Stainless Steel Coil Tube — Arrival Inspection Protocol (Acceptance Criteria Specification)
1. Product Overview
The Stainless Steel Coil Tube (also referred to as Coiltube or Coiled Tubing) is a continuous-length, cold-worked stainless steel pipe supplied in the form of a coil for downstream processing, fabrication, and installation. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this product is engineered for high-precision industrial applications where dimensional accuracy, mechanical integrity, and corrosion resistance are critical performance parameters.
This specification document defines the Arrival Inspection Protocol (到货检验协议) — a pre-agreed contractual framework governing the acceptance criteria upon delivery. The protocol establishes the Positive Material Identification (PMI) re-inspection ratio, Non-Destructive Testing (NDT) sampling plan, and Non-Conformance Handling Process (不合格处理流程). The primary objective of this protocol is to eliminate post-delivery disputes by establishing mutually agreed-upon inspection standards, tolerances, and remediation procedures prior to shipment.
Core Principle: All inspection parameters, acceptance thresholds, and dispute resolution mechanisms are pre-defined in the contract to prevent ambiguity and ensure traceability throughout the supply chain.
2. Material & Properties
2.1 Material Grades
Coil tubes are typically manufactured from austenitic and duplex stainless steel grades, selected based on the end-use application requirements:
- ASTM A312 / A312M — Cold-worked austenitic stainless steel seamless tubes
- ASTM A213 — Heat-exchanger and heat-transfer tubing
- EN 10216-5 — Seamless austenitic stainless steel tubes for pressure purposes
- GB/T 12771 — Chinese national standard for welded stainless steel tubes
2.2 Chemical Composition Requirements
Chemical composition is verified per ASTM E1412 (Optical Emission Spectrometric Analysis) and ASTM E135 (X-Ray Fluorescence Spectrometric Analysis). Key elemental limits include:
- Carbon (C): ≤ 0.08% (standard) / ≤ 0.03% (L-grade low carbon)
- Chromium (Cr): 17.0% – 19.0% (304) / 18.0% – 20.0% (316)
- Nickel (Ni): 8.0% – 10.5% (304) / 10.0% – 14.0% (316)
- Molybdenum (Mo): 2.0% – 3.0% (316 series)
- Sulfur (S): ≤ 0.030% (maximum)
2.3 Mechanical Properties
- Tensile Strength: ≥ 515 MPa (75 ksi) — 304 grade
- Yield Strength: ≥ 205 MPa (29.7 ksi) — 304 grade
- Elongation: ≥ 40% (minimum)
- Hardness: 85 – 230 HV (depending on cold-work level)
3. Specifications — Arrival Inspection Protocol
3.1 PMI Re-Inspection Ratio (Positive Material Identification)
PMI re-inspection is a mandatory contractual requirement to verify that the delivered material grade matches the specified order. The protocol defines the following sampling framework:
| Parameter | Requirement | Standard Reference |
|---|---|---|
| PMI Testing Method | Handheld X-Ray Fluorescence (XRF) Spectrometry | ASTM E135 / ASTM E1412 |
| Sampling Ratio — Standard Orders | 1 coil per lot (minimum 1 unit per heat number) | Contract Annex A |
| Sampling Ratio — Critical Applications | 10% of coils per lot (minimum 3 units) | Contract Annex A |
| Sampling Ratio — First Article / New Grade | 100% PMI verification on first 3 coils | Contract Annex A |
| Acceptance Criteria | All measured values within ±0.5% of specified grade composition | ASTM E135 |
| Testing Location | Outer surface of coil, 500 mm from each end | Manufacturer SOP |
| Documentation | Digital PMI report with operator certification attached to Mill Test Report (MTR) | ISO 9001:2015 Clause 8.7 |
3.2 NDT Sampling Plan (Non-Destructive Testing)
Non-Destructive Testing is applied to verify internal and surface integrity without compromising product usability. The following NDT methods and sampling protocols are pre-agreed:
| NDT Method | Application | Sampling Frequency | Acceptance Criteria | Standard |
|---|---|---|---|---|
| Eddy Current Testing (ECT) | Internal defect detection (inclusions, laminations, cracks) | 100% inline during production; 5% post-production re-verification | No defects exceeding 25% of wall thickness | ASTM E309 / ASTM E709 |
| Magnetic Particle Inspection (MPI) | Surface and near-surface defect detection | 10% of coils per lot (minimum 2 units) | No linear indications > 6 mm length | ASTM E1444 |
| Visual Inspection (VT) | Surface quality, dimensional accuracy, packaging integrity | 100% of coils at point of dispatch | No visible defects per ASTM A312 Section 10 | ASTM A312 / ISO 17638 |
| Hydrostatic Testing (HT) | Pressure integrity verification | 100% inline; sampling re-test 3% per lot | No leakage at 1.5× design pressure for 30 seconds | ASTM A312 / EN 10216-5 |
| Ultrasonic Testing (UT) | Wall thickness measurement and internal flaw detection | 5% of coils per lot (minimum 2 units) | No internal reflectors exceeding 15% DAC level | ASTM E1316 |
3.3 Non-Conformance Handling Process
The Non-Conformance Handling Process is a structured, pre-agreed escalation and remediation framework designed to resolve quality discrepancies without disrupting supply continuity. The process follows the following sequential steps:
- Step 1 — Identification & Quarantine: Upon detection of a non-conforming coil, the receiving party immediately isolates the affected material and notifies the supplier within 24 hours via written communication (email or formal Non-Conformance Report).
- Step 2 — Verification & Re-Testing: Both parties agree on an independent third-party laboratory for re-verification testing. Results are binding if the laboratory holds ISO/IEC 17025 accreditation.
- Step 3 — Classification: Non-conformances are classified as:
- Class A (Critical): Material grade mismatch, mechanical properties below minimum, or safety-critical defect — full lot rejection.
- Class B (Major): Dimensional deviation exceeding tolerance by >50%, surface defect requiring rework — affected coils rejected, remainder of lot subject to 100% inspection.
- Class C (Minor): Cosmetic imperfections, minor dimensional variance within 50% of tolerance — acceptable with documented concession or price adjustment.
- Step 4 — Remediation: Options include return for replacement, on-site rework at supplier's cost, price concession, or mutual agreement on use-as-is with documented risk acceptance.
- Step 5 — Root Cause Analysis & CAPA: Supplier submits a Corrective and Preventive Action (CAPA) report within 10 working days, including root cause analysis, containment actions, and preventive measures.
- Step 6 — Closure: Non-conformance is formally closed only upon written confirmation from both parties that remediation is satisfactory.
3.4 Inspection Timeline & Responsibilities
| Activity | Responsible Party | Timeline | Deliverable |
|---|---|---|---|
| Visual & dimensional inspection | Buyer / Third-party inspector | Within 3 working days of delivery | Inspection Report |
| PMI verification | Buyer (or designated lab) | Within 5 working days of delivery | PMI Certificate |
| NDT sampling | Buyer / Third-party NDT agency | Within 7 working days of delivery | NDT Test Report |
| Non-conformance notification | Buyer | Within 24 hours of detection | Non-Conformance Report (NCR) |
| Supplier response & remediation plan | Supplier | Within 48 hours of NCR receipt | Remediation Proposal |
| CAPA report submission | Supplier | Within 10 working days | CAPA Report |
4. Manufacturing Process
The stainless steel coil tube production process at Wenzhou Jixing Metal Materials Co., Ltd follows a controlled sequence ensuring dimensional precision and metallurgical integrity:
- Hot Rolling: Billet material is heated to 1200°C–1300°C and pierced to form hollow tubes.
- Intermediate Annealing: Tubes are annealed to relieve residual stresses and restore ductility for cold working.
- Acid Pickling & Descaling: Surface scale is removed via controlled acid bath treatment (HNO₃/HF blend).
- Cold Drawing / Cold Reduction: Tubes pass through multiple die stations to achieve final dimensions with tight tolerances (±0.05 mm).
- Final Annealing: Solution annealing at 1050°C–1150°C followed by rapid quenching to achieve austenitic microstructure.
- Coiling: Finished tubes are wound into coils with controlled tension to prevent deformation.
- Final Inspection: 100% inline ECT, hydrostatic testing, and dimensional verification prior to coiling.
5. Applications
- Automotive Industry: Fuel system lines, brake lines, exhaust components, fuel cell hydrogen tubing
- Medical Devices: Endoscopic instruments, surgical tubing, pharmaceutical processing lines
- Food & Beverage Processing: Sanitary piping, CIP (Clean-in-Place) systems, brewing equipment
- Petrochemical & Energy: Heat exchanger tubes, refinery piping, offshore platform components
- Aerospace: Hydraulic lines, pneumatic tubing, fuel delivery systems
- Consumer Appliances: Washing machine water lines, dishwasher spray arms, refrigerator tubing
- Construction: Architectural railing systems, structural bracing, decorative trim
6. Quality Certifications
The arrival inspection protocol is supported by the following quality management certifications and standards compliance:
- ISO 9001:2015 — Quality Management System certification covering all production and inspection processes
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
- ISO/IEC 17025 — Laboratory accreditation for PMI and NDT testing facilities
- EN 10204 Type 3.1 — Material Test Certificate issued by authorized manufacturing representative
- EN 10204 Type 3.2 — Material Inspection Certificate issued by independent third-party inspector (available upon request)
- ASTM A312 / A213 Compliance — Full conformance to American Society for Testing and Materials standards
- CE Marking — European Conformity for pressure equipment applications
- ASME Certificate — For pressure vessel and piping applications per ASME Section IX
7. Unique Selling Points — Arrival Inspection Protocol
"Pre-agreed acceptance criteria eliminate post-delivery disputes."
- Contractual Certainty: All inspection parameters, sampling ratios, and acceptance thresholds are defined prior to order placement, providing full transparency and predictability for both buyer and supplier.
- Structured Escalation Pathway: The Non-Conformance Handling Process provides a clear, time-bound resolution framework that prevents prolonged disputes and supply interruptions.
- Third-Party Verification Option: Independent ISO/IEC 17025-accredited laboratory testing is pre-authorized, ensuring impartial dispute resolution.
- Traceability: Every coil is traceable to its heat number, mill test report, PMI certificate, and NDT results — creating a complete quality documentation package.
- Scalable Sampling: The protocol accommodates varying risk levels — from standard orders (1 coil per lot) to critical applications (10% sampling) — optimizing inspection cost without compromising quality assurance.
- Regulatory Alignment: The protocol aligns with international standards (ASTM, EN, ISO), ensuring acceptance across global markets and regulatory jurisdictions.
- Continuous Improvement: Mandatory CAPA reporting after any non-conformance ensures systematic quality improvement over the supply relationship lifecycle.
8. Conclusion
The Arrival Inspection Protocol represents Wenzhou Jixing Metal Materials Co., Ltd