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I. Pre-inspection Preparation (First Step of Inspection)

1. Sample Information Verification

1. Verify batch information: Confirm material model, nominal clamping inner diameter, material grade (65Mn / 304 stainless steel), batch number, production date and surface treatment process (galvanized / blackened / passivated), which shall be consistent with design drawings and incoming quality inspection sheets.

2. Sampling Rules: Grade-II sampling inspection specified by GB2828 for mass production batches, with 100% full visual inspection for appearance items. 15 pieces shall be sampled from each batch for mechanical property, salt spray and tightness tests; double sampling quantity for products applied in special automotive working conditions.

3. Environmental Requirements: The temperature of the inspection room shall be 20±5℃, and the relative humidity shall be 45%-65%. All measuring tools must be constant-temperature calibrated in advance and used within valid calibration period.

2. Equipped Testing Tools

II. Step 1: Full Visual Inspection (100% Mandatory Basic Screening)

1. Overall Shape: No distortion, warping or elliptical deformation on the whole clamp; symmetrical opening angle and ear opening & closing structure without unilateral offset.

2. Edge Burrs: The height of burrs at cutting and bending positions shall not exceed 0.02mm; no sharp flash to avoid scratching matched rubber hoses.

3. Surface Defects: Free of cracks, indentations, rust spots, oxide stains, peeling, missing spot welding and cold welding. No intergranular cracks on stainless steel spring clamps.

4. Coating Appearance: Uniform galvanized layer without color difference, missing plating or sagging; blackened coating features firm adhesion without peeling. Engraved product model and batch marks are clear and intact.

5. Elastic Structure: No edge chipping or rebound jamming on opening ears; no dislocation or jamming at hinge connection positions.

III. Step 2: Dimensional Accuracy Inspection

1. Core Inner Diameter: Measure free-state inner diameter, maximum expanded inner diameter and assembled closed inner diameter. The tolerance shall comply with drawing requirement ±0.05mm to match standard pipe diameters.

2. Body Structural Parameters: Steel strip thickness, strip width, ear height, opening gap, bending fillet radius and center distance shall meet drawing tolerance standards.

3. Geometric Tolerance: Qualified circularity and end face parallelism, no eccentricity; complete fitting contact surface with outer hose wall after assembly.

4. Auxiliary Verification: Qualified opening stroke and expansion allowance, no assembly interference during installation.

IV. Step 3: Special Surface Treatment Inspection

1. Coating Thickness Test: Tested by magnetic thickness gauge; galvanized coating ≥8μm, passivation coating ≥3μm to meet anti-corrosion requirements.

2. Adhesion Test: 1mm grid cross-cut test; no coating peeling after adhesive tape tearing, which means qualified adhesion performance.

3. Salt Spray Corrosion Resistance Test: Neutral salt spray test. Carbon steel galvanized clamps show no red rust within 48h; 304 stainless steel clamps show no corrosion cracks within 1000h.

4. Passivation Integrity Test: No free acid residue and surface discoloration for passivated finished clamps.

V. Step 4: Physical & Mechanical Property Batch Inspection

1. Hardness Test: 65Mn spring steel: HV420-480; 304 stainless steel: HV380-450. Unqualified hardness will cause fracture risk or insufficient elastic resilience.

2. Clamping Force Test: Rated clamping force tested by tensile testing machine shall comply with original standard; insufficient clamping force causes loose connection, while excessive force will crush rubber hoses.

3. Resilience Performance: No permanent plastic deformation after 50 times reciprocating opening and closing test; inner diameter rebound deviation ≤2%.

4. Tensile Fracture Performance: The clamp body and welding points have qualified tensile strength without cracking or fracture under rated stress.

5. Stress Corrosion Test: Special working condition clamps shall pass the stress corrosion test without brittle fracture and stress cracks.

VI. Step 5: Simulated Working Condition Assembly Performance Test

1. Assembly Adaptability: Smooth manual or tool assembly on standard pipe fittings, tight closing without fitting gap.

2. Pressure Holding Tightness Test: Assemble clamps on standard pipe assemblies, keep rated hydraulic or pneumatic pressure for 5min at room temperature, no leakage and pressure relief at connecting ports. High-low temperature alternating tightness test is required for customized working-condition products.

3. Fatigue Life Test: Complete vibration and opening-closing cycle test. Ordinary clamps: no fracture or clamping attenuation after over 1000 cycles; automotive dedicated clamps: qualified after over 5000 cycles.

4. Torque Inspection: Double-ear clamps shall reach standard locking torque, no slipping or rebound loosening after locking.

VII. Nonconformity Classification, Disposal & Re-inspection Rules

1. Defect Classification

• Critical Defect: Cracking, fracture, pressure holding leakage and unqualified hardness → whole batch rejection.

• Major Defect: Out-of-tolerance dimension, insufficient clamping force, coating peeling → screened and reworked for secondary inspection.

• Minor Defect: Slight surface scratch, unclear marking → conditional acceptance for delivery.

2. Disposal Procedure

1. Qualified Products: Paste qualified label, file inspection data and arrange warehouse storage.

2. Unqualified Products: Isolate with red warning labels, classified into reworkable, scrap and batch return goods.

3. Failed Batch Performance Test: Expand sampling quantity for re-inspection; reject the whole batch if re-inspection still fails.

VIII. Data Filing & Batch Traceability Management

1. Record full inspection data including appearance, dimension, hardness, clamping force, salt spray and tightness test results, keep original inspection records.

2. Issue official finished product inspection certificate bound with batch number, realizing full-process traceability from raw material processing to finished inspection.

3. Regularly review measuring tool data to optimize stamping, heat treatment and electroplating inspection standards.

IX. General Inspection Notes

1. Do not forcibly expand clamps during inspection, to avoid artificial elastic fatigue and permanent deformation affecting test accuracy.

2. Heat-treated clamps must be cooled to room temperature before hardness and resilience inspection.

3. Classify clamps of different materials for independent inspection to avoid batch mixing.

4. Custom non-standard clamps shall follow customer drawing parameters instead of general national standards.