Stainless Steel Coil Tube (Coiltube) – Industrial Heat Exchange Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product supplied in continuous coiled form, designed primarily for heat exchange, steam heating, and thermal transfer applications. Coil tubes offer significant advantages over straight lengths in terms of space efficiency, thermal performance, and ease of installation within compact heat exchanger assemblies, condensers, and reboilers.
This product is engineered to withstand high-temperature steam environments, aggressive chemical media, and cyclic thermal loading while maintaining structural integrity and dimensional accuracy throughout its service life. The coiled configuration facilitates seamless integration into shell-and-tube heat exchangers, air preheaters, and process heating systems.
Material & Properties
Material Grades
- AISI 304 / UNS S30408 – General-purpose austenitic stainless steel with excellent corrosion resistance and formability; ideal for steam heating and moderate-temperature applications.
- AISI 316 / UNS S31608 – Molybdenum-enhanced austenitic grade offering superior resistance to pitting and crevice corrosion in chlorinated or acidic environments.
- AISI 316L / UNS S31603 – Low-carbon variant of 316, suitable for high-temperature service where sensitization (intergranular corrosion) must be avoided.
- AISI 321 / UNS S32108 – Titanium-stabilized grade providing enhanced resistance to intergranular corrosion at elevated temperatures (up to 870°C).
- AISI 310S / UNS S31008 – High-temperature austenitic grade for extreme thermal cycling environments exceeding 1000°C.
Mechanical Properties (AISI 304, Annealed Condition)
- Tensile Strength (UTS): ≥ 515 MPa (74,700 psi)
- Yield Strength (0.2% Offset): ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40%
- Hardness: ≤ 217 HB (Brinell)
- Maximum Service Temperature: 870°C (1,598°F)
- Minimum Service Temperature: -196°C (cryogenic capable)
Chemical Composition (AISI 304, wt%)
| Element | Specification | Element | Specification |
|---|---|---|---|
| C (Carbon) | ≤ 0.08 | Ni (Nickel) | 8.0 – 10.5 |
| Si (Silicon) | ≤ 0.75 | Mn (Manganese) | ≤ 2.00 |
| P (Phosphorus) | ≤ 0.045 | S (Sulfur) | ≤ 0.030 |
| S (Sulfur) | ≤ 0.030 | N (Nitrogen) | ≤ 0.10 |
| Cr (Chromium) | 18.0 – 20.0 | Fe (Iron) | Balance |
Corrosion Resistance
- Excellent resistance to atmospheric corrosion and non-oxidizing acids
- Good resistance to dilute organic and inorganic acids
- Superior resistance to boiling acetic acid (up to 20%) and citric acid (up to 10%)
- Effective resistance to steam and condensate environments at temperatures up to 350°C
- 316 grade: additional resistance to marine atmospheres, sulfuric acid, and phosphoric acid
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ50.8 mm (¼" – 2") | ASTM A213 / ASME SA-213 |
| Wall Thickness | 0.5 mm – 3.0 mm (0.020" – 0.118") | ASTM A213 / ASME SA-213 | OD Tolerance | ±0.05 mm (±0.002") | EN 10216-5 / GB/T 14976 |
| Wall Thickness Tolerance | ±10% of nominal | ASTM A213 |
| Coil Length | Custom – typically 50 m – 500 m per coil | Manufacturer specification |
| Coil Inner Diameter | Φ200 mm – Φ600 mm (as required) | Manufacturer specification |
| Surface Finish | Pickled & Passivated (2B), No. 4 Brushed, or Mirror (BA) | ASTM A403 |
| End Condition | Plain, Beveled, or Threaded (as specified) | ASME B1.20.1 |
| Heat Treatment | Solution Annealed (1050°C – 1150°C, water quench) | ASTM A213 |
| Maximum Operating Pressure | Up to 4.0 MPa (580 psi) – depends on OD, wall, and temperature | ASME BPV Code Section I |
| Maximum Operating Temperature | 304: 870°C | 316: 870°C | 310S: 1100°C | Material-dependent |
| Thermal Conductivity | 16.3 W/(m·K) at 100°C (AISI 304) | ASM Handbook |
| Applicable Standards | ASTM A213, ASME SA-213, EN 10216-5, GB/T 14976, JIS G3459 | — |
Manufacturing Process
1. Raw Material Preparation
High-purity austenitic stainless steel billets or wire rod are sourced from certified mills. Incoming material undergoes strict chemical analysis (via optical emission spectrometry, OES) and mechanical testing to ensure compliance with the specified grade requirements. Certificates of Analysis (CoA) are maintained for full traceability.
2. Pipe Forming (Seamless or Welded)
- Seamless Process: Billets are heated to 1,100°C – 1,200°C, pierced on a Mannesmann-type piercing mill, and hot-rolled to near-final dimensions. This produces a homogeneous microstructure without weld seams.
- Welded Process: Cold-rolled stainless steel strip is formed into a tubular shape and welded using Automatic Submerged Arc Welding (SAW) or High-Frequency Induction Welding (HFW). Welds are subsequently homogenized through solution annealing.
3. Cold Drawing / Sizing
The formed tubes are cold-drawn through precision dies to achieve exact dimensional tolerances (OD ±0.05 mm). This process enhances mechanical properties through work hardening and ensures uniform wall thickness throughout the tube length.
4. Solution Annealing
Tubes are heated to 1,050°C – 1,150°C in a controlled atmosphere furnace (nitrogen or vacuum) and rapidly cooled (water quench or air cool). This dissolves carbides, eliminates residual stresses from cold working, and restores full corrosion resistance and ductility.
5. Pickling and Passivation
Following annealing, tubes are immersed in a mixed acid bath (typically HNO₃/HF or H₂SO₄/HNO₃) to remove oxide scale. Subsequent passivation with dilute nitric acid (20%–30%) forms a protective chromium oxide film, ensuring optimal corrosion resistance.
6. Coiling
The finished tubes are wound onto precision-wound coils using automated coiling equipment. The coiling process is controlled to prevent kinking, deformation, or surface damage. Coil diameters and lengths are customized per customer requirements.
7. Quality Inspection
Each coil undergoes rigorous non-destructive testing (NDT) including:
- Eddy Current Testing (ECT): 100% length inspection for wall thickness, internal/external defects, and weld integrity.
- Hydrostatic Testing: Pressure testing at 1.5× maximum operating pressure for leak detection.
- Dimensional Verification: OD, wall thickness, and coil geometry measured at specified intervals.
- Surface Inspection: Visual and magnetic particle inspection for surface discontinuities.
Applications
Primary Applications
- Steam Heating Systems: Coil tubes serve as heating elements in industrial steam-heated processes, providing efficient thermal transfer through their high surface-area-to-volume ratio.
- Shell-and-Tube Heat Exchangers: The coiled configuration allows for compact arrangement within exchanger shells, maximizing heat transfer efficiency in limited footprints.
- Condensers and Reboilers: Used in distillation columns, chemical reactors, and refrigeration systems where condensation and boiling processes occur.
- Air Preheaters: Coil tubes transfer heat from flue gases to process air in power generation and industrial furnace systems.
- Food and Pharmaceutical Processing: Sanitary-grade coil tubes (BA finish) used in pasteurization, sterilization, and CIP (Clean-in-Place) systems.
Industry Segments
- Petrochemical and Refining
- Power Generation (Thermal and Nuclear)
- Pharmaceutical Manufacturing
- Food and Beverage Processing
- Marine Engineering
- Automotive Heat Management Systems
- Building Services (HVAC and District Heating)
Unique Selling Points
- Superior Thermal Efficiency: The coiled geometry maximizes heat transfer surface area within minimal installation space, reducing capital expenditure on heat exchanger vessels.
- Enhanced Corrosion Durability: Solution-annealed austenitic stainless steel provides long-term resistance to steam, condensate, and aggressive process fluids, minimizing maintenance intervals.
- Precision Dimensions: Tight tolerances (±0.05 mm OD) ensure reliable compatibility with standard tube sheets, headers, and expansion joints.
- Customizable Coiling: Flexible coil lengths and diameters accommodate diverse system designs and installation constraints.
- Full Traceability: Every coil is traceable to mill heat numbers with complete documentation, supporting regulatory compliance in safety-critical industries.
Quality Certifications
Applicable Standards
- ASTM A213 / ASME SA-213: Standard specification for seamless and welded austenitic stainless steel boiler, heat-exchanger, and similar heat-transfer service tubes.
- EN 10216-5: Non-ferrous metal tubes for pressure purposes – Technical delivery conditions for seamless stainless steel tubes for heat exchangers.
- GB/T 14976: Chinese national standard for fluid transport stainless steel seamless tubes.
- JIS G3459: Japanese Industrial Standard for austenitic stainless steel tubes for boiler, heat exchanger, and similar heat-transfer service.
- ASME BPV Code Section I: Rules for construction of power boilers (pressure design verification).
- ASTM A403: Standard specification for stainless steel tubing, seamless and welded.
Certifications and Compliance
- ISO 9001:2015: Quality Management System certification for consistent manufacturing quality.
- ISO 3834: Quality requirements for welding of metallic products.
- EN 10204 3.1: Test certificates verifying material compliance with specified standards.
- NACE MR0175 / ISO 15156: Compliance for sour service (H₂S-containing environments) where applicable.
- 3.1 Test Reports: Independent third-party material testing and verification per EN 10204.
- Mill Test Certificates (MTC): Provided with every shipment, covering chemical composition, mechanical properties, and heat treatment records.
Inspection and Documentation
Each coil is accompanied by a comprehensive quality dossier including:
- Certificate of Material Analysis (CoA) with full chemical composition
- Mechanical Test Report (tensile, hardness, impact)
- Non-Destructive Testing (NDT) Reports (Eddy Current, Hydrostatic)
- Heat Treatment Log (temperature profiles and cooling rates)
- Dimensional Inspection Report
- Mill Heat Number traceability documentation
Storage, Handling, and Packaging
- Coils are protected with VCI (Vapor Corrosion Inhibitor) paper wrapping and outer plastic film to prevent surface contamination during transit.
- Wooden or steel cradles support coil weight and prevent deformation during stacking and transport.
- Storage in dry, well-ventilated areas away from dissimilar metals to prevent galvanic corrosion.
- Handling via certified coil-handling equipment (C-hooks or roller stands) to avoid surface marring.
Technical Support
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including: