Complete Test Specification For Anti-theft Self-locking Nut Anti-loosening, Anti-demolition & Anti-corrosion Performance, Fully Cite Valid Current GB/T & ISO Standards

Complete Test Specification For Anti-theft Self-locking Nut Anti-loosening, Anti-demolition & Anti-corrosion Performance, Fully Cite Valid Current GB/T & ISO Standards

Anti-theft self-locking nuts used in power transmission tower, rail transit, municipal guardrail and PV bracket have clear mandatory national standard requirements for factory inspection and project site acceptance. All test methods and judgment thresholds in this article adopt valid current standards issued by National Fastener Standardization Technical Committee, without self-defined fictional indicators. List of core cited standards: GB/T 3098.2 Mechanical properties of fasteners – Nuts, GB/T 10125-2021 Artificial atmosphere corrosion test – Salt spray test, GB/T 3098.17-2000 Mechanical properties of fasteners – Pre-load test for hydrogen embrittlement inspection, ISO 16130 Fasteners – Vibration relaxation test for all-metal lock nuts, covering full-dimensional test demand of three mainstream anti-theft nut types.

1. Three Types Of Anti-theft Nut Graded Performance Judgment Table (General Acceptance Threshold For Engineering Bidding, Allowable Range Specified By National Standard)

2. Standardized Operation Procedure Of Four Core Mandatory National Standard Tests

1. Vibration Anti-loosening Fatigue Test (ISO 16130): Match nut with corresponding grade bolt, apply standard national standard preload, alternating vibration 10-50Hz on vibration table for continuous 500,000 cycles, retest residual preload after test, judge anti-loosening performance unqualified if lower than threshold in table, 100% batch sampling required for rail transit and wind power projects. 2. Neutral Salt Spray Corrosion Test (GB/T 10125-2021 NSS): 5% sodium chloride solution, pH 6.5-7.2, constant temperature 35℃ continuous spray, judge anti-corrosion unqualified if red rust appears before coating matching duration in table; coastal PV and island power grid projects must add alternating salt spray test per IEC61701. 3. Hydrogen Embrittlement Pre-load Screening Test (GB/T 3098.17): Only for grade 8.8 and above high-strength carbon steel anti-theft nuts, apply 1.2 times yield load and stand for 48 hours static placement, qualified if no crack or brittle fracture on thread after disassembly; mandatory test for electroplated & hot-dip galvanized high-strength nuts before delivery to avoid safety hazard of delayed fracture on construction site. 4. Torsion Breaking Load Test (GB/T 3098.2): Apply load uniformly via torque tester, record maximum torque when nut thread tear or spur tooth inverted structure fails, shall not be lower than minimum threshold in table, whole batch rejected if sampling unqualified for municipal and power grid project site entry.

3. Objective Judgment Basis Of Anti-demolition Grade (No Self-defined Grade, Based On General Security Engineering Specification)

Grade 1 Civil Anti-demolition: Pin Torx & triangular groove matched with ordinary lock nut, compatible with standard socket for complete disassembly, only allowed for indoor home appliance and small household charging pile, no mandatory long-term salt spray or million-cycle vibration requirement. Grade 2 Industrial Anti-demolition: Spur tooth & ordinary inverted structure, special special-shaped socket required, cannot be disassembled by ordinary household wrench, statutory grade adopted by onshore power grid and rail transit projects. Grade 3 Security Anti-demolition: Composite inner & outer special inverted structure, no general matching tool, customized special fixture needed for disassembly, mandatory for road security, monitoring pole and toll equipment.

4. Batch Delivery Sampling Rule (GB/T 2828.1 Count Sampling, Industry General)

1. Ordinary civil batch: total quantity ≤50,000pcs, implement AQL1.0 sampling, extract 80pcs per batch for basic appearance & dimension test. 2. Industrial power grid & wind power batch: regardless of batch quantity, extract 125pcs per batch, must complete three destructive tests including vibration fatigue, salt spray and hydrogen embrittlement. 3. Key municipal security engineering batch: extract 200pcs per batch for full-item test, rework, re-coat and re-heat treat whole batch if any national standard index unqualified, forbid defective goods screening and delivery out of factory.