Internal Threaded Coil Tube (Coiltube) — Technical Specification
1. Product Overview
The Internal Threaded Coil Tube (product code: JX-CT-1226) is a precision-engineered coiled tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is supplied in continuous coil form (Coiltube), designed for applications requiring both structural integrity and internal threading for mechanical connection purposes. The coil tube is available in stainless steel and copper alloy grades, with the internal thread profile machined to precise dimensional tolerances to ensure reliable assembly in heat exchange, refrigeration, plumbing, and industrial process systems.
The distinguishing feature of this product lies in the Finalizing Process Quality Control (精整工序质量控制) — a rigorous post-machining stage that ensures the dimensional accuracy, surface finish, and thread integrity of the internal helical profile. This quality control framework encompasses multi-stage inspection protocols covering geometric accuracy, surface roughness, thread gauge compliance, and material certification verification.
2. Material & Properties
The coil tube is fabricated from high-purity alloy materials selected to meet or exceed international standards. The following materials are available:
- Stainless Steel 304 (UNS S30400) — Austenitic stainless steel with excellent corrosion resistance, suitable for general industrial and food-grade applications.
- Stainless Steel 316L (UNS S31603) — Low-carbon austenitic stainless steel with added molybdenum for enhanced resistance to pitting and crevice corrosion in aggressive environments.
- Copper C12200 (T2 Grade) — High-conductivity copper alloy with superior thermal performance and excellent solderability, ideal for refrigeration and HVAC coil applications.
- Copper C12010 (TU1 Grade) — Oxygen-free copper with ultra-high purity, designed for high-temperature and high-reliability thermal applications.
2.1 Key Mechanical Properties
| Property | SS 304 | SS 316L | Copper C12200 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 485 | ≥ 210 |
| Yield Strength (MPa) | ≥ 205 | ≥ 170 | ≥ 69 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 45 |
| Thermal Conductivity (W/m·K, 25°C) | 16.3 | 14.6 | 398 |
| Density (g/cm³) | 8.00 | 8.03 | 8.94 |
| Maximum Operating Temperature (°C) | 870 | 870 | 250 |
| Corrosion Resistance (Salt Spray, hours) | ≥ 1000 | ≥ 2000 | ≥ 500 |
2.2 Thread Specification
The internal thread profile is machined to one of the following standard thread forms, depending on application requirements:
- NPT (National Pipe Thread) — Tapered thread per ASME B1.20.1
- BSP (British Standard Pipe) — Tapered thread per ISO 7-1
- Metric (M) — Parallel thread per ISO 68-1
- Custom Thread Profiles — Available upon specification with minimum order quantities
3. Specifications
| Parameter | Specification |
|---|---|
| Product Code | JX-CT-1226 |
| Product Category | Internal Threaded Coil Tube (Coiltube) |
| Outer Diameter (OD) Range | 6.0 mm – 50.8 mm (¼" – 2") |
| Wall Thickness Range | 0.5 mm – 3.0 mm |
| Inner Diameter (ID) Range | 4.0 mm – 45.0 mm |
| Coil Diameter | Φ 500 mm – Φ 1200 mm (standard); custom upon request |
| Coil Weight | 50 kg – 300 kg per coil |
| Coil Length | 5 m – 100 m per coil (configurable) |
| Thread Pitch Tolerance | ± 0.02 mm |
| OD Tolerance | ± 0.05 mm |
| Wall Thickness Tolerance | ± 0.03 mm |
| Surface Roughness (Ra) | ≤ 0.8 μm (internal thread surface) |
| Surface Finish | Polished / Passivated / Matte / Custom |
| Available Materials | SS 304, SS 316L, Copper C12200, Copper C12010 |
| Standard References | ASTM B751, ASTM B730, EN 10217, GB/T 14976 |
| Packaging | Wooden pallet with moisture-proof wrapping; coil secured with steel strapping |
| Minimum Order Quantity | 500 meters per specification |
4. Manufacturing Process
The production of the Internal Threaded Coil Tube follows a multi-stage manufacturing workflow designed to ensure dimensional precision, metallurgical integrity, and surface quality. Each stage is subject to defined quality control checkpoints.
4.1 Process Flow
- Raw Material Procurement & Inspection — Ingot or wire rod materials are sourced from certified mills. Incoming material undergoes spectroscopic analysis (OES/XRF) to verify chemical composition compliance with ASTM/EN specifications. Heat number traceability is established at this stage.
- Wire Drawing (Wire Drawing Process) — Billet wire is cold-drawn through a series of progressively reducing dies to achieve the target outer diameter and wall thickness. Drawn wire is annealed in a protective atmosphere furnace (atmospheric annealing) to relieve cold work stresses and restore ductility.
- Coiling (Coil Forming) — The drawn wire is coiled onto precision mandrels to form the initial coil geometry. Coil diameter and pitch are controlled by CNC-driven winding equipment to maintain uniformity.
- Internal Threading (Internal Thread Machining) — The coil tube is advanced through a continuous threading station where internal helical threads are formed using high-precision thread milling cutters or rolling dies. The threading process is executed at controlled feed rates to minimize work hardening and burr formation.
- Finalizing Process (精整工序 — Finalizing Stage) — This is the critical quality control stage that distinguishes this product. The finalizing process includes:
- Deburring & Edge Breaking — All thread entry and exit points are deburred using automated wire brushes and rotary tools to achieve a burr-free surface.
- Surface Polishing — Internal surfaces are polished using multi-stage abrasive treatment to achieve Ra ≤ 0.8 μm surface roughness.
- Passivation Treatment — Stainless steel coils undergo acid pickling and passivation (per ASTM A967) to remove free iron and enhance corrosion resistance.
- Dimensional Verification — Each coil undergoes 100% thread gauge inspection (go/no-go gauges) and sampling of dimensional measurements using coordinate measuring machines (CMM).
- Non-Destructive Testing (NDT) — Eddy current testing (ECT) and ultrasonic testing (UT) are performed to detect internal defects, wall thickness variations, and thread integrity issues.
- Final Packaging & Labeling — Coils are wrapped in moisture-proof polyethylene film, secured with steel strapping, and palletized on treated hardwood. Each coil is labeled with heat number, material grade, specification reference, and production date.
4.2 Quality Control Framework for the Finalizing Stage
The finalizing process quality control system is structured around the PDCA (Plan-Do-Check-Act) cycle, with the following control points:
- In-Process Inspection (IPI) — Real-time monitoring of thread pitch, depth, and surface roughness during machining using in-line optical sensors and laser micrometers.
- First Article Inspection (FAI) — Comprehensive dimensional and metallurgical verification of the first coil from each production batch before mass production commences.
- Statistical Process Control (SPC) — Control charts are maintained for critical dimensions (OD, wall thickness, thread pitch) to detect process drift and ensure capability indices (Cpk) remain above 1.33.
- Final Release Inspection (FRI) — A final audit by the Quality Assurance department verifies all documentation, test reports, and material certifications before shipment authorization.
5. Applications
The Internal Threaded Coil Tube finds extensive application across multiple industries due to its combination of coil-form convenience, internal threading for secure mechanical connections, and material versatility:
- HVAC & Refrigeration Systems — Evaporator and condenser coils, refrigerant distribution lines, and heat exchanger assemblies where high thermal conductivity (copper grades) and corrosion resistance (stainless steel grades) are required.
- Automotive Industry — Intercooler pipes, engine cooling system components, and fuel delivery lines requiring compact coil geometry and precise thread engagement.
- Food & Pharmaceutical Processing — Sanitary-grade tubing for fluid transfer systems where hygienic internal surfaces and corrosion resistance are critical (SS 316L recommended).
- Oil & Gas Industry — Downhole tubing connections, chemical injection lines, and subsea equipment requiring high-pressure resistance and corrosion tolerance.
- Plumbing & Domestic Water Systems — Threaded connection points for water supply, gas distribution, and heating systems in residential and commercial installations.
- Chemical Processing — Process piping for aggressive chemical environments where SS 316L provides superior resistance to pitting and stress corrosion cracking.
- Power Generation — Steam generator tubes, feedwater systems, and condensate lines in thermal power plants.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and product certification framework:
- ISO 9001:2015 — Quality Management System certification, ensuring consistent production quality and process control.
- ISO 14001:2015 — Environmental Management System certification, demonstrating commitment to environmentally responsible manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- EN 10204 3.1 Certificates — Third-party witnessed material test certificates provided with each shipment, verifying chemical composition, mechanical properties, and dimensional compliance.
- ASME B751 / ASTM B730 Compliance — Product dimensions and material properties conform to recognized international standards for seamless stainless steel tube.
- CE Marking — Conformity with European Union directives for products intended for the European market.
- Pressure Equipment Directive (PED) 2014/68/EU — Available for applications requiring pressure vessel or piping component certification.
- Mill Test Reports (MTR) — Full traceability from raw material heat number through to finished product, including spectroscopic analysis, mechanical test results, and dimensional inspection records.
7. Unique Selling Points
The Internal Threaded Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. offers several distinguishing advantages over conventional alternatives:
- Rigorous Finalizing Process Quality Control — The dedicated finalizing stage (精整工序) with its multi-layered inspection protocol ensures that every coil tube meets the highest standards of dimensional accuracy and surface quality. This is not a post-production inspection step but an integrated manufacturing phase with real-time process control.
- Coil Form Supply Efficiency — The coiltube configuration eliminates the need for straight-length cutting and reduces material waste by up to 15% compared to straight pipe supply. It also enables automated coil feeding in downstream fabrication operations.