Stainless Steel Pressure-Bearing Coiltube — Wenzhou Jixing Metal Materials Co., Ltd.

Product Overview

The Stainless Steel Coiltube (also referred to as Coiled Tubing or Pressure-Bearing Coiltube) is a precision-engineered, continuously wound stainless steel tube designed for demanding pressure-containing applications. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product represents the culmination of advanced metallurgical science and rigorous pressure-bearing design methodology. The coiltube is formed through a seamless coiling process that eliminates longitudinal weld seams, thereby providing superior structural integrity, uniform wall thickness, and exceptional resistance to internal and external pressure loads.

Unlike conventional straight-pipe assemblies that require welding at connection points—creating potential weak zones—the coiltube is delivered as a single, continuous, and unbroken tube wound onto a spool. This design philosophy fundamentally reduces failure risk in high-pressure, high-temperature, and corrosive environments. The product is particularly suited for applications where fatigue resistance, thermal cycling endurance, and corrosion performance are critical operational parameters.

Design Philosophy: The pressure-bearing design methodology for coiltubes integrates principles of elastic-plastic mechanics, hoop stress analysis, and fatigue life prediction to ensure that the tube maintains structural integrity under sustained and transient pressure loads. The design accounts for geometric nonlinearities introduced by the coiling radius, residual stresses from cold working, and the interaction between internal pressure and bending moments.

Material & Properties

The coiltube is fabricated from high-grade austenitic stainless steels conforming to international standards. The primary material grades offered include:

Key Mechanical and Physical Properties (Typical — Grade 316L)

Property Value / Range Test Standard
Tensile Strength (Ultimate) ≥ 515 MPa (75 ksi) ASTM A270 / EN 10217-7
Yield Strength (0.2% Proof) ≥ 205 MPa (30 ksi) ASTM A270 / EN 10217-7
Elongation at Break ≥ 35% ASTM A270
Hardness (Rockwell B) ≤ 95 HRB ASTM E140
Operating Temperature Range −196 °C to +870 °C —
Maximum Working Pressure (design-dependent) Up to 25 MPa (3,626 psi) ASME B31.3 / EN 13480
Thermal Conductivity (25 °C) 16.3 W/(m·K) ASTM E153
Electrical Resistivity (25 °C) 0.74 μΩ·m ASTM E116
Corrosion Resistance (Pitting) PREN ≥ 24 ASTM G48

Specifications

The following table outlines the dimensional and performance specifications available for the Wenzhou Jixing Coiltube product line. Custom specifications can be developed upon request to meet specific project requirements.

Parameter Specification / Range Notes
Outer Diameter (OD) 6.35 mm – 25.40 mm (1/4" – 1") Standard series; custom OD available
Wall Thickness 0.50 mm – 3.00 mm Thin-wall to heavy-wall options
Coiling Radius 0.3 m – 3.0 m (1 ft – 10 ft) Determined by application requirements
Tube Length (per spool) 100 m – 5,000 m (328 ft – 16,404 ft) Continuous length; no butt welds
Surface Finish 2B, BA (Bright Annealed), No. 4, No. 8, Mirror Ra ≤ 0.05 μm for mirror finish
End Preparation Plain cut, Beveled (37.5° ± 2.5°), Flanged, Threaded Custom end prep available
Dimensional Tolerance (OD) ± 0.10 mm (± 0.004") Per ASTM A270 / EN 10217-7
Dimensional Tolerance (Wall) ± 10% of nominal Per ASTM A270
Coiling Tolerance ± 2% of nominal radius Ensures uniform stress distribution
Weight (per meter) 0.15 kg/m – 2.50 kg/m Dependent on OD and wall thickness

Applicable Standards

Manufacturing Process

The manufacturing of pressure-bearing coiltubes follows a meticulously controlled multi-stage process to ensure dimensional accuracy, metallurgical integrity, and pressure containment performance. The process flow is outlined below:

  1. Raw Material Selection and Inspection:

    High-purity stainless steel slabs or ingots are sourced from certified suppliers. Incoming materials undergo rigorous chemical composition analysis (via Optical Emission Spectrometry, OES), mechanical property testing, and visual inspection to ensure conformance to the specified grade and standard.

  2. Hot Rolling and Annealing:

    The selected steel slabs are hot-rolled into strip stock of precise dimensions. Intermediate annealing cycles are performed to relieve residual stresses and refine grain structure, ensuring optimal formability for subsequent cold working operations.

  3. Tube Forming (Seamless or Welded):

    For seamless tubes, the strip is wound around a mandrel and the longitudinal seam is welded using Transverse Welding or Longitudinal Welding (TIG/Orbital welding). The weld zone is subsequently annealed to restore full metallurgical homogeneity. For seamless extrusion, a solid billet is pierced and extruded through a die to produce tube stock without a weld seam.

  4. Cold Drawing and Sizing:

    The tube is cold-drawn through a series of progressively reducing dies to achieve the target outer diameter and wall thickness. This cold working process enhances mechanical properties through work hardening while maintaining tight dimensional tolerances.

  5. Intermediate Annealing:

    Periodic solution annealing (typically at 1050 °C – 1150 °C followed by rapid cooling) is performed between cold drawing stages to prevent cracking, restore ductility, and precipitate carbides uniformly.

  6. Surface Treatment:

    The tube undergoes pickling and passivation to remove surface oxides, contaminants, and decarburized layers. This process forms a stable, protective chromium oxide film that enhances corrosion resistance. Surface finishing (polishing, electropolishing) is applied according to the specified finish grade.

  7. Coiling:

    The finished tube is coiled onto a spool using a controlled coiling machine. The coiling radius is precisely maintained within tolerance to ensure uniform stress distribution and prevent localized deformation. The coiling process is monitored using load cells and radius sensors to detect and correct any deviation in real time.

  8. Pressure Testing:

    Each coil is subjected to hydrostatic pressure testing at 1.5 times the maximum design working pressure for a minimum dwell time of 10 seconds. The test pressure is calculated in accordance with ASME B31.3 or the applicable project specification. Any tube exhibiting leakage, deformation, or dimensional change is rejected.

  9. Final Inspection and Certification:

    Comprehensive final inspection includes dimensional verification (laser measurement), surface quality assessment (visual and magnetic particle testing, MPI), chemical composition re-verification, and mechanical property sampling. A full mill test certificate (MTC) is issued for each batch, conforming to EN 10204 Type 3.1 requirements.

Applications

The stainless steel pressure-bearing coiltube finds extensive application across multiple high-value industries where reliability, corrosion resistance, and pressure integrity are paramount:

Oil and Gas Industry

Chemical and Petrochemical Processing

Food and Beverage Industry

Power Generation

Marine and Offshore

Medical and Laboratory

Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and approvals:

Quality Assurance Protocol

Every production batch undergoes a multi-tiered quality assurance protocol:

Unique Selling Points