Stainless Steel Coil Tube — Burst-Tested for Superior Pressure Integrity

Product Overview

Wenzhou Jixing Metal Materials Co., Ltd. manufactures high-performance stainless steel coil tubes (also referred to as coil tubing) designed for demanding fluid transfer, heat exchange, and process engineering applications. Each coil tube is produced to exacting dimensional and mechanical tolerances, and the company distinguishes itself through a rigorous burst testing program — a type-test and R&D verification protocol that pressurizes representative samples until rupture to empirically determine the actual burst pressure and safety factor. This methodology provides customers with quantified confidence in the structural integrity and pressure resistance of every production lot.

Coil tubes are supplied in continuous, pre-formed coil configurations that facilitate high-speed automated forming, bending, and welding operations, significantly reducing fabrication waste and production cycle times compared to straight-length tubing.

Material & Properties

Stainless steel coil tubes from Wenzhou Jixing are available in a comprehensive range of austenitic and duplex grades, each selected to meet specific corrosion resistance, mechanical strength, and temperature performance requirements:

• 304 / 304L (UNS S30400 / S30403): General-purpose grade offering excellent corrosion resistance, formability, and weldability. Suitable for food processing, chemical handling, and moderate-temperature service.
• 316 / 316L (UNS S31600 / S31603): Enhanced molybdenum content provides superior resistance to chlorides, acids, and marine environments. Ideal for pharmaceutical and coastal applications.
• 321 (UNS S32100): Titanium-stabilized grade with improved resistance to intergranular corrosion at elevated temperatures (up to 870 °C / 1,598 °F).
• 310S (UNS S31008): High-temperature grade maintaining oxidation resistance up to 1,150 °C (2,094 °F) for furnace and kiln applications.
• 2205 Duplex (UNS S32205): Combined austenitic-ferritic microstructure delivering approximately double the yield strength of 304/316 with excellent chloride stress corrosion cracking resistance.
• 904L (UNS N08904): Ultra-low carbon, high-alloy grade for highly aggressive chemical environments including sulfuric and phosphoric acids.

Specifications

Parameter	Specification	Standard Reference
Outer Diameter (OD)	3.0 – 50.8 mm (0.118 – 2.000 in)	ASTM A269 / ASME SA-269
Wall Thickness	0.25 – 4.0 mm (0.010 – 0.157 in)	ASTM A269
Coil Diameter	300 – 1,500 mm (11.8 – 59.1 in)	Customer-specific
Coil Length	50 – 500 m (164 – 1,640 ft) per coil	Customer-specific
Surface Finish	Mill finish, pickled & passivated, electropolished, brushed, or mirror polished	ASTM A479
Tolerance — OD	±0.05 – ±0.15 mm (±0.002 – ±0.006 in)	ASTM A269
Tolerance — Wall Thickness	±10% of nominal	ASTM A269
Material Grades	304, 304L, 316, 316L, 321, 310S, 2205, 904L, 309S, 316Ti	ASTM A270 / A276
Forming Method	Seamless (cold drawn) or welded (ERW, orbital TIG)	ASTM A269 / A554
End Condition	Plain, beveled, or with protective caps	Customer-specific
Operating Temperature Range	−196 °C to 1,150 °C (−321 °F to 2,094 °F), grade-dependent	ASME BPV Code
Burst Test — Applied Pressure	Pressurized beyond design pressure until tube rupture	Type test / R&D verification
Burst Test — Measured Parameters	Actual burst pressure (Pb), calculated safety factor (Pb / Pdesign)	ASTM A269 / EN 10217
Packaging	Wooden crate, export-grade pallet with moisture-proof wrapping	ISO 11607 (pharma)

Manufacturing Process

1. Raw Material Procurement & Inspection

Virgin stainless steel billets or strip are sourced from certified mills with full material traceability. Incoming material undergoes spectroscopic verification (PMI) to confirm grade composition and mechanical properties prior to processing.

2. Seamless Tube Production

For seamless coil tubes, hot-rolled or cold-drawn seamless pipes are produced via the Mannesmann piercing or capillary extrusion method. The continuous coil configuration is achieved through precision cold forming over a mandrel, ensuring uniform wall thickness and consistent geometry throughout the coil length.

3. Welded Tube Production

Welded coil tubes are manufactured by cold rolling precision strip over a forming die set, followed by resistance welding (ERW) or orbital TIG welding. The continuous coil is formed in a single operation, eliminating butt joints and ensuring homogeneous mechanical properties along the entire length.

4. Heat Treatment & Annealing

Post-forming annealing at controlled temperatures (typically 1,000–1,150 °C / 1,832–2,094 °F for austenitic grades) relieves cold-work stresses, restores full corrosion resistance, and achieves the specified mechanical condition (Solution Annealed, 1/4 Hard, 1/2 Hard, Full Hard, or Soft).

5. Surface Treatment

Tubes undergo pickling and passivation to remove scale and restore the chromium oxide passive layer. Electropolishing is available for sanitary and pharmaceutical applications requiring Ra ≤ 0.4 μm (0.00002 in) surface roughness.

6. Coil Winding & Packaging

Finished tubes are wound onto precision coils with controlled tension to prevent deformation. Each coil is wrapped, labeled with lot identification, and packaged for export or domestic delivery.

Burst Testing — Type Test & R&D Verification Program

Unique Differentiator: Wenzhou Jixing Metal Materials conducts burst testing as a type-test and research & development verification protocol. Representative samples are pressurized continuously until complete tube rupture, enabling empirical determination of the actual burst pressure and the corresponding safety factor relative to design pressure. This is a non-routine factory test performed during product development, design qualification, or periodic re-verification — providing customers with definitive proof of pressure integrity margins.

Burst Test Methodology

1. Sample Selection: Representative tube sections are extracted from production coils per statistical sampling plans (AQL-based or per ASTM E8/E9).
2. Test Preparation: Samples are prepared with sealed end fittings capable of withstanding pressures exceeding the expected burst pressure. Test specimens are inspected for surface defects and dimensional conformity.
3. Pressurization: A hydraulic pressure test rig applies fluid pressure at a controlled, continuously increasing rate until the tube ruptures catastrophically.
4. Data Capture: The actual burst pressure (P_b) is recorded at the moment of rupture. The burst location, failure mode (hoop rupture, longitudinal split, or joint failure), and any pre-failure deformation are documented.
5. Safety Factor Calculation: The safety factor is determined as the ratio of burst pressure to design (working) pressure: SF = P_b / P_design. Industry standards typically require a minimum safety factor of 3.0–5.0 depending on application criticality.
6. Reporting: A comprehensive burst test report is issued, including test conditions, measured burst pressures, calculated safety factors, failure analysis, and compliance assessment against applicable codes (ASME BPV Code, PED 2014/68/EU, AD-2000-Merkblätter).

Significance of Burst Testing

• Provides empirical validation of theoretical pressure capacity calculations based on hoop stress formulas (Barlow's equation: P = 2·σ·t / D).
• Identifies material or manufacturing defects that may not be detectable through dimensional inspection or non-destructive testing alone.
• Supports design qualification for critical applications including pressure vessels, hydraulic systems, and high-pressure fluid transfer.
• Facilitates regulatory compliance and code stamping for pressure-containing equipment.
• Enables continuous improvement of manufacturing parameters through iterative R&D testing.

Applications

• Heat Exchangers & Boilers: Coil tubes for shell-and-tube heat exchangers, air-cooled condensers, and process heaters where continuous coil supply reduces welding joints and improves thermal efficiency.
• Automotive & HVAC: Refrigerant tubing, intercooler tubes, and condenser tubes requiring tight tolerances and high flow capacity.
• Food & Beverage Processing: Sanitary-grade 304L/316L coil tubes for CIP systems, pasteurizers, and hygienic fluid transfer with electropolished interiors.
• Pharmaceutical & Biotech: Weldable coil tubing for bioreactors, purification systems, and sterile fluid handling in compliance with FDA 21 CFR and EU GMP standards.
• Chemical & Petrochemical: 316L, 904L, and 2205 duplex coil tubes for acid service, refinery heat exchangers, and chemical processing plants.
• Hydraulic & Pneumatic Systems: High-pressure fluid lines where burst-tested integrity margins ensure operational safety.
• Medical Devices: Precision-drawn coil tubing for endoscopes, surgical instruments, and implantable device components.
• Marine & Offshore: Chloride-resistant 316L and duplex coil tubes for seawater systems, ballast tanks, and offshore platform piping.
• Energy & Power Generation: Boiler tubes, superheater elements, and solar thermal collector tubes operating at elevated temperatures.

Quality Certifications & Compliance

• ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and continuous improvement.
• ISO 14001:2015 — Environmental Management System for sustainable manufacturing practices.
• ISO/IEC 17025 — Laboratory competence for in-house testing including burst testing, dimensional inspection, and mechanical property verification.
• EN 10204 3.1/3.2 — Third-party inspection and material certification available upon request.
• CE Marking (PED 2014/68/EU) — Conformity with European Pressure Equipment Directive for pressure-containing applications.
• ASME Certification — Material compliance with ASME Boiler & Pressure Vessel Code (Section II, Part A) for pressure vessel and piping applications.
• Mill Test Reports (MTRs) — Full chemical composition (spectroscopic analysis) and mechanical property data provided with every shipment.
• Non-Destructive Testing (NDT) — Electromagnetic testing (ET), eddy current testing, and ultrasonic testing available for weld integrity and wall thickness verification.
• Food Contact Compliance — NSF/ANSI 61 and EC 1935/2004 compliance for food-grade applications.

Unique Selling Points

• Empirically Validated Pressure Integrity: Burst testing provides real-world proof of pressure capacity and safety margins — a level of verification that goes beyond standard hydrostatic pressure tests and theoretical calculations.
• Comprehensive Grade Selection: Over ten stainless steel grades available, from general-purpose 304 to ultra-aggressive service 904L and high-strength 2205 duplex.
• Continuous Coil Supply: Eliminates butt welds, reduces material waste by up to 30%, and enables high-speed automated fabrication.
• Full Traceability: Every coil is traceable to the original mill heat number with complete chemical and mechanical data.
• Custom Fabrication: Flexible coil diameters, lengths, surface finishes, and end conditions tailored to customer-specific requirements.
• Global Export Capability: Export-grade packaging, international certification compliance, and established logistics networks serving customers worldwide.