Stainless Steel Coil Tube — Steam Drying Heat Exchange Application

Product Overview

The Stainless Steel Coil Tube (Model Ref.: JX-CoilTube-528) is a precision-engineered continuous spiral tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for steam drying heat exchange systems. This product is supplied in coiled configuration, enabling seamless integration into axial and radial positioning assemblies within industrial drying apparatus. The coil tube delivers superior thermal conductivity, mechanical resilience under cyclic thermal loading, and long-term corrosion resistance in high-temperature steam environments.

Unlike conventional straight-pipe heat exchangers, the coiltube geometry maximizes heat transfer surface area per unit volume, reduces pressure drop, and facilitates compact installation within constrained equipment housings. The product has been validated through the engineering modification program titled "Modification of Axial and Radial Positioning Device for Steam Drying Heat Exchange Coil Tube", which addressed alignment tolerances, vibration damping, and thermal expansion compensation in operational systems.

Material & Properties

The coil tube is fabricated from austenitic stainless steel grades conforming to international standards, with the following material characteristics:

• Base Alloy: SUS304 / SUS316L / SUS321 (ASTM A213 TP304/TP316L/TP321 equivalent)
• Chromium Content: 18–25% (provides passive oxide film stability)
• Nickel Content: 8–22% (ensures austenitic structure retention at elevated temperatures)
• Molybdenum (316L grade): 2.0–3.0% (enhanced pitting and crevice corrosion resistance)
• Maximum Service Temperature: 870°C (SUS304) / 925°C (SUS321)
• Operating Pressure Rating: Up to 1.6 MPa (standard) / 2.5 MPa (reinforced)
• Surface Finish: 2B finish (Ra ≤ 0.8 μm) or pickled & passivated (Ra ≤ 1.2 μm)

Specifications

Parameter	Specification	Standard Reference
Outer Diameter (OD)	Φ6 mm – Φ32 mm	GB/T 14976 / ASTM A269
Wall Thickness	0.5 mm – 2.0 mm	GB/T 14976 / ASTM A269
Coil Pitch (Helix Spacing)	15 mm – 60 mm (configurable)	Custom per drawing
Coil Mean Diameter	Φ100 mm – Φ800 mm	Custom per drawing
Coil Length per Roll	5 m – 50 m	—
Dimensional Tolerance	±0.1 mm (OD); ±0.05 mm (wall thickness)	ISO 4287
End Condition	Plain / Beveled / Flanged / Threaded (G1/4 – G1)	GB/T 7306 / ASME B1.20.1
Surface Treatment	Pickled & Passivated / Electro-polished	ASTM A967
Winding Direction	Right-hand (standard) / Left-hand (optional)	—
Delivery Form	Coiled (on mandrel) or straightened sections	—

Manufacturing Process

The production of the JX-CoilTube-528 follows a rigorous multi-stage manufacturing sequence:

1. Raw Material Procurement: Cold-rolled stainless steel strip or seamless tube stock sourced from certified mills (Baosteel, Outokumpu, or equivalent), with mill test certificates (MTC) verified for chemical composition and mechanical properties.
2. Coil Forming (Cold Bending): The seamless tube is cold-formed into a helical coil using a CNC-controlled pipe coiling machine. The forming process maintains uniform curvature radius without inducing residual stress concentrations or wall-thickness reduction exceeding 5%.
3. Heat Treatment: Solution annealing at 1050–1100°C followed by water quenching to restore full austenitic structure and eliminate work-hardening effects from coiling. For SUS321 grade, stabilization annealing at 870–880°C is applied.
4. Pickling & Passivation: Immersion in nitric-fluoric acid solution removes oxide scale; subsequent passivation with dilute nitric acid (20–30%) forms a stable chromium oxide protective layer (Cr₂O₃).
5. Axial & Radial Positioning Assembly: The coil tube is integrated into a dedicated positioning bracket system that constrains both axial displacement (end-of-tube movement) and radial displacement (lateral deflection), ensuring stable operation under steam flow-induced vibration and thermal expansion. This positioning device modification incorporates elastomeric damping elements and adjustable set screws for field calibration.
6. Pressure Testing: Each coil assembly undergoes hydrostatic pressure testing at 1.5× working pressure (typically 2.4 MPa for standard configurations) with a minimum hold time of 30 minutes, verified by calibrated pressure gauges.
7. Non-Destructive Testing (NDT): 100% visual inspection, with random ultrasonic testing (UT) or eddy current testing (ECT) for internal defect detection per ASTM E709.

Applications

The JX-CoilTube-528 is engineered for demanding thermal processing applications, including:

• Industrial Steam Drying Systems: Primary heat transfer element in continuous belt dryers, rotary dryers, and fluidized bed dryers for food, pharmaceutical, and chemical powder processing.
• Pharmaceutical Sterilization Equipment: Steam jacketed reactors and autoclaves requiring sanitary-grade heat exchange surfaces (electropolished finish, Ra ≤ 0.4 μm).
• Food Processing Heat Exchangers: Pasteurization, UHT (Ultra-High Temperature) treatment systems, and condensate recovery units.
• Chemical Reactor Cooling/Heating Coils: Internal coil assemblies in agitated vessels for controlled exothermic/endothermic reactions.
• Heat Pump & Refrigeration Systems: Evaporator and condenser coil elements in industrial refrigeration circuits.
• Textile & Paper Drying Machinery: Steam-heated coil elements in cylinder dryers and Yankee dryers.

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification systems:

• ISO 9001:2015 — Quality Management System certification
• ISO 14001:2015 — Environmental Management System certification
• ASME Section IX — Welding procedure qualification (for brazed/welded coil assemblies)
• EN 10204 3.1 — Material test certificates (independent third-party inspection available)
• CE Marking — Conformity with EU Pressure Equipment Directive (PED 2014/68/EU) for pressure-bearing configurations
• NSF/ANSI 61 — Drinking water system components certification (for food/pharma grade applications)
• GB/T 14976-2012 — Chinese national standard for seamless stainless steel tubes for heat exchangers
• ASTM A269 / A213 — American standards for seamless austenitic stainless steel tubes

Unique Selling Points

Engineered for Precision Positioning: The axial and radial positioning device modification program has been integrated into the coil tube supply package, delivering a turnkey solution that eliminates field alignment issues and reduces commissioning time by up to 40%.

• Customizable Geometry: Coil pitch, mean diameter, and helix direction are fully configurable to match specific equipment layouts and thermal load requirements.
• Thermal Fatigue Resistance: Material selection and heat treatment protocols ensure ≥ 50,000 thermal cycle endurance without crack initiation at typical operating temperature differentials (ΔT = 100–300°C).
• Compact Volumetric Efficiency: Spiral geometry achieves 2.5–4× the heat transfer area of equivalent-length straight pipe within the same envelope space.
• Low Pressure Drop Design: Continuous helical flow path minimizes turbulent losses compared to finned-tube or plate heat exchanger alternatives.
• Full Traceability: Each coil tube batch is traceable from raw material heat number through final inspection, with digital quality records retained for 10 years.

Ordering Information & Technical Support

Customers are advised to provide the following parameters for accurate quotation and design matching:

• Required tube OD, wall thickness, and material grade
• Target coil pitch, mean diameter, and total developed length
• Operating temperature, pressure, and medium (steam, condensate, etc.)
• End connection type and orientation requirements
• Surface finish specification (2B, electropolished, sanitary)
• Applicable code/standard requirements for the installation jurisdiction

Wenzhou Jixing Metal Materials Co., Ltd. provides engineering consultation, sample prototyping, and on-site technical support for coil tube integration into steam drying and heat exchange systems worldwide.