Stainless Steel Coil Tube (Coiltube) — Settler Stripping Steam Application
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled tubing product designed for high-temperature, high-pressure industrial applications, particularly in petrochemical and refining environments. This product is specifically optimized for use in Settler Stripping Steam Coil Nozzle Systems, where it serves as a critical heat exchange and steam distribution component within atmospheric and vacuum distillation units.
The coil tube is fabricated from high-grade austenitic stainless steel, offering exceptional resistance to thermal fatigue, corrosion, and mechanical stress under continuous cycling conditions. Its helical coil geometry provides a high surface-area-to-volume ratio, enabling efficient heat transfer and uniform steam distribution in stripper and settler vessels.
Industry Context: In refinery operations, the settler (settling drum) is an essential vessel used to separate vapor from liquid streams. The stripping steam coil nozzle assembly introduces superheated steam into the settler to strip light hydrocarbons from heavier fractions. The coil tube must withstand repeated thermal cycling, aggressive process media, and sustained mechanical loads, demanding the highest material and fabrication standards.
Material & Properties
Base Material Composition
The coil tube is typically fabricated from the following stainless steel grades, selected based on the specific service conditions:
- SAE 304 / ASTM A312 TP304 (UNS S30400): General-purpose austenitic stainless steel with excellent corrosion resistance and formability. Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- SAE 316 / ASTM A312 TP316 (UNS S31600): Enhanced pitting and crevice corrosion resistance due to 2–3% Molybdenum (Mo) addition. Preferred for chloride-containing environments.
- SAE 321 / ASTM A312 TP321 (UNS S32100): Stabilized austenitic grade with Titanium (Ti) stabilization to prevent sensitization at elevated temperatures (up to 870°C).
- SAE 347 / ASTM A312 TP347 (UNS S34700): Niobium (Nb)-stabilized austenitic grade offering superior resistance to intergranular corrosion at high service temperatures.
- SAE 310S / ASTM A312 TP310S (UNS S31008): High-temperature grade with elevated Chromium (25%) and Nickel (19%) content, suitable for sustained temperatures up to 1100°C.
Mechanical Properties (Typical — ASTM A312)
| Property | SAE 304 | SAE 316 | SAE 321 | SAE 347 | SAE 310S |
|---|---|---|---|---|---|
| Yield Strength (0.2% Offset), min. (MPa) | 205 | 205 | 205 | 205 | 205 |
| Tensile Strength, min. (MPa) | 515 | 515 | 515 | 515 | 515 |
| Elongation, min. (%) | 40 | 40 | 40 | 40 | 40 |
| Maximum Service Temperature (°C) | 870 | 870 | 900 | 925 | 1100 |
| Corrosion Resistance Rating (ASTM G48) | Good | Excellent | Good | Good | Good |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 16.3 | 15.9 | 15.9 | 21.5 |
Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) — Item No. 1388 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Applicable Standards | ASTM A312 / ASME SA-312, GB/T 12771, EN 10217-7 |
| Outer Diameter (OD) Range | 6.0 mm – 108.0 mm (custom sizes available) |
| Wall Thickness Range | 0.5 mm – 6.0 mm |
| Coil Winding Diameter | Custom, typically 300 mm – 2000 mm |
| Coil Length | Custom, up to 500 m per coil |
| Surface Finish | Pickle & Polish (2B), Brushed, or Mirror (No. 4 / 8K) |
| End Form | Plain cut, beveled, or threaded (per drawing) |
| Tolerance — OD | ±0.05 mm (precision grade) / ±0.1 mm (standard grade) |
| Tolerance — Wall Thickness | ±0.03 mm (precision grade) / ±0.05 mm (standard grade) |
| Pressure Rating | Up to 4.0 MPa (design-dependent) |
| Operating Temperature Range | −196°C to +1100°C (grade-dependent) |
| Heat Treatment | Solution Annealing (1050–1150°C) followed by rapid quenching |
| Non-Destructive Testing (NDT) | Eddy Current (ASTM E309), Hydrostatic Testing, Radiographic Testing |
| Coil Packing | Wooden crate with moisture-absorbent desiccant, suitable for international shipping |
Manufacturing Process
The production of high-quality stainless steel coil tubes involves a rigorous multi-stage process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
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Raw Material Selection & Incoming Inspection:
Hot-rolled stainless steel strip or seamless pipe blanks are sourced from certified mills. Incoming materials undergo Chemical Composition Analysis (CA) via Optical Emission Spectroscopy (OES) and mechanical property verification to ensure compliance with ASTM A312 / ASME SA-312 specifications.
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Hot Rolling & Annealing:
Raw steel slabs are hot-rolled into strip or pipe blanks. The material is subsequently solution-annealed at temperatures between 1050°C and 1150°C, followed by rapid water or air quenching to achieve a fully austenitic microstructure with optimal ductility.
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Cold Drawing / Cold Forming:
The annealed strip or pipe is cold-drawn through precision dies to achieve the target outer diameter and wall thickness. This process enhances mechanical strength and dimensional accuracy while maintaining the desired grain structure.
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Coil Winding (Coiling):
The formed tube is wound into a helical coil configuration using CNC-controlled coiling equipment. The winding process is carefully controlled to prevent kinking, wrinkling, or localized plastic deformation. The coil pitch and winding diameter are maintained within specified tolerances.
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Pickling & Passivation:
The coiled tube is subjected to acid pickling (typically using a mixture of nitric acid and hydrofluoric acid) to remove oxide scale and surface contaminants. A subsequent passivation treatment forms a protective chromium oxide layer, enhancing corrosion resistance.
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Precision Polishing (Optional):
For applications requiring enhanced surface finish, the coil tube undergoes mechanical or electrolytic polishing to achieve a surface roughness of Ra ≤ 0.4 μm. This is critical for hygienic and high-velocity flow applications.
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Non-Destructive Testing (NDT):
100% of production undergoes Eddy Current Testing (ECT) in accordance with ASTM E309 to detect internal and surface discontinuities. Additional Hydrostatic Testing is performed at 1.5× the maximum design pressure to verify pressure integrity.
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Final Inspection & Packaging:
Dimensional verification is performed using calibrated measuring instruments. Each coil is tagged with a unique Heat Traceability Number (HTN), accompanied by a Mill Test Certificate (MTC / EN 10204 3.1 Certificate). Coils are packaged in moisture-protected wooden crates for safe transport.
Applications
The Stainless Steel Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. is engineered for demanding industrial applications, with particular emphasis on the following sectors:
1. Petrochemical & Refining Industry
- Settler Stripping Steam Coil Nozzle Systems: Primary application — the coil tube serves as the heat transfer element in settler vessels, where superheated steam is introduced to strip volatile hydrocarbons from heavier process streams. The coil geometry ensures uniform heat distribution and efficient mass transfer.
- Atmospheric and Vacuum Distillation Units (ADU/VU): Used in reboiler coil assemblies, overhead condensers, and fractionation tower internals.
- Catalytic Cracking Units (FCC): Coil tubes in feed preheat exchangers and catalyst regeneration systems.
- Hydrotreating and Hydrocracking Units: High-temperature reactor effluent coolers and heat recovery coils.
2. Oil & Gas Processing
- Subsea production risers and flowlines
- Gas processing plant heat exchanger coils
- Liquefied Natural Gas (LNG) transport and storage systems
3. Chemical Processing
- Reactor internals and jacketed coil systems
- Distillation column reboilers and condensers
- Corrosive chemical storage tank heating coils
4. Power Generation
- Boiler tube banks and superheater coils
- Heat recovery steam generator (HRSG) coils in combined cycle plants
- Cooling tower and condenser tube assemblies
5. Food & Pharmaceutical Industry
- Sanitary process coils for heat exchangers and pasteurization systems
- CIP (Clean-In-Place) compatible coil assemblies
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications:
| Certification | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — certified for design, manufacturing, and supply of metallic products |
| ISO 14001:2015 | Environmental Management System — ensuring environmentally responsible manufacturing practices |
| EN 10204 3.1 | Inspection Certificate — material-specific test results issued by an authorized quality control department |
| NADCAP (if applicable) | Aerospace and defense supply chain accreditation for heat treatment and NDT processes |
| ASME Section IX | Welding Procedure Qualification — for coil tube fabrication involving welded joints |
| API 5L / API 5CT (if applicable) | American Petroleum Institute standards for line pipe and tubular products |
| CE Marking | Conformity with European Union Pressure Equipment Directive (PED 2014/68/EU) where applicable |
| Material Traceability | Full Heat Number (HTN) traceability from raw material mill to finished coil product |
Unique Selling Points
- Application-Specific Engineering: Coil tubes are specifically engineered for settler stripping steam nozzle applications, with optimized coil geometry and material selection for maximum thermal efficiency and service life in high-temperature, corrosive refinery environments.
- Full Material Grade Portfolio: Availability of SAE 304, 316, 321, 347, and 310S grades allows precise matching of material properties to the specific service conditions — from ambient-temperature condensers to high-temperature reboiler applications.
- Precision Dimensional Control: Tolerances as tight as ±0.03 mm on wall thickness and ±0.05 mm on outer diameter ensure reliable fit-up during installation and minimize field fabrication requirements.
- Comprehensive NDT Coverage: 100% Eddy Current Testing and Hydrostatic Testing provide absolute confidence in product integrity, reducing the risk of in-service failure and unplanned shutdowns.
- Complete Traceability: Every coil is accompanied by a full Heat Traceability record and EN 10204 3.1 Material Test Certificate, ensuring full compliance with international procurement and regulatory requirements.
- Custom Coil Configuration: Customizable coil winding diameter, pitch, and total length to meet specific equipment design requirements, from small pilot units to large-scale refinery installations.
- Surface Finish Options: Range of surface finishes from standard pickled and passivated to mirror-polished (Ra ≤ 0.4 μm), accommodating both industrial and hygienic process requirements.
Technical Notes for Settler Stripping Steam Coil Nozzle Application
In the specific context of Settler Stripping Steam Coil Nozzle Renovation, the following engineering considerations are critical:
- Thermal Cycling Resistance: The coil tube must withstand repeated thermal cycling between ambient temperature and superheated steam temperatures (typically 350°C – 500°C). Grades SAE 321 and SAE 347