Stainless Steel Coil Tube — Sand-Blasting Cleaning Application for Large-Diameter Casings
1. Product Overview
The Stainless Steel Coil Tube (SSCT) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous pipe product formed into a compact coil configuration. Unlike conventional straight-length tubes, coil tubes offer exceptional versatility in downstream processing due to their continuous, seamless length and reduced material waste. This product line is specifically designed for demanding industrial applications, including the sand-blasting cleaning (冲砂清洗) of large-diameter casings in the oil and gas, petrochemical, and power generation sectors.
Coil tubes are produced through continuous forming and welding processes, enabling the manufacture of extremely long lengths without intermediate joints. This characteristic makes them ideal for applications requiring extended, uninterrupted internal surfaces — such as cleaning tools, perforated liners, and casing intervention equipment.
2. Material & Properties
The coil tubes are fabricated from premium-grade austenitic and duplex stainless steel grades, selected for superior corrosion resistance, mechanical strength, and formability. Key material grades include:
- 304 / 304L (UNS S30400 / S30403) — General-purpose corrosion resistance, excellent weldability, suitable for moderate chloride environments.
- 316 / 316L (UNS S31600 / S31603) — Enhanced pitting and crevice corrosion resistance due to molybdenum (Mo) content; preferred for chemical and marine applications.
- 321 (UNS S32100) — Stabilized with titanium (Ti); resists intergranular corrosion at elevated temperatures (450–850°C).
- 310S (UNS S31008) — High-temperature oxidation resistance up to 1150°C; used in extreme thermal environments.
- 316L (UNS S31603) — Low-carbon variant for superior weldability and resistance to sensitization.
- Duplex 2205 (UNS S31803 / S32205) — Combined austenitic-ferritic microstructure offering 2–3× the yield strength of 304/316 with excellent chloride stress corrosion cracking (SCC) resistance.
Key Mechanical Properties (Typical Values for 304/316L Coil Tube):
- Tensile Strength (UTS): 515–720 MPa (75,000–104,000 psi)
- Yield Strength (0.2% Offset): ≥205 MPa (≥29,700 psi)
- Elongation: ≥40% (minimum)
- Hardness (Rockwell B): ≤92
- Specific Gravity: 8.0 g/cm³
- Thermal Conductivity: 16.3 W/(m·K) at 32°C
- Thermal Expansion Coefficient: 16–17.3 × 10⁻⁶ /°C (10–32°C)
- Operating Temperature Range: −196°C to 870°C (304/316L); up to 1150°C (310S)
3. Technical Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.18 mm (⅛") to 168.3 mm (6½") | ASTM A213 / A269 / A219 |
| Wall Thickness (WT) | 0.25 mm to 12.7 mm (0.010" to ½") | ASTM A213 / A269 |
| OD Tolerance | ±0.10 mm (±0.004") for OD ≤ 50.8 mm; ±0.15 mm for OD > 50.8 mm | ASTM A213 / ASME B36.19M |
| Wall Thickness Tolerance | ±10% of nominal | ASTM A213 / EN 10216-5 |
| Coil Length (Continuous) | Up to 5,000 m (16,404 ft) per coil | Manufacturer Specification |
| Coil Inner Diameter | 500 mm to 1,500 mm (20" to 60") | Manufacturer Specification |
| Surface Finish | Mill finish, pickled & passivated, or polished (Ra ≤ 0.4 μm) | ASTM A240 / ASME SA-240 |
| Welding Process | Longitudinal TIG (GTAW) or orbital welding; seamless (ERW/autoclave) options available | ASTM A213 / AWS D10.9 |
| Heat Treatment | Solution annealing (1050–1150°C) followed by rapid quenching | ASTM A213 / ASTM A999 |
| Coil Packaging | Steel drum or protective wrap with desiccant; wooden pallet base | ISO 1496 / Manufacturer Standard |
| Maximum Coil Weight | Up to 15,000 kg (33,070 lbs) | Manufacturer Specification |
| Applicable Standards | ASTM A213, A269, A219, A312; ASME SA-213, SA-269, SA-219; EN 10216-5; GB/T 12771 | Multi-standard compliance |
4. Manufacturing Process
The production of stainless steel coil tubes follows a rigorous, multi-stage manufacturing sequence designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Procurement & Inspection: Hot-rolled coil (HRC) or cold-rolled strip is sourced from certified mills. Incoming materials undergo spectroscopic analysis (OES), chemical composition verification, and mechanical property testing per ASTM E1010 and ASTM E8.
- Strip Preparation: The coil strip is leveled, slit to required width, and cleaned to remove surface contaminants, oils, and scale. Strip width is calculated based on the target tube OD and seam allowance.
- Coil Forming (Roll Forming): The flat strip passes through a series of precision roll stands that progressively bend it into the desired circular cross-section. This cold-forming process is performed at controlled speeds to maintain dimensional consistency and prevent work hardening.
- Longitudinal Welding: The formed tube is welded along the longitudinal seam using Gas Tungsten Arc Welding (GTAW/TIG) or Plasma Arc Welding (PAW). Inert gas shielding (argon or argon-helium mix) prevents oxidation. Weld parameters are precisely controlled to ensure full penetration and a uniform weld bead.
- Weld Annealing (Solution Treatment): The welded tube is heat-treated at 1050–1150°C to homogenize the weld zone, dissolve carbides, and restore full austenitic corrosion resistance. This step eliminates residual stresses and weld sensitization.
- Precision Sizing & Straightening: The tube passes through a sizing mill to achieve final OD and wall thickness tolerances. A straightening unit ensures the tube runs true within the coil.
- Pickling & Passivation: The tube is cleaned using acid pickling (nitric/hydrofluoric acid blend) to remove mill scale and oxidation, followed by passivation to establish a protective chromium oxide film. This ensures optimal corrosion resistance and surface cleanliness.
- Coil Winding & Packaging: The finished tube is wound into coils of the specified diameter and length. Coils are wrapped with protective film, secured with steel strapping, and palletized for shipping.
- Final Quality Control: Each coil undergoes non-destructive testing (NDT) including eddy current inspection, hydrostatic pressure testing (per ASTM A213/A269), dimensional verification, and visual examination of weld seams.
5. Applications
5.1 Sand-Blasting Cleaning of Large-Diameter Casings (Primary Application)
A critical and specialized application of stainless steel coil tubes is in the sand-blasting (冲砂) cleaning of large-diameter casings used in oil well completion and intervention operations. This process involves the following methodology:
- Tool Fabrication: Stainless steel coil tubes are fabricated into flexible cleaning tools, scrub brushes, and sand-blasting nozzles. The coil's continuous length and inherent flexibility allow the tool to navigate through large-diameter casings (typically 5-1/2" to 20") with minimal handling.
- Internal Cleaning: The coil tube-based tools are deployed into cased wells to remove scale deposits, cement residues, sand accumulation, and corrosion products from the interior surfaces of production casings and liners.
- Advantages over Conventional Methods: Coil tube tools offer superior flexibility and conformability compared to rigid cleaning tools, reducing the risk of casing damage. The stainless steel material resists corrosion from produced fluids (containing chlorides, H₂S, and CO₂), ensuring tool longevity and minimizing contamination of wellbore fluids.
- Process Efficiency: The continuous coil format enables rapid deployment and retrieval, significantly reducing intervention time and associated operational costs. Multiple cleaning passes can be performed with a single tool deployment.
5.2 Additional Applications
- Oil & Gas Industry: Perforated liner strings, tubing spools, sand control screens, and well completion components.
- Chemical Processing: Heat exchanger tubes, reactor internals, piping systems for aggressive chemical transport.
- Food & Pharmaceutical: Sanitary-grade tubing for processing, storage, and transfer of food products, pharmaceuticals, and biotechnology fluids.
- Power Generation: Boiler tubes, superheater elements, and condensate lines in thermal and nuclear power plants.
- Marine & Offshore: Subsea umbilical components, ballast water systems, and offshore platform piping.
- Automotive: Exhaust system components, fuel delivery lines, and emission control systems.
- Medical Devices: Endoscope tubing, surgical instrument shafts, and implant-grade components.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and certifications ensuring product conformance to international standards:
- ISO 9001:2015 — Quality Management System certification, demonstrating systematic adherence to quality principles throughout the manufacturing lifecycle.
- ISO 14001:2015 — Environmental Management System, reflecting commitment to sustainable and environmentally responsible production practices.
- ISO 45001:2018 — Occupational Health and Safety Management System.
- API 5CT / API 5L Compliance — For oil and gas industry applications, products meet American Petroleum Institute (API) requirements for casing and tubing materials.
- NACE MR0175 / ISO 15156 — Compliance with standards for materials resistant to sulfide stress cracking (SSC) and hydrogen-induced cracking (HIC) in sour (H₂S-containing) environments.
- ASME B31.3 / B31.5 — Conformance with piping code requirements for process and fluid systems.
- EN 10204 3.1 / 3.2 — Third-party inspection and certification of material test reports.
- CE Marking — European Conformity marking for products intended for the European Economic Area (EEA).
- Mill Test Certificates (MTC) — Full chemical composition, mechanical property, and NDT results provided with every shipment.
7. Unique Selling Points
Continuous Coil Format for Maximum Flexibility: The coil tube format eliminates butt joints and allows for unlimited downstream cutting and fabrication. This is particularly advantageous for sand-blasting tool fabrication, where seamless, continuous internal surfaces are critical for effective casing cleaning.
Specialized Application Expertise: Wenzhou Jixing Metal Materials Co., Ltd. possesses deep technical knowledge in applying coil tubes to large-diameter casing cleaning operations. This domain-specific expertise translates into optimized product specifications tailored for sand-blasting tool performance.
Multi-Grade Material Availability: From standard 304/316L to high-strength duplex 2205 and high-temperature 310S, the product range covers virtually every corrosion and thermal environment encountered in industrial operations.
Superior Surface Integrity: The pickling and passivation process ensures a clean, oxide-free surface with enhanced corrosion resistance — critical for maintaining fluid integrity during casing cleaning operations.
Custom Fabrication Capability: Coils can be supplied in custom diameters, wall thicknesses, and lengths to meet specific project requirements, including special alloy compositions for extreme service conditions.
Full Traceability & Documentation: Every coil is accompanied by comprehensive test documentation, including chemical analysis, mechanical test