Lastprüfung der Kranhakenverfahren

Crane hooks are the vital, often singular, connection point between the lifting apparatus and the load. Ensuring their structural integrity and safe working load (Swl) capacity is non-negotiable for preventing catastrophic failures. Load testing is a mandatory procedure designed to verify this integrity beyond any doubt. Here’s a detailed look at the standard load testing procedure for crane hooks:

Purpose

• 1. To verify the hook’s ability to safely lift its rated SWL and beyond, within defined safety margins.

• 2. To detect hidden flaws, Risse, deformations, or material weaknesses not visible during routine inspections.

• 3. To ensure compliance with regulatory standards (Wie OSHA, ASME B30.10, ISO 4309) and manufacturer specifications.

• 4. To provide documented proof of the hook’s fitness for service.

Types of Load Tests

• 1. Beweislasttest (Static Test): The most common type, applying a static load greater than the SWL but less than the ultimate strength.

• 2. Dynamic Load Test: Involves lifting, lowering, and sometimes swinging a test load to simulate operational stresses. Often performed on the entire crane system, but hook performance is critical.

Standard Load Testing Procedure for Hooks (Beweislasttest)

• 1. Pre-Test Preparations:

  • Review Documentation: Examine the hook’s identification (Swl, serial number, Hersteller), inspection history, and previous test certificates.
  • Visual Inspection: Conduct a thorough visual inspection before applying load. Look for:
    • Risse (especially at the throat, shank, or tip).
    • Excessive wear, Kerben, or gouges.
    • Verformung (bending, verdrehen).
    • Corrosion or pitting.
    • Worn or damaged latch (if equipped).
    • Legible SWL marking.
  • Clean the Hook: Remove dirt, grease, or loose scale that could mask defects or interfere with measurement.
  • Measure Critical Dimensions: Record key dimensions (Z.B., throat opening, Kranhaken tip wear) using calipers or gauges for post-test comparison.
  • Select Test Weight: Calculate the required proof load. Common standards require:
    • Initial Test (New Hook): Typically 200% of SWL.
    • Periodic Re-Test (In-Service Hook): Typically 125% of SWL (Always confirm based on local regulations, standards like ASME B30.10, and manufacturer’s instructions). Ensure weights are certified and calibrated.
  • Setup: Rig the hook safely using appropriate slings/shackles rated for the test load. Ensure the hook is positioned correctly (load applied along the hook centerline). Use a dedicated test frame or the crane itself (if procedure allows) with the boom in its least stable configuration.
  • Safety Zone: Establish a clearly marked exclusion zone. All personnel must stand clear except essential test operators.
  • PPE: All involved personnel must wear appropriate Personal Protective Equipment (hard hat, safety glasses, steel-toe boots, high-visibility vest).
  • Instrumentation (Optional but Recommended): Use strain gauges or calibrated load cells to precisely measure the applied load. Use dial indicators to measure any permanent deformation.

• 2. Applying the Load:

  • Lift Slowly: Raise the test load smoothly and gradually to the target proof load (Z.B., 125% Swl). Avoid jerking.
  • Hold Duration: Once the full proof load is reached, hold it statically for a minimum specified time (commonly 5 Zu 10 minutes, as per standard/manufacturer). Maintain precise control.
  • Monitor Continuously: During the hold period, carefully observe the hook and its rigging for any signs of:
    • Audible noises (cracking, popping).
    • Visible deformation (bending, stretching).
    • Movement or slippage in rigging.
    • Cracking (critical!).

• 3. Post-Hold Actions:

  • Lower Slowly: Gradually and smoothly lower the test load to the ground.
  • Detailed Visual Inspection: Conduct an even more rigorous visual inspection immediately after load removal. Pay particular attention to areas under highest stress (throat, shank, tip, latch mechanism). Look for any new cracks, opening of existing cracks, or permanent deformation. Magnifying glasses or dye-penetrant testing might be used for critical assessment.
  • Dimensional Check: Re-measure the critical dimensions recorded before the test. Compare results. Any permanent deformation exceeding manufacturer or standard tolerances (often specified as a percentage of original dimension) is cause for rejection.
  • Functional Check (Verriegeln): Wenn ausgestattet, ensure the latch operates freely and correctly engages the hook tip.

• 4. Evaluation & Dokumentation:

  • Pass Criteria: The hook passes if:

    • No cracks are detected during pre, during, or post-test inspections.

    • No permanent deformation exceeding allowable tolerances is measured.

    • The latch (Wenn vorhanden) functions correctly.

  • Fail Criteria: The hook fails if:

    • Any crack is detected.

    • Permanent deformation exceeds specified limits.

    • The latch is damaged or malfunctions.

    • Any other defect compromising safety is found.

  • Tagging: If passed, attach a durable, weather-resistant test tag securely to the hook. It must clearly state:

    • Swl

    • Test Load Applied (Z.B., “Tested to 125% SWL”)

    • Test Date

    • Next Test Due Date (based on regulatory/company schedule)

    • Unique Identification (Serial Number)

    • Testing Authority/Company

  • Certificate of Test: Issue a formal test certificate detailing all aspects of the test (hook ID, Swl, test load, date, inspector, results, standards followed). This is a critical legal and safety document.

Important Considerations & Warnings

• 1. Qualified Personnel: Load testing must ONLY be performed by competent, trained, and authorized personnel familiar with the standards, procedures, and risks.
• 2. Never Exceed Limits: Applying loads significantly beyond the specified proof test (especially approaching ultimate strength) can damage sound hooks and is dangerous.
• 3. Environment: Avoid testing in high winds, poor visibility, or adverse weather conditions that compromise safety.
• 4. Rigging Integrity: The test rigging (slings, Fesseln) must be certified for the test load and inspected before use.
• 5. Rejection is Safety: A failed hook must be immediately removed from service. Repair of crane hooks is generally prohibited; replacement is the only safe option.
• 6. Frequency: Follow manufacturer recommendations, regulatory requirements (Z.B., annual), and company policy based on usage severity. More frequent testing may be needed for harsh environments or heavy use.

Load testing crane hooks is not merely a regulatory box-ticking exercise; it is a fundamental pillar of lifting safety. A meticulously executed load test procedure, performed by qualified individuals at the required intervals, provides the highest level of assurance that this critical component will perform reliably under stress. Consistent adherence to this procedure protects personnel, safeguards equipment, prevents costly downtime and damage, and ultimately saves lives. Never compromise on the integrity of the hook or the rigor of its testing.