Stainless Steel Coil Tube – Hydrostatic Pressure Test Specification (Static Water Pressure Holding)
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular product supplied in continuous coil form. As a critical component in industrial piping systems, coil tubes are widely deployed across chemical processing, food and beverage, pharmaceutical, and energy sectors. This specification document focuses on the hydrostatic pressure test (Hydrostatic Pressure Test / Water Pressure Test), specifically the static water pressure holding (Static Water Pressure Holding) procedure, which constitutes a mandatory quality assurance checkpoint prior to product shipment.
The hydrostatic pressure test is the most fundamental and universally recognized non-destructive testing (NDT) method for verifying the structural integrity, weld quality, and dimensional accuracy of stainless steel tubes. It ensures that every coil tube meets or exceeds the mechanical performance requirements stipulated by international standards before reaching the end user.
2. Material & Properties
Coil tubes produced by Wenzhou Jixing Metal Materials Co., Ltd are typically fabricated from austenitic stainless steel grades, including but not limited to:
- 304 / 304L (UNS S30400 / S30403) – General-purpose corrosion resistance
- 316 / 316L (UNS S31600 / S31603) – Enhanced resistance to chlorides and pitting
- 321 / 321H (UNS S32100 / S32109) – Stabilized for high-temperature service
- 310S (UNS S31008) – High-temperature oxidation resistance
Key material properties relevant to hydrostatic pressure performance include:
- Yield Strength (Rp0.2) – Minimum 205 MPa (Grade 304), 170 MPa (Grade 316L)
- Tensile Strength (Rm) – Minimum 515 MPa (Grade 304), 485 MPa (Grade 316L)
- Elongation (A50mm) – Minimum 40% (Grade 304), 35% (Grade 316L)
- Corrosion Resistance – Excellent resistance to atmospheric, aqueous, and mild chemical environments
3. Specifications – Hydrostatic Pressure Test Parameters
| Parameter | Specification / Requirement | Standard Reference |
|---|---|---|
| Test Medium | Clean, de-aerated water (Hydrostatic Water) | ASTM A999 / EN 10217 |
| Test Pressure | 1.5 × Design Pressure (1.5 times the maximum allowable working pressure) | ASME BPVC Section VIII / EN 10216 |
| Hold Time (Dwell Time) | ≥ 5 seconds (minimum static water pressure holding duration) | ISO 11114 / GB/T 14976 |
| Acceptance Criteria | No leakage, no visible deformation, no pressure drop detected during hold period | ASTM A999 / ISO 11114 |
| Test Coverage | 100% inspection – Every coil tube lot undergoes hydrostatic pressure testing | Internal Quality Assurance Protocol |
| Inspection Type | Mandatory pre-shipment inspection (Non-negotiable) | Factory Acceptance Test (FAT) |
| Equipment Accuracy | Pressure gauge accuracy ±1.0% of reading; calibrated within valid interval | ISO 17025 |
| Test Temperature | Ambient temperature (typically 15°C – 40°C) | ASTM A999 |
4. Manufacturing Process – Pressure Test Integration
The hydrostatic pressure test is integrated as a critical stage within the manufacturing workflow of Wenzhou Jixing Metal Materials Co., Ltd's coil tube production line. The process sequence is as follows:
- Hot Rolling / Cold Drawing – Production of seamless or welded stainless steel tubes from billet or strip stock
- Cold Drawing / Cold Pilgering – Dimensional refinement to achieve precise outer diameter (OD) and wall thickness tolerances
- Heat Treatment (Solution Annealing) – Restoration of austenitic microstructure and removal of residual stresses
- Pickling & Passivation – Removal of oxide scale and formation of protective chromium oxide layer
- Coiling – Winding of tubes into continuous coil form for efficient downstream processing
- Hydrostatic Pressure Testing (Static Water Pressure Holding) – Application of 1.5× design pressure with ≥5 second hold time; automated detection of leakage or deformation
- Final Inspection & Documentation – Recording of test results, generation of Mill Test Reports (MTR), and packaging for shipment
5. Applications
Coil tubes that have passed the hydrostatic pressure test are suitable for demanding applications requiring high reliability and leak-tight integrity:
- Chemical Processing – Piping systems for acid, alkali, and solvent transfer
- Food & Beverage Industry – Hygienic-grade fluid handling and CIP (Clean-in-Place) systems
- Pharmaceutical Manufacturing – GMP-compliant process piping and equipment
- Petrochemical & Oil/Gas – Downstream processing, refining, and distribution systems
- Heat Exchangers & Boilers – Tubular bundles requiring pressure containment
- Medical Devices – Instrumentation tubing and fluid delivery components
- Automotive & Aerospace – High-performance fluid lines and hydraulic systems
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system aligned with international standards. The hydrostatic pressure test program is supported by the following certifications and compliance frameworks:
- ISO 9001:2015 – Quality Management System certification
- ISO 17025 – Laboratory competence for testing and calibration
- EN 10204 3.1 Certificate – Third-party material test report for each shipment
- ASME / PED (Pressure Equipment Directive) – Compliance with pressure vessel and piping codes
- CE Marking – Conformity with European health, safety, and environmental protection standards
7. Unique Selling Points
"Safety and Reliability – Every Tube, Every Time."
- 100% Hydrostatic Testing Coverage – Unlike many manufacturers that perform sampling-based inspection, Wenzhou Jixing subjects every coil tube to full hydrostatic pressure testing, ensuring zero tolerance for defects
- 1.5× Design Pressure Protocol – Exceeds minimum code requirements by testing at 50% above the maximum allowable working pressure, providing an additional safety margin
- Automated Leak Detection – Advanced instrumentation enables real-time pressure monitoring and immediate detection of any leakage or structural failure
- Full Traceability – Each test result is digitally recorded and linked to the corresponding heat number and coil lot, enabling complete supply chain traceability
- Multi-Grade Capability – Testing infrastructure accommodates all major austenitic and duplex stainless steel grades, supporting diverse customer requirements
- Compliant with Global Standards – Test procedures align with ASTM, EN, ISO, ASME, and GB/T standards, facilitating acceptance across international markets
8. Conclusion
The hydrostatic pressure test (static water pressure holding) at 1.5× design pressure with a minimum 5-second hold time is not merely a regulatory requirement – it is a cornerstone of product safety philosophy at Wenzhou Jixing Metal Materials Co., Ltd. This mandatory inspection protocol guarantees that every stainless steel coil tube delivered to customers possesses verified structural integrity, dimensional accuracy, and leak-tight performance. For industrial applications where failure is not an option, this rigorous testing standard provides the confidence and assurance that end users demand.