore full austenitic structure, eliminate residual welding stresses, and ensure uniform corrosion resistance. The weld zone is subsequently pickled and passivated to restore the chromium oxide passive layer.
- Cold Drawing / Sizing: Tubes are cold-drawn through precision tungsten carbide dies to achieve exact outer diameter and wall thickness tolerances (±0.05 mm). This step also enhances mechanical properties through strain hardening.
- Coiling Operation: The finished tube is coiled at controlled tension and bending radius using a CNC (Computer Numerical Control) coil-winding machine. The coil pitch, diameter, and total length are programmed to meet the specific system design requirements. Minimum bend radius is maintained at ≥ 5× tube OD to prevent ovality or wall thinning.
- Surface Treatment: Depending on the application, tubes receive pickling (removal of surface scale), passivation (chemical activation of Cr₂O₃ layer using citric or nitric acid), or mechanical polishing to achieve mirror or satin finish.
- End Processing: Tube ends are machined to accept flaring, threading, or welding connections. Precision cutting ensures square, burr-free ends suitable for seamless integration into heating manifolds.
- Quality Inspection: Each batch undergoes 100% hydrostatic pressure testing, eddy current (ECT) flaw detection for weld integrity, and dimensional verification via coordinate measuring machine (CMM) or laser scanning.
Applications
The stainless steel coil tube for low-temperature hot water radiant heating bed systems finds application across multiple industries:
- Medical & Healthcare: Radiant heating beds in hospitals for post-operative patient warmth, neonatal incubators, and physiotherapy equipment. The corrosion-resistant and hygienic surface finish meets medical-grade requirements.
- Agricultural & Livestock: Heated bedding systems for livestock (pigs, poultry, cattle) to maintain optimal ambient temperature during cold seasons. The low-temperature operation (35°C–65°C) prevents thermal injury to animals while reducing energy consumption compared to high-temperature systems.
- Greenhouse & Horticulture: Substrate heating for seed germination trays, root zone heating for hydroponic systems, and floor heating in controlled-environment agriculture.
- Industrial Process Heating: Temperature-controlled surfaces in food processing (conveyor belts, packaging lines), pharmaceutical drying, and material curing applications.
- Domestic & Commercial: Floor radiant heating systems, heated furniture (mats, chairs), and thermal management in automotive seating systems.
- Cryogenic & Low-Temperature Storage: Insulated container heating elements to maintain product temperature during cold-chain logistics.
Unique Selling Points
- Superior Corrosion Resistance: The austenitic stainless steel composition provides exceptional resistance to corrosion in water-based heating circuits, eliminating the need for chemical inhibitors and extending system lifespan beyond 20 years.
- Optimized Heat Dissipation: Research-backed coil geometry maximizes convective and radiative heat transfer while minimizing pressure drop, achieving thermal efficiency rates exceeding 92% in low-temperature operation.
- Low-Temperature Operation Advantage: Designed specifically for 35°C–65°C water temperatures, reducing energy consumption by 30–50% compared to conventional high-temperature heating systems while maintaining comfortable radiant warmth.
- Hygienic Surface Finish: Mirror-polished (Ra ≤ 0.4 μm) options meet food-grade (FDA-compliant) and medical-grade surface requirements, facilitating easy cleaning and preventing bacterial colonization.
- Customizable Geometry: Full CNC programming capability allows tailored coil diameters, pitches, and lengths to fit specific system designs and spatial constraints.
- Structural Integrity: Precision manufacturing with full traceability ensures consistent wall thickness, ovality ≤ 1%, and zero defects in the weld zone, guaranteeing leak-free operation under cyclic pressure loading.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework supported by the following certifications and standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- CE Marking (EU Conformity) — Compliance with European pressure equipment directives (PED 2014/68/EU) for products operating above specified pressure thresholds.
- GB/T 19001-2016 — Chinese national standard for quality management systems.
- SGS Testing — Independent third-party verification of material composition, mechanical properties, and surface quality.
- Material Test Certificates (MTC) — EN 10204 Type 3.1 certificates provided with each shipment, including full chemical analysis, mechanical test results, and heat treatment documentation.
- NACE MR0175 / ISO 15156 — Compliance for sour service applications where hydrogen-induced cracking resistance is required.
- NSF/ANSI 61 — Drinking water system component certification (available for medical and food-grade applications).
Note: All products are manufactured in accordance with applicable national and international standards. Custom specifications are available upon request. Wenzhou Jixing Metal Materials Co., Ltd. provides full technical documentation, including heat dissipation performance data sheets derived from experimental studies on low-temperature hot water coil tube heating bed systems, to support system design and validation.