Stainless Steel Coil Tube — Hydrostatic Pressure Testing Specification (Static Water Pressure Holding)
1. Product Overview
The stainless steel coil tube (Coil Tube) produced by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubing product supplied in continuous coil form, designed for seamless integration into automated processing lines, heat exchanger assemblies, and high-integrity fluid transport systems. As a critical quality assurance measure, every coil tube batch undergoes a mandatory hydrostatic pressure test (Hydrostatic Pressure Test) — specifically the static water pressure holding procedure (Static Water Pressure Holding) — prior to shipment. This test verifies the structural integrity, weld soundness, and pressure containment capability of each tube, ensuring compliance with international safety standards.
2. Material & Properties
- Material Grade: Austenitic stainless steel (e.g., AISI 304, AISI 316L, SUS304, SUS316L) — selected for superior corrosion resistance, high-temperature stability, and mechanical reliability.
- Microstructure: Fully austenitic, non-magnetic (or weakly magnetic post-cold-work), providing excellent ductility and weldability.
- Corrosion Resistance: High resistance to intergranular corrosion (IGC), pitting corrosion, and stress corrosion cracking (SCC) in aggressive chemical environments.
- Mechanical Properties: Yield strength ≥ 205 MPa (annealed condition); tensile strength ≥ 515 MPa; elongation ≥ 40% — ensuring adequate safety margins under pressure loading.
3. Hydrostatic Pressure Test Specifications
| Parameter | Specification / Requirement | Reference Standard |
|---|---|---|
| Test Method | Static Water Pressure Holding (Static Hydrostatic Pressure Test) | ASTM A213, EN 10217, GB/T 12771 |
| Test Medium | Deionized water or clean tap water (non-corrosive, non-abrasive) | — |
| Test Pressure | 1.5 × Design Pressure (Pdesign) | ISO 449, EN 10217-7 |
| Hold Time (Dwell Time) | ≥ 5 seconds at full test pressure | ASTM A213, EN 10217 |
| Acceptance Criteria | No visible leakage, no seepage, no permanent deformation, no pressure drop | — |
| Inspection Frequency | 100% — Mandatory inspection for every coil tube lot before dispatch | Internal QA protocol |
| Temperature | Ambient temperature (20 ± 5 °C) | EN 10217 |
| Equipment | Calibrated hydraulic test pump with precision pressure gauge (accuracy ± 0.5% FS) | ISO 17025 traceability |
4. Manufacturing & Testing Process
- Coil Forming & Cold Drawing: Stainless steel strip is cold-rolled and formed into coil tube geometry with precise dimensional control (wall thickness tolerance ± 10%).
- Welding (if applicable): Seamless or welded coil tubes are produced using automatic orbital or TIG welding with full penetration welds.
- Pickling & Passivation: Tubes undergo acid pickling (HNO₃ + HF) followed by passivation to remove surface oxides and restore the passive chromium oxide layer.
- Hydrostatic Pressure Testing — Static Water Pressure Holding:
- Each tube coil is sealed at both ends with hydraulic plugs.
- The test chamber is pressurized with water to 1.5 × the rated design pressure.
- Pressure is maintained (held) for a minimum of 5 seconds.
- Visual and instrument-based inspection confirms zero leakage and zero permanent deformation.
- Non-conforming tubes are immediately quarantined and rejected.
- Final Inspection & Documentation: Each batch receives a test certificate including pressure test records, material test reports (MTR), and dimensional inspection data.
5. Applications
- Chemical & Petrochemical Industry: Process piping, reactor internals, and transfer lines for aggressive media.
- Food & Pharmaceutical Industry: Sanitary process lines, CIP/SIP systems, and hygienic fluid transfer.
- Heat Exchanger & HVAC Systems: Coil tubes for shell-and-tube heat exchangers, air conditioning, and refrigeration circuits.
- Automotive & Aerospace: Fuel lines, brake lines, and hydraulic systems requiring high-pressure integrity.
- Medical Equipment: Sterilization chambers, gas delivery lines, and instrument tubing.
- Water Treatment & Desalination: High-pressure RO membrane housings and brine circulation lines.
6. Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System certified production.
- ISO 17025 — Testing laboratory traceability and calibration standards.
- CE Marking (PED Directive 2014/68/EU) — Pressure Equipment Directive compliance for EU market.
- EN 10204 3.1 — Inspection certificate issued per lot.
- ASTM A213 / EN 10217 / GB/T 12771 — Product standard conformance.
- 100% Hydrostatic Pressure Testing — Mandatory pre-shipment inspection ensuring zero-defect delivery.
7. Unique Selling Points
Zero-Leakage Guarantee: The 1.5× design pressure hold test (≥ 5 seconds) provides a safety factor of 50% above operational conditions, guaranteeing absolute pressure integrity for the entire service life of the coil tube.
- Full Batch Traceability: Every coil tube is individually tested, recorded, and documented — enabling complete traceability from raw material to end user.
- Non-Destructive Verification: The hydrostatic test confirms weld integrity, wall uniformity, and absence of manufacturing defects (pinholes, inclusions, stress concentrations) without damaging the product.
- Compliance with Global Standards: Testing protocols align with ASTM, EN, ISO, and GB standards, facilitating global market acceptance.
- Enhanced Safety Margins: The conservative 1.5× pressure multiplier accounts for transient overpressure events, ensuring reliable performance under real-world operating conditions.